Materials Science and Engineering Commons^™

Nanocrystalline Piezoresistive Polysilicon Film Obtained By Aluminum Induced Crystallization For Pressure Sensing Applications, Suraj Kumar Patil

Material Science and Engineering Dissertations - Archive

The overall objective of our research was to integrate various sensors on to a single flexible substrate for multi-sensory information gathering. Additional capabilities could be incorporated towards the realization of 'smart skin' for simultaneous and real time sensing of various mechanical, biological and chemical stimuli. Recent research venues are dictated by the trend of shifting from conventional silicon (Si) substrates to lower weight, low profile, structurally robust and lower cost flexible substrates. These flexible substrates easily conform to non-planar objects, could be batch fabricated at lower cost and enable multilayer construction. This would eventually evolve into seamless assimilation of sensors …

An Investigation Of Initially Delaminated Composite Sandwich With Delamination Arrest Mechanism Under Buckling Loading, Tony D. Tran

Master's Theses

This thesis involves the development of a fiberglass-foam composite sandwich structure with the introduction of delamination arrestment keys; therefore, a study of an initially delaminated composite sandwich structure was the experimental analysis on multiple configurations in how the arrestment keys are placed.

The first part of this thesis research was to the experimental design and manufacturing of the composite sandwich plates. These plates were later cut down to the specific test dimensions and manufacturing processes for the composite sandwich plates and test specimens were created. The composite sandwich plates were manufactured using a vacuum resin infusion process. The dimensions of …

Oxidation Of Cyclohexane And Ethylbenzene By Hydrogen Peroxide Over Co-Substituted Heteropolytungstate Catalyst, W Kanjina, W Trakarnpruk

Journal of Metals, Materials and Minerals

The tetrabutylammonium salt of Co-substituted heteropolytungstate, [(n-C4H9)4N]4 HPW11Co(H2O)O39.3H2O was synthesized and characterized. It was shown to be an active catalyst for the oxidation of cyclohexane and ethylbenzene. The oxidation reactions were performed using green oxidant hydrogen peroxide and acetonitrile as solvent. The major products of the oxidation of cyclohexane were cyclohexanone (K) and cyclohexanol (A). High selectivity towards K-A oil was achieved. At longer time cyclohexanol was converted to cyclohexanone. Ethylbenzene was also selectively oxidized to acetophenone. These oxidation reactions appear to be radical processes since they were totally inhibited in the presence of radical scavenger.

Effect Of Sintering On Microstructure And Properties Of Hydroxyapatite Produced By Different Synthesizing Methods, N Monmaturapoj, C Yatongchai

Journal of Metals, Materials and Minerals

The aim of this study is to investigate the effect of the sintering schedule on microstructure and properties of hydroxyapatite which is produced by different synthesizing methods. Hence, wet-chemical precipitation and solid-state reaction were performed to prepare nano-sized hydroxyapatite (HA) powders. Powders were then uniaxially pressed and sintered by varying temperatures and times. XRD and SEM were used to identify phases and morphology. Density and porosity of the sintered sample were determined using the Archimedes technique. Flexural strength was measured by a universal testing machine. The results show that density and strength could be improved by increasing the sintering temperature …

Study On Flame Retardancy And Anti-Dripping Of Polyester Fabric Treated With Bentonite, Diammonium Hydrogen Phosphate And Aluminium Hydroxide, P Lerdkajornsuk, S Charuchinda

Journal of Metals, Materials and Minerals

The purpose of this research was to improve flame retardancy and anti-dripping of polyester fabric by using bentonite, 3% (w/w) diammonium hydrogen phosphate (DA) and 5, 10% (w/w) aluminium hydroxide (Al(OH)3) via pad-dry technique. The burning behavior of the treated polyester fabric was investigated according to ASTM D1230. The results showed that 10wt% of bentonite alone were capable of imparting anti-dripping. Nevertheless, the preparation of the slurry of bentonite (>10% (w/w)) caused high viscosity leading to difficulties for the preparation and finishing process. Thus, the addition of 4% (w/w) of sodium chloride (NaCl) to the suspension of bentonite (up …

Pickling Behavior Of Aisi 304 Stainless Steel In Sulfuric And Hydrochloric Acid Solutions, W Homjabok, S Permpoon, G Lothongkum

Journal of Metals, Materials and Minerals

Oxide scales as well as a Cr-depleted layer, which grows between the oxide scale and base metal, are formed on AISI 304 stainless steel surface during high temperature processing. Pickling is an important process which includes mechanical and chemical operations to remove oxide scales, Cr-depleted layers, and to recover the surface passivity. The multi-step pickling is commonly used because of its higher efficiency than a single step pickling. In this study, the multi-step pickling of AISI 304 stainless steel in HCl solution was investigated instead of H2SO4 solution for the first step of pickling. HF+HNO3 mixed acid is traditionally used …

Effect Of Temperature And Pressure On The Densification Of Titanium Silicide Compound, P Thapnuy, S Larpkiattaworn, T Luangvaranunt, J Ikeuchi

Journal of Metals, Materials and Minerals

Titanium silicide compound was synthesized from the mixture of titanium and silicon powder with atomic ratios of 60:40 and 70:30. The powders were mixed by ball milling and pressed by different methods: by using uniaxial pressing at 64 MPa, cold isostatic pressing (CIP) at 200 MPa, hot forging (HF) at 648 MPa, and hot pressing (HP) at 24 MPa. The samples were then sintered at 1300o C or 1600o C for 2 hours soaking time in argon atmosphere. The sintered samples were subsequently characterized for phase constitution using X-ray diffraction (XRD). Ti5Si3 was observed as main compound of mixtures with …

Effects Of Aluminium On Sintered Properties Of Cu-10wt%Sn Bearing, V Chobaomsup, T Luangvaranunt

Journal of Metals, Materials and Minerals

Self-lubricating bearings are one of the oldest industrial applications of porous powder metallurgy parts, dating back to the mid-1920s. They remain the highest part produced by the P/M industry. The objective of this research was to study the effects of sintering time, sintering temperature and ratio of adding aluminium on sintered properties of Cu-10wt%Sn bearing that was produced from powder metallurgy processing. Various physical and mechanical properties such as density, percentage of porosity and hardness were tested to elucidate the effect of processing parameters. Phase identification and microstructure were analyzed by X-Ray Diffractometer and optical microscope, respectively. Sintering times in …

Surface Modification Of Polyester Fabrics With Vinyltriethoxysilane, B Kusuktham

Journal of Metals, Materials and Minerals

Surface modification of polyester fabrics was studied aiming at improving the water repellency property. Vinyltriethoxysilane (VTES) was employed as surface modifying agent. Prior to application, VTES was prepared in aqueous emulsion using cetyltrimethylammoniun bromide (CTAB) as an emulsifying agent. The application of VTES emulsion was carried out using a padder and followed by curing at 150° C for 15 minutes. The result showed that the treated fabrics exhibited higher contact angle values when compared to untreated fabric, indicating an increase in water repellency property. It was believed that VTES was converted into silicone through siloxane network. The presence of a …

Processing And Composition Effects On The Fracture Behavior Of Spray-Formed 7xxx Series Al Alloys, Mala M. Sharma, Constance W. Ziemian, Timothy J. Eden

Faculty Journal Articles

The fracture properties of high-strength spray-formed Al alloys were investigated, with consideration of the effects of elemental additions such as zinc,manganese, and chromium and the influence of the addition of SiC particulate. Fracture resistance values between 13.6 and 25.6 MPa (m)^1/2 were obtained for the monolithic alloys in the T6 and T7 conditions, respectively. The alloys with SiC particulate compared well and achieved fracture resistance values between 18.7 and 25.6 MPa (m)^1/2. The spray-formed materials exhibited a loss in fracture resistance (KI) compared to ingot metallurgy 7075 alloys but had an improved
performance compared to high-solute powder …

Analyzing The Impact Of Reactive Transport On The Repository Performance Of Triso Fuel, Gregory Schmidt

UNLV Theses, Dissertations, Professional Papers, and Capstones

One of the largest determiners of the amount of electricity generated by current nuclear reactors is the efficiency of the thermodynamic cycle used for power generation. Current light water reactors (LWR) have an efficiency of 35% or less for the conversion of heat energy generated by the reactor to electrical energy. If this efficiency could be improved, more power could be generated from equivalent volumes of nuclear fuel. One method of improving this efficiency is to use a coolant flow that operates at a much higher temperature for electricity production. A reactor design that is currently proposed to take advantage …

College Of Engineering Senior Design Competition Fall 2010, 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 …

Chemical And Electronic Structure Of Surfaces And Interfaces In Compound Semiconductors, Sujitra Pookpanratana

UNLV Theses, Dissertations, Professional Papers, and Capstones

The interface formation between two different materials is important in applications for optoelectronic devices. Often, the success or performance of these devices is dependent on the formation of these heterojunctions. In this work, the surface and interfaces in such materials for optoelectronic devices are investigated by a suite of X-ray analytical techniques including X-ray photoelectron (XPS), X-ray excited Auger electron (XAES), and X-ray emission (XES) spectroscopies to provide novel insight.

For the group III-nitrides (e.g., AlxGa1-xN) used in many light emitting devices, a significant challenge exists to form an Ohmic contact. The electron affinities and band gaps of GaN and …

Optimizing The Mechanical Properties Of Partially Yttria Stabilized Zirconia With Alumina Additions, Ramanaganapathy Kandaswamy

All Theses

Zirconia is one of the extensively studied solid oxide ceramics with respect to its use in various industrial applications like electrolyte in fuel cells, sensors, refractories and exhaust chamber in automobile industry. It can be found from the literature 1-4 that are contradictory results on the mechanical properties when alumina is added. There are several factors like microstructure, phase composition and method of processing that affects the mechanical properties of the material. The focus of this research is to examine how hardness, tensile strength and other properties varies with alumina content and deduce the optimal amount of alumina that is …

Utilizing Copper(I) Catalyzed Azide-Alkyne Huisgen 1,3-Dipolar Cycloaddition For The Surface Modification Of Colloidal Particles With Electroactive And Emissive Moieties, Parul Rungta

All Dissertations

The development of charge–transporting and fluorescing colloidal particles that can be directly printed into electroluminescent devices may result in a broad impact on the use of electrical energy for illumination. The objective of this work was to design and synthesize electroactive & fluorescing colloidal particles; establish their optical, electronic, and thermodynamic properties; and transition them into a device format for potential applications. The original intended application of this work was to build “better” colloidally–based organic light emitting devices (OLEDs) by creating functional particles with superior electrical and optical performance relative to commercially available technologies, but through the course of the …

Production And Characterization Of Aramid Copolymer Fibers For Use In Cut Protection, Jeffrey Moreland

All Dissertations

High-performance fibers such as para-aramids are used extensively in gloves for cut protection. However, the inherent cut resistance of these fibers and the relationship between cut resistance and other material properties is not known. To better understand cut resistance at the material level, an experiment was conducted using a lab-scale wet spinning system to produce and characterize aramid copolymer fibers.
To facilitate the use of lab-scale equipment, the experiment was conducted as a four-factor split-plot response surface design. The four treatment factors studied were solvent concentration in the coagulation bath, the amount of salt in the coagulation bath, the degree …

Thermal Properties Of Lunar Regolith Simulants, Kenneth W. Street, Chandra Ray, Doug Rickman, Daniel A. Scheiman

Materials Science and Engineering Faculty Research & Creative Works

Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H₂O and/or OH-, the presence of which has substantial impact on important system behaviors. We have undertaken studies of lunar regolith simulants to determine the limits of the simulants to validate key components for human survivability during sustained presence on the moon. Differential Thermal Analysis (DTA) yields information on phase transitions and melting temperatures. Thermo-Gravimetric Analysis (TGA) with Fourier Transform Infrared (FTIR) analysis provides information on …

Plasma Processing Of Lunar Regolith Simulant For Oxygen And Glass Production, S. Sen, D. Butts, J. S. O'Dell, C. S. Ray

Materials Science and Engineering Faculty Research & Creative Works

Tools for extracting life-sustaining resources from the moon are needed to support the vision for space exploration. of particular interest is the production of oxygen for life support and propulsion. on the lunar surface the only practical source for oxygen is the lunar regolith. Described in this paper is an innovative plasma reduction technique for the production of oxygen from lunar regolith. Thermodynamic calculations showed that the regolith oxides could be dissociated to yield up to 7.3 weight percent oxygen when exposed to extremely high temperatures of up to 3000°C. Subsequently the use of a plasma flame to obtain oxygen …

Effect Of Cldh On Rebar Corrosion Behavior In Chloride Contaminated Neutral Pore Solutions, Yu-Ming Tang, Le Niu, Yu Zuo

Journal of Electrochemistry

he effect of calcined LDH-MgAl-CO₃ on rebar corrosion behavior in chloride ion contaminated neutral concrete pore solutions was investigated in this paper.Corrosion potentials of rebars in pore solutions after treatment with CLDH were higher than before treatment.According to polarization tests,passivated region of rebars in pore solutions after treatment with CLDH was found apparently instead of activation.EIS tests showed that CLDH made the impedance of specimens increase.The measurements of pH and chloride ion concentration after treatment indicated that / of pore solutions decreased by 4～5 magnitude orders.

Electrochemical Detection For The Corrosion Of Reinforcing Steel In Concrete During Immersion And Drying Cycles, Bing-Li Jia, Fa-He Cao, An-Na Chen, Jian-Qing Zhang

Journal of Electrochemistry

The corrosion behavior of reinforcing steel in concrete under dry-wet cycle condition has been studied by electrochemical noise(EN) compared with the electrochemical impedance spectroscopy(EIS),SEM micrographs and EDS.The statistical method has been employed to analyze the EN data of reinforcing steel in concrete,which revealed three different corrosion stages of reinforcing steel in concrete,including the dissolution of the passive film,the active corrosion and the cumulation of corrosion product.The wavelet transform has also been employed,which indicated that steel in concrete with pH 1 is associated with uniform corrosion,while steel in concrete with pH 3 and pH 7 are associated with localized corrosion,such as …