Materials Science and Engineering Commons^™

Optimization Of Membrane Electrode Assembly In Air-Breathing Direct Methanol Fuel Cell, Liang Ma, Wei-Wei Cai, Jing Zhang, Liang Liang, Jian-Hui Liao, Chang-Peng Liu, Wei Xing

Journal of Electrochemistry

The structure and performance of MEA were optimized by tailoring the catalyst layer,cathodic microporous layer (MPL) ,anodic MPL and membrane,with the considerations of unique characteristics of airbreathing direct methanol fuel cell (DMFC) such as methanol crossover and cathode flooding. It was found that high catalyst loading could suppress the methanol crossover effectively,but too high catalyst loading can lead to high mass transport resistance. Hydrophobic anodic MPL with 30% (by mass) PTFE could facilitate the CO₂ bubble detachment,which decreased the methanol concentration gradient and suppressed the methanol crossover accordingly. When Nafion 115 was used as membrane,methanol crossover was severe,while Nafion …

Research On Electrochemical Performance Of Lithium-Ion Battery Cathode Material Lini(1/3)Co(1/3)Mn(1/3)O2 In Aqueous Lino3 Solution, Jun Zheng, Xin Jia, Chong Wang, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

The cathode material of LiNi_1/3Co_1/3Mn_1/3O₂ synthesized by sol-gel method shows excellent high rate performance, and high output power density during discharge process. A well-ordered layered α-NaFeO₂ structure was confirmed by XRD and a primary particle size of about 500 nm was indicated by SEM. Galvanostatic charge-discharge test indicates that LiNi_1/3Co_1/3Mn_1/3O₂ in 2 mol·L^-1 LiNO₃ aqueous solution with pH 12 reached a ca-pacity of 147 mAh/g while charged and discharged at 2C. The capacities were 64, 33, 16 mAh/g with 80C (14.4 A/g), 150C …

Fabrication Of Electrochemically Activated Glassy Carbon/Bismuth Film Electrodes For Sensitive Analysis Of Pb(2+) And Cd(2+), Kang Shi, Wen-Jing Wang, Kun Hu

Journal of Electrochemistry

The application of electrochemically activated glassy carbon (GC) in the in-situ preparing of bismuth film electrodes (BiFEs) to analyze Pb^{2 +} and Cd^{2 +} was investigated. The glassy carbon electrodes were electrochemically activated by either potentiostic or cyclic polarization in 1 mol·L^-1 NaOH solution. Experimental results show that employment of HCl solution as the analytical solution not only can reproducibly renew the electrochemically activated GC electrode surface with an electrochemical clear procedure, but also can greatly enhance the sensitivity of BiFes method for analysis of Pb^{2 +} and Cd^{2 +}. The test range thus …

Synthesis Of Cosalen Composite In Apo-5 And Its Electrocatalytic Behaviour For Reaction Of Dioxygen Reduction, Rong Zhang, Li-Hua Tang, Bin-Bin Fan, Jing-Hong Ma, Rui-Feng Li

Journal of Electrochemistry

CoAPO-5 molecular sieve was hydrothermally synthesized. The Cobalt ions in CoAPO-5 were coordinated with the SALEN ligend diffusing into the channels of the molecular sieve to form CoSALEN complexes. The electrochemical behaviors and electrocatalysis for dioxygen reduction of the CoSALEN complex immobilized in APO-5 modified glassy carbon electrodes (GCEs) have been investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in differrent pH aqueous solutions. The results showed that the PS/CoSALEN/APO-5 /GC modified electrode is of the high electrocatalytic activity towards dioxygen reduction in pH 6. 86 buffer solution with a reduced overpotential of 447 mV lower than bare GC electrode. …

Electrochemical Behaviors Of Hydrazine In Bmimpf6 Solution At Ag Electrode, Jie Sun, Yan Li, Yi-Ling Feng, Rong Wang, Xia-Qin Wu

Journal of Electrochemistry

In this work, the electrochemical behaviors of hydrazine at Ag electrode in the room temperature ionic liquid, BmimPF₆, were studied by cyclic voltammetry. Results suggested that Ag electrode showed a good catalytic activity towards hydrazine oxidation. The catalytic peak current showed a good linear relationship with the hydrazine concentration in the range of 0 ～ 3.4 mmol/L. The rate-determining step of the electrocatalytic reaction involved one electron transfer form hydrazine molecule to Ag⁺ ion.

Biodegradable Polymer Blends And Composites From Proteins Produced By Animal Co-Product Industry, Bernice Nzioki

All Theses

ABSTRACT
Development of new green materials from by-products of animal rendering industries would provide a substantial economic return to animal rendering processors. Meat and bone meal (MBM), one of the products of the rendering industry, has potential for numerous bio-based applications. This research focuses on fabrication of plastics blends made of MBM (Meat and bone meal) and UHMWPE (ultra high molecular weight polyethylene). We investigated thermal, morphological, water absorption and mechanical properties of the plastics. The plastics were compression molded and their properties were examined.
DSC thermographs of the blends indicated that the thermal properties of UHMWPE did not change …

Microstructural Evolution Of Nickel During Spark Plasma Sintering, Matthew Thomas Luke

Boise State University Theses and Dissertations

Spark plasma sintering (SPS) is reported to produce materials with properties superior to those that result from conventional processing techniques. Spark plasma sintering is also reported to process materials at lower temperatures and in a shorter time than other processes, which may facilitate the synthesis of materials that are traditionally difficult to process. While the properties of materials that result from SPS processing have been studied, there is not a thorough understanding of the evolution of the microstructure in response to SPS process parameters. A comparison of the microstructure of nickel produced by SPS at varying ramp rate, temperature, dwell …

Grain Boundary Premelting And Activated Sintering In Binary Refractory Alloys, Xiaomeng Shi

All Dissertations

Quasi-liquid intergranular film (IGF) which has been widely observed in ceramic systems can persist into sub-solidus region whereby an analogy to Grain boundary (GB) premelting can be made.
In this work, a grain boundary (GB) premelting/prewetting model in a metallic system was firstly built based on the Benedictus' model and computational thermodynamics, predicting that GB disordering can start at 60-85% of the bulk solidus temperatures in selected systems. This model quantitatively explains the long-standing mystery of subsolidus activated sintering in W-Pd, W-Ni, W-Co, W-Fe and W-Cu, and it has broad applications for understanding GB-controlled transport kinetics and physical properties. Furthermore, …

Production Of Multiwall Carbon Nanotuse For Alcohol Sensor Application., Ebtehal Saleh Alshaqaq

Student Works (2010-2019)

Multiwall carbon nanotube/polyethylene oxide (PEO), multiwall carbon nanoube/polyvinyl alcohol(PVA) and multiwall carbon nanotube/ polyvinyl alcohol(PVA)/zinc oxide(ZnO) have been tested as chemical sensors and detailed study on the effect of different gas concentration and material properties on gas sensitivity is presented. Initial composites were prepared by a simple solution casting and characterized by x-ray diffraction for ZnO, Fourier transform infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM) to demonstrate crystallite size of ZnO, the morphology and surface area respectively. On the other hand, MWCNT/PEO , MWCNT/PVA , MWCNT/PVA/ZnO were prepared with different loading MWCNT and ZnO. The chemical sensing properties of …

Standardization Of A Volumetric Displacement Measurement For Two-Body Abrasion Scratch Test Data Analysis, Ryan L. Kobrick, David M. Klaus, Kenneth W. Street Jr.

Publications

A limitation has been identified in the existing test standards used for making controlled, two-body abrasion scratch measurements based solely on the width of the resultant score on the surface of the material. A new, more robust method is proposed for analyzing a surface scratch that takes into account the full three-dimensional profile of the displaced material. To accomplish this, a set of four volume displacement metrics are systematically defined by normalizing the overall surface profile to statistically denote the area of relevance, termed the “Zone of Interaction” (ZOI). From this baseline, depth of the trough and height of the …

Mechanical Behavior Of Alloy 230 At Temperatures Relevant To Ngnp Program, Sudin Chatterjee

UNLV Theses, Dissertations, Professional Papers, and Capstones

Identification and selection of suitable structural materials for heat exchanger application within the purview of the next generation nuclear plant (NGNP) program constitute a major challenge. This challenge stems from the lack of many desired metallurgical and mechanical properties of conventional metallic materials and alloys for applications at temperatures approaching 950 oC. Nickel (Ni)-base Alloy 230 has been highly recommended as a suitable structural material for such application due to its excellent resistance to high-temperature plastic deformation and superior corrosion resistance in many hostile environments. Systematic studies on tensile, fracture toughness, creep, stress-rupture and creep-fatigue behavior of this alloy have …

Performance Of Nevada’S Aggregates In Alkali-Aggregate Reactivity Of Portland Cement Concrete, Mohammad Shahidul Islam

UNLV Theses, Dissertations, Professional Papers, and Capstones

Alkali-aggregate reaction (AAR) is a form of distress that occurs in concrete and results in serviceability problems, cracks, spalling, and other deterioration mechanisms. There are two categories of AAR, namely, alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). Alkali-silica reaction is one of the most recognized deleterious phenomena in concrete, and has been a major concern since its discovery in the 1940s. The reaction which occurs between reactive silica or silicates present in some aggregates and alkalis of Portland cement produces an alkali-silica gel that expands in the presence of moisture resulting in concrete cracks. ACR is also a chemical reaction …

Kinetic And Finite Element Modeling For Firing Brick, Daniel Mckinney

All Theses

Kinetic modeling and simulation were used to optimize the firing cycle for brick. This was done to develop a tool for the brick industry to reduce fuel consumption and emissions during firing. A kinetic model was built using shrinkage data from dilatometer measurements and mass loss data from thermogravimetry measurements in order to predict the density as a function of temperature and time. The density of brick was related to the absorption coefficient (C/B), an ASTM standard which is related to the durability of the brick. The kinetic model was used to optimize the firing curve using a rate controlled …

Characterization And Modification Of Helmet Padding System To Improve Shockwave Dissipation, Katelyn Howay

All Theses

Currently soldiers are being exposed a much higher number of improvised explosive devices (IEDs) and the resulting shockwaves. These shockwaves can cause traumatic brain injuries (TBIs) even without the occurrence of ballistic impact. The focus of this research was to reduce the amount of shockwaves soldiers are exposed to by inserting fibers and woven fabrics into a foam padding system. These fibers and fabrics facilitate the dissipation of the shockwave energy before it is able to penetrate the padding and cause TBIs.
The sound velocity of high-performance fibers, commodity fibers and woven fabric was measured using a Dynamic Modulus Tester. …

Fabrication Of Transparent Ceramic Laser Media For High Energy Laser Applications, Karn Serivalsatit

All Dissertations

Sesquioxides of yttrium, scandium, and lutetium, i.e., Y₂O₃, Sc₂O₃, and Lu₂O₃, have received a great deal of recent attention as potential high power solid state laser hosts. These oxides are receptive to lanthanide doping, including trivalent Er, Ho and Tm which have well known emissions at eye-safe wavelengths that can be excited using commercial diode lasers. These sesquioxides are considered superior to the more conventional yttrium aluminum garnet (YAG) due to their higher thermal conductivity, which is critical for high power laser system. Unfortunately, these oxides possess high …

Layer-By-Layer Assembly Of {Nanoclay-(Sol-Gel Oxide)}N And {Nanoclay-(Oxide Nanoparticle)}N Multilayers: Synthesis And Growth Mechanisms, Hao Chen

All Dissertations

Two new classes of all-inorganic nanostructured multilayers, {MMTx-(sol-gel oxide)}n and {MMTx-(oxide nanoparticle)}n, have been successfully synthesized for the first time. They were made by adapting a layer-by-layer (LbL) assembly method initially developed to synthesize polyelectrolyte-based multilayers. In most previous studies, this electrostatic-assisted LbL assembly method used polyelectrolytes/polymers as the 'structural glue' to prepare multilayers. The synthesis of {MMTx-(sol-gel ZrO2)}n multilayers demonstrates for the first time the feasibility of making sol-gel oxide 'glued' all-inorganic multilayers, thereby introducing an innovative nanoscale fabrication concept. The synthesis of {MMTx-(oxide nanoparticle)}n multilayers further illustrates the versatility of LbL assembly technique by achieving a second new …

In-Pile Thermal Conductivity Measurement Methods For Nuclear Fuels, Brandon S. Fox

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Measuring nuclear fuel thermal conductivity in-pile can provide much needed data for understanding fuel performance during irradiation and yield thermophysical property data needed for simulation codes and fuel databases. The objective of this research is to develop and compare two in-pile thermal conductivity methods in a laboratory setting using surrogate fuel materials.

A steady-state radial heat flow method was investigated to understand its viability as an in-pile steady-state thermal conductivity technique. By using Joule heating to simulate volumetric heat generation within a surrogate fuel rod, thermal conductivity was measured with two thermocouples at different radial positions within the rod. Examinations …

Hydrogen Fuel Cell Analysis: Lessons Learned From Stationary Power Generation Final Report, Scott E. Grasman, John W. Sheffield, Fatih Dogan, Sunggyu Lee, Umit O. Koylu, Angie Rolufs

Materials Science and Engineering Faculty Research & Creative Works

This study considered opportunities for hydrogen in stationary applications in order to make recommendations related to RD&D strategies that incorporate lessons learned and best practices from relevant national and international stationary power efforts, as well as cost and environmental modeling of pathways. The study analyzed the different strategies utilized in power generation systems and identified the different challenges and opportunities for producing and using hydrogen as an energy carrier. Specific objectives included both a synopsis/critical analysis of lessons learned from previous stationary power programs and recommendations for a strategy for hydrogen infrastructure deployment. This strategy incorporates all hydrogen pathways and …

Investigation Of Creep Threshold Stresses Using In Situ Tem Straining Experiment In An Al-5y2o3-10sic Composite, S. P. Deshmukh, Rajiv S. Mishra, I. M. Robertson

Materials Science and Engineering Faculty Research & Creative Works

Creep behavior of metal matrix composites is similar to dispersion strengthen alloys and characterized by the presence of a threshold stress below which the creep rate is negligible. This threshold stress is attributed, at least in dispersion-strengthened alloys, to dislocation particle interactions in which the detachment of the dislocations from the particle is the rate-limiting step. Creep experiments were performed on an Al-5Y₂O₃-10SiC composite in the temperature range of 473 and 573 K and the nature of the dislocation-particle interaction was determined by performing in situ straining experiments at elevated temperature in a transmission electron microscope. …

Crosslinked Conventional Size And Nanoparticle Size Acrylic Latexes And Their Blends: Investigation Of The Effects Of Crosslinking, Particle Size And Distribution, Glass Transition Temperature And Blending On Film Formation, Properties And Morphology, Ravi Ghanshyambhai Joshi

Master's Theses and Doctoral Dissertations

Synthetic latexes have many product applications including functioning as a binder in paints and coatings. For many years, researchers in industry as well as in academe have been exploring various strategies to improve performance of acrylic latexes mainly to replace traditionally used solvent borne coatings due to increasing environmental concerns and strict governmental regulations. The main goal of the study is to investigate the effects of type (pre-coalescence or post-coalescence) and level of crosslinking, particle size (nano particle size ~ 20-25 nm vs. conventional particle size ~ 120-130 nm) and distribution, glass transition temperature (Tg), and blending on latex film …