This document summarizes research on encapsulating the organic ferrimagnet vanadium tetracyanoethylene (V[TCNE]x) to make it air-stable. The encapsulation process involves applying an epoxy encapsulant to the film. Testing found that the encapsulation: 1) Does not interfere with the film's bulk magnetic properties as measured by FTIR and SQUID magnetometry. 2) Increases the film's lifetime when exposed to air from degrading immediately to being stable for 2-4 weeks depending on the property measured, with remanence decaying most rapidly. The encapsulation is a promising first step towards enabling applications of organic magnetic materials.
Repair of teeth with cracks in crowns and roots: An observational clinical studyDR.AJAY BABU GUTTI M.D.S
1) An observational clinical study investigated the survival rate of teeth with longitudinal cracks (PRCT and DRCT) that underwent composite restoration.
2) 180 cracked teeth from 99 patients were included, with 26% surviving after 5 years. Survival was better for PRCT (75%) than DRCT (48%).
3) The adhesive composite restoration technique was found to promote bone repair in most cases and reduce risk of further crack progression or extraction.
While time-consuming, it provided a promising long-term prognosis for vertical root cracks.
Goliath Beniah received his Ph.D. in Chemical Engineering from Northwestern University in 2017. His thesis focused on developing novel non-isocyanate polyurethane materials. He has over 7 publications and 2 invention disclosures. Beniah has work experience in research and development roles at 3M, Valspar, and Lonza Biologics, and his skills include polymer synthesis and characterization techniques. He is currently seeking employment and his references include his Ph.D. advisor at Northwestern University and a group leader from Engineered Polymer Solutions.
Histomorphometric and biomechanical analyses of Self-drilling Orthodontic Tem...Mahfud Mohamed
This study evaluated bone density and torque resistance of two types of self-drilling temporary anchorage devices (TADs): tapered and cylindrical. Six dogs had the TADs inserted between their maxillary premolars and molars. Bone density was measured before and after insertion at 4, 8, and 12 weeks. Cylindrical TADs showed significantly higher bone density immediately after insertion and at 8 weeks. By 12 weeks, there was no significant difference in bone density between TAD types. Cylindrical TADs also showed higher torque resistance upon removal at 12 weeks. Both TAD types remained stable during the 12-week loading period despite immediate loading.
Joint Replacement: The Current and Future Impact of CoatingsApril Bright
The control of surface properties to reduce wear and corrosion and improve biocompatibility is of particular interest today as device companies—and surgeons, payors and patients—seek to extend the life of knee and hip implants. In this session, device companies shared research on their joint replacement coatings and materials, covering pros, cons and the future of their technology.
This document describes a new device designed to measure dental implant stability using resonance frequency analysis. The device uses an electromagnetic actuator to deliver an impact force to the implant, triggering vibrations that are detected to determine the resonance frequency. In vitro and in vivo tests show the device provides measurements that highly correlate with a commercially available device. A clinical study using the new device found initial resonance frequency values above 10 kHz indicated implants were ready for immediate loading, while values from 4-10 kHz required more osseointegration time. The new device allows for minimum contact measurement of implant stability without additional attachment or disassembly steps.
This study assessed whether biostimulation with a diode laser regulates cementoblast functions such as proliferation and biomineralization. Cementoblasts treated with a diode laser showed increased survival and proliferation over time compared to untreated cells. The laser-treated cells also demonstrated more mineralized nodule formation. While further studies are needed, biostimulating cementoblasts with low-level lasers may positively impact periodontal regeneration by allowing cementoblasts to remain in the area longer to aid in new attachment formation.
Coatings: The Power of Bone Integration to Aid Recovery - OMTEC 2018April Bright
Dr. Michael Gentile, DPM, fellow of the American College of Foot and Ankle Surgeons, lends his perspective on future coating technologies and ways to engage coating’s important role in a device. Special focus is given to titanium-integrated PEEK surfaces.
Antimicrobial Coatings: The Research and Regulatory PerspectiveApril Bright
Coatings have long been considered an avenue for infection prevention in orthopedic procedures. These coatings, some of which utilize silver, have largely not been commercialized because regulators seek greater evidence of their safety, creating a long, expensive road for device companies. Announcements in the last half of 2018 and early 2019 indicate that companies continue to push to get them on the market and that productive conversations are taking place with regulators. This session began with a history of antimicrobial coatings followed by a look at recent research and technology.
Repair of teeth with cracks in crowns and roots: An observational clinical studyDR.AJAY BABU GUTTI M.D.S
1) An observational clinical study investigated the survival rate of teeth with longitudinal cracks (PRCT and DRCT) that underwent composite restoration.
2) 180 cracked teeth from 99 patients were included, with 26% surviving after 5 years. Survival was better for PRCT (75%) than DRCT (48%).
3) The adhesive composite restoration technique was found to promote bone repair in most cases and reduce risk of further crack progression or extraction.
While time-consuming, it provided a promising long-term prognosis for vertical root cracks.
Goliath Beniah received his Ph.D. in Chemical Engineering from Northwestern University in 2017. His thesis focused on developing novel non-isocyanate polyurethane materials. He has over 7 publications and 2 invention disclosures. Beniah has work experience in research and development roles at 3M, Valspar, and Lonza Biologics, and his skills include polymer synthesis and characterization techniques. He is currently seeking employment and his references include his Ph.D. advisor at Northwestern University and a group leader from Engineered Polymer Solutions.
Histomorphometric and biomechanical analyses of Self-drilling Orthodontic Tem...Mahfud Mohamed
This study evaluated bone density and torque resistance of two types of self-drilling temporary anchorage devices (TADs): tapered and cylindrical. Six dogs had the TADs inserted between their maxillary premolars and molars. Bone density was measured before and after insertion at 4, 8, and 12 weeks. Cylindrical TADs showed significantly higher bone density immediately after insertion and at 8 weeks. By 12 weeks, there was no significant difference in bone density between TAD types. Cylindrical TADs also showed higher torque resistance upon removal at 12 weeks. Both TAD types remained stable during the 12-week loading period despite immediate loading.
Joint Replacement: The Current and Future Impact of CoatingsApril Bright
The control of surface properties to reduce wear and corrosion and improve biocompatibility is of particular interest today as device companies—and surgeons, payors and patients—seek to extend the life of knee and hip implants. In this session, device companies shared research on their joint replacement coatings and materials, covering pros, cons and the future of their technology.
This document describes a new device designed to measure dental implant stability using resonance frequency analysis. The device uses an electromagnetic actuator to deliver an impact force to the implant, triggering vibrations that are detected to determine the resonance frequency. In vitro and in vivo tests show the device provides measurements that highly correlate with a commercially available device. A clinical study using the new device found initial resonance frequency values above 10 kHz indicated implants were ready for immediate loading, while values from 4-10 kHz required more osseointegration time. The new device allows for minimum contact measurement of implant stability without additional attachment or disassembly steps.
This study assessed whether biostimulation with a diode laser regulates cementoblast functions such as proliferation and biomineralization. Cementoblasts treated with a diode laser showed increased survival and proliferation over time compared to untreated cells. The laser-treated cells also demonstrated more mineralized nodule formation. While further studies are needed, biostimulating cementoblasts with low-level lasers may positively impact periodontal regeneration by allowing cementoblasts to remain in the area longer to aid in new attachment formation.
Coatings: The Power of Bone Integration to Aid Recovery - OMTEC 2018April Bright
Dr. Michael Gentile, DPM, fellow of the American College of Foot and Ankle Surgeons, lends his perspective on future coating technologies and ways to engage coating’s important role in a device. Special focus is given to titanium-integrated PEEK surfaces.
Antimicrobial Coatings: The Research and Regulatory PerspectiveApril Bright
Coatings have long been considered an avenue for infection prevention in orthopedic procedures. These coatings, some of which utilize silver, have largely not been commercialized because regulators seek greater evidence of their safety, creating a long, expensive road for device companies. Announcements in the last half of 2018 and early 2019 indicate that companies continue to push to get them on the market and that productive conversations are taking place with regulators. This session began with a history of antimicrobial coatings followed by a look at recent research and technology.
Optimal growth and characterization of cobalt sulphide thin films fabricated ...Alexander Decker
The document summarizes research on growing and characterizing cobalt sulfide thin films using chemical bath deposition. Key findings include:
1) Cobalt sulfide thin films were successfully deposited on glass from an aqueous solution containing cobalt chloride, thiourea, ammonia, and EDTA.
2) The films showed high absorbance of UV light and low transmittance in the UV region, indicating they could be used in applications requiring UV filtering.
3) Band gap energy of the films was found to be 1.72 eV, making the material suitable for photovoltaic and optoelectronic devices.
the purpose of this
invention is to provide a biological housing system capable of undergoing highly controlled ultrasonic stimulations, capable of guaranteeing, at
the same time, practicality and simplicity of use, low cost and complete sterility of the biological samples tested
Organic transistors were first developed in 1986 and use organic molecules rather than silicon as the active material. They have advantages over traditional silicon transistors such as being lightweight, flexible, cheap to produce, and compatible with solution processing and plastic substrates. Key parameters for organic transistors include mobility, on-off ratio, and threshold voltage. Device design can be top contact or bottom contact, with top contact having superior performance. Pentacene-based organic transistors currently have the best field effect mobility. Improving the dielectric, electrodes, and reducing contact resistance and leakage current can further increase performance. Organic transistors have applications in flexible displays, memory, sensors, and more.
This document reviews acoustic trapping and manipulation of living cells. It discusses how acoustic manipulation works by trapping cells in pressure gradients using ultrasonic standing waves. The ability to non-invasively trap and manipulate live cells could enable applications like selective drug delivery and studying cell-cell interactions. Various acoustic manipulation techniques are described, including using opposing transducers to generate a standing wave for trapping cells. Characterizing the effects on cell viability and measuring acoustic forces are important. The project aims to design a sterilizable device that can optically image cells while acoustically trapping them. Initial tests trapping flour suggest the approach may work for cells.
Radiation Resistance of Teflon as a Filter Moderator Materialkent.riley
This document summarizes the results of irradiating polytetrafluoroethylene (PTFE, also known as Teflon) samples with mixed fields of fast neutrons and gamma rays. Samples were irradiated to doses ranging from 0.3 to 50 million Gy for gamma rays and 0.13 to 80 thousand Gy for fast neutrons. The irradiated samples showed high levels of embrittlement but minimal changes (less than 1.5%) in properties like weight loss, fluorine loss, and swelling even at the highest doses. PTFE appears to have adequate physical and chemical stability for use in neutron filter applications in nuclear reactors.
Plenary lecture of the XIII SBPMat (Brazilian MRS) meeting, given on September 30th 2014 by Karl Leo, professor of optoelectronics at Dresden University of Technology (Germany) and director of the Solar and Photovoltaic Engineering Research Center at KAUST (Saudi Arabia).
Transparent Conducting Oxides for Thin Film PVcdtpv
This document summarizes research on transparent conducting oxides (TCOs) for thin film photovoltaics. It discusses TCO properties and applications in different solar cell technologies. Specific materials discussed include ZnO, CdO, and Cd2SnO4. For CdO, it summarizes findings on conductivity, mobility, band structure, and fundamental band gap determination as a function of temperature and carrier concentration. Combinatorial optimization studies of ZnO are also outlined. In general, the document examines TCO physics and materials development to improve thin film solar cell performance and efficiency.
The document compares the pulse-echo and through-transmission ultrasonic techniques for evaluating fiber content in glass/epoxy composites. Specimens with varying glass content from 30-65% were tested using both techniques and results were compared to destructive analysis. Both ultrasonic methods showed good agreement with each other and provided linear relationships between wave velocity and fiber content. Through-transmission was faster but required access to both sides, while pulse-echo could be used with one-side access. Overall, the study found that both ultrasonic techniques are effective non-destructive tools for evaluating fiber content in composites.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
In vitro tests of adhesive and composite dental materialsSilas Toka
The document summarizes a review article on the relevance of in vitro tests of adhesive and composite dental materials. It discusses how laboratory tests are standardized according to ISO protocols to evaluate properties like depth of cure, flexural strength, water sorption and solubility. While laboratory tests provide useful data on material properties, they do not replace clinical studies. Some laboratory recommendations did not prove superior to simpler techniques in clinical trials. Additionally, unexpected clinical problems may arise that were not anticipated by laboratory testing alone, emphasizing the need to augment laboratory studies with long-term clinical evaluations.
In vitro tests of adhesive and composite dental materialsSilas Toka
The document summarizes a review article on the relevance of in vitro tests of adhesive and composite dental materials. It discusses how laboratory tests are conducted according to ISO standards to evaluate properties like depth of cure, flexural strength, water sorption and solubility. While such tests provide standardized physical property data, they do not replace clinical studies. Laboratory tests only partially correlate with clinical performance and cannot predict all potential problems. Both laboratory and long-term clinical studies are needed to fully assess new dental materials.
Ultrasonic testing of glass fiber reinforced polypropylene compositesIAEME Publication
This document discusses ultrasonic testing of glass fiber reinforced polypropylene composites to determine the relationship between fatigue-induced strength degradation and changes in ultrasonic wave velocity and damping coefficient. Samples were subjected to oscillating bending loads and ultrasonic testing at various cycle intervals. A good correlation was found between decreasing ultrasonic wave velocity and increasing strength degradation with more fatigue cycles. Ultrasonic testing is proposed as an effective non-destructive method to assess fatigue degradation in polymer composites. Further research on other materials and loading conditions is planned.
This document summarizes a finite element study of piezoelectric thin films on substrates. It outlines the background on piezoelectricity, modeling preliminaries including governing equations and material properties. It then lists the main tasks which include analyzing the effects of periodicity, lattice mismatch, and different film-substrate properties on the piezoelectric response and internal stress. Publications resulting from this work are also listed.
1.1 The aim of the experiment
The aim of the experiment is to test the usefulness of the ultrasonic waves, by passing them through different
solids one can find out a lot of physical properties like young’s modulus , defects, Poisson ratio, Velocity of
sound in respective material this is due to the response of the received ultrasonic waves.
1.2 Theory of experiment
Ultrasonic testing (UT) is a family of non-destructive testing (NDT) techniques based on the propagation of ultrasonic waves in the object or material tested. In most common UT applications, very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz, and occasionally up to 50 MHz, are transmitted into materials to detect internal flaws or to characterize materials. A common example is ultrasonic thickness measurement, which tests the thickness of the test object, for example, to monitor pipework corrosion.
Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. It is used in many industries including steel and aluminium construction, metallurgy, manufacturing, aerospace, automotive and other transportation sectors.
An Experimental Analysis to Determine Ultimate Tensile Strength of Jute Reinf...IJSRD
From past few decades, there is been substantial growth and development in field of Composites. Advanced materials and Composites are being used in almost every industry in some form or the other. Composites have found wider applicability and liking in designing industries. This has triggered researchers towards this emerging technology. Jute reinforced composites may be used in combination with biodegradable polymer or to replace conventional glass fibre reinforced composites. In this case, the main concern is their impact resistance. The production of hybrid laminates by coupling layers of glass fibre reinforced with jute reinforced laminates, proved also effective to improve the mechanical characteristics. In recent years, a number of studies have been carried out, aimed to compare properties of jute fibre reinforced laminates. This project studies Mechanical properties of Jute Reinforced Glass Fibre Composite by Acousto-Ultrasonic Technique. The specimens were tested for UTS on UTM and the correlation factors were determined by comparing SWF (Stress Wave Factors) and UTS. The comparative analyses are presented in results.
This document discusses phononic crystals and acoustic metamaterials. Phononic crystals are periodically arranged materials that can strongly confine, diffract, and disperse elastic waves. They can create band gaps where waves become evanescent, and exhibit phenomena like negative refraction. Experiments have demonstrated band gaps, tunneling, confinement in defects, and locally resonant acoustic shields. Future work includes developing three-dimensional phononic crystals and incorporating phononic structures into surface acoustic wave and Lamb wave devices to control elastic waves at higher frequencies.
This document summarizes research on hypersonic phononic crystals conducted by Edwin L. Thomas at MIT. Key points:
1) Phononic crystals have periodic variations in density and elastic constants that create band gaps for sound/mechanical waves, allowing uses like sound isolation. The research focuses on hypersonic crystals with 100nm features for enhancing acousto-optical interactions.
2) Hypersonic phononic crystals with band gaps in the GHz frequency range were fabricated using interference lithography and their phonon dispersion was measured using Brillouin light scattering, demonstrating the first experimentally observed band gap at hypersonic frequencies.
3) The grant supported graduate students working on fabricating the crystals using
Arranging atoms one by one the way we want themOndrej Dyck
Can we build structures and devices atom-by-atom? Researchers at Oak Ridge National Laboratory are using electron beams to manipulate materials at the atomic scale. In this presentation they make the case that the future of atomic fabrication with electron beams will combine materials synthesis in the scanning transmission electron microscope
This document discusses the safety of cellphone radiation based on photon energy levels. It makes three key points:
1) Cellphones operate in the classical wave limit of high photon densities, not the single photon limit, so the energy of individual photons is irrelevant to safety.
2) The photon flux from cellphones is many orders of magnitude greater than levels that have produced biological effects in studies. Effects could result from coherent photon energies combining to do work inside cells.
3) Estimates suggest exposure levels above 30pW/m^2 could produce biological damage, whereas cellphones typically emit hundreds of V/m, exceeding considered "safe" levels for large neurons. Many studies have found health effects from
Optimal growth and characterization of cobalt sulphide thin films fabricated ...Alexander Decker
The document summarizes research on growing and characterizing cobalt sulfide thin films using chemical bath deposition. Key findings include:
1) Cobalt sulfide thin films were successfully deposited on glass from an aqueous solution containing cobalt chloride, thiourea, ammonia, and EDTA.
2) The films showed high absorbance of UV light and low transmittance in the UV region, indicating they could be used in applications requiring UV filtering.
3) Band gap energy of the films was found to be 1.72 eV, making the material suitable for photovoltaic and optoelectronic devices.
the purpose of this
invention is to provide a biological housing system capable of undergoing highly controlled ultrasonic stimulations, capable of guaranteeing, at
the same time, practicality and simplicity of use, low cost and complete sterility of the biological samples tested
Organic transistors were first developed in 1986 and use organic molecules rather than silicon as the active material. They have advantages over traditional silicon transistors such as being lightweight, flexible, cheap to produce, and compatible with solution processing and plastic substrates. Key parameters for organic transistors include mobility, on-off ratio, and threshold voltage. Device design can be top contact or bottom contact, with top contact having superior performance. Pentacene-based organic transistors currently have the best field effect mobility. Improving the dielectric, electrodes, and reducing contact resistance and leakage current can further increase performance. Organic transistors have applications in flexible displays, memory, sensors, and more.
This document reviews acoustic trapping and manipulation of living cells. It discusses how acoustic manipulation works by trapping cells in pressure gradients using ultrasonic standing waves. The ability to non-invasively trap and manipulate live cells could enable applications like selective drug delivery and studying cell-cell interactions. Various acoustic manipulation techniques are described, including using opposing transducers to generate a standing wave for trapping cells. Characterizing the effects on cell viability and measuring acoustic forces are important. The project aims to design a sterilizable device that can optically image cells while acoustically trapping them. Initial tests trapping flour suggest the approach may work for cells.
Radiation Resistance of Teflon as a Filter Moderator Materialkent.riley
This document summarizes the results of irradiating polytetrafluoroethylene (PTFE, also known as Teflon) samples with mixed fields of fast neutrons and gamma rays. Samples were irradiated to doses ranging from 0.3 to 50 million Gy for gamma rays and 0.13 to 80 thousand Gy for fast neutrons. The irradiated samples showed high levels of embrittlement but minimal changes (less than 1.5%) in properties like weight loss, fluorine loss, and swelling even at the highest doses. PTFE appears to have adequate physical and chemical stability for use in neutron filter applications in nuclear reactors.
Plenary lecture of the XIII SBPMat (Brazilian MRS) meeting, given on September 30th 2014 by Karl Leo, professor of optoelectronics at Dresden University of Technology (Germany) and director of the Solar and Photovoltaic Engineering Research Center at KAUST (Saudi Arabia).
Transparent Conducting Oxides for Thin Film PVcdtpv
This document summarizes research on transparent conducting oxides (TCOs) for thin film photovoltaics. It discusses TCO properties and applications in different solar cell technologies. Specific materials discussed include ZnO, CdO, and Cd2SnO4. For CdO, it summarizes findings on conductivity, mobility, band structure, and fundamental band gap determination as a function of temperature and carrier concentration. Combinatorial optimization studies of ZnO are also outlined. In general, the document examines TCO physics and materials development to improve thin film solar cell performance and efficiency.
The document compares the pulse-echo and through-transmission ultrasonic techniques for evaluating fiber content in glass/epoxy composites. Specimens with varying glass content from 30-65% were tested using both techniques and results were compared to destructive analysis. Both ultrasonic methods showed good agreement with each other and provided linear relationships between wave velocity and fiber content. Through-transmission was faster but required access to both sides, while pulse-echo could be used with one-side access. Overall, the study found that both ultrasonic techniques are effective non-destructive tools for evaluating fiber content in composites.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
In vitro tests of adhesive and composite dental materialsSilas Toka
The document summarizes a review article on the relevance of in vitro tests of adhesive and composite dental materials. It discusses how laboratory tests are standardized according to ISO protocols to evaluate properties like depth of cure, flexural strength, water sorption and solubility. While laboratory tests provide useful data on material properties, they do not replace clinical studies. Some laboratory recommendations did not prove superior to simpler techniques in clinical trials. Additionally, unexpected clinical problems may arise that were not anticipated by laboratory testing alone, emphasizing the need to augment laboratory studies with long-term clinical evaluations.
In vitro tests of adhesive and composite dental materialsSilas Toka
The document summarizes a review article on the relevance of in vitro tests of adhesive and composite dental materials. It discusses how laboratory tests are conducted according to ISO standards to evaluate properties like depth of cure, flexural strength, water sorption and solubility. While such tests provide standardized physical property data, they do not replace clinical studies. Laboratory tests only partially correlate with clinical performance and cannot predict all potential problems. Both laboratory and long-term clinical studies are needed to fully assess new dental materials.
Ultrasonic testing of glass fiber reinforced polypropylene compositesIAEME Publication
This document discusses ultrasonic testing of glass fiber reinforced polypropylene composites to determine the relationship between fatigue-induced strength degradation and changes in ultrasonic wave velocity and damping coefficient. Samples were subjected to oscillating bending loads and ultrasonic testing at various cycle intervals. A good correlation was found between decreasing ultrasonic wave velocity and increasing strength degradation with more fatigue cycles. Ultrasonic testing is proposed as an effective non-destructive method to assess fatigue degradation in polymer composites. Further research on other materials and loading conditions is planned.
This document summarizes a finite element study of piezoelectric thin films on substrates. It outlines the background on piezoelectricity, modeling preliminaries including governing equations and material properties. It then lists the main tasks which include analyzing the effects of periodicity, lattice mismatch, and different film-substrate properties on the piezoelectric response and internal stress. Publications resulting from this work are also listed.
1.1 The aim of the experiment
The aim of the experiment is to test the usefulness of the ultrasonic waves, by passing them through different
solids one can find out a lot of physical properties like young’s modulus , defects, Poisson ratio, Velocity of
sound in respective material this is due to the response of the received ultrasonic waves.
1.2 Theory of experiment
Ultrasonic testing (UT) is a family of non-destructive testing (NDT) techniques based on the propagation of ultrasonic waves in the object or material tested. In most common UT applications, very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz, and occasionally up to 50 MHz, are transmitted into materials to detect internal flaws or to characterize materials. A common example is ultrasonic thickness measurement, which tests the thickness of the test object, for example, to monitor pipework corrosion.
Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. It is used in many industries including steel and aluminium construction, metallurgy, manufacturing, aerospace, automotive and other transportation sectors.
An Experimental Analysis to Determine Ultimate Tensile Strength of Jute Reinf...IJSRD
From past few decades, there is been substantial growth and development in field of Composites. Advanced materials and Composites are being used in almost every industry in some form or the other. Composites have found wider applicability and liking in designing industries. This has triggered researchers towards this emerging technology. Jute reinforced composites may be used in combination with biodegradable polymer or to replace conventional glass fibre reinforced composites. In this case, the main concern is their impact resistance. The production of hybrid laminates by coupling layers of glass fibre reinforced with jute reinforced laminates, proved also effective to improve the mechanical characteristics. In recent years, a number of studies have been carried out, aimed to compare properties of jute fibre reinforced laminates. This project studies Mechanical properties of Jute Reinforced Glass Fibre Composite by Acousto-Ultrasonic Technique. The specimens were tested for UTS on UTM and the correlation factors were determined by comparing SWF (Stress Wave Factors) and UTS. The comparative analyses are presented in results.
This document discusses phononic crystals and acoustic metamaterials. Phononic crystals are periodically arranged materials that can strongly confine, diffract, and disperse elastic waves. They can create band gaps where waves become evanescent, and exhibit phenomena like negative refraction. Experiments have demonstrated band gaps, tunneling, confinement in defects, and locally resonant acoustic shields. Future work includes developing three-dimensional phononic crystals and incorporating phononic structures into surface acoustic wave and Lamb wave devices to control elastic waves at higher frequencies.
This document summarizes research on hypersonic phononic crystals conducted by Edwin L. Thomas at MIT. Key points:
1) Phononic crystals have periodic variations in density and elastic constants that create band gaps for sound/mechanical waves, allowing uses like sound isolation. The research focuses on hypersonic crystals with 100nm features for enhancing acousto-optical interactions.
2) Hypersonic phononic crystals with band gaps in the GHz frequency range were fabricated using interference lithography and their phonon dispersion was measured using Brillouin light scattering, demonstrating the first experimentally observed band gap at hypersonic frequencies.
3) The grant supported graduate students working on fabricating the crystals using
Arranging atoms one by one the way we want themOndrej Dyck
Can we build structures and devices atom-by-atom? Researchers at Oak Ridge National Laboratory are using electron beams to manipulate materials at the atomic scale. In this presentation they make the case that the future of atomic fabrication with electron beams will combine materials synthesis in the scanning transmission electron microscope
This document discusses the safety of cellphone radiation based on photon energy levels. It makes three key points:
1) Cellphones operate in the classical wave limit of high photon densities, not the single photon limit, so the energy of individual photons is irrelevant to safety.
2) The photon flux from cellphones is many orders of magnitude greater than levels that have produced biological effects in studies. Effects could result from coherent photon energies combining to do work inside cells.
3) Estimates suggest exposure levels above 30pW/m^2 could produce biological damage, whereas cellphones typically emit hundreds of V/m, exceeding considered "safe" levels for large neurons. Many studies have found health effects from
1. Realization of Air-Stable Encapsulated Vanadium
Tetracyanoethylene
• Context & motivation
• Encapsulation Process
• Does the process damage
the film?
• Does it protect the film?
• Implications
I. H. Froning1, M. Harberts1, Y. Lu2, H. Yu1, A. J. Epstein 1,2, and E. Johnston-Halperin1
1Department of Physics, The Ohio State University, Columbus, OH 43210-1117, USA
2Department of Chemistry, The Ohio State University, Columbus, OH 43210-1173, USA
Day 28Day 1
BareEncapsulated
1 cm
1 cm
Grant DMR1207243
2. Organic, magnetic devices can do more if
they are air stable
• Many organic materials are air-sensitive (ours included)
Air stability would allow for broader use
• A multiplicity of encapsulation strategies has been
developed for air-sensitive OLEDs, OPVs, and OFETs
Flexible, air-stable devices exist in all of these areas1,2,3,4
Long-range ordering could make encapsulation of magnetic
materials more difficult
• Why not try existing encapsulation techniques on
organic magnets (and see if it works)?
1. Chwang, Rothman, Mao, et al., Appl. Phys. Lett. 83, 413 (2003).
2. Lungenschmied, Dennler, Neugebauer, et al., Sol. Energy Mater. Sol. Cells 91, 379 (2007).
3. Sekitani, Zschieschang, Klauk, and Someya, Nat. Mater. 9, 1015 (2010).
4. Kaltenbrunner, Sekitani, Reeder, Yokota, et al., Nature 499, 458 (2013).
3. V[TCNE]x is an interesting material, and so
we’d like to encapsulate it
It’s a room-temperature
organic ferrimagnet…
• Demonstrated potential for
use in spin valves5,6 &
microwave electronics7
• Straightforward to make8
• TC near 600 K
…but it’s air sensitive
• Begins degrading immediately
after air-exposure
Loses opacity as it does
• Must seal samples in order to
perform experiments
26 Hours0 Hours
T=300 K
H=100 Oe
5. Yoo, Chen et al., Nat. Mater. 9, 638 (2010).
6. Li, C.-Y. Kao et al., Adv. Mater. 23, 3382 (2011).
7. Yu, Harberts et al., Appl. Phys. Lett. 105, 012407 (2014).
8. Harberts, Lu, Yu, et al., in press, J. Vis. Exp.
4. Encapsulation process is straightforward
Two Questions:
• Does it interfere with
the film’s bulk
magnetic properties?
• If not, does it protect
the film’s bulk
magnetic properties?• Apply Ossila E131
Encapsulation Epoxy to
film with syringe
• Put cover slide on top
• Illuminate for 1 hour
5. QUESTION 1: does this interfere with
V[TCNE]x’s bulk properties?
FTIR
• No new bonds in bulk
SQUID Magnetometry
• Magnetic moment not
suppressed
• Coercivity unchanged Suggests
minimal interaction at epoxy-
V[TCNE]x interface
Compare bare samples to encapsulated samples without
exposing either to atmosphere
Conclusion: bulk magnetic properties are largely unaffected
Transmission(a.u.)
Wavenumber (cm-1)
T=300 K
6. QUESTION 2: does this preserve V[TCNE]x’s
bulk magnetic properties?
• Coercivity and saturation
are robust
• Remanence drops more
rapidly
Monitor encapsulated sample over time. How long is it
stable?
Conclusion: The overall lifetime is increased, but can we
characterize the decay process more clearly?
-70 0 70
0
-40
40
H (kOe)
M(emu/cm3)
T=300 K
7. What is the decay process?
• Remanence goes to 0
by 710 hours (1 month)
• TC & saturation are
more robust
TC above 300 K at 710
hours
Our understanding:
loss of long range order,
then loss of spins
Conclusion: The encapsulated sample takes 1 month to degrade
completely but different parameters decay at different rates
8. Conclusions
• Encapsulated V[TCNE]x is
air-stable for 2 to 4 weeks,
depending on what
parameters are important
to a given measurement
Can perform measurements
under atmospheric
conditions!
• This is the first
encapsulation method we
tried
• Points to a promising
future for organic
magnetic devices!
Day 28Day 1
BareEncapsulated
Editor's Notes
Thank you for the introduction. My goal, over the next 10 minutes, will be to demonstrate why and how we encapsulate this promising organic-based magnet, before answering two questions: 1st, does the encapsulation process damage the film; and 2nd, does it protect the film? I will end by briefly discussing the implications of this work for the field. As a non-quantitative preview though, the top row here shows a bare film of VTCNE on the day of growth, and 1 month later, whereas the second row shows the same thing for an encapsulated film.
The organic magnets my lab works are air-sensitive. And that’s a problem not just because it makes working with these materials difficult for us. It’s a problem because we want collaborators in academia to use these materials to study magnetism. We want industry to use them in the kind of low-cost, chemically tunable spintronics devices and flexible, high frequency magnetoelectronics applications that we know they are often well suited for. A lot of that becomes much easier if these materials are air-stable.
It is encouraging to remember, however, that many other organic electronics are also air-sensitive. This has led to a multiplicity of encapsulation strategies for OLEDs, OPVs, and OFETs. Flexible, air-stable devices have been demonstrated in all three of these areas. Now, there is no reason to expect that, just because a strategy works on an OLED, it will work on a magnetic material too. In particular, if an OLED degrades at its surface, that only affects charge transport at the surface. Magnetic ordering, on the other hand, is a long range effect, and so if the surface is damaged, that damage could be reflected in the bulk magnetic properties of the material.
Still, if applying these techniques to organic magnets makes them more air-stable, that provides a great opportunity to explore these materials in new regimes. So there’s not much to lose by trying.
The magnet we work with most often is VTCNE, which is an interesting material with a notable limitation. Let’s start with why it’s interesting.
First, it’s a thin-film organic-based ferrimagnet, with demonstrated potential for use in spintronics and microwave electronics applications. It’s also relatively straightforward to grow via chemical vapor deposition at low temperatures and pressures. Most importantly for the purposes of this discussion, though, it has a Curie temperature near 600 Kelvin, so it’s magnetic properties are already fairly stable with respect to temperature. This makes it a good candidate for device applications, but…
…It’s air-sensitive! It begins to degrade immediately after being exposed to air, which means that we cannot perform measurements on samples without first sealing them in specialized assemblies, specific to each measurement we want to do. And that works – we’ve had success doing it that way for years – but it’s cumbersome. And it makes broader applications of the material more difficult. So. Can we make it air-stable, and if so, for how long?
The encapsulation strategy we used is straightforward. We purchased a UV-cured epoxy, intended for use with organic materials, applied several droplets of it to the top of our film, pressed down on top of that with a cover slide, and illuminated with white light for one hour to cure it. And… that’s it. The easy part is done: now we need to figure out whether this works, and to do that, we need to answer two questions:
1st, does the epoxy interfere with the film’s bulk magnetic properties? And 2nd, does it actually protect those properties against degradation?
So, what does this epoxy do to the VTCNE film? Does it interact with it? Kill the magnetic moment of the sample?
To address this, we compared unprotected VTCNE films to encapsulated films using two methods: Fourier Transform Infrared Spectroscopy, and SQUID magnetometry – without exposing any samples to the atmosphere.
On this slide everything in red is a bare film, and everything in blue is encapsulated. The top curve here shows the results of an FTIR measurement on bare VTCNE, with the cyano bond highlighted. The bottom curve is encapsulated VTCNE, with the background signal of the epoxy we applied subtracted – this should show us whether the epoxy has broken the bond between the cyano group and vanadium ion in the bulk of the material. We see no evidence of new bonds, although this does not preclude surface interactions. This promising, but what we really want to know is whether encapsulation affects the magnetic moment of the sample, and for that we turn to magnetometry measurements.
The figure on the right shows the volume-normalized, room temperature M vs H plots of bare and encapsulated VTCNE at high field to examine the effects of encapsulation on the overall magnetization of the films. We see that that the saturation magnetization of the encapsulated film (in blue) is not suppressed by the presence of the epoxy.
Next, let’s look at low field effects. Here is the same figure, zoomed in to the region of the hysteresis loop and normalized by remanence rather than volume. This normalization lets us examine any changes in the shape of the loop, independent of overall sample magnetization: what we’re asking here is whether the magnetic behavior of the encapsulated film is markedly different from that of a bare film. The shapes are remarkably similar, and the coercivity is unchanged by the presence of the epoxy. We note that coercivity is an extrinsic parameter that should be sensitive to interactions at the epoxy-VTCNE interface. Thus, we have indirect evidence that these interactions are minimal…
..and we conclude that the bulk magnetic properties of the VTCNE films are largely unaffected by this encapsulation process.
Now, this is promising, but, remember that the point of encapsulating these samples is to increase their in-air lifetime. Have we achieved that?
To address that 2nd question, we performed more SQUID magnetometry measurements on another encapsulated VTCNE film, exposed to air over the course of one month.
Here, none of the curves are normalized by remanence – only by volume – but once again the main figure is a zoomed-in picture of the hysteresis loop, and the inset shows the full field sweep. We see that the coercivity in the main figure and saturation magnetization in the inset are unchanged until 340 hours, or about 2 weeks, and the saturation is still nonzero after 710 hours, or 1 month, which is a significant improvement over their usual lifetime of 10s of minutes. The remanence drops more rapidly however, which suggests a more complicated decay process.
So this figure tells us that the film is still magnetic after 1 month, but perhaps we can see the decay process more clearly by extracting some magnetic parameters from this data and plotting them over time.
Here, we plot three magnetic parameters of the encapsulated sample from the last slide as a function of exposure time, on a semi-log scale. Those parameters are Curie temperature, saturation magnetization, and remanence. We see that after 1 month, the remanence has dropped to nearly 0, but TC and Ms decay more slowly. We believe this signifies that as the sample decays there is a loss of long-range order before there is a loss of spins. This is in accordance with our understanding of what makes encapsulation of a magnetic material different from OLED encapsulation: surface degradation in an OLED only affects the material locally, whereas a magnetic ordering parameter like remanence is globally sensitive to these surface effects and therefore likely to be less robust against degradation.
However, the fact that the Curie temperature is still above room temperature after 1 month means that, even if magnets are harder to protect than OLEDs, this encapsulation strategy has increased the overall lifetime of the sample from 10s of minutes to 1 month.
That’s a major improvement. Depending on what magnetic parameters are important to a given measurement, this means that encapsulated VTCNE is now air-stable for 2 to 4 weeks. That’s immediately useful: if we have a measurement we’d like to perform on a VTCNE film that takes, say, a few days to run, and requires the sample to be exposed to air for that whole time, we can do that now. Previously, if that measurement took even an hour, we had to seal the sample within a specialized assembly to protect it from the ambient environment.
I’d also like to point out that this is the first encapsulation method we tried. Different methods that work with other organic electronics may work on organic magnets as well. The takeaway here is that there is almost certainly room for improvement.
Which brings me to my last, most important point. Organic magnets have not found their way into consumer electronics the way OLEDs have. There are a number of reasons for this, but lack of air-stability is a critical constraint – a device with an in-air lifetime of 20 minutes is just not that useful in most contexts. The work I’ve presented here demonstrates a result that has been immediately useful in our own lab, but it also points to a promising future of air-stable, organic-based, magnetic devices.
So thank you for your time and your attention, and for more details, we have a paper in review. But, for now, I’d like to open it up for a couple minutes of questions.