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Full-Text Articles in Engineering

Optimized Electrochemical Performance Of Si@C Prepared By Hydrothermal Reaction And Glucose Carbon Source, Si Chen, Song-Sheng Zheng, Lei-Ming Zheng, Ye-Han Zhang, Zhao-Lin Wang Aug 2022

Optimized Electrochemical Performance Of Si@C Prepared By Hydrothermal Reaction And Glucose Carbon Source, Si Chen, Song-Sheng Zheng, Lei-Ming Zheng, Ye-Han Zhang, Zhao-Lin Wang

Journal of Electrochemistry

Silicon (Si) has been considered as the potential material for the next-generation lithium-ion batteries (LIBs) for its high capacity (4200 mAh·g-1, Li22Si5) and suitable working voltage (about 0.25 V vs. Li/Li+). However, the cycling stability and electrochemical performance of Si anode become significant challenges because of low intrinsic conductivity and huge volume variation (about 400%) during cycling processes. In addition, the repeated formation and destruction of surface solid electrolyte interphase (SEI) film will continuously consume the electrolyte and cause damage to LIBs. Carbon (C) materials, such as graphite, carbon spheres and tubes, …


Facile One-Step Solid-State Synthesis Of Ni-Rich Layered Oxide Cathodes For Lithium-Ion Batteries, Jing-Yue Wang, Rui Wang, Shi-Qi Wang, Li-Fan Wang, Chun Zhan Aug 2022

Facile One-Step Solid-State Synthesis Of Ni-Rich Layered Oxide Cathodes For Lithium-Ion Batteries, Jing-Yue Wang, Rui Wang, Shi-Qi Wang, Li-Fan Wang, Chun Zhan

Journal of Electrochemistry

Nickel-rich layered oxide is one of the dominate cathode materials in the lithium ion batteries, due to its high specific energy density meeting the range requirement of the electric vehicles. Typically, the commercial Ni-rich layered oxides are synthesized from co-precipitated precursors, while precision control is required in the co-precipitation process to ensure the atomic level mixing of the cations such as Ni, Co and Mn, et.al. In this work, a one-step solid-state method was successfully applied to synthesize the Ni-rich layered oxide materials with ultra-high Ni content. By choosing the nickel hydroxides as the precursor with layered structure similar to …


Advanced Lithium Metal Batteries: Functional Electrolyte Additive And Lithium Metal/Solid-State Electrolyte Interface Engineering, Abiral Baniya Aug 2022

Advanced Lithium Metal Batteries: Functional Electrolyte Additive And Lithium Metal/Solid-State Electrolyte Interface Engineering, Abiral Baniya

Dissertations - ALL

Majority of the energy in current world is produced and consumed by burning non-renewable fossil fuel sources such as coal, oil, and natural gas, etc. It is taking a toll on our planet earth due to high rates of carbon and greenhouse emissions. This calls for an urgent need of energy transition from conventional fossil fuel to renewable and sustainable energy sources such as solar, wind, geothermal, etc. However, harnessing energy from such renewables are constrained by their intermittency and non-dispatchability, requiring some sort of efficient energy storage systems that can provide continuous energy supply. Batteries in general are considered …


Do Agrivoltaics Improve Public Support For Solar? A Survey On Perceptions, Preferences, And Priorities, Alexis Pascaris, Chelsea Schelly, Mark Rouleau, Joshua Pearce Aug 2022

Do Agrivoltaics Improve Public Support For Solar? A Survey On Perceptions, Preferences, And Priorities, Alexis Pascaris, Chelsea Schelly, Mark Rouleau, Joshua Pearce

Michigan Tech Publications, Part 1

Agrivoltaic systems integrate agricultural production with solar photovoltaic electricity generation. Given the proven technical, economic, and environmental co-benefits provided by agrivoltaic systems, increased proliferation is anticipated, which necessitates accounting for the nuances of community resistance to solar development on farmland and identifying pathways for mitigation. Minimizing siting conflict and addressing agricultural communities’ concerns will be key in continued deployment of agrivoltaics, as localized acceptance of solar is a critical determinant of project success. This survey study assessed if public support for solar development increases when energy and agricultural production are combined in an agrivoltaic system. Results show that 81.8% of …


Extending The Low-Temperature Operation Of Sodium Metal Batteries Combining Linear And Cyclic Ether-Based Electrolyte Solutions, Haoyu Zhu, Hui Xiong Aug 2022

Extending The Low-Temperature Operation Of Sodium Metal Batteries Combining Linear And Cyclic Ether-Based Electrolyte Solutions, Haoyu Zhu, Hui Xiong

Materials Science and Engineering Faculty Publications and Presentations

Nonaqueous sodium-based batteries are ideal candidates for the next generation of electrochemical energy storage devices. However, despite the promising performance at ambient temperature, their low-temperature (e.g., < 0 °C) operation is detrimentally affected by the increase in the electrolyte resistance and solid electrolyte interphase (SEI) instability. Here, to circumvent these issues, we propose specific electrolyte formulations comprising linear and cyclic ether-based solvents and sodium trifluoromethanesulfonate salt that are thermally stable down to −150 °C and enable the formation of a stable SEI at low temperatures. When tested in the Na||Na coin cell configuration, the low-temperature electrolytes enable long-term cycling down to −80 °C. Via ex situ physicochemical (e.g., X-ray photoelectron spectroscopy, cryogenic transmission electron microscopy and atomic force microscopy) electrode measurements and density functional theory calculations, we investigate the mechanisms responsible for efficient low-temperature electrochemical performance. We also report the assembly and testing between −20 °C and −60 °C of full Na||Na3V2(PO4)3 coin cells. The cell tested at −40 °C shows an initial discharge capacity of 68 mAh g−1 with a capacity retention of approximately 94% after 100 cycles at 22 mA g−1.


Identification Of Lithocholic Acid As A Molecular Glass Host For Room-Temperature Phosphorescent Materials, John J. Flynn, Zachary M. Marsh, Douglas M. Krein, Steven M. Wolf, Joy E. Haley, Erick S. Vasquez, Thomas M. Cooper, Nicholas P. Godman, Tod A. Grusenmeyer Aug 2022

Identification Of Lithocholic Acid As A Molecular Glass Host For Room-Temperature Phosphorescent Materials, John J. Flynn, Zachary M. Marsh, Douglas M. Krein, Steven M. Wolf, Joy E. Haley, Erick S. Vasquez, Thomas M. Cooper, Nicholas P. Godman, Tod A. Grusenmeyer

Chemical and Materials Engineering Faculty Publications

Lithocholic acid was identified as a molecular glass host material for room temperature phosphorescent (RTP) chromophores. Differential scanning calorimetry (DSC) was performed on a series of structurally similar, biologically sourced molecules, including lithocholic acid, β-estradiol, cholesterol, and β-sitosterol, in an effort to identify new amorphous molecular glasses independent of plasticizing additives. DSC analysis revealed lithocholic acid and β-estradiol form stable molecular glasses post thermal processing unlike neat cholesterol and β-sitosterol. The ability of lithocholic acid and β-estradiol to stabilize high wt. % loadings of d10-pyrene and a mixture of d10-pyrene and an iridium chromophore, bis(2,4-difluorophenylpyridinato)-tetrakis(1-pyrazolyl)borate iridium(III) (FIr6), was also investigated. …


Could The Inclusion Of Certain Building Information And Modelling Aspects Into The Leaving Certificate Engineering Syllabus, Aid The Transition Of Students Into Third Level Education, When Choosing A Course Within The Construction Industry, Joseph Boyle, Deborah M. Brennan Aug 2022

Could The Inclusion Of Certain Building Information And Modelling Aspects Into The Leaving Certificate Engineering Syllabus, Aid The Transition Of Students Into Third Level Education, When Choosing A Course Within The Construction Industry, Joseph Boyle, Deborah M. Brennan

Capstone Reports

The paper investigates the effects of implementing several Building Information and Modelling (BIM) aspects into the Leaving Certificate Engineering Syllabus and examines the impact this has on students choosing third level Architectural Engineering and Construction (AEC) industry courses with the desire of improving the shortage in the sector. The method and content of the study was based on academic research on second level education in other European countries through the lens of a Literature Review. A sixteen-week pilot program was trialed with over one hundred students at Senior Cycle. The outcomes of the study were critically evaluated through stakeholder interviews …


Removal Of Selenium And Heavy Metals From Coal Combustion Residuals Wastewater Using Surface Modified Iron Based Media, Madan Tandukar, Alex Korff, Andrew Vincent, Chris Hardin Aug 2022

Removal Of Selenium And Heavy Metals From Coal Combustion Residuals Wastewater Using Surface Modified Iron Based Media, Madan Tandukar, Alex Korff, Andrew Vincent, Chris Hardin

World of Coal Ash Proceedings

No abstract provided.


Study On Road Performance Of High Content Phosphogypsum Cement Stabilized Red Clay, Yang Dezhong, Chen Kaisheng, Li Qiang Aug 2022

Study On Road Performance Of High Content Phosphogypsum Cement Stabilized Red Clay, Yang Dezhong, Chen Kaisheng, Li Qiang

Journal of China & Foreign Highway

In response to the waste of phosphogypsum resources and engineering characteristics of red clay, by referring to the mix ratio design method of fly ash mixtures, 18 sets of mix ratio samples were set up indoors. By conducting compaction tests, seven-day unconfined compression strength tests, water-stability tests, and CBR tests, exploratory research was conducted on the road performance of high content phosphogypsum stabilized red clay. The results indicate that the optimal water content of high content phosphogypsum stabilized red clay is lower than that of plain red clay. The seven-day unconfined compression strength is 1.8-3.7 times that of plain red …


Preface Of Volume 1 Issue 1 On Journal Of Materials Exploration And Findings (Jmef), Jaka Fajar Fatriansyah Aug 2022

Preface Of Volume 1 Issue 1 On Journal Of Materials Exploration And Findings (Jmef), Jaka Fajar Fatriansyah

Journal of Materials Exploration and Findings

No abstract provided.


The Optimization Of Failure Risk Estimation On The Uniform Corrosion Rate With A Non-Linear Function, Fernanda Hartoyo, Jaka Fajar Fatriansyah, Imam Abdillah Mas'ud, Farhan Rama Digita, Hanna Ovelia, D. Rizal Asral Aug 2022

The Optimization Of Failure Risk Estimation On The Uniform Corrosion Rate With A Non-Linear Function, Fernanda Hartoyo, Jaka Fajar Fatriansyah, Imam Abdillah Mas'ud, Farhan Rama Digita, Hanna Ovelia, D. Rizal Asral

Journal of Materials Exploration and Findings

Failures in the oil and gas pipeline system are conditions that must be avoided and anticipated because the losses due to the failures can occur at a very high level. Internal corrosion is one of the significant causes of the failures in pipeline systems. In addition, this type of corrosion is due to the high content of carbon dioxide and other corrosive substances in crude oil and natural gas. Therefore, an optimal inspection scheduling system is required to prevent the possibility of pipeline failures due to corrosion and to avoid any overspending on the budget due to excessive inspection scheduling. …


Material Selection Of Below-Knee Leg Prosthetics, Raihan Kenji Rizqillah Aug 2022

Material Selection Of Below-Knee Leg Prosthetics, Raihan Kenji Rizqillah

Journal of Materials Exploration and Findings

The effort to select the best pylon material, part of below-knee leg prosthetic, has been performed. It begins with function analysis to generate design requirement, which concludes that the objective is to select material that gives proper mechanical properties with lowest weigth and cost. Constraint requirements eliminate unsuitable material. Material indices, a scoring function, are derived from objective with respect to a function, and used for ranking material candidates. Ranking from material indices gives top material candidates of woods. Al alloy, Mg alloy, and ferrous alloy. Further seek of documentation is undertaken by failure analysis, value analysis, fabrication, and environmental …


Investigating Features And Output Correlation Coefficient Of Natural Fiber-Reinforced Poly(Lactic Acid) Biocomposites, Andreas Federico, Siti Norasmah Surip, Wan Nor Raihan Wan Jaafar, Jaka Fajar Fatriansyah, Agrin Febrian Pradana Aug 2022

Investigating Features And Output Correlation Coefficient Of Natural Fiber-Reinforced Poly(Lactic Acid) Biocomposites, Andreas Federico, Siti Norasmah Surip, Wan Nor Raihan Wan Jaafar, Jaka Fajar Fatriansyah, Agrin Febrian Pradana

Journal of Materials Exploration and Findings

Polylactic acid (PLA) material has the potential to be applied in various industrial fields, but this material has shortcomings in terms of mechanical properties, especially mechanical strength, due to brittleness nature of PLA. The manufacture of PLA composite material with the addition of natural fibers as a reinforcing phase is one of the methods to increase the impact strength and maintain the biodegradable properties of the material. However, in theory, there are many factors that affect the mechanical properties of composite materials, thus making the mechanical properties of composites more complex than monolithic materials. The mechanical properties of these composite …


The Effect Of Sample Placement In The Furnace During The Heat Treatment Process Of 7075-T6 Aluminum Alloy On Microstructure, Hardness, And Electrical Conductivity, Donanta Dhaneswara, Hardi Rindharto, Muhammad Syauqi Aqilafif Aug 2022

The Effect Of Sample Placement In The Furnace During The Heat Treatment Process Of 7075-T6 Aluminum Alloy On Microstructure, Hardness, And Electrical Conductivity, Donanta Dhaneswara, Hardi Rindharto, Muhammad Syauqi Aqilafif

Journal of Materials Exploration and Findings

This paper reports the effects of sample placement during the heat treatment on the microstructural morphology and mechanical properties of 7075 Al alloy such as hardness value and electrical conductivity. The material was in the formed of Al alloy sheets where samples were machined into a square with dimensions of 1.5 x 1.5 inch. The 7075-T0 Al alloy as samples were given heat treatment by precipitation hardening (aging) at temperature 120°C for 24 hours, so it becomes 7075-T6 Al alloy. Samples were subjected to some mechanical tests and the morphology of the resulting microstructures were characterized by optical microscopy. The …


Modeling The Effects Of Mechanical Loading On Hypertrophic Cardiomyopathy Pathogenesis In Human Induced Pluripotent Stem Cell Derived Micro Heart Muscle, Jingxuan Guo Aug 2022

Modeling The Effects Of Mechanical Loading On Hypertrophic Cardiomyopathy Pathogenesis In Human Induced Pluripotent Stem Cell Derived Micro Heart Muscle, Jingxuan Guo

McKelvey School of Engineering Graduate Student Theses & Dissertations

Sudden cardiac death in the young is devastating. Advances in genetics have associated mutations in the contractile sarcomere apparatus of cardiomyocytes with hypertrophic cardiomyopathy, the most frequent cause of sudden cardiac death in the young. Currently, it is challenging to predict genotype-phenotype relationships in hypertrophic cardiomyopathy due to its incomplete disease penetrance. For example, different patients from the same family with identical genomic variants develop different symptoms. Non-genetic, environmental factors such as blood pressure are critical in heart function and disease. Therefore, understanding how mechanical factors contribute to phenotypes in diseases like hypertrophic cardiomyopathy is critical for developing effective therapeutics. …


Contents, Jaka Fajar Fatriansyah Aug 2022

Contents, Jaka Fajar Fatriansyah

Journal of Materials Exploration and Findings

No abstract provided.


Synthesis And Consolidation Of Metal Oxide Nanocrystals Via Nonthermal Plasma, Austin Cendejas Aug 2022

Synthesis And Consolidation Of Metal Oxide Nanocrystals Via Nonthermal Plasma, Austin Cendejas

McKelvey School of Engineering Graduate Student Theses & Dissertations

Nonthermal plasmas offer a unique nonequilibrium environment that has been leveraged in a wide variety of applications in the fields of material processing, lighting, and waste management to name a few. In all of these cases, the plasma serves as a source of high energy electrons, ions, reactive gas species, and radicals that interact in several ways with surfaces brought into contact with the plasma. Specifically, nonthermal plasmas have been shown to be very successful in achieving continuous, high-throughput, monodisperse nanocrystals of a wide variety of materials. The crystallinity of nanoparticles synthesized in nonthermal plasmas can be attributed to the …


Plasmonic Nanomaterials-Based Point-Of-Care Biosensors, Rohit Gupta Aug 2022

Plasmonic Nanomaterials-Based Point-Of-Care Biosensors, Rohit Gupta

McKelvey School of Engineering Graduate Student Theses & Dissertations

Point-of-care (POC) biosensors, although rapid and easy-to-use, are orders magnitude less sensitive than laboratory-based tests. Further they are plagued by poor stability of recognition element thus limiting its widespread applicability in resource-limited settings. Therefore, there is a critical need for realizing stable POC biosensors with sensitivity comparable to gold-standard laboratory-based tests. This challenge constitutes the fundamental basis of this dissertation work– to expand access to quality and accurate biodiagnostic tools. At the heart of these solutions lies plasmonic nanoparticles which exhibit unique optical properties which are attractive for label-free and labelled biosensors.Firstly, we improve the stability and applicability of label-free …


Soft Electronics And Sensors For Wearable Healthcare Applications, Li-Wei Lo Aug 2022

Soft Electronics And Sensors For Wearable Healthcare Applications, Li-Wei Lo

McKelvey School of Engineering Graduate Student Theses & Dissertations

Wearable electronics are becoming increasingly essential to personalized medicine by collecting and analyzing massive amounts of biological signals from internal organs, muscles, and blood vessels. Conventional rigid electronics may lead to motion artifacts and errors in collected data due to the mismatches in mechanical properties between human skin. Instead, soft wearable electronics provide a better platform and interface that can form intimate contact and conformably adapt to human skin. In this respect, this thesis focuses on new materials formulation, fabrication, characterization of low-cost, high sensitivity and reliable sensors for wearable health monitoring applications.

More specifically, we have studied the silver …


Design Of Multi-Principal Element Materials Using A Combination Of First-Principles Calculations And Machine Learning, Zhaohan Zhang Aug 2022

Design Of Multi-Principal Element Materials Using A Combination Of First-Principles Calculations And Machine Learning, Zhaohan Zhang

McKelvey School of Engineering Graduate Student Theses & Dissertations

Multiple-principal element materials, including alloys (MPEAs), oxides and other compounds combine several elements on a sub-lattice, which increases the configurational entropy and contributes to their thermodynamic stability. The vast combinatorial design space of multi-principal element materials gives rise to diverse microstructures and unprecedent combination of properties. It also poses a challenge—how to rapidly screen MPEAs with stability and properties for targeted applications. Furthermore, fundamental composition-structure-property relationships in MPEAs are currently missing. In this dissertation, I have used MPEAs as a representative system and investigated the role of chemical composition on their phase-stability and mechanical properties. With a combination of first-principles …


The Generation And Transport Of Charged Aerosols: Fundamental Study And Applications In Medicine And Energy Conversion, Hao Zhou Aug 2022

The Generation And Transport Of Charged Aerosols: Fundamental Study And Applications In Medicine And Energy Conversion, Hao Zhou

McKelvey School of Engineering Graduate Student Theses & Dissertations

Charged aerosols have significant implications in the field of functional material synthesis, pharmaceutical coating, and drug delivery. Electrospray systems are an effective methodology for generating highly charged monodispersed droplets in the size range from nanometer to micrometer. The prediction of surface charge, size and morphology of nanoparticles resulting from charged droplets are highly required for the precise control of nanoparticle properties and their effective utilization. However, the evolution of charged droplet is not well understood due to the existence of coulombic fission and ion evaporation processes. Thus, the goal of this dissertation is to elucidate how the precursor properties and …


Effects Of Cyclic Intercritical Annealing On Strength-Ductility Combinations In Medium Manganese Steels, Dawn Van Iderstine Aug 2022

Effects Of Cyclic Intercritical Annealing On Strength-Ductility Combinations In Medium Manganese Steels, Dawn Van Iderstine

Theses and Dissertations

Intercritically annealed medium manganese steels are a promising third-generation advanced high-strength steel candidate, relying on large fractions of Mn-enriched retained austenite for excellent strength-ductility combinations. The present study proposes a novel cyclic intercritical annealing to promote nucleation and efficient stabilization of austenite in a medium Mn microstructure. Design of the heat treatment is driven by the hypothesis that the distribution of ductile austenite is key in mitigating the strain incompatibility that accelerates failure in these steels. Development and preliminary testing of the heat treatment are first detailed and compared with literature results for equivalent isothermal annealing. The effects of cyclic …


Ferrous Alloy Manufacturing For The Martian Surface Through In-Situ Resource Utilization With Ionic Liquids Harvested Iron And Bosch Process Carbon, Blake C. Stewart Aug 2022

Ferrous Alloy Manufacturing For The Martian Surface Through In-Situ Resource Utilization With Ionic Liquids Harvested Iron And Bosch Process Carbon, Blake C. Stewart

Theses and Dissertations

As research continues for the habitation of the Lunar and Martian surfaces, the need for materials for construction of structural parts, mechanical components, and tools remains as a major milestone. The use of in-situ resource utilization (ISRU) techniques is critical due to the financial, physical, and logistical burdens of sending supplies beyond low-Earth orbit. The Bosch process is currently in development as a life support system at the National Aeronautics and Space Administration’s (NASA) Marshall Space Flight Center (MSFC) to regenerate oxygen (O2) from metabolic carbon dioxide (CO2) with the byproduct of elemental carbon (C). The Bosch process presents a …


Initial Exploration Of Reduced Gyrations For Arkansas Asphalt Mix Designs, Jocie L. Baker Aug 2022

Initial Exploration Of Reduced Gyrations For Arkansas Asphalt Mix Designs, Jocie L. Baker

Graduate Theses and Dissertations

The most common distresses in asphalt pavement are cracking and rutting. These distresses plague almost every asphalt roadway in the world. Finding ways to mitigate these distresses will improve the performance of asphalt pavements. One way to combat the premature cracking of asphalt in the field is to ensure there is enough asphalt binder within the mix. This will help the flexibility of the asphalt undergoing large loads and deformation. However, it is widely accepted that mix designs across the country lack the appropriate amount of asphalt binder in their mixes, causing dry mix designs that are subject to cracking …


Study Of Electron Energy Filtering For Cold Electron Transport At Room Temperature, Pushkar Kiran Gothe Aug 2022

Study Of Electron Energy Filtering For Cold Electron Transport At Room Temperature, Pushkar Kiran Gothe

Material Science and Engineering Dissertations - Archive

The Fermi-Dirac thermal excitation of electrons at room temperature has been a significant limitation to many technologically important phenomena such as single electron transport. The electron thermal excitation also degrades the performance of modern electronic devices as well as spintronic devices. The scaling of metal-oxide-semiconductor field-effect transistors (MOSFETs) is hindered due to the thermal excitation of electrons at room temperature. Suppression of the thermally excited electrons at room temperature would therefore enable further scaling of the transistors, and in turn, improve the performance of electronic devices. This study demonstrates the suppression of electron thermal excitation at room temperature without using …


Hierarchical Microstructures To Overcome The Conflict Between Strength And Toughness Of Hard Coatings: Tin/Ni As A Model System, Ignacio Lopez Cabanas Aug 2022

Hierarchical Microstructures To Overcome The Conflict Between Strength And Toughness Of Hard Coatings: Tin/Ni As A Model System, Ignacio Lopez Cabanas

Material Science and Engineering Dissertations - Archive

In the recent times, industry's production speed has been increasing and thus, the production of parts needs to adapt and so do the materials used to manufacture them. Hence, tools exposed to more extreme conditions using hard coatings need them to be more reliable. In this work an improvement of the toughness of TiN/Ni coatings is achieved through the combination of different microstructures at different levels. This first part consisted on finding the optimum TiN/Ni composition by using a high throughput methodology for a faster analysis and the second on the combination of that composition with a multilayer structure to …


Modeling Hierarchical Porous Electrodes With Tailored Anisotropic Structure, Debanjan Sarker Aug 2022

Modeling Hierarchical Porous Electrodes With Tailored Anisotropic Structure, Debanjan Sarker

All Theses

Modern electric vehicles and consumer electronics applications demand high specific energy from Li-ion batteries, which can be charged and discharged faster. In the search for high specific energy, researchers have tried to make thicker battery electrodes which contain a greater proportion of active material. While chemical and structural modification of electrodes can help to increase the electronic conductivity of active material, the microstructure of porous electrodes can be engineered to enhance ion transport for fast charge and discharge. Previous research has shown that macropores introduced by directional freeze tape casting can enhance the performance of thick porous electrodes. For instance, …


Elevated Temperature Thermal Properties Of Zrb2-B4c Ceramics, Eric W. Neuman, Matthew Thompson, William Fahrenholtz, Gregory E. Hilmas Aug 2022

Elevated Temperature Thermal Properties Of Zrb2-B4c Ceramics, Eric W. Neuman, Matthew Thompson, William Fahrenholtz, Gregory E. Hilmas

Materials Science and Engineering Faculty Research & Creative Works

The elevated temperature thermal properties of zirconium diboride ceramics containing boron carbide additions of up to 15 vol% were investigated using a combined experimental and modeling approach. The addition of B4C led to a decrease in the ZrB2 grain size from 22 µm for nominally pure ZrB2 to 5.4 µm for ZrB2 containing 15 vol% B4C. The measured room temperature thermal conductivity decreased from 93 W/m·K for nominally pure ZrB2 to 80 W/m·K for ZrB2 containing 15 vol% B4C. The thermal conductivity also decreased as temperature increased. For nominally pure ZrB2, the thermal conductivity was 67 W/m·K at 2000 °C …


Superhard Single-Phase (Ti,Cr)B2 Ceramics, Lun Feng, William Fahrenholtz, Gregory E. Hilmas, Laura Silvestroni Aug 2022

Superhard Single-Phase (Ti,Cr)B2 Ceramics, Lun Feng, William Fahrenholtz, Gregory E. Hilmas, Laura Silvestroni

Materials Science and Engineering Faculty Research & Creative Works

A nominally pure and dense (Ti0.9Cr0.1)B2 ceramic was produced by spark plasma sintering of powders synthesized by boro/carbothermal reduction of oxides. The synthesized powders were a single phase and had an average particle of 0.4 ± 0.1 μm and an oxygen content of 1.2 wt%. Average Vickers hardness values of the resulting ceramics increased from 25.9 ± 0.8 GPa at a load of 9.81 N, to 46.3 ± 0.8 GPa at a load of 0.49 N. Compared to the nominally pure TiB2 ceramic obtained under the same processing conditions, the (Ti0.9Cr0.1)B2 ceramic had higher values under the same load due …


Sub-Bandgap Photon-Assisted Electron Trapping And Detrapping In Algan/Gan Heterostructure Field-Effect Transistors, Andrew Gunn Aug 2022

Sub-Bandgap Photon-Assisted Electron Trapping And Detrapping In Algan/Gan Heterostructure Field-Effect Transistors, Andrew Gunn

All Theses

We have investigated photon-assisted trapping and detrapping of electrons injected from the gate under negative bias in a heterostructure field-effect transistor (HFET). The electron injection rate from the gate was found to be dramatically affected by sub-bandgap laser illumination. The trapped electrons reduced the two-dimensional electron gas (2DEG) density at the AlGaN/GaN heterointerface but could also be emitted from their trap states by sub-bandgap photons, leading to a recovery of 2DEG density. The trapping and detrapping dynamics were found to be strongly dependent on the wavelength and focal position of the laser, as well as the gate bias stress time …