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Articles 12211 - 12240 of 16704

Full-Text Articles in Engineering

Precipitate Redistribution During Creep Of Alloy 617, Scott Schlegel, Sharla Hopkins, E. Young, James Cole, Thomas Lillo, Megan Frary Dec 2009

Precipitate Redistribution During Creep Of Alloy 617, Scott Schlegel, Sharla Hopkins, E. Young, James Cole, Thomas Lillo, Megan Frary

Materials Science and Engineering Faculty Publications and Presentations

Nickel-based superalloys are being considered for applications within advanced nuclear power generation systems due to their high temperature strength and corrosion resistance. Alloy 617, a candidate for use in heat exchangers, derives its strength from both solid solution strengthening and the precipitation of carbide particles. However, during creep, carbides that are supposed to retard grain boundary motion are found to dissolve and re-precipitate on boundaries in tension. To quantify the redistribution, we have used electron backscatter diffraction and energy dispersive spectroscopy to analyze the microstructure of 617 after creep testing at 900 and 1000°C. The data were analyzed with respect …


Synthesis And Evaluation Of Bioceramics For Orthopedics And Tissue Culture Applications, Hande Demirkiran Dec 2009

Synthesis And Evaluation Of Bioceramics For Orthopedics And Tissue Culture Applications, Hande Demirkiran

Material Science and Engineering Dissertations - Archive

Hydroxyapatite is the most well known phosphate in the biologically active phosphate ceramic family by virtue of its similarity to natural bone mineral. Among all bioglass compositions Bioglass®45S5 is one of the most bioactive glasses. This study initially started by adding different amounts (1, 2.5, 5, 10, and 25 wt. %) of Bioglass®45S5 to synthetic hydroxyapatite in order to improve the bioactivity of these bioceramics.The chemistries formed by sintering and their effect on different material properties including bioactivity were identified by using various techniques, such as powder and thin film x-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray …


Tribological Performance Of Ashless Antiwear Additives Under Extreme Pressure Conditions, Bohoon Kim Dec 2009

Tribological Performance Of Ashless Antiwear Additives Under Extreme Pressure Conditions, Bohoon Kim

Material Science and Engineering Dissertations - Archive

Zinc diakyl dithiophosphate (ZDDP) has been used in engine oil for several decades as an antiwear additive. However, ZDDP is the primary source of P, S and Zn in the exhaust, which results in frequent maintenance or replacement of exhaust gas treatment systems. The use of ashless additives is more desirable because of recent environmental regulations. The main goal of this research was to develop a fundamental understanding of how ashless compounds protect the tribological surface in comparison to ZDDP. X-ray absorption near edge structure spectroscopy (XANES) has been performed on tribo and thermal films in order to investigate the …


Self Powered Sensing By Combining Novel Sensor Architectures With Energy Harvesting, Vishwas Bedekar Dec 2009

Self Powered Sensing By Combining Novel Sensor Architectures With Energy Harvesting, Vishwas Bedekar

Material Science and Engineering Dissertations - Archive

Recent advancements in the field of wireless sensor networks have resulted in increasing demand for self-powering techniques that reduces the dependence on batteries. In order to address this problem, there has been significant effort on generating small electrical power locally by harvesting energy from freely available environmental sources such as mechanical vibrations, wind, and stray magnetic field. Further, there is need for inventing new sensing techniques to reduce the overall power consumption. The road for reaching the destination of self-powered sensor networks requires cooperative progress in reduction in sensor power consumption by developing new sensing mechanisms and local generation of …


Pozzolanic Activity Of Rice Husk Ash: Comparison Of Various Electrical Methods, S Wansom, S Janjaturaphan, S Sinthupinyo Dec 2009

Pozzolanic Activity Of Rice Husk Ash: Comparison Of Various Electrical Methods, S Wansom, S Janjaturaphan, S Sinthupinyo

Journal of Metals, Materials and Minerals

The great abundance of rice husk ash (RHA) as low-cost agricultural waste in Thailand makes it the most suitable material for cement-based applications. However, the use of RHA as a supplementary cementitious material (SCM) is not yet widespread in Thailand due to the poor pozzolanic activity of most agricultural RHA. Most RHA is incinerated at too high temperatures (usually in excess of 1000ºC) or under uncontrolled conditions as biomass fuel. This reduces the amount of amorphous SiO2 and hence worsens the pozzolanic activity of the resulting RHA. To enhance the use of RHA as an SCM in Thailand, a proper …


A Simple Method For Production Of Humidity Indicating Silica Gel From Rice Husk Ash, J Nayak, J Bera Dec 2009

A Simple Method For Production Of Humidity Indicating Silica Gel From Rice Husk Ash, J Nayak, J Bera

Journal of Metals, Materials and Minerals

The objective of the present work is to develop a procedure for obtaining and characterizing active blue silica from rice husk ash. About 25 wt.% silica powder (from total mass of rice husk) of 95% pure silica could be produced after heat-treating at 700°C for 6 hours. A simple method based on alkaline extraction followed by acid precipitation was developed to produce pure silica hydrogel from RHA. A well-defined very minimum amount CoCl2-containing blue silica gel was prepared by impregnation of the aqueous solution of the salt to silica hydrogel, ageing and drying method. The sharp colour changing from blue …


A Global Defect Chemistry Model For P-Type Mixed Ionic And Electronic Conductors, Xiao Dong Zhou, Harlan U. Anderson Dec 2009

A Global Defect Chemistry Model For P-Type Mixed Ionic And Electronic Conductors, Xiao Dong Zhou, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

A global defect chemistry model is presented to relate the properties of a variety of p-type perovskite conductors, including chromites, manganites, and ferrites, which can be tailored as mixed ionic and electronic conductors (MIECs). It is found that oxygen nonstoichiometry in these p-type MIECs can be correlated using reaction constant for oxygen vacancy generation. the values of reaction constant for oxygen vacancy formation can be obtained by simulating the electronic conductivity as a function of oxygen activity and temperature with the existing global model that is based on the concept of localized electron holes. the global defect chemistry model allows …


Synthesis, Characterization And Potential Applications Of Fept Nanoparticles, Vikas Nandwana Dec 2009

Synthesis, Characterization And Potential Applications Of Fept Nanoparticles, Vikas Nandwana

Material Science and Engineering Dissertations - Archive

Monodisperse FePt nanoparticles with controlled size and geometry have drawn great attention in the last decade for fundamental scientific studies and for their potential applications in advanced materials and devices such as ultra-high-density magnetic recording media, exchange-coupled nanocomposite magnets, biomedicines and nanodevices. This dissertation focuses on the synthesis and characterization of FePt nanoparticles and their use in potential applications. The FePt nanoparticles of different size (2 to 16 nm) and shape (spherical, cubic, rod) were synthesized by a chemical solution method. The size and shape of these particles were controlled by adjusting reaction parameters. The as-synthesized FePt nanoparticles have chemically …


Ziegler-Natta Catalyst With High Activity And Good Hydrogen Response, L Sinthusai, W Trakarnpruk, R Strauss Dec 2009

Ziegler-Natta Catalyst With High Activity And Good Hydrogen Response, L Sinthusai, W Trakarnpruk, R Strauss

Journal of Metals, Materials and Minerals

Ziegler-Natta catalysts were prepared from chemical reaction route comprising of steps of 1) magnesium complex formation between butyloctyl magnesium and 2-ethyl-1-hexanol, 2) MgCl2 support preparation from the reaction between the magnesium complex and TiCl4 as chlorinating agent and 3) titanation with TiCl4. The catalysts were used for ethylene polymerization using triethylaluminum as a cocatalyst. Effects influencing properties of catalysts and polymerization performance were investigated: triethylaluminum/Mg molar ratio, Ti/Mg molar ratio, addition of electron donor and aging step. Results show that addition of ethylbenzoate as an electron donor resulted in decreased catalytic activity. However it was found that catalytic stability under …


Preparation Of Silica Gel From Rice Husk Ash Using Microwave Heating, S Rungrodnimitchai, W Phokhanusai, N Sungkhaho Dec 2009

Preparation Of Silica Gel From Rice Husk Ash Using Microwave Heating, S Rungrodnimitchai, W Phokhanusai, N Sungkhaho

Journal of Metals, Materials and Minerals

The purpose of this research is to separate silica gel from rice husk ash by microwave heating. The experiments were performed by heating rice husk ash in sodium hydroxide solution with various concentrations in microwave oven for 5 or 10 minutes. The obtained sodium silicate was neutralized to give silica gel. The best condition for silica gel production was the reaction with 2.0 M sodium hydroxide at microwave power of 800 W for 10 minutes. The ability of silica gel as desiccant was investigated by adsorption test. The results showed that silica gel prepared by low concentration of sodium hydroxide …


Synthesis And Characterization Of Silicon-Silicon Carbide Composites From Rice Husk Ash Via Self-Propagating High Temperature Synthesis, S Niyomwas Dec 2009

Synthesis And Characterization Of Silicon-Silicon Carbide Composites From Rice Husk Ash Via Self-Propagating High Temperature Synthesis, S Niyomwas

Journal of Metals, Materials and Minerals

Silicon-Silicon Carbide (Si-SiC) composites were synthesized by self-propagating high temperature synthesis (SHS) from a powder mixture of rice husk ash (RHA)-C-Mg. The reaction was carried out in a SHS reactor under static argon gas at a pressure of 0.5 MPa. The standard Gibbs energy minimization method was used to calculate the equilibrium composition of the reacting species. The comparison of silica from RHA and commercial sources in the precursor mixture on the Si-SiC conversion has investigated using X-ray diffraction and scanning electron microscope technique. The as-synthesized products of Si-SiC-MgO powders were leached with 0.1M HCl acid solution to obtain the …


Synthesis And Characterization Of Sio2 Nanowires Prepared From Rice Husk Ash, S Pukird, P Chamninok, S Samran, P Kasian, K Noipa, L Chow Dec 2009

Synthesis And Characterization Of Sio2 Nanowires Prepared From Rice Husk Ash, S Pukird, P Chamninok, S Samran, P Kasian, K Noipa, L Chow

Journal of Metals, Materials and Minerals

SiO2 nanowires were synthesized by thermal evaporation of rice husk ash and coconut shell charcoal with the ratio of 1:2 by weight heated at a temperature of 1,350ο C in atmosphere of nitrogen for 1 hour. The scanning electron microscope and X-rays diffraction instrument are used to characterize the SiO2 nanowires. The SiO2 nanowires synthesized have diameters varying from 40 nm to 200 nm while the lengths were a few micrometers.


Preparation And Characterization Of Silicon From Rice Hulls, E Swatsitang, M Krochai Dec 2009

Preparation And Characterization Of Silicon From Rice Hulls, E Swatsitang, M Krochai

Journal of Metals, Materials and Minerals

High purity silica can be prepared by reflux raw rice hulls in 1 N HCl for 45 minutes first, then pyrolyzed at 650°C for 3 hours in O2 atmosphere. The obtained white ash was examined by XRD showing a broad peak of amorphous silica at 2 theta = 22 degree. Silicon can be prepared by metallothermal reduction of pure silica at 650°C in Ar atmosphere for 1-3 hours, using magnesium (99% purity) as a reducing agent. High purity silicon (99.98 %) can be obtained by subsequently washing the as-reduced silica with HCl: H2O and HF: H2O solutions. The results from …


Utilization Of Rice Husk To Synthesize High-Performance Phosphors, L Xiong, K Saito, S Wada, E H. Sekiya Dec 2009

Utilization Of Rice Husk To Synthesize High-Performance Phosphors, L Xiong, K Saito, S Wada, E H. Sekiya

Journal of Metals, Materials and Minerals

Rice husk (RH) has high C and Si contents, so it can be used not only as a fuel candidate, but also as a low-cost Si source for synthesizing high-performance products. In the present work, we proposed a low-cost route to synthesize high-performance silicate phosphors with RH. RH was burned either as received or as pretreated by HCl washing. The resulting ashes were, respectively, utilized to react with other raw materials at high temperatures to form silicate phosphors. The high-temperature solid-state reaction process was optimized by varying either the temperature or the holding time. The crystallographic and fluorescent properties of …


Utilization Of Silica In Rice Hulls As Raw Materials For Silicon Semiconductors, T Okutani Dec 2009

Utilization Of Silica In Rice Hulls As Raw Materials For Silicon Semiconductors, T Okutani

Journal of Metals, Materials and Minerals

Highly pure silicon and silicon compounds are required in high technology products such as semiconductors and solar cells. Rice hulls consist of 71 to 87wt% organic components such as cellulose and 13 to 29wt% inorganic components. In rice hulls, 87 to 97wt% of the inorganic components are silica (SiO2). Rice plants absorb water-soluble siliceous ions via the roots. These ions are transported to stems, leaves and rice hulls by sap flow. In rice hulls, siliceous ions accumulate at the cuticle outside of the epidermis. The production of pure silicon compound (SiCl4) and of silicon metal as the starting material for …


Utilization Of Rice Husk Ash Silica In Controlled Releasing Application, P Prawingwong, C Chaiya, P Reubroycharoen, C Samart Dec 2009

Utilization Of Rice Husk Ash Silica In Controlled Releasing Application, P Prawingwong, C Chaiya, P Reubroycharoen, C Samart

Journal of Metals, Materials and Minerals

Mesoporous silica was produced by sol-gel technique using rice husk ash as a silica source which was applied in the drug delivery system. The drug releasing behavior was studied in phosphate buffer using indigo carmine as a drug model. The textural properties of mesoporous silica were characterized and considered with the result of the releasing study. The pore volume and silanol group on the surface of mesoporous silica affected the releasing behavior. The larger pore volume could contain the larger amount of drug which showed fast release. The effect of the silanol group presented an interaction between the drug molecule …


Crystal Habit Of Caco3 Under Different Carbonation Methods, J Ariyaprayoon, U Leela-Adisorn, A Supsakulchai Dec 2009

Crystal Habit Of Caco3 Under Different Carbonation Methods, J Ariyaprayoon, U Leela-Adisorn, A Supsakulchai

Journal of Metals, Materials and Minerals

The saturated solutions of Ca(OH)2 were carbonated by CO2 in air under static and turbulent conditions. The saturation state of starting solution and carbonation methods had effect on the crystal habit. The phase of CaCO3 precipitated from saturated solution is calcite. No metastable phase of CaCO3 was found.


Effect Of Black Rice Husk Ash Substituted Opc On Strength And Leaching Of Solidified Plating Sludge, R Piyaphanuwat, S Asavapisit Dec 2009

Effect Of Black Rice Husk Ash Substituted Opc On Strength And Leaching Of Solidified Plating Sludge, R Piyaphanuwat, S Asavapisit

Journal of Metals, Materials and Minerals

Strength and leachability of the solidified plating sludge using OPC and BHA as solidification binders were investigated. BHA was used to replace OPC at 0, 20 and 30 wt.%, and was used to solidify 30 and 50 wt.% of the plating sludge. Results showed that no strength was observed during the first 7 days of curing when OPC was used to solidify the plating sludge. But when 20 and 30 wt.% of BHA were used to substitute OPC, the solidified wastes containing 50 wt.% of the plating sludge gave strength of 4.5 kg/cm2 at the age of 3 and 4.1 …


Synthesis Of Zeolite A Membrane From Rice Husk Ash, C Bhavornthanayod, P Rungrojchaipon Dec 2009

Synthesis Of Zeolite A Membrane From Rice Husk Ash, C Bhavornthanayod, P Rungrojchaipon

Journal of Metals, Materials and Minerals

Rice husk is a major by-product of the rice-processing industries. The burning of rice husk in air results in the formation of rice husk ash (RHA) with a content in SiO2 that varies from 85 to 98% depending on the burning conditions, the furnace type and the rice variety. Numerous studies aimed at using RHA as a cheap alternative source of amorphous silica for the production of silicon based materials with industrial and technological interests. The zeolite gel was prepared with the following batch composition: 3.1Na2O : Al2O3: 1.9SiO2: 128H2O synthesized by hydrothermal treatment with various times from 15 min …


Burning Temperature Dependence Of Rice Husk Ashes In Structure And Property, L Xiong, E H. Sekiya, P Sujaridworakun, S Wada, K Saito Dec 2009

Burning Temperature Dependence Of Rice Husk Ashes In Structure And Property, L Xiong, E H. Sekiya, P Sujaridworakun, S Wada, K Saito

Journal of Metals, Materials and Minerals

Much attention has been paid to the characterization of the structure and properties of rice husk ash (RHA), but little to the burning temperature dependence of its structure and properties. This dependence is important for the structure and property optimization of RHA in a controllable manner. In this paper, we present a research on the burning temperature dependence of RHA. Rice husk (RH) was burned at various temperatures either as received or after pretreatment by HCl washing. The obtained ashes of both groups exhibit a strong burning temperature dependence of the specific surface area and pore volume, based on the …


Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme Dec 2009

Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme

Stephen Ducharme Publications

Among the ferroelectric thin films used in field-effect transistor devices; the ferroelectric copolymer of polyvinylidene fluoride PVDF –CH2–CF2–, with trifluoroethylene TrFE –CHF–CF2–, has distinct advantages, including low dielectric constant, low processing temperature, low cost, and compatibility with organic semiconductors. The operation of a metal-ferroelectric insulatorsemiconductor structure with PVDF-TrFE as the ferroelectric layer was analyzed and optimized by numerical solution of the Miller and McWhorter model. A model device consisting of 20 nm PVDF/TrFE on a 10-nm-thick high-k dielectric buffer exhibits a memory window of 5 V with an operating voltage of 15 V. The operating voltage can be reduced to …


Simpler Packaging, Tomiko Oden Dec 2009

Simpler Packaging, Tomiko Oden

Graphic Communication

This project explains how product packaging is become more "green", and thus more simple. Packaging needs to go beyond just simplifying materials and graphics - it needs to create a simpler process in order to reduce wasted time, energy, and resources.


Investigation Of The Thermoelectric Behavior And Structure Formation Of (Pbte/Agsbte2)-Silver Chalcogenide Mixtures, Yisha Wang Dec 2009

Investigation Of The Thermoelectric Behavior And Structure Formation Of (Pbte/Agsbte2)-Silver Chalcogenide Mixtures, Yisha Wang

All Theses

Sustainable energy research is currently on the forefront of scientific exploration and energy conservation and the development of new energy production techniques are both crucial for our long lasting stable future. Accordingly, thermoelectric materials will be a significant energy conservation and production source. The state-of -the-art thermoelectric materials can be used to collect the wasted heat and converted to power, which is the future for the green power generation.
PbTe is considered a state-of-the-art thermoelectric material, which has been extensively studied. It forms in the NaCl structure and it is a semiconductor with a room temperature gap value of 0.29 …


Mechanical And Chemical Characterization Of Biological Composite Structures, Bonnie Zimmerman Dec 2009

Mechanical And Chemical Characterization Of Biological Composite Structures, Bonnie Zimmerman

All Theses

A better understanding of the bioresponse of naturally occurring systems will help
to optimize the engineering of synthetic biomaterials. The aim of this thesis was to
characterize the mechanical and chemical behavior of two distinct biological composite
systems, human teeth and wool fibers. These mechanical and chemical properties were
also studied as a function of natural structure and environmental conditions.
Human teeth are composite systems consisting primarily of hydroxylapatite and
protein. This project investigated how the use of clinical dental treatments and
procedures, such as whitening and etching, affects mechanical properties. Analysis of
nanoindentation with the Oliver-Pharr model provided elastic …


Nucleation And Growth Behavior Of Tellurite-Based Glasses Suitable For Mid-Infrared Applications, Jonathan Massera Dec 2009

Nucleation And Growth Behavior Of Tellurite-Based Glasses Suitable For Mid-Infrared Applications, Jonathan Massera

All Dissertations

Optical fibers transmitting in the 2-5 μm mid-infrared (MIR) spectral region are highly desirable for a variety of military and civilian applications including super-continuum generation, infrared countermeasures (IRCM), and MIR laser sources. These new applications in the mid-infrared require novel optical materials that transmit in this window and can be fabricated into fiber. As tellurite glasses are known to have good transparency in the (NIR) region, tellurite-based glasses are the material of choice for this study due to their high linear and nonlinear refractive index, their low glass transition temperature and the ability to form them into optical fiber.
This …


Design And Performance Of Load Bearing Shear Walls Made From Composite Rice Straw Blocks, Kevin Robert Camann Dec 2009

Design And Performance Of Load Bearing Shear Walls Made From Composite Rice Straw Blocks, Kevin Robert Camann

Master's Theses

Although rice straw and other grains have been used in building since pre-history, in the past two decades, there has been a move to utilize this rapidly renewable, locally available, agricultural byproduct as part of the sustainable construction movement. Up to this point, this has been done by simply stacking up the full straw bales. Stak Block, invented by Oryzatech, Inc., is a modular, interlocking block made of a composite of rice straw and binding agent that serves as an evolution in straw construction. This study investigates the feasibility of using these Stak Blocks as a structural system. The report …


Exergetic And Thermoeconomic Analyses Of The Rice-Husk Power Plant In Thailand, P Peerapong, B Limmeechokchai Dec 2009

Exergetic And Thermoeconomic Analyses Of The Rice-Husk Power Plant In Thailand, P Peerapong, B Limmeechokchai

Journal of Metals, Materials and Minerals

The purpose of this study is to analyze a rice husk power plant, and consider the efficiency of the power plant through both the first law and the second law of thermodynamics. The energetic and exergetic performance criteria such as thermal efficiency, exergy efficiency, and exergy loss have been found to be useful methods in design, evaluation, optimization and improvement of thermal power plants. The exergetic efficiency of a power plant shows that the boiler is the major component contributing to total loss, with its exergetic efficiency of 30%, while the steam turbine has the exergetic efficiency of 76%. The …


Influence Of Impurity Ions On Rice Husk Combustion, L Xiong, K Saito, E H. Sekiya, P Sujaridworakun, S Wada Dec 2009

Influence Of Impurity Ions On Rice Husk Combustion, L Xiong, K Saito, E H. Sekiya, P Sujaridworakun, S Wada

Journal of Metals, Materials and Minerals

Rice husk (RH) contains various impurity ions such as K+ , Al3+, Fe3+, Mnn+ (n = 2 - 4), and P-containing acid ions. In the present work, some of their oxides, formed in RH combustion, were found to exert a strong influence on the middle- and late stages of RH combustion, and consequently, strongly affected the structure and properties of the final ash. Very recently, we proved for the first time that the existence of the transition metallic ions in rice husk can lead to a decrease of about 70°C in the terminal combustion temperature (Ttc) of RH. This catalytic …


Production And Characterization Of Novel Shaped Fibers For Fluid Sorption And Transport, Lisa Fuller Dec 2009

Production And Characterization Of Novel Shaped Fibers For Fluid Sorption And Transport, Lisa Fuller

All Dissertations

This work investigated the production and characterization of novel shaped fibers for fluid adsorption and transport. Shaped fibers such as Y, H, and octolobal, as well as conventional round fibers, were extruded using a research melt extruder. The fibers were extruded from 18 melt flow index (MFI) polypropylene (PP) and blends of 18 MFI PP and 400 MFI PP. Hydrophilic spin finish Bozzetto Favorol SF2 was applied to the surface of extruded fibers and hydrophilic polyester additive LB-100 was included in the blend of some H fibers to increase the hydrophilicity of the fiber surface. The geometric shape retention of …


Indirect Electrosynthesis Of Double Aldehyde Starch Using Pb-(Bro3-/Br-) As Electro-Catalytic Mediator, Ni-Na Chen, Ri-Yao Chen, Xi Zheng, Xiao Chen, Zhen Chen Nov 2009

Indirect Electrosynthesis Of Double Aldehyde Starch Using Pb-(Bro3-/Br-) As Electro-Catalytic Mediator, Ni-Na Chen, Ri-Yao Chen, Xi Zheng, Xiao Chen, Zhen Chen

Journal of Electrochemistry

In this paper,Nafion membrane was used as the separator in the electrolysis cell to indirectly electro-generating the double aldehyde starch(DAS) with BrO3-/Br-as a redox mediator and Pb as an anode.Effects of temperature,concentration of sulfuric acid and starch on the electro-oxidation of DAS were discussed.The steady state polarization curves were obtained.The experiment results showed that the current efficiency was over 50% when the electrolysis current density was 15mA/ cm2.