Thesis Defense Presentation ONE-STEP PROCESS FOR SOLID OXIDE FUEL CELL FABRIC...chrisrobschu
Solid oxide fuel cells (SOFCs) are electrochemical devices that convert the chemical energy of a fuel to electrical energy. They offer clean, efficient, and reliable power and they can be operated using a variety of fuels. There are two major obstacles for commercializing the SOFC technology: reducing processing cost and increasing operating lifetime. The cost reduction necessary for commercialization of SOFC technology will not be met by optimization alone. Mass production techniques must be developed for SOFCs to be competitive with current power generating devices. The current cost goal of $400 / kW can only be met by improved processing techniques. Hot pressing as was investigated at Boston University as a novel processing technique to fabricate the planar SOFC in a single step. By removing multiple batch processing steps and simplifying the manufacturing process, considerable cost reduction can be achieved over current manufacturing processes. Additionally, the flexibility of hot pressing can improve interfacial contact and functionally grade interfaces to reduce polarization losses. Finally, by optimizing the process, the processing time and cost can be greatly reduced.
Fundamental knowledge related to ceramic processing, sintering, and hot pressing to successfully hot press a single operational SOFC in one step has been developed. Ceramic powder processing for each of the components of an SOFC has been tailored towards this goal. Processing parameters for the electrolyte and cathode were investigated and optimized to attain convergence. Several anode fabrication techniques were investigated and a novel anode structure was developed and refined. Based on these results single SOFC cells were fabricated in one step.
Thesis defense schumacher_Dec 2002
This standard defines methods for calculating the early life failure rate of a product, using accelerated
testing, whose failure rate is constant or decreasing over time. For technologies where there is adequate
field failure data, alternative methods may be used to establish the early life failure rate.
The purpose of this standard is to define a procedure for performing measurement and calculation of early
life failure rates. Projections can be used to compare reliability performance with objectives, provide line
feedback, support service cost estimates, and set product test and screen strategies to ensure that the
Early life Failure Rate meets customers' requirements.
Nonequilibrium Excess Carriers in Semiconductorstedoado
The document discusses nonequilibrium excess carriers in semiconductors. It describes carrier generation and recombination processes, including direct band-to-band generation and recombination. Excess carrier generation occurs when high-energy photons excite electrons into the conduction band, generating electron-hole pairs. The document also discusses the Shockley-Read-Hall theory of recombination at trap energy levels within the bandgap, and the rates of electron and hole capture and emission processes. Under low-level injection and intrinsic doping assumptions, the recombination rate of excess carriers depends on the material parameters.
The document discusses semiconductors and their properties. It explains that semiconductors have resistivity between conductors and insulators. Their energy bands consist of a conduction band, valence band, and a small forbidden gap of around 0.7-1.1 eV. This allows electrons to move between bands with small amounts of energy. The document also describes intrinsic and extrinsic semiconductors, and how doping with elements from group 3 or 5 creates an excess or deficiency of electrons, resulting in n-type or p-type materials respectively.
This document discusses how MOSFET power losses affect power supply efficiency. It provides equations to calculate the various power loss components in a buck converter, including conduction losses, switching losses, and static losses. MOSFET switching losses are affected by load current and switching frequency. Both the high-side and low-side MOSFETs contribute conduction, switching and gate driver losses. Optimizing MOSFET selection involves tradeoffs between conduction resistance, gate charge and switching speed. Understanding these loss factors enables improved power supply efficiency design.
The document discusses band theory of solids and key concepts like the Fermi level, band gaps, and conduction in different materials. It explains that the Fermi level describes the highest occupied electron energy level at absolute zero. Materials are classified based on their band gap as conductors, semiconductors, or insulators. Conductors have a small or overlapping band gap allowing conduction, while insulators have a large gap preventing conduction except at very high temperatures. Semiconductors have an intermediate gap size and can conduct at higher temperatures when electrons are thermally excited across the gap.
This document is a presentation by Dr. Lynn Fuller on Gallium Arsenide (GaAs) devices, technologies, and integrated circuits. It provides an overview and comparison of silicon and GaAs, describes GaAs crystal growth techniques like molecular beam epitaxy (MBE), and discusses GaAs field effect transistors (MESFETs) and the fabrication process for GaAs integrated circuits. The presentation contains numerous diagrams and equations to illustrate concepts in GaAs device physics and fabrication processes.
In this work, I am showing a faithful atomistic process of estimating the oxygen migration energetics within BSCF, oxygen migration energy exhibit a strong dependence on different local atomic structures of this doped perovskites. In addition, DFT calculations exhibit the reason of cubic phase stability of this doped perovskite in variable oxygen concentration.
Thesis Defense Presentation ONE-STEP PROCESS FOR SOLID OXIDE FUEL CELL FABRIC...chrisrobschu
Solid oxide fuel cells (SOFCs) are electrochemical devices that convert the chemical energy of a fuel to electrical energy. They offer clean, efficient, and reliable power and they can be operated using a variety of fuels. There are two major obstacles for commercializing the SOFC technology: reducing processing cost and increasing operating lifetime. The cost reduction necessary for commercialization of SOFC technology will not be met by optimization alone. Mass production techniques must be developed for SOFCs to be competitive with current power generating devices. The current cost goal of $400 / kW can only be met by improved processing techniques. Hot pressing as was investigated at Boston University as a novel processing technique to fabricate the planar SOFC in a single step. By removing multiple batch processing steps and simplifying the manufacturing process, considerable cost reduction can be achieved over current manufacturing processes. Additionally, the flexibility of hot pressing can improve interfacial contact and functionally grade interfaces to reduce polarization losses. Finally, by optimizing the process, the processing time and cost can be greatly reduced.
Fundamental knowledge related to ceramic processing, sintering, and hot pressing to successfully hot press a single operational SOFC in one step has been developed. Ceramic powder processing for each of the components of an SOFC has been tailored towards this goal. Processing parameters for the electrolyte and cathode were investigated and optimized to attain convergence. Several anode fabrication techniques were investigated and a novel anode structure was developed and refined. Based on these results single SOFC cells were fabricated in one step.
Thesis defense schumacher_Dec 2002
This standard defines methods for calculating the early life failure rate of a product, using accelerated
testing, whose failure rate is constant or decreasing over time. For technologies where there is adequate
field failure data, alternative methods may be used to establish the early life failure rate.
The purpose of this standard is to define a procedure for performing measurement and calculation of early
life failure rates. Projections can be used to compare reliability performance with objectives, provide line
feedback, support service cost estimates, and set product test and screen strategies to ensure that the
Early life Failure Rate meets customers' requirements.
Nonequilibrium Excess Carriers in Semiconductorstedoado
The document discusses nonequilibrium excess carriers in semiconductors. It describes carrier generation and recombination processes, including direct band-to-band generation and recombination. Excess carrier generation occurs when high-energy photons excite electrons into the conduction band, generating electron-hole pairs. The document also discusses the Shockley-Read-Hall theory of recombination at trap energy levels within the bandgap, and the rates of electron and hole capture and emission processes. Under low-level injection and intrinsic doping assumptions, the recombination rate of excess carriers depends on the material parameters.
The document discusses semiconductors and their properties. It explains that semiconductors have resistivity between conductors and insulators. Their energy bands consist of a conduction band, valence band, and a small forbidden gap of around 0.7-1.1 eV. This allows electrons to move between bands with small amounts of energy. The document also describes intrinsic and extrinsic semiconductors, and how doping with elements from group 3 or 5 creates an excess or deficiency of electrons, resulting in n-type or p-type materials respectively.
This document discusses how MOSFET power losses affect power supply efficiency. It provides equations to calculate the various power loss components in a buck converter, including conduction losses, switching losses, and static losses. MOSFET switching losses are affected by load current and switching frequency. Both the high-side and low-side MOSFETs contribute conduction, switching and gate driver losses. Optimizing MOSFET selection involves tradeoffs between conduction resistance, gate charge and switching speed. Understanding these loss factors enables improved power supply efficiency design.
The document discusses band theory of solids and key concepts like the Fermi level, band gaps, and conduction in different materials. It explains that the Fermi level describes the highest occupied electron energy level at absolute zero. Materials are classified based on their band gap as conductors, semiconductors, or insulators. Conductors have a small or overlapping band gap allowing conduction, while insulators have a large gap preventing conduction except at very high temperatures. Semiconductors have an intermediate gap size and can conduct at higher temperatures when electrons are thermally excited across the gap.
This document is a presentation by Dr. Lynn Fuller on Gallium Arsenide (GaAs) devices, technologies, and integrated circuits. It provides an overview and comparison of silicon and GaAs, describes GaAs crystal growth techniques like molecular beam epitaxy (MBE), and discusses GaAs field effect transistors (MESFETs) and the fabrication process for GaAs integrated circuits. The presentation contains numerous diagrams and equations to illustrate concepts in GaAs device physics and fabrication processes.
In this work, I am showing a faithful atomistic process of estimating the oxygen migration energetics within BSCF, oxygen migration energy exhibit a strong dependence on different local atomic structures of this doped perovskites. In addition, DFT calculations exhibit the reason of cubic phase stability of this doped perovskite in variable oxygen concentration.
Dr. K. Ramya gave a lecture on superconductivity. The BCS theory proposed by Bardeen, Cooper and Schrieffer explains electron-phonon interaction in superconductors. In normal conductors, electrons scatter off vibrating atoms, increasing resistance. In superconductors, electron-phonon interaction decreases scattering, lowering energy. Electrons form Cooper pairs with equal and opposite momenta. Below a critical temperature, interaction between Cooper pairs and the positive ion core vanishes, resulting in zero resistivity and superconductivity. Applications of superconductivity include more efficient electrical generators, transformers, transmission lines, magnetic levitation, fast electrical switching, computer logic and storage, SQUIDs for magnetometry, and
Solid oxide fuel cells (SOFCs) use solid ceramic electrolytes to transport oxygen ions between the cathode and anode. They can operate on hydrogen or natural gas fuels from 700-1000°C. Perovskite materials are commonly used as electrodes or electrolytes due to their mixed ionic and electronic conductivity. SOFCs offer clean electricity generation but challenges remain in reducing costs and operating temperatures before widespread commercialization. Research is ongoing to develop new materials with improved performance at lower temperatures.
Ferroelectricity refers to materials that exhibit permanent electric polarization even in the absence of an external electric field. Materials that display this behavior are known as ferroelectric materials. Examples include lead titanate and lead zirconate titanate. Ferroelectric materials have applications in devices such as thermistors, oscillators, memory, and capacitors due to their large dielectric constants and ability to remain polarized in the absence of a field. Pyroelectricity is the ability of a material to generate an electric signal when subjected to thermal changes, and leads to applications in infrared sensors and thermometers. Ferroelectric hysteresis curves plot the polarization versus applied electric field and exhibit hysteresis behavior.
This document discusses the density of states (DoS) for bulk semiconductors. It begins by defining DoS as the number of available energy states per unit energy interval per unit dimension in real space. It then derives the DoS for bulk semiconductors using the Bloch theorem and shows that the DoS is proportional to the square root of energy. Finally, it defines the effective DoS, which accounts for occupancy based on the Fermi-Dirac distribution.
Two port network parameters, Z, Y, ABCD, h and g parameters, Characteristic impedance,
Image transfer constant, image and iterative impedance, network function, driving point and
transfer functions – using transformed (S) variables, Poles and Zeros.
The document summarizes a master's thesis defense on high pressure steam reactivation of calcium oxide (CaO) sorbents for carbon dioxide capture using calcium looping process. It discusses:
1) The introduction, experimental methodology, results and discussions, conclusions, and future work sections of the thesis.
2) Current CO2 levels and emissions from electricity production in the US, highlighting the need for carbon capture from coal and natural gas power plants.
3) Existing carbon capture technologies like amine scrubbing and their limitations.
4) The calcium looping process for post-combustion CO2 capture and limitations in maintaining sorbent reactivity over multiple cycles.
5) Reactivation of
The document summarizes key concepts from a lecture on combinatorics, probability, and multiplicity as they relate to statistical mechanics. It discusses two model systems - a two-state paramagnet and the Einstein solid. For the paramagnet, it defines the energy levels and multiplicity of macrostates. The multiplicity represents the number of configurations or arrangements of particles between energy levels. It also discusses the probability distribution of particles between energy levels for large systems. For the Einstein solid model, it describes a solid as 3N independent quantum harmonic oscillators, each with discrete energy levels defined by integers. It provides expressions for the total internal energy of the system.
Engineering physics 5(Quantum free electron theory)Nexus
This document discusses quantum free electron theory, which was developed by Sommerfeld in 1928 to explain physical properties that classical free electron theory could not. Quantum theory permits only a fraction of electrons to gain energy, as opposed to classical theory. It introduces the density of states and Fermi-Dirac distribution function to determine the number of electrons in a given energy range. The effect of temperature on the distribution function is also examined, showing that only states close to the Fermi level are affected at higher temperatures. An expression is provided for electrical conductivity based on quantum concepts involving the Fermi velocity and mean free path.
This document summarizes a seminar presentation on negative capacitance field-effect transistors (NC-FETs). It discusses how NC-FETs can reduce the subthreshold swing below the 60 mV/decade Boltzmann limit by using a ferroelectric material with negative capacitance as the gate insulator. This allows the subthreshold swing to be lowered, reducing power dissipation. Two types of NC-FET devices are described: ferroelectric FETs (FE-FETs) which use a ferroelectric gate insulator, and suspended-gate FETs which use air as the insulator. Advantages of NC-FETs include lower power, lower threshold voltage, and improved noise margins. Applications include high-
Zinc-air batteries use zinc as the anode and oxygen from the air as the cathode. They have a high energy density and range from button cells to applications in electric vehicles. Zinc reacts with hydroxyl ions at the anode to form zincate, releasing electrons. The zincate then decays into zinc oxide and water, which is recycled at the cathode. Reactions produce around 1.35-1.4 volts.
This document discusses the synthesis of polymer-derived boron-doped rare earth stabilized bismuth oxide nanocomposites for solid oxide fuel cell applications. It outlines the use of electrospinning and polymeric precursor techniques to produce nanocomposites of bismuth oxide stabilized with rare earth elements such as dysprosium, yttrium, holmium, erbium, and lanthanum. The document discusses how these techniques can produce nanocomposites with improved properties including higher ionic conductivity and strength due to reduced grain sizes.
Crystal defects occur when the regular patterns of atoms in crystalline materials are interrupted. There are several types of crystal defects including point defects, line defects, and plane defects. Point defects are defects that occur at or around a single lattice point and include vacancies, interstitials, and substitutions. Vacancies occur when an atom is missing from its normal position in the crystal lattice. Interstitials occur when an atom occupies a position between normal lattice sites. Substitutions occur when a foreign atom replaces a host atom in the lattice. The presence of defects is necessary for crystals to have stability at any non-zero temperature due to the contribution of defects to entropy.
The chapter discusses the quantum mechanical model of the hydrogen atom.
It begins by applying the Schrödinger equation to the hydrogen atom potential and separating the equation into radial, angular, and azimuthal parts. This leads to the quantization of energy into discrete allowed energy levels.
The chapter then introduces the key quantum numbers - principal (n), angular momentum (l), and magnetic (ml) - that arise from the separated equations. The values of these numbers and their relationships are defined.
Finally, the chapter discusses how an external magnetic field interacts with the magnetic moments of orbiting electrons and intrinsic spin, causing the Zeeman effect of spectral line splitting into multiple energy levels.
Neighbouring group participation, organic chemistry, M.SC.2JOYNA123
This document summarizes a student's report on neighbouring group participation in organic chemistry. It defines neighbouring group participation as the interaction of a reaction center with electrons in an adjacent atom, sigma bond, or pi bond. The document notes that NGP reactions proceed through an SN2 mechanism, involving attack of an internal nucleophile in the first step followed by substitution of an external nucleophile in the second step. This can lead to unexpected retention of configuration and a first-order reaction. Examples of NGP involving pi bonds and aromatic rings are also mentioned.
This document discusses band theory and several models used to describe electron behavior in solids, including the free electron model, nearly free electron model, and tight binding model. It provides an overview of each model, including their assumptions and how they describe properties like electron energy and band gaps. The free electron model treats electrons as independent particles but fails to explain material properties. The nearly free electron model incorporates a periodic potential and allows electron wavefunctions and energy bands to be described. The tight binding model uses a superposition of atomic orbitals to approximate electron wavefunctions in solids where potential is strong.
Since conversion of the fuel to energy takes place via an electrochemical process, not combustion.
It is a clean, quiet and highly efficient process- two to three times more efficient than fuel burning.
This document discusses variational principles and Lagrange's equations. It covers Hamilton's principle, the calculus of variations, deriving Lagrange's equations from Hamilton's principle, Hamilton's principle for nonholonomic systems, and conservation theorems. Key points include using Hamilton's principle to find the path that makes the action integral stationary, using the calculus of variations to find such paths, deriving Lagrange's equations by making the variation of the action integral equal to zero, and handling constraints using Lagrange multipliers.
This document discusses different types of battery technology. It introduces batteries and their components. There are three main types of batteries: primary cells which are not rechargeable, secondary cells which are rechargeable, and reserve batteries which have a long shelf life. Two specific battery technologies discussed are nickel-metal hydride batteries, which use metal hydrides as the anode, and lithium-ion batteries. Key characteristics of batteries include their emf, current, capacity, efficiency, cycle life, power density, and shelf life.
The document discusses energy band gaps in materials. It provides information on the density of electrons, energy gaps, and electric fields required for insulators, semiconductors, and metals. It then lists common materials used in semiconductors along with their band gap energies in electronvolts at 302 Kelvin. These include diamond, silicon dioxide, silicon, germanium, and lead sulfide. The document also discusses silicon-germanium alloys and intrinsic semiconductors. It covers doping, p-n junction diodes, their uses as electronic switches and rectifiers. Transistors are discussed for their uses as amplifiers, oscillators, and in integrated circuits. Radio broadcasting and reception is also mentioned
CMOS (complementary metal oxide semiconductor) technology continues to be the
dominant technology for fabricating integrated circuits (ICs or chips). This dominance
will likely continue for the next 25 years and perhaps even longer. Why? CMOS
technology is reliable, manufacturable, low power, low cost, and, perhaps most
importantly, scalable. The fact that silicon integrated circuit technology is scalable was
observed and described in 1965 by Intel founder Gordon Moore. His observations are
now referred to as Moore's law and state that the number of devices on a chip will double
every 18 to 24 months. While originally not specific to CMOS, Moore's law has been
fulfilled over the years by scaling down the feature size in CMOS technology. Whereas
the gate lengths of early CMOS transistors were in the micrometer range (long-channel
devices) the feature sizes of current CMOS devices are in the nanometer range
(short-channel devices).
To encompass both the long- and short-channel CMOS technologies in this book,
a two-path approach to custom CMOS integrated circuit design is adopted. Design
techniques are developed for both and then compared. This comparison gives readers
deep insight into the circuit design process. While the square-law equations used to
describe MOSFET operation that students learn in an introductory course in
microelectronics can be used for analog design in a long-channel CMOS process they are
not useful when designing in short-channel, or nanometer, CMOS technology. The
behavior of the devices in a nanometer CMOS process is quite complex. Simple
equations to describe the devices' behavior are not possible. Rather electrical plots are
used to estimate biasing points and operating behavior. It is still useful, however, for the
student to use mathematical rigor when learning circuit analysis and design and, hence,
the reason for the two-path approach. Hand calculations can be performed using a
long-channel CMOS technology with the results then used to describe how to design in a
nano-CMOS process.
This document summarizes a presentation on solid electrolytes. It discusses how solid electrolytes exhibit ionic conductivity through mobile anions or cations, with maximum conductivity between 0.1-10 Ohm-1cm-1. Examples of solid electrolytes mentioned include AgI, β-alumina, and zirconia. Applications discussed include use in batteries, oxygen sensors, and solid oxide fuel cells. The proposed work is to synthesize and characterize Sr and Cu doped LaAlO3 as a potential solid electrolyte material.
The document discusses experiments on the stability of SOFC cathodes and the development of a novel test system. It focuses on studying the stability of a barium-based cathode material (La0.5Ba0.5CoO3-δ) when exposed to carbon dioxide through thermodynamic and kinetic analysis. The key reactions, pathways and kinetics of carbonate formation are examined through TGA and HT-XRD experiments. An equilibrium phase diagram is proposed. Additionally, a test system is developed to enable rapid testing of multiple electrodes through a materials printer and micro contact impedance spectroscopy. This allows reproducible fabrication and evaluation of many electrode compositions.
Dr. K. Ramya gave a lecture on superconductivity. The BCS theory proposed by Bardeen, Cooper and Schrieffer explains electron-phonon interaction in superconductors. In normal conductors, electrons scatter off vibrating atoms, increasing resistance. In superconductors, electron-phonon interaction decreases scattering, lowering energy. Electrons form Cooper pairs with equal and opposite momenta. Below a critical temperature, interaction between Cooper pairs and the positive ion core vanishes, resulting in zero resistivity and superconductivity. Applications of superconductivity include more efficient electrical generators, transformers, transmission lines, magnetic levitation, fast electrical switching, computer logic and storage, SQUIDs for magnetometry, and
Solid oxide fuel cells (SOFCs) use solid ceramic electrolytes to transport oxygen ions between the cathode and anode. They can operate on hydrogen or natural gas fuels from 700-1000°C. Perovskite materials are commonly used as electrodes or electrolytes due to their mixed ionic and electronic conductivity. SOFCs offer clean electricity generation but challenges remain in reducing costs and operating temperatures before widespread commercialization. Research is ongoing to develop new materials with improved performance at lower temperatures.
Ferroelectricity refers to materials that exhibit permanent electric polarization even in the absence of an external electric field. Materials that display this behavior are known as ferroelectric materials. Examples include lead titanate and lead zirconate titanate. Ferroelectric materials have applications in devices such as thermistors, oscillators, memory, and capacitors due to their large dielectric constants and ability to remain polarized in the absence of a field. Pyroelectricity is the ability of a material to generate an electric signal when subjected to thermal changes, and leads to applications in infrared sensors and thermometers. Ferroelectric hysteresis curves plot the polarization versus applied electric field and exhibit hysteresis behavior.
This document discusses the density of states (DoS) for bulk semiconductors. It begins by defining DoS as the number of available energy states per unit energy interval per unit dimension in real space. It then derives the DoS for bulk semiconductors using the Bloch theorem and shows that the DoS is proportional to the square root of energy. Finally, it defines the effective DoS, which accounts for occupancy based on the Fermi-Dirac distribution.
Two port network parameters, Z, Y, ABCD, h and g parameters, Characteristic impedance,
Image transfer constant, image and iterative impedance, network function, driving point and
transfer functions – using transformed (S) variables, Poles and Zeros.
The document summarizes a master's thesis defense on high pressure steam reactivation of calcium oxide (CaO) sorbents for carbon dioxide capture using calcium looping process. It discusses:
1) The introduction, experimental methodology, results and discussions, conclusions, and future work sections of the thesis.
2) Current CO2 levels and emissions from electricity production in the US, highlighting the need for carbon capture from coal and natural gas power plants.
3) Existing carbon capture technologies like amine scrubbing and their limitations.
4) The calcium looping process for post-combustion CO2 capture and limitations in maintaining sorbent reactivity over multiple cycles.
5) Reactivation of
The document summarizes key concepts from a lecture on combinatorics, probability, and multiplicity as they relate to statistical mechanics. It discusses two model systems - a two-state paramagnet and the Einstein solid. For the paramagnet, it defines the energy levels and multiplicity of macrostates. The multiplicity represents the number of configurations or arrangements of particles between energy levels. It also discusses the probability distribution of particles between energy levels for large systems. For the Einstein solid model, it describes a solid as 3N independent quantum harmonic oscillators, each with discrete energy levels defined by integers. It provides expressions for the total internal energy of the system.
Engineering physics 5(Quantum free electron theory)Nexus
This document discusses quantum free electron theory, which was developed by Sommerfeld in 1928 to explain physical properties that classical free electron theory could not. Quantum theory permits only a fraction of electrons to gain energy, as opposed to classical theory. It introduces the density of states and Fermi-Dirac distribution function to determine the number of electrons in a given energy range. The effect of temperature on the distribution function is also examined, showing that only states close to the Fermi level are affected at higher temperatures. An expression is provided for electrical conductivity based on quantum concepts involving the Fermi velocity and mean free path.
This document summarizes a seminar presentation on negative capacitance field-effect transistors (NC-FETs). It discusses how NC-FETs can reduce the subthreshold swing below the 60 mV/decade Boltzmann limit by using a ferroelectric material with negative capacitance as the gate insulator. This allows the subthreshold swing to be lowered, reducing power dissipation. Two types of NC-FET devices are described: ferroelectric FETs (FE-FETs) which use a ferroelectric gate insulator, and suspended-gate FETs which use air as the insulator. Advantages of NC-FETs include lower power, lower threshold voltage, and improved noise margins. Applications include high-
Zinc-air batteries use zinc as the anode and oxygen from the air as the cathode. They have a high energy density and range from button cells to applications in electric vehicles. Zinc reacts with hydroxyl ions at the anode to form zincate, releasing electrons. The zincate then decays into zinc oxide and water, which is recycled at the cathode. Reactions produce around 1.35-1.4 volts.
This document discusses the synthesis of polymer-derived boron-doped rare earth stabilized bismuth oxide nanocomposites for solid oxide fuel cell applications. It outlines the use of electrospinning and polymeric precursor techniques to produce nanocomposites of bismuth oxide stabilized with rare earth elements such as dysprosium, yttrium, holmium, erbium, and lanthanum. The document discusses how these techniques can produce nanocomposites with improved properties including higher ionic conductivity and strength due to reduced grain sizes.
Crystal defects occur when the regular patterns of atoms in crystalline materials are interrupted. There are several types of crystal defects including point defects, line defects, and plane defects. Point defects are defects that occur at or around a single lattice point and include vacancies, interstitials, and substitutions. Vacancies occur when an atom is missing from its normal position in the crystal lattice. Interstitials occur when an atom occupies a position between normal lattice sites. Substitutions occur when a foreign atom replaces a host atom in the lattice. The presence of defects is necessary for crystals to have stability at any non-zero temperature due to the contribution of defects to entropy.
The chapter discusses the quantum mechanical model of the hydrogen atom.
It begins by applying the Schrödinger equation to the hydrogen atom potential and separating the equation into radial, angular, and azimuthal parts. This leads to the quantization of energy into discrete allowed energy levels.
The chapter then introduces the key quantum numbers - principal (n), angular momentum (l), and magnetic (ml) - that arise from the separated equations. The values of these numbers and their relationships are defined.
Finally, the chapter discusses how an external magnetic field interacts with the magnetic moments of orbiting electrons and intrinsic spin, causing the Zeeman effect of spectral line splitting into multiple energy levels.
Neighbouring group participation, organic chemistry, M.SC.2JOYNA123
This document summarizes a student's report on neighbouring group participation in organic chemistry. It defines neighbouring group participation as the interaction of a reaction center with electrons in an adjacent atom, sigma bond, or pi bond. The document notes that NGP reactions proceed through an SN2 mechanism, involving attack of an internal nucleophile in the first step followed by substitution of an external nucleophile in the second step. This can lead to unexpected retention of configuration and a first-order reaction. Examples of NGP involving pi bonds and aromatic rings are also mentioned.
This document discusses band theory and several models used to describe electron behavior in solids, including the free electron model, nearly free electron model, and tight binding model. It provides an overview of each model, including their assumptions and how they describe properties like electron energy and band gaps. The free electron model treats electrons as independent particles but fails to explain material properties. The nearly free electron model incorporates a periodic potential and allows electron wavefunctions and energy bands to be described. The tight binding model uses a superposition of atomic orbitals to approximate electron wavefunctions in solids where potential is strong.
Since conversion of the fuel to energy takes place via an electrochemical process, not combustion.
It is a clean, quiet and highly efficient process- two to three times more efficient than fuel burning.
This document discusses variational principles and Lagrange's equations. It covers Hamilton's principle, the calculus of variations, deriving Lagrange's equations from Hamilton's principle, Hamilton's principle for nonholonomic systems, and conservation theorems. Key points include using Hamilton's principle to find the path that makes the action integral stationary, using the calculus of variations to find such paths, deriving Lagrange's equations by making the variation of the action integral equal to zero, and handling constraints using Lagrange multipliers.
This document discusses different types of battery technology. It introduces batteries and their components. There are three main types of batteries: primary cells which are not rechargeable, secondary cells which are rechargeable, and reserve batteries which have a long shelf life. Two specific battery technologies discussed are nickel-metal hydride batteries, which use metal hydrides as the anode, and lithium-ion batteries. Key characteristics of batteries include their emf, current, capacity, efficiency, cycle life, power density, and shelf life.
The document discusses energy band gaps in materials. It provides information on the density of electrons, energy gaps, and electric fields required for insulators, semiconductors, and metals. It then lists common materials used in semiconductors along with their band gap energies in electronvolts at 302 Kelvin. These include diamond, silicon dioxide, silicon, germanium, and lead sulfide. The document also discusses silicon-germanium alloys and intrinsic semiconductors. It covers doping, p-n junction diodes, their uses as electronic switches and rectifiers. Transistors are discussed for their uses as amplifiers, oscillators, and in integrated circuits. Radio broadcasting and reception is also mentioned
CMOS (complementary metal oxide semiconductor) technology continues to be the
dominant technology for fabricating integrated circuits (ICs or chips). This dominance
will likely continue for the next 25 years and perhaps even longer. Why? CMOS
technology is reliable, manufacturable, low power, low cost, and, perhaps most
importantly, scalable. The fact that silicon integrated circuit technology is scalable was
observed and described in 1965 by Intel founder Gordon Moore. His observations are
now referred to as Moore's law and state that the number of devices on a chip will double
every 18 to 24 months. While originally not specific to CMOS, Moore's law has been
fulfilled over the years by scaling down the feature size in CMOS technology. Whereas
the gate lengths of early CMOS transistors were in the micrometer range (long-channel
devices) the feature sizes of current CMOS devices are in the nanometer range
(short-channel devices).
To encompass both the long- and short-channel CMOS technologies in this book,
a two-path approach to custom CMOS integrated circuit design is adopted. Design
techniques are developed for both and then compared. This comparison gives readers
deep insight into the circuit design process. While the square-law equations used to
describe MOSFET operation that students learn in an introductory course in
microelectronics can be used for analog design in a long-channel CMOS process they are
not useful when designing in short-channel, or nanometer, CMOS technology. The
behavior of the devices in a nanometer CMOS process is quite complex. Simple
equations to describe the devices' behavior are not possible. Rather electrical plots are
used to estimate biasing points and operating behavior. It is still useful, however, for the
student to use mathematical rigor when learning circuit analysis and design and, hence,
the reason for the two-path approach. Hand calculations can be performed using a
long-channel CMOS technology with the results then used to describe how to design in a
nano-CMOS process.
This document summarizes a presentation on solid electrolytes. It discusses how solid electrolytes exhibit ionic conductivity through mobile anions or cations, with maximum conductivity between 0.1-10 Ohm-1cm-1. Examples of solid electrolytes mentioned include AgI, β-alumina, and zirconia. Applications discussed include use in batteries, oxygen sensors, and solid oxide fuel cells. The proposed work is to synthesize and characterize Sr and Cu doped LaAlO3 as a potential solid electrolyte material.
The document discusses experiments on the stability of SOFC cathodes and the development of a novel test system. It focuses on studying the stability of a barium-based cathode material (La0.5Ba0.5CoO3-δ) when exposed to carbon dioxide through thermodynamic and kinetic analysis. The key reactions, pathways and kinetics of carbonate formation are examined through TGA and HT-XRD experiments. An equilibrium phase diagram is proposed. Additionally, a test system is developed to enable rapid testing of multiple electrodes through a materials printer and micro contact impedance spectroscopy. This allows reproducible fabrication and evaluation of many electrode compositions.
This document summarizes research on the electrical conductivity of Ba-Sr-Co-Fe cathode materials for solid oxide fuel cells (SOFCs). Single phase cubic Ba0.5Sr0.5Co1-xFexO3-δ compositions were synthesized via gel combustion and cation complexation routes. Electrical conductivity measurements showed that conductivity initially increased with temperature up to a maximum then decreased, attributed to oxygen loss from the lattice. Fe substitution had little effect on conductivity. While BSCF shows potential as an SOFC cathode, further work is needed to increase conductivity to meet requirements of current IT-SOFCs.
This document provides contact information for Senta Wessels, an architect and technology expert. It lists her name, phone number, and email address. Senta Wessels can be reached at 079 522 0003 or wsenta@gmail.com regarding architectural and technology services.
The document summarizes a presentation on developing composite anode materials of yttria-stabilized zirconia (YSZ), zinc-doped ceria (CZO), and nickel-nickel oxide (Ni:NiO) for intermediate-temperature solid oxide fuel cells. Nanoparticles of YSZ, CZO, and Ni:NiO were synthesized using a sol-gel method and characterized. Composites with varying volume ratios of the components were fabricated by ball milling. Characterization showed the intended crystal structures were obtained. Future work proposed testing the materials' electrochemical and mechanical properties to evaluate their suitability as low-temperature fuel cell anodes.
Fuel cell electric vehicles and hydrogen fuel for CaliforniaChris White
Presentation by Catherine Dunwoody for the California Energy Commission at the July 31, 2013 Integrated Energy Policy Report (IEPR) workshop about the role that FCEVs can play in 2050.
Relating Microstructure and Ionic Conductivity in Calcium Doped Ceria for sol...Cruz Hernandez
This document summarizes research into improving the ionic conductivity of calcium doped ceria for use as a solid oxide fuel cell electrolyte. Ceria was doped with varying concentrations of calcium from 2-10% using a spray drying technique. X-ray diffraction analysis showed the cubic fluorite structure was maintained with doping. Electrical characterization found that 5% calcium doping yielded the highest ionic conductivity, with grain and grain boundary conductivity dependent on dopant concentration. Scanning electron microscopy revealed the average grain size also varied with calcium concentration.
Pd-Substituted (La,Sr)CrO3 for Solid Oxide Fuel Cell AnodesEmmaReneeDutton
Presentation of independent honors research thesis (June 2011) for Bachelor of Science in Materials Science & Engineering at Northwestern University.
This document summarizes a presentation given by Gurpreet Kaur on the performance studies of copper-iron/ceria-yttria stabilized zirconia anode for solid oxide fuel cells. The objectives were to fabricate SOFCs in the lab using tape casting and to prepare Cu/CeO2-YSZ and Cu-Fe/CeO2-YSZ anodes for characterization and performance testing in hydrogen and methane fuels. Characterization showed that addition of iron to Cu-based anodes improved catalyst dispersion and electrical conduction. Performance testing found that power density increased from 190 to 330 mW/cm2 with increasing iron content in the Cu-Fe/CeO2-YSZ anode composition
This document summarizes an internship project on synthesizing nanopowders for solid oxide fuel cell anodes using plasma spraying. The intern aimed to synthesize a pure nanostructured phase of lanthanum doped ceria using solution plasma spraying. Tests were also conducted to deposit a coating of lanthanum strontium titanate and yttria-stabilized zirconia on a thin disk using suspension plasma spraying. The intern obtained promising results for synthesizing lanthanum doped ceria powder but needs to improve the quality of the composite coating and overcome issues of thermal shock. Future work involves repeating ceria synthesis, developing a new substrate, and testing a lanthanum doped ceria, lanthan
Transmission electron microscopy (TEM) is important tools for surface and interface study. Electron Energy Loss Spectroscopy (EELS) belongs to the TEM family, I added some know-how about DFT simulation of EELS spectrum. I showed some tricks and caution which I found important. Please send me a note for questions and comments
Solid oxide fuel cells (SOFCs) are highly viable for alternative energy due to their ability to operate using various fossil fuel impurities and internally reform methane. SOFCs are also economically advantageous because they utilize heat absorption to reduce cooling needs and can operate at lower temperatures than similar fuel cells using inexpensive stainless steel. Additionally, SOFCs facilitate high levels of carbon capture through the separation of fuel and air streams.
The document summarizes an experimental analysis of converting a 1400 cc diesel engine car into a hybrid electric vehicle using BLDC hub motors. Key findings include:
1) The conversion achieved fuel savings of 45-61% compared to the conventional vehicle through the use of lower power hub motors and a separate battery pack for the electric motors.
2) Performance of the vehicle was retained after conversion, with no changes needed to the existing electrical or hydraulic brake systems.
3) The proposed conversion method could be easily implemented on many existing small cars with front-wheel drive to reduce emissions and fuel consumption cost-effectively.
M. Padmini and Dr. Manoj S. Soni presented on concentrating solar photovoltaics at the IVth International Conference on Advances in Energy Research at IIT Bombay from December 10-12, 2013. Their presentation discussed various concentrating photovoltaic techniques including parabolic concentrators, hyperboloid concentrators, Fresnel lenses, compound parabolic concentrators, and quantum dot concentrators. It provided details on how each technique works and its advantages. It also discussed recent developments like rod lenses and solar spheres. Finally, it analyzed the potential cost savings of a 30MW concentrating solar farm in India compared to a non-concentrating system, finding that concentration could reduce costs from Rs. 200
The document summarizes heat and mass transfer characteristics of direct methanol fuel cells (DMFCs) based on experiments and modeling. Key points:
- A 3D non-isothermal model is developed to predict methanol and temperature distributions in the anode. Experimental results validate the model.
- Increasing methanol concentration does not significantly impact net water generation but does increase methanol crossover, affecting cell performance.
- At 1M methanol concentration and 230mA/cm2 current density, the fuel utilization efficiency is 57% despite high methanol crossover.
- Temperature distribution shows methanol solution heated to 57°C from 27°C, improving cell performance. Double channel serpentine flow field aids methanol diffusion.
A solid oxide fuel cell (SOFC) works by using oxygen ions conducting through a solid ceramic electrolyte to generate electricity from hydrogen or other fuels. It consists of an anode and cathode separated by an electrolyte, and produces electricity through an electrochemical reaction without combustion. SOFCs operate at high temperatures between 1000-1800 degrees F, which allows them to use a wide variety of fuels. They are more efficient than traditional power generation and are being developed for applications such as stationary power plants, transportation, and residential use.
Tor A Fjeldly and Muhammad Nawaz submitted a master's thesis on the formation of silicon nanostructures in silicon nitride thin films for use in solar cells. The goal was to develop silicon nitride anti-reflective coatings containing silicon nanoparticles and characterize the films using ellipsometry. Seven silicon nitride films with varying stoichiometry were deposited using PECVD and characterized with ellipsometry, photoluminescence, and transmission electron microscopy before and after annealing. Ellipsometry showed the films became more compact after annealing with increased refractive index. Photoluminescence was observed for samples with high ammonia flow but decreased after annealing, while samples with low ammonia flow showed little photolum
1) The document discusses using a soap film experiment to visualize and understand the wake interactions between multiple piezoelectric cantilevers used for wind energy harvesting.
2) Two models were tested in the soap film tunnel - a single cantilever and two cantilevers placed 8 mm apart.
3) The soap film experiment setup includes a vertical tunnel with divergent, test, and convergent sections to produce a constant velocity soap film for visualizing vortex shedding and flows.
Analysis Of Carbon Nanotubes And Quantum Dots In A Photovoltaic DeviceM. Faisal Halim
Analysis of Carbon Nanotubes and Quantum Dots in a Photovoltaic Device
A poster prepared by Francis and me; presented by Francis. I modified on of the photographs used, in this copy.
Drop formation in liquid-liquid systems was studied experimentally using high-speed imaging. Different phase systems were used including a system relevant to nuclear applications (TBP-nitric acid-water). Drop diameter, detachment height, and time were measured for variations in hole diameter, pitch, plate spacing, and flow asymmetry. Drop diameter increased with hole velocity and diameter but showed a maximum with pitch. Detachment height and time decreased with hole velocity. Intermittent drops were seen at low velocities for large pitch in the nuclear system. Drop size increased at smaller plate spacings. Flow asymmetry had little effect. The study provides insights useful for mass transfer processes in nuclear industries.
This document summarizes an analysis of the fatigue life of a tubesheet used in an industrial filtration system. The analysis involved:
1) Calculating the dimensions of the tubesheet based on client specifications.
2) Performing static and transient dynamic finite element analyses to determine stress and deformation values under different loading conditions.
3) Using the stress and deformation results to predict the fatigue life of the tubesheet according to ASME codes.
4) Validating the FEA results by comparing predicted and measured deformation values from an actual hydrotest.
The analysis found that the tubesheet could withstand the alternating stresses from the filtration process cycles for an infinite fatigue life.
This document discusses the effects of photoanode thickness on the performance of dye-sensitized solar cells (DSSC) simulated using an equivalent circuit model. Three DSSCs were fabricated with TiO2 absorption layer thicknesses of 6 μm, 12 μm, and 18 μm. Their current-voltage characteristics were measured and fitted to an equivalent circuit model. The model shows that both the series resistance (Rs) and shunt resistance (Rsh) increase with thicker absorption layers. It also shows that increasing Rs decreases the fill factor, while cell efficiency decreases as the material thickness increases due to increased resistance.
Final Report for CHEME 5650 Huawei ZhouHuawei Zhou
This report describes a project to enhance a slot-die coating setup and use it to coat various materials. The author designed additional parts for the coating head and controlled equipment like the syringe pump, temperature controller, and stepping motor. Experiments coated water, isopropanol, anthracene solution, dye solutions, and pyrene to understand the coating process and material properties. Field effect transistors were also fabricated from some coated films and tested.
Manufacture and Testing of Building Integrated Photovoltaic systemSharathKumar528
This work is my dissertation project on the Manufacture and testing of building Integrated concentrating Photovoltaic system for the fulfilment of masters degree in Renewable Energy Engineering, University of Exeter,Penryn, UK
This document evaluates the modal damping of graphite/epoxy laminated composites through experimental testing. Graphite/epoxy laminate composite plates of different thicknesses (2mm and 4mm) and fiber orientations (0 and 45 degrees) were fabricated and tested under different boundary conditions (cantilever, two sides fixed, all sides fixed) using an impulse excitation technique. The results show that modal damping decreases with increasing laminate thickness and is sensitive to changes in boundary conditions. Damping was highest for the cantilever boundary condition and lowest for the two sides fixed condition. Evaluation of modal damping through experimental modal analysis provides a simple and effective technique for characterizing damping properties of composite laminates.
Production and characterization of nano copper powder using electric explosio...eSAT Publishing House
This document summarizes research on producing nano copper powder using an electric explosion process in liquid media. Key points:
- Nanoparticles were produced by exploding copper wires submerged in distilled water using a high voltage capacitor charged to 30-40kV.
- Particle size could be controlled by varying the injected power. Size was analyzed using SEM and TEM, with most particles between 200-500nm.
- A centrifugal separator was used to classify particles by size. Smaller particles precipitated at higher rpm settings.
- The process successfully produced copper nanoparticles, though some submicron particles also formed from non-vaporized liquid droplets.
The report summarizes the design and fabrication of electrospray sources for electric propulsion conducted during an 8-month cooperative work term. The goals were to mount a new laboratory and design single emitter and multi-emitter array prototypes. Key conclusions include adding oxygen during deep reactive ion etching improved prototype fabrication by reducing silica grass formation. The mounted laboratory and completed prototype designs achieve the research goals. Recommendations include further calibrating test equipment and conducting prototype performance tests after mounting is fully complete.
Fabrication of microfluidic channels in glass and siliconYichen Sun
Microfluidic channels in glass and silicon chips are fabricated in the cleanroom. Their acoustic focusing properties are then tested and reported in this project report (MEMS 5801).
This report discusses an experiment on flow visualization of electro-kinetic force chemical mechanical planarization (EKF-CMP). Straight and radial electrode specimens were created in glass chambers to observe flow patterns under various voltages and solution conditions using video and simulations. Results showed that lower gap lengths and radial electrode orientation produced faster fluid flow. While solution pH had little effect, EKF-CMP was found to significantly improve material removal rate over conventional CMP, making it suitable for creating refined 3D stacked wafers needed to satisfy Moore's Law. In conclusion, the experiment validated that external voltage application enhances CMP performance.
This document is a thesis submitted by Yishi Lee to Embry-Riddle Aeronautical University for the degree of Master of Science in Engineering Physics. The thesis developed a new 3-D model of the high-latitude ionosphere to study the coupling between the ionosphere, magnetosphere, and neutral atmosphere. The model consists of equations describing the conservation of mass, momentum, and energy for six ionospheric constituents, as well as an electrostatic potential equation. The thesis was prepared under the direction of Dr. Matthew Zettergren and other committee members. It uses the 3-D model to examine ion heating, plasma structuring due to perpendicular transport, ion upflow, molecular ion generation, and neutral wave forcing in
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Electrochemical impedance spectroscopy on thermal ageing evaluation of epoxy ...eSAT Journals
Abstract This research concentrates on the thermal ageing of a full 3-coat system with sacrificial pigment (zinc rich) primer on mild steel where the temperature dependence test is conducted to explore the correlation between the coating resistances with the corrosion rate underneath the coating. Electrochemical impedance spectroscopy (EIS) is introduced over a range of temperature to extract activation energies for the rate of controlling processes in the corrosion reactions. It is expected that the zinc rich primer does not form a barrier coating for the metal substrate rather it will be the most active component of the substrate in the electrochemistry. Full 3-coat system with zinc rich primer show the extracted activation energy from coating resistance is significantly lower than the activation energy extracted from the charge transfer resistance. This suggested that the coating resistance from EIS cannot be controlling the corrosion reaction. The activation energies generated for the corrosion process here (78–97 kJmol-1) are very much higher than those of ion transport through the coating (19–37 kJmol-1) during early immersion. Further interesting findings come from the activation energy trends over time particularly for the corrosion process which shown that the value is decreasing where at the end of exposure, the activation energy values for coating and charge transfer resistance become quite similar. It is suggested that at this stage ion transport in the coating might be controlling the corrosion process unlike at the beginning; the activation energy is getting smaller due to coating degradation. Index Terms: epoxy coating, electrochemical impedance spectroscopy, thermal effect, zinc rich primer
IRJET- A Research Paper on Design and Experimentation on Continuous Loop Demu...IRJET Journal
This document summarizes a research paper on the design and experimentation of a continuous loop demulsifier. The demulsifier uses electrocoalescence to separate water from crude oil by inducing opposite charges on water droplets using an electrostatic field, causing them to coalesce into larger droplets that settle out of the oil due to gravity. Key components of the developed system include distributor and collector tubes, grid electrodes to generate a uniform electric field, a pump to continuously feed the emulsion, and an acrylic vessel to hold it all. Experimental results showed this to be an effective low-cost method for continuous crude oil demulsification.
Carbon Nanotubes Effect for Polymer Materials on Break Down Voltage IJECEIAES
Epoxy resin composites reinforced to different types of carbon nano-particles have been fabricated. Carbon black (20, 30 and 40 wt. %), graphene (0.5 to 4 wt. %) and carbon nanotubes (CNT) (0.5 to 2 wt. %) were added with different weight percentages to epoxy. The dielectric strength of composites was tested in several conditions such as (dry, wet, low salinity and high salinity). The mechanical characterization showed that the nano-composite Polymer enhanced by using these particles in the tensile strength. Thermal gravimetric analysis shows effect of these nano-particles on the thermal structure of epoxy resin. Scanning Electron Microscopic test is used to characterize the dispersion of carbon nano-particles and to analysis the fractured parts in the nano scale.
This document discusses a roller electrospinning system for producing nanofibers at higher rates than traditional needle electrospinning. The researchers tested polyurethane solutions with varying concentrations of lithium chloride salt. Adding salt increased the solution's viscosity and conductivity. Higher salt concentrations led to higher spinning performance up to 3 g/min/m and increased fiber diameters. The roller electrospinning system was able to efficiently produce nanofibers at an industrial scale.
The document is a dissertation submitted by Mahato Lipika for the degree of Master of Science in Computer Control and Automation in 2016. It discusses leak location detection in gas pipeline networks. Chapter 1 introduces the background of gas pipeline networks in Singapore and the motivation for leak detection. The objective is to analyze pressure profile data using different methods to locate leaks in the network. Chapter 2 reviews literature on gas pipeline networks, leak detection techniques, and computational fluid dynamics modeling. Chapter 3 describes initial calculations, experiments conducted to collect pressure profile data from a test network setup under different leak conditions. Chapter 4 presents results of analyzing the data using various methods to locate leaks. Chapter 5 provides conclusions and suggestions for future work.
Driving Business Innovation: Latest Generative AI Advancements & Success StorySafe Software
Are you ready to revolutionize how you handle data? Join us for a webinar where we’ll bring you up to speed with the latest advancements in Generative AI technology and discover how leveraging FME with tools from giants like Google Gemini, Amazon, and Microsoft OpenAI can supercharge your workflow efficiency.
During the hour, we’ll take you through:
Guest Speaker Segment with Hannah Barrington: Dive into the world of dynamic real estate marketing with Hannah, the Marketing Manager at Workspace Group. Hear firsthand how their team generates engaging descriptions for thousands of office units by integrating diverse data sources—from PDF floorplans to web pages—using FME transformers, like OpenAIVisionConnector and AnthropicVisionConnector. This use case will show you how GenAI can streamline content creation for marketing across the board.
Ollama Use Case: Learn how Scenario Specialist Dmitri Bagh has utilized Ollama within FME to input data, create custom models, and enhance security protocols. This segment will include demos to illustrate the full capabilities of FME in AI-driven processes.
Custom AI Models: Discover how to leverage FME to build personalized AI models using your data. Whether it’s populating a model with local data for added security or integrating public AI tools, find out how FME facilitates a versatile and secure approach to AI.
We’ll wrap up with a live Q&A session where you can engage with our experts on your specific use cases, and learn more about optimizing your data workflows with AI.
This webinar is ideal for professionals seeking to harness the power of AI within their data management systems while ensuring high levels of customization and security. Whether you're a novice or an expert, gain actionable insights and strategies to elevate your data processes. Join us to see how FME and AI can revolutionize how you work with data!
Monitoring and Managing Anomaly Detection on OpenShift.pdfTosin Akinosho
Monitoring and Managing Anomaly Detection on OpenShift
Overview
Dive into the world of anomaly detection on edge devices with our comprehensive hands-on tutorial. This SlideShare presentation will guide you through the entire process, from data collection and model training to edge deployment and real-time monitoring. Perfect for those looking to implement robust anomaly detection systems on resource-constrained IoT/edge devices.
Key Topics Covered
1. Introduction to Anomaly Detection
- Understand the fundamentals of anomaly detection and its importance in identifying unusual behavior or failures in systems.
2. Understanding Edge (IoT)
- Learn about edge computing and IoT, and how they enable real-time data processing and decision-making at the source.
3. What is ArgoCD?
- Discover ArgoCD, a declarative, GitOps continuous delivery tool for Kubernetes, and its role in deploying applications on edge devices.
4. Deployment Using ArgoCD for Edge Devices
- Step-by-step guide on deploying anomaly detection models on edge devices using ArgoCD.
5. Introduction to Apache Kafka and S3
- Explore Apache Kafka for real-time data streaming and Amazon S3 for scalable storage solutions.
6. Viewing Kafka Messages in the Data Lake
- Learn how to view and analyze Kafka messages stored in a data lake for better insights.
7. What is Prometheus?
- Get to know Prometheus, an open-source monitoring and alerting toolkit, and its application in monitoring edge devices.
8. Monitoring Application Metrics with Prometheus
- Detailed instructions on setting up Prometheus to monitor the performance and health of your anomaly detection system.
9. What is Camel K?
- Introduction to Camel K, a lightweight integration framework built on Apache Camel, designed for Kubernetes.
10. Configuring Camel K Integrations for Data Pipelines
- Learn how to configure Camel K for seamless data pipeline integrations in your anomaly detection workflow.
11. What is a Jupyter Notebook?
- Overview of Jupyter Notebooks, an open-source web application for creating and sharing documents with live code, equations, visualizations, and narrative text.
12. Jupyter Notebooks with Code Examples
- Hands-on examples and code snippets in Jupyter Notebooks to help you implement and test anomaly detection models.
Salesforce Integration for Bonterra Impact Management (fka Social Solutions A...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on integration of Salesforce with Bonterra Impact Management.
Interested in deploying an integration with Salesforce for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
UiPath Test Automation using UiPath Test Suite series, part 6DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 6. In this session, we will cover Test Automation with generative AI and Open AI.
UiPath Test Automation with generative AI and Open AI webinar offers an in-depth exploration of leveraging cutting-edge technologies for test automation within the UiPath platform. Attendees will delve into the integration of generative AI, a test automation solution, with Open AI advanced natural language processing capabilities.
Throughout the session, participants will discover how this synergy empowers testers to automate repetitive tasks, enhance testing accuracy, and expedite the software testing life cycle. Topics covered include the seamless integration process, practical use cases, and the benefits of harnessing AI-driven automation for UiPath testing initiatives. By attending this webinar, testers, and automation professionals can gain valuable insights into harnessing the power of AI to optimize their test automation workflows within the UiPath ecosystem, ultimately driving efficiency and quality in software development processes.
What will you get from this session?
1. Insights into integrating generative AI.
2. Understanding how this integration enhances test automation within the UiPath platform
3. Practical demonstrations
4. Exploration of real-world use cases illustrating the benefits of AI-driven test automation for UiPath
Topics covered:
What is generative AI
Test Automation with generative AI and Open AI.
UiPath integration with generative AI
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Digital Marketing Trends in 2024 | Guide for Staying AheadWask
https://www.wask.co/ebooks/digital-marketing-trends-in-2024
Feeling lost in the digital marketing whirlwind of 2024? Technology is changing, consumer habits are evolving, and staying ahead of the curve feels like a never-ending pursuit. This e-book is your compass. Dive into actionable insights to handle the complexities of modern marketing. From hyper-personalization to the power of user-generated content, learn how to build long-term relationships with your audience and unlock the secrets to success in the ever-shifting digital landscape.
Taking AI to the Next Level in Manufacturing.pdfssuserfac0301
Read Taking AI to the Next Level in Manufacturing to gain insights on AI adoption in the manufacturing industry, such as:
1. How quickly AI is being implemented in manufacturing.
2. Which barriers stand in the way of AI adoption.
3. How data quality and governance form the backbone of AI.
4. Organizational processes and structures that may inhibit effective AI adoption.
6. Ideas and approaches to help build your organization's AI strategy.
OpenID AuthZEN Interop Read Out - AuthorizationDavid Brossard
During Identiverse 2024 and EIC 2024, members of the OpenID AuthZEN WG got together and demoed their authorization endpoints conforming to the AuthZEN API
Fueling AI with Great Data with Airbyte WebinarZilliz
This talk will focus on how to collect data from a variety of sources, leveraging this data for RAG and other GenAI use cases, and finally charting your course to productionalization.
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-und-domino-lizenzkostenreduzierung-in-der-welt-von-dlau/
DLAU und die Lizenzen nach dem CCB- und CCX-Modell sind für viele in der HCL-Community seit letztem Jahr ein heißes Thema. Als Notes- oder Domino-Kunde haben Sie vielleicht mit unerwartet hohen Benutzerzahlen und Lizenzgebühren zu kämpfen. Sie fragen sich vielleicht, wie diese neue Art der Lizenzierung funktioniert und welchen Nutzen sie Ihnen bringt. Vor allem wollen Sie sicherlich Ihr Budget einhalten und Kosten sparen, wo immer möglich. Das verstehen wir und wir möchten Ihnen dabei helfen!
Wir erklären Ihnen, wie Sie häufige Konfigurationsprobleme lösen können, die dazu führen können, dass mehr Benutzer gezählt werden als nötig, und wie Sie überflüssige oder ungenutzte Konten identifizieren und entfernen können, um Geld zu sparen. Es gibt auch einige Ansätze, die zu unnötigen Ausgaben führen können, z. B. wenn ein Personendokument anstelle eines Mail-Ins für geteilte Mailboxen verwendet wird. Wir zeigen Ihnen solche Fälle und deren Lösungen. Und natürlich erklären wir Ihnen das neue Lizenzmodell.
Nehmen Sie an diesem Webinar teil, bei dem HCL-Ambassador Marc Thomas und Gastredner Franz Walder Ihnen diese neue Welt näherbringen. Es vermittelt Ihnen die Tools und das Know-how, um den Überblick zu bewahren. Sie werden in der Lage sein, Ihre Kosten durch eine optimierte Domino-Konfiguration zu reduzieren und auch in Zukunft gering zu halten.
Diese Themen werden behandelt
- Reduzierung der Lizenzkosten durch Auffinden und Beheben von Fehlkonfigurationen und überflüssigen Konten
- Wie funktionieren CCB- und CCX-Lizenzen wirklich?
- Verstehen des DLAU-Tools und wie man es am besten nutzt
- Tipps für häufige Problembereiche, wie z. B. Team-Postfächer, Funktions-/Testbenutzer usw.
- Praxisbeispiele und Best Practices zum sofortigen Umsetzen
GraphRAG for Life Science to increase LLM accuracyTomaz Bratanic
GraphRAG for life science domain, where you retriever information from biomedical knowledge graphs using LLMs to increase the accuracy and performance of generated answers
Skybuffer SAM4U tool for SAP license adoptionTatiana Kojar
Manage and optimize your license adoption and consumption with SAM4U, an SAP free customer software asset management tool.
SAM4U, an SAP complimentary software asset management tool for customers, delivers a detailed and well-structured overview of license inventory and usage with a user-friendly interface. We offer a hosted, cost-effective, and performance-optimized SAM4U setup in the Skybuffer Cloud environment. You retain ownership of the system and data, while we manage the ABAP 7.58 infrastructure, ensuring fixed Total Cost of Ownership (TCO) and exceptional services through the SAP Fiori interface.
Ocean lotus Threat actors project by John Sitima 2024 (1).pptxSitimaJohn
Ocean Lotus cyber threat actors represent a sophisticated, persistent, and politically motivated group that poses a significant risk to organizations and individuals in the Southeast Asian region. Their continuous evolution and adaptability underscore the need for robust cybersecurity measures and international cooperation to identify and mitigate the threats posed by such advanced persistent threat groups.
Programming Foundation Models with DSPy - Meetup SlidesZilliz
Prompting language models is hard, while programming language models is easy. In this talk, I will discuss the state-of-the-art framework DSPy for programming foundation models with its powerful optimizers and runtime constraint system.
How to Interpret Trends in the Kalyan Rajdhani Mix Chart.pdfChart Kalyan
A Mix Chart displays historical data of numbers in a graphical or tabular form. The Kalyan Rajdhani Mix Chart specifically shows the results of a sequence of numbers over different periods.
How to Interpret Trends in the Kalyan Rajdhani Mix Chart.pdf
Master Thesis SOFC
1. SOLID OXIDE FUEL CELL:
DESIGN IMPROVEMENTS OF THE ELECTROSTATIC SPRAY
DEPOSITION SYSTEM AND CELL TEST STATION
DEVELOPMENT
BY
ARTURO VEIGA LÓPEZ
Submitted in partial fulfillment of the
requirements for the degree of
Master in Mechanical and Aerospace Engineering
in the Graduate College of the
Illinois Institute of Technology
Chicago, Illinois
October 2013
2. Master Project. Arturo Veiga López 2
Acknowledgements
Foremost, I would like to express my sincere gratitude to my advisor Prof. Philip Nash
for the continuous support during my stay in the Illinois Institute of Technology and
for giving me this opportunity; for his patience, motivation, and knowledge. His
guidance has helped me during my research. I would also like to thank Prof. Robert
Selman for his encouragement, insightful comments, and hard questions.
I thank my fellow labmate Quanzhi He, I am grateful to for his support and guidance in
the laboratory. I also would like to thank Russ Janota for his assistance throughout my
experiments.
Last, but not least, I would like to thank my sister Almudena for all her help and advice
during these years, for her support and encouragement, without you this wouldn´t be
possible. And also to my brother in law Carlos for his continuous encouragement.
My parents, Encarnación and Alfonso, receive my deepest gratitude and love for their
dedication and the many years of support during my undergraduate and college
studies that provided the foundation for this work.
3. Master Project. Arturo Veiga López 3
Table of contents
Acknowledgement………………………………………………………………………………………………. 2
List of figures………………………………………………………………………………………………………. 5
List of symbols…………………………………………………………………………………………………..... 8
Abstract……………………………………………………………………………………………………………… 10
Chapter
1. Introduction and background…………………………………………………………………11
1.1. Introduction……………………………………………………………………………..11
1.1.1. Planning and work breakdown structure (WBS)………….. 12
1.1.2. Cost analysis………………………………………………………………..14
1.2. General overview and background………………………...…………………. 17
1.2.1. Principles of SOFC………………………………………………………..17
1.2.2. Fuel Cell Performance ………………………………………..………..20
2. Development of a SOFC electrolyte with ESD technique…………………..…........25
2.1. Introduction and objectives……………………………………………………… 25
2.2. Development of an enhanced spray system……………………………......28
2.2.1. Spray stability…………………..…………………..………………………….…….29
2.2.1.1. Design requirements……………………………………………..…. 29
2.2.1.2. Experiment methodology…………………………………………. 32
2.2.1.3. Experiment results………………….……………..………………….34
2.2.2. Increasing the powder concentration of the suspension ………….39
2.2.2.1. Electrostatic stabilization.…………………..……………………..42
2.2.2.2. Steric stabilization…………………..………………………………...42
4. Master Project. Arturo Veiga López 4
3. SOFC Design, operation and results…………………………………..…………………….44
3.1. Design of the SOFC test station…………………..………………………….......44
3.1.1. Principles of design of the SOFC test station………………….44
3.1.2. Parts of the SOFC test station…………………..……………..…….45
3.2. Preparation of the experiment ……………………………………………….....54
3.2.1. Assembly process of the fuel cell …………………..…………......54
3.2.2. Experimental AC impedance procedure ……………..………...58
3.3 Results …………..…………………………..…………………………..……………..…..61
3.3.1. Open circuit potential …………..…………………………..…...…….61
3.3.2. Voltage and current curve (i-V) ……………..…………….……… 62
3.3.3. Electrochemical impedance spectroscopy ……………..……..65
4. Conclusion ..……………..………………………..………………………..…………………………68
References ……………..………………………..…………………………..…………………………………..….70
5. Master Project. Arturo Veiga López 5
List of figures
Figure 1.1. Work Breakdown Structure of the project (WBS).
Figure 1.2. Gant Chart of the project.
Figure 1.3. Schematic of a SOFC.
Figure 1.4. i-V curve with Tafel fitting .
Figure 1.5. Application of a voltage perturbation creates a current response
maintaining the linearity.
Figure 1.6. Physical sketch, equivalent circuit and Nyquist plot of an interface.
Figure 1.7. Physical sketch, equivalent circuit and Nyquist plot of an entire fuel cell.
Figure 2.1. Schematic of Sketch of the Electrostatic Spray Deposition technique.
Figure 2.2. Schematic of Coulomb force between two particles. Particles with the same
charge repel each other.
Figure 2.3. Electrostatic Spray Deposition System developed by He, 2013. Syringe and
pump (top left are connected to the nuzzle (top right). Note detail of heated substrate
(top right).
Figure 2.4. Improved spray system.
Figure 2.5. Types of spray based on distance to voltage combinations. Flow rate and
temperature used were 1ml/h and 230C, respectively. Note that four modes of spray
can be achieved: sputtering, squirt, cone jet, and dripping. Refer to text for an in depth
explanation of each mode.
Figure 2.6. Left: Cone Jet Spray: Ideal spray mode. Uniform spray guarantees best
results. Right: Cone Jet Spray deposition result. Note uniformity of deposit.
Figure 2.7. Different samples of YSZ sprayed onto a silicon substrate.
Figure 2.8. SEM micrograph of the sample obtained with a spray time of 30 min using
original spray system.
Figure 2.9. SEM micrograph of the sample obtained with a spray time of 30 min using
new spray system without vacuum.
Figure 2.10. SEM micrograph of the sample obtained with a spray time of 1 hour using
new spray system without vacuum.
6. Master Project. Arturo Veiga López 6
Figure 2.11. SEM micrograph of the sample obtained with a spray time of 14 hours
using new spray system without vacuum.
Figure 2.12. SEM micrograph of the sample obtained with a spray time of 14 hours
using new spray system without vacuum.
Figure 2.13. SEM micrograph of the sample obtained with a spray time of 17 hours
using new spray system without vacuum.
Figure 2.14. Schematic of forces that a particle is subjected to when in a fluid.
Gravitational and drag forces are opposite.
Figure 2.15. Schematic representation of potentials involved in a particle (surface
charge , Stern potential and Zeta potential).
Figure 2.16. Schematic representation of electrostatic stabilization.
Figure 2.17. Schematic representation of steric stabilization.
Figure 3.1. Schematic sketch the Solid Oxide Fuel Cell (SOFC) system and its parts.
Figure 3.2. Schematic of the hot temperature gas system.
Figure 3.3. Zirconia tube.
Figure 3.4. Anode-supported fuel cell characteristics model ASC-2.0.
Figure 3.5. Schematic of the assembly of the fuel cell.
Figure 3.6. SEM of silver wire in contact with Aremco Cement at 800C.
Figure 3.7. Composition of the surface of the Ag in contact with Aremco Cement at
800C.
Figure 3.8. SEM of silver wire near Aremco Cement at 800C.
Figure 3.9. Composition of the surface of the Ag near Aremco Cement at 800C.
Figure 3.10. Image of the Zirconia and inconel tubes with the furnace open.
Figure 3.11. Detailed view of the silver mesh impregnated with the ink and connected
to the wire.
Figure 3.12. Detailed view of the cathode side of the fuel cell mounted in the Zirconia
tube.
Figure 2.13. Final placement of the fuel cell before the test.
Figure 3.14. Curing curves for a layer of cement
Figure 3.15. Schematic of the two electrode connection diagram.
7. Master Project. Arturo Veiga López 7
Figure 3.16. Open circuit potential curve. At 800C and 97% H2 and 3% H2O.
Figure 3.17. i-V curve. At 800C and 97% H2 and 3% H2O.
Figure 3.18. Power density curve. At 800C and 97% H2 and 3% H2O.
Figure 3.19. Fuel cell performance curves. Fuel Cell Materials data sheet for model
ASC-2.0.
Figure 3.20. Results AC impedance spectrocopy. At 800C and 97% H2 and 3% H2O.
Figure 3.21. Equivalent circuit of the fuel cell.
Figure 3.22. Experimental results (red); Fitting results (green).
8. Master Project. Arturo Veiga López 8
List of symbols
ASI Specific Area Impedance
C Capacitance
Ethermo Thermodynamically predicted voltage of fuel cell.
EIS Electrochemical Impedance Spectroscopy
ESD Electrostatic Spray Deposition
Fd Drag force
Fg Gravity force
FC Fuel Cell
FRA Frequency Response Analyzer
g gravity
i-V Current-Voltage
OPC Open Circuit Potential
R Radious of the particle
R Resistance
Rf Faradic Resistance
RΩ Ohmic Resistance
SEM Scanning Electron Microscope
SOFC Solid Oxide Fuel Cell
V Settling velocity
V Voltage
Vp Volume of the particle
WBS Work Breakdown Structure
YSZ Yttria-stabilized Zirconia
Z Impedance
Zreal Real part of the Impedance
Zimag Imaginary part of the impedance
act Activation losses due to reaction kinetics.
ohmic Ohmic losses from ionic and electronic losses.
conc Concentration losses due to mass transport.
9. Master Project. Arturo Veiga López 9
µ Dynamic viscosity
ρf Fluid density
ρp Particle density
ω Frequency
10. Master Project. Arturo Veiga López 10
1. Abstract
The current project work focuses on the principles of fuel cells and the parameters
that measure the performance of a solid oxide fuel cell. The first two aims of the study
were to enhance the efficiency of the Electrostatic Spray Deposition (ESD) spray by
improving the spray stability. This can be achieved by increasing a more
homogeneous supply of particle by the ESD spray. Two main factors were studied; the
settling of the particles and the tendency of the particles to stick to the container
walls. The finished system was tested spraying layers of YSZ up to 14 hours and 70
microns of thickness. From our results we can conclude that this system is
appropriate to produce a stable spray system for YSZ and that the desired thickness
can be obtained varying the deposition time. The third aim of the study was to assess
the performance of a solid oxide fuel cell in order to improve its efficiency. For that, a
solid oxide fuel cell test station was designed and manufactured and the performance
of a commercially available fuel cell was evaluated. In conclusion, the fuel cell testing
system was validated and showed a fairly good approximation to the values provided
by the manufacturer, validating the functionality of the test station. Additional
improvements and research are warranted to achieve a fully reproducible and
commercially available solid oxide fuel cell.
11. Master Project. Arturo Veiga López 11
1. Introduction and background
1.1. Introduction
This project was part of the research focus of Professor Philip Nash and in collaboration with
Professor J. Robert Selman in the field of Solid Oxide Fuel Cells. The ultimate goal is to build a
Fuel Cell using the Electrostatic Spray Deposition technique in one step. The objective is to
achieve a sensible more efficient Fuel Cell in terms of electricity produced per unit of fuel, but
also developing a simple, low cost and scalable manufacturing process.
This research first started 2011 with the Master’s student Quanzhi He and I continued on the
project starting in September of 2012 as part of my research training during my Master in
Mechanical and Aerospace Engineering.
From my perspective this was a great opportunity to learn a new technology. The challenges
of this project were beyond the simply material science knowledge. This project combines
disciplines such as electrochemistry, material science, and fluid dynamics with nanoparticles.
This was a broad field that allowed to broaden my knowledge and challenged me every day.
Because most of the equipment used was design and build with the help of the faculty of the
Mechanical, Materials and Aerospace Engineering department, it also gave me the opportunity
of being part of designing and prototyping the equipment that will be used to perform those
tests and that will be used in the future by future colleagues.
12. Master Project. Arturo Veiga López 12
1.1.1. Planning and work breakdown structure (WBS)
This project was developed from September 2012 to October 2013 and was subjected to
changes of scope due to time and resource constraints, or due to unplanned challenges and
pitfalls along the process.
The following diagram shows the work breakdown structure of the project. In brief, the
structure has three components: The study of the Electrochemical Impedance Spectroscopy
(EIS) which is the technique that will be used for test the performance of a SOFC. The
Electrostatic Spray Deposition that is the technique used to build the SOFC and here a new
system was design build and tested. And the SOFC test station which is the system that checks
the performance of the SOFC, and here includes the design, build and test with a commercial
fuel cell.
3. SOFC2. ESD1. Study EIS
WBS
1.1. Principles
1.2. Test
with batteries
3.1. Design
Test station
3.2. Build
Test station
2.2. Build
New ESD system
2.3. Spray
YSZ
2.1. Design
New ESD system
3.3 Test
Commercial FC
Figure 1.1. Work Breakdown Structure of the project (WBS).
13. Master Project. Arturo Veiga López 13
A simplified Gant chart is showed in the figure 1.2. in order to give a basic time frame of the project and the activities executed during the
project.
Work breakdown
structure
2012 2013
9 10 11 12 1 2 3 4 5 6 7 8 9
EIS
Study principles FC
Study EIS technique
Battery tests
Equivalent circuit
Test
Station
Design
Build
Sealing Tests
Leakage repair
Improve system
ESD
Learn technique
Prototyping
Design final
Build final design
Repair Voltage control
Spray new system
SOFC
Test
Build test station
OCP
I-V
EIS
Write thesis
Figure 1.2. Gant Chart of the project.
14. Master Project. Arturo Veiga López 14
1.1.2. Cost analysis
The current project has been fully funded by Professor Philip Nash, and my advisor during
this project.
Although a detailed breakdown of all the costs involved in this project has not been
conducted, we have estimated that the total cost of the project is ~ $100,000. However, many
items are difficult to estimate, such as work hours, specialists consultation, amortization of
high specialized-equipment, software used, maintenance and hours of labor to build the
prototypes.
Only a fraction of the real cost of the project is shown here (see Tables 1.1 and 1.2), namely
the materials needed to build a test for a Solid Oxide Fuel Cell (SOFC) station and the
improved in the existing Electrostatic Spray Deposition (EDS) system. It important to consider
that also these materials are part of the ones used in other projects, specially the equipment
like the inductance oven and heaters for the SOFC test station. In the EDS system the High
Voltage power supply, syringe pump, and substrate heater were reused from other research
projects.
The following itemized list of materials is only to be used as a guide for the total cost of the
materials to facilitate a better understanding of the whole project.
15. Master Project. Arturo Veiga López 15
Table 1.1. New EDS system materials.
Line Quantity Product Unit Price Total Price
1 1 8486K545 Optically Clear Cast Acrylic Tube, 2-1/2" OD X 2" ID, 1' Length 34.94 34.94
2 10 9685T3 High-Pressure White Nylon Tubing, .15" ID, 1/4" OD, .05" Wall Thickness 0.85 8.5
3 3 5012K38 Acetal Quick-Disconnect Coupling, Socket, 1/8 Coupling, for 1/8" Tube ID 6.91 20.73
4 3 5012K46 Acetal Quick-Disconnect Coupling, Plug, 1/8 Coupling, 1/8" Male NPT 7.01 21.03
5 1 51525K221 Plastic Quick-Turn (Luer Lock) Coupling, Nylon, Male X Male Thread, 1/4" 5.25 5.25
6 2 2930T63 Type 316 Stainless Steel Wire Cloth Disc, 100 X 100 Mesh, 2-9/16" 6.45 12.9
7 1 9319T183 Super-Corrosion-Resistant 316 Stainless Steel, 100X100 Mesh 8.59 8.59
8 10 8359K14 High-Strength Clear Nylon Tubing, .190" ID, 1/4" OD, .030" Wall Thickness 0.36 3.6
9 1 8560K358 Optically Clear Cast Acrylic Sheet, 1/4" Thick, 6" X 6" 5.49 5.49
10 2 5392K11 Rigid White Polypropylene Tubing, 1/8" ID, 1/4" OD, 1/16" Wall Thickness 0.48 0.96
11 2 53945K111 Hard-Wall Rigid Clear PVC Tubing, .170" ID, 1/4" OD, .04" Wall Thickness 0.84 1.68
12 1 1901K11 Chemical-Resistant PVDF Tube Fitting, 90 Degree Elbow for 1/4" Tube OD 4.5 4.5
13 1 51055K984 White Acetal Instant Tube Fitting, 90 Degree Elbow for 1/4" Tube OD 2.73 2.73
14 1 8560K275 Optically Clear Cast Acrylic Sheet, 1/8" Thick, 6" X 12" 5.07 5.07
15 1 8547K62 Tube Made of Teflon(R) PTFE, 1/2" OD X 5/16" ID, 1' Length 7.89 7.89
16 3 5128A62 Low-Profile Hold-Down Toggle Clamp, Standard, Steel 8.58 25.74
17 1 8486K555 Optically Clear Cast Acrylic Tube, 3" OD X 2-1/2" ID, 1' Length 35.73 35.73
18 2 5678K111 Magnetic Stirring Bar, Ocatagonal, 1/2" Length, 5/16" OD 3.96 7.92
19 2 5678K112 Magnetic Stirring Bar, Octagonal, 5/8" Length, 5/16" OD 4.41 8.82
20 5 52705K31 Ultra-Clear PFA Tubing, 1/16" ID, 1/8" OD, 1/32" Wall Thickness, Clear 1.52 7.6
21 1 91772A165 18-8 Stainless Steel Pan Head Phillips Machine Screw, 6-32 Thread 6.66 6.66
22 1 9545K27 Push-in Tapered Round Rubber Plug, Through Hole 8.33 8.33
23 1 9545K18 Push-in Tapered Round Rubber Plug, Solid, Size 6, Fits 1-1/4" 15.91 15.91
260.57TOTAL
New ESD System
16. Master Project. Arturo Veiga López 16
Table 1.2. SOFC test station materials.
Line Quantity Product Description Unit Price Total Price
1 1 4757K61 Miniature PVC Ball Valve Diverting, 3-Port, Push-to-Connect 20.61$ 20.61$
2 50 5195T64 Water-Resistant Clear Polyurethane Tubing 3/16" 0.39$ 19.50$
3 1 89495K151 Stainless Steel Round Tube Type 304, 3" OD, 2-1/2" 90.05$ 90.05$
4 2 5182K256 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/4" Tube NPT 19.23$ 38.46$
5 2 50775K403 Tube Support for 1/4" Tube ID Durable Nylon Compression Tube Fitting 6.09$ 12.18$
6 1 6811A22 Super-High Temperature Wrap for Wire and Cable Protection 5.16$ 5.16$
7 30 5195T64 Water-Resistant Clear Polyurethane Tubing 3/16" ID, 1/4" OD 0.39$ 11.70$
8 1 89495K151 Stainless Steel Round Tube Type 304, 3" OD, 2-1/2" 90.05$ 90.05$
9 1 50775K403 Tube Support for 1/4" Tube OD Durable Nylon Compression Tube Fitting 6.09$ 6.09$
10 1 4093T21 Diverting 3-Port Brass Ball Valve Any-Direction, 1/4" NPT Female 41.64$ 41.64$
11 1 92001A291 18-8 Stainless Steel Wing Nut 8-32 Thread Size, 29/32" Wing Spread 6.58$ 6.58$
12 1 92141A011 18-8 SS General Purpose Flat Washer NO. 10 Screw Size, 7/16" OD 2.33$ 2.33$
13 2 47065T142 Std Zinc-Plated STL End-Feed Fastener, for 1" Aluminum Inch T-Slotted 2.30$ 4.60$
14 1 87175K93 NON-Porous High Alumina Ceramic Tube 4 Bore, .188" OD 27.88$ 27.88$
15 1 5182K269 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/2" NPT Female Pipe 20.04$ 20.04$
16 1 87175K91 NON-Porous High Alumina Ceramic Tube 4 Bore, .188" OD 20.91$ 20.91$
17 1 92001A291 18-8 Stainless Steel Wing Nut 8-32 Thread Size, 29/32" Wing Spread 6.58$ 6.58$
18 1 92141A011 18-8 SS General Purpose Flat Washer NO. 10 Screw Size, 7/16" OD 2.33$ 2.33$
19 2 47065T142 Std Zinc-Plated STL End-Feed Fastener, for 1" Aluminum Inch T-Slotted 2.30$ 4.60$
20 1 5182K269 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/2" Tube OD X 1/4" NPT 20.04$ 20.04$
21 1 9922K121 Corrosion-Resistant Steel Tubing 1/4" OD, .18" ID 18.97$ 18.97$
22 3 5182K577 Type 316 SS Yor-Lok Tube Fitting Front and back Sleeve for 1/2" Tube OD 4.50$ 13.50$
24 3 5182K557 Type 316 SS Yor-Lok Tube Fitting Nut for 1/2" Tube OD 5.25$ 15.75$
25 1 5182K129 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/2" NPT Male Pipe 16.32$ 16.32$
26 1 5182K269 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/2" NPT Female Pipe 20.04$ 20.04$
27 2 47065T206 Aluminum Inch T-Slotted Framing System Single Horiz Tube Holder 36.12$ 72.24$
28 1 47065T101 Aluminum Inch T-Slotted Framing System Four-Slot Single 14.20$ 14.20$
29 8 47065T223 Aluminum Inch T-Slotted Framing System 90 Degree Bracket 3.98$ 31.84$
30 1 9657K302 Steel Compression Spring Zinc-Pltd Music Wire, 1.00" L,.300" OD 9.80$ 9.80$
31 1 91792A209 18-8 SS Pan Head Slotted Machine Screw 8-32 Thread, 3" Length 7.01$ 7.01$
32 1 9435K43 302 SS Precision Compression Spring 1.0" Length, .24" OD, 5.02$ 5.02$
33 1 9246K11 Multipurpose Aluminum (Alloy 6061) 1/4" Thick, 8" X 8" 17.38$ 17.38$
34 1 8746K541 NON-Porous High-Alumina Ceramic Tube .875" OD, 5/8" ID, 12" Length 67.60$ 67.60$
35 1 8746K542 NON-Porous High-Alumina Ceramic Tube .875" OD, 5/8" ID, 24" Length 122.90$ 122.90$
36 1 9396K104 Silicone O-Ring AS568A Dash Number 020, Packs of 25 5.27$ 5.27$
37 4 3854T81 Clear Plastic Petri Dish with Cover, 3-1/2" Diameter, 5/8" Height 6.62$ 26.48$
38 1 5943K232 Cleaned and Bagged Yor-Lok SS Tube Fitting Branch Tee for 1/2" NPT 56.42$ 56.42$
39 3 5182K755 Type 316 SS Yor-Lok Tube Fitting Tube Stem Reducing Cplg for 1/2" 13.33$ 39.99$
40 5 5182K574 Type 316 SS Yor-Lok Tube Fitting Front & Back Sleeve for 1/4" Tube OD 2.56$ 12.80$
42 1 5182K242 Type 316 SS Yor-Lok Tube Fitting Reducing Coupling for 1/4" 15.90$ 15.90$
43 6 2572K26 Load-Rated Bumper Polyurethane, Med-Hard, 1/4" 7.94$ 47.64$
44 3 5182K577 Type 316 SS Yor-Lok Tube Fitting Front & Back Sleeve for 1/2" Tube OD 4.50$ 13.50$
46 3 5182K557 Type 316 SS Yor-Lok Tube Fitting Nut for 1/2" Tube OD 5.25$ 15.75$
47 1 5182K129 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/2" NPT Male Pipe 16.32$ 16.32$
48 1 5182K269 Type 316 SS Yor-Lok Tube Fitting Adapter for 1/2" NPT Female Pipe 20.04$ 20.04$
49 1 SSR330DC10 Solid State Relay 21.00$ 21.00$
50 3 TJ50 Thermocuple TJ50-CAIN-14U-6-SB-OSTW-M 51.25$ 153.75$
51 1 TJ70 Thermocouple TJ70-CAIN-116U-30-SB-OSTW-M 51.45$ 51.45$
52 1 TJ50 Thermocouple TJ50-CAIN-116U-12-SB-OSTW-M 43.25$ 43.25$
53 1 INC-12-30OPEN Miniature protection tube INC-12-30OPEN 28.70$ 28.70$
54 1 AG-M40-100 Silver mesh 205.00$ 205.00$
55 1 Ag-I Silver ink 95.00$ 95.00$
56 1 ASC-2.0 Anode supported fuel cell 155.00$ 155.00$
57 1 C-885 Zr-based Cement - Ceramabond 885 93.00$ 93.00$
2,000.16$TOTAL
Test Station
17. Master Project. Arturo Veiga López 17
1.2. General overview and background
1.2.1. Principles of SOFC
A Fuel Cell is a device that transforms the chemical energy of a fuel into electric
current through an electrochemical process. It was first discovered in 1839 by Sir
William Grove.
The focus of this project is the Solid Oxide Fuel Cell (SOFC, see figure 1.3. for details),
one of many types of fuel cells. This fuel cell is in solid state in its operation and it is
made with special ceramics with key characteristics that will be covered in the
current chapter.
All fuel cells have 3 main parts: an anode, a cathode and the electrolyte, which is the
layer in between. Both anode and cathode have to be electric conductors in contrast
with the electrolyte that should be an insulator. The electrolyte is made by a material
that allows the anions of Oxygen (O2-) to go through, but at the same time, forces the
electrons to circulate through the electric circuit producing a current that powers it.
18. Master Project. Arturo Veiga López 18
Figure 1.3. Schematic of a SOFC.
The electrolyte used for the SOFC is made of 8mol% Yttria-stabilized Zirconia
(Y2O3 Fully Stabilized ZrO2), which is the most common electrolyte material in SOFC.
The electrolyte main requirement is that it has to conduct the Oxygen anions and at
the same time it has to be an electrical insulator. The ionic movement occurs through
the crystal lattice. This phenomenon is thermally activated so it has to be heated to a
temperature of 800 C. This is the biggest challenge in this type of Fuel Cell and most
of the research is focused in attempting to lower this temperature by making several
layers between the anode/cathode and the electrolyte, using other materials, or like in
this research project, lowering the electrolyte thickness.
Fuel = H2
H2O
Air = O2
Anode Cathode
Electrolyte
O2-
e-
e-
19. Master Project. Arturo Veiga López 19
The anode is made of Nickel Ytttria-stabilized Zirconia (Ni/YSZ). Here is where the
fuel is oxidized to produce H2O. The main characteristics of a good anode are:
Good Hydrogen catalyst
Large specific area, commonly is a porous material
Good electronic conductor
The reaction that takes place in the anode is:
The cathode is made of Lanthanum Strontium Manganite (LSM). Here is where the
Oxygen molecule breaks down and the result atoms are ionized. The main
characteristics of a good anode are:
Good Oxygen catalyst
Large specific area normally is a porous material
Good electronic conductor
The reaction that takes place in the cathode is:
Both anode and cathode reactions combine lead us to the overall reaction:
There are also other requirements for all of these 3 materials like thermal stability,
same expansion coefficient, chemical compatibility but that goes further out of the
scope of this introductory chapter.
The main advantages of this type of fuel cell is its great efficiency, theoretically up to
60%, and that it can be a good candidate for a combined heat and power application
that could increase it further.
20. Master Project. Arturo Veiga López 20
1.2.2. Fuel Cell Performance
The performance of a fuel cell is measured by identifying and calculating the losses
that lowers the potential from the thermodynamic ideal case. One of the objectives of
to test the fuel cell and for that a test station needs to be built.
General losses
In a fuel cell there are several losses that lower its thermodynamic potential.
Where:
V: Operating voltage.
Ethermo: Thermodynamically predicted voltage of fuel cell.
act: Activation losses due to reaction kinetics.
ohmic: Ohmic losses from ionic and electronic losses.
conc: Concentration losses due to mass transport.
For measuring the performance of a fuel cell basically 2 tests are needed: The i-V
curve and the Electrochemical Impedance Spectroscopy (EIS).
The current voltage curve (i-V)
The i-V curve is a curve that shows the potential at different current densities. From
the curve itself the losses can not be determined, but using the Tafel equation it can be
identified the activation loss and the Ohmic and concentration loss (see Figure 1.4).
21. Master Project. Arturo Veiga López 21
Activation loss
Ohmic +
concentration loss
Voltage
Current density
i-V curve
Tafel fitting
Figure 1.4. i-V curve with Tafel fitting .
Electrochemical Impedance Spectroscopy.
The other test that helps us to evaluate the performance of the Fuel Cell is the
Electrochemical Impedance Spectroscopy (EIS). This technique allows us to
differentiate the majority of sources of loss in a Fuel Cell.
The EIS principles are based on measuring the impedance of the Fuel Cell when a
small AC voltage perturbation superposes to the DC voltage of the polarization applied
to the cell.
This perturbation needs to be small enough for the i-V curve to be pseudolinear, but
large enough to yield a current response that can be measured (see Figure 1.5.).
22. Master Project. Arturo Veiga López 22
Voltage
Current density
Voltage
perturbation
Creates current
response
Pseudolinear
portion of i-V curve
Figure 1.5. Application of a voltage perturbation creates a current response
maintaining the linearity.
The impedance measured with this technique and at different frequencies is plotted in
a Nyquist diagram like in the bottom of the figure 1.6.
An electrochemical reaction can be represented by a resistor and a capacitor in
parallel. The resistor reflects the Faradic resistance, while the capacitor reflects the
capacitive nature of the interface due to the charge separation between 2 layers.
23. Master Project. Arturo Veiga López 23
C1
CathodeElectrolyte
↓ ω
-Zimag
Zreal
Rf,1
Rf,1
Figure 1.6. Physical sketch, equivalent circuit and Nyquist plot of an interface.
As shown in figure 1.6., the diameter of the circle reflects the resistance. The
capacitance can be calculated from the following equation:
In an equivalent circuit of a fuel cell there are 2 interfaces, anode-electrolyte and cathode
electrolyte and an Ohmic resistance that is mainly due to the resistance that the anions have
to go through the electrolyte. This equivalent circuit is shown in the figure 1.7.
25. Master Project. Arturo Veiga López 25
2. Development of a SOFC electrolyte with ESD technique
2.1. Introduction and Objectives
The current section will briefly describe the rationale behind the selection of the
Electrostatic Spray Deposition (ESD) technique to build a Solid Oxide Fuel Cell and the
basic concepts of this methodology.
Based on the results of the Thesis called “Electrostatic spray deposition of Solid Oxide
Fuel Cell electrolyte” [He, 2013] it is feasible to achieve a 100% dense YSZ layer using
the ESD technique. Moreover, the control of the porosity of the sprayed layer with
other materials provides with the opportunity to build an anode and cathode with the
same technique, which should be porous to maximize the surface in contact with the
gases in the fuel cell. However, this is not without challenges. We will cover those
challenges and how to overcome them in the following sections.
The overall objective of these experiments is to advance the knowledge of the
properties of the sprayed layer and to face the challenges in long-time sprays and
other materials. The ultimate goal of this research is the development of a complete
fuel cell with the solely use of the ESD technique in several steps of spray and sinter
the several layers of a fuel cell.
ESD is essentially a coating technique that uses a liquid to create a suspension where
nanoparticles of the material which we want to coat our surface with are dissolved
into (see Figure 2.1. for details).
26. Master Project. Arturo Veiga López 26
Figure 2.1. Schematic of Sketch of the Electrostatic Spray Deposition technique.
An ESD system consists of a suspension system with a syringe pump and a nozzle, a
high voltage generator, and a heated substrate. The suspension is sprayed onto a
substrate using a high electric field (8 kV – 13 kV) between the nuzzle (where the
suspension is pumped) and the substrate. The substrate is heated to a certain
temperature that helps evaporate the excess of liquid in the flight time of those drops.
Flight time refers to the time that elapses between the time that the suspension leaves
the heated surface and that it reaches the nuzzle. The remaining of the liquid
evaporates in contact with the substrate allowing a slight movement of the particles in
the substrate. This helps to achieve a more uniform layer.
The electric field charge the drops when they go through the nuzzle (that drives the
particles to stick to the substrate), but also this charge is responsible for the Columbus
Film
Drops
Flow:1ml/h
Voltage
8-13 kV
Nuzzle
Heatedsubstrate
27. Master Project. Arturo Veiga López 27
force that prevents agglomeration between them. As a result they form a uniform
layer (see Figure 2.2.).
Figure 2.2. Schematic of Coulomb force between two particles. Particles with the same
charge repel each other.
The system developed by He, 2013 is shown on Figure 2.3. This system requires a
series of improvements to enhance robustness and reproducibility of the
methodology, which will be the focus of this work.
The main advantage of this technique is that it not only provides with the opportunity
to create a thin film (as thin as 1 µm), but that it also allows with a high control over
the porosity of the layer. Other advantages include the low equipment cost and the
easy scalability for manufacturing. Overall, this technique is highly competitive over
others, such as physical vapor deposition, screen printing, or slurry coating.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Drop
YSZ particles
28. Master Project. Arturo Veiga López 28
Figure 2.3. Electrostatic Spray Deposition System developed by He, 2013. Syringe and
pump (top left are connected to the nuzzle (top right). Note detail of heated substrate
(top right).
2.2. Development of an enhanced spray system
The former system developed by He, 2013 although innovative, lacked of the
repeatability and robustness required. One of the main challenges with this system is
that the ESD technique is very slow, which in turns leads to a high variability of the
final outcome. The amount of suspension sprayed is about 1 ml per hour, with an
average of 3 µm per hour. Assuming the final anode thickness should be over 100
microns, this speed of growth to generate the layer is too slow and requires a very
long spraying phase (up to 30 hours).
Nuzzle Heatedsubstrate
Syringe +
pump
29. Master Project. Arturo Veiga López 29
Maintaining the spray constant and stable for this amount of time is quite difficult due
to the sensitivity of the technique. Note that any change on the suspension or the
ambient conditions can change the spray behavior. Therefore, it is essential to 1)
achieve complete spray stability (described in section 2.2.1.) and 2) reduce the spray
time (described in section 2.2.2.).
To achieve complete spray stability, a new design and improvements to the system
have been implemented.
To reduce the spray time, the flow rate and/or the powder concentration in the
suspension need to be evaluated. These improvements are studied in detail in this
chapter.
2.2.1. Spray stability
2.2.1.1. Design requirements
To achieve a complete spray stability and repeatability we identified the underlying
causes that may affect the spray behavior. It was determined by experimental
observation that the main problem for having a stable spray was the supply to the
spray with a constant concentration of particles. Two critical factors of the design
were responsible for the heterogeneous supply of particles, namely the settling of the
particles and the tendency of the particles to stick to the container walls. These will be
covered in the next sections.
Settling of the particles
Settling refers to the process by which particles settle on the bottom of a liquid and
form a sediment. The main problem is the settling of particles due to the different
density between the YSZ nanopowders and the liquid where those particles are
30. Master Project. Arturo Veiga López 30
dissolved. Later in this chapter we will study if it is possible to modify the suspension
itself to prevent this settling phenomenon. In this section, we will discuss how to
minimize this effect by solely improving the design.
We also observed that the particles have a tendency to stick to the walls of the tubes.
The solution proposed and tested is to incorporate a reservoir as close to the nuzzle as
possible. This will allow to have the highest amount of suspension next to the nuzzle.
We also implemented a magnetic stirring system in it so we can stir the suspension at
the same time that spraying is occurring. This will minimize the tendency of the
particles to stick to the container walls by increasing the ratio volume/area and
assuring that the suspension sprayed is not in contact with any tubes before is being
sprayed. This solution was tested through different prototypes before the
implementation into the final design.
The magnetic stirring system has to be capable to operate at a very low speed (~ 90
rpm). To achieve this speed, the voltage and frequency regulator has to be connected
in series with a dimmer that “cuts” part of the AC current in each cycle. This was a fast
and very cost effective solution to lower the speed of the stirring motor.
Another possible approach could be the implementation of an ultrasound system that
constantly induces a vibration on the particles that theoretically prevents the
agglomeration that causes the settling. This could be a solution not only for the
reservoir, but also for the syringe and the remaining tubes. It was not incorporated in
this design because of its complexity, but it is a solution worth exploring in future
design improvements.
Vacuum
A vacuum can be created during the spray phase and that can affect the stability when
spraying occurs during a long period of time. To solve this problem, a tube open to the
air was attached in the top part of the container.
31. Master Project. Arturo Veiga López 31
With this tube we cannot apply a pressure to the system so the flow rate will be only
imposed by the electric field and not by the syringe. That also poses the following
challenge; to maintain the suspension level by guessing the flow rate sprayed. Because
of this phenomena and the poor results obtained trying to prevent this vacuum, this
system was not implemented.
Electric field
Another problem that directly affects the spray stability is the uniformity of the
electric field. The electric field is the driving force of the spray; any distortion of the
electric field affects directly shape of the spray. This represents a complex challenge,
because the electric permittivity is directed affected by the concentration,
distribution, and nature of the particles sprayed. In the original design [He, 2013], a
plastic disk was placed in the middle of the nuzzle. This disk allows to concentrate the
electric field in the upper part of the nuzzle, that is a perfect cylinder, blocking the rest
of the possible electric field of the rest of the nuzzle.
To improve this approach a grounded Faraday cage was built to ensure the electric
field, that comes from any other part that is not the last 0.5 inches of the nuzzle, is
cancelled.
All of the above descried systems were designed and built specifically for this project
(see improved design in Figure 2.4.). They were made as compact as possible and met
the requirements and needs of material compatibility. The system adapted the design
of the original design [He, 2013] in terms of the chamber, the positioning, and the
heating system. The design was developed using the software PRO-E a CAD software.
32. Master Project. Arturo Veiga López 32
Figure 2.4. Improved spray system.
2.2.1.2. Experiment methodology
Several experiments were made to spray a YSZ layer with different thicknesses. The
results were observed in the SEM to evaluate the microstructure of the deposited
layer. The parameters controlled during the experiment were: voltage, distance, flow
rate, and temperature of the substrate.
To get a stable spray, and based on previous experiments, the flow rate was set to 1
ml/h. The temperature is a critical parameter to achieve a completely dense layer and
it was set at 250 C.
33. Master Project. Arturo Veiga López 33
To achieve a good spray shape, the combination of distance and voltage is essential.
This spray mode is called cone-jet and it is the operation mode that allows to have a
perfect and uniform layer. To determine these parameters it is needed to calibrate
using different distances and voltages. Figure 2.5. represents the relationship between
these two parameters and the type of spray that will provide with.
Figure 2.5. Types of spray based on distance to voltage combinations. Flow rate and
temperature used were 1 ml/h and 230C, respectively. Note that four modes of spray
can be achieved: sputtering, squirt, cone jet, and dripping. Refer to text for an in depth
explanation of each mode.
Four modes of spray can be achieved based on the distance to voltage relationship:
1) Sputtering: This mode occurs when the voltage is very high in relationship to
the distance. In this case, multiple sprays come out of the nuzzle and cannot be
easily controlled.
2) Squirt: This mode produces a single spray, but it is not uniform. The center of
the spray has more drops, that cause a little hill in the middle of the deposited
layer.
34. Master Project. Arturo Veiga López 34
3) Cone Jet: This is the ideal mode of spray; it is completely uniform and best
results are achieved when formed (Figure 2.6.).
4) Dripping: In this mode, the voltage is too low for the selected distance and
instead of having a continuous spray, only drops are formed.
Figure 2.6. Left: Cone Jet Spray: Ideal spray mode. Uniform spray guarantees best
results. Right: Cone Jet Spray deposition result. Note uniformity of deposit.
2.2.3. Experiment results
A series of experiments were conducted to test the spray stability. SEM technique was
used to compare results with the previous system and to achieve sprays for up to 17
hours and evaluate its microstructure.
In Figure 2.7. different YSZ samples sprayed onto a silicon substrate are shown. The
different of color within each half of each sample is due to the fact that a more obscure
side was sintered.
35. Master Project. Arturo Veiga López 35
Figure 2.7. Different samples of YSZ sprayed onto a silicon substrate.
To evaluate the results in terms of density and uniformity after the sinterization, the
samples obtained were compared to the original system [He, 2013]. Figure 2.8. shows
a SEM micrograph obtained after the use of the original system. Some pores are
evident, but most of them will disappear with the sinter process.
36. Master Project. Arturo Veiga López 36
Figure 2.8. SEM micrograph of the sample obtained with a spray time of 30 min using
original spray system.
The new spray system without the vacuum was tested using the following conditions:
Flow rate: 1 ml/h
Concentration of YSZ in the suspension: 1 wt %
Solvent of the suspension: Butyl Carbitol
Temperature of the substrate 230 C
The voltage and distance were adjusted to achieve the best possible Cone Jet
Figure 2.9. SEM micrograph of the sample obtained with a spray time of 30 min using
new spray system without vacuum.
37. Master Project. Arturo Veiga López 37
Figure 2.10. SEM micrograph of the sample obtained with a spray time of 1 hour using
new spray system without vacuum.
Thickness of the layer is proportional to the time (thicker in 1 hour vs. 30 min
exposure) as the rest of parameters remain constant. We can notice that there is still
some porosity, but it has improved compared to the original system design. Longer
exposure times, up to 17 hours were tested (see Figures 2.11. and 2.12.).
Figure 2.11. SEM micrograph of the sample obtained with a spray time of 14 hours
using new spray system without vacuum.
38. Master Project. Arturo Veiga López 38
Figure 2.12. SEM micrograph of the sample obtained with a spray time of 14 hours
using new spray system without vacuum.
As seen in the micrographs after 14 of exposure (Figures 2.11. and 2.12.)one can
obtain a layer of up to 69 microns and with good properties. The cracks along the
surface are caused by the cutting process, since the layer is too thick to have a perfect
cross section.
The above described experiments were performed without the vacuum tube that will
theoretically allow the achievement of a more stable spray. The type of spray achieved
is slightly of squirt mode, as shown in Figure 2.13., the center has more particles
sprayed than on the sides.
39. Master Project. Arturo Veiga López 39
Figure 2.13. SEM micrograph of the sample obtained with a spray time of 17 hours
using new spray system without vacuum.
We can conclude that this system is appropriate to produce a stable spray system for
YSZ and to achieve the desired thickness varying the deposition time.
2.2.2. Increasing the powder concentration of the suspension
As mentioned earlier, reducing the spray time is critical to achieve a complete stable
spray. Changes in the composition of the actual suspension will allow to produce a
thicker layer in less time.
In order to limit the particle settling it is needed to understand the principles that
regulate the particles settling. A particle suspended in a fluid is subjected to two
applied forces, gravity and drag. The drag force is a function of the particle velocity, so
when the gravity accelerates the particle, its velocity increases until both forces are
equal. This is called the terminal velocity. The terminal velocity is affected by
numerous parameters like the shape, size of the particles, the density, and viscosity of
the fluid.
Figure 2.14. Schematic of forces that a particle is subjected to when in a fluid.
Gravitational and drag forces are opposite.
40. Master Project. Arturo Veiga López 40
We assume that there is a smooth spherical particle in a fluid, hence no interferences
among particles. Based on the Reynolds number we can have 3 different scenarios:
Stokes drag
Newtonian drag
Transitional drag
In this case, and due to the small particles involved, the Reynolds number is very
small. This indicates that the main dragging force is due to the viscous forces.
Applied force (gravity)
Where:
ρp : Particle density
ρf : Fluid density
g: gravity
Vp: Volume of the particle
Drag force
Where:
µ: dynamic viscosity of the fluid (6 Pa*s)
R: radius of the particle (20 nm)
v: settling velocity
Then:
ρ
For our suspension, the velocity is 2.7∙10-3 mm/h which is equivalent to ~ 1 mm/year.
Theoretically, with this particle size (20 nm), the suspension should remain stable for
years. But, experimentally, it is observed that the suspension settles within hours.
41. Master Project. Arturo Veiga López 41
That observation leads to the assumption that the particles agglomerate to produce
much bigger particles in the order of magnitude of 10 microns.
Also, another phenomenon that was observed is that with the time, even if we agitate
the suspension every hour the velocity of settling is higher. That means that the
particles are agglomerating and even after an agitation process they still remain
together, making the settling faster. Two methods are available to avoid the
agglomeration phenomenon, electrostatic stabilization and steric stabilization.
Before explaining those two methods, it is important to review that particles may
carry electrical charges in their surfaces, which in this case is the main factor of
agglomeration (electric charge). There are three types of potential involved in a
particle (surface charge, Stern potential and Zeta potential), and each of them is
predominant in a specific region around the particle. We will focus on the Zeta
potential, which is the one that drives the agglomeration of small particles. Zeta
potential is defined as the potential difference between the dispersion medium and
the stationary layer of fluid near a single particle.
Figure 2.15. Schematic representation of potentials involved in a particle (surface
charge, Stern potential, and Zeta potential).
42. Master Project. Arturo Veiga López 42
2.2.2.1. Electrostatic stabilization
This method is based in changing the zeta potential of the suspension. If the zeta
potential is greater than +30 mV or smaller than -30 mV, the agglomeration is
avoided. It is important to remember that the settling time for nanoparticles is in the
range of years. To change the zeta potential, the most common method is to change
the pH of the suspension to increase or decrease the zeta potential of the particle in
the medium.
This method works better in mediums that have a high electric dielectric constant.
The solvent used to spray YSZ is Diethylene Glycol Monomethyl and has a dielectric
constant of 10.15, which makes it not very suitable, but possible.
Figure 2.16. Schematic representation of electrostatic stabilization.
2.2.2.2. Steric stabilization
Another approach is to use a polymer chain that sticks to the surface of the particles
using the electric charge of the particles. The chains of the polymer interact among
them before the particles are close enough to be attracted by electrostatic forces. It is
43. Master Project. Arturo Veiga López 43
required that the medium may be a good solvent for the polymer chain. In addition,
the charge of these polymers has to be opposite to the zeta potential of the particles.
Figure 2.17. Schematic representation of steric stabilization.
In order to use these methods the zeta potential of the particles used in the medium
needs to be determined experimentally. The equipment required to determined the
zeta potential of these particles is highly specialized and currently will not represent a
cost-effective measure to implement.
Theoretically, the improvement on the amount of particles is limited by the viscosity,
from the suspension point of view, apart other factors that should be tested
experimentally like the stability of the spray, which can be up to 30 % of volume of
powders. That allows to work with 70 wt % of powders in a stable suspension, which
is 70 times higher than the actual powder concentration.
There are other factors involved that have the potential to reduce the powder
concentration. It is likely that the spray system cannot operate with such amount of
powder concentration, but the current limitation factor (the suspension) will not be a
problem in the future, so there is potential for improvement by increasing the powder
concentration. This means that this technique can be accelerated to achieve same
thickness in a fraction of the time required.
44. Master Project. Arturo Veiga López 44
3. SOFC Design, operation and results
3.1. Design of the SOFC test station
In order to assess the performance of a Solid Oxide Fuel Cell (SOFC), a test station was
built. This chapter is going to focus on the design and manufacture of the test station
and on the evaluation of the performance of the fuel cell.
3.1.1. Principles of design of the SOFC test station
The fuel cell design is based on a traditional test equipment for SOFC button cells
using a cylindrical induction furnace to achieve the operation temperature using a
Zirconia tube as support for the SOFC. Some critical factors were to be taken into
account to design this test station:
Working temperature: 800 C.
Fragility of the materials used to build the SOFC and the SOFC per se.
Minimize the difference among the expansion coefficients of the materials used.
Achieve a 100 % seal system due to the nature of the gases and temperatures
involved.
Minimize the electric interferences from the furnace.
Among these factors, the high temperature (~ 800 C) is the most important design
factor to take into account.
The fuel cell (see Figure 3.1. for detailed design) has to not only provide with both fuel
and air in the necessary conditions, but has also to control the temperature of system,
collect the current and voltage, and process them.
45. Master Project. Arturo Veiga López 45
Figure 3.1. Schematic sketch of a Solid Oxide Fuel Cell (SOFC) system and its parts.
3.1.2. Parts of the SOFC test station
The test station can be divided up into several subsystems that include the following:
Low temperature gas system
The furnace and the temperature control system
The hot temperature gas system
SOFC button cell
The AC impedance system
Gas Valve
N2
H2
Heated
water bath
To the
outside
Lowtemperature gas system
Hot temperature gas system
Lowtemperature gas system
Blower
AC impedance system
Potentiostat /
Freq. Response Analyser
Ag wires
Zirconia
tubes
46. Master Project. Arturo Veiga López 46
Electrical insulator
Sealing
Low temperature gas system
This system includes the bottles of Hydrogen and Nitrogen and runs up to the
entrance of the Zirconia tube system. The gas control system (Diavac 885, Leybold)
has the flow meters and valves to adjust the flow of the gas to perform the test.
The incoming gas is bubbled into a 500 ml flask with three openings, two for the gas
and one for the thermocouple that will register its temperature. This flask
incorporates a heater (Omega LHM0500) that allows to increase the humidity of the
gas, until the saturation point at any given temperature. This is especially important
because the level of humidity of the gas (saturated of water) depends on the
temperature of the gas. The heater is controlled by the same system as the furnace. It
is important to keep the distance between the flask and the entrance of the Zirconia
tube as short as possible, in order to prevent condensation in the tube. Otherwise, the
gas may be less humid than what it should be.
Once the gases pass through the hot gas system, the exhausted gases are bubbled
through another device, which induces a little over pressure into the system. Its
function is to check the presence of leakages throughout the experiment and to
provide with a steady flow along the process. Finally, the gases are safely extracted to
the exterior of the building.
The furnace and the temperature control system
The furnace is based on a cylindrical furnace (ATS series 3210) with a maximum
output of 4,010 W and a series of three thermocouples (model Omega TJ50)
connected to a digital controller (model Omega Multizone controller), that allows to
control and maintain the needed temperature in the furnace.
47. Master Project. Arturo Veiga López 47
The hot temperature gas system
The hot temperature gas system (see Figure 3.2.) is made of two Zirconia tubes (see
Figure 3.3.) and one inconel tube that is placed inside one of the Zirconia tubes and
the connection system required to connect all three tubes to the low temperature gas
system.
Figure 3.2. Schematic of the hot temperature gas system.
Air
H2 N2
H2O
N2
H2O
N2
Oven
Ag wires
To potentiostat
Inconel tube
Stainless
steel tube
Alumina tube
Alumina tube
Inconel tube
48. Master Project. Arturo Veiga López 48
Figure 3.3. Zirconia tube.
The gases go through the inconel tube that ends in the fuel cell where the gases react
with the SOFC. The products of this reaction go through the space in between the
Zirconia and the inconel tube. Knowing the temperature close to the fuel cell is critical,
because is this will be the operating temperature, which drives the ion mobility
through the YSZ. To measure the temperature, a thermocouple TJ70-CAIN was placed
inside the Zirconia tube and as close as possible to the fuel cell.
The structure to hold the Zirconia tube was made using an extrusion aluminum frame,
commonly used in this type of constructions because of its great flexibility and
robustness.
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SOFC button cell
The button cell used is the model ASC-2.0, an anode supported cell supplied by fuel
cell materials with the Ni-YSZ/YSZ/LSM structure (20 mm of diameter). Other details
of the cell are the following: a 10 μm thick YSZ electrolyte, LSM as cathode with a
thickness of 50μm and NiO-YSZ anode with 220-260μm of thickness (see Figure 3.4.
for details). Both anode and cathode are porous to increase the reactive area surface
with the gases. This type of fuel cell requires a reduction of the anode before use.
Specifics of the assembly of the button fuel cell are shown in Figure 3.5.
Figure 3.4. Anode-supported fuel cell characteristics model ASC-2.0.
Cathode
Electrolyte
Anode
50. Master Project. Arturo Veiga López 50
Figure 3.5. Schematic of the assembly of the fuel cell.
The AC impedance system
The system used to analyze the AC impedance data is the PARSTAT 4000, Princeton
Applied Research, a potentiostat / galvanostat coupled with a frequency response
analyzer (FRA) contained in a single unit. The impedance system is connected and
controlled a computer using the VersaStudio electrochemistry software that allows
the design of the experiments and the analysis of the data obtained. Silver mesh and
wires (silver wire diameter: 0.25 mm) are used to the transport of the voltage and
current to be analyzed. Note that when using this of equipment at these temperatures,
platinum is the ideal element of choice because it has a melting point much higher
than the silver (Ag: 961 C vs. Pt: 963 C).
To test the integrity of the silver under experimental conditions, an experiment was
conducted to determine if degradation in the silver may affect the results. The
integrity of the silver wire was evaluated by analyzing the structure and composition
of the silver wire (see Figures 3.6. to 3.9).
Ag wires
Cement
Cathode
Ag mesh
(current collector)
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Figure 3.6. SEM of silver wire in contact with Aremco Cement at 800C.
Figure 3.7. Composition of the surface of the Ag in contact with Aremco Cement at
800C.
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Figure 3.8. SEM of silver wire near Aremco Cement at 800C.
Figure 3.9. Composition of the surface of the silver near Aremco Cement at 800C.
During this experiment it was noticed that the phosphorous included in the cement
forms a layer of Ag3PO4 in the surface (see Figure 3.6.), which makes the silver wire
more brittle. After 5 hours, the conductivity of the silver wires starts to be affected. To
minimize the silver wire degradation, as well as to decrease the ohmic resistance and
make a better electrical connection with the potentiostat, a thicker silver wire was
selected (new diameter: 0.25 mm).
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Electrical insulator
To achieve the best measurement of the impedance and other electrical signals the
fuel cell and the silver wires have to be fully isolated from the noise coming from the
induction furnace. A 316 stainless steel alloy tube was used to protect the fuel cell. An
inconel tube was used to protect the silver wires that collect the current and that are
connected to the potentiostat.
Sealing
The most important part of the cell assembly is the sealing between the test station
and the fuel cell, and it is not without challenges. If the system is not completely
sealed, it can result in complications such as loss of voltage, hot spots, and also
explosions. If the leakage is large enough, the hydrogen can be in contact with the
oxygen present in the air, which in a certain range of composition can lead to an
explosion. Appropriate safety measures were taken when conducting the
experiments.
Requirements to achieve the best sealing possible:
Gas tightness
Same thermal expansion between fuel cell and Zirconia tube
Chemical stability and low partial pressure at high temperatures
To match the thermal expansion of the materials involved a Zirconia-based cement
needs to be used, discarding other cements based on conventional glass-ceramic
materials or glass. Another potential solution may be the use of a gold ring. Applying
pressure to this gold ring at high temperatures, the gold will deform itself and seal the
system. This solution was rejected due to manufacture precision issues during the
cutting of the tubes and the higher cost involved, although the main advantage is the
easy and fast replacement of the cell.
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A Zirconia-based cement (Ceramabond 885) provided by Aremco was used. The main
problem encountered in this sealant is that it forms a porous layer. The easy diffusion
of H2 through the layer requires to apply several layers (up to 4) and to cure them
successively to achieve a good sealing and prevent any H2 leakage.
3.2. Preparation of the experiment
3.2.1 Assembly process of the fuel cell
The assembly of this cell is a critical step in the fuel cell testing and in order to achieve
a good result is crucial to have a perfect assembly of the system. The literature is
scarce regarding fuel cell assembly. This methodology used was based on the results
of the Thesis called “Characterization of porous SOFC Electrodes” [Hslao, 1996] and
was specifically adapted and improved for this design.
To make the process easier and time effective when it comes to test more than one
cell, 1 inch of the Zirconia tube was cut to mount the fuel cell. Then, the other side was
pasted with the same cement to the Zirconia tube. This also allows to have more space
to take the silver wire connected to the anode outside of the system. After that,
another collector is placed in the cathode side and pasted with the silver ink.
55. Master Project. Arturo Veiga López 55
Figure 3.10. Image of the Zirconia and inconel tubes with the furnace open.
The current collector is a silver mesh (AG-M40-100) that was cut to fit the shape of
the anode and the cathode. In order to mount the collector in the cathode side, the
anode should not be touched, because that can give us a deviation from the theoretical
potential. Two silver wires of 0.35 mm provided by Goodfellow are responsible for the
conduction of the current and voltage to the potentiostat.
In order to achieve a perfect contact between the collector, the anode, and the
cathode, silver ink (AG-i) is applied. This will keep the mesh in the same place
throughout the experiment. To cure the silver ink it should be fired up to 800 C for 1
hour.
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Figure 3.11. Detailed view of the silver mesh impregnated with the ink and connected to
the wire.
Although silver is not the most suitable material to be used as a collector, because of
the high temperatures reached during the experiment, silver was used due to the
better cost compared to platinum. Using silver allows 5 hours of tests at 800 C, time
after which, the silver starts a degradation process.
Figure 3.12. Detailed view of the cathode side of the fuel cell mounted in the Zirconia
tube.
57. Master Project. Arturo Veiga López 57
Figure 2.13. Final placement of the fuel cell before the test.
In order to increase the temperature of the cell it is extremely important in every
stage not to increase or decrease the temperature more than 1 C/min to prevent
cracks due to the thermal expansion and to allow the cement to expel the gases
produced in the cure process of the cement.
After applying the silver ink to stick the current collectors in the anode and cathode a
thin layer of cement is applied and the following temperature cycle was followed: 2
hours at room temperature, 2 hours at 93 C, 2 hours at 260 C, and 2 hours at 370 C,
and then the temperature was reduced to 20 C. Four layers should be applied and
cured one after another checking that there are no visible cracks after each curing
step.
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Figure 3.14. Curing curves for a layer of cement.
Thereafter, the silver ink is fired according to the manufacturer by increasing the
temperature up to 800 C for one hour. A sealing test is performed to check that there
is no leakage; a mixture of 5% H2 and 95% N2 is pumped through the system and some
overpressure is added to the system bubbling the exhausted gas. Then, with an
hydrogen detector, the entire system is inspected for possible leaks.
3.2.2. Experimental AC impedance procedure
To prepare the fuel cell, the manufacturer does not provide with sufficient
information and different research groups use their own procedure to make the set-
up. Three main aspects need to be taken into account:
1) The leakage is detected by comparison of the open circuit potential with the
theoretic obtained in the Nerst equation for the reaction:
0
50
100
150
200
250
300
350
400
450
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Temperature(C)
Time (h)
Cement cure heat treatment
Real
temperature
Theroretic
temperature
(1°C/min)
59. Master Project. Arturo Veiga López 59
Where:
E - The electromotive force (or reversible open circuit voltage), V
E0 - the EMF at standard pressure, V
R - The universal gas constant, 8.314 JK-1mol-1
F - Faraday constant, 96485 Coulombs
Pi - partial pressure, bar
which in our conditions of gas compositions and temperature (800C, 97% H2
3% H2O, Air) has a value of 1.10 V.
If the voltage is out of the ± 5 %, another layer of cement is recommended. Also,
if the OCP is less than the one predicted, this can be indicative that the
electrolyte layer is not continuous or that it is broken.
2) Anode reduction
Anode reduction is achieved by a mixture of 10% of Hydrogen and 90%
Nitrogen starting at 400 C. According to Xiao (2006), the complete reduction
of the anode will be achieved at 500 C.
3) Conditioning
New fabricated button cells are not in a full equilibrated state and they need a
conditioning; normally the time needed to reduce the anode is enough for
achieving thermal and electrochemical stability.
After having the silver and the cement cured, the procedure starts at room
temperature.
1) The temperature is increased until 400 C with a ramp of 1 C/min without gas
supply.
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2) When 400 C is reached 10 cc/min of N2 is pumped in for about 10 min to
ensure there is no O2 inside the system
3) Then, the anode is reduced according to the above-mentioned description
between the temperatures of 400 and 600 C. Gas supply is stopped after 600
C are reached.
4) At 750 C the gas supply switches to 90% N2, 10% H2 monitoring the open
circuit voltage. When it is close to the theoretical, the gas mixture is changed to
humidified Hydrogen (97% H2 , 3% H2O). Under our experimental conditions, 3
hours were needed to reach an open circuit potential close enough to the
theoretical (1.10 V).
Throughout the process, the temperature of the furnace needs to be monitored and
remain stable; that is, it should not be a difference of more than 5 C between the
highest and the lowest temperature inside it.
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3.3. Results
A two electrodes configuration is used for testing the fuel cell according to the
instructions manual of the PARSTAT 4000 unit.
Figure 3.15. Schematic of the two electrode connection diagram.
In order to test the performance of the SOFC, three electrochemical tests are
performed: open circuit potential, current voltage test, and AC impedance test.
3.3.1 Open circuit potential (OCP)
The OCP of the tested cell was in a range between 1.03 V and 1.12 V, which is close to
the theoretical predicted by the Nest equation: 1.10 V at 800 C. This means that a
good seal is accomplished and that there are no electrical leaks during the tests. It also
ensures the proper operation of the cell.
In Figure 3.16. the OPC trajectory of the fuel cell at 800 C and gas composition of 97%
H2 and 3% H2O are shown.
• WE: Working electrode
• CE: Counter electrode
• SE: Sense electrode
• RE: Reference electrode
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Figure 3.16. Open circuit potential curve at 800C and 97% H2 and 3% H2O.
Before each test, the OCP was checked to verify the integrity of the system. After 7
hours of testing at 800 C, the OCP revealed a drastic drop in the open circuit
potential. After cooling down the test station and examination the fuel cell, it was
observed that the silver mesh that works as current collector was displaced. It is likely
that the silver ink degraded and stopped sticking together the silver mesh and the
anode, due to the long sustained high temperature. The silver ink is recommended for
temperatures under 600 C. In this project, due to the extremely high cost of Platinum,
silver ink mesh and cables were used.
3.3.2. Current voltage curve (i-V)
The voltage and current curve is the main instrument to evaluate the performance of
the fuel cell, maintaining constant the fuel and the temperature. In order to calculate
the current density, the current is divided by the area of the fuel cell in contact with
the gas and the collector resulting in an area of 1.6 cm2.
1
1.02
1.04
1.06
1.08
1.1
1.12
1.14
1.16
1.18
1.2
0 5 10 15 20
E(Volt)
Time (minutes)
Open Circuit Potential
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The measurements were performed every 100 mA cm-2 except from the first 250mA
cm-2 that were measured every 50mA cm-2 to be more accurate. Between each
measure, a relaxation time of 10 min was allowed to achieve a steady state condition.
The measures were performed until the current upper limit was fixed; this happened
when the voltage reached 0.2 V. Another important benchmark of the performance of
the fuel cell using this test is the so called specific area impedance (ASI). ASI is
measured in the middle of the curve and a value of 0.5 Ω or less is accepted as a good
performance of the fuel cell. In our case the ASI achieved was 0.34 Ω.
In Figure 3.17., the i-V curve of the fuel cell at 800 C and fuel composition of 97%H2
and 3%H2O is shown. The curve does not display appreciable hysteresis.
Figure 3.17. i-V curve at 800C and 97% H2 and 3% H2O.
Figure 3.18. shows the power density; the maximum achieved was 0.6 W/cm2 at 1.12
A/cm2.
0
0.2
0.4
0.6
0.8
1
1.2
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2
Voltage(V)
Current (A/cm2)
i-V
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Figure 3.18. Power density curve at 800C and 97% H2 and 3% H2O.
The performance measured by the manufacturer at different temperatures is shown
in Figure 3.19. In comparison with the manufacturer’s material datasheet, our results
are slightly smaller, which may be due to the precision of our system. Also, it is
important to remark, the high sensibility of the temperature, as we can observe in the
graph.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.5 1 1.5 2 2.5
Powerdensity(W/cm2)
Current (A/cm2)
Power density
65. Master Project. Arturo Veiga López 65
Figure 3.19. Fuel cell performance curves. Fuel Cell Materials data sheet for model ASC-
2.0.
3.3.3. Electrochemical impedance spectroscopy
As mentioned in Chapter 1, the AC impedance technique allows us to compare the
different resistances of the fuel cell associated to different phenomena occurring in
the fuel cell, as well as to compare different conditions of the fuel cell to understand
better its behavior.
To perform the AC impedance spectroscopy test, it is required to superimpose an AC
sine wave on the DC potential. One of the key parameters of this technique is the
amplitude of the AC sine wave. Unfortunately, the only option to choose the correct
amplitude is with trial an error. Too large of an amplitude will invalidate the linearity
of the response, which the impedance theory is based on. Too small of an amplitude
66. Master Project. Arturo Veiga López 66
will not create a sufficient strong signal to be analyzed. The values used of this
amplitude are about 5 mV. The frequency range applied is from 1 MHz to 0.5 Hz
In Figure 3.20., the real part of the impedance versus the imaginary part (note that is
minus the imaginary) has been plotted.
Figure 3.20. Results AC impedance spectrocopy. At 800C and 97% H2 and 3% H2O.
With a ZSimDemo3.2 software, a study of the equivalent circuit was made. This fuel
cell fits the equivalent circuit with the following parameters. From them we can say
that the Ohmic resistance is 0.126 Ω and the kinetic resistance is 0.677 Ω.
Ohmic resistance: RΩ = 0.126 Ω
High frequency resistance Rf1 = 0. 62 Ω
High frequency capacitor C1= 0.124 F
Low frequency resistance Rf2 = 0.057 Ω
Low frequency capacitor C2= 0.015 F
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
-Im(Z),Ω
Re(Z), Ω
Impedance spectra
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RΩ Rf,2Rf,1
C1 C2
Figure 3.21. Equivalent circuit of the fuel cell.
Figure 3.22. shows the alignment between the experimental results and the ones
resulting from the equivalent circuit.
Figure 3.22. Experimental results (red); Fitting results (green).
Other gas composition tests were planned to be assayed, but the silver degradation
prevented further testing.
In conclusion, the fuel cell testing system was validated and showed a fairly good
approximation to the values provided by the manufacturer, assuring that the test
station works correctly.
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4. Conclusions
The current research work focuses on the principles of fuel cells and specifically, the
parameters that measure the performance of a solid oxide fuel cell.
A rigorous study has been developed to improve the original Electrostatic Spray
Deposition (ESD) spray system, a new technology to develop a efficient solid oxide
fuel cell. This original EDS spray system was developed in the Thesis: “Electrostatic
spray deposition of Solid Oxide Fuel Cell electrolyte” [He, 2013]. The improvements
developed in the current project focused on enhancing the efficiency of the EDS spray
by achieving a better spray stability.
To increase the stability, and in turn the efficiency of the EDS spray, a more
homogeneous supply of particles is required. This is controlled by two main factors:
the settling of the particles and the tendency of the particles to stick to the container
walls. Several experiments were specifically designed to test these two aspects and
included improvements of the original design that targeted the following aspects:
- Include a reservoir under the nuzzle.
- Avoid the vacuum produced during the spray.
- Create a more uniform electric field.
Several prototypes described in Chapter 2 were developed to test the results of the
above-mentioned aspects. The finished system was tested spraying layers of YSZ up to
14 hours and 70 microns of thickness and we can conclude that this system is
appropriate to produce a stable spray system for YSZ and that the desired thickness
can be obtained varying the deposition time.
Because reducing the spray time is critical to achieve a complete stable spray, a
theoretical analysis was developed to increase the percentage of particles in the
suspension.
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This step is a major hurdle of the design of the EDS spray technology. This project has
only started to assess one of the main problems of this technique. The achievement of
faster deposition rates are still required to develop a future commercial method to
build solid oxide fuel cells.
On the other hand, assessing the performance of a solid oxide fuel cell is required to
improve its efficiency. The second part of this project focused on the design and
manufacture of a solid oxide fuel cell test station and on the evaluation of the
performance of a commercially available fuel cell. The test station was designed and
built focusing on simplicity and robustness.
The designed fuel cell test station was tested with a commercial fuel cell to evaluate its
proper operation and accuracy. Results from these tests were compared to the
specifications provided by the manufacturer. In conclusion, the fuel cell testing system
was validated and showed a fairly good approximation to the values provided by the
manufacturer, validating the functionality of the test station.
As mentioned above, the improvements implemented in the development of a solid
oxide fuel cells, especially the composition of the suspension, are only the tip of the
iceberg of a very complex engineering problem and leave open many unsolved
technical difficulties.
In order to achieve a fully functional and reproducible fuel cell with EDS technique it
will be necessary not only to successfully spray the anode and cathode, but also to find
a solution to support mechanically the fuel cell during the operation time. Future
research is required to target these unsolved questions.
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