Ceramic Materials Commons^™

An Evaluation Of The Performance Characteristics Of Olivine Temper In Pueblo Ii Virgin River Puebloan Ceramics, Sharlyn Anderson

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this study is to examine the technological properties of the three dominant temper types - olivine, sand, and sherd - used by the Virgin Branch Puebloan during the Pueblo II era (AD 1000-1500) to explain the high proportion of Moapa Gray Ware traded to the Moapa Valley at that time. The research is guided by the hypothesis that olivine tempered pottery - or Moapa Gray Ware - possessed superior technological qualities than locally made wares, and that these qualities fueled the demand of Moapa Gray Ware ceramics.

This thesis evaluates one possibility for explaining the transportation of …

Batio3–Srtio3 Layered Dielectrics For Energy Storage, Sheng Chao, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

BaTiO₃–SrTiO₃ (BST) thick films (~ 250–390 μm) with layered structures were fabricated by tape-casting and lamination process. Layered composites with various Ba/Sr ratios were obtained by lamination of BaTiO₃ (BT) and SrTiO₃ (ST) tapes in different spatial configurations (2–2). As-prepared BST ceramics showed much improved sinterability over the laminates of pure BT or pure ST tapes. Dielectric properties of materials were measured in the temperature range of 25 °C to 200 °C. The method of utilizing of layered structures offered flexibility to maximize the energy storage capability at specific operating conditions: (temperature and electric field) …

Hollow Hydroxyapatite Microspheres For Controlled Delivery Of Proteins, H. Fu, M. N. Rahaman, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of a lithium-calcium-borate glass (106-150 microns) for 2 days in K₂HPO₄ solution (0.02 M; 37°C) and evaluated as a controlled delivery device for a model protein, bovine serum albumin (BSA). the as-prepared HA microspheres had a hollow core with a diameter equal to 0.6 the external diameter, a surface area of V100 m²/g, and a mesoporous shell wall (pore size of ≈13 nm). after loading the hollow HA microspheres with a solution of BSA, release of the BSA into a medium of phosphate-buffered saline (PBS) …

Processing And Characterization Of Boron Carbide-Hafnium Diboride Ceramics, Harlan J. Brown-Shaklee

Doctoral Dissertations

"Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB₂ sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB₂ powder in part by removing oxides at the HfB₂ surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB₂ by 150⁰C compared to carbon, which reduced the hot pressing temperature by ~50⁰C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, …

Method For Determining The Dielectric Constant Of Particles, Vladimir Petrovsky, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

A method of measuring the dielectric constant of a powder, including selecting a powder having an unknown first dielectric constant, selecting a liquid having a known second dielectric constant, and introducing a predetermined amount of powder into a predetermined volume of liquid to define a slurry characterized by a known volume fraction of powder. Next, the impedance spectra of the slurry are plotted over a predetermined frequency range, the measured dielectric constant data is read and the appropriate equivalent circuit for the slurry is determined. Appropriate equivalent circuit equations are applied to the measured dielectric constant data, and the first …

Complex Impedance Study Of Fine And Coarse Grain Tio2 Ceramics, Sheng Chao, Vladimir Petrovsky, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Titanium dioxide (TiO₂) ceramics with various grain sizes were investigated by impedance spectroscopy techniques. Dielectric loss peak identified in coarse grain TiO₂ was attributed to space charge polarization occurring at the grain boundaries. Electric modulus representation of the impedance data showed two types of relaxation processes in coarse grain TiO₂, whereas only one type was observed in fine grain TiO₂. Long-range migration of oxygen vacancies was found to be the dominant conduction mechanism for fine grain TiO₂, while electron hopping between localized states was attributed to dielectric relaxation in coarse grain …

Ebc Development For Hot-Pressed Y2O3/Al2O3 Doped Silicon Nitride Ceramics, Sivakumar Ramasamy, Surendra N. Tewari, Kang N. Lee, Ramakrishna T. Bhatt, Dennis S. Fox

Chemical & Biomedical Engineering Faculty Publications

Multilayer EBCs of alcohol and sol-based slurries containing (a) 45% SiO₂-34% Y₂O₃-%Al₂O₃, (b) mullite/Gd₂SiO₅ (88/12wt.%) with and without B₂O₃ addition, (c) mullite/rare-earth silicates (94/6wt.%, (Gd₂SiO₅, Lu₂SiO₅, Er₂SiO₅, and HfSiO₄)), and (d) only mullite, were applied on hot pressed Y₂O₃/Al₂O₃ doped Si₃N₄ substrates. Of the four major EBC systems studied, only mullite/Gd₂SiO₅ (88/12wt.%) EBCs sintered in air at …

Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

There is an increasing demand for synthetic scaffolds with the requisite biocompatibility, internal architecture, and mechanical properties for the bone repair and regeneration. In this work, scaffolds of a silicate bioactive glass (13-93) were prepared by a freeze extrusion fabrication (FEF) method and evaluated in vitro for potential applications in bone repair and regeneration. The process parameters for FEF production of scaffolds with the requisite microstructural characteristics, as well as the mechanical and cell culture response of the scaffolds were evaluated. After binder burnout and sintering (60 min at 700°C), the scaffolds consisted of a dense glass network with interpenetrating …

Selective Laser Sintering Of 13-93 Bioactive Glass, Krishna C. R. Kolan, Ming-Chuan Leu, Greg Hilmas, Mariano Garcia Velez

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Bioactive glasses are more promising than biopolymers in fabricating scaffolds for bone tissue repair because they convert to hydroxyapatite, when implanted in vivo. Both direct and indirect selective laser sintering (SLS) methods of 13-93 bioactive glass were considered in this research to study the feasibility of fabricating scaffolds for bone repair applications. Stearic acid was used as the binder in the indirect method to fabricate the scaffolds. The green scaffolds underwent binder burnout and sintering at various soaking conditions between 675⁰C and 700⁰C, achieving a maximum compressive strength of 23.6 MPa, which is higher than that of the human cancellous …

Characterization Of Aluminum-Boron Carbide Particulate Metal Matrix Composites, Eric Blank

Materials Engineering

The analysis of die-cast 380 aluminum-boron carbide particulate metal matrix composites (MMC) was performed in order to see if the samples had the required tensile strength of 300 MPa. 10wt% B4C die-cast samples were produced and tested. Half were heat treated to the T6 condition and the others were left as cast. Using ASTM standard B 557M it was found that the average tensile strength for the as-cast samples was 130 MPa and the heat treated samples had a tensile strength of 93 MPa. These values were both lower than expected. The heat treated samples were not expected to have …

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

Materials Science and Engineering Faculty Research & Creative Works

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

Reaction Sintered Zirconium Carbide/Tungsten Composite Bodies And A Method For Producing The Same, Shi C. Zhang, Greg Hilmas, William Fahrenholtz

Materials Science and Engineering Faculty Research & Creative Works

A method of sintering a composite body characterized by a transition metal carbide phase (such as a ZrC phase) substantially evenly distributed in a second, typically refractory, transition metal (such as W) matrix at ambient pressures, including blending a first predetermined amount of first transition metal oxide powder (such as ZrO₂) with a second predetermined amount of second transition metal carbide powder (such as WC powder). Next the blended powders are mixed to yield a substantially homogeneous powder mixture and a portion of the substantially homogeneous powder mixture is formed into a green body. The body is fired …

Ceramic Dielectrics For High Energy Density Capacity Application, Sheng Chao

Doctoral Dissertations

"The objective of this dissertation is to investigate the relationship between the processing parameters, microstructural development, defect chemistry and electrical properties of titanium oxide (TiO₂) dielectrics for high energy density capacitor applications. The effects of aliovalent dopants on the dielectric properties of TiO₂ ceramics were investigated, aiming to further improve the desired dielectric properties especially at elevated temperatures (up to 200°C). Due to the segregation of acceptor type impurities in the starting powders, space charge polarization took place in TiO₂ ceramics with relative large grain size (>̲500nm), leading to high dielectric loss and low energy storage efficiency. Increased ratio …

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha, Florin Bobaru

Department of Engineering Mechanics: Faculty Publications

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

Phase Equilibria In Iron Phosphate System, Liying Zhang

Doctoral Dissertations

"The main objectives of this research were to synthesize iron phosphate compounds, study phase equilibria in the iron phosphate system, focusing on the glass forming area, and investigate glass formability and properties based on the liquidus regions. Twelve iron phosphate compounds were successfully prepared and studied in terms of liquidus temperature or decomposition behavior. The liquidus surface of the Fe₃PO₇- Fe(PO₃)₃ system was re-determined and found to be significantly different from that originally presented by Wentrup in 1935. Eutectic points exist at 58.0 mole% Fe₂O₃ (1070⁰C), 42.7 mole% Fe₂O₃ (925°C), and 37.0 mole% Fe₂O₃ (907°C). The latter two eutectic points …

The Properties And Structure Of Tin Phosphate Glasses Modified With Other Oxides, Jong Wook (Austin) Lim

Masters Theses

"The main objective of this research was to evaluate the properties and structures of glasses from the stannous (SnO) phosphate system for possible use in low temperature optical applications. Glasses in the binary xSnO-(100-x)P₂O₅ system (50 ≤ x ≤ 70) were prepared and their thermal and optical properties were evaluated. Differences in glass transition temperatures (T_g) measured here and reported in the literature were explained by differences in the residual water content in the glasses, as determined by infrared spectroscopy. In general, increasing the SnO content of the binary glasses increased the refractive index and the glass transition …

Sintering And Microstructural Effects On Mechanical Properties Of Zirconium Carbide-Tungsten Cermets, Melissa M. Giles Craft

Masters Theses

"Zirconium carbide-tungsten cermets were prepared by in situ reaction sintering a mixture of zirconia and tungsten carbide. Tungsten is a refractory metal with a melting point of 3422⁰C; however, its mechanical strength decreases significantly with increasing temperature. One approach to improve the elevated temperature strength is to add ceramic particulates to the matrix. Zirconia and tungsten carbide were compacted and then reacted and sintered in a single step by heating to 2050⁰C. The resulting stoichiometric zirconium carbide-tungsten cermet had a relative density greater than 96%. Cermets with two different grain sizes were produced by altering the final sintering temperature. Sintering …