bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of B2O3 and Binary Aluminoborate Melts at 1600°C
Authors: RIEBLING E. F.
Published: June 2006

Viscosity and density data were obtained up to 1700°C for a series of binary aluminoborate melts that contained as much as 15 mole% (∼21 wt%) Al2O3 and up to 1620°C for pure molten B2O3. Large expansion coefficient decreases and a slight activation energy increase for B2O3 above 1400°C suggested a tightening of its structure. The addition of Al2O3 reduced viscosity and increased activation energy. The decreased compositional dependence of molar volume (compared to SiO2 additions) and the increased expansion coefficients accompanying Al2O3 additions suggested a loosening of the O—B—O structure at 1600°C. Molar volume deviations from ideality were similar to but smaller than those for SiO2 and GeO2 additions at 1300°C. Microclustering of aluminum‐bearing polyhedra appeared to occur at slightly higher boron atom contents than with SiO2 and GeO2 additions.
The System Silica‐Sodium Tetraborate
Authors: ROCKETT T. J. , FOSTER W. R.
Published: June 2006

The phase relations were established for the system silica‐sodium tetraborate. The silica liquidus curve exhibits strong upward concavity but shows no flattening. The tridymite‐cristobalite transformation occurred at 1410°± 10°C. A lowering of the α to β quartz inversion temperature of about 9°C was detected. Primary crystal habits are discussed. The region of metastable subliquidus immiscibility is also discussed and the nature of initial crystallization of the silica‐rich liquid is shown.
Effect of Two‐Dimensional Pressure on the Permittivity of Fine‐ and Coarse‐Grained Barium Titanate
Authors: BUESSEM W. R. , CROSS L. E. , GOSWAMI A. K.
Published: June 2006

The effect two‐dimensional pressure on the permittivity of fine‐ and coarse‐grained ceramic BaTiO3 was investigated. It was shown that, unlike coarse‐grained (10° or above) barium titanate, the permittivity of the fine‐grained (1μ mean) material increased with the increase in two‐dimensional compression perpendicular to the electrode, whereas for an intermediate grain size, the permittivity was almost independent of pressure. The apparent anomalous effect of the fine grain size on the pressure coefficient of permittivity was explained satisfactorily on the basis of an internal stress model using a modified Devon‐shire thermodynamic treatment.
Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3 PbTiO3 ‐PbZrO3 Ceramics Modified with Certain Additives
Authors: OUCHI HIROMU , NISHIDA MASAMITSU , HAYAKAWA SHIGERU
Published: June 2006

Effects of additives on the piezoelectric properties of Pb(Mg1/3Nb2/3)O3‐PbTiO3‐PbZrO3 ceramics in a perovskite‐type structure are described. The tetragonality of Pb(Mg1/3Nb2/3)0.375‐Ti0.375Zr0.25O3 ceramics increased with the addition of NiO, Cr2O3, or Fe2O3 but decreased with the addition of MnO2 or CoO. The dielectric and piezoelectric properties of the base composition were improved markedly through selection of additives in proper amounts. Addition of NiO yielded a high dielectric constant and planar coupling coefficient for compositions at the morphotropic transition boundary. High mechanical Q‐factors and low electrical dissipation factors were obtained by addition of MnO2. Addition of both NiO and MnO2 produced a mechanical Q‐factor of 2051 and a planar coupling coefficient of 0.553. The resonant frequency of Pb(Mg1/2Nb2/3)0.4375Ti0.4375 zr0.125O3 containing MnO2 had very low temperature and time dependence. The microstructure indicated that ceramics with a high mechanical Q‐factor had a fine, uniform grain structure. Addition of Cr2O3 retarded grain growth and addition of MnO2, NiO, CoO, or Fe2O3 promoted grain growth in the ternary system.
Desulfurization of Pyrite
Authors: BLACHERE J. R.
Published: June 2006

Reactions occurring during the heating of pyrite depend on the atmosphere. Fe2O3 is formed under good oxidizing conditions; FeS is formed when the atmosphere is low in oxygen. This is shown by DTA, X‐ray diffraction, and total sulfur determinations on iron sulfides, on their mixtures with illitic clays and inert materials, and particularly on shales. The importance of the steam that evolves from the clay is shown. A mechanism for the reactions involving pyrite during the firing of a brick is discussed.
Phase Transformation in Barium Orthoferrate, BaFeO3‐x
Authors: MORI SABURO
Published: June 2006

The compound BaFeO3‐x exists in many forms, the hexagonal phase having a wide range in oxygen content (BaFeO2.63–2.92). The other phases have the limited compositions and the distinct structures of perovskite: triclinic I, BaFeO2.50; triclinic II, BaFeO2.64–2.67; rhombohedral I and II, BaFeO2.62–2.64; and tetragonal, BaFeO2.75–2.81. The phases contain Fe4+ ions correlating with the oxygen content. The hexagonal phase shows a continuous change in oxygen content with temperature down to BaFeO2.63. The perovskitelike phases, however, show characteristic transformations. The triclinic I phase oxidizes to the triclinic II form at 320° to 500°C and to the hexagonal form at 720° to 915°C in oxygen. These transformations are related to oxidation‐reduction of iron ions (Fe3+⇌ Fe4+).
Effect of Inclusions on Grain Growth of Oxides
Authors: ARIAS ALAN
Published: June 2006

Effects of 10 vol% Cr, Mo, W, Mn, Ni, Ti, BN, and ZrB2 on the grain growth of Al2O3, HfO2, MgO, and ZrO2 were investigated by vacuum heat‐treating previously vacuum hot‐pressed specimens containing a layer of the cermet and a layer of the corresponding oxide. Most of the metals and compounds inhibit grain growth of the four oxides investigated. Some of the additions enhance grain growth, whereas others react with the matrix oxide. In most systems, the oxide layer adjacent to the cermet showed exaggerated grain growth at the interface. No correlation was found between reactivity, melting point, and volatility of the metal addition and grain growth of the matrix oxide.
Infrared Radiation of Titanium Boronitride
Authors: GRENIS ALBERT F. , LEVITT ALBERT P.
Published: June 2006

The infrared radiation properties and characteristics of the ternary solid, titanium boronitride, were investigated in the wavelength region from 1.0 to 10.0μ at 1300°K. The normal spectral emittance, integrated normal total emittance, and infrared radiation intensity were determined for this material with both rough and polished surfaces. The normal total emissivity of the material was also calculated based on the weighted average of the normal total emissivities of the constituent compounds. The results are in good agreement with the experimental values.
Solubilities of Ar, N2, CO2, and He in Glasses at Pressures to 10 Kbars
Authors: FAILE S. P. , ROY DELLA M.
Published: June 2006

Glasses containing up to several percent of Ar, N2, and CO2 were prepared at 2000 to 150,000 psi and up to 950°C and retained under ambient conditions. The solubilities are presented as a function of pressure, temperature, and composition of glass. Solubilities of O, He, and H2O were also investigated in various glass compositions, especially K2O–4SiO2 and B2O3. The evolution of the gases at atmospheric pressure was followed by electron microscopy and density measurements.
Electrical and Magnetic Properties of the System SrFeO3–BiFeO3
Authors: MacCHESNEY J. B. , JETZT J. J. , POTTER J. F. , WILLIAMS H. J. , SHERWOOD R. C.
Published: June 2006

Perovskite phases containing iron in both the tetravalent and trivalent states were prepared by equilibration at high oxygen pressures. Small bismuth additions to SrFeO3 resulted in high conductivity (101 to 103 (ohm‐cm)–1 at 26°C) and antiferromagnetic order below 130°K. Distortion to tetragonal symmetry occurs approximately at the composition Bi0.3Sr0.7FeO2.87, but higher bismuth concentrations (up to 80 mole %) give rise to a second cubic phase region which shows decreased conductivity (∼10–5 (ohm‐cm)–1) and weak ferromagnetism with ordering temperatures higher than 26°C. Rhombohedral specimens Bi0.9Sr0.1FeO2.96 and BiFeO3.01 are anti‐ferromagnetic and have comparatively low conductivity.
Dielectric Aging and Microstructure in the System BaTiO3‐CaTiO3
Authors: COOKE F. W. , BRADT R. C. , DeVRIES R. C. , ANSELL G. S.
Published: June 2006

The effect of precipitation of a dispersed CaTiO3–rich phase on the shape, organization, and thickness of ferroelectric domains in BaTiO3 was studied. No morphologically related precipitate could be produced despite the close structural similarity of the phases involved. These effects, when correlated with changes in dielectric aging behavior, show that dielectric aging is not a simple thermally activated process.
Phase Equilibria in the System CaO‐Yb2O3
Authors: BARRY THOMAS L. , STUBICAN V. S. , ROY RUSTUM
Published: June 2006

Phase equilibrium relations in the system CaO‐Yb2O3 were studied. Results of this work demonstrated the existence of four crystalline phases: Yb2O3.3CaO, Yb2O3.2CaO, Yb2O3°CaO, and 2Yb2O3°CaO. The 2Yb2O3°CaO phase is metastable at all temperatures and was obtained only by rapid quenching from the melt. The crystalline solubility limit of YbaO3 in CaO at 1850°C is slightly greater than 8 mole %, whereas no solubility of CaO in Yb2O3 was detected. All four compounds have subsolidus minimums of stability and dissociate into the component oxides below 1800°C. Data are also presented for the systems CaO‐Gd2O3 and CaO‐La2O3.
Ferroelectrics of Ultrafine Particle Size: II, Grain Growth Inhibition Studies
Authors: HARKULICH THEODORE M. , MAGDER JULES , VUKASOVICH MARK S. , LOCKHART ROBERT J.
Published: June 2006

Inhibition of grain growth in pure, fine‐particle‐size barium titanate bodies by coating the surfaces of the barium titanate particles with tantalum oxide was so effective that doping with a sintering aid was necessary for densification of the bulk material at temperatures below the melting point. A correlation, which was independent of starting particle size, was established between inhibitor concentration and final grain size of the fired bodies. Barium titanate bodies of predetermined grain size not larger than 2000 A were obtained even with extended firing schedules. In the smallest grain sizes, the Curie point was shifted below the measured temperature range, and hysteresis losses were reduced markedly. The dielectric constant had a smooth variation from approximately 3000 at room temperature to 800 at 180°C.
Crack Propagation Method for Measuring Grain Boundary Energies in Brittle Materials
Authors: CLASS W. H. , MACHLIN E. S.
Published: June 2006

A cleavage technique was used to measure the surface free energy and the grain boundary energy for twist boundaries of varying twist angles in potassium chloride. The results for the surface energy and its temperature dependence are in good agreement with theory and experiment. Based in part on this agreement and the measured misfit orientation dependence, the grain boundary energy values obtained are concluded to be reasonable.
Analysis of Deformation of a Fireclay Refractory
Authors: HULSE C. O. , PASK JOSEPH A.
Published: June 2006

Rate process theory was applied in a study of the creep behavior of a fireclay refractory (firebrick) after different heat treatments. The analysis was based on the assumption that, in the absence of phase changes, equivalent deformation substructures are produced for a given strain at constant stress independent of temperature. An activation energy of about 170 kcal/mole was determined for the flow process in a heat‐treated firebrick, which corresponds closely to the value for mullite specimens. Varying but higher values obtained under different test conditions indicated that phase changes were also occurring during the creep tests. The effect of the amount and texture of the components on the creep behavior and strength of the firebrick specimens is discussed. Useful correlations based on this approach are presented, making it possible to predict creep behavior at constant or variable temperatures and also to calculate stress distributions through a wall containing a temperature gradient after a given strain is reached in a given time.
Simplified Method for Calculating Elastic Moduli of Ceramic Powder from Compressibility and Debye Temperature Data
Authors: SOGA NAOHIRO , ANDERSON ORSON L.
Published: June 2006

A method is presented for calculating the isotropic elastic moduli of ceramic powder from the compressibility and the Debye temperature. Young's and shear moduli of polycrystalline MgO, Al2O3, BeO, and TiO2 were computed from compressibility and Debye temperature data by the present method and compared with values determined by the standard resonance method; values agreed within a few percent. An advantage of the present method is its applicability to specimens too small for the resonance method, because both compressibility and Debye temperature can be determined on powder or thin‐film forms.
Theorems for Calculation of Weight Ratios to Produce Maximum Packing Density of Powder Mixtures
Authors: LEWIS H. D. , GOLDMAN A.
Published: June 2006

Two mixing theorems are proposed to provide methods for (1) testing for possible greater packing density of powder mixtures compared with unmixed components, (2) predicting which of several powders or binary combinations of these powders gives the highest density, and (3) calculating the weight mixing ratio to give maximum packing density for particular combinations. Calculations are based on proper use of particle “size” data obtained from typical commercial “size” measuring devices, proper definitions of mixing and the fraction of powder occurring in “size” intervals, and functional or nonfunctional description of the data.
Activities in Li2O‐, Na2O, and K2O‐SiO2 Solutions
Authors: CHARLES R. J.
Published: June 2006

Activities of alkali metal oxides and silica are calculated for regions of the Li2O‐SiO2, Na2O‐SiO2, and K2O‐SiO2 phase diagrams where volatility, cell potential, and thermodynamic data are available. For the high‐silica composition regions, activities are calculated from the stable phase diagrams and assumptions based on sub‐regular solution behavior. These data permit estimates of the phase boundaries for the metastable two‐liquid regions in the Li2O and Na2O systems which may be compared with experiment. An estimate is also made of the critical point for K2O‐SiO2 to determine whether metastable phase separation in this system will be experimentally obtainable.
Structure of Glasses and Melts in the Na2O·GeO2·B2O3 System
Authors: RIEBLING E. F. , BLASZYK P. E. , SMITH D. W.
Published: June 2006

Density and viscosity results are presented for ternary Na2O·GeO2·B2O3 melts (∼600° to 1300°C) and glasses containing as much as 35 mole % Na2O. Synthetic partial molar volume models indicate a fairly broad stability region for BO4 tetrahedra in the B2O3‐rich melts. Similar models for GeO2‐rich melts reveal a more limited stability region for GeO6 octahedra. The expansion coefficient contours and viscosity isotherms confirm the volume‐based conclusions for the liquid state. The high‐temperature volume models were used to develop glass volume models that agree to within several percent of experiment. It has been concluded that the melts and glasses possess similar structures. The relatively greater compositional stability of GeO6 octahedra in the presence of B2O3 (compared to Al2O3) can be related to the smaller average number of oxygens around boron (III), at a fixed O/Ge ratio, compared to aluminum (III). Evidence is presented for a slight decrease of the thermal stability of GeO6 octahedra in the GeO2‐rich melts above about 1000°C.
Electrical Conductivity of Uranium Dioxide
Authors: BATES J. L. , HINMAN C. A. , KAWADA T.
Published: June 2006

The electrical conductivity of nearly stoichiometric single‐crystal and polycrystalline uranium dioxide was measured from room temperature to 3000°K. Below approximately 550°K, the curve of log σ versus T−1 is linear with a calculated activation energy of approximately 0.17 ev. Between 550° and 1250°K, however, the shape of the curve changes; this change varies from one specimen to another. The electrical conductivity increases rapidly with increasing temperature above 1250°K with a change from p‐type to n‐type conduction. The best linear fit of the log σ versus T−1 curve above 1400°K is σ= 3.57 × 103e−(1.15 ev/KT). Above 1900°K, the curve deviates slightly from linearity and is best fit by the equation σ= 2.10 × 10−2T1.4e−(0.916 ev/KT).
Curie Temperature and Birefringence Variation in Ferroelectric Lithium Metatantalate as a Function of Melt Stoichiometry
Authors: BALLMAN A. A. , LEVINSTEIN H. J. , CAPIO C. D. , BROWN H.
Published: June 2006

The ferroelectric Curie temperature of lithium metatantalate is linearly dependent on the melt stoichiometry. Curie temperatures ranging from 700° to 540°C were measured on single crystals and correspond to a melt composition variation of approximately 6 mole % on each side of apparent stoichiometry. High Curie temperatures occur at high lithium oxide concentrations. The Curie temperature of LiTaO3 grown from a nominally stoichiometric melt is 618°± 5°C. The birefringence of lithium metatantalate is also a linear function of the melt composition. Birefringence values from +0.006 to –0.004 were measured and correspond to the melt composition variation described above with positive birefringence associated with low Curie temperatures.
Vapor Pressure of Gd2O3 from 2350° to 2590°K
Authors: MESSIER D. R.
Published: June 2006

Knudsen evaporation experiments were made on gadolinium sesquioxide from 2350° to 2590°K. Two sets of Knudsen cell data yielded average values of 468.7 ± 0.8 and 471.0 ± 0.5 kcal/mole for the assumed evaporation reaction

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The results indicate that the evaporation coefficient may be much less than one.
High‐Temperature Behavior of Beryl and Beryl Melts at High Pressure
Authors: MUNSON RONALD A.
Published: June 2006

The pressure dependence of the nonreversible thermal decomposition of natural beryl was examined between 15 and 50 kbars using the high‐pressure “belt” apparatus. The principal products of decomposition are silica, phenacite, and chrysoberyl. As the pressure is increased the thermal stability of beryl decreases and the thermal stability of the decomposition products increases. Silica crystallizes from beryl melts as coesite at the higher pressures and as quartz at the lower pressures.
Electrical, X‐Ray, and Thermal Expansion Studies in the System KNbO3‐AgNbO3
Authors: WEIRAUCH DONALD F. , TENNERY VICTOR J.
Published: June 2006

Unlike the KNbO3‐NaNbO3 system, the KNbO3‐AgNbO3 system possessed a very limited degree of solid solution between its end‐members. Solid solution of AgNbO3 in KNbO3 was limited to slightly less than 6 mole %, and solid solution of KNbO3 in AgNbO3 was limited to less than 0.5 mole %. Because of a tendency for the K1‐xAgxNbO3 system to lose oxygen spontaneously during firing when 0.06 ≤x≤ 0.995, the system could not be treated as a true binary system. The compositions in the KNbO3 solid solution region (0 ≤x < 0.06) were ferroelectric at room temperature. Lattice parameter, relative permittivity, and thermal expansion measurements were made on specimens in the region 0 ≤x≤ 0.06.
Effects of Water Vapor on the Initial Sintering of Calcia
Authors: PETERSEN RONALD O. , CUTLER IVAN B.
Published: June 2006

The effect of water vapor on the initial sintering kinetics of calcium oxide was studied at 920” to 1123°C. In the range of PHI() from 8 × 10W4 to 487 mm Hg, water vapor increased the rate of sintering. The initial sintering kinetics followed the model for volume diffusion with calculated diffusion coefficients dependent on PH2O, which varied from (P,H2O)1/2 at pressures between 6.1 and 50 mm Hg to (PIH2O)1/2 at pressures between 244 and 487 mm Hg. The activation enthalpy varied from 123 ± 7 kcal/mole when PH2O= 0.04 mm Hg to 103 ± 3.5 kcal/mole at PH2O 243.9 mm Hg.
Diffusional Creep Mechanisms
Authors: GIFKINS R. C.
Published: June 2006

Creep extension without dislocation movement across grains may be obtained in polycrystalline aggregates by diffusion through the grains (Nabarro‐Herring) or through grain boundaries (Coble). These mechanisms are compared with a suggestion that creep can occur by grain‐boundary sliding controlled by diffusion which can lead to movement along the boundary of grain‐boundary protrusions and can be accommodated by diffusion around triple points.
Strengthening Glass‐Ceramics by Application of Compressive Glazes
Authors: DUKE D. A. , MEGLES J. E. , MACDOWELL J. F. , BOPP H. F.
Published: June 2006

Glasses in the Na2O–Ba0–A12O3‐Si02 system, nucleated with TiO2, were heat‐treated to effect controlled crystallization. Resulting materials consisted of a dense, micro‐crystalline mixture of nepheline (Na20–A12O3‐2SiO2) and barium feldspar (BaO‐A12O3‐2Si02) in a glassy matrix. Thermal expansion coefficients (O° to 300° C) of these bodies ranged from 75 to 125 × 10 –7/°C. Glazes in the Na2O‐CaO‐PbO‐B2O2‐A1203‐SiO2 system having expansion coefficients of about 40 to 80 × 10 ‐7/0°C were applied to the glass‐ceramics. On firing, the glazes matured well and reacted with the bodies to form interlocking crystals at the interface. This interfacial region was investigated using several instrumental techniques, and the crystals were identified as plagioclase feldspar. Applying these compressive glazes resulted in modular of rupture up to five times that of the initial glass‐ceramic. Calculated strengths correlated well with experimental values.
Diffusion in the System K2O‐SrO‐SO2 I, Effective Binary Diffusion Coefficients
Authors: COOPER A. R. , VARSHNEYA A. K.
Published: June 2006

Concentration distributions of potassium and strontium were measured with the electron probe after inter diffusion in the system K2O‐SrO‐SiO2 at 750° C for periods of 4 to 14 hr. The effective binary diffusion coefficients for multicomponent diffusion determined for K2O and SrO behaved in accordance with Fick's laws. The utility and limitation of these coefficients to describe inter diffusion in condensed multicomponent systems are discussed.
Preferred Orientation in Microstructures of Eutectics Between Compounds
Authors: MOORE JOHN W. , VAN VLACK LAWRENCE H.
Published: June 2006

The microstructures of eutectics between compounds were studied for systems MnO‐MnS, NaCl‐NaF, NaBr‐NaF, LiF‐NaF, and FeO‐FeS. With the exception of FeS, all the compounds had the NaCl‐type structure. In the systems having only NaCl‐type structures, the lamellas of the two eutectic phases had matching crystal orientations. There was less consistency among the eutectic systems, however, than between the phase pairs. The crystal growth directions in all five systems were different, and no more than two of the systems had the same set of inter‐facial planes. One must conclude that the two phases within a eutectic of compounds do not solidify independently of one another. It is suggested that the two phases of an NaCl‐type eutectic pair crystallize as a “single” ionic crystal with imperfections present to accommodate the dimensional mismatch.
Mechanical Degradation of MgO by Water Vapor
Authors: JANOWSKI K. R. , ROSSI R. C.
Published: June 2006

The effect of exposure to the laboratory atmosphere on the fracture stress and Young's modulus of poly crystalline magnesium oxide was studied. The observed degradation of mechanical properties was attributed to chemical attack by atmospheric water vapor. The rate and extent of degradation depended on the amount and nature of porosity in the specimens.
Diffusion of Oxygen in Selected Monocrystalline Rare Earth Oxides
Authors: BERARD M. F. , WIRKUS C. D. , WILDER D. R.
Published: June 2006

The diffusion of oxygen in monocrystalline ScaO3, YzO3, Dy,O2, HosO3, Er2O3, Tm2O2, and Lu2O3was measured by a thermobalance technique. The reoxidation of partially reduced crystals of these materials was treated as a diffusion‐controlled process with a moving boundary. Large diffusion coefficients and fairly low activation energies were found for this process, in agreement with a proposed migration mechanism which involves the inherently defective anion sublattice of these materials.
Chemical Strengthening of Polycrystalline Alumina
Authors: KIRCHNER HENRY P. , GRUVER ROBERT M. , WALKER RALPH E.
Published: June 2006

Low‐expansion solid solution surface layers formed by reaction of Cr2O3 and Al2O3 were used to chemically strengthen alumina bodies. The surface layers were formed by packing the samples in Cr2O3 powder and heating to high temperatures. Fluorides or chlorides were added to the packing material, leading to substantial additional improvement. The flexural strengths of the control samples were increased by refiring in the presence of the products of decomposition of the fluorides. At high concentrations of fluorides in the packing material, the outside dimensions and the weights of the samples decreased during the treatments.
Effect of Graphite on Microstructure and Drying Shrinkage of Clay
Authors: KILGORE R. V. , WILLIAMSON W. O.
Published: June 2006

Graphite specimens bonded by kaolinite‐illite clay, in which planar orientation of the graphite flakes and clay platelets had been produced by deformation, showed enhanced differential drying shrinkage with increased graphite content. The greater shrinkage was perpendicular to the plane of preferred orientation. Comparable additions of quartz grains to the clay made the drying shrinkage less differential. The volume drying shrinkage was first increased and then decreased by successive additions of graphite. The increase was ascribed to the increasing concentration of water in the clay bond as the clay content diminished. The subsequent decrease appeared because the drying shrinkage of the clay was reduced near the graphite and because the graphite itself did not shrink.
Vapor Pressure of Hypostoichiometric Urania as a Function of Composition
Authors: SZWARC R. , LATTA R. E.
Published: June 2006

The vapor pressure of hypostoichiometric urania was measured as a function of temperature for a series of compositions. The data were obtained by an entrainment technique in which weight loss of a specimen vaporizing at high temperatures in a stream of carrier gas is followed continuously with a recording thermobalance. Use of suitable atmospheres produced constant vaporizing compositions which vaporized pseudocongruently. Equations obtained for the vapor pressure are:

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Model for Rheology of Halloysite Suspensions
Authors: KENT RAYMOND C. , GORDON RONALD S. , HAHN SANG J.
Published: June 2006

A quantitative rheological model was developed for predicting the non‐Newtonian flow behavior of aqueous halloysite suspensions. Halloysite clay from the large Utah deposits was used for this investigation because of its unique tubular morphology. The flow behavior of the suspensions was characterized by the semi empirical Ree‐Eyring generalized viscosity equation. The β parameter in the Ree‐Eyring equation, a measure of the relaxation time for the flow process, was very sensitive to variations in the pH and volume fraction solids. When the logarithm of 0 was plotted versus pH (4 to 11) for halloysite suspensions containing 15, 20, and 25 wt% solids, linear plots with increasing slopes were obtained. Attempts were made to show the physical significance of the parameters introduced in the model.
Technique for Measuring Grain Boundary Mobility and Its Application to Potassium Chloride
Authors: GIBBON C. F.
Published: June 2006

A simple technique for investigating boundary mobility is outlined and applied to the study of boundary migration in melt‐grown bicrystals of KCl containing pure twist boundaries. An unexpectedly high activation energy, 4 to 6 ev, is found for movement of the twist boundaries.
Spectral Reflectance of Sintered Oxides
Authors: SCHATZ ELIHU A.
Published: June 2006

Spectral reflectance in the 0.23 to 2.65μ region was measured on sintered oxides of Al2O3, CeO2, TiO2, Y2O3, and ZnO. The oxides were sintered at various temperatures up to 1550°C. Large changes in reflectance occurred as a result of different extents of sintering of the specimens. The data were interpreted in terms of changes in the distance between the particles, the water content, and the surface roughness. Loss of trace‐water and decrease in surface roughness result in an increase in reflectance, whereas shrinkage of the specimen causes a decrease in reflectance.
High‐Field Losses of Adulterated Lead Zirconate‐Titanate Piezoelectric Ceramics
Authors: GDULA R. A.
Published: June 2006

The high‐field losses of adulterated lead zirconate‐titanate ceramics were compared on the basis of rates of temperature rise of standard‐size samples in the same transducer configuration. Systematic chemical modification in light of the ionic model of the perovskite structure was used to produce ceramics with widely varying high‐field behavior. High‐field losses could be greatly reduced by adulteration of either cation site with ions of lower than normal valency. At 1 at.% concentration, lowest losses were found with adulterants whose valence was one unit less than normal. The results are explained as stoichiometric effects. Normal air‐fired lead zirconate‐titanate ceramics are considered to be deficient in metal tons. Adulteration with subvalent cations reduces the iotal oxygen content of the ceramic and brings it toward true ABO3 stoichiometry. Lowest losses are postulated for truly stoichiometric bodies.
Relative Energies of Tilt Boundaries in Aluminum Oxide
Authors: SHACKELFORD JAMES F. , SCOTT WILLIAM D.
Published: June 2006

The relative grain boundary energy and surface diffusion coefficient of aluminum oxide were determined by observing the thermal grooving behavior of a series of bi‐crystals containing symmetric tilt boundaries. The relative energy for high tilt angles (30° to 150°) was roughly constant and equal to 0.54. The variation of relative energy with tilt angle was consistent with a dislocation core model for grain boundaries. The surface diffusion coefficient was:

The agreement of this value for a vacuum etch with previous data for etches in air ruled out the oxygen ion as a possible rate‐controlling diffusion species.
Phase Equilibria in the Systems NiO‐Cr2,O3,‐O2, MgO‐Cr2O3−O2, and CdO‐Cr2,O3,‐O2, at High Oxygen Pressures
Authors: MULLER OLAF , ROY RUSTUM , WHITE WILLIAM B.
Published: June 2006

Phase equilibria were determined for the systems NiO‐Cr2O3−O2, MgO‐Cr2O3,‐O2, and CdO‐Cr2O3−O2 from 450° to above 850° C and at oxygen pressures of from 2 to 3500 atm. Only two intermediate phases were found in the nickel system: NiCrO., (CrVO4 structure) and the spinel NiCr2O4. The magnesium and cadmium systems are similar in that they have three analogous phases: the low‐temperature α‐MgCrO4 and α‐CdCrO4 (both with the CrVO4 structure), the high‐temperature β‐MgCrO4 and β‐CdCrO4 (both with the α‐MnMoO4 structure), and the spinels MgCr2O4 and CdCr2O4. The cadmium system contains an additional phase, Cd2CrO5, which is primitive monoclinic.
The System Al‐O
Authors: YANAGIDA HIROAKI , KRbGER F. A.
Published: June 2006

Previous data by other writers who infer the existence of aluminum suboxides in the solid state are critically discussed and alternatively interpreted. High‐temperature X‐ray diffraction patterns previously attributed to crystalline Al2O and AlO are identified as those of Al4C3 and AlTaO2, respectively. The melting curve observed by Baur and Brunner, suggesting the existence of a compound of the approximate composition Al2O9, corresponds to the pseudobinary system Al2O3−Al4C3. The T‐x melting curve of the system Al2O3−Al was determined. There is no indication of the existence of crystalline aluminum suboxide, the only condensed phases being α‐Al2O3 and Al. The liquidus indicates demixing of liquid Al and molten Al2O3. There is very limited intersolubility, and the addition of Al does not lower the melting point of Al2O3 measurably. With these facts and some additional information from the literature about the gaseous species, the P‐T‐x diagram of the system Al‐O was constructed.
A Consistent Set of Thermodynamic Values for Plutonium Mononitride
Authors: SPEAR KARL E. , LEITNAKER JAMES M.
Published: June 2006

Values given in the literature for the heat of formation of plutonium mononitride range from — 70 to — 76 kcal/mole. This paper shows that if estimated entropy and high‐temperature heat capacity data are used to derive a reasonable set of high‐temperature thermal functions for the mononitride, ΔH0f,298 (PuN) values obtained by both second‐and third‐law methods from equilibrium data agree. The equilibrium data are from measurements reported in the literature and cover a range from 700° to about 3040°K. A calorimetric value of —70.2 kcal/mole reported for the PuN heat of formation appears to be in disagreement with the derived equilibrium value of — 76.0 kcal/mole, but this difference can be explained by a composition uncertainty.
Evaporation of Hypostoichiometric Plutonium Dioxide from 2070° to 2380°K
Authors: MESSIER DONALD R.
Published: June 2006

Total vapor pressures of PuO2‐x, compositions were measured gravimetrically with tungsten Knudsen cells from 2070° to 2380°K. The vapor pressure equation for the composition approximating the congruent one, PuO1.82, is

where Pc, is the pressure if the vapor is assumed to be entirely PuO2(g). The evaporation of PuO1.562 was univari‐ant, indicating the presence of two condensed phases, and that of PuO1.62 was bivariant from 2240° to 2380°K; this result confirms that the phase boundary of the PuO2‐x, phase remains at Pu1.61 at temperatures close to the liquidus.
The System MgO‐Cr2O3−Fe2O3 at 1300°c in Air
Authors: ULMER G. C. , SMOTHERS W. J.
Published: June 2006

Phase relations in air at 1300°C were determined for the system MgO‐Cr2O3−Fe2O3 by conventional quenching techniques. Details of the phase equilibria were established for: (1) the sesquioxide solid solution between Cr2O3 and Fe2O3, (2) the spinel solid solution field between MgCr2O4 and MgFe2O4, and (3) the periclase solid solution field for MgO. Selected tie lines connecting coexisting compositions were established with X‐ray diffractometer data. Diffuse reflectance spectra, diffractometer intensity ratios, and lattice parameter measurements were obtained for quenched samples to study the structural inversion in the spinel series MgCr2O4‐MgFe2O4.
Vacuum Hot‐Pressing of Magnesium Aluminate Spinel
Authors: RUMMLER DONALD R. , PALMOUR HAYNE
Published: June 2006

The densification kinetics of magnesium aluminate spinel during vacuum hot‐pressing were studied between 1175° and 1460° C and from 500 to 5100 psi. A phenomenologi‐cal rate equation, which suggests a logarithmic relation between strain rate and porosity, excellently described the observed densification. Treating porosity as an independent variable was shown to be reasonable; it does not functionally restrict porosity as a modifier of the applied stress. The strain rate dependence on porosity decreased at a porosity of approximately 0.15. Below 1350° C the densification characteristics were similar to those reported for other oxide systems. At 1450°C an increase in the stress dependence of the densification rate and an interaction between stress and porosity suggested that plastic flow by dislocation motion was an operative mechanism during densification.
Interrelation of Hardness, Modulus of Elasticity, and Porosity in Various Gypsum Systems
Authors: SOROKA I. , SEREDA P. J.
Published: June 2006

The interrelation of hardness, modulus of elasticity, and porosity was investigated in four gypsum systems. Results suggest that intergrowth and interlocking of crystals significantly affect mechanical behavior, at least hardness and modulus of elasticity, E. In addition, both properties are related to porosity, p. This relation can be described empirically by the exponential expression E = Eo exp (— p).
Secondary Grain Growth of Li2O‐A12O3‐SiO2‐TiO2 Glass‐Ceramics
Authors: CHYUNG C. K.
Published: June 2006

The kinetics of secondary grain growth in a Ti02‐nucleated β‐spodumene solid‐solution glass‐ceramic was studied. The thermal stability of the grains was excellent. Grain growth followed the cube‐root‐of‐time law. The activation energy of the grain boundary migration was 55 ± 10 kcal/mol. Grain growth inhibition due to Ti02 precipitates and the residual glassy phase was closely examined. The excellent thermal stability of the grains is due to grain growth inhibition by the residual glassy phase, not by rutile precipitates. It is suggested that the diffusion of A2+, and probably the simultaneous diffusion of Li+, through the residual glass is the rate‐limiting process for the grain boundary migration.
Role of P2O5 in TiO2‐Opacified Porcelain Enamels
Authors: EPPLER R. A. , SPENCER‐STRONG G. H.
Published: June 2006

Phosphorus pentoxide is known to affect the reflectance and color of TiO2‐opacified porcelain enamels. It has been postulated that P2O5, impedes the anatase‐to‐rutile phase transformation. This hypothesis was tested by applying recently developed analytical procedures based on X‐ray diffraction analysis to a typical porcelain enamel cover coat system. The inversion of anatase to rutile was not significantly affected by P2O5. Instead, in the range 0.5 to 4%, as P2O5 concentration was increased in the frit, the rate of crystallization of both anatase and rutile also increased, with the rate of increase of anatase being about twice that of rutile.
X‐Ray Stress Analysis of WC‐Co Cermets: I, Procedures★
Authors: FRENCH DAVID N.
Published: June 2006

The factors that influence the measurement of stress by the “two‐exposure” X‐ray diffractometer technique in the WC phase of WC‐Co cermets were studied. Chromium Karadiation was used on the (1012) line of WC (2θ= 135.8°). The X‐ray values of Young's modulus and Poisson's ratio are 105×106 psi and 0.19, respectively, and the X‐ray stress factor is 1.51 × 108 psi/Å. The measured stresses are biaxial. Because penetration is limited to less than 5 μm for CrKa radiation, extreme care in surface preparation and heat treatment is required. A suitable preparation is metallographic polishing with 6 μm diamond followed by annealing in hydrogen at 750°C. This treatment allows measurement of about 40, 000 psi compressive temperature stress inherent in the WC particles resulting from differences in coefficients of thermal expansion between WC and Co. Mechanical stresses can also be measured; they arise from external forces such as grinding, polishing, and sand blasting. Mechanical and temperature stresses cannot always be clearly distinguished, however.
Heat of Annealing in Simple Alkali Silicate Glasses
Authors: TISCHER R. E.
Published: June 2006

The enthalpy changes associated with annealing of glass were studied in simple and mixed alkali silicate glasses. The data indicate that during prolonged annealing the glass comes to a metastable equilibrium state and has a unique heat of solution which depends on its fictive temperature. The heats of solution of these glasses show a linear dependence on fictive temperature, and the magnitude of this dependence is related to the molar volume of the glass. The significance of these heat effects is discussed. The maximum heat effects which can occur on annealing sodium silicate glasses were measured and were approximately half as large as the enthalpy changes associated with the structural arrangements that occur during crystallization of these glasses.
Slip Behavior and Hardness Indentations in MnSe and MnSe‐MnS Solid Solutions
Authors: RIEWALD PAUL G. , VAN VLACK LAWRENCE H.
Published: June 2006

Single crystals in the solid solution series MnSe‐MnS were prepared, and selected surfaces were indented with either a Vickers or a Knoop microindenter. Information on mechanical behavior was obtained by observation of slip traces around indentations and by study of Knoop hardness anisotropy. Manganous selenide exhibits {111} and {110} as primary and secondary slip mechanisms, respectively, in contrast to the {110} mechanism preferred by MnS. In the system MnSe‐MnS, the primary slip mechanism changes gradually with composition. The {110} mechanism of MnS is much more sensitive to temperature than the {111} mechanism of MnSe, and a large solid solution hardening effect accompanies the substitution of sul‐fide for selenide ions.
The Systems PbF2‐AlF3 and CaF2‐AlF3
Authors: SHORE R. G. , WANKLYN BARBARA M.
Published: June 2006

The compound Pb3Al2FI12 is reported in the system PbF2‐AIF3. It is tetragonal, I 4/m, d0= 14.23 å, co= 7.20 Å. A phase diagram for the system is presented on the basis of DTA and X‐ray Powder Patterns. The compound melts incongruently at 649°C. Solid solubility of AlF3 in PbF2 occurs with up to 15 mol% AlF3. Data for the system CaF2‐A1F3 is compared with previous reports.
Cation Self‐Diffusion in Polycrystalline Y2O3 and Er2O3
Authors: BERARD M. F. , WILDER D. R.
Published: June 2006

A tracer sectioning technique was used to measure cation self‐diffusion coefficients in fully dense polycrystalline YaO3 and Er2Os under oxidizing conditions. The results are described by the relations

image

for Y2O3 (1400° to 1670°C), and

image

for Er2O3 (1400° to 1700°C). The greater activation energy for erbium diffusion in erbia may be partly attributable to a mass effect.
Behavior of Bubbles of Oxygen and Sulfur Dioxide in Soda‐Lime Glass
Authors: GREENE C. H. , PLATTS D. R.
Published: June 2006

Bubbles of sulfur dioxide are dissolved by soda‐lime glass containing arsenic or ferric oxide at a rate which follows a square‐root‐of‐time law, indicating a diffusion process. Mixtures of sulfur dioxide and oxygen are dissolved very rapidly as long as both gases are present, whereas an excess of either gas remaining in the bubbles is adsorbed at the normal rate, which depends on the composition of the glass. Apparently sulfur dioxide is dissolved by oxidation either by oxygen in the bubble or by oxygen diffusing from oxidizing constituents in the glass, whereas oxygen is dissolved by diffusing into the glass to react with reducing constituents.
Nitrogen Diffusion in Uranium Nitride as Measured by Alpha Particle Activation of 15N
Authors: HOLT J. B. , ALMASSY MARCIA Y.
Published: June 2006

A new technique, based on the nuclear activation reaction 15N(α, n)18F, was used to measure nitrogen self‐diffusion coefficients in UN. Temperatures were 1700° to 2000°C and N2 pressures 7 to 603 torr. The diffusion coefficients were in fair agreement with those obtained by the gaseous exchange method in an independent study. No fundamental significance was attached to the activation energy because UN is nonstoichiometric under these conditions, and the relation between composition and N2 pressure is unknown. The results are compatible with nitrogen interstitial diffusion.
Infrared Kinetic Study of High‐Temperature Reactions of Synthetic Kaolinite
Authors: MACKENZIE K. J. D.
Published: June 2006

An infrared frequency shift method was used to follow the kinetics of conversion of dehydroxylated synthetic kaolinite to mullite. Comparison of the kinetic and activation thermodynamic data for natural and synthetic kaolinite suggests that the mechanism of high‐temperature reaction is similar, although the activation energy of synthetic kaolinite is larger than that of natural kaolinite because of the lack of nucleation‐promoting impurity cations in the former. The high‐temperature ir data indicate that there is little or no difference in the cation coordination of the phases intermediate to metakaolinite and mullite, but that the principal high‐temperature coordination change (probably the accommodation of aluminum in well‐defined tetrahedral sites) occurs during the later stages of mullite formation.
Strengthening of Class Fibers: 11, Ion Exchange *
Authors: COOPER A. R. , KROHN D. A.
Published: June 2006

Soda‐alumina‐silica glass fibers were ion‐exchanged in potassium nitrate at 400°C; their strength was measured before and after exchange. The potassium concentration distribution and the optical retardation were also measured. The results for unetched fibers are consistent with the premise that the kinetics of exchange are controlled by diffusion with D⋍×10−11 cm2/s) and with the predictions of thermal stress analysis with a dilation coefficient of 2.8×10−4 (wt fraction potassium)−1. The existence of a broad maximum in the plot of strengthening of unetched fibers vs time may be explained by the existence of Griffith flaws about 2 μm deep in the unexchanged glass. A deleterious effect from ion exchange was noted with etched fibers, in which even a short (½ h) exchange caused significant weakening.
Color Centers and Point Defects in Irradiated Thoria
Authors: CHILDS B. G. , HARVEY P. J. , HALLETT J. B.
Published: June 2006

The optical absorbance of commercially pure thoria single crystals was measured after oxidizing and reducing treatments, irradiation by 18‐MeV protons, 48‐MeV 16O ions, and 60Co gamma photons, and thermal annealing at temperatures up to 950° C. For unirradiated specimens, absorption bands previously observed at 2.80, 3.03, and 4.03 eV were confirmed, and additional bands were identified at 1.67, 2.04, 2.45, 3.61, and 4.52 eV. Reduction and irradiation enhanced the 3.03 and 3.61 eV bands but diminished the 2.80, 4.03, and 4.52 eV bands. The centers responsible for the two groups of bands are thus presumed to be electron‐type and hole‐type, respectively. Impurity atoms, also, are probably involved in the centers. Ion irradiation produced an intense blue color in the exposed volume of the specimens, and additional absorption bands appeared at 1.49, 1.80, 2.03, and 2.32 eV. The behavior of these bands on annealing and on subsequent low‐exposure gamma irradiation indicated that the corresponding centers are combinations of impurity atoms and oxygen interstitials.
Effect of Dopants on the Defect Structure of Single‐Crystal Aluminum Oxide
Authors: RASMUSSEN J. J. , KINGERY W. D.
Published: June 2006

Density and lattice parameter changes induced by dopants were studied in Czochralski rubies containing from 0.054 to 0.160 wt% Cr2O3, in Czochralski sapphires containing from 0.083 to 0.120 wt% TiO2, and in verneuil crystals grown from powders containing 250 to 1000 ppm Ca, Mg, Si, and V. Densities were determined within at least ∼0.005% using a hydrostatic weighing technique; lattice parameter shifts were measured within a maximum of 0.25% using a step‐scanning goniometer technique. Some crystals which appeared to be clear, transparent, and single‐phase contained fine particles of a second phase. It is concluded that Si4+ and Ti4+ ions enter solution with the formation of cation vacancies to maintain charge neutrality, that verneuil crystals contain vanadium as V3+, that the solid solubility of Ca2+ is low (<340 ppm), and that MgO decomposes under verneuil growth conditions, resulting in formation of a second phase.
Stacking Faults in Chemically‐Vapor‐Deposited Beta Silicon Carbide
Authors: GULDEN T. D.
Published: June 2006

A high density of planar defects, often forming closed figures on {111} planes, was observed in chemically‐vapor‐deposited β‐SiC. The defects were identified as extrinsic stacking faults by electron diffraction contrast analysis.
Through Pore Size Distribution and Kinetics of the Carbonation Reaction of Portland Cement Mortars
Authors: DAIMON MASAKI , AKIBA TOKUJI , KONDO RENICHI
Published: June 2006

Through pores of hardened cement mortars were studied by gas transfer experiments. The permeabilities were the same for N2 and H2. The pore size distribution of through pores was examined by back diffusion; the method was simplified by combining H2 and N2 gases. The permeability calculated from these results agreed with the experimental values of N2 and H2. The neutralization rate of hardened cement was expressed as L2=kθ(t‐ti). The rate of neutralization was determined by the gas diffusion of both CO2 and H2O.