The document summarizes research on synthesizing graphene via chemical vapor deposition for use in supercapacitor electrodes. It describes using CVD to deposit graphene on copper foil substrates by flowing methane and hydrogen gases into a heated furnace. Experiments varied the hydrogen flow rate and growth time, finding that higher hydrogen levels and shorter times produced higher quality mono-layer graphene, as shown through Raman spectroscopy analysis. The document also explores electropolishing copper substrates and transferring graphene to other substrates for use in supercapacitors.
GRAPHENE SYNTHESIS AND APPLICATION POSTERAman Gupta
For free download Subscribe to https://www.youtube.com/channel/UCTfiZ8qwZ_8_vTjxeCB037w and Follow https://www.instagram.com/fitrit_2405/ then please contact +91-9045839849 over WhatsApp.
Graphene eplained by poster presentation
Graphene field-effect transistor simulation with TCAD on top-gate dielectric ...TELKOMNIKA JOURNAL
This paper presents the influence of top-gate dielectric material for graphene field-effect transistor (GFET) using TCAD simulation. Apart from silicon-based dielectric that is typically used for top-gate structure, other high-dielectric constant (high-k) dielectric materials namely aluminum oxide and hafnium oxide are also involved in the analysis deliberately to improve the electrical properties of the GFET. The unique GFET current-voltage characteristics against several top-gate dielectric thicknesses are also investigated to guide the wafer fabrication engineers during the process optimization stage. The improvement to critical electrical parameters of GFET in terms of higher saturation drain current and greater on/off current ratio shows that the use of high-k dielectric material with very thin oxide layer is absolutely necessary.
2017 ECS San Francisco Section Cubicciotti Award Ceremony TalkTianyu Liu
Invited by the Electrochemical Society San Francisco Section to give the presentation to highlight my research and extracurricular activities. The award ceremony was held on the campus of UC Berkeley.
GRAPHENE SYNTHESIS AND APPLICATION POSTERAman Gupta
For free download Subscribe to https://www.youtube.com/channel/UCTfiZ8qwZ_8_vTjxeCB037w and Follow https://www.instagram.com/fitrit_2405/ then please contact +91-9045839849 over WhatsApp.
Graphene eplained by poster presentation
Graphene field-effect transistor simulation with TCAD on top-gate dielectric ...TELKOMNIKA JOURNAL
This paper presents the influence of top-gate dielectric material for graphene field-effect transistor (GFET) using TCAD simulation. Apart from silicon-based dielectric that is typically used for top-gate structure, other high-dielectric constant (high-k) dielectric materials namely aluminum oxide and hafnium oxide are also involved in the analysis deliberately to improve the electrical properties of the GFET. The unique GFET current-voltage characteristics against several top-gate dielectric thicknesses are also investigated to guide the wafer fabrication engineers during the process optimization stage. The improvement to critical electrical parameters of GFET in terms of higher saturation drain current and greater on/off current ratio shows that the use of high-k dielectric material with very thin oxide layer is absolutely necessary.
2017 ECS San Francisco Section Cubicciotti Award Ceremony TalkTianyu Liu
Invited by the Electrochemical Society San Francisco Section to give the presentation to highlight my research and extracurricular activities. The award ceremony was held on the campus of UC Berkeley.
20180320 polymer based nanomaterials for supercapacitorsTianyu Liu
The slides for a guest lecture of a graduate course (Chem 6564) offered by the Department of Chemistry, Virginia Polytechnic Institute and State University.
Electron transfer between methyl viologen radicals and graphene oxidekamatlab
Methyl viologen radicals are capable of transferring electrons to graphene oxide and partially restore the sp2 network. The reduced graphene oxide serves as a scaffold to anchor Ag nanoparticles. The growth of these silver nanoparticles is dictated by the ability of RGO to store and shuttle electrons. The RGO/Ag nanocomposites discussed in the present work offer new opportunities to design next generation photocatalysts.
Visit our website, KamatLab.com, for the latest news, publications, and research from our group.
Graphene, a single atom layer of Carbon, has amazing properties, that can be used in various fields such as flexible transparent touch screen, paper battery, ultra capacitor ect. Get an overall knowledge about what is graphene, its structure, synthesis, applications from this slides. Graphene technologies are creating a new era in the material science and hence in other sectors.
Progress in Synthesis of Graphene using CVD, Its Characterization and Challen...paperpublications3
Abstract: Diamond and Graphite both are natural allotropes of carbon. Graphene is a substance composed of sp2 hybridized carbon atoms that are similar to graphite and arranged in a regular hexagonal pattern. Graphene has astounding physical properties such as high electronic conductivity, excellent mechanical strength and thermal stability. It is capable to maintain its strength up to 3,600°C. It is transparent, high super hydrophobicity at nanometer scale , 100 times stronger than steel with high current density. These unique properties make graphene an interesting candidate for a number of applications currently under development, as for instance Li-ion batteries, transparent touch screens, light weight aircrafts or transistors.
Amongst the synthesis techniques, chemical vapor deposition has proved promising result for advance devices and for numerous applications where high-quality graphene films, High purity, fined grained and low structural defects film is required. CVD process is normally conducted below the atmospheric pressure and relatively lower temperatures , less than 1000°C. Pressure of LPCVD is 10-1000 Pascals.
Keywords: CVD, Graphene, Graphite, Graphene sheets..
Title: Progress in Synthesis of Graphene using CVD, Its Characterization and Challenges: A Review
Author: Sakshi Rana, Harminder Singh
International Journal of Recent Research in Electrical and Electronics Engineering (IJRREEE)
ISSN 2349-7815
Paper Publications
Modeling of Dirac voltage for highly p-doped graphene field-effect transistor...journalBEEI
In this paper, the modeling approach of Dirac voltage extraction of highly p-doped graphene field-effect transistor (GFET) measured at atmospheric pressure is presented. The difference of measurement results between atmospheric and vacuum pressures was analyzed. This work was started with actual wafer-scale fabrication of GFET with the purposes of getting functional device and good contact of metal/graphene interface. The output and transfer characteristic curves were measured accordingly to support on GFET functionality and suitability of presented wafer fabrication flow. The Dirac voltage was derived based on the measured output characteristic curve using ambipolar virtual source model parameter extraction methodology. The circuit-level simulation using frequency doubler circuit shows the importance of accurate Dirac voltage value to the device practicality towards design integration.
Critical heat flux enhancement in pool boiling with al2 o3 water nanofluideSAT Journals
Abstract Boiling is an important phase change phenomena as it plays a crucial role in the design of high heat flux system like boilers, heat exchangers, microscopic heat transfer devices. However boiling phenomenon is limited by critical heat flux. At critical heat flux material of heated surface suffers physical damage due to lower heat transfer resulting from thin film formed over the surface. Now a days Nanofluid which is colloidal suspension of nanoparticle in base fluid is highlighted as innovative techniques to enhance critical heat flux. In the present study Al2O3 nanoparticles were characterized by using SEM and XRD analysis. From SEM images it was seen that nanoparticle has spherical morphology, and from XRD analysis average nanoparticle size determined was 29.48 nm. Five different nanofluids of concentration range from 3 gram/liter to 15 gram/liter were prepared. Critical heat flux (CHF) of each Al2O3-water nanofluid in pool boiling is determined on NiCr wire of SWG 28. The minimum critical heat flux enhancement is 30.53% at 3 gram/liter nanofluid compared to critical heat flux of distilled water. The highest critical heat flux enhancement is 72.70 % at 12 gram/liter nanofluid. Critical heat flux of nanofluid increases with increase in concentration of Al2O3 nanoparticle in distilled water up to 12 gram/liter nanofluid. Surface roughness of bare wire was 0.126 μm. Surface roughness of wire sample used in pool boiling of 3 gram/liter nanofluid is 0.299μm and highest surface roughness was 0.715 μm of heater used in pool boiling of 12 gram/liter nanofluid. The Surface roughness measurement results show the evidence of nanoparticle deposition on wire surface and its effect on Critical Heat Flux enhancement. Keywords: Critical heat flux, Nanoparticle, Nanofluid, Concentration, Surface roughness.
20180320 polymer based nanomaterials for supercapacitorsTianyu Liu
The slides for a guest lecture of a graduate course (Chem 6564) offered by the Department of Chemistry, Virginia Polytechnic Institute and State University.
Electron transfer between methyl viologen radicals and graphene oxidekamatlab
Methyl viologen radicals are capable of transferring electrons to graphene oxide and partially restore the sp2 network. The reduced graphene oxide serves as a scaffold to anchor Ag nanoparticles. The growth of these silver nanoparticles is dictated by the ability of RGO to store and shuttle electrons. The RGO/Ag nanocomposites discussed in the present work offer new opportunities to design next generation photocatalysts.
Visit our website, KamatLab.com, for the latest news, publications, and research from our group.
Graphene, a single atom layer of Carbon, has amazing properties, that can be used in various fields such as flexible transparent touch screen, paper battery, ultra capacitor ect. Get an overall knowledge about what is graphene, its structure, synthesis, applications from this slides. Graphene technologies are creating a new era in the material science and hence in other sectors.
Progress in Synthesis of Graphene using CVD, Its Characterization and Challen...paperpublications3
Abstract: Diamond and Graphite both are natural allotropes of carbon. Graphene is a substance composed of sp2 hybridized carbon atoms that are similar to graphite and arranged in a regular hexagonal pattern. Graphene has astounding physical properties such as high electronic conductivity, excellent mechanical strength and thermal stability. It is capable to maintain its strength up to 3,600°C. It is transparent, high super hydrophobicity at nanometer scale , 100 times stronger than steel with high current density. These unique properties make graphene an interesting candidate for a number of applications currently under development, as for instance Li-ion batteries, transparent touch screens, light weight aircrafts or transistors.
Amongst the synthesis techniques, chemical vapor deposition has proved promising result for advance devices and for numerous applications where high-quality graphene films, High purity, fined grained and low structural defects film is required. CVD process is normally conducted below the atmospheric pressure and relatively lower temperatures , less than 1000°C. Pressure of LPCVD is 10-1000 Pascals.
Keywords: CVD, Graphene, Graphite, Graphene sheets..
Title: Progress in Synthesis of Graphene using CVD, Its Characterization and Challenges: A Review
Author: Sakshi Rana, Harminder Singh
International Journal of Recent Research in Electrical and Electronics Engineering (IJRREEE)
ISSN 2349-7815
Paper Publications
Modeling of Dirac voltage for highly p-doped graphene field-effect transistor...journalBEEI
In this paper, the modeling approach of Dirac voltage extraction of highly p-doped graphene field-effect transistor (GFET) measured at atmospheric pressure is presented. The difference of measurement results between atmospheric and vacuum pressures was analyzed. This work was started with actual wafer-scale fabrication of GFET with the purposes of getting functional device and good contact of metal/graphene interface. The output and transfer characteristic curves were measured accordingly to support on GFET functionality and suitability of presented wafer fabrication flow. The Dirac voltage was derived based on the measured output characteristic curve using ambipolar virtual source model parameter extraction methodology. The circuit-level simulation using frequency doubler circuit shows the importance of accurate Dirac voltage value to the device practicality towards design integration.
Critical heat flux enhancement in pool boiling with al2 o3 water nanofluideSAT Journals
Abstract Boiling is an important phase change phenomena as it plays a crucial role in the design of high heat flux system like boilers, heat exchangers, microscopic heat transfer devices. However boiling phenomenon is limited by critical heat flux. At critical heat flux material of heated surface suffers physical damage due to lower heat transfer resulting from thin film formed over the surface. Now a days Nanofluid which is colloidal suspension of nanoparticle in base fluid is highlighted as innovative techniques to enhance critical heat flux. In the present study Al2O3 nanoparticles were characterized by using SEM and XRD analysis. From SEM images it was seen that nanoparticle has spherical morphology, and from XRD analysis average nanoparticle size determined was 29.48 nm. Five different nanofluids of concentration range from 3 gram/liter to 15 gram/liter were prepared. Critical heat flux (CHF) of each Al2O3-water nanofluid in pool boiling is determined on NiCr wire of SWG 28. The minimum critical heat flux enhancement is 30.53% at 3 gram/liter nanofluid compared to critical heat flux of distilled water. The highest critical heat flux enhancement is 72.70 % at 12 gram/liter nanofluid. Critical heat flux of nanofluid increases with increase in concentration of Al2O3 nanoparticle in distilled water up to 12 gram/liter nanofluid. Surface roughness of bare wire was 0.126 μm. Surface roughness of wire sample used in pool boiling of 3 gram/liter nanofluid is 0.299μm and highest surface roughness was 0.715 μm of heater used in pool boiling of 12 gram/liter nanofluid. The Surface roughness measurement results show the evidence of nanoparticle deposition on wire surface and its effect on Critical Heat Flux enhancement. Keywords: Critical heat flux, Nanoparticle, Nanofluid, Concentration, Surface roughness.
Computational Analysis of CuO Nano Coolant in a Car RadiatorIOSRJMCE
Nanofluids are basically nanoparticles in base fluids. Nanofluids have unique features different from conventional solid-liquid mixtures in which nano sized particles of metals and nonmetals are dispersed. Due to improvement of mechanical properties, nanofluids are widely used in heat transfer industries. The coolant is used water-based, with the addition of glycols to prevent freezing and other additives to limit corrosion, erosion and cavitations. In this study 50-50 mixture of Ethylene Glycol with water (EGW) is tested and compared with another mixture by adding 2 percent Copper oxide (CuO). The geometric model of radiator is uploaded in Autodesk CFD software for its computational analysis. It is analyzed up to 100 iterations. Both the results are compared to find the improved heat transfer rate due to the addition of 2% CuO with Ethylene Glycol and water
Effect of Arresters on Erosion in Economizer Zone and its AnalysisIDES Editor
Thermal Power Stations all over the world are facing
the problem of boiler tube leakage frequently. The consequences
of which affects the performance of power plant and huge
amount of money loss. It was also found from the trends of
failure that the economizer is the zone where the leakages are
found more. The maximum number of cause of failure in
economizer unit is due to flue gas erosion. The authors in this
paper have attempted to suggest a probable solution for
reduction of erosion in economiser zone and its analysis using
CFD tool. The past failure details revels that erosion is more in
U-bend areas of Economizer Unit because of increase in flue
gas velocity near these bends. Horizontal Arresters were
provided on the way of flue gas to reduce its velocity near these
bends. But it is observed that the velocity of flue gases
surprisingly increases near the lower bends as compared to
upper ones. In this paper the authors have submitted the
findings of analysis of finned tube economizer with Arresters
at different inclinations. A steady 3D CFD tool is used for
analysis and flow of the flue gases over the coils has been
observed. The effect of provision of arresters on the surface
temperature, the flue gas temperature, pressure and velocity
field of fluid flow within an economizer tube using the actual
boundary conditions have been analyzed using CFD tool. The
analysis considered the inclination of Arresters both in upward
and downward directions. The optimum dimensions of arrester
and feasible inclination is recommended as a result of the study.
The installation of Arresters, may affect the performance of
economizer. The authors have analyzed the performance and
tried to comment on this issue too.
Hydrothermal Assisted Microwave Pyrolysis of Water Hyacinth for Electrochemic...drboon
We develop ‘green’ approach to prepare conductive carbon material from water hyacinth (Eichhornia crassipes) powder for use in electrochemical capacitor device. The features on morphology, crystallography and surface functionality were analyzed based on SEM, XRD and FTIR instrumentation, respectively. The electrical conductivities were measured using four-point probe. Electrochemical properties were studied using cyclic voltammetry. SEM analyses indicated the existence of nanoparticles in the carbon samples. XRD analysis showed that carbon sample had sharp peaks indicating crystallite carbon and sylvite. FTIR analysis showed that the carbon have common surface functionalities which also can be found in other conductive carbon samples. The electrical conductivities test showed that the carbon had 0.001–1.5 S cm-1 of conductivity. The shape of the cyclic voltammograms were typical for carbon electrode that use in electrochemical capacitor.
Higher chromatic rendition with Cr3+ -doped yellow Y3Al5O12:Ce3+ for double-...IJECEIAES
Remote phosphor designs of white-light-emitting diodes (WLEDs) have been recognized for their high thermal stability and excellent luminous efficiency but not for the chromatic rendering. The study presents an approach for the remote phosphor structure to overcome the low-colorrendering issue by enriching its red-light spectral intensity through codoping Cr 3+ and Ce3+ ions into the yellow Y3Al5O12 (YAG) phosphor compound. This ion co-doping process probably enhances emission spectra in the far-red range because of the energy transfer of the integrated ions: Ce3+ Cr 3+. Additionally, the luminescence and color properties of the phosphor layer significantly depend on the doped concentration of the Cr 3+ ion. Here, with 0.008% Cr 3+ in the phosphor composite, either internal or external quantum performances of the dual-layer WLED light are enhanced, which achieved the number of 58.9% and 46.7%, respectively. The color rendering index (CRI) would also be higher if Cr 3+ is added, about 77.9, compared to the CRI of 63.2 when using the original YAG:Ce3+ phosphor layer.
Performance Evaluation of U-Tube Pulsating Heat Pipe with Water-Based Nanofl...Adib Bin Rashid
The safety and efficiency of electronic equipment are becoming increasingly
critical as modern technologies progress significantly. The size of electronic
equipment is shrinking as it becomes more integrated. Hence, the heat load per
unit area increases, and the standard heat dissipation method may not fulfill their
requirements. Therefore, Pulsating Heat Pipe plays an essential role in efficiently
removing heat from congested surfaces to satisfy the requirement. To find
optimized parameters for a PHP, various investigations are conducted in this work
to help performance up-gradation of PHP. As the equipment gets smaller by size
and more heat has to be removed from smaller surfaces, nanoparticles can
significantly increase heat transfer performance. Furthermore, they can augment
the heat transfer ability of fluids inside the PHP by providing capillary wicking,
increased thermal effusivity, hydrodynamic instabilities, and structural disjoining
pressure. In this work, various experiment is carried out with water-based
Aluminum Oxide, Zinc Oxide, and Graphene Oxide Nanofluids. This work will help
upgrade PHP's performance and thus help enhance heat transfer performance
from smaller surfaces like Processor of Computers.
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
The International Journal of Mechanical Engineering Research and Technology is an international online journal published Quarterly offers fast publication schedule whilst maintaining rigorous peer review. The use of recommended electronic formats for article delivery expedites the process of All submitted research articles are subjected to immediate rapid screening by the editors consultation with the Editorial Board or others working in the field of appropriate to ensure that they are likely to be the level of interest and importance of appropriate for the journal.
international research journal of engineering and technology 3 nov.pdfnareshkotra
The International Journal of Mechanical Engineering Research and Technology is an international online journal in English published Quarterly offers a fast publication schedule whilst maintaining a proper peer review and the use of recommended electronic formats for an article delivery expedites the process of All submitted research articles are subjected to an immediate rapid screening by the editors consultation with the Editorial Board or others working in the field as assure that they are likely to be the level of interest and importance of appropriate for the journal.
The International Journal of Mechanical Engineering Research and Technology is an international online journal in English published Quarterly offers a fast publication schedule with whilst maintaining a rigorous peer review and the use of recommended electronic formats for article delivery expedites the process of All submitted research articles are subjected to immediate rapid screening by the editors consultation with the Editorial Board or others working in the field as appropriate to ensure they are likely to be the level of interest and importance appropriate for the journal.
The International Journal of Mechanical Engineering Research and Technology is an international online journal in English published Quarterly offers a fast publication schedule whilst maintaining rigorous peer review the use of recommended electronic formats for article delivery expedites the process All submitted research articles are subjected to immediate rapid screening by the editors consultation with the Editorial Board or others working in the field as appropriate to ensure they are likely to be the level of interest and importance appropriate for the journal.
Experimental Studies on Pool Boiling Heat Transfer Using Alumina and Graphene...
Final REU Poster
1. Introduction and Purpose
Conclusions
Acknowledgements
GRAPHENE SYNTHESIS VIA CHEMICAL VAPOR DEPOSITION FOR USE IN SUPERCAPACITOR ElECTRODES
Michael Curtin, Jian Liu,William E. Bernier, and Wayne E. Jones, Jr
Department of Chemistry, Binghamton University - State University of New York, NY, 13902
Research Experiences For Undergraduates Poster Session, JULY 31, 2014
References
1 Wonbong Choi, et al., Critical Reviews in Solid State and Materials Sciences, 35:1 (2010) 52-71 2 Chenguang Liu, et al., Nano Letters, 10 (2010) 4863–4868 3 Xuesong Li, et al., Science Express, 324 (2009) 1312 4 A.M. Awad, et al., Applied Surface Science 256 (2010) 4370–4375 5 Ajay Kumar and Chee Huei Lee (2013). Synthesis and Biomedical Applications of Graphene: Present and Future Trends, Advances in Graphene Science, Dr. M. Aliofkhazraei (Ed.), ISBN: 978-953-51-1182-5, InTech, DOI: 10.5772/55728.
Results
Graphene, a mono-layer sheet of carbon atoms oriented in a honeycomb crystal lattice has captured considerable attention due to its exceptional electronic and optoelectronic properties. With its high electrical conductivity, optical transparency, and superb thermal properties, graphene has generated extensive research for use in supercapacitor applications.[1] Supercapacitors are electrical energy storage devices that can store and release energy, quite similar to electrochemical batteries. Unlike batteries, supercapacitors are able to charge and discharge rapidly, generating an extremely large amount of power upon discharge. Batteries however remain to have a higher energy density, allowing for extended storage and discharge of energy.[2] Graphene has the capability of enhancing the energy density of a supercapacitor primarily due to its large surface-to-volume ratio. When paired with the electrodes of a supercapacitor cell, graphene’s surface area and high electron mobility create a tremendous amount of space for efficient electrical charge storage.
According to the Raman spectroscopy analysis, the (2D/G) ratio increases with an increasing flow rate of H2 gas, which indicates mono-layer graphene results from increased H2. Also when shortening the growth time, the (2D/G) ratio increased as well. When running an experiment with a much lower concentration of hydrogen under the same conditions, there was no detection of carbon deposition, concluding the pivotal role of hydrogen involved in the chemical vapor deposition of graphene films.
This work was supported by the Research Experiences for Undergraduates (REU) program of the National Science Foundation under Award Number 1263004. This work could not have been completed without the help of the professional and graduate personnel at the Binghamton University Department of Chemistry. Also special thanks to the CASP Lab at Binghamton University for providing the resources necessary for this work to be completed.
The graphene films were prepared using the chemical vapor deposition (CVD) method. Chemical vapor deposition is an efficient deposition process where chemical precursors are transported in the vapor phase to decompose on a heated substrate to form a film [3]. This growth technique was used to produce high-purity, high-performance solid materials. The target substrate for graphene growth included a thin piece of copper foil. The precursor gases used involved both hydrogen (H2) and methane (CH4). The methane gas provides the carbon source for deposition and the hydrogen supply plays the role of a carrier gas for deposition of carbon. Both gases are carefully controlled using digital monitors and gauges that regulate their flow rate and pressure. The process begins with loading the copper sample into a tube furnace and evacuating any air inside to create a vacuum. The furnace is then heated to approximately 1000 °C while the hydrogen gas enters the chamber. Once the temperature reaches1000 °C the copper is annealed for 15 minutes, after which methane is introduced for a desired period of time.[3] This is the effective growth time for the graphene layer. The furnace is rapidly cooled to room temperature, while the remaining waste gas is evacuated through an external pump.
Diagram 1: Double Layer Supercapacitor with Graphene-Coated Aluminum Electrodes
Experiment A
Results and Discussion
Diagram 2: Chemical Vapor Deposition Process
H2
CH4
Flow Rate Controller
Tube Furnace
Copper
Pump/ Evacuation
Pressure Gauge
Carbon Deposition
Heat Flow
Pressure Gauge
Flow Rate (sccm)
Gas Ratio (H2/CH4)
Growth Time (min)
Hydrogen Supply
Sample #
H2
CH4
1
2
35
0.0571
30
Pure Hydrogen
2
10
35
0.286
30
Pure Hydrogen
3
20
35
0.571
30
Pure Hydrogen
4
2
35
0.0571
15
Pure Hydrogen
9
20
35
0.571
30
5% Hydrogen
Figure 1: Raman spectrum for graphene varying H2 concentration
Figure 2: Raman spectrum for graphene varying growth time
Figure 3: Peak intensity ratios for increasing H2 concentration
Table 1: Growth parameters for CVD trials
Running parallel to the cvd experiment included an exploration into the surface morphology of the target substrate Cu, and potential methods for developing a cleaner and smoother surface. The electrochemical technique of electropolishing was further investigated. This process involves removing metal ion by ion from the surface material, leaving behind a microscopically featureless and smooth surface.
Experiment B
The electropolishing process involves making the workpiece anodic by negatively biasing the two electrodes. When an electric potential is applied, a current will travel through a conductive electrolyte and remove ions from the surface of the metal workpiece. To run a successful electropolish, parameters including current density, current duration, concentration of acidic electrolyte and electrode positioning must be carefully chosen and monitored.[4]
Diagram 3: Electropolishing Mechanism
Figure 6: AFM image of Copper sample surface profile before electropolish
Figure 7: AFM image of Copper sample surface profile after electropolish
Experiment C
Although less studied than the graphene growth process, the transfer of graphene from the Copper substrate to another target substrate for use in supercapacitor electrodes has generated interest and investigation. This tricky and delicate process has the potential for developing convenient and much cheaper supercapacitors on an industrial scale
Diagram 4: Graphene transfer process [5]
Figure 5: Raman spectrum for graphene with a varying H2 supply
Figure 4: Peak intensity ratios for varying growth time
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
H2 =2 CH4 =35
H2 =10 CH4 =35
H2 =20 CH4 =35
Intensity
(2D/G) Ratio
(D/G) Ratio
0
0.2
0.4
0.6
0.8
1
1.2
Growth =30 min
Growth = 15 min
Intensity
(2D/G) Ratio
(D/G) Ratio
-1.00E+02
0.00E+00
1.00E+02
2.00E+02
3.00E+02
4.00E+02
5.00E+02
6.00E+02
1.00E+03
1.50E+03
2.00E+03
2.50E+03
3.00E+03
Raman Intensity
Wavenumber (cm-1)
5% Hydrogen Supply
Pure Hydrogen Supply
According to the AFM images, the the copper sample appears to have an increased surface roughness than before the polish. This could be the result of a very aggressive acid concentration.
-1.00E+02
-5.00E+01
0.00E+00
5.00E+01
1.00E+02
1.50E+02
2.00E+02
1.20E+03
1.70E+03
2.20E+03
2.70E+03
Raman Intensity
Wavenumber (cm-1 )
H2=2 CH4=35
H2=10 CH4=35
H2=20 CH4=35
2D
G
D
-1.00E+02
-5.00E+01
0.00E+00
5.00E+01
1.00E+02
1.50E+02
2.00E+02
1.00E+03
1.50E+03
2.00E+03
2.50E+03
3.00E+03
Raman Intensity
Wavenumber (cm-1 )
Growth Time =30 min
Growth Time = 15 min