Materials Science and Engineering Commons^™

Purification Of Solar Grade Silicon Using Electromagnetic Field, Anping Dong, Lucas N.W. Damoah, Lifeng Zhang, Hui Zhu

Materials Science and Engineering Faculty Research & Creative Works

Non-metallic particles and the metallic impurity elements in the solar cell silicon have a strong detrimental effect on the conversion efficiency of the solar cell. Removing these impurities is one of the important tasks for silicon refining. the current paper proposed a new approach to purify silicon - electromagnetic (EM) separation. Since the non-metallic particles and the metallic impurity elements are non- or less conductive while the molten silicon is well conductive, under EM field, the Lorenz force will push the particles to the boundary layer, thus separate these inclusions. in the current study, a high frequency EM field was …

Non-Metallic Particles In Solar Grade Silicon (Sog-Si), Lucas Nana Wiredu Damoah, Anping Dong, Lifeng Zhang, Hui Zhu

Materials Science and Engineering Faculty Research & Creative Works

This study investigated the non-metallic inclusions in Solar 2rade Silicon (SoG-Si), especially the distribution of inclusions in the top 15mm layer of multicrystalline silicon ingot. the SoG-Si ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. the hard inclusions lead to wire breakages during the cutting of the ingot into wafers. the main kinds of inclusions found in top-cut silicon scraps from two manufacturers have been investigated using acid extraction, automated feature analysis techniques and SEM-EDS and optical Microscope: They are needle-like Si3N4 and lumpy …

Investigating Wood Welding Parameters Using A Prototype Welding Machine, Timothy R. Melin

Master's Theses

Understanding how different processing variables influence wood welded bonds is vital if the technique will ever be used to create engineered lumber without using adhesives. A variation of vibration welding, wood welding uses pressure and friction to bond materials together. During welding, heat causes a softening in the wood, a naturally occurring composite material. This softening leads to fiber entanglement and a bond forms upon cooling.

The goal of this research was to investigate several processing aspects of the wood welding procedure. A prototype wood welding machine, designed and fabricated from the ground up, was used to investigate the effects …

Versatile Route For Preparation Of Polydiacetylene/Zno Nanocomposites And Their Colorimetric Response To Ph And Ethanol, N Rungruangviriya, N Traiphol

Journal of Metals, Materials and Minerals

This contribution presents a simple method to prepare polydiacetylene(PDA)/ZnO nanocomposites, which can be utilized as active materials in sensing technology. The ZnO nanoparticles, which constitute of Zn-OH2 + , Zn-OH and Zn-O- groups at their surfaces, function as nano-substrates for self-assembling of diacetylene monomers, 10,12-pentacosadiynoic acid (PCDA), in aqueous medium. Photopolymerization of the assemblies yields poly(PCDA)/ZnO nanocomposites with core-shell structure. Strong interactions between the active groups at ZnO surface and carboxylic head groups of poly(PCDA) promote chain ordering and reduce segmental dynamics of poly(PCDA) in the nanocomposites. The existence of strong interfacial interaction drastically affects the colorimetric response behavior of …

Preparation And Properties Of Superhydrophobic Cotton Fabrics, P Kampeerapappun, K Visatchok, D Wangarsa

Journal of Metals, Materials and Minerals

In this study, superhydrophobic cotton fabric was prepared by coating maleic-anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA) triblock copolymer solutions containing calcium carbonate (CaCO3) particles. SEBS-g-MA solutions were prepared using single solvent (toluene and tetrahydrofuran (THF)) and mixed solvent (toluene: ethanol (EtOH) and THF: EtOH). Cotton fabrics were treated with the prepared solution using padding technique. All coated fabrics exhibited a water contact angle (WCA) of more than 100°. Optimum WCA values were observed when THF and 90:10 toluene: EtOH were employed. In case of CaCO3 particles addition, 6% W/V CaCO3 could impart the highest WCA value of 154°. However, the durability of …

Corrosion Assessment Of Carbon Steel In Thailand By Atmospheric Corrosion Monitoring (Acm) Sensors, W Pongsaksawad, E Viyanit, S Sorachot, T Shinohara

Journal of Metals, Materials and Minerals

Atmospheric corrosion of metal depends on material compositions, weather condition (dry, dew, and rain period), temperature, relative humidity, and airborne sea salt of specific location. General testing procedure to obtain the corrosion rate is by actual exposure test of the specimen panels based on time interval plan. In Japan, atmospheric corrosion monitoring (ACM) sensor, made of an iron-silver galvanic couple, has been developed and used to sense the corrosivity in terms of galvanic current. Under some atmospheric conditions, these data can be converted to time of wetness and related to the corrosion rate of carbon steel. With ACM sensors, it …

Preparation And Characteristics Of Galangal Essential Oil/Alginate Microcapsules, T Jiamrungraksa, S Charuchinda

Journal of Metals, Materials and Minerals

Galangal essential oil/alginate microcapsules were prepared by solidifying in liquid (orifice method) between sodium alginate and calcium chloride. The structure, morphology and also the thermal stability of the microcapsules were investigated by FT-IR, optical microscope, infrared moisture determination balance (IMDB) at 120°C for 2 hours. The galangal essential oil release content of microcapsules was estimated by measuring time course of weight of microcapsules determination by isothermal TGA at 37°C and 120°C. FT-IR spectral data confirmed the presence of galangal essential oil in the prepared microcapsules. An increase of sodium alginate concentration and oil content resulted in significantly higher average size …

Development Of An Aluminum Semi-Solid Extrusion Process, T Rattanochaikul, S Janudom, N Memongkol, J Wannasin

Journal of Metals, Materials and Minerals

Semi-solid extrusion process is a new forming process that is quite promising because the process requires lower forming pressure than conventional solid extrusion. In addition, semi-solid extrusion does not require large machines, which results in lower production costs. The aim of this article is to study the feasibility of an aluminum semi-solid extrusion process. The semi-solid technique selected for usage in this study was the Gas Induced Semi-Solid (GISS) process. The laboratory extrusion system was developed in this work. In the experiments, nitrogen gas was injected into aluminum melt for about 5 seconds. After that, the obtained semi-solid slurry was …

Hardness And Fracture Toughness Of Alumina-Based Particulate Composites With Zirconia And Strontia Additives, T Oungkulsolmongkol, P Salee-Art, W Buggakupta

Journal of Metals, Materials and Minerals

This project aims to study characteristics and mechanical properties i.e. hardness and fracture toughness of alumina matrix composite materials containing zirconia and strontium oxide. Two groups of composite specimen were fabricated: (i) Al2O3 matrix with 3 mol% Y2O3- ZrO2, varied from 10, 20, 30 and 40 vol%, and (ii) Al2O3 matrix with 2, 5, 10 and 15 vol% SrO added in the form of SrCO3. The powders were blended and then pressed into pellets. The compacts were pressureless sintered at 1600 o C for 2 hours in air. Density measurement of the sintered composites was carried out using liquid immersion. …

Development Of Layered Zn-Fe Coatings For Better Corrosion Protection, R S. Bhat, R Udupak, A C. Hegde

Journal of Metals, Materials and Minerals

In this research, the Zn-Fe coating having successive layers of alloys of two different compositions were developed alternatively on mild steel for better corrosion protection. The multilayer coatings, or alternatively, composition modulated alloy (CMA) coatings of different configurations have been developed, and their corrosion behaviors were evaluated by electrochemical DC and AC methods. The cyclic cathode current densities and numbers of layers have been optimised for peak corrosion stability of the coatings. Under optimal condition, the CMA coating having 300 layers, having about 67 nm average thickness was found to be approximately six times higher corrosion resistant than monolayer coating …

Microstructural Evolution Of Surface Layers During Electrolytic Plasma Processing, Cristian Cionea

Material Science and Engineering Dissertations - Archive

Electrolytic Plasma Processing is an emerging technology for surface modification. The EPP process is based on electrolysis of an aqueous electrolyte by application of an electrical potential between the workpiece and counter-electrode, and the production of plasma (micro-arc discharges on the workpiece surface). The plasma micro-arcs provide a heat source for surface modification via localized surface melting and rapid cooling (cleaning process) and, if desirable, enhance ion deposition on a given substrate (coating). Three substrates (low carbon steel, pure Al and pure Ti) were "cleaned" by EPP and their near surface layer microstructure was studied. It was found that the …

Bubble Template Synthesis Of Hollow Gold Nanoparticles And Their Applications As Theranostic Agents, Chienwen Huang

Material Science and Engineering Dissertations - Archive

Hollow gold nanoparticle with a sub-30nm polycrystalline shell and a 50 nm hollow core has been successfully synthesized through the reduction of sodium gold sulfite by electrochemically evolved hydrogen. Such hollow gold nanoparticles exhibit unique plasmonic properties. They strongly scatter and absorb near infrared light. In this thesis we seek to understand the formation mechanism of hollow gold nanoparticles in this new synthesis process and their plasmonic properties. Also, we explore their biomedical applications as theranostic agents (therapeutic and diagnostic imaging). A lithographically patterned electrode consisting of Ag stripes on a glass substrate was used to investigate the formation process …

Study On The Leakage Current Behavior And Conduction Mechanism Of Porous Low-K In Cu/Porous Low-K Interconnects: The Influence Of Extrinsic Factors, Liangshan Chen

Material Science and Engineering Dissertations - Archive

This study investigates the influence of extrinsic factors including moisture and impurities trapped in porous low-k (PLK) and defective diffusion barrier on the leakage current behavior and the associated conduction mechanism of PLK in advanced Cu/PLK interconnects. For this purpose, a voltammetry technique that was previously developed for diffusion barrier characterization was extended to detect the trapped impurities in PLK. With this technique in hand, the influence of extrinsic factors was then studied. Cu was found to diffuse out into PLK through barrier defects in the presence of electric stress. Its out-diffusion and subsequent migration in PLK manifested as a …

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 …