bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid–Solid Equilibria in the System NiO–TiO2–SiO2 in the Temperature Range 1430° to 1660°C
Authors: Roberts Nia F. , Muan Arnulf
Published: March 2005

Equilibrium relations in the system NiO–TiO2–SiO2 in air have been investigated in the temperature range 1430° to 1660°C. The most conspicuous feature of the phase relations is the existence of a cation‐excess spinel‐type phase, in addition to NiO and NiTiO3, on the liquidus surface and at subsolidus temperatures down to 1430°C. Three invariant points have been located on the liquidus. There is a peritectic at 1540°C characterized by coexisting NiO (ss), spinel(ss), cristobalite, and liquid of composition 47 wt% NiO, 29 wt% TiO2, and 24 wt% SiO2. Two eutectics are present, one at 1480°C, with spinel(ss), NiTiO3, cristobalite, and liquid (42 wt% NiO, 43 wt% TiO2, and 15 wt% SiO2), as the coexisting phases. The other is at 1490°C with NiTiO3, rutile, cristobalite, and liquid (32 wt% NiO, 56 wt% TiO2, and 12 wt% SiO2). A liquid miscibility gap extends across the diagram from the two bounding binary systems NiO–SiO2 and TiO2–SiO2.
Activity–Composition Relations in Refractory Oxide Solid Solutions at High Temperatures: The System Cr2O3–Al2O3
Authors: Tsai Hwan‐Tang T. , Muan Arnulf
Published: March 2005

Activity–composition relations in Al2O3–Cr2O3 solid solutions at 1500° and 1600°C were determined by equilibrating members of this solid‐solution series with Mo–Cr alloys of known activity–composition relations and a gas phase of known oxygen potentials. The oxide solid solution shows considerable positive deviation from ideality.
Thermogravimetric Study of the M‐Co‐O System: I, M = Ta and Nb at 1200°C
Authors: Kitayama Kenzo
Published: March 2005

Phase equilibria in the Ta‐Co‐O and Nb‐Co‐O systems have been studied at 1200°C at oxygen partial pressures from 10−0.68 to 10−13.50 atm for the former and from 10−0.68 to 10−13.30 atm for the latter. In both systems, M2CoO6 and M2Co4O9 are stable ternary compounds under the experimental conditions, and a new phase, Nb5Co2O14, has been identified. The Ta‐Co‐O system is simple, whereas the Nb‐Co‐O system is somewhat more complicated because of the extra phase. The lattice constants of the ternary compounds have been determined and compared with previous values. The standard Gibbs energies of reactions have been determined using oxygen partial pressures in equilibrium with three solid phases.
Activity–Composition Relations in the Systems CaO–MnO and MgO–MnO at at 1500° and 1600°C
Authors: Tsai Hwan‐Tang T. , Muan Arnulf
Published: March 2005

Activity–composition relations in CaO–MnO and MgO–MnO solid solutions were determined by equilibrating oxide solid solutions with platinum–manganese alloys under controlled oxygen partial pressures at 1500° and 1600°C. Both systems show considerable positive deviation from ideality.
Role of Selected Cations and Gas Speciation on the Reduction of Fayalite at 1300°C
Authors: Ulmer Gene C. , Elliott William Crawford , Buntin Thomas , Erickson Edwin S. , Friel John J.
Published: March 2005

Pure fayalite liquid was reduced at 1300°C in variable C/H ratio gas mixtures, all with constant fO2 both with and without various cation additives that included Cr2O3, MnO, CaO, TiO2, Al2O3, Na2O, and K2O. Similar studies were also performed on Carol Lake iron ore pellets without these cation additives. The role of cation additives in reduction with CO‐rich gases is minimally important. In hydrogen‐rich reduction studies, the reduction per hour was increased 50% by a 2.5 wt% addition of CaO, increased by about 75% by a 2.5 wt% addition of Cr2O3, and increased by about 50% for a 2.5 wt% addition of MnO as compared to the reduction rate of pure fayalite liquid. Much more dramatic than any cation additive effect is the role of the hydrogen content of the gas mixture. At 1300°C and a fixed –log fO2= 13, the reduction per hour of pure fayalite liquid triples with the replacement of the CO by hydrogen even with just the first 10 vol% of hydrogen. Theoretical discussions of the role of cation additives and gas speciation on fayalite melt structure are presented.
Grain Boundary Sliding Microdisplacement Measurements During the Creep of Alumina
Authors: Blanchard Cheryl R. , Page Richard A.
Published: March 2005

Grain boundary sliding (GBS) is thought to be the principal driving force for the nucleation, growth, and coalescence of grain boundary cavities during compressive creep of polycrystalline ceramics. It has been shown theoretically that stochastic GBS gives rise to continuous cavity nucleation and transient cavity growth and coalescence, eventually leading to crack formation and failure. This paper will show through experimental measurements, using stereoimaging techniques, that GBS is in fact stochastic. Also, mode II GBS, in‐plane grain rotation, and in‐grain shear displacements, strains, and strain rate measurements during creep of Lucalox Al2O3 will be presented. These displacements, measured on a machine vision system, will be presented in terms of the surrounding microstructural constraint and their lack of angular relation to the compressive load axis.
Effect of Crystal‐Axis Orientation on Resonance Mode of BaTiO3 Ceramics
Authors: Ohara Yoshinobu , Koumoto Kunihito , Yanagida Hiroaki
Published: March 2005

BaTiO3 ceramics were fabricated by sintering a mixture of fibrous and commercial powders, and the effects of crystal‐axis orientation on the resonance characteristics of the poled specimens was investigated. Resonance in the radial direction was observed only for the fibrous BaTiO3 ceramic disk. The degree of c‐axis orientation of the sintered compact decreased with an increase in the initial amount of the commercial powder, and the decrease in the degree of orientation caused the appearance of the resonance in the thickness direction.
Models of Fiber‐Matrix Interfacial Debonding
Authors: Steif Paul S. , Dollar Anna
Published: March 2005

Shortcomings of the commonly used criteria for debonding of the fiber‐matrix interface are considered. A criterion which addresses these difficulties is proposed. With this criterion, it is possible to deduce something about the range of validity of Outwater and Murphy's1 widely known approximate formula for debond initiation.
Preparation of Strontium Barium Niobate by Sol–Gel Method
Authors: Hirano Shin‐ichi , Yogo Toshinobu , Kikuta Ko‐ichi , Ogiso Ko‐ji
Published: March 2005

Crack‐free SBN (SrxBa1‐xNb2O6) thin films have been prepared by a sol–gel method with metal alkoxides. A homogeneous and stable precursor solution was obtained from Sr and Ba metal and Nb(OEt)5 in ethanol with a key additive of ethoxyethanol. SBN (where x= 0.5) powder crystallized to orthorhombic phase at 700°C, and then transformed completely to tetragonal phase at 1200°C. The formation of tetragonal SBN was observed on sapphire (R) substrates at 700°C, whereas the tetragonal phase began to appear in the powders at 1000°C. SBN films with highly preferred orientation were successfully synthesized on MgO (100) substrates at 670°C.
Grain‐Boundary and Grain Electrical Resistances in CoxFe3−xO4
Authors: Ferreira António R. , Furtado Carlos S. , Perdigão João M.
Published: March 2005

The complex impedance analysis technique was used to separate the grain‐boundary and grain impedances of ferrites of the system CoxFe3−xO4. All the samples, for x= 0.886, 0.960, 0.980, 0.995, 0.999, 1.005, 1.011, 1.021, 1.041, and 1.126, were fabricated by the traditional routine under the same conditions of preparation and sintering. The variations of both grain‐boundary and grain resistances with temperature were evaluated in the frequency range 100 Hz < f < 40 MHz. The values of the activation energies for both conduction processes were determined from the Arrhenius plots, and the variations of these activation energies and of the resistances at 20° and 150°C were drawn as a function of x. A sharp change in these quantities was observed at the stoichiometric composition (x = 1). Explanations and suggestions for the observed behaviors have been made.
Aids in Hydrothermal Experimentation: II, Methods of Making Mixtures for Both “Dry” and “Wet” Phase Equilibrium Studies
Authors: ROY RUSTUM
Published: March 2005

Various methods for the preparationof mixture for phase equilibrium studies are described. Especial attention has been paid to compositions which cannot be preserved in a glass structure.
Stress–Strain Behavior of Alumina, Magnesia‐Partially‐Stabilized Zirconia, and Duplex Ceramics and Its Relevance for Flaw Resistance, KR‐Curve Behavior, and Thermal Shock Behavior
Authors: Lutz Ekkehard H. , Swain Michael V.
Published: March 2005

The stress–strain behavior for Al2O3 of different grain size, for three different Mg‐PSZ grades, and for various differently composed duplex structures is investigated and compared with their flaw resistance, KR‐curve behavior, and thermal shock behavior measured in previous works. The experimental results seem to reveal that, for most materials, quasi ductility increases with increasing flaw resistance, increasingly pronounced KR‐curve behavior, and increasing thermal shock retained strength. However, brittle ceramics can exhibit rising KR‐curves, whereas pronounced quasiductile materials can exhibit flat KR‐curves. An explanation for the apparent pseudo relationship between quasi ductility and KR‐curve behavior may be that, apart from genuine transformation ductility, most quasi‐ductile effects such as microcracking have only a minor contribution to rising R‐curve behavior, but require the existence of strong residual stresses, which are, on the other hand, responsible for the occurrence of most toughening mechanisms. Also discussed is the influence of microcracking on flaw resistance and thermal shock strength degradation.
Hydration of Tricalcium Germanate–Tricalcium Silicate Solid Solutions
Authors: Sample David , Brown Paul W.
Published: March 2005

The hydration characteristics of solid solutions of composition 3CaO·xGeO2·(1 −x)SiO2 were investigated at 25°C by isothermal calorimetry. The compositions hydrated were for x= 0, 0.2, 0.4, 0.6, 0.8, and 1.0. Full hydration was achieved for compositions in which x < 0.2. Both the rate of hydration and the total heat evolved for complete hydration vary with composition. Hydrate compositions were determined, and these also show a compositional dependence. The hydration product for tricalcium germanate has a Ca/Ge ratio near 1.5. Although the hydration products of the solid solution are far more fibrous, their morphologies are reminiscent of that of calcium silicate hydrate.
X‐ray Diffraction Characterization of the Enamel–Steel Interface
Authors: Mackert J. Rodway , Conner Trent G. , Ringle Robert D. , Parry Edward E. , Fairhurst Carl W.
Published: March 2005

In the enameling of steel, the oxide is generally regarded as being completely dissolved by the fusing enamel, with the enamel–metal bond forming directly between oxide‐saturated glass and metal. According to this model, the adherence of the oxide layer present on the surface of the steel as the enamel begins to fuse is irrelevant, because none of the original oxide layer remains in the matured enamel–steel bond. This model has not been completely verified, however, and some researchers have presented evidence for the presence of a layer of wüstite (FeO) at the enamel–steel interface on the order of 1 to 4 μm in thickness. Whether such a layer exists has important implications regarding the mechanism of enamel–steel adherence. In the present study, a method was developed to concentrate whatever crystalline material might be present in the interfacial zone to make it more amenable to detection by X‐ray diffraction. Through the use of wüstite standards, the present technique was shown to be capable of detecting a layer of wüstite at the enamel–steel interface as thin as 0.3 μm. However, in neither one‐coat nor two‐coat enameling could a layer of wüstite be demonstrated at the enamel–steel interface. Hence, there does not appear to be a 1‐to‐4‐μm‐thick wüstite layer at the enamel–steel interface. If a layer of iron oxide is present at the interface, it must be thinner than 0.3 μm.
Application of Molecular Orbital Calculations to Fracture Mechanics: Effect of Applied Strain on Charge Distribution in Silica
Authors: Wong‐Ng Winnie , White Grady S. , Freiman Stephen W.
Published: March 2005

To further our understanding of the mechanism of environmentally enhanced crack growth, molecular oribital calculations (MO) using the ab initio self‐consistent‐field (SCF) technique have been employed to investigate the effect of applied strain on the atomic charge distribution and the bond overlap population of the Si–O bond at the crack tip of silica. Pyrosilicic acid (H6Si2O7) with eclipsed conformation has been employed as the model molecule. Strain effects up to 20% were simulated in terms of bond stretching and angle distortion. The results indicate that, regardless of how the external strain is applied on the model molecule, the gross electron population on the bridged oxygen increases as strain increases and that on the silicon decreases.
Effects of Dopants on the Complex Impedance and Dielectric Properties of Aluminum Nitride
Authors: Jang Se‐Aug , Choi Gyeong Man
Published: March 2005

Complex impedance patterns of aluminum nitride (AlN) doped with various ions of different ionic sizes and valences have been examined at temperatures between 400° and 950°C. The patterns showed distinct differences between samples doped with ions of different sizes. Grain and grain boundary contributions to the resistance and capacitance were compared. It was found that the grain boundary: grain resistance ratio increases with density. Samples doped with large cations have higher effective dielectric constants at the grain boundary than samples doped with small cations or undoped samples, indicating a thinner grain‐boundary layer.
Processing Temperature Effects on Molybdenum Disilicide
Authors: Wade Robert K. , Petrovic John J.
Published: March 2005

A series of MoSi2 compacts were fabricated at increasing hot‐pressing temperatures to achieve different grain sizes. The materials were evaluated by Vickers indentation fracture to determine room‐temperature fracture toughness, hardness, and fracture mode. From 1500° to 1800°C, MoSi2 had a constant 67% transgranular fracture and linearly increasing grain size from 14 to 21 μm. Above 1800°C, the fracture percentage increased rapidly to 97% transgranular at 1920°C (32‐μm grain size). Fracture toughness and hardness decreased slightly with increasing temperature. MoSi2 processed at 1600°C had the highest fracture toughness and hardness values of 3.6 MPa.m1/2 and 9.9 GPa, respectively. The effects of SiO2 formation from oxygen impurities in the MoSi2 starting powders and MoSi2–Mo5Si3 eutectic liquid formation were studied.
Interaction of a Crack in a Glass Matrix with an Inclined Fiber
Authors: Hillig William B.
Published: March 2005

Studies on crack propagation in a model glass‐matrix composite were undertaken to observe how the crack propagates around a nonfailing elastic reinforcing fiber. The model system consisted of a 1.6‐mm‐diameter ferrous alloy rod embedded in a glass that very closely matched the thermal expansion of the alloy. Cracks were driven through the glass so as to intersect the rod. The crack trajectory, spallation region, and debonding effects are described. A computational model is offered for the spallation needed to accommodate crack opening in the absence of significant matrix compliance.
Measurement of the Oxygen and Impurity Distribution in Polycrystalline Aluminum Nitride with Secondary Ion Mass Spectrometry
Authors: Potter Gregg E. , Knudsen Arne K. , Tou James C. , Choudhury Ashok
Published: March 2005

The lattice oxygen content in sintered polycrystalline aluminum nitride substrates was measured via secondary ion mass spectrometry (SIMS). This was achieved by quantitative analysis of spatial and depth‐resolved ion images of polished specimens using the solid‐state standard addition method. The thermal conductivity of the polycrystalline material, measured with the laser flash technique, was found to be strongly correlated with the oxygen content in the AIN grains. This dependence is similar to that observed in single‐crystal studies and is consistent with the phonon scattering model of AIN thermal conductivity. Scanning electron microscopy and SIMS images of a variety of other species (C, F, Cl, Y, Si, and Ca) were also obtained. In general, impurities were localized within second‐phase regions although calcium was also found to be distributed uniformly along AIN grain boundaries. Other impurity constituents are also discussed.
Phase Relations and Thermodynamic Properties of Condensed Phases in the System Sr–Cu–O
Authors: Jacob K. Thomas , Mathews Tom
Published: March 2005

The phase diagram of the system Sr–Cu–O has been determined at 1173 K. Several compositions in the ternary system were quenched after equilibration, and the phases present were identified by optical microscopy, X‐ray diffraction, and electron proble microanalysis. Four ternary compounds, SrCu2O2, Sr2CuO3, SrCuO2+δ, and Sr14Cu24O41, have been identified. Values for the nonstoichiometric parameter δ in SrCuO2+δ corresponding to the different three‐phase fields have been determined using the hydrogen reduction technique. The thermodynamic properties of all the ternary oxides were determined using solidstate cells incorporating either oxide or fluoride electrolyte. The results from both types of cells were internally consistent. A discrepancy in the recent literature regarding thermodynamic properties of Sr2CuO3 has been resolved. The compound Sr14Cu24O41 has been identified in some of the earlier investigations as Sr3Cu5O8+z˙ Using a novel variation of the galvanic cell technique, in which the emf of a cell incorporating a fluoride electrolyte is measured as a function of oxygen potential of the gas phase in equilibrium with the condensed phase electrode, the formula Sr14Cu24O41 has been confirmed. The compound does not have significant nonstoichiometry. The phase relations in the system Sr–Cu–O have been evaluated as a function of temperature and oxygen partial pressure from the thermodynamic data.
Corrosion of Sic Materials in N2–H2–CO Gaseous Environments: I, Thermodynamics and Kinetics of Reactions
Authors: Butt Darryl P. , Tressler Richard E. , Spear Karl E.
Published: March 2005

Two sintered SiC materials and a siliconized SiC materials were exposed to two gas compositions in the N2–H2–CO system at 1000°–1350°C, 133 Pa and 98.7 kPa for 8–1000 h. The two gases were a nitrogen‐based gas which contained 98.2% N2, 1.2% H2, and 0.6% CO; and an endothermic gas which contained 37.8% N2, 41.1% H2, and 21.1% CO by volume. Thermodynamics of reactions were modeled using the program SOLGASMIX. Kinetic studies were based on weight change measurements obtained from vacuum TGA and long‐term tube–furnace experiments. In the case of a siliconized SiC, reactions were complex, owing to its two phase composition and to the presence of impurities. Under many conditions, silicon was rapidly etched from the surface of the siliconized SiC during a short initial period due to the formation of SiO and carbon or SiO and β‐SiC. In the case of sintered mateials (and the siliconized material during the later stages of corrosion), etching of SiC was observed under many of the conditions studied, due to the apparent formation of SiO, HCN, and/or carbon. Corrosion in an endothermic gas was typically more severe than in a nitrogen‐based gas, due to its higher Pco.
Effects of Green Density on Crystallization and Mullitization in the Transiently Sintered Mullite
Authors: Wang Jia G. , Ponton Clive B. , Marquis Peter M.
Published: March 2005

The effects of green density as an experimental parameter in influencing the crystallization of an amorphous silica layer coated on the surface of α‐alumina powder particles and the subsequent reaction of crystalline cristobalite and alumina to form mullite have been investigated. Green compacts consisting of alumina powder particles coated with an amorphous silica layer were fabricated using both a conventional uniaxial die pressing and rotary forging at room temperature, resulting in various green densities from 15% to 68% theoretical density. It has been shown that both the crystallization temperature of the amorphous silica layer coated on the surface of alumina powder particles and the subsequent mullitization temperature are lowered in the highly compacted materials.
Study of the Bimodal Pore Structure of Ceramic Powder Compacts by Mercury Porosimetry
Authors: Zheng Jingmin , Reed James S.
Published: March 2005

Mercury porosimetry was used to study the pore‐size distribution of both green and partially sintered alumina compacts. Experiments showed that using the mercury‐penetration volume data to study the pore structure changes during sintering for a compact with a bimodal pore‐size distribution could lead to wrong conclusions because the mercury‐penetration volume was not linearly proportional to the porosity. Instead, the porosity distribution should be used. When the porosity of large pores was <10%, some large pores within the compact were observed to become isolated or channeled to the compact surface; this caused errors in the porosity distribution measured by mercury porosity.
Phase Characterization of Lead Zirconate Titanate Obtained from Organic Solutions of Citrates
Authors: Zaghete Maria A. , Santos Carlos O. Paiva , Varela José A. , Longo Elson , Mascarenhas Yvonne P.
Published: March 2005

Lead zirconate titanate (PZT) with several Zr/Ti ratios was prepared by the organic solution of citrates of the respective cations. The Rietveld method was applied to perform quantitative analysis of the coexisting phases. The ratio of tetragonal/rhombohedral phases increased with calcination temperature. For the composition where Zr/Ti = 53/47, the tetragonal quantity varied from 25% to 35% for temperatures ranging from 600° to 800°C. For the powder with Zr/Ti = 57/43, only the rhombohedral phase was observed after calcination at 700°C. For the powder with Zr/Ti = 49/51, only the tetragonal phase was observed after calcination at 800°C. The amount of tetragonal phase was controlled in Zr/Ti = 55/45 by seeding the powder with the tetragonal phase of PZT.
Chemical Kinetic Calculations of the Gas Phase in Filament‐Assisted Chemical Vapor Deposition of Diamond
Authors: Chen Zhong‐jia , Wirtz Gerald P. , Brown Sherman D.
Published: March 2005

A chemical kinetic model was developed for the gas mixture in filament‐assisted diamond chemical vapor deposition (CVD) systems. CH4/H2 mixture was studied as the starting gas mixture. The predictions of gas evolution calculated from this model were used to interpret certain published experimental observations. From the initial analysis, it was concluded that the thermodynamic state of the gas composition determined the effects of transport parameters on diamond growth. In many filament‐assisted diamond CVD systems the gas composition was found to be kinetically controlled. The analysis also suggested that CH3 is a major precursor of diamond films. When CH4/H2/O2 was used as the starting gas mixture, the results indicated that the oxygen additive catalyzed the process to increase the concentrations of CH3 and H, thereby increasing the growth rate and improving the quality of diamond films.
Lead‐Ion Stability in Soda–Lime Lead Silicate Glasses
Authors: Lehman Richard L.
Published: March 2005

Sodium‐calcium‐lead silicate glass compositions were prepared over a wide compositional range by conventional glass‐melting methods. The acid chemical stability of the glass structure was studied by corroding samples of glass in 4% acetic acid solution at 22°C for periods up to 24 h. Lead corrosion stability was evaluated by measuring lead concentrations in the corrosion solution. At short times, parabolic time dependence was observed and the parabolic time coefficients were regressed against composition, yielding a simple additive relationship. A similar model was fitted to 24‐h release data, which showed compositional effects similar to the 2‐h data. Of the oxides studied, sodium was the most detrimental to durability, and the coefficients of the oxides decreased in the series: Na2O, PbO, CaO, SiO2. The effects of the oxides could be partially explained by the number of nonbridging oxygens expected in the glass structure, and the residual effect was attributed to cation characteristics. Small phosphate additions to the glass greatly increased the lead‐ion stability under nearly all experimental conditions examined.
Numerical Integration of the Hereditary Integrals in a Viscoelastic Model for Glass
Authors: Chambers Robert S.
Published: March 2005

Numerical schemes are developed to evaluate the integrals produced by the temporal discretization of the hereditary constitutive equations for a viscoelastic model of glass. Such schemes can be implemented in a material module of a finite element code to provide a general capability for analyzing residual stresses in complicated glass components subjected to nonuniform cooling histories. The robustness of the integration strategy increases the accuracy of a finite element stress analysis, lessens the need for discriminating time step controls, and can reduce the number of time steps required to generate accurate transient solutions incrementally.
Limiting Subcritical Crack Growth in Glass‐Matrix Composites
Authors: Jessen Todd L. , Lewis David
Published: March 2005

Subcritical crack growth measurements were made in borosilicate glass/Fe‐Ni‐Co particulate composites, in which the metal particles were used both as‐received and also with a surface oxidation treatment. No crack growth was observed in the composites containing the partially oxidized particles before catastrophic failure ensued. The composites containing nonoxidized particles did exhibit measurable growth. Fracture surface observations identify strong bonding between the particles and matrix as the main reason for significantly increasing the slow crack growth resistance. This method of “effectively” eliminating subcritical crack growth may be a means by which the design threshold of glasses is raised, thus opening new areas of applications for glass systems.
Kinetics of NiFe2O4 Precipitation in NiO
Authors: Summerfelt Scott R. , Carter C. Barry
Published: March 2005

The kinetics of the precipitation of NiFe2O4 from an Fedoped NiO matrix has been studied. Polycrystalline samples were cooled at a constant rate through the solvus temperature, and the various stages of precipitation were monitored by periodically interrupting the cooling to observe the evolving size, distribution, and morphology of the precipitates. The precipitation occurred primarily by homogeneous nucleation and growth. The coherent precipitates have a dendritic morphology with a large interparticle spacing characteristic of fast precipitate growth. Reasonable rates for the nucleation of NiFe2O4 were observed to occur between 850° and 800°C, resulting in a 350° to 400°C undercooling. Preferential nucleation occurred at grain boundaries, but these particles were only twice as long as those nucleated homogeneously. The size and shape of the precipitates are independent of the distance from the surface, indicating that precipitation occurs by a local arrangement of the Ni and Fe cations and the preexisting cation vacancies.
Mechanical Properties and Oxidation Behavior of Al2O3–AlN–TiN Composites
Authors: Gogotsi Yury G. , Porz Franz , Yaroshenko Viktor P.
Published: March 2005

The study examines the effect which the composition of hot‐pressed electroconductive ceramics has on their structure, mechanical properties, and oxidation behavior, for ceramics of the type AIN–Al2O3–42 wt% TiN, differing in the AIN/Al2O3 ratio. The results are physico‐mechanical property data, including density, hardness, strength, fracture toughness, and wear resistance. A correlation was found between the wear resistance and fracture toughness. The analysis of oxidation products revealed the formation of α‐Al2O3 and rutile in the temperature range from 600° to 1100°C and aluminum titanate above 1200°C. The spallation of the oxide layer caused low oxidation resistance of Al2O3‐rich composites above 1250°C. The oxidation of composites was compared with the oxidation of pure TiN. The relationship is discussed between material properties, composition, phases, and processing parameters.
Calculation of Temperature Distributions during the Solidification Stage in Ceramic Injection Molding
Authors: Zhang Tao , Evans Julian R. G.
Published: March 2005

A finite difference procedure for calculating unsteady‐state temperatures in a molded ceramic–polymer suspension during solidification is described. The method incorporates temperature‐dependent thermal diffusivity and enthalpy of fusion of the polymer. An experimental method is used to assess the surface heat transfer coefficient h at the mold wall. It is found that at low injection pressures h varies with time as the molded body shrinks from the wall, but at high injection pressures h can be treated as constant throughout the solidification stage. Using an analytical method, graphical charts are produced for dimensionless temperature as a function of dimensionless time for values of Biot's modulus in the region relevant to ceramic injection molding.
Solution‐Condensed YBa2Cu3O7 −x Superconductor Thin Films from Thermosetting Metal‐Organic Precursors
Authors: Pak Sung S. , Montgomery Fred C. , Duggan D. M. , Chen K. C. , Mazdiyasni K. S. , Tsai Patricia K. , Paulius Lisa M. , Maple M. Brian
Published: March 2005

Two different multimetal organic compounds were synthesized and used to deposit thin Y:Ba:Cu oxide films on selected metal and ceramic substrates by the dip‐coating method. The rheology of the precursors is strongly influenced by the organic ligand, types of solvent, solvent–water molar ratio, and processing method. The precursor compounds were converted to suitable viscosity to achieve uniform film thickness processing on complex geometry. Superconducting transition temperatures Tc in the range of 89 to 93 K have been measured, depending on processing parameters used. The critical current density, Jc of the solution‐coated films had values comparable to those for poly‐crystalline samples. Y123 films exhibit c‐axis alignment on Ag substrates. A prototype high‐Q cavity was coated with Y123 and its performance was evaluated.
Al2O3─SiC Composites from Aluminosilicate Precursors
Authors: Chaklader Asoke C. D. , Gupta Sankar Das , Lin Edmond C. Y. , Gutowski Boris
Published: March 2005

Al2O3 and SiC composite materials have been produced from mixtures of aluminosilicates (both natural minerals and synthetic) and carbon as precursor materials. These composites are produced by heating a mixture of kaolinite (or synthetic aluminosilicates) and carbon in stoichiometric proportion above 1550°C, so that only Al2O3 and SiC remain as the major phases. A similar process has also been used for synthesizing other composite powders having mixtures of Al2O3, SiC, TiC, and ZrO2 in different proportions (all compounds together or selective mixtures of some of them), as desired. The microstructure of hot‐pressed dense compacts, produced from these powders, revealed that the SiC phase is distributed very homogeneously, even occasionally within Al2O3 grains on a nanosize scale. The homogeneous distribution of SiC particles within the system produced high fracture toughness of the hot‐pressed material (KIC∼ 7.0 MPa · m1/2) and having Vicker's hardness values greater than 2000 kgf/mm2.
R‐Curve Behavior in Zirconia‐Reinforced Molybdenum Disilicide Composites
Authors: Bhattacharya Arun K. , Petrovic John J.
Published: March 2005

R‐curves for hot‐pressed 20 vol% ZrO2 (2.5‐YPSZ and 8‐YPSZ) reinforced MoSi2 composites were evaluated using the indentation/bend technique. Results indicated a modest increase in the material toughness for both composites. Experimental R‐curves were compared with theoretically predicted R‐curves to evaluate the critical transformation stress for the partially stabilized ZrO2 composite. A high critical transformation stress value obtained was indicative of the inhibition of transformation toughening effects due to microstructural inhomogeneity in the partially stabilized ZrO2‐MoSi2 composites.
Quantitative Analysis of the Crystalline Phases in β″‐Alumina‐Based Solid Electrolytes Using X‐ray Powder Diffraction
Authors: Shen Jyung‐Lyang , Howard Scott A. , Liu Jenq , Ownby P. Darrell
Published: March 2005

The resistivity of β”‐alumina‐based solid electrolytes is partially determined by the relative concentration of the phases present in the electrolyte. In order to determine the concentrations of the phases within such electrolytes, several methods of quantitative phase analysis using X‐ray powder diffraction data were investigated. Several analytical equations found in the literature specifically addressing the assay of phases in these systems have been found to be inconsistent. New equations, extended to accommodate the often present sodium aluminate phase, were derived and applied successfully in the calculation of the relative abundance of each phase in calcined electrolyte powders. Verification of the accuracy of these equations was obtained by comparing the results to those obtained from a Rietveld whole‐pattern fitting algorithm.
Glassy Phase in Alumina–Silica Ceramic Shell Molds
Authors: Zhou Wancheng , Zhang Litong , Fu Hengzhi
Published: March 2005

Variation of the amount and the composition of the glassy phase in high‐purity Al2O3‐SiO2 shell molds and the crystallization of the glassy phase have been studied. The results indicate that the two main modes of transformation from a glassy phase to a crystalline phase during firing are (1) formation of mullite through a chemical reaction and (2) devitrification of the glassy phase that comes from the original materials. The transformation is mainly influenced by the S/(A + S) value (A and S are the weight percentages of Al2O3 and SiO2, respectively), the Na2O content, and the firing temperature. Low S/(A+S), low Na2O, and high firing temperature are favorable to the transformation.
Thermodynamic Stability and Mechanisms of Formation and Decomposition of Perovskite Pb(Zn1/3Nb2/3)O3 Prepared by the PbO Flux Method
Authors: Jang Hyun M. , Oh S. Hoon , Moon Jong H.
Published: March 2005

The mechanisms of formation and decomposition of the ferroelectric perovskite PZN [Pb(Zn1/3Nb2/3)O3] were examined. The formation of perovskite PZN from the excess molten PbO environment is characterized by an inititial rapid formation of pyrochlore phase, followed by a subsequent reaction between the intermediate pyrochlore phase, ZnO, and liquid PbO to produce perovskite phase. The pure perovskite PZN crystal prepared by the PbO flux method is thermodynamically unstable over a wide range of temperature (600° to 1400°C), yielding pyrochlore phase and PbO as the decomposition products. The decomposition reaction of perovskite PZN proceeded uniformly with a spatial homogeneity throughout the specimen. The estimated activation energy of the decomposition reaction is approximatley 18 kcal/mol.
The One‐Dimensional Car Parking Problem and Its Application to the Distribution of Spacings between Matrix Cracks in Unidirectional Fiber‐Reinforced Brittle Materials
Authors: Yang Xiao Feng , Knowles Kevin M.
Published: March 2005

Experimental observations of the spacings between cracks formed in the matrix in unidirectional fiber‐reinforced brittle materials in a situation where a tensile stress is applied parallel to the lengths of the fibers, and where the fibers have a longer elongation to failure than the matrix, suggest that the distribution of crack spacings does not follow the one expected on the basis of a model where the matrix cracks at a well‐defined single‐valued stress. A simple model which is able to account for this apparent discrepancy between theory and experiment is developed and discussed.
Effects of Complex Precursors on Alkoxide‐Derived Cordierite Powder
Authors: Okuyama Masahiko , Fukui Toshimi , Sakurai Chihiro
Published: March 2005

Preparation of chemically homogeneous cordierite powders of submicrometer size was investigated using alkoxide precursors, synthesized from Mg metal, Al(OBus)3, and partially prehydrolyzed Si(OEt)4. The amount of partial prehydrolysis water in precursor synthesis was changed to study the effects on the hydrolysis products. In the hydrolysis of the diluted solution of the precursor, product morphology was quite sensitive to the precursor, and different morphologies such as gelation, gel precipitation, and powder precipitation were observed. A redispersable powder of submicrometer size was obtained only from the precursor synthesized at a H2O/Si(OEt)4 ratio of 1.2. Differences were also observed in minor crystalline phases among calcined hydrolysis products. The alkoxide precursors were characterized using Raman spectroscopy, gas chromatography, and NMR spectroscopy. The differences in hydrolysis products are most likely due to differences in hydrolysis and condensation of different chemical species in precursors.
Shape of MgAl2O4 Grains in a CaMgSiAlO Glass Matrix
Authors: Park Sang‐Yeup , Choi Kyoon , Kang Suk‐Joong L. , Yoon Duk N.
Published: March 2005

When sintered Al2O3 is annealed with CaMgSiAlO glass at 1600°C, polyhedral MgAl2O4 grains form and glass pockets are entrapped within the grains. After annealing for 13 h at 1600°C, the liquid pockets show a regular octahedron shape which is expected to represent the equilibrium shape. All grain surfaces in contact with the glass matrix show the same shape. The small grains, which must be shrinking, thus have the equilibrium shape, because their shrinkage shape is is identical to the equilibrium and growth shape. However, the octahedral shape also represents the growth shape for the growing large grains. The grains also form grain boundaries with neighboring grains.
Metal Dopants in Bi‐Pb‐Ca‐Sr‐Cu‐O High‐Tc Superconductor Thick Films Prepared by Melt Solidification
Authors: Tatsumisago Masahiro , Chigusa Hisashi , Tohge Noboru , Minami Tsutomu
Published: March 2005

Metal‐doped superconductor thick films Bi1.6Pb0.4M0.1 Ca2‐Sr2Cu3Ox (M = V, Nb, Mo, In, Sn, Sb, and W) were prepared using a melt–solidification procedure. The optimum heat‐treatment temperature Topt was observed in all the films with different dopants; Topt was related to the temperature at which a partial melting of the films occurred as determined by differential thermal analysis. The dopants in the melt‐solidified films lower the partial melting temperature and thus lower Topt for the formation of the 110 K phase.
Strength of Bottles as Affected by Limitations of Manufacturing Processes *
Authors: Preston F. W.
Published: March 2005

Letter of Transmittal

This paper is part of the proceedings of the Standard Testing Procedure Committee of the Glass Container Association of America. The reasons that caused the Committee to ask for a more or less formal statement of what was known on this subject will be apparent from the paper itself. The members of the Committee, namely, Mr. Bowes, Mr. Flint, Mr. Hiller, Mr. Lyon, and Mr. Roche, as well as Mr. Hendrickson, Mr. Lester, myself, and various others associated with the Committee, have read the paper and offered criticisms. Although we do not necessarily, either as individuals or as a Committee, concur in all that is said, we believe that the paper offers a new approach to some difficult problems connected with strength, a primary concern of the Committee, and that it may act as a basis for industrial advances or for further contributions by others outside the Committee.

V. L. Hall, Secretary, Glass Container Association
Elemental Depth Profiling of Nuclear Waste Glasses after Two‐Years Burial in a Salt Geology
Authors: Lodding Alexander R. , Engström E. Urban , Zoitos Bruce K. , Clark David E. , Wicks George G.
Published: March 2005

Detailed surface compositional analysis has been conducted on 12 simulated nuclear waste forms leached for two years in the brine environment of the Waste Isolation Pilot Plant (WIPP). Secondary ion mass spectrometry (SIMS) of both cations and anions has identified characteristic leaching and precipitation zones within the leached layers on all specimens. The thickness of the leached layers is found to range from approximately 0.3 to 2.7 μm and the total element loss from 80 to 625 mmol/m2, indicating that durability in brine differs by less than an order of magnitude between the different glasses. The in‐depth profiles of anionic elements indicate the significant roles of carbon, fluorine, and chlorine in the formation of surface phases. Also recorded and discussed are elemental SIMS images of sputter crater tapers, providing additional documentation of leaching subzones.
Structure and Bond Strength of a Copper–Alumina Interface
Authors: Yoshino Yuichi , Shibata Takashi
Published: March 2005

Dispite a few studies on the Cu─O eutectic bonding of copper and alumina, the mechanism of Cu─Al2O3 bonding has been unclear to the present, especially with respect to the formation of a reaction phase. The present work reveals that peel strngth decreases and recovers with the concentration of oxygen at the interface, and that the recovery process is rate‐controlled by the diffusion of oxygen in copper. There is a thin, 5‐nm‐thick, reaction layer between the copper and the alumina, which is likely to be amorpous. Incorporating XPS data of the interface, thermodynamic considerations suggest that the reaction phase is CuAlO2. The variation of peel strength is discussed and related to the stability of CuAlO2 and oxygen at the interface.
Cone Crack Nucleation at Sharp Contacts
Authors: Tandon Rajan , Cook Robert F.
Published: March 2005

The distribution of initiation loads for cone cracking during Vickers indentation is studied by direct experimental observation of the indentation process and by simulation. Observations on three different glasses show that cone cracks initiate at the edge of the contact impression and yield distributions of initiation loads with nonzero minima. The simulations, based on a model of an expanding indentation impression in a random array of active crack nuclei, yield distributions of initiation loads with minima of zero. Cone cracks at sharp contacts are concluded to be initiated from nuclei generated by the contact process itself, rather than by nuclei preexisting on the contact surface.
Effect of Additives on Ostwald Ripening of Silver in Glass
Authors: Yata Kunio , Yamaguchi Takashi
Published: March 2005

The effect of additives on the growth of silver particles in a lead borosilicate glass was studied. Growth of silver particles was expressed by the Ostwald ripening theory and controlled by diffusion. Addition of palladium retarded the growth of silver particles. This is attributed to the reduced activity of silver caused by the formation of silver–palladium solid solutions. Addition of ruthenium dioxide promoted the growth, whereas addition of tin dioxide had almost no effect on the growth rate. A “solubility parameter” was introduced to evaluate the temperature dependence of solubility of silver in glass, and the effect of additives has been discussed. Association of diffusion species has been proposed as a possible factor responsible for the temperature dependence of the solubility parameter.
Fabrication of Mullite Body Using Superplastic Transient Phase
Authors: Xue Liang A. , Chen I‐Wei
Published: March 2005

Mullite, an extremely creep‐resistant ceramic, has been fabricated using a novel processing/forming approach taking advantage of superplastic transitional phases. Starting with a mixture of alumina, silica, and a small amount of lithia additive (0.8 wt%), a processing window of about 50°C around 1350°C has been found within which the material can be densified and superplastically deformed with negligible mullitization. The lithia additive promotes a transient lithium aluminosilicate glassy phase that greatly enhances sintering and deformation. The superplastic premullite maintains a nearly constant grain size during deformation between 1250° and 1400°C, over a strain rate from 6 × 10−7 to 10−1 s−1, and has unusually high activation energy values in the range of 1150 to 2086 kJ/mol. An increase in the transient glassy phase content due to the increased matrix dissolution at higher temperatures contributes in part to this anomaly. The mullite work pieces thus shaped become creep resistant again after a postforming annealing/mullitization treatment which decreases the creep rate by 6 orders of magnitude. The mechanical properties (hardness, toughness, and strength) of the finished mullite are compared to those of conventionally processed mullite.
Imaging and Diffraction Study of Continuous α‐Fe2O3 Films on (0001)Al2O3
Authors: Tietz Lisa A. , Carter C. Barry
Published: March 2005

Continuous α‐Fe2O3 films grown on bulk (0001)Al2O2 substrates by low‐pressure chemical vapor deposition have been studied by transmission electron microscopy and the observations compared to those obtained from discontinuous films at an earlier stage of the growth process. Plan‐view specimens revealed significant thermal stress in the continuous films, while cross‐sectional specimens showed that cracking occurs in thicker films. The free surface of the film and the film/substrate interface appeared sharp and flat, apart from growth ledges and steps. Weak‐beam imaging revealed a hexagonal misfit dislocation network consisting of perfect edge dislocations. Fine structure in the selected‐area diffraction patterns which corroborates these observations is also discussed. The misfit network of partial dislocations previously observed in the discontinuous films was not observed for the continuous films, indicating an effect of film thickness, growth rate, or surface preparation on the Fe2O3/(0001)Al2O3 interface structure.
Preparation of Zirconia‐Toughened Bioactive Glass‐Ceramic Composite by Sinter–Hot Isostatic Pressing
Authors: Kasuga Toshihiro , Nakajima Kiichi , Uno Tomoko , Yoshida Masahiro
Published: March 2005

High‐strength bioactive ceramics, MgO‐CaO‐SiO2‐P2O5 glass‐ceramic composites toughened by zirconia, were prepared by sinter‐hot isostatic pressing (sinter‐HIPing) to achieve easier mass production and higher reliability. Raw materials for preparing a dense presintered body were investigated to obtain almost complete densification by sinter‐HIPing. It was found that the densification of a presintered body was influenced by residual glassy phases in the crystallized glass particles. By using a controlled crystallized glass powder and a zirconia powder as raw materials, a presintered body with a relative density higher than 94% was prepared, and then it was densified to near its theoretical density by sinter‐HIPing. This bioceramic exhibited an extremely high bending strength of 400 to 1000 MPa and fracture toughness of 3 to 5 MPa.m1/2 for 30 to 80 vol% of zirconia.
Ultrasonic Evaluation of Oxygen Content, Modulus, and Microstructure Changes in YBa2Cu3O7–x Occuring During Oxidation and Reduction
Authors: Roth Don J. , DeGuire Mark R. , Dolhert Leonard E.
Published: March 2005

Ultrasonic velocity measurements were used to evaluate the effects of oxidation and reduction on the oxygen content, elastic properties, and global microstructure of the YBa2Cu3O7–x ceramic superconductor for samples ranging from 70% to 90% of theoretical density. Bulk density, velocity, and Young's modulus generally increased with increasing oxygen content upon oxidation, and this behavior was reversible. Velocity image patterns obtained from ultrasonic scans were similar after oxidation and reduction treatments for a 90% dense sample, although the velocity value at any given point on the sample was changed following the treatments. The unchanging pattern correlated with destructive measurements showing that the spatial pore distribution (fraction and size) was not measurably altered after the treatments. Changes in superconducting behavior, crystal structure, and grain structure were observed consistent with changes in oxygn content.