bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric Properties of Ceramics in the System (Sr0.50Pb0.25Ca0.25)TiO3‐Bi2O3·3TiO2 and Their Applications in a High‐Voltage Capacitor
Authors: NISHIGAKI SUSUMU , MURANO KANJI , OHKOSHI AKIO
Published: June 2006

The dielectric behavior of (1‐x)(Sr0.5Pb0.25Ca0.25) TiO3‐x(Bi2O3·3TiO2) was studied using x=O to 8.25 mol%. Around the point at which x equals 1.56 mol%, the following phenomena were observed: (1) At −;22°C, the weak field permittivity increased substantially with a dc bias field, becoming more than twice the zero bias value at a field of 3 kV/mm; (2) the permittivity peak shifted markedly toward a high temperature under a dc bias field; (3) relaxation behavior was evident; and (4) there are large hysteresis loops at low temperatures and double hysteresis loops, which seem to be related to a field‐enforced ferroelectric phase, in a wide temperature range. We used dielectrics with an optimized composition of x=4.30 mol% in a small, highly reliable, 15‐kV high‐voltage ceramic capacitor.
Preparation and Properties of Quenched Li2O‐BaO‐Nb2O5 Glasses
Authors: TATSUMISAGO MASAHIRO , HAMADA AKIRA , MINAMI TSUTOMU , TANAKA MASAMI
Published: June 2006

Glasses were prepared in the wide variety of compositions in the system Li2O‐BaO‐Nb2O5, which contains no “glass‐former,” by the twin‐roller quenching technique. The crystallization temperature ranges from 500° to 700°C and increases as Li2O is replaced by BaO. The dielectric constant increases steeply with temperature, reaching an anomalously large value (104) in glasses which contain a large amount of Li2O. Such a temperature dependence of dielectric constant is very similar to that of conductivity in each glass, indicating that the dielectric behavior is caused by polarization due to the ionic motion in glass. The conductivity at 500 K ranges from 10−13 to 10−5Ω−1·cm−1 and the activation energy for conduction from 120 to 40 kJ/mol. The concentration of Li+ ions mainly controls the conductivity and the addition of Ba2+ ions slightly lowers it.
Effect of Thermal Gradients on Ionic Defects in Wustite
Authors: HODGE J. D. , BOWEN H. K.
Published: June 2006

The thermal gradient response of ionic defects in wustite was studied using two methods. The first involved measuring the decay of the thermoelectric voltage of a sample with time in a thermal gradient. The second involved measuring concentration gradients in samples which had been annealed in a thermal gradient for an extended amount of time. Both types of experiments gave results that could be predicted by assuming that the behavior of ionic defects in a thermal gradient is determined primarily by the local equilibrium of the sample with the gas phase.
Characterization and Crystallization of Y‐Si‐Al‐O‐N Glass
Authors: Thomas G. , Ahn C. , Weiss J.
Published: June 2006

Glasses were prepared from sintered powders ofSi3N4, Al2O3, Y2O3 AlN, andSiO2 to study their crystallization on subsequent heat treatment. Appreciable crystallization was efected only after the glasses were doped with up to 5 wt% ZrO2. Electron microscopy and microanalysis showed that the crystalline phase was Y2O3·2SiO2 without detectable Zr. The sofening temperature is in the range 850° to 1020°C. In‐situ heating in a high‐voltage electron microscope at ∼12OO°C produced renucleation and growth of the crystalline phase; at higher temperatures, however, the glass phase volatilized.
High‐Strength Ca(PO3)2 Glass‐Ceramics Prepared by Unidirectional Crystallization
Authors: Abe Y. , Hosoe M. , Kasuga T. , Ishikawa H. , Shinkai N. , Suzuki Y. , Nakayama J.
Published: June 2006

New CaO‐P2P5 glass ceramics were prepared by crystallizing glass rods or plates unidirectionally in a temperature‐gradient furnace. The unidirectionally crystallized glass showed extremely high bending strength (∼500 to 600 MN/m2) even when subjected to a severe abrasion treatment with Sic paper. Scanning electron microscopy of fracture surjaces revealed a typical fiber‐reinforced‐composite structure. Crystalline phases and crystallographic directions were checked by X‐ray diflraction. The fracture mechanism is discussed in terms of microstructure.
Influence of a Tangential Force on the Fracture of Two Contacting Elastic Bodies
Authors: CHIANG SHU‐SHENG , EVANS ANTHONY G.
Published: June 2006

The problem of fracture initiation at two elastically contacting structural components, subject to applied normal and tangential forces, was analyzed. The fracture initiation load was predicted to depend sensitively on the magnitude of the applied tangential force and the interfacial friction coefficient, and to exhibit important dependencies on the fracture toughness, elastic modulus, and curvature of the contacting bodies. Experimental results obtained on glass and Si3N4 conform with the trends predicted by the analysis.
Formation of Ultrafine Tetragonal ZrO2 Powder Under Hydrothermal Conditions
Authors: TANI EIJI , YOSHIMURA MASAHIRO , SŌMIYA SHIGEYUKI
Published: June 2006

Ultrafine tetragonal ZrO2 powder was prepared by hydrothermal treatment at 100 MPa of amorphous hydrous zirconia with distilled water and LiCl and KBr solutions. The resulting powder consisted of well‐crystallized particles; at 200°C, the particle size was 16 nm and at 500°C, 30 nm. Under hydrothermal conditions tetragonal ZrO2 appears to crystallize topotactically on nuclei in the amorphous hydrous zirconia.
Microstructure and Grain‐Boundary Composition of Hot‐Pressed Silicon Nitride With Yttria and Alumina
Authors: AHN CHANNING C. , THOMAS GARETH
Published: June 2006

The microstructure of two hot‐pressed silicon nitrides containing Y2O3 and Al2O3 was examined by electron microscopy, electron diffraction, and quantitative, energy‐dispersive X‐ray microanalysis. A crystalline second phase was identified in the material with additives of 5 wt% Y2O3+2 wt% Al2O3, as a solid solution of nitrogen mellilite and alumina. An amorphous third phase as narrow as 2 nm is discerned at all grain boundaries of this material by high‐resolution dark‐field and lattice imaging. The second phase in a material with additives of S wt% Y2O3+5 wt% Al2O3 was found to be amorphous. Some of the additional alumina additive appears in solid solution with silicon nitride. In situ hot‐stage experiments in a high‐voltage electron microscope show that the amorphous phase volatilizes above 1200°C, leaving a skeleton of Si3N4 grains linked by the mellilite crystals at triple points. The results show that intergranular glassy phases cannot be eliminated by the Y2O3/Al2O3 fluxing.
Subsolidus Phase Equilibria and Ordering in the System ZrO2‐Y2O3
Authors: PASCUAL CARMEN , DURÁN PEDRO
Published: June 2006

The subsolidus phase relations in the entire system ZrO2‐Y2O3 were established using DTA, expansion measurements, and room‐ and high‐temperature X‐ray diffraction. Three eutectoid reactions were found in the system: (a) tetragonal zirconia solid solution→monoclinic zirconia solid solution+cubic zirconia solid solution at 4.5 mol% Y2O3 and ∼490°C, (b) cubic zirconia solid solutiow→δ‐phase Y4Zr3O12+hexagonalphase Y6ZrO11 at 45 mol% Y2O3 and ∼1325°±25°C, and (c) yttria C‐type solid solution→wcubic zirconia solid solution+ hexagonal phase Y6ZrO11 at ∼72 mol% Y2O3 and 1650°±50°C. Two ordered phases were also found in the system, one at 40 mol% Y2O3 with ideal formula Y4Zr3O12, and another, a new hexagonal phase, at 75 mol% Y2O3 with formula Y6ZrO11. They decompose at 1375° and >1750°C into cubic zirconia solid solution and yttria C‐type solid solution, respectively. The extent of the cubic zirconia and yttria C‐type solid solution fields was also redetermined. By incorporating the known tetragonal‐cubic zirconia transition temperature and the liquidus temperatures in the system, a new tentative phase diagram is given for the system ZrO2‐Y2O3.
Rhombohedral Twinning in Alumina
Authors: SCOTT WILLIAM D. , ORR K. K.
Published: June 2006

Alumina single crystals were deformed in compression along the c axes at T= 625 to 1373 K. Large‐scale deformation by rhombohedral twinning was observed at a constant resolved shear stress of only 12.6 MPa between ∼900 and 1373 K. Below 900 K, the twinning stress for specimens with ground surfaces rose rapidly to 227 MPa at 625 K. A model for twin growth in the absence of dislocation slip is proposed.
Thermal Expansion of Substituted Copper Aluminosilicate Glasses
Authors: MATUSITA KAZUMASA , SAKKA SUMIO , SHOUJI TOMOSHI
Published: June 2006

The effects of various components on the thermal expansion coefficient of low‐expansion Cu2O‐Al2O3‐SiO2 glasses were examined. When a component of glass was substituted by another oxide, the expansion coefficient always increased, except for substitution of Al2O3 by B2O3. This result indicates that the essential components to maintain the low expansivity are Cu2O, such trivalent oxides as Al2O3 and B2O3, and tetravalent oxide SiO2. Glasses of the systems Cu2O‐Al2O3‐B2O3, Cu2O‐Al2O3‐GeO2, and Cu2O‐Al2O3‐P2O5, which were derived by replacing SiO2 by other network‐forming oxides, showed fairly low expansion coefficients compared with other conventional borate, germanate, and phosphate glasses. It was also found that the valence state of copper ions is important for the thermal expansion characteristics of these glasses; Cu+ ions contribute to the low expansion coefficient.
A Biaxial‐Flexure Test for Evaluating Ceramic Strengths
Authors: SHETTY D. K. , ROSENFIELD A. R. , DUCKWORTH W. H. , HELD P. R.
Published: June 2006

An improved test fixture for biaxial‐tension strength testing of ceramics featuring uniform pressure loading of disks was developed and qualified. Biaxial data were obtained for an alumina ceramic, along with comparable uniaxial data from three‐ and four‐point flexure tests. Weibull statistics provided a good description of the size effect on data from the two uniaxial tests, but underestimated the effect of stress biaxiality. The biaxial strengthening observed in the alumina ceramic is consistent with that observed previously in a glass‐ceramic.
Electrical Conduction in Co1‐χMgχO
Authors: KOUMOTO KUNIHITO , YAMAYOSHI KEIKO , YANAGIDA HIROAKI
Published: June 2006

Electrical conductivity and thermoelectric power were measured on Co1‐χMgχO (0.16χ 0.87) at 900° to 1200°C. Electrical conductivity σ decreased and the activation energy increased with increasing MgO content. Seebeck coefficient α appeared to be positive for all χ. The difference in temperature dependence of σ and α was 0.2 to 0.5 eV and the hole mobility decreased with increasing MgO content. The results were interpreted as showing that electron holes were localized to cation clusters and their thermally activated hopping conduction was operative in the solid solution. The dominant lattice defect changed from singly to doubly ionized cobalt vacancy with increasing MgO content.
Ionic Transference Numbers and Electrical Conduction in MgAl2O4 Spinel
Authors: SONDER EDWARD
Published: June 2006

Ionic transference numbers were obtained for T=1000 to 1700 K and for oxygen pressures 105 to 10−11 Pa by measuring potentials produced across samples having different oxygen partial pressures at the two faces. Alternating and direct current conductivities were also measured for the same samples over the same range of temperature and pressure. The results show that conduction in MgAl2O4 is almost purely ionic and that the conductivity is not greatly influenced by either ambient oxygen pressure or iron impurity up to 0.1%. It is proposed that the current carriers are cation vacancies that are present as a result of cation nonstoichiometry.
Viscoelastic Analysis of Thermal Stresses in a Composite Sphere
Authors: SCHERER GEORGE W.
Published: June 2006

Viscoelastic analyses of thermal stresses are presented for composite spheres in which the viscous phase constitutes either the core or the cladding. These results should offer a better approximation to the stresses caused by spherical inclusions than the isolated sphere solution. The viscoelastic solution provides a means of finding the appropriate setting temperature for the composite, and its dependence on the volume fraction of the elastic material. The setting temperature of an elastic core composite is also shown to be predictable from that for a sandwich seal of the same materials. A “fluid core” analysis is shown to provide a good approximation when the elastic phase constitutes the cladding. This type of seal is sensitive to the dilatational relaxation behavior of the glass.
NMR Study of Adsorbate Self‐Diffusion in Porous Glasses
Authors: KÁRGER JÖRG , LENZNER JÖRG , PFEIFER HARRY , SCHWABE HARTMUT , HEYER WOLFGANG , JANOWSKI FRANK , WOLF FRIEDRICH , ŽDANOV SERGEJ PETROVIČ
Published: June 2006

The NMR pulsed field gradient technique was used to study molecular transport in porous glasses. The adsorbent materials were produced by leaching phase‐separated sodium‐boron‐silica glasses of different composition, then heat‐treating. The pore diameters of the glass samples produced were within the interval 0.8 to 50 nm. Water, methanol, dodecane, and do‐decene were used as adsorbates. The coefficients of adsorbate self‐diffusion were found to decrease with decreasing pore diameter. In comparison with the neat liquids, a reduction in the adsorbate mobility (up to two orders of magnitude) was observed. For the larger pores, that decrease may be attributed to the tortuosity of the adsorbent, whereas the low diffusivities in the porous glasses with small pores are a consequence of the stabilizing effect of the rigid adsorbent framework.
Effect of Microstructure on the Properties of TiB2 Ceramics
Authors: Ferber Matt K. , Becher Paul F. , Finch Cabell B.
Published: June 2006

Samples of a TiB2 ceramic containing 0 to 10 wt% Ni were fabricated by hot‐pressing. Several properties, including fracture strength, indentation fracture toughness, and thermal expansion (between 25° and 1000°C) were measured. Resulting data were correlated with sample microstructure and composition.
Fracture Toughness Predictions for Crack Bowing in Brittle Particulate Composites
Authors: Green David J.
Published: June 2006

The bowing of cracks between obstacles has been proposed as a mechanism for increasing the .fracture toughness of brittle materials. An analytical expression is presented based on previous theoretical studies that can be used to predict the increase in fracture toughness. The approach incorporates the effect of obstacle failure and the assumptions needed to compare the predictions with experimental data.
Microstructural Characterization of Graded‐Index Antireflective Films
Authors: Danforth Stephen C. , Haggerty John S.
Published: June 2006

The miscrostructure of graded‐index antirefection (GIAR) films was characterized using transmission and scanning electron microscopy, small‐angle X‐ray scattering, and replication. Transmission electron microscopy and X‐ray scattering results agree for the entire coarsening history of the phase‐separated substrate borosilicate glass. The complexity of the replication process and the metallization used for scanning electron microscopy caused the effective resolution limits for GIAR films to be much larger than the inherent resolution limits for each instrumentation.
Formation of β‐Si3N4 Coatings by Chemical Vapor Deposition
Authors: Oda Kiichi , Yoshio Tetsuo , O‐Oka Kazuo
Published: June 2006

BetaSi3N4 coatings were obtained by chemical vapor deposition in a fused‐silica reaction tube by outside heating of the system SiCl4‐NH3‐N2 at a deposition temperature (reaction tube temperature) of 1300°C, whereas α‐ and α+β‐phase coatings were obtained at depositon temperatures of 1150° and 1250°C, respecively. Formation of β‐phase coatings at relatively low temperatures is explained in terms of the effect of a catalytic impurity, SiO vapor from the reaction tube. The X‐ray diffraction patterns and sulface morphologies of the coatings were studied.
Crack Branching in Ceramic Disks Subjected to Biaxial Flexure
Authors: Shetty D. K. , Rosenfield A. R. , Duckworth W. H.
Published: June 2006

Fracture stresses in soda‐lime glass, a glass‐ceramic, and an alumina ceramic tested in biaxial flexure correlated with the crack lengths prior to branching. The resultant branching constant for the glass agreed closely with the mirror‐mist boundary constant, and evidence indicated agreement between the branching constants and the inner‐mirror boundary constants for the polycrystalline materials. The ratio of the branching constant to the critical stress intensity factor was much smaller for the polycrystalline materials than for the glass. The crack‐branching measurements also indicated the presence of a compressive residual stress as Sociated with the ground sufaces of the specimens.
A Liquid Silazane Precursor To Silicon Nitride
Authors: Seyferth Dietmar , Wiseman Gary H. , Prud'homme Christian
Published: June 2006

The reaction of dichlorosilane, H2SiCl2, with gaseous NH3 in dichloromethane or diethyl ether solution results in the formation of a silazane oil containing silicon, hydrogen, and nitrogen in good yield. This ammonolysis product can be pyrolyzed in an N2 atmosphere (temperature to 1150°C) to give α‐Si3N4 in ∼70% yield. The ceramic product formed has a relatively porous, fine‐grained microstructure with some cracks and blisters.
Infrared Spectra of Rapidly Quenched Glasses in the Systems Li2O‐RO‐Nb2O5 (R=Ba, Ca, Mg)
Authors: TATSUMISAGO MASAHIRO , HAMADA AKIRA , MINAMI TSUTOMU , TANAKA MASAMI
Published: June 2006

Twin‐roller quenching produced wide ranges of glass formation in the systems Li2O‐RO‐Nb2O5 (R=Ba,Ca,Mg). The glass‐forming ability is improved with an increase in the ionic radius of R2+ ions. The crystallization temperature is increased as Li2O is replaced by RO or the ionic radius of R2+ ions is increased. Infrared spectra revealed that the glass LiNbO3 (=50Li2O‐0Nb2O5) was composed of six‐coordinated NbO6 octahedra, which were joined together by corner‐sharing only. In the Li2O‐RO‐Nb2O5 glasses there exist edge‐shared as well as corner‐shared NbO6 octahedra. The edge‐shared NbO6 octahedra in the glasses are increased with an increase in the content of RO or Nb2O5, and also with an increase in the ionic radius of R2+ ions.
Effect of Heat Treatment on the Na+ Resistivity of Vitreous Silica
Authors: PAPADOPOULOS KIM , MATTOX DOUGLAS M. , MEEK THOMAS T.
Published: June 2006

The dc resistivity of fused quartz with respect to Na+ ions was measured at temperatures up to 750°C, using β‐alumina as the sodium source. Heat treatment in air at 1100°C gave minima in resistivity at times which depended on the choice of either a high‐OH or a low‐OH glass. The initial fall in resistivity is explained by the stabilization of the glass to a more open structure and the later increase is attributed to a blocking effect of “permanent” hydroxyl groups, which slowly enter the glass as atmospheric water.
Controlled Flaws in Ceramics: A Comparison of Knoop and Vickers Indentation
Authors: MARSHALL DAVID B.
Published: June 2006

Application of indentation fracture analysis to Knoop and Vickers indentation is examined, with particular emphasis on determining the limitations of the point force representation for the residual stress field. Deviation from the point force approximation is insignificant for crack‐size/plastic‐zone‐size ratios 1.3. The Vickers deformation/fracture configuration in brittle materials invariably conforms to this requirement, whereas the Knoop configuration does not (except at very high indentation loads). However, stable crack growth during a failure test extends the crack sufficiently that the strength degradation for both types of indentation is well described by the point force approximation.
Elevation of Liquidus Temperature in a Gel‐Derived Na2O‐SiO2 Glass
Authors: WEINBERG MICHAEL C. , NEILSON GEORGE F.
Published: June 2006

The liquidus temperatures of a 19 wt% soda‐silica glass prepared by gel and conventional techniques were determined. X‐ray diffraction measurements of the glasses which were heat‐treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel‐derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel‐derived glass is elevated.
Hydrothermal Oxidation of Hf Metal Chips in the Preparation of Monoclinic HfO2 Powders
Authors: TORAYA HIDEO , YOSHIMURA MASAHIRO , SŌMIYA SHIGEYUKI
Published: June 2006

Fine monoclinic HfO2 powders were prepared from Hf metal chips by reaction with high‐temperature high‐pressure water. Dependence of the reaction on temperature‐pressure‐time was examined in both closed and open systems. Hydrothermal oxidation of Hf proceeded through three stages: the surface oxidation of Hf metal chips with H2O, the reaction of the Hf with released H2 to form hydrides, and the succeeding oxidation of the hydrides with H2O to form HfO2. Most of the fine HfO2 powders were, however, considered to be formed by the latter two reactions after the cracking and pulverizing of metal chips associated with hydriding. The difference in the reaction rates between the closed and open systems was explained by taking into account the fugacity relations of H2 and H2O in the respective systems.
High‐Temperature Environmental Strength Degradation of a Hot‐Pressed Silicon Nitride: An Experimental Test
Authors: CLARKE D.R.
Published: June 2006

High‐temperature environmental strength degradation of hot‐pressed silicon nitride ceramics is postulated to occur as a consequence of the properties of the noncrystalline inter‐granular phase being altered by cation diffusion from the environment. The model proposed is tested by comparing the strength before and after prolonged high‐temperature exposures to a calcium‐rich magnesium silicate. Two high‐temperature degradation regimes are identified, one in which the intergranular phase alone is affected, and the other, at still higher temperatures, where actual corrosion of the silicon nitride grains occurs.
Densification of Calcia‐Stabilized Zirconia with Borates
Authors: Buchanan Relva C. , Sircar Anup
Published: June 2006

Densification studies of submicrometer ZrO2 powders stabilized with 6.5 wt% CaO (CSZ) showed borate additions (1 to 10 wt%) to be effective sintering aids. Estimated densities >99% of theoretical were obtained on sintering at 1200°Cfor 4 h with 2 wt% B2O3 or 5 wt% CaO·2B2O3 additions to the CSZ powders. Average grain sizes obtained were typically <1 μm. Partial development of a monoclinic ZrO2 phase was observed in the sintered samples. The amount of this phase varied from ∼7 to 75 wt% and was approximately linearly dependent on the additive concentration. The effect was most marked for the B2O3 additions. Development of the monoclinic phase was attributed to progressive leaching of Ca from the CSZ phase by B2O3, in effect partially destabilizing the ZrO2.
Comparison of KIc Values for Al2O3‐ZrO2 Composites Obtained from Notched‐Beam and Indentation Strength Techniques
Authors: Swain Michael V. , Classen Nils
Published: June 2006

Values of KIcfor hot‐pressed AL2O3‐ZrO2 composites were measured using notched‐beam and indentation strength techniques. The results are compared with K factors at the mirror/mist boundary and at crack branching. It was found that the indentation strength technique provides a more consistent estimation of KIc, than the notched‐beam technique.
Static Fatigue of Preoxidized Hot‐Pressed Silicon Nitride
Authors: Quinn George D. , Swank Lewis
Published: June 2006

Hot‐pressed Si3N4 samples were preoxidized and tested in stress rupture. The lifetime of preoxidized samples was compared to samples that were not pretreated; for the test conditions chosen, lifetime was shorter for the preoxidized samples.
Infrared Study of Soda‐Lime Glass During Hydration and Dehydration
Authors: OLBERT BLAIN H. , DOREMUS ROBERT H.
Published: June 2006

Infrared spectra of two soda‐lime silicate glasses were measured after different times of hydration and dehydration. The height of OH and molecular water bands increased proportionally to the square root of time during hydration. The amount of dehydration with time was fit with a diffusion model; the diffusing species was probably molecular water. The rate of dehydration of the two laboratory glasses was many orders of magnitude faster than the rate for a commercial soda‐lime glass, consistent with the presence of a transformed layer on the surface of the hydrated laboratory glasses.
Kinetics of the β″‐to‐β Transformation in the System Na2O‐A12O3
Authors: HODGE JAMES D.
Published: June 2006

Mixtures of α‐A12O3 and NaAlO2 corresponding to the eutectic composition 65 mot % A12O 3 were heated in sealed platinum crucibles above the eutectic temperature (measured to be 1572°C in this study). Once melting was complete, the liquid was quenched and the resultant solid examined by X‐ray diffraction. Sodium aluminate, beta alumina, and beta″ alumina were detected in all cases. However, the relative amounts of beta and beta″ present were a function of the cooling rate, with the amount of beta″ increasing with a decreasing cooling rate. Subsequent annealing (in platinum envelopes) of the solidified eutectic at 1400° and 1530°C showed that the amount of beta″ present decreased with increasing annealing time. Based on this observation, it is apparent that, in the temperature range studied, beta″‐is metastable. Analysis of the time‐transformation data shows that the reaction kinetics are consistent with the diffusion‐controlled growth of the beta phase at the expense of the beta″‐phase.
Effect of Iron on Waste‐Glass Leaching
Authors: McVAY GARY L. , BUCKWALTER CHARLES Q.
Published: June 2006

The interactive effects between ductile iron and PNL 76–68 borosilicate glass were investigated as a function of time in 90°C static deionized, tuff, and basalt groundwaters. A syn‐ergistic effect occurs between the two materials, i. e. iron enhances glass dissolution and glass enhances iron corrosion. An iron silicate precipitate forms, part of which is colloidal in nature. This precipitate effectively removes many of the elements from solution and therefore inhibits the saturation effects which normally cause decreases in elemental removal rates. Thus, the effects of initial solution composition on the glass leach rates are significantly reduced and the relatively high early leach rates normally observed in deionized water are maintained for longer times due to the suppression of saturation effects. This results in more total elemental removal from the glass in all of the groundwaters evaluated. The precipitate and its colloidal form require further characterization.
Impurity Alkali Diffusion in Sodium‐Cesium Silicate Glasses
Authors: JAIN H. , PETERSON N. L.
Published: June 2006

The tracer diffusion coefficient of 86Rh was measured as a function of Cs/Na ratio in (Na, CS)2O:3SiO2 glasses. A comparison of the compositional dependence of this impurity alkali diffusion with the self‐diffusion coefficients of 22Na and 137Cs suggests that the alkali‐ion pair concept in the weak‐electrolyte model is not sufficient to explain the mixed‐alkali effect.
Fracture‐Surface Energy and Fracture Toughness of (U,Pu)C and (U,Pu(C,O)
Authors: MATZKE HANSJOACHIM , MEYRITZ VOLKER , ROUTBORT JULES L.
Published: June 2006

The fracture surface energy, γf, and the fracture toughness, K1c, were measured for the advanced fast‐breeder reactor fuels (U0.80Pu0.20)C and (U0.82Pu0.18) C0.9O0.1, using the method of Hertzian indentation with steel indentors. Elastic behavior was observed with transgranular cracks yielding K1c, values of ∼ 1.5 MN·m−3/2. The surface energy of the oxicarbide was smaller than that of the carbide. Annealing of the (U,Pu) (C,O) led to a completely different behavior. Permanent “quasi‐plastic” deformation was observed, in addition to Hertzian ring cracks, due to pronounced grain‐boundary weakening and grain separation. The plausible cause, i. e. precipitation of He formed by decaying Pu into grain‐boundary bubbles, indicates that the in‐pile behavior of a nuclear fuel after some burn‐up does not necessarily correspond to the behavior observed in laboratory experiments, even in the absence of restructuring due to thermal gradients that exist during operation.
Role of Water Vapor in Crystallite Growth and Tetragonal‐Monoclinic Phase Transformation of ZrO2
Authors: MURASE YOSHIO , KATO ETSURO
Published: June 2006

The role of water vapor in crystallite growth and the tetragonal‐to‐monoclinic phase transformation of ZrO2 was studied using three specially prepared samples: an ultrafine powder of monoclinic ZrO2 obtained by hydrolysis of ZrOCI2, an aggregated powder of tetragonal ZrO2 obtained by thermal decomposition of Zr(OH)4 under reduced pressure, and an ultrafine powder of tetragonal ZrO2 obtained by thermal decomposition of zirconyl acetate dispersed in caramel. The samples were heat‐treated up to 1000°C in dry and wet atmospheres saturated with water vapor at 90°C. It was found that water vapor markedly accelerated crystallite growth for both monoclinic and tetragonal ZrO2 and facilitated the tetragonal‐to‐monoclinic phase transformation. Water vapor increases surface diffusion and thus enhances crystallite growth and decreases surface energy, which leads to stabilization of the tetragonal phase.
Behavior of Pores in the Sintering of Acicular Fe2O3 Powder
Authors: YAMAGUCHI TAKASHI , KOSHA HIDEAKI
Published: June 2006

The sintering of acicular Fe2O3 powder was studied by isothermal dilatometry, hysteresis Hg porosimetry, and SEM of powder compacts using a resin‐impregnating technique, and compared with an ordinary equiaxed powder. It is shown that the pores in the acicular powder compacts remain connected until a later stage of sintering than those in the spherical powder, and that the observed rapid initial densification, along with preferential shrinkage in the parallel‐to‐pressing direction, can be interpreted in terms of particle rearrangement.
Synthesis and Characterization of a High‐Purity AlN Powder
Authors: HUSEBY IRVIN C.
Published: June 2006

High‐purity AIN powder was synthesized by preparing high‐purity (NH4)3 AIF6, decomposing the (NH4)3 AIF6 to AIF3, and reacting the AIF, at 800° to 1000°C with high‐purity NH3. AIN powders could be synthesized with a cation purity of 99.99% and an oxygen content <0.2 wt%. The specific surface area depended on the process conditions and varied from 0.2 to 2.6 m2/g. The thermodynamics of the process are evaluated and the influence of various process parameters on the resulting powder characteristics are described.
Heat‐Resistant Nonsilicate Porous Glasslike Material
Authors: RES MILOSLAV A. , HART S. , WHITE R. W.
Published: June 2006

Substitution of the end‐member oxides in the ternary sodium borosilicate system was studied. Replacing SO2 with a combination of beat‐resistant oxides Ce, Hf, Th, and Zr (with or without La2O3 and/or Y2O3) was found to produce glasses (droplet like phases present), which after heat treatment decomposed into two immiscible microphases (coarsening process) of which one is water‐soluble. The structure of the leached materials or the materials sintered after leaching (CeO2‐HfO2‐La2O3‐ThO2‐Y2O3‐ZrO2), (CeO2‐HfO2‐La2O3‐ThO2‐ZrO3), (CeO2‐HfO2‐ThO2‐YZO3‐ZrO2), and (CeO2‐HfO2‐ThO2‐ZrO2) is predominantly glasslike. Some Na2O‐B2O3 may be expected to remain unleached in the pores, as has been observed for silica‐based materials. However, no evidence for this was found during X‐ray diffraction analysis and therefore any such presence if crystalline must be below 1%. The new glasslike materials have a higher sintering temperature (1520°C) than porous silica glass (900° to 1200°C). The specific surface area of the leached glasslike materials is 93.7 to 295.8 m2/g and an average pore radius of 0.4 to 7.3 nm was calculated, A favorable alkali resistance of 5.12 × 10−3 to 1.36 × 10−2 mg/dm2 as well as a water resistance of 5.9 to 13.8 Na2O in mg/g was measured.
Static Fatigue of Silica in Hermetic Environments
Authors: Wysocki J. A.
Published: June 2006

Static fatigue tests on metal‐coated silica fibers have shown subcritical crack growth with crack velocities ranging from ∼10−14 to 10−17 m.s−1. To induce subcritical crack growth, however, it is necessary that the test be performed at stress intensities, KI, of >0.8 KIC. Metal‐coated fibers provide a unique medium for studying static fatigue at these high stress levels because the metal coating protects the fiber from the external environment. Crack growth,for these tests demonstrates the sensitivity of crack velocity to OH− concentrations at the crack site.
Optical Absorption and Oxidation States of Uranium in Alkali Aluminoborate Glasses
Authors: Morsi Morsi M. , El‐Konsol Salah , Adawi Mohamed A.
Published: June 2006

The optical absorption spectra of 22R2O.13Al2O3.65B2O3 (mol%) glasses contain ing uranium indicate the presence of U6+, U5+, and U4+. The presence of U6+ in the uranyl group is favored as alkali ion (R) is replaced in the direction Li<Na<K. Addition of 0.252 g Ce increases this species from ∼36% to ∼57% of the total U. The residual uranium occurs mainly as U6+ coordinated diflerently from that in uranyl groups (possibly 4‐coordinated). A suggestion for making use of such findings in estimating the uranium content of a sample is given.
Strength of Proof‐Tested Optical Fibers
Authors: Sakaguchi Shigeki , Nakahara Motohiro
Published: June 2006

Minimum strengths of proof‐tested optical fibers were investigated on the basis of the fracture mechanics concept. To confirm truncation of the minimum strength by the proof test, tensile tests were performed for long proofed fibers over a total length of 150 km. The results confirm that the proof test is useful in guaranteeing the minimum strength.
Characterization of Flux‐Grown Ca(WO4)x(MoO4)1–x Crystals
Authors: ARORA S. K. , GODBOLE R. S. , RAO G. S. TRIVIKRAMA
Published: June 2006

Crystals of Ca(WO4)x(MoO4)1–x, in the range x=0.072 to 0.86 were successfully grown by the flux technique. Neither the densities of the mixed crystals nor the cell parameters vary linearly. The dislocation density of the mixed crystals, determined by the etching technique, is greater than that of the end partners. The variation in microhardness of the mixed configurations is found to be linear and has no correlation with their dislocation content.
Melt Processing and Properties of Barium‐Sialon Glasses
Authors: TREDWAY WILLIAM K. , RISBUD SUBHASH H.
Published: June 2006

Bulk oxynitride glasses in the system Ba‐Sialon were prepared by cooling homogenized melts from ∼1740°C at ∼50°C/min. The microchemistry, microstructure, and properties of these materials were studied by DTA, dilatometry, electron microscopy, and energy dispersive X‐ray analysis. Up to ∼7 at.% nitrogen was retained in the glasses by the conventional glass‐processing techniques used. Microscopically homogeneous glasses were obtained despite macroscopic segregation of millimeter‐sized metallic spheres consisting of Si and Fe. Incorporation of nitrogen in the glass network led to decreasing thermal expansion coefficients, higher glass‐transition temperatures, and greater values of indentation hardness with increasing nitrogen content.
Toughening by Monoclinic Zirconia
Authors: RUF H. , EVANS ANTHONY G.
Published: June 2006

The toughening induced by monoclinic ZrO2 in the absence of microcracking was investigated, using ZnO as the host material. Toughness levels Kc in excess of the host toughness KcM were achieved, attaining a peak toughness Kc/KcM∼1.7, at monoclinic ZrO2 volume concentrations 0.2. This toughening is attributed to crack/particle interactions, associated with the deflection and bowing of the crack by the residual strain field around the monoclinic ZrO2 particles.
Liquid Immiscibility in the Systems X2O‐MO‐B2O3‐SiO2 (X=Na, K; M=Mg, Ca, Ba) and Na2O‐MgO‐BaO‐B2O3‐SiO2
Authors: TAYLOR PETER , CAMPBELL ALLAN B. , OWEN DERREK G.
Published: June 2006

The limits of miscibility at 650°C were determined for compositions with the mole ratio SiO2/B2O3=1.07 in the systems X2O‐MO‐B2O3‐SiO2 (X = Na,K; M = Mg,Ca,Ba) and Na2O‐MgO‐BaO‐B2O3‐SiO2. The form of the miscibility gaps in the quaternary systems is similar to that previously described for the system Na2O‐ZnO‐B2O3‐SiO2. The topography of miscibility gaps in systems of this type is discussed in detail. The extent of the miscibility gap is correlated with the polarizing power of each cation, X and M (Na > K and Zn ≅ Mg > Ca > Ba) both among the seven quaternary systems and within the single five‐component system examined. The possibility of using empirical correlations observed among the quaternary systems to predict the behavior of other compositions, or of more complex systems, is explored.
Electrical Conduction in Sintered α‐Sb2O4
Authors: MIYAYAMA MASARU , OGI SHUYA , YANAGIDA HIROAKI
Published: June 2006

Electrical conductivity and thermoelectric power were measured on sintered α‐Sb2O4 at 250° to 780°C. Oxygen partial pressure dependence of the conductivity and sign of the Seebeck coefficient showed α‐Sb2O4 to be a p‐type semiconductor above 600°C in the oxygen pressure range of lo5 to 102 Pa. A hopping conduction was proposed from very small hole mobility with an activation energy of 18 kJ/mol.
Numerical Fracture Analysis of Chevron‐Notched Specimens: 11, Stability Condition for Crack Growth
Authors: SAKAI MOTOTSUGU , YAMASAKI KOUZOU
Published: June 2006

Stability conditions for crack growth were studied in chevronnotched specimens with vacious kinds of geometry. The generalized Gibbs free energy G(α) for crack growth in a system composed of a specimen and a testing machine was theoretically considered and analyzed numerically using the results obtained in Part I. We emphasize in both works the importance of the surface boundary effect on the interlaminar shear correction factor k and show that G(α) varies discontinuously with the crack growth if Bluhm's assumption is applied. In addition to the geometric effects on the stability of crack growth, the influence of the testing machine's compliance was considered.
Thermal Conductivity of Silicate and Borate Glasses
Authors: Ammar Mohamed M. , Gharib Sayed A. , Halawa Madiha M. , El‐Batal Hatem A. , El‐Badry Khairy
Published: June 2006

Thermal conductivities of silicate and borate glasses were determined at 30°C by steady‐state methods. From the experimental data, factors representing the contribution of individual oxides (on a weight‐percent basis) were calculated by the least‐squares method. The experimental thermal conductivities and those calculated from the factors obtained agree fairly well.
Effect of Fiber Drawing Tension on Optical and Mechanical Properties of Optical Fiber Waveguides
Authors: Oh Paul S. , Mcalarney John J. , Nath Dilip K.
Published: June 2006

Based on experimental results, the effects of fiber drawing tension on both optical and mechanical properties of optical fibers are discussed. Lower drawing tensions (i.e. > 0.05 N (5 g)) were found to be desirable for fabricating uniform high‐strength fibers, whereas higher drawing tensions (i.e. > 0.5 N (50 g)) were better for low‐loss fibers having a large silica core.
Orthosilicate Analyses: A Measure of Hydration in Pastes of Alite and Portland Cement
Authors: Wu Zhao‐qi , Hriljac Joe , Hwang Chao‐Lung , Young J. Francis
Published: June 2006

The proportion of monomeric silicate in a hydrated paste can be used to estimate the degree of hydration of alite or portland cement. The monomer was estimated by gel permeation chromatography of the trimethylsilylated pastes.
Application of Electrical Analog in Composite Plates
Authors: Virkar Anil V.
Published: June 2006

A simple experimental method is proposed for determining stress intensity factors for composite plates in antiplane loading. The method relies on the fact that, in antiplane loading, a single harmonic potential function describes the state of stress und strain in an isotropic body in much the same way as a single potential function describes local flux densities in an electric conductor.
Effect of Surface Saturation on Transfer of Water in Saturated Ceramic Bodies
Authors: Hrma Pavel
Published: June 2006

The surface condition of saturated clay‐based ceramic bodies is important in the transport of water. Only pure concentration diffusion can occur in bodies with saturated surfaces, whereas transport is enhanced by capillary forces in those with unsaturated surfaces. It is suggested that the transfer of water in a saturated ceramic body is controlled by both concentration and pressure diffusion. A pressure gradient results from capillary forces caused by menisci formed at an unsaturated surface.
Immobilization of Radioactive Cesium in Pyrolytic‐Carbon‐Coated Zeolite
Authors: STINTON DAVID P. , LACKEY W. J. , ANGELINI PETER
Published: June 2006

All waste forms currently being developed for radwaste disposal have difficulty immobilizing cesium. A new waste form was developed to dispose of cesium by loading up to 5 wt% Cs onto zeolite granules. These zeolite particles are then heat‐treated and coated with pyrolytic carbon and/or BC to completely immobilize cesium. The leach rate of cesium from pyrocarbon‐coated zeolite is 3 to 4 orders of magnitude less than for other waste forms. We therefore propose that cesium be removed from the primary waste stream and loaded onto zeolite granules for subsequent coating. The total waste form (primary waste form plus coated zeolite) would have acceptable leach resistance for all radwaste components and be extremely leach‐resistant for cesium.
Processing‐Related Fracture Origins: I, Observations in Sintered and Isostatically Hot‐Pressed A12O3/ZrO2 Composites
Authors: LANGE F. F.
Published: June 2006

Strengths of sintered Al2O3/ZrO2 composites are much lower than those of hot‐pressed composites due to large flaws associated with the sintering process. Fractography has shown that cracklike internal surfaces are at the fracture origins of the sintered materials. It is hypothesized that the cracklike internal surfaces are developed as a result of differential sintering of agglomerates relative to their surrounding powder compact. Isostatic hot‐pressing of the sintered composites quickly eliminated the cracklike internal surface. Flaws responsible for fracture of the isostatically hot‐pressed composites were low‐density regions that are not as easily eliminated.
Chemical Durability of Savannah River Plant Waste Glass as a Function of Waste Loading
Authors: RANKIN W. DUNCAN , WICKS GEORGE G.
Published: June 2006

The leachability of Savannah River Plant (SRP) waste forms was assessed for glass containing up to 50 wt% simulated waste oxides. Leach tests included standard MCC‐1 static tests and pH‐buffered solution experiments. An integrated approach combining leachate solution analysis with both bulk and surface analyses was used to study waste‐glass corrosion as a function of waste loading. Scouting tests on key processing and product parameters, such as viscosity, electrical resistivity, and density were also performed. Results of this study show that the durability of SRP waste glass improves due to the presence of the waste, for waste loadings up to 50 wt% because of the formation of protective surface layers. In addition, the data indicate that the practical limit of waste loading will be determined not by chemical durability of the product, but by processing considerations.
Optical Absorption Characteristics of Ni2+ in Mixed‐Alkali Borate Glasses
Authors: AHMED A. A. , ABBAS A. F.
Published: June 2006

Nickel‐containing mixed‐alkali borate glasses were prepared and their spectral absorption in the visible and near‐ir were measured and used to determine the ligand field strength, Racah parameter, and state of coordination of Ni2+ ions. The change in these parameters with alkali content is discussed in terms of mixed‐alkali effect. Nickel ions were found to occupy octahedral sites in the 20 mol% (Li2O+Na2O) glasses, whereas in the 30 mol% (Na2O+K2O) glasses NiZ+ ions are believed to occupy both octahedral and tetrahedral sites. In most cases slight deviations were observed which increased with increasing alkali content. The results obtained suggest that the substitution of one alkali for another in alkali borate glasses did not produce gross alterations of the glass network sufficient to induce deviations from linearity in property‐composition relations.
Thermophoretic Deposition of Particles in Laminar Flow in a Concentric Annulus
Authors: WEINBERG MICHAEL C.
Published: June 2006

The thermophoretic deposition efficiency of particles in laminar flow in a concentric annulus is considered. A simple, but formally exact expression for the cumulative deposition efficiency is derived (for PrK= 1). This formula is used to calculate the deposition efficiency, and to demonstrate that 100% collection may be easily realized. The effect of the annulus size and the ratio of inner to outer tube wall temperature on the collection efficiency is explored to some extent.
Gamma‐Ray Interaction with Lead Borate and Lead Silicate Glasses Containing Manganese
Authors: GHONEIM N. A. , MOUSTAFFA F. A. , ZAHRAN A. H. , EL DIN F. M. EZZ
Published: June 2006

The optical absorption of high lead borate and lead silicate glasses containing manganese before and after γ‐ray irradiation was studied. To separate the absorption due to manganese from the intrinsic absorption, blank glasses were prepared and measured. The results showed that the visible absorption band before and after irradiation exhibited changes with the radiation dose and chemical composition of the glass. The response of the glasses to gamma irradiation was related to the creation and spread of defect “color centers,” the approach of a saturation condition, and the possible photochemical effect on the transition metal.
Intergranular Crack‐Deflection Toughening in Silicon Carbide
Authors: Faber K.T. , Evans Anthony G.
Published: June 2006

The fracture toughness of three Sic‐based materials was examined and correlated to toughening mechanisms. Crack deflection along grain boundaries in hot‐pressed Sic‐Al2O3 and Sic‐ZrO2 provided notable toughness increases compared to sintered α‐Sic, which fractures trans granularly. The existence of a crack‐deflection mecha nism was confirmed by scanning electron microscopy.
Preparation and Properties of Iron‐Magnesium‐Aluminum Spinel
Authors: Marchant David D. , LambertBates J.
Published: June 2006

Lattice parameter, melting point, electrical conductivity, thermal expansion, and thermal diffusivity/conductivity were measured for 0.25Fe3O4‐0.75MgAl2O4 spinel. The electrical conductivity, which appears to be predominantly electronic (>1 S/m above 500 K), and the melting point (2124 K) make this material a candidate for use as an electrode for a magnetohydrodynamic generator.
Statistical Study of Thermal Shock Damage of a Borosilicate Glass
Authors: ASHIZUKA M. , EASLER T.E. , BRADT R.C.
Published: June 2006

The statistical aspects of thermal shock damage were addressed by examining the strength distributions of quenched specimens. It was observed that slow crack growth effects were minor, and that severe damage commenced near KIc. The increased range of retained strengths observed after thermal shock occurs because the low‐strength portion of the distribution experiences the initial thermal shock damage. Crack arrest in the damaged specimens, examined by an energy balance, indicated that a large number of surface flaws actively extend during the initial stages of thermal shock damage.
Thermodynamic Calculations for the Chemical Vapor Deposition of Silicon Nitride
Authors: KINGON ANGUS I. , LUTZ LEONARD J. , DAVIS ROBERT F.
Published: June 2006

The importance of silicon nitride (Si3N4) prepared by the chemical vapor deposition (C VD) technique is discussed briefly. A computer code was used to calculate CVD phase diagrams useful for the preparation of this material. Theoretical deposition efficiencies and gaseous phase compositions are also reported. The reactants include NH3/SiH4, NH3/SiH2Cl2, NH3/SiCl4, and NH3/SiF4. The effect of N2, H2, and Ar additions, as well as the system pressure, are evaluated. The results are compared with experimental data from the literature.