Materials Science and Engineering Commons^™

Masking Material As A Form Of Food Storage In Tiarinia Cornigera And Micippa Platipes (Brachyura, Majidae), J. Kyomo

Tanzania Journal of Science

Masking or decorating, which means attaching materials to the body, was investigated in two spider crabs Tiarinia cornigera and Micippa platipesin the subtropical waters of Okinawa, Japan. This life strategy was compared between sites over a period of time. All crabs of different ages and sizes attached materials, in one combination or the other, on their bodies proportionate to their carapace sizes. Older or larger crabs had their carapaces more completely covered with the materials than young or smaller crabs. Similar materials were found at all sites and had equal selective precedences by crabs. Red algae, particularly Gelidiella sp, was …

Properties Of Fired Bodies Made From Tanzanian Talc-Clay Mixes For Ceramic Applications., E. H. J. Lugwisha

Tanzania Journal of Science

Fired properties of talc-clay mixed bodies of different compositions were investigated for ceramic applications. Clays from Pugu and Malangali and talcs from two different sites in Kikombo deposits in Dodoma Region were used. Chemical analyses, X-ray analysis and Differential Thermal analysis for clays and talcs were used for the characterisation. Moulded mixed samples of clay and talc dried at room temperature at 1100C for 24 hours were fired at 1200, 1250, 1300 and 13500C for 6 hours. Both clay deposits consist mainly of kaolin. Talc1 - T1 is of higher purity than Talc - T2. Furthermore, the percentage shrinkage of …

Evidence Of Long-Wavelength Collective Excitations In Magnetic Superlattices, Nikolay I. Polushkin, Steven A. Michalski, Lanping Yue, Roger D. Kirby

Materials Research Science and Engineering Center: Faculty Publications

We report on a mechanism of dynamic dipolar coupling in magnetic superlattices via long-wavelength nonevanescent fields. In the spin excitation spectra of our heterophase stripe structures, such interactions mediate a singlet ↔ doublet crossover in the frequency regime driven by the orientation of an external static field. This crossover is a new feature observed in collective behavior of superlattices, though there is some analogy of this phenomenon with birefringence taking place in optical superlattices. We envision applying the collective effects described here in microwave photonic devices.

Use Of Friction Stir Processing And Friction Stir Welding For Nitinol Medical Devices, Blair London, Murray Mahoney, Alan Pelton

Materials Engineering

Metallic materials may be joined utilizing a friction stir processing technique. The friction stir processing technique utilizes a shaped, rotating tool to move material from one side of the joint to be welded to the other without liquefying the base material.

Optimizing Production Methods For Artifical Silk Proteins Through Bioreactor And Purification Studies Of Recombinant Proteins Expressed From Pichia Pastoris, Aaron Ramey

All Theses

Advancements in the field of biomaterials are being made to produce an artificial silk fiber. A gene was constructed which utilized components from both the dragline silk of Nephila clavipes and nematode collagen. For this engineered protein, the yeast strain Pichia pastoris was chosen to be the host organism. Previous research has shown P. pastoris to have comparatively low amounts of specific protein productivity. Therefore, this problem must be compensated for by obtaining extremely high cell densities. The main focus of this study was to optimize the fermentation parameters of transgenic yeast cultures within a bioreactor in order to increase …

Influence Of Temperature And Polymer/ Mold Surface Interactions On Micro-Feature Replication At Ambient Pressure In Micro Injection Molding, Varun Thakur

All Theses

This study assesses micro-feature replication at elevated mold temperature and ambient pressure using a variety of polymers. Moldings were made on the surface of stainless steel and silicon wafers containing features as small as 130 nm under isothermal conditions in a heated chamber by allowing polymer to spread over the features at ambient pressure. Feature replication was analyzed via AFM and SEM. Polymer behavior was characterized via melt contact angle and melt viscosity. While feature detail was well replicated, the moldings exhibited poor dimensional accuracy due to shrinkage. In general, polymers with low viscosity and surface tension comparable to the …

Dielectric Properties And Method Of Characterizing Ceramic Powders And Multiphase Composites, Ravi Kiran Kota

All Theses

Barium Titanate was the first developed ferroelectric ceramic material and even today it is widely used. It is also a well-known material used for capacitors. The only reason behind a wide range of applications is that barium titanate boasts of high dielectric properties. A phase transition from cubic to tetragonal at normal working temperatures provides enhanced dielectric properties in this electronic material. For any application and design, the most inquired property is the dielectric constant. Predicting the dielectric constant is very much required as it is the pre-requisite. This is the major objective of the present work. To estimate the …

College Of Engineering Senior Design Competition Fall 2006, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.

The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects …

Thermal Failure Mechanism And Voltammetry Metrology For Cu/Barrier/Low K Integration, Dongmei Meng

Material Science and Engineering Dissertations - Archive

The present study investigates the thermal stability of Cu/barrier/porous low κ (PLK) integration first, and then a new characterization method based on voltammetry is developed to characterize quality of diffusion barrier and pore structure in low κ materials and its thermal stability. The study of thermal stability reveals that Cu/barrier/PLK interconnect fails by Cu out-diffusion through the defects of diffusion barrier into the PLK structure, which is driven by oxidation and stress gradient within the interconnect structure. The failure appears to be triggered by defects in diffusion barrier, however, such defects are not effectively detected by TEM observation due to …

Preparation And Characterization Of Properties Of Electrodeposited Copper Oxide Films, Longcheng Wang

Material Science and Engineering Dissertations - Archive

Copper oxides, including cuprous oxide and cupric oxide, are prepared by electrochemical deposition. The structural, optical and electrical properties of as-deposited copper oxides are evaluated, based on which cuprous oxide is selected as a promising material for photovoltaic applications. Electrodeposited cuprous oxide is a p-type semiconductor with a direct band gap of 2.06 eV. The mechanism of how pH affects the structural and electrical properties of electro-deposited cuprous oxide films is studied. In the pH range of 7.5 to 12.0, there are three different preferred crystal orientations: (100), (110) and (111). With different orientations, cuprous oxide shows different surface morphology …

Micromechanical Analysis Of Yielding For Particulate Filled Composites, Chih-Ta Chen

Material Science and Engineering Theses - Archive

Particulate filled composites are hybrid materials which consist of particulates held together by a matrix. In this thesis, a simulation method to obtain overall failure criterion for particulate filled composites based on the computer software "MATHEMATICA" will be presented. The composite is assumed to fail at the matrix just outside the inclusion. By Self-Consistent Method, the composite can be imaged as an inclusion embedded within effective matrix. The Equivalent Inclusion method is then applied to stimulate the stress field within the inclusion. Stress just outside inclusion can be calculated because interfacial traction force on the boundary of inclusion is continuous. …

Investigation On The Mechanism Of Interface Electromigration (Em) In Copper (Cu) Thin Films, Jee Yong Kim

Material Science and Engineering Dissertations - Archive

This study concerns the mechanism of the interface electromigration (EM) in copper (Cu) thin films. While EM in Cu is one of the most concerned reliability failure phenomena in Cu interconnects used microelectronic devices, its mechanism is not well understood yet. In order for better understanding of the EM mechanism, this study attempt to investigate the interface EM mechanism by examining the passivation effects on Cu EM using a cross-strip structure where Cu lines are cross-stripped with different passivation layers. From the observation of the marker polarity (hillocks and voids), the interface EM mechanism is determined whether the passivation layer …

Titanium Alloyed With Boron, Seshacharyulu Tamirisakandala, Daniel B. Miracle, Raghavan Srinivasan, Jay S. Gunasekera

Mechanical and Materials Engineering Faculty Publications

Small additions of boron to conventional titanium alloys have been found to produce significant changes to the microstructures and associated properties. Grain refinement and improved strength and stiffness are first-order effects, which lead to possibilities for developing novel and affordable processing methodologies and to enhance performance over conventional titanium alloys. In this article, we introduce this new class of titanium alloys and describe unique formability benefits achieved via engineering microstructures.

An Experimental Comparison Of Dimensional And Strength Characteristics Of American And Chinese Manufactured Fasteners, Michael Bailey Stroup

All-Inclusive List of Electronic Theses and Dissertations

This research investigated the quality and strength characteristics ofboth American and Chinese manufactured fasteners. The purpose of this research was to determine if there is a significant statistical difference between both manufacturers dimensional and tensile strength characteristics as to the American National Standards Institute's specified tolerances. The researcher selected the independent samples t-test to analyze the raw data collected from the experiment. SPSS 13.0 statistical analysis software was used to determine the degree of correlation between the independent variables: fastener dimensions, and ultimate tensile strengths. The researcher involved utilizing a calibrated micrometer that was capable to producing measurements to the …

Effect Of Decarburization On Microstructure Of Dc-Plasma Nitrided H 13 Tool Steel, P Visuttipitukul, C Paa-Rai, K Hideyuki

Journal of Metals, Materials and Minerals

Decarburization may occur during heat treatment of H13 steel resulting in carbon deficiency near the specimen surface. Microstructures and properties of H13 tool steel after surface treatment such as plasma nitriding can be affected by decarburization. This study is focused on the microstructure of plasma nitrided H13 steel. Decarburized and non-decarburized H13 steel was plasma nitrided for 36-72 ks at temperatures varying from 773 to 823 K. The microstructure of the plasma nitrided layer was analyzed by an optical microscope and Electron Probe Micro Analysis (EPMA). The thickness of the nitriding layer is measured. The microstructures of the decarburized and …

Techniques To Improve Coating Adhesion Of Superhard Coatings, N Panich, P Wangyao, N Vattanaprateep, S Yong

Journal of Metals, Materials and Minerals

This work addresses the development of different techniques in fabricating TiB2 coatings with increased adhesion to the substrate and with retained high hardness. Titanium diboride (TiB2) coatings were deposited on high-speed steel substrates by magnetron sputtering of a TiB2 target. Attempts to enhance the coating adhesion to the substrate of the TiB2 coatings by controlling the deposition conditions and parameters are presented, such as effect of substrate rotation; annealing temperature; using deposited Cr as an interlayer material and Ti/TiB2 multilayer system. The structure of the coatings was examined by X-ray diffraction, field-emission scanning electron microscopy, and atomic force microscopy. The …

Transparent Coating Materials Based On Inorganic/Organic Composites, K Srikulkit, N Rojtinnakorn, R Charoensak

Journal of Metals, Materials and Minerals

A siloxyl group functionalized copolymer of low molecular weight was synthesized, aiming at preparing transparent inorganic/organic coating composites. Two types of coating systems were investigated: two-component system (based on functionalized copolymer-HMMM) a three-component system (based on functionalized copolymer-HMMM-TEOS). Their properties were investigated and compared. Coating films obtained from these systems exhibited good optical clarity, which was largely dependent on the content of indicated Materials. For instance, to prevent phase separation in the 3- component system, TEOS was "effectively" linked to pendent siloxyl groups on the organic moiety Hence, coating formulations containing a high degree of pendent siloxyl groups exhibited better …

Ph Dependant Coating For Microfluidics Devices, L Limsavarn, C Panithipongwut, P Thongkorn, S T. Dubas

Journal of Metals, Materials and Minerals

The layer-by-layer technique was used to coat the channels of PDMS microfluidics devices. The coating was based on the sequential deposition of polydiallyldimethylammonium chloride (PDADMAC) with a copolymer of polystyrene sulfonate and maleic acid (CoPSS-Maleic) into polyelectrolyte multilayer (PEM). The possible deposition of PEM coating on PDMS was confirm by contact angle which showed the clear transformation of the PDMS surface from hydrophobic to hydrophilic. The later deposition of the PEM coating inside the micro-channels was confirmed by change in electroosmotic flow direction (EOF) and intensity as a function of the number of deposited layers. The EOF measurements revealed that …

Uv Radiation Energy Consumption In Curing Process Of Epoxidized Sunflower Oil-Organoclay Hybrid Coatings, N Jiratumnukul, R Intarat

Journal of Metals, Materials and Minerals

Epoxidized sunflower oil (ESO) can be cured with ultraviolet radiation using either cationic or hybrid initiation. The organoclay was prepared by the cationic exchange process, in which sodium ions were replaced by alkyl ammonium ions. Organoclay was incorporated into epoxidized sunflower oil UVcurable systems. The effects of diluents and types of photo initiators were studied. It was found that the formulations with a hybrid photoinitiator required less energy in the curing process than those with a cationic photoinitator. Moreover, the formulations without diluent can be cured with lower radiation energy than those with diluent.

Electrochemical Oxidation Process For Mineralization Of Solvent, A Charoensri, F Kobayashi, A Kimura, J Ishii

Journal of Metals, Materials and Minerals

A silver mediated electrochemical oxidations is a promising technique for the destruction of organic compounds. The destruction of 30%tributyl phosphate in dodecane in a nitric acid medium containing electrogenerated Ag(II) to carbon dioxide was studied by using a laboratory scale electrochemical oxidation cell. The electrolyte used in this system was 0.5 M AgNO3 in the range of 3 - 7 M HNO3, at operating temperatures of 60ºC ± 5ºC, under ultrasonic agitation and the output of a DC power supply at constant the current was 60 A, respectively. Electrolysis was carried out for 5 hours. The results show that, in …

Investigation Of The Band Structures And Optical Properties Of Super Lattices, Sheikha Ahmed Awad Alnaeme

Theses

Group III nitrides are highly attractive materials because of their great potential for the development of optoelectronic devices in short wavelength, semiconductor lasers and optical light-emitters and detectors. GaN, AlN and InN are considered as the most important compounds in this class of materials. In this work, we present a theoretical investigation of the electronic properties (band structure, density of state and contour maps of the charge density distribution) and optical properties (refractive index, absorption and dielectric constants). Also, we investigate the band structures and optical properties of AlN/GaN and InN/GaN super lattices. A full-potential linearized plane-wave (FPLAPW) method is …

Ac Conductivity Relaxation Processes In Cacu₃Ti₄O₁₂ Ceramics: Grain Boundary And Domain Boundary Effects, Wei Li, Robert W. Schwartz

Materials Science and Engineering Faculty Research & Creative Works

The ac conductivity of CaCu₃Ti₄O₁₂ ceramics associated with electrical charge carrier motion (ions or vacancies) was investigated as a function of frequency at different temperatures. The long range migration of charge carriers within the ceramic is restricted by two kinds of insulating barriers, namely, grain boundaries and domain boundaries. The potential barriers associated with these boundaries lead to two anomalies in conductivity response and three frequency-dependent contributions to conductivity: long range diffusion of carriers, carrier migration localized within grains, and carrier migration localized within domains.

Synthesis And Characterization Of Multifunctional Oxides For Force And Gas Sensors, Vaneet Sharma

Material Science and Engineering Theses - Archive

In this research work, the piezoresistivity phenomena in multifunctional oxides of La0.8Sr0.2MnO3 (LSMO) and composites of LSMO - (Ce0.12Zr0.88)O2 has been investigated for force and gas sensor applications in harsh environments including automobile and aerospace industry. In these applications, there is a need of material with high mechanical strength with multi sensing capabilities. The inherent sensing capabilities allow the material to be implemented at variety of platforms. Previously, LSMO polycrystalline ceramics have been studied as a cathode material in solid oxide fuel cells (SOFC). Owing to its colossal magnetoresistance properties, this material has also been extensively studied for use in …

Reheat Treated Microstructures And Gamma Prime Particle Coarsening Behaviour At 900˚C Of Cast Nickel Based Superalloy In-738, S Polsilapa, P Sopon, N Panich, N Chuankrerkkul, A Thueploy

Journal of Metals, Materials and Minerals

Long-term isothermal exposure tests were conducted on IN-738 alloy to evaluate the variation of gamma prime particle coarsening behavior after different rejuvenated heat treatment conditions. The longterm thermal exposure tests (up to 2,500 hours) were conducted at 900˚C to assess gamma prime particle coarsening behavior. Metallographic work had been performed on isothermally aged samples to characterize gamma prime coarsening as a function of heating time. At all investigated heating times, the gamma prime particles in all tested specimens were coarser than the initial reheat treated ones. The gamma prime particles appeared to coarsen more into a round shape or agglomerated …

The Influence Of The Strain Rate On The Material Properties Of The Zinc-Coated Sheet, Z Vadasová, M Mihaliková

Journal of Metals, Materials and Minerals

In this paper the influence of the strain rate on the material properties of the zinc-coated sheet of the thickness (1; 1.5; 1.8) mm made from low-alloyed steel ZINKODUR 340 was analyzed. Increasing the strain rate is one of the possible ways to increase cold mechanical work in products. The tensile test is the most useful method for determining the material characteristic such as ductility. This contribution analyzes the influence of loading rate in range from 1 to 1000mm/min on material characteristics of tested steel during the tensile test. Strain rate is one of the most significant factors, which affected …

The Effect Of Long-Term Thermal Exposure At Elevated Temperatures On Microstructures And Mechanical Properties In Centrifugally Casted Iron-Base Alloy, G Lothongkum, N Thaweepornkhasemsukh, P Wangyao

Journal of Metals, Materials and Minerals

This work has an aim to study and investigate the relationship between high temperature exposure conditions on microstructural evolution and mechanical properties in the iron-based alloy, Fe-30.8 Ni - 26.6 Cr alloy, strengthened by carbide precipitation. Two exposure temperatures (900 and 1000°C) with various thermal exposure times are introduced to the as-received alloy. After short-term exposure, it was found that the secondary carbides precipitated early near the primary carbides, which were chromium and niobium/titanium carbide networks. The secondary carbide precipitations were also found in the dendrite cores. The amounts of needle-like carbides and secondary carbide films increased with time and …

Development Of Flame Retardant Polyphosphoric Acid Coating Based On The Polyelectrolyte Multilayers Technique, K Srikulkit, C Iamsamai, S T. Dubas

Journal of Metals, Materials and Minerals

Polyelectrolyte multilayer (PEM) thin films were deposited on silk by sequential deposition of Chitosan and polyphosphoric acid. This PEM composition takes advantage of synergetic effect of the phosphorus and the nitrogen to provide an efficient coating, which prevents fiber decomposition at high temperature. Prior to the PEM assembly on silk fibers, the growth of the film was initially monitored using an atomic force microscopy (AFM). Films formed on silicon wafer after 10, 20, 30, 40 and 60 layers showed somewhat linear increase, which is consistent with the PEM technique. A total thickness ranging from 10 to 107 nm for the …

An Exploration Of Several Structural Measurement Techniques For Usage With Functionally Graded Materials, Robert A. Reuter

Theses and Dissertations

Titanium / titanium boride functionally graded 6"x 1"x1" beams were subjected to a four-point beam test in order to critique the value of several measurement techniques. Also, finite element analysis results were compared with experimental values and general observations about the experiment were recorded. Uniform 85% TiB /15% Ti and uniform commercially pure titanium specimens were also subjected to the same loading conditions as a control. Techniques used include digital image correlation, fiber optic strain gauging, strain gauging, and differential infrared thermography techniques. The strain data results were compared with one another and to linear finite element models. It was …

Synergistic Functions Of Trimethl Phosphate And Vinylene Carbonate As Additives For The Li-Ion Batteries, Zhi-Yuan Tang, Yan-Bing He, Quan-Sheng Song, Yu-Hong Chen, Yuan-Gang Liu, Qiang Liu

Journal of Electrochemistry

The cooperative effects of trimethl phosphate and vinylene carbonate as additives for Li-ion batteries are investigated by using the cyclic voltammetry,electrochemical impedance spectroscopy and scanning electronic micro-photographs.The results show that the combination application of TMP and VC as additives for Li-ion batteries not only enhances safety of the batteries,but also improves their cycling performance.The reason may be ascribed to firstly VC being reduced and the reduction product polymerized to form excellent solid electrolyte interface(SEI) layer on the surface of graphite electrode during the first charge and discharge process,which prevents effectively the decomposition of TMP on the surface of the graphite …

Facilitated Effect Of Ag To Oxygen Transportation In Pem Fuel Cell Air Cathodes, Hong-Feng Xu, Jian-Hua Dong, Xiang-Li Hou

Journal of Electrochemistry

Silver(Ag) was deposited in the pores of Nafion membrane by ion exchange and succedent hydrogen reduction;the structures of Nafion-Ag membrane were measured by TEM and XRD,the diffusion coefficients of oxygen in Nafion-Ag was determined by electrochemical limited current method.The results showed that after deposited silver,the pores in the Nafion were enlarged by silver grains;the oxygen diffusion coefficient was increased about four times.By introducing silver in the thin Nafion film around the cathode catalyst,the performance of PEM fuel cell have a evident increasing in high current density, which shows the facilitated effects of silver to oxygen transportation in PEM fuel cell.