bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Toughness Anisotropy of Sodium β‐ Alumina
Authors: Hitchcock David C. , De Jonghe Lutgard C.
Published: June 2006

The fracture toughness anisotropy was determined for sodium p‐alumina single crystals, using a hardness indent method. For cracks with a habit plane normal to the 00.1 planes, the fracture toughness is ∼2 MPa.m112, whereas for cracks running parallel to the 00.1 planes, it is ∼0.16 MPa.m112. This extreme anisotropy may partly explain the difference between calculated and observed critical current densities jor mode I failure initiation of poly crystalline solid electrolytes.
Precursor Powders for Sulfide Ceramics Prepared by Evaporative Decomposition of Solutions
Authors: Chess Daniel L. , Chess Catherine A. , White William B.
Published: June 2006

Precursor oxide powders for the synthesis of ternary sulfide ceramics can be prepared by the evaporative decomposition of nitrate solutions. The oxides can be sulfidized inflowing H,S at 1000 C with little grain growth. Ceramics prepared by direct sintering of these powders in flowing H0S have a much lower porosity than ceramics prepared from conventionally fired powders and sintered under identical conditions. Particle sizes are in the micrometer size range, in agreement with calculation.
Preparation of Rapidly Quenched Glasses in Pseudobinary Systems Composed of Lithium Ortho‐Oxosalts
Authors: Tatsumisago Masahiro , Narita Hiroshi , Minami Tsutomu , Tanaka Masami
Published: June 2006

Twin‐roller quenching was attempted for 15 pseudobinary systems combining two chosen from the lithium ortho‐oxosalts, i.e. Li3BO3, Li4SiO4, Li4GeO4, Li3PO4, Li2SO4, and Li2WO4. Glassy flakes were obtained in almost all systems. Glass formation was easier in systems containing large amounts of Li3BO3 or Li2WO4 compared to those containing Li4GeO4 or Li3PO4. Glass transition, crystallization, and liquidus temperatures were determined. Infrared spectra revealed that the glasses consisted of Li+ ions and discrete ortho‐oxoanions only.
Three Crystalline Polymorphs of KFeSiO4, Potassium Ferrisilicate
Authors: BENTZEN JANET J.
Published: June 2006

Orthorhombic α‐KFeSiO4 (a=0.5478, b=0.9192, c=0.8580 nm), hexagonal β‐KFeSiO4 (a=0.5309, c=0.8873 nm), and hexagonal γ‐KFeSiO4 (a=0.5319, c=0.8815 nm) were synthesized by devitrification of KFeSiO4 glass. Powder X‐ray diffraction data are given for all three polymorphs. Alpha KFeSiO4, the high‐temperature polymorph, melts congruently at 1197°± 2°C. Mössbauer spectroscopy of the α phase indicates that Fe3+ occupies two tetrahedral sites in the lattice. Beta KFeSiO4, the low‐temperature polymorph, and γ‐KFeSiO4, a metastable polymorph, appear to be isomorphous with kalsilite, KAISiO4, and synthetic kaliophilite, KAISiO4, respectively, and it is proposed that β‐ and γ‐KFeSiO4 are linked by Si‐Fe order‐disorder. Beta KFeSiO4 transforms slowly into α‐KFeSi04 above 910°C but the transformation was not shown to be reversible in the present dry‐heating experiments.
Slow Crack Growth Behavior in Transformation‐Toughened Al2O3‐ZrO2(Y2O3) Ceramics
Authors: BECHER PAUL F.
Published: June 2006

Significant increases in the critical fracture toughness (KIC) over that of alumina are obtained by the stress‐induced phase transformation in partially stabilized ZrO2 particles which are dispersed in alumina. More importantly, improved slow crack growth resistance is observed in the alumina ceramics containing partially stabilized ZrO2 particles when the stress‐induced phase transformation occurs. Thus, increasing the contribution of the ZrO2 phase transformation by tailoring the Y2O3 stabilizer content not only increases the critical fracture toughness (KIC) but also the KIa to initiate slow crack growth. For example, crack velocities (v)≥10–9 m/s are obtained only at KIa≥5 MPa.m1/2 in transformation‐toughened (KIC=8.5 MPa.m1/2) composites vs KIa≥2.7 MPa.m1/2 for comparable velocities in composites where the transformation does not occur (KIC=4.5 MPa.m1/2). This behavior is a result of crack‐tip shielding by the dissipation of strain energy in the transformation zone surrounding the crack. The stress corrosion parameter n is lower and A greater in these fine‐grained composite materials than in fine‐grained aluminas. This is a result of the residual tensile stresses associated with larger (≥1 μm) monoclinic ZrO2 particles which reside along the intergranular crack path.
Dynamic Fatigue of a Machinable Glass‐Ceramic
Authors: SMYTH KATHRINE K. , MAGIDA MATTHEW B.
Published: June 2006

To assess the stress‐corrosion susceptibility of a machinable glass‐ceramic, its dynamic fatigue behavior was investigated by measuring its strength as a function of stress rate. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for components of this material. This material was concluded to have only moderate resistance (N=30) to stress corrosion in ambient conditions. The effects of specimen size on strength were assessed for the material used in this study; it was concluded that the Weibull edge‐flaw scaling law adequately describes the observed strength‐size relation.
X‐Ray Scattering Studies of Glasses in the System ZrF4‐BaF2
Authors: COUPÉ RÉJANE , LOUËR DANIEL , LUCAS JACQUES , LÉONARD ANDRÉ J.
Published: June 2006

A Fourier analysis of X‐ray scattering by glasses in the system ZrF4‐BaF2 is presented. The first peak in the radial distribution functions occurs in the range 0.209 to 0.211 nm; the average coordination numbers estimated for the zirconium atom are in the range 7.08 to 8.35, depending on the chemical composition. The second peak has been broken down into two components attributed to two kinds of Ba‐F distances, 0.261 to 0.266 and 0.307 to 0.319 nm, with a corresponding coordination number of barium with respect to fluorine atoms ranging from 8.70 to 10.68. Interpretation of the cation‐cation region is suggested; the average angle values of the Zr‐F‐Zr bridge bond, varying from 150° to 160° prevent two neighboring zirconium atoms from being bonded through two fluorine atoms. Comparative discussions with crystalline structures of fluorozirconates are presented.
Effect of Chemical Composition on the Sinterability of Ultrafine Sic Powders
Authors: Hojo Junichi , Miyachi Kenji , Okabe Yasuzo , Kato Akio
Published: June 2006

Ultrafine β‐SiC powders with an average particle size of 0.01 to 0.06 μm were produced by CVD methods. When these powders contained enough carbon to remove impurity oxygen, sintered bodies with a relative density >95% were uchieved at 2050°C in the presence of 1 wt% boron. The Vickers microhardness reached 21 to 25 GPa at a density of ∼95%.
New Method for solid‐state Bonding Between Ceramics and Metals
Authors: Suganuma Katsuki , Okamoto Taika , Shimada Masahiko , Koizumi Mitsue
Published: June 2006

A new method, for solid‐state bonding between ceramics and metals was developed. An interlayer, which is a composite of the materials to be bonded, is used. The technique can be applied to materials which cannot be bonded by conventional diffusion‐bonding methods because of thermal‐expansion mismatches. It is ex pecked that the bonded materials will have excellent thermal shock resistance.
Finite Difference Numerical Analysis of Phase‐Boundary Reaction Models for Cesium Penetration Into Glass
Authors: FRUEHOLZ R. P. , WUN‐FOGLE M.
Published: June 2006

Experimental data for the phase‐boundary reaction and subsequent diffusion occurring when glass surfaces are exposed to aqueous Cs were theoretically analyzed. Partial differential equations resulting from a surface reaction followed by three possible modes of penetration: (a) simple diffusion, (b) interdiffusion, and (c) double diffusion of Cs, were numerically solved using a finite difference technique. A model in which aqueous Cs+ is assumed to react rapidly with a time‐dependent number of glass surface sites, followed by double‐diffusion penetration, produced the best agreement with experiment. Cesium diffusion coefficients of 2.10‐16 and 3.10‐17 cm2/s were obtained. The value of the finite difference solution technique is also discussed.
Structural Characterization of the Spinel Phase in the Kaolin‐Mullite Reaction Series Through Lattice Energy
Authors: MAZUMDAR S. , MUKHERJEE B.
Published: June 2006

Kaolinite undergoes structural transformation on heating. X‐ray photographs reveal the existence of a spinel‐type phase when kaolin is heated at 980°C. The kaolinite decomposes into a spinel phase with the expulsion of silica. A controversy arises as to whether the spinel phase is γ‐Al2O3 or Si‐Al spinel. Calculating the lattice energies of the structures confirms that the spinel phase is γ‐Al2O3 and not Si‐Al spinel, as proposed earlier. The heat involvement in phase transformation, as obtained from experimental observation at 980°C, is also explained in the light of lattice energies.
Sub‐Sub‐Tg Enthalpy Relaxation in a B2O3 Glass
Authors: CHEN H. S. , KURKJIAN C. R.
Published: June 2006

Enthalpy relaxation processes in a B,O3 glass were investigated calorimetrically in the temperature region from well below to near the glass‐transition temperature Tg. The low‐temperature (TaTg‐ 100 K) or sub‐sub‐Tg anneals stabilize the glass structure. On heating, the annealed sample shows an excess endothermic peak above the annealing temperature Ta, and gradually recovers the original enthalpy without heating through Tg. The enthalpy relaxation evolves in a continuous manner with annealing time as seen in the recovery process. As Ta approaches Tg, a gradual transformation of the sub‐sub‐Tg behavior to that characteristic of the sub‐Tg anneal occurs. The relaxation spectrum exhibits a broad distribution of relaxation times with activation energies of ∼ 105 J/mol. The so‐called β distribution commonly used in the analysis of the sub‐Tg relaxation processes is seen to be too narrow to describe the sub‐sub‐Tg behavior. Possible mechanisms for the sub‐sub‐Tg relaxation phenomena are proposed.
Chemical Analysis of Bi‐Containing Magnetic Bubble Garnet Films
Authors: LUTHER L. C. , KOMETANI T. Y.
Published: June 2006

Elemental compositions of Bi‐containing garnet films suitable for 4 μm period magnetic bubble devices were determined by gravimetric and atomic spectroscopic techniques. The analytical results were found to be in substantial agreement with estimates from material property measurements and, in particular, to validate a method of estimating Bi content from Faraday rotation measurements alone. Both Pb and Pt were found to be present at concentrations of 0.02±0.01 atoms per formula unit.
Fracture Behavior of the Space Shuttle Thermal Protection System
Authors: KOMINE ATSUTOMO , KOBAYASHI ALBERT S.
Published: June 2006

Stable crack‐growth and fracture‐toughness experiments were conducted using precracked specimens machined from LI‐900 reusable surface insulation (RSI) tiles of the space shuttle thermal protection system (TPS) at room temperature. Similar fracture experiments were conducted on fracture specimens with preexisting cracks at the interface of the tile and the strain isolation pad (SIP). Stable crack growth was not observed in the LI‐900 tile fracture specimens which had a fracture toughness of 12.0 kPaμm. The intermittent subcritical crack growth at the tile‐pad interface of the fracture specimens was attributed to successive local pull‐outs due to tensile overload in the LI‐900 tile and cannot be characterized by linear elastic fracture mechanics. No subcritical interfacial crack growth was observed in the fracture specimens with densified LI‐900 tiles where brittle fracture initiated at an interior point away from the densification.
Stress Transmission During the Compaction of a Spray‐Dried Alumina Powder in a Steel Die
Authors: DIMILIA ROBERT A. , REED JAMES S.
Published: June 2006

Stress transmission through the compact, die wall friction, and the radial/axial stress ratio were investigated using a spray‐dried alumina powder containing 2.3% polyvinyl alcohol binder, stored at 15, 55, or 92% rh, and an unlubricated/lubricated steel die for pressing. Stress transmission was enhanced by lubricating the die and decreasing the thickness/ diameter of the compact. Increasing the punch velocity in the range 0.006 to 0.6 cm/min improved the stress transmission for powder stored at the highest humidity, but only in the intermediate range of pressures. Radial stress at the highest pressures (>107 Pa) was essentially independent of the properties of the binder phase and the radial/axial stress ratio was ∼0.4. At high pressures, the product of (die wall friction) (radial/axial stress ratio) decreased with lubrication of the die and storage of the granulated powder at a higher percent relative humidity (softer granules).
Effect of Initial Grain Size on Fission Gas Release from Irradiated UO2 Fuel
Authors: Hastings Ian J.
Published: June 2006

Uranium dioxide fuel with initial grain sizes from 8 to 80 μm was irradiated at linear ratings of 50 to 65 kW/m to a maximum burnup of 230 MW*h/kg U (10000 MW.d/metric ton U). At a linear power of 50 kW/m, where grain growth is not significant, a large initial grain size reduced fission gas release; above 50 kW/m, the results were inconclusive, but a large initial grain size appeared less effective in reducing release.
CO2 Retention in High‐Alkali Borate Glasses
Authors: Martin Steve W. , Cooper Emanuel I. , Angell C. Austen
Published: June 2006

A study of the high‐alkali region of glass formation in the system Na2O +B2O3 reveals that retention of CO2 from carbonate starting materials can become a serious preparative problem at the high‐alkali extreme. Results presented for glasses prepared using both Na2O and Na2CO3 show that residual CO2 can lead to major differences in physical properties which in this work are represented by the viscosity‐related glass transition temperature.
Effect of Gamma Irradiation on Simulated Waste Glass Leaching and on the Leach Vessel
Authors: Strachan Denis M.
Published: June 2006

Concern over the low resistance of teflon to radiation‐induced damage leads to the requirement that, when teflon leach vessels are used, the exposure limit is 1 × 105 rad of beta or gamma radiation during a leach experiment. This limit is supported for MCC 76–68 simulated waste glass by the present investigation.
Twinning Shear in Alumina
Authors: Scott William D.
Published: June 2006

The homogeneous shear necessary to reorient a lattice into twin orientation can be calculated precisely from crystallographic lattice dimensions. Measurement of the surface tilt produced by rhombohedral twins in Al2O3 agrees well with the calculated value, indicating that significant additional shear from the motion of glide dislocations is not contributing to twin deformation.
Use of Autocorrelation Analysis in the Evaluation of Piezoelectric Coupling of Modified PLZT Ceramics Subjected to High Electric Fields
Authors: Jemna Irina , Luca E. , Nicolau P. , Tǎnǎsoiu C. , Ioan C.
Published: June 2006

Two piezoelectric materials were investigated in electric fields, up to 3 kV/cm to determine whether single‐sample testing can be used to evaluate piezoelectric coupling. Autocorrelation analysis of the data showed that the minimal increment of electric field necessary for successive independent measurements on single specimens is 1.3 kV /cm. This value coincides with the breakage field of the sample at resonance. Electrumechanical performance can still be evaluated with a sampling interval slightly lower than 1.3 kV/cm.
Preparation and Thermal Behavior of Magnesium‐Germanium Hydroxide
Authors: Yamaguchi Osamu , Matumoto Hiroshi , Morikawa Shinichi , Shimizu Kiyoshi
Published: June 2006

Poorly crystallized Mg3Ge2O5(OH)4 powder was prepared by simultaneous hydrolysis of magnesium and germanium alkoxides, followed by washing and drying. When this material is heated, spinel‐type Mg2GeO4 and MgGeO3 crystallize at 580° to 850°C and 860° to 1070°C, respectively. The spinel subsequently transforms to the olivine‐type structure at 940° to 1050°C. Both Mg2GeO4 and MgGeO3 crystallize directly from an amorphous phase.
Liquid‐Phase Sintering of TiC‐Ni Composites
Authors: MILLER DANIEL J. , PASK JOSEPH A.
Published: June 2006

The sintering of TiC‐Ni particle compacts was studied with specific attention to effects of processing conditions. Densification was progressively inhibited with the increasing additions of free carbon to the system. These results are explained on the basis of changes in the eutectic reactions in the system, reduced solubility of TiC in the Ni‐rich liquid, and decreased wetting of the solid by the liquid. Presintering hydrogen heat treatment reduced the carbon content of the TiC‐Ni compacts and led to reduction in sintering rates and elevated temperatures of liquid‐phase formation. Wetting experiments with hydrogen‐treated materials showed a time‐dependent wetting angle. These results are discussed based on wetting theory and reactions predicted by the equilibrium ternary‐phase diagram.
Energy Principle of Elastic‐Plastic Fracture and Its Application to the Fracture Mechanics of a Polycrystalline Graphite
Authors: SAKAI MOTOTSUGU , URASHIMA KAZUHIRO , INAGAKI MICHIO
Published: June 2006

Utilizing loading‐unloading procedures on the basis of nonlinear energy principles, an empirical method for evaluating the nonlinear fracture mechanics parameters, i.e. the nonlinear energy toughness Gc, the crack growth resistance R, the Jc value, and the plastic energy dissipation rate φp, was established. These parameters were experimentally determined for an isotropic polycrystalline graphite enabling the elastic‐plastic fracture mechanics of graphite to he addressed. The graphite exhibits a typical elastic‐plastic fracture with ×38% of the total fracture energy consumed as plastic energy. It was concluded that the widely used assumption of the applicability of linear elastic fracture mechanics to polycrystalline graphites can lead to erroneous results if the fracture tests are conducted with the usual specimen size. The proposed experimental method for evaluating elastic‐plastic fracture parameters is potentially very effective for studying various nonlinear fractures in other ceramic materials.
Structure and Properties of Rapidly Quenched Li2O‐Al2O3‐Nb2O5 Glasses
Authors: TATSUMISAGO MASAHIRO , HAMADA AKIRA , MINAMI TSUTOMU , TANAKA MASAMI
Published: June 2006

In the system Li2O‐A12O3‐Nb2O5, glasses were prepared in a wide range of compositions using a twin‐roller quenching technique. The glass‐transition temperature, ranging from 495° to 780°C, was primarily determined by the Li2O content and was independent of the Al2O3 and Nb2O5 contents in the composition region with the Li2O/Nb2O5 ratio smaller than unity, whereas it increased with the replacement of Nb2O5 by A12O3 in the region of the ratio larger than unity. Although the conductivity, ranging from 10‐9 to 10‐5Ω‐1 cm‐1 at 500 K, was also primarily determined by the Li2O content, it tended to decrease slightly as Nb2O5 was replaced by A12O3 in glasses containing a given Li2O5 content; such a tendency was pronounced in the composition region with the Li2O/Nb2O5 ratio larger than unity. Ir spectra and the chemical shifts of AIKα X‐ray fluorescence lines of the glasses revealed that aluminum ions in the glasses with the Li2O/Nb2O5 ratio smaller than unity were mainly in the octahedral coordination state, Aloe, and that, when the ratio exceeded unity, the amount of the tet‐rahedrally coordinated aluminum ions AlO4 increased with increasing Li2O/Nb2O5 ratio.
Oxygen Self‐Diffusion in Single‐Crystal Y2O3
Authors: Ando Ken , Oishi Yasumichi , Hase Hiroyuki , Kitazawa Koichi
Published: June 2006

Self‐diffusion coefficients of the oxygen ion in single‐crystal Y2O3 were determined by the gas‐solid isotope exchange technique. The results in the range 1100° to 1500°C are described by D=7.3 X 10‐6 exp [‐19l(kJ/mol)/RT] cm2/s. Comparison of the results with those for oxides with the fluorite‐type structure indicates that the regularly arranged vacant anion sites in the C‐type structure do not contribute eflectively to oxygen ion diffusion.
Properties of Glass/Alumina Composites
Authors: Higby Paige L. , Shelby James E.
Published: June 2006

The density, transformation range behavior, and ac conductivity of composites of spherical alumina particles dispersed in sodium borosilicate glasses were measured. The values of density and electrical conductivity obtained were compared to those calculated using common models.
A Practical Technique for Investigating the Fracture Properties of Clay‐Based Ceramics by Diamond Indentation
Authors: Rose Michael E. , Burke Carin M.
Published: June 2006

A method is described for investigating the fracture properties of vitreous clay‐based ceramics. It involves indenting the specimen with a Vickers diamond in‐denter under paraffin oil and revealing the radial cracks so formed with the aid of insoluble dye particles. Typical results are quoted for soda‐lime glass and two electrical porcelains. It is suggested that differences in behavior of the porcelains can be attributed to the toughening effect of microcracks.
Temperature Dependence of Young's Modulus and Internal Friction in Alumina, Silicon Nitride, and Partially Stabilized Zirconia Ceramics
Authors: Shimada Masahiko , Matsushita Ken'ichi , Kuratani Shusei , Okamoto Taira , Koizumi Mjtsue , Tsukuma Koji , Tsukidate Takaaki
Published: June 2006

The temperature dependence of Young's modulus and internal friction (Q−1)in alumina, silicon nitride, and partially stabilized zirconia (Y‐PSZ) ceramics was studied. Little change in Q−1 was found for alumina, whereas Q−1 for silicon nitride ceramics increased above 700°C. The Q−1 of Y‐PSZ increased markedly with increasing temperature up to a peak at ∼200°C.
Hot Isostatic Pressing of Nuclear Waste Glasses
Authors: Harker Alan B. , Morgan Peter E. D. , Flintoff John F.
Published: June 2006

Borosilicate glass and glass‐ceramic forms were prepared from simulated Savannah River Plant high‐level nuclear waste by hot isostatic pressing. This process allows glass forms to be consolidated at temperatures as low as 850°C, removes viscosity constraints on frit selection, eliminates Cs volatilization, and permits waste loadings of 50 wt%. Actinide leach resistance of the glass form was improved by using redox control to induce formation of a minor uraninite crystalline phase.
Analogy Between Mechanical and Dielectric Strength Distributions for BaTiO3 Ceramics
Authors: Yamashita Kimihiro , Koumoto Kunihito , Yanagida Hiroaki , Hamano Takashi
Published: June 2006

Mechanical and dielectric strengths were measured for BaTiO3, ceramics at room temperature. The results were evaluated in terms of Weibull statistics, and a clear analogy between the mechanical and dielectric strength distributions was found.
Sinterability of Agglomerated Powders
Authors: LANGE F. F.
Published: June 2006

A concept is presented which relates the sinterability of a powder compact to its particle arrangement as defined by the distribution of pore coordination numbers, i.e., the number of touching particles surrounding and defining each void space. Previous thermodynamic arguments suggest that pores will disappear only when their coordination numbers are less than a critical value. The coordination‐number distribution of an agglomerated powder is discussed with respect to the size of the multiple‐particle packing unit, consolidation forces, and phenomena occurring during sintering. One pertinent conclusion is that the multiple‐particle packing units densify and support grain growth as sintering initiates. Grain growth and rearrangement processes decrease the coordination number of remaining pores to allow them to disappear during latter states of sintering. Porosimetry and direct observations of powder compacts of <1 μm Al2O3 heat‐treated between 600° and 1600°C support this concept.
Microstructure, Strength, and Oxidation of a 10 wt% Zyttrite‐Si3N4 Ceramic
Authors: DUTTA SUNIL , BUZEK BRUNO
Published: June 2006

Hot‐pressed Si3N4 doped with 10 wt% zvttrite as a sinterine aid was studied. An equiaxed, fine‐grainid microstructure was predominant, with no apparent porosity. Bend strengths were determined at room temperature and high temperatures (up to 1370°C/2500°F). Oxidation was measured by weight gain at 1370°C in air. The resulting material exhibited very good room‐temperature strength (755 MPa/110 ksi). The work showed that room‐temperature strength can be improved significantly by using controlled Si3N4 powder with 10 wt% zyttrite. High‐temperature strength (514 MPd75 ksi) at 1370°C was nearly double that of hot‐pressed Si3N4 (NC‐132). The oxidation resistance at 1370°C was also higher than that of NC‐132.
Lattice Modification in Ion‐Implanted Ceramics
Authors: McHARGUE C. J. , YUST C.S.
Published: June 2006

The effect of ion implantation on alumina (Al2O3) and silicon carbide (SiC) was investigated by Rutherford backscattering (RBS), indentation hardness, fracture toughness, transmission electron microscopy (TEM), and linear scratching with a diamond stylus. The implanted (10l6 to 1017 Cr.cm−2 at 280 to300 keV, 1 to 4 |MX 10l6Ti.cm −2at 150 keV,2 |MX 1016Zr.cm−2 at 150 keV) AI2O3 lattice is significantly damaged but remains crystalline; the lattice hardness increases, and the scratched surface is less sensitive to fracture. The implanted (1013 to 10l6 N.cm−2 at 62 keV, 1014 to 10l6 Cr.cm −2 at 280 keV) Sic lattice becomes amorphous to a depth of 250 nm, becomes less hard, and deforms without fracture when scratched. The variation in Rutherford backscattered spectra and in surface hardness with annealing are reported and interpreted in terms of lattice defects for the Al2O3 specimens.
Grain Growth in CaO‐Stabilized ZrO2 in the Presence of a Liquid Phase
Authors: Dou Shixue , Pacey Philip D. , Masson Charles R. , Marple Basil R.
Published: June 2006

Calcia‐stabilized zirconia, CSZ (7.5 wt% CaO), with impurities of A12O3, SiO2, MgO, Fe2O3, and TiO2, was sintered in air at 1783 K for times (t) up to 230 h. The microstructure consisted of grains of CSZ with small amounts of pores and a CaO‐Al2O3‐SiO2 eutectic. Grain diameters grew in proportion to t1/3. The results are consistent with a mechanism in which grain growth is limited by diffusion of Zr4+ ions through the liquid eutectic.
Residual Stresses and Cracking in Metal/Ceramic Systems for Microelectronics Packaging
Authors: HSUEH C. H. , EVANS A. G.
Published: June 2006

Residual stresses that develop in a metal/ceramic system due to thermal expansion mismatch were calculated for a work‐hardening metal. The calculations were conducted for a cylindrical configuration, pertinent to certain microelectronics packaging systems. Experimental measurements of the stress have also been made on a Cu/cordierite ceramic system, using an indentation technique. It is shown that porosity in the metal can plastically expand and provide a mode of dilatational relaxation. Porosity in the metal thus emerges as an important stress‐relaxing mechanism.
Time‐Dependent Strength of Siliconized Silicon Carbide under Stress at 1000° and 1100°C
Authors: CARROLL D. F. , TRESSLER R. E.
Published: June 2006

The time‐dependent strength of a fine‐grained siliconized silicon carbide under stress at 1000° and 1100°C was investigated. Both macroscopic stress redistribution and localized flaw blunting were found to contribute to the strengthening of siliconized silicon carbide in bending tests. Strengthening through macroscopic stress redistribution involved nonlinear creep behavior which decreased the maximum outer fiber stress in the bending beam. Localized flaw blunting processes were determined to be operative in this material through artificial flaw tests using a prestress to prevent flaw healing. The sharp artificial cracks were blunted during static load tests by localized deformation processes at the crack tip.
Sodium Transport in the Na2O‐H2O‐SiO2 Glass System
Authors: MOLINELLI JOYCE , TOMOZAWA MINORU , TAKATA MASASUKE
Published: June 2006

The variation with water content of dc conductivity and Na diffusion coefficient for the Na2O · 4siO2 and Na2O · 2SiO2 glass systems was found to be similar to that of the Na2O.3SiO2 series reported earlier. The conductivity was estimated for the ternary system Na2O‐H2O‐SiO2 by combining the present results with the previous data on the Na2O · 3SiO2 system. When the conductivity of those glasses with a constant [Na2O] + [H2O] content was plotted against water content, a pronounced mixed “alkali” effect was demonstrated. The Haven ratio, calculated by comparison of the dc conductivity to the Na diffusion coefficient at 100°C for each of the three glass systems, was found to increase toward unity with increasing water content. This suggests that the addition of water reduces the number of sodium charge carriers. The subsequent increase in conductivity beyond the minimum with the introduction of larger amounts of water is, probably, due to an increase in the mobility of the Na+ ions.
Dynamic Compaction of Aluminum Nitride Powder: Hugoniot Measurement and Comparison with Static Behavior
Authors: GOURDIN W. H. , WEINLAND S. L.
Published: June 2006

A limited number of shock Hugoniot measurements were performed on two unsintered aluminum nitride powder compacts having initial densities of 1.30 and 1.53 g/cm3. Stresses achieved ranged from 0.25 to 1.8 GPa, corresponding to linear compaction rates of 0.2 to 0.6 km/s. Densification is incomplete behind the first shock wave, proceeding only to ∼70% of the solid density, regardless of the initial density. On reshock, however, significantly higher densities are achieved. Initial compaction of the powder to a relative density of 65% to 70% occurs readily at stresses below 0.25 GPa. For greater stresses, however, densification is slight. Comparisons with static compression data for the same powders suggest that this resistance to compaction is an effect of compaction rate.
Plastic Deformation in Alumina by Explosive Shock Loading
Authors: BEAUCHAMP E.K. , CARR M. J. , GRAHAM R.A.
Published: June 2006

Spherical alumina powder, composed of α‐Al2O3 and transitional alumina phases, was compacted by explosive shock loading with maximum pressures of 13 to 26 GPa and a maximum adiabatic temperature rise of ∼400°C. A final density >90% of theoretical was achieved. The powder densified primarily by plastic deformation, with only occasional particle fracture. Transmission electron microscopy showed dislocation densities of at least 1011 cm−2 in all phases and extensive twinning in transitional alumina phases.
Formation of ZnO Hemispheres from a Mixed‐Nitrate Glass Melt
Authors: Louër Daniel
Published: June 2006

From a KZn(NO3)3 glass melt it is possible to prepare, at 180°C, ZnO particles having a hemispherical morphology with an average diameter of 300 pm. Careful microscopic examinations and the behavior of the particles during annealing are presented. The addition of 1 wt% Co in the glass melt leads to the formation of ZnO spherules.
Transformation of Yttria‐Doped Tetragonal ZrO2 Poly crystals by Annealing under Controlled Humidity Conditions
Authors: Sato Tsugio , Ohtaki Shiro , Endo Tadashi , Shimada Masahiko
Published: June 2006

Phase changes on the surface resulting from low‐temperature annealing of yttria‐doped tetragonal ZrO2 polycrystals under controlled humidity conditions were investigated at 0.1 to 7350 Pa of water vapor pressure and 100° to 600°C for 1 to 50 h. The tetragonal‐to‐monoclinic phase transformation was greatly accelerated by increasing water vapor pressure; the transformation rate was first order with respect to the concentration of tetragonal ZrO2 on the surface of the sample.
Effect of Thickness on Direct Bonding of Silicon Nitride to Steel
Authors: Suganuma Katsuaki , Okamoto Taira , Koizumi Mitsue , Shimada Masahiko
Published: June 2006

The effects of specimen size, primarily the thickness of silicon nitride, on residual stress in a silicon nitride/steel joint were calculated using a finite‐element method and studied experimentally by tensile tests of isostatically hot‐pressed joints. The thicker joints had a low strength because of thermal expansion mismatch. When the silicon nitride was <0.2 mm thick, the strength of the joints reached 50 MPa.
Structure‐Property Relations in Lanthanide Borate Glasses
Authors: CHAKRABORTY INDRA N. , DAY DELBERT E. , LAPP JOSEF C. , SHELBY JAMES E.
Published: June 2006

Glass formation in the system Ln2O3‐B2O3 (Ln = Nd, Sm) was studied. Glasses could be formed in the range from 0 to ‐28 mol% rare‐earth oxide (Ln2O3), but liquid immiscibility in these systems limits the range of homogeneous glasses to 0 to 1.5 and 25 to 28 mol% Ln2O3. The infrared spectra indicate that the rare‐earth‐rich glasses are structurally similar to rare‐earth metaborates (LnB3O6) which contain (B3O6)‐ chains. The variation in density, transformation temperature, thermal expansion coefficient, and transformation‐range viscosity of these glasses with the size of the rare‐earth ion is discussed. Glasses near the metaborate composition have a transformation temperature of =700°C, which is high for binary borate glasses. Glasses could not be formed in the systems EU2O3‐, Gd2O3‐, HO2O3‐, and Er2O3‐B2O3, even by quenching at =1300°C/s. The sudden lack of glass formation in the system Ln2O3‐B2O3 with Ln3+ ions smaller than Sm3+ is explained on the basis of the size effect of the Ln3+ ion on the stability of (B3O6)‐ chains in these metaborates.
Differences in Surface Behavior of Alkali Ions in Li2O ·3SiO2 and Na2O · 3SiO2 Glasses
Authors: GAROFALINI S. H. , LEVINE S. M.
Published: June 2006

The molecular dynamics computer simulation technique was used to determine the short‐time dynamics behavior and resultant structures of ions at the surface of Li20·3SiO2 and Na2O‐3SiO2 glasses. Room temperature and elevated temperatures were used. Results are compared with similar studies of the K2O·3SiO2 glass surface and with recent experimental ion‐scattering‐spectroscopy data. The simulations indicate that a localized surface rearrangement occurs within picoseconds after formation of the free surface, creating a surface excess of alkali in the Na (and K) case, but not in the Li case. Elevated temperatures, even for brief times, enhance the observed surface excess of Na and K. The results correspond to those obtained from the ion‐scattering‐spectroscopy studies.
Subcutectic Densification and Second‐Phase Formation in Al2O3‐Cao
Authors: WU SHUN JACKSON , JONGHE LUTGARD C. DE , RAHAMAN MOHAMMED N.
Published: June 2006

The early and intermediate stages of densification of alumina containing calcia were examined at subeutectic temperatures. Up to 0.15 wt% calcia causes a decrease in the densification rate; from 0.15 to 0.7 wt% calcia, the densification rate increases initially but then decreases at longer times; more than 0.75 wt% calcia leads to a monotonically decreasing densification rate. The data for materials containing more than 0.15 wt% calcia may be interpreted as a competition between enhanced subeutectic densification and the presence of densification‐retarding second phases.
Photoelastic Effects in Phosphate Glasses
Authors: MATUSITA KAZUMASA , IHARA CHIKASHI , KOMATSU TAKAYUKI , YOKOTA RYOSUKE
Published: June 2006

The stress‐optical coefficients of RO‐Pz05 glasses (R = Mg, Ca, Sr, Ba, and Zn) were measured, and the photoelasticity mechanisms were analyzed based on the equation expressing the relation among the photoelastic constants, the elastic moduli, and the refractive index of glasses. No simple relation was found between the stress‐optical coefficient and the elastic modulus, indicating that the factor (p – q), where p and q are the Neumann strain‐optical coefficients, is important. The change of (p – q) with glass composition is governed mainly by changes in the effect of the atoms, rather than the lattice. The atomic effect increases with decreasing radius of the divalent cation, except for Zn2+. The ZnO‐containing glasses exhibit extraordinarily large atomic effects. The photo‐elasticity mechanism is discussed in relation to the nature of the chemical bonds.
Experimental Study of Porous Gel Sintering
Authors: SATOH S. , SUSA K. , MATSUYAMA I. , SUGANUMA T.
Published: June 2006

Formation and disappearance of closed pores in silica gel during sintering were experimentally detected using a light‐scattering technique. The disappearance of closed pores is strongly influenced by the atmosphere in which the gel is sintered.
Fabrication and Mechanical Properties of Lightweight Ceramics Produced by Sintering of Hollow Spheres
Authors: GREEN D.J.
Published: June 2006

Lightweight ceramics with densities in the range 8 to 24% of theoretical were fabricated by sintering hollow glass spheres. The densification behavior, which was complex, involved uniform shrinkage of the spheres, local densification, deformation of the spheres, and coarsening of the cells. A major flaw population was found to be relatively large areas which were devoid of spheres. There was a distinct difference in the mechanical behavior and fracture path for the low‐ and high‐density materials. The behavior of the high‐density materials appeared to agree well with existing micromechanical models in terms of Young's modulus, fracture toughness, and density. The fracture toughness of these cellular materials per unit weight is similar to that of bulk glass but is not translated into strength because of the relatively large flaw sizes in the final microstructure.
Surface ‐OH Profile from Reaction of a Heavy‐Metal Fluoride Glass with Atmospheric Water
Authors: TKJKIOAT DENIS , FONTENEAU GILLES , MOYNIHAN CORNELIUS T. , LUCAS JACQUES
Published: June 2006

The surface ‐OH profile in a 15BaF2‐28.3ZnF2‐28.3YbF2‐28.3ThF4 (mol%) glass resulting from reaction with atmospheric water for 22.5 h at 344°C was determined by monitoring the 2.9‐pm absorption band as material was removed from the surface by polishing. The ‐OH penetrated ‐10 pm into the surface. The‐OH concentration profile agreed with that predicted from a diffusional analysis, allowing determination of the surface ‐OH concentration; this corresponded to replacement of one of seven F− ions with OH−.
Microstructural Evolution in a ZrO2 Wt% Y2O3 Ceramic
Authors: CHAIM R. , RÜHLE M. , HEUER A. H.
Published: June 2006

Several unusual microstructural features, i.e., 90° tetragonal ZrO2 twins containing antiphase domain boundaries, tetragonal ZrO2 precipitates in a colony morphology, and precipitate‐free zones at the perimeter of cubic ZrO2 grains containing fine tetragonal ZrO2 precipitates, were observed in a single ZrO2‐12 wt% Y2O2 ceramic annealed at 1550°, 1400°, and 1250°C, respectively. The type of phase transformation responsible for each microstructural feature is described.
Thermodynamic Assessment of the System MnO‐NiO
Authors: BERGMAN BILL , ÅGREN JOHN
Published: June 2006

The thermodynamic properties of pure MnO and NiO were analyzed in terms of the Debye model and a model for the magnetic transitions. The classical formula R In (β+ 1) for the magnetic entropy was found to overestimate the effect of magnetic ordering in these systems. A previous interpretation of the data for NiO was corrected. Thermodynamic functions were derived for the solid and liquid states and are given as analytic expressions. A previous assessment of the Gibbs energy of the solid solution (Mn, Ni)O from activity data was modified on statistical grounds. The results indicate that there should be a miscibility gap below 41O°C. By estimating the Gibbs energy of the liquid phase, it was possible to calculate the complete phase diagram.
Phase Characterization of Partially Stabilized Zirconia by Raman Spectroscopy
Authors: PERRY C. H. , LIU D.‐W. , INGEL ROBERT P.
Published: June 2006

Raman spectroscopy was used to characterize phase transformations and transition temperatures in partially stabilized zirconia containing ≤20 wt% Y2O3. The completeness of the martensitic transition and its thermal hysteresis was followed in samples with ≤4 wt% Y2O3. Between 5 and 12 wt% the spectra indicate a tetragonal modification precipitated in a disordered cubic fluorite matrix. Above 15 wt% a “density of states” spectrum prevails that is characteristic of the fully stabilized disordered cubic phase.
Preparation and Properties of Nitrogen‐Doped Phosphate Glasses
Authors: REIDMEYER MARY R. , DAY DELBERT E.
Published: June 2006

Techniques for preparation and the properties of phosphorus oxynitride glasses produced from sodium metaphosphate and nitride compounds are reported. Properties reported include nitrogen content, dissolution rate in water, thermal expansion coefficient, softening point, glass transformation temperature, density, refractive index, microhardness, and infrared absorption.
Preparation of Submicrometer A12O3 Powder by Gas‐Phase Oxidation of Tris (acetylacetonato) aluminum (111)
Authors: KAMATA KIICHIRO , MOCHIZUKI TAKAO , MATSUMOTO SHIGEKI , YAMADA AKIFUMI , MIYOKAWA KIKUO
Published: June 2006

Fine A12O3 powder was prepared by the gas‐phase oxidation of aluminum acetyl‐acetonate. The reaction products were amorphous material at 600° and 800°C, γ‐Al2O3 at 1000° and 1200°C, and δ‐Al2O3 at 1400°C. The powders consisted of spherical particles from 10 to 80 nm in diameter; particle size increased with increasing reaction temperature and concentration of chelate in the gas.
Feasibility of a Composite of Sic Whiskers in an MoSi2 Matrix
Authors: GAC FRANK D. , PETROVIC JOHN J.
Published: June 2006

A composite consisting of 20 vol% Sic whiskers in a hot‐pressed MoSi2 matrix was investigated. The composite displayed an ∼100% increase inflexural strength and a 54% improvement in fracture toughness, compared to the values measured for the matrix material. The improvements are attributed to the change in the micro‐structure of the MoSi2 afforded by the presence of the whiskers.
Improvement in Fiber Testing of High‐Modulus Single‐Filament Materials
Authors: LI CHI‐TANG , LANGLEY NEAL R.
Published: June 2006

The standard procedure for determining the tensile strength and Young's modulus of single‐filament ceramic fibers (outlined in ASTM test method D‐3379‐75) was modified for accurate determination of Young's modulus, especially for fibers with larger diameters. An improved plotting method to determine the system compliance factor was developed; this method allows for variations in fiber diameter and produces more accurate Young's moduli.
Synthesis of (Ba, Pb) (Zr, Ti)03 Solid Solution Having No Compositional Fluctuations
Authors: KAKEGAWA KAZUYUKI , MOHRI JUN‐ICHI
Published: June 2006

A method was developed to determine compositional fluctuations in a (Ba, Pb) (Zr, Ti)O, solid solution which can exhibit two types of fluctuations. The solid solution prepared by an ordinary dry process undergoes large compositional fluctuations in both the Ba, Pb site and the Zr, Ti site. However, solid solutions prepared by solid‐solid reaction between coprecipitates of Pb2+ and Ba2+ and coprecipitates of Zr 4+ and Ti4+ showed no compositional fluctuations.
Thermodynamic Properties of Cerium Oxalate and Cerium Oxide
Authors: GALLAGHER SARAH ANN , DWORZAK WOLFGANG RUDOLPH
Published: June 2006

Differential scanning calorimetry and thermogravimetry were used to determine the thermodynamic properties of cerium oxalate. Hydrated cerium oxalate was found to contain 13 molecules of water and decomposed producing three thermal events corresponding to the loss of adsorbed water, water of hydration, and decomposition of anhydrous cerium oxalate to cerium oxide. Anhydrous cerium oxalate obeyed first‐order reaction kinetics where ‐In(1‐a)=kt. Reaction rates, heat capacities, and equations for the heat capacities are given.
Microstructure of Reaction‐Bonded Silicon Nitride Consolidated by Isostatic Hot‐Pressing
Authors: MIESKOWSKI DIANE M. , SANDERS WILLIAM A.
Published: June 2006

Reaction‐bonded Si3N4 specimens which had been isostatically hot‐pressed at 1850°, 1950°, and 2050°C were examined microstructurally and by chemical analyses. Previously reported data indicated an increase in the 1200°C bend strength of reaction‐bonded Si3N4 only after it was pressed at 2050°C. Observations from the present study indicate that this behavior results from the relative oxygen levels of the isostatically hot‐pressed specimens. Calculations show that an Si02 content of 52.2 vol% is required to realize an increase in the 1200°C strength.
Molecular Dynamic Simulation of Eu3+ ‐Doped Sodium Borate Glasses and Their Fluorescence Spectra
Authors: HIRAO KAZUYUKI , SOGA NAOHIRO
Published: June 2006

A molecular dynamic simulation was performed for sodium borate glasses containing a small amount of Eu2O3 to investigate the local structures of cations in glass. A new potential VB‐B in the form ‐A exp[‐C(r ‐ 0.239)2] was added to the regular modified Born‐Mayer‐Huggins‐type potentials, ΦB‐B, ΦB‐O, and ΦO‐O, to account for the directional tendency of the borate network structure. With this potential added, both the radial distribution of sodium borate glasses observed by small‐angle X‐ray diffraction and the change in coordination number of boron with sodium content obtained by NMR agreed well with the simulation. The average coordination number of Ed3+ ions in the simulated glasses varied from 7.5 to 8.6, depending on the composition of the host sodium borate glasses. The inhomogeneous line width of the 5D0‐7Fz emission peak also changed, depending on the sodium content, with a maximum at 18 mol% NazO content; this result agrees well with experimental data obtained from laser‐induced fluorescence spectra.
Superplastic Deformation in Fine‐Grained MgO 2Al2O3 Spinel
Authors: PANDA P. C. , RAJ R. , MORGAN P. E. D.
Published: June 2006

Fine‐grained polycrystals of MgO 2A12O3 spinel were deformed to large strains at strain rates ranging from 1O‐5 to 1O‐3 s‐1 and at temperatures from 1723 to 1885 K. These polycrystals were ductile at low strain rates and high temperatures; the ductility was especially remarkable at temperatures near the solvus. The mechanism of deformation, which was determined by measuring the change of flow stress with grain size, was dislocation creep, with the stress exponent in the power‐law creep equation having a value of 2.1 ± 0.4. Despite deformation of several hundred percent, the grain size remained equiaxed, and deformation led to the evolution of a grain size which depended only on the strain rate and temperature. The initial microstructure had an influence on whether the poly‐crystal would fracture or flow; a small initial grain size and a supersaturated solid solution were conducive to ductile flow. The ductility is attributed to dynamic recrystallization. It is proposed that the onset of fracture and the onset of dynamic recrystallization are competitive processes. Conditions which promote dynamic recrystallization also promote ductile flow.
Structural Dependence on Sintering Temperature of Lead Zirconate‐Titanate Solid Solutions
Authors: LUCUTA P. GR. , CONSTANTINESCU FL. , BARB D.
Published: June 2006

Pb(Zr0.525Ti0.475)O3 piezoceramics, both unmodified and doped with 2 wt% Bi2O3 or Nb2O5, were prepared by the usual techniques, using sintering temperatures from 900° to 1250°C. The microstructural data showed that the sintering temperature which produces minimum porosity is altered by the oxide additions. X‐ray diffraction demonstrated the coexistence of both ferroelectric phases. The lattice parameter measurements showed that the tetragonal and rhombohedra1 unit cells of the two ferroelectric phases depend on the sintering temperature.
Optical Absorption Spectra of Chlorine‐Associated Defect Centers in an Irradiated ZrF4‐Based Glass
Authors: Joseph Friebele E. , Tran Danh C.
Published: June 2006

The optical absorption spectra of an irradiated zirconium‐barium‐lanthanum aluminum‐ lithium fluoride glass prepared with 1 wt% BaC12 were resolved into Gaussian bands identified as the Vk, and VH centers, Zr3+, and two bands associated with Cl, i.e., FCl− at 4.78 eV and Cl−2 at 3.90 eV. These latter bands are more thermally stable than the VH and V, trapped hole centers, persisting to 450 and 550 K, respectively.
Monoclinic Crystal Structures of ZrO2 and HfO2 Refined from X‐ray Powder Diffraction Data
Authors: Hann Raiford E. , Suitch Paul R. , Pentecost Joseph L.
Published: June 2006

The crystal structures of ZrO2 and HfO2 (P21/c) were refined in detail from X‐ray powder diffraction data. The precision obtained for the atom positions for both compounds is comparable to that of previous single‐crystal work.