Ceramic Materials Commons^™

Preface, Delbert E. Day, Günther H. Frischat

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Factors Influencing The Production Rate And Quality Of Lead Sinter, John R. Knoepke, Hung Yang Tsai, Arthur E. Morris

Materials Science and Engineering Faculty Research & Creative Works

The sintering characteristics of a typical Missouri lead concentrate were determined for two types of raw sinter mix: conventionally prepared and pelletized. The important sintering characteristics are sulfur elimination, sinter strength, production rate of sinter, permeability of the sinter bed, and bed temperature. These characteristics were analyzed statistically, and are described by an empirical model, in which proportion of returns, moisture content, air flow, bed height, size distribution of returns, and ignition time are the independent variables. The characteristics of a conventionally prepared sinter mix are most strongly affected by the moisture content of the raw mix. The characteristics of …

Chemical Corrosion Of Ag Films On Glass, Hyun Soo Park

Doctoral Dissertations

"The chemical corrosion of chemically, vacuum and sputter deposited Ag films on an aluminoborosilicate and a soda lime glass was investigated in wet HCl and saturated water vapor as a function of concentration, temperature and time. The higher corrosion resistance of chemically deposited Ag films in comparison to evaporated or sputtered Ag films is attributed to their lower microvoid density and higher adhesion strength. Ag films on the more chemically durable aluminoborosilicate glass had a higher corrosion resistance. Furthermore, films which received a moderate thermal annealing (80 to 140° C) or were deposited on a glass surface washed with HN0 …

Sessile Drop Studies Of Gallium On Alumina, Timothy John Snyder

Masters Theses

"The liquid-vapor and solid-vapor interfacial energies of the system Ga-Al₂O₃ were determined by the sessile drop technique. The interfacial energies were found to decrease with increasing temperature and P₀₂.

A maximum liquid-vapor interfacial energy of 581 ergs/cm² was found for a clean sessile drop at 1227°C. Values for Γ₀, the excess concentration of oxygen, were calculated for both the liquid-vapor and solid-liquid interfaces. The work of adhesion between molten Ga and Al₂O₃ was found to increase with decreasing P₀₂ with a maximum of 576 ergs/cm² occurring …

The Influence Of Manganese Oxide On Sintering Of A Commercial Natural Magnesite., Alamar Kasan Duarte

Masters Theses

"Sintering studies on a commercial natural magnesite have been done to investigate the influence of MnO doping (MnO concentration from 0.16 to 2.50 wt.%) on the densification process over the temperature range 1520 to 1760°C , over periods of time from 3,600 to 57,600s in both oxidizing and reducing atmospheres (Air and P_O2 = 10^-7 KPa. In an air atmosphere the additions of MnO enhances the densification process. This fact may be associated with an increase in lattice diffusion of Mg ions due to an increase in cation vacancies in the MgO lattice from the presence of …

Glass Surfaces Then And Now, Norbert J. Kreidl

Materials Science and Engineering Faculty Research & Creative Works

A reservoir of efficient instrumentation capable of detailed and quantitative exploration of glass surface features is now available in the face of the recognition of their crucial importance for both surface and bulk properties as well as performance. Yet it may be instructive to glance at what had been learned about glass surfaces by investigators before the advent of these intricate tools. Among such earlier findings are the recognition of the altered composition and structure of the surface layer, the extension of this disturbance to considerable depth, the effect of surface structure on adsorption, adhesion, wetting, finishing, etc. and on …

Conduction Polarization In Sodium Germanate Glasses, Akira Doi, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

Only one thermally stimulated depolarization current (TSDC) peak was found in germanate glasses containing from 0.19 to 32.5 mol% Na₂0, whereas comparable silicate glasses exhibit two such peaks. Equations are developed showing that the distortion of the equilibrium Na⁺-ion distribution by an applied electrical field produces a polarization in general agreement with the observed TSDC peak. It is proposed that the TSDC peak is due to dc conduction.

Structure And Properties Of Neodymium Chromite, David Charles Hitchcock

Masters Theses

"Pure, accepton and Al doped NdCrO₃ were prepared by an organo-metallic process.

The crystal structure and lattice parameters were determined by x-ray diffraction. All compositions were orthorhombic Pbnm.

Pellets were pressed from powders of each composition and sintered to high density in a reducing atmosphere. When a small amount of Fe was substituted for Cr, the powder could be sintered in air.

Electrical conductivity for acceptor doped NdCrO₃ varied from about 1 (ohm cm)^-1 at room temperature to about 10 (ohm cm)^-1 at 900°C, about two orders of magnitude higher than the electrical conductivity of the …

Discussion Of "Gas Composition, Temperature, And Pressure Measurements In A Lead Blast Furnace", Arthur E. Morris, John R. Knoepke

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Thermally Stimulated Polarization And Depolarization Current (Tspc/Tsdc) In Glass, Chi-Ming Hong

Doctoral Dissertations

"The feasibility of studying ionic motion in glass using thermally stimulated polarization (TSPC)/depolarization current (TSDC) techniques was investigated with 4Na₂O·96SiO₂ and 30PbO·70SiO₂ (mol%) glasses. The TSDC peaks in these glasses were dependent on glass composition and attributed to bulk polarization. The high temperature background TSPC is shown to be due to dc conductivity, whereas the TSPC/TSDC peaks in the 4Na₂O glass are attributed to shorter range Na⁺ motion.

The electrical conductivity of glasses determined by TSPC agrees well with that measured by conventional ac or dc techniques. The TSPC technique is a rapid and easy method of measuring the …

Properties Of High Alumina Refractories After Exposure To Steam/H₂ Atmospheres, David W. Lang

Masters Theses

"Selected properties of a dense fired alumina, a phosphate-bonded ramming mix, and a calcium aluminate cement-bonded castable were evaluated after exposure at 260°C and 538°C to steam/H₂ atmospheres (2.58, 5.17, and 6.89) MPa. Chemical reactions in the refractories were determined by x-ray diffraction, DTA/TGA, and changes in physical properties. The modulus of rupture (MOR) of the dense alumina decreased with increasing steam pressure and degree of saturation. The calcium aluminate cement phases in the castable were most reactive in 260°C steam and formed several hydrated phases which generally resulted in a higher MOR. The MOR of the ramming mix …

Calcium Migration In Dense Alumina Aged In Water And Physiological Media, Heidi H. Osterholm

Masters Theses

"The flexural strength and relative Ca concentration at the external surface were measured for a dense alumina aged in deionized water and Ringer's solution at 40⁰C for 60 weeks and at 80⁰C for 45 weeks. Changes in the Ca concentration at the external surface and flexural strength during aging were attributed to the dissolution of the calcium impurity believed to be present in a glass phase of unknown composition. Auger electron spectroscopy was used to investigate the relative concentration of the calcium impurity at the external and fracture surfaces of a dense alumina after in vivo exposure for 6, 12 …

Microwave Sintering Of Batio₃ Ceramics, Kurt Duane Humphrey

Masters Theses

"Barium titanate and BaTiO₃-based multilayer capacitors were sintered in a commercial microwave oven. The oven was equipped with a 2.45 GHz continuous-wave magnetron with a maximum power output of 650 watts.

Microwave-absorbing setters made of SiC were used to offset thermal losses from the samples and allow sintering temperatures (>1325°C) to be achieved. Pure samples were pressed from commercial BaTiO₃ powder and microwave sintered to about 90% of theoretical density. Multilayer capacitors were obtained from commercial manufacturers and used in all sintering experiments. A comparison between microwave sintered material and identical samples sintered in a conventional electric furnace revealed …

The System Mgo‐Mgcl2‐H2o At 23°C, Ladawan Urwongse, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

Solubilities of MgO in aqueous HC1 solutions at 23°±3°C were measured and combined with analyses of neat magnesium oxychloride cements, cured in sealed containers, to construct an equilibrium phase diagram for the system MgO‐MgCl2‐H₂O. Specific gravities and acidities of solutions saturated with MgO and relative humidities of vapor phases over sealed samples were measured and combined with XRD data to define the compositions in equilibrium with two crystalline phases. Studies of relative reaction rates indicated that the 5–1–8 phase crystallizes more rapidly than the 3·1·8 phase and that cements near the 3·1·8 composition react rapidly with atmospheric CO …

Phase Relations In Magnesium Oxysulfate Cements, Ladawan Urwongse, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

Solubilities of MgO in H₂SO₄ solutions were measured and X‐ray analyses of over 100 neat cement samples were used to construct an isothermal phase diagram for the system MgO‐H₂SO₄‐H₂O at 23°±3°C. The phases MgO, Mg(OH)₂, 3Mg(OH)₂ MgSO₄·8H₂O (3·1·8), MgSO₄·7H₂O, MgSO₄·6H₂O, and MgSO₄·H₂O were stable at 23°C. The phases Mg(OH)₂· MgSO₄·5H₂O (1·1·5) and MgSO₄·4H₂O were observed but are considered to be metastable, resulting …

Development Of Impervious Low Thermal Expansion Petalite Bodies, Suchinda Chotipanich

Masters Theses

"Impervious petalite bodies were formulated from petalite, lithium aluminosilicate frit and kaolin. Thermal expansion coefficients for selected bodies were less than 2 x 10⁻⁶ /°C(20 - 600 °C). Mineralogy and the reactions in systems containing petalite, lithium aluminosilicate frit and kaolin were observed. Silica-poor high quartz solid solution was found to be the reaction product formed from the reaction between frit and kaolin before conversion to ß-spodumene solid solution at higher temperatures. The crystallization of the ß-spodumene solid solution phases in this system did not occur at the same temperature resulting in variation in the size of the crystallites. The …

Boehmite-Bonded High-Alumina Refractories, Gerhard H. Schiroky

Masters Theses

"High-alumina refractories (99+ % Al₂O₃) were produced by pressing a mixture of 70% tabular alumina and 30% reactive alumina and autoclaving in saturated steam at 1.4 MPa (200 psia)/194 °C to 3.4 MPa (500 psia)/242 °C for 12 to 96 h. Autoclaving converted the reactive alumina to boehmite which acted as the bond phase. At room temperature the MOR ranged up to 37 MPa depending upon boehmite content. The hot-MOR decreased steadily with increasing temperature, but was still 8 MPa at 1400 °C which exceeds that of comparable cement-bonded or conventionally fired high-alumina refractories. The estimated autoclaving costs are lower …

Phase Equilibria In Aqueous Magnesium Chloride, Sulfate, Chromate And Phosphate Systems, Ladawan Urwongse

Doctoral Dissertations

"In the first part of the present study, which is presented in Paper I, solubility of MgO in aqueous HCl solutions at 23° ± 3°C was measured and combined with analyses of neat magnesium oxychloride cements to construct an equilibrium phase diagram for the system MgO-MgCl₂-H₂O. Invariant liquids in equilibrium with Mg(OH)₂ and 5Mg(OH)₂·MgCl₂·8H₂O (5.1.8), with 5·1·8 and 3Mg(OH)₂·MgCl₂·8H₂O (3·1·8), and with 3·1·8 and MgCl₂·6H₂O were located at 0.8 ± 0.2 MgO, 17.0 ±0.5 MgCl₂; at 1.0 …

An X-Ray Diffraction Analysis Of The Lacro₃-Laalo₃ Solid Solution Series, Robin Ashley Murphy

Masters Theses

"A crystallographic study was made of powders from the LaCr_1-x Al_xO₃, La_.90(Mg_.05 Cr_1-x Al_x )_.95O_2.83 , and La_1±xCrO₃ systems. The relationships between composition and thermal expansion, electrical conductivity, and vaporization were also investigated. The x-ray diffraction data of the LaCrCO₃ - LaAlO₃ compounds showed the system to form a single phase solid solution for any given sample from the series. The orthorhombic to rhombohedral phase transition was depressed to below room temperature at approximately 13% Al⁺³ substitution"--Abstract, page ii.

Glass In The Year 2000, Norbert J. Kreidl

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

The Al2o3‐Sio2‐Zro2 Liquidus Surface: A Discussion, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Suggested Chemistry Of Zinc Oxychloride Cements, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

Solutions of ZnCl₂ were prepared from ZnCl₂·nH₂O and by reaction of zinc metal with HCl. Specific gravities and pH values were determined as a function of composition. A ternary phase, 4ZnO·ZnCl₂·5H₂O, was precipitated when the ZnCl₂ solutions were diluted to a pH of 5.48 ± 0.05. Mixtures of ZnO with ZnCl, and HCI solutions were equilibrated in sealed containers and analyzed by X‐ray diffraction. The resulting phase diagram shows 2 ternary phases, 4ZnO·ZnCl₂·5H₂O (4·1·5) and ZnO·ZnCl₂·2H₂O (1.1.2), both of which are soluble …

Subsolidus Equilibria And Stabilization Of Tetragonal Zro2 In The System Zro2‐Al2o3‐Sio2, Charles A. Sorrell

Materials Science and Engineering Faculty Research & Creative Works

The irreversible reaction between zircon and alumina to form mullite and zirconia was observed to proceed very slowly at 1480°C, confirming the existence of a stable join between mullite and zirconia in addition to the join between mullite and zircon. Attempts to determine equilibrium assemblages in powder samples of several combinations of the constituents at 1300° and 1400°C were unsuccessful. Metastable tetragonal ZrO₂ was observed in fired powder samples containing kaolinite, in fired zircon‐alumina samples, and in calcined gels prepared from zirconyl nitrate, aluminum nitrate, and colloidal silica in water. Tetragonal ZrO₂ was the dominant crystalline phase in …

Intermetallic Reactions In Vacuum-Deposited Nickel And Gold Films On (111) Silicon Single Crystals, K. H. Yoon, Gordon Lewis, L. L. Levenson

Materials Science and Engineering Faculty Research & Creative Works

Pure nickel and gold thin films were vacuum-deposited on (111) silicon single crystals. When Ni/Au/Si or Au/Ni/Si samples were heated to about 550° in situ, hexagonal or deformed hexagonal shaped crystallites were formed on the silicon substrates. The composition of these crystallites was determined by using x-ray diffraction, scanning electron microscopy and scanning Auger microprobe methods. The crystallites were identified as NiSi2. The crystal-lites on the (111) silicon plane parallel to the surface appeared as regular hexagons while the inclined crystal-lites resembled trapezia. The results of Auger spectra and in-depth composition profiles for Ni, Au, and Si showed that the …

Electrical Degradation In High Purity Barium Titanate, Jeffrey Duncan Keck

Doctoral Dissertations

"The stability of BaTiO₃-type insulators to DC fields has long been recognized as one of the important factors in determining the quality of a capacitor which uses such a material as its dielectric. The slow increase of the electrical conductivity of an insulator which is stressed by DC fields at levels below the breakdown strength is normally termed degradation. Since degradation is a very common malady to the ceramic capacitor manufacturers, many studies have been conducted over the past two decades in efforts to learn how to remedy the problem.

The results of previous studies have shown that …

Subsolidus Equilibria And Metastable Phase Development In The System Zro₂-Al₂O₃-Sio₂, Charles Christopher Sorrell

Bachelors Theses

"Subsolidus equilibria in the low silica portion of the system ZrO₂-Al₂O₃-SiO₂ were studied by X-ray diffraction of quenched samples fired at 1300°, 1400°, and 1480°C. Samples prepared as powders from combinations of a-Al₂O₃, Al(OH)₃, silicic acid, ZrO₂, and kaolinite reacted very slowly at 1300° and 1400°C and the trends toward equilibria are not apparent. A mixture of zircon and Al(OH)₃ reacted slowly at 1480°C to form mullite and ZrO₂, indicating that the latter phases are the stable assemblage rather than zircon and alumina. A gel prepared from aluminum nitrate, zirconyl nitrate, and colloidal silica reacted at 1480°C to form alumina, …

The Influence Of Oxygen Activity On Sintering Of Strontium Doped Lanthanum Chromite., Leslie Groupp

Masters Theses

"The influence of oxygen activity upon the sintering of lanthanum chromite (La_1-xSr_x CrO₃) with x ranging from Oto 0.2 was investigated using chemically prepared powders of <0.1 microns particle size. The results show that at a temperature of 1740 ° C densities of >92% of theoretical could be achieved if the oxygen activities were maintained in the 10^-11 to 10^-12 atm. range. If oxygen activity exceeds 10^-10 atm., densities of not >80% theoretical could be obtained. For the compositions studied, room temperature X-ray analysis of both the starting powders and sintered compacts show the compositions to be orthorhombic and single phase. The ambient lattice parameters and resistivity measurements decreased …

Effect Of Temperature, Aging, And Composition On Phase Development In The System Al₂O₃-P₂O₅-H₂0., John Allan Middleton

Masters Theses

The chemical and physical conditions for the formation of various phases of aluminum phosphate were studied. Mixtures of Al₂O₃ and H₃PO₄ were aged in sealed containers and examined for phase development by X-ray diffraction. The results revealed the aging of samples to be a critical process for the formation of equilibrium phase assemblages at low temperatures, Initial composition becomes important as equilibrium is neared and at elevated temperatures when the molar ratios of Al₂O₃, P₂O₅, and H₂O determine what phases will be formed. Temperature …

Characterization Of Two Mexican Raw Dolomites For Refractory Brick Production, Rodolfo Trevino Cantu

Masters Theses

"Two Mexican dolomites were characterized in order to discover their suitability for production of refractory brick.

The results were compared with other dolomites from American Companies. Some samples were burned in a gas fired Laboratory Furnace and others were obtained in the burned state after processing in Industrial Rotary Kilns.

The characterization procedures included X-Ray Diffraction, Scanning Auger Microprobe, DTA and TGA techniques, Chemical Analysis and Bulk Density measurements.

The procedure to control the quality of the dead-burned dolomite at the industrial level was established taking as the main criteria, bulk density, hydration susceptibility, and impurity levels"--Abstract, page ii.

Ionic Thermal Current In Sodium-Rubidium Silicate Glasses., Chi-Ming Hong

Masters Theses

"The ionic thermal current (ITC) method has been employed to study alkali ion motion in a sodium silicate glass and two sodium-rubidium silicate glasses over the temperature range 110 ° K to 400 ° K. T wo peaks and three peaks were observed in a l.0Na₂O-3.0SiO₂ glass and a 0.75Na₂O-0.25Rb₂O-3.0SiO₂ glass, respectively. Only one peak and a high temperature shoulder were observed in the 0.50Na₂O-0.50Rb₂O-3.0SiO₂ glass. These peaks were attributed to orientation and space charge polarization with each peak associated with a particular movement of the sodium …