bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Temperature on the Charge on KaoIinite Particles in Water
Authors: BUTTON D. D. , LAWRENCE W. O.
Published: June 2006

An electrophoretic technique was used to determine the variation of charge on a kaolinite particle as a function of temperature. A monodies‐persed fraction of kaolinite was treated with various amounts of sodium hydroxide. The pH, conductivity, and electrophoretic mobility of the clay were determined as functions of temperature. From this information the charge on the particles and an energy related to the energy of adsorption
Phase Equilibria in the Spinel Region of the System FeO‐Fe2O3‐Al2O3
Authors: ROITER B. D.
Published: June 2006

Phase relations in the spinel region of the system FeO‐Fe2O3‐Al2O3 were determined in CO2 at 1300°, 1400°, and 15000°C and for partial oxygen pressures of 4 × 10−7 and 7 × 10−10 atmospheres at 15OO°C. The spinel field extends continuously from Fe3O4‐x to FeAl2O4+z.
Elastic Properties of Some Glasses After Neutron Irradiation
Authors: PAYMAL ANDRÉ J. , Le CLERC PIERRE
Published: June 2006

The changes in Young's modulus brought about in various glasses by exposure to irradiation in a nuclear reactor are reported. These changes are a function of glass composition and particularly of the alkali content. The proposed interpretation of the changes observed at low doses is based on comparisons with the temperature ratio of Young's modulus and consideration is given to both a “hot” structural configuration and a rearrangement in cation sites. The changes observed at higher doses are explained by an increase in the specific gravity due to compaction and those at very high doses by tempering.
Electrical Conduction Anomaly of Semiconducting Glasses in the System As—Te—I
Authors: EATON D. L.
Published: June 2006

The transformation from one resistance state to another by glasses in the system As‐Te‐I is discussed and a model is postulated. The anomalous behavior of the electrical properties of glasses in this system is shown to result from thermal breakdown of the dielectric during which reversible glass‐to‐crystal phase transformation occurs. Results of compositional studies and the measurement of the electrical characteristics of resistivity, Seebeck coefficients, and current‐voltage curves are given. Resistivities of 103 to > 107 ohm‐cm and Seebeck coefficients of +800 to ±4300μv per OC were measured for glasses in this system.
Phase Separation in Borosilicate Glasses
Authors: CHARLES R. J.
Published: June 2006

Dielectric measurements and direct‐transmission electron microscopy were used to analyze the phase separation and alteration in sodium borosilicate glasses. Metal impregnation of the glasses after leaching was particularly useful in observing the topology of separated phases whose characteristic dimensions are about 100 A. The results indicate that borosilicate glasses such as Vycor and Pyrex are fully phase separated when rapidly cooled from the melt and that subsequent heat treatment serves only to alter the structural characteristics of the separated phases. The topological characteristics of the initially segregated phases suggest that phase separation may occur by spinodal decomposition.
Color Centers in X‐Irradiated Soda‐Silica Glasses
Authors: SMITH HERBERT L. , COHEN ALVIN J.
Published: June 2006

The coloration produced by X‐irradiation in silicate glasses prepared under oxidizing and reducing conditions was studied. These glasses differed both in the position of the absorption maximums and in the thermal stability of the color centers formed. Maximums were observed at 4.10, 2.70, and 1.96 ev in oxidized glasses and at 2.15 ev in reduced glasses. Additions of a wide variety of cations to the basic glasses modified the coloration produced by X‐irradiation. These modifications appeared as new centers or in the enhancement or reduction of coloration produced by X‐irradiation in the base glasses. The reduction of ions such as Ce4+, Eu3+, and Yb3+ by X‐irradiation is observed. Although several of the color centers appeared to be associated with the glass network itself, there was some correlation between the added cations and the coloration of the glass by X‐irradiation.
Subsolidus Relations in the System SiO2— Al2O3— P2O5
Authors: ROBINSON P. , McCARTNEY ERIC R.
Published: June 2006

Phase relations in that part of the system SiO2‐Al2O5‐P2O6 below 50 mole % P2O3 were investigated at subsolidus temperatures. The only ternary compositions which crystallized readily were those lying close to binary compounds and no evidence for ternary compound formation was found. Solid solution between silica and aluminum phosphate, expected on the basis of closely similar lattice dimensions and physical properties, was not indicated by X‐ray diffraction, refractive index, or electron‐beam microprobe results. Above 80% silica and at a temperature of 1400°C, the only crystalline species was cristobalite whereas below 60% silica, only the cristobalite form of AlPO4 was present. Coexistence of these two constituents seemed to be inhibited, possibly because of the strong glass‐forming properties of the component oxides.
Release of Xenon from Uranium Carbide at Low Temperatures
Authors: AUSKERN ALLAN
Published: June 2006

The release of xenon from lightly irradiated uranium monocarbide powders was studied in the temperature range 150° to 975°C. Release in this range is much higher than that calculated by extrapolating high‐temperature diffusion data. The kinetics of the release agree with a model in which the xenon in the first three or four unit cells is released over a range of activation energies.
Thermal Expansion Measurements on Thoria and Hafnia to 4500°F
Authors: OHNYSTY BASIL , ROSE F. K.
Published: June 2006

Equipment for measuring thermal expansion to 4500°F is described. Linear thermal expansion to 4500°F was measured on thoria and hafnia. Average coefficient of linear expansion from 75° to 4500°F for thoria was 6.05 x 10‐3perOF; for stabilized hafnia with 10 wt% Y2O3 additions it was 6.33 × 10−6 per OF, and with 15 wt% Y2O3 additions it was 6.27 × 10−6 per °F.
Solid Solutions in Antiferroelectric Region of the System PbHfO3‐PbTiO3‐PbSnO3‐PbNO2O6
Authors: HALL C. A. , DUNGAN R. H. , STARK A. H.
Published: June 2006

Dielectric, ferroelectric, and piezoelectric properties were investigated for compositions in the high‐lead hafnate region of the system PbHfO3‐PbTiO3‐PbSnO3‐PbNO2O6. Phase diagrams were prepared that show the existence of a ferroelectric‐to‐antiferroelectric phase transition with increasing temperature. Five phases were shown to exist in the portion of the system investigated two ferroelectric phases, two antiferroelectric phases, and one paraelectric phase. Ferroelectric‐antiferroelectric phase transitions induced by temperature, electric field, and pressure were investigated. The highest spontaneous polarization measured was approximately 25 μcoul per cm2.
Phase Relations in the System Uranium—Nitrogen
Authors: BUGL J. , BAUER A. A.
Published: June 2006

To supplement efforts to develop UN as a nuclear fuel material, a study of the phase relations in the system uranium‐nitrogen was conducted. The decomposition behavior and melting point of UN was studied in a controlled nitrogen‐pressure apparatus in which cast specimens of UN were heated and observed. UN decomposed at pressures of nitrogen below 2.5 atm at temperatures below 2850° C and melted congruently at 2850° C and pressures of 2.5 atm or greater. The nitrogen content of the liquid uranium phase in equilibrium with UN was determined by heating uranium in a UN crucible and then quenching and analyzing the equilibrated phase. The solubility of nitrogen in atomic percent can be expressed as S = 2.45 × 104 exp (‐38,800/RT) for temperatures in OK. Studies in the region U2N3‐UN2 of the system which were performed using a Sievert‐type apparatus showed that although these compounds are structurally dissimilar, they form a series of continuous solid solutions. Only UN2 formed at high pressures and low temperatures. A pressure‐temperature schematic diagram and a temperature‐composition schematic diagram for a nitrogen pressure of 1 atm for the system uranium‐nitrogen are presented. At this pressure, UN decomposed at 2800° C and U2N3 decomposed at 1345° C.
Preparation and Thermal Analysis of Mixed Magnesium‐Manganese‐Iron Oxalates and Hydrated Oxides
Authors: GALLAGHER P. K. , SCHREY FRANK
Published: June 2006

A square‐loop ferrite composition, Mg0.675Mn0.535–Fe1.8000O4, having high purity and fine particle size was prepared by pyrolysis of coprecipitated oxalates or hydrated oxides. The control of pH had a marked effect on the stoichiometry of the coprecipitated divalent oxalates, and ap optimum pH of 2.5 to 3.0 was observed. Thermal analysis was performed on the coprecipitated materials and on individual components; it revealed that the coprecipitated oxalates formed a solid solution whereas the hydrated oxides did not.
Properties and Structure of Glasses in the Binary Systems Alkali—TiO2
Authors: RAO Bh. V. JANAKIRAMA
Published: June 2006

Glasses corresponding to mole formulas R2TiO3 and R2Ti2O5 were prepared in 1‐ to 5‐g quantities by quenching in a platinum crucible. K2O, Rb2O, and Cs2O formed fairly stable glasses with TiO2. On heat treatment, these glasses nucleated readily and formed opal‐like glasses. Li2O and Na2O, however, did not form glasses with TiO2 in 1‐g quantities. Hygroscopicity increased with the alkali content and decreased with the increase in TiO2 concentration. The refractive indices of the glasses ranged from 1.66 to 1.90. These facts indicate that TiO2 is a glass former in its own right and that Ti4+ exists in sixfold coordination in these glasses.
Conductivity Discontinuity in a Two‐Phase System
Authors: GREKILA R. B. , TIEN T. Y.
Published: June 2006

A geometric model is presented to describe the electrical conductivity in a two‐phase system. In the case treated the grains are of equal size and shape and the conductivity changes primarily with changing numbers of contacts between grains of the phase with higher conductivity. A test of the validity of the model was made by application to the two‐phase region (from 22 to 50 mole % CaO) of the system ZrO2–CaO.
Thermal Conductivity of Sintered UO, and Al2O3 at High Temperatures
Authors: NISHIJIMA TORAJI , KAWADA TOSHIYUKI , ISHIHATA AKIRA
Published: June 2006

The thermal conductivities of sintered Al2O3 and UO2 were measured in the ranges 400° to 1700°C and 300° to 2100°C respectively. The conductivity values for Al2O3 agreed with those reported previously at all temperatures investigated. The conductivity of UO, decreased with increasing temperature to a minimum of 0.0050 cal per cm sec °C at about 1400°C, and then increased with increasing temperature to 0.0105 cal per cm sec °C at 2100°C.
Growth of Large Optical‐Quality Yttrium and Rare‐Earth Aluminum Garnets
Authors: VAN UITERT L. G. , GRODKIEWICZ W. H. , DEARBORN E. F.
Published: June 2006

An improved flux consisting of PbO‐PbF2 and B2O3 was developed for the growth of garnets. Rare‐earth aluminum garnet crystals weighing in excess of 100 g and modified yttrium aluminum garnet crystals weighing up to 60 g were obtained using this flux. Lead contamination was reduced to noncritical levels in these crystals by working with large excesses of A12O3 in the melt. Excellent optical quality has been produced as indicated both by visual examination and by outstanding laser performance.
Effect of Porosity on Compressibility of Glass
Authors: WALSH J. B. , BRACE W. F. , ENGLAND A. W.
Published: June 2006

An expression derived for the compressibility of glass foams is the same as Mackenzie's expression for a body containing a low concentration of spherical pores, when carried to the limit of very high porosity. Simple analysis shows that Mackenzie's expression is also valid for slightly nonspherical pores but should underestimate the actual compressibility for porosities which are neither high nor low. Compressibility measured on a series of porous glass samples to 70% porosity agree closely with the theoretical relation, except at intermediate porosities, where the departure shows the predicted effect of pore interaction.
Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3—PbTiO3—PbZrO3 Solid Solution Ceramics
Authors: OUCHI HIROMU , NAGANO KATSUO , HAYAKAWA SHIGERU
Published: June 2006

Ceramic and electrical properties and crystal structures of the system Pb(Mgl/3Nb2/3‐ PbTiO3‐PbZrO3 are described. The system is composed of three crystal phases at room temperature: pseudocubic, tetragonal, and rhombohedral. A high dielectric constant and radial coupling coefficient and low resonant resistance were obtained for the compositions near the morphotropic transformation. The composition Pb(Mgl/3Nb2/3)0.4375Ti0.4375Zr0.125O3 had the lowest temperature coefficient of resonant frequency.
Crystalline Solution in the System MgO‐Mg,SiO4,‐MgAl2,O4,
Authors: SCHLAUDT CHARLES M. , ROY DELLA M.
Published: June 2006

Crystalline solubility relations in the system MgO‐Mg2SiO4MgAl2O4 (periclase‐forsterite‐spinel) were studied using coprecipitated gels as starting materials. The substitution 2Al = Mg + Si was investigated along the join Mg2SiO4‐Mg‐Al2O4,. At 1720°C the maximum crystalline solution in forsterite is about 0.5 mole % MgAI2O4, and in spinel it is slightly more than 5.0 mole % Mg2SiO4. The solubility of MgO in forsterite was 0.5 mole % at 1860°C, whereas more than 11 mole % Mg2SiO4 can be dissolved in the periclase structure at this temperature. Ternary crystalline solution exists in the periclase structure to a composition of Mg0.853Al0.063Si0.026O at 1710°C.
Kinetics of the Anatase‐Rutile Transformation
Authors: SHANNON ROBERT D. , PASK JOSEPH A.
Published: June 2006

Transformation of three commercial anatase powders resulted in sigmoid curves of transformation vs. time, which were interpreted in terms of a nucleation‐growth process. Analysis of these curves by several rate laws led to activation energies for nucleation of 109, 136, and 148 kcal/mole and for growth of 100, 115, and 190 kcal/mole, respectively. The rate of transformation and activation energy are governed by the nature and amount of impurities which determine the defect structure of the TiO2, i.e. the concentration of oxygen vacancies or interstitials. It is suggested that, in general, oxygen vacancies accelerate and the interstitials inhibit the transformation. CuO additions and hydrogen atmospheres accelerated the transformation by the introduction of oxygen vacancies and/or by reduction to a second TinO2n−1Magnéli phase which could act as a nucleating agent. The transformation is retarded in vacuum; this retardation is attributed to the introduction of titanium interstitials.
The System MgO‐ZnO‐SiO2
Authors: SEGNIT E. R. , HOLLAND A. E.
Published: June 2006

The system MgO‐ZnO‐Sio2 was studied by the quenching technique. No ternary compounds were found in the system, but extensive solid solution relations occurred in the magnesiumand zinc‐bearing compounds. Two ternary eutectics and one reaction point were located; the minimum melting point in the system was 1370°± 5°C at a composition of 15.5 wt% MgO, 37.0 wt% ZnO, and 47.5 wt% SiO2.
Interdiffusion of Calcium in Soda‐Lime‐Silica Glass at 880° to 1308°C
Authors: SUCOV EUGENE W. , GORMAN ROBERT R.
Published: June 2006

The interdiffusion of calcium in soda‐lime‐silica glass under the action of a concentration gradient was studied. Pairs of glass blocks differing by 2.9 mole % in CaO content were fused together to form diffusion couples and were held at 880° to 1308°C. The couples were allowed to cool to room temperature and the diffusion which had taken place was measured by optical interferometry and by an electron microprobe. The diffusion coefficients varied from 4.4 × 10−10cm2/sec at 880°C to 8.0 × 10−8 cm2/sec at 1308°C. The activation energy was 42,000 cal/mole. It is concluded that oxygen diffuses simultaneously with the calcium, maintaining the electrical neutrality of the glass.
Nucleation and Growth of Lead Titanate from a Glass
Authors: Bergeron C. G. , Russell C. K.
Published: June 2006

The temperature dependence of the rate of growth of PbTiO2 crystals from a PbO‐B2O3‐TiO2 glass was experimentally determined. The Brown‐Ginell equation describing the temperature dependence of the growth rate provided an excellent fit for the data. The activation energy for the growth of PbTiO3 crystals was 34 kcal per mole. Within the same temperature range the activation energy for viscous flow was 75 kcal per mole. Differential thermal analyses of both powdered and solid samples of glass showed that the exotherm associated with crystal growth occurred at 100° to 150°C below that of the maximum rate of crystal growth and corresponded to a temperature at which the rate of surface nucleation was relatively high although the rate of crystal growth was low.
Initial Sintering of BaTiO3 Compacts
Authors: Anderson Harlan U.
Published: June 2006

Experimental measurements were made of the rate of initial shrinkage of high‐purity BaTiO3 compacts in air. The time dependence of the shrinkage rate was consistent with a model based on grain boundary vacancy diffusion. The apparent activation energy for the shrinkage rate in the range 700° to 1000°C is 112 ± 9 kcal per mole. Comparison with other data indicates that oxygen ion vacancy diffusion controls the initial sintering rate.
Oxidation Behavior of Uranium Monophosphide
Authors: Baskin Y.
Published: June 2006

Oxidation of UP at moderate temperatures was studied using DTA, X‐ray diffraction, TGA, and chemical analysis. Heating rates, atmosphere, and particle size were varied. Oxidation behavior of UP was significantly different from that of UC, UN, US, and UAs, all of which possess the NaCl‐type crystal structure. The greater oxidation resistance of UP was attributed to surface formation of an amorphous phase containing P2O5 and UO2. Existence of this coating was thought to be responsible for the nontarnishing and generally nonpyrophoric nature of UP at room temperature.
Role of “Adherence Oxides” in the Development of Chemical Bonding at Glass‐Metal Interfaces
Authors: BOROM MARCUS P. , PASK JOSEPH A.
Published: June 2006

Chemical bonding, a requirement for adherence, is developed at glass‐metal interfaces by achieving and maintaining equilibrium compositions at the interfaces. Reactions between iron and glasses with and without “adherence oxides” were studied by thermogravimetry, optical microscopy, and electron probe microanalysis. Adherence oxides result in the formation of alloys at the interface that tend to maintain equilibrium with the adjoining glass over an extended time and enhance atmospheric oxidation of the metal. The occurrence of dendrites in the bulk glass and the function of a “nickel flash” in porcelain enameling are discussed in terms of these reactions.
Thermal‐Mechanical History and the Strength of Magnesium Oxide Single Crystals: II, Etch Pit and Electron Transmission Studies
Authors: STOKES R. J.
Published: June 2006

Mechanical tests show that the room‐temperature flow strength of magnesia single crystals varies with heat treatment. Flow strength depends on the size, density, and distribution of precipitate particles which inhibit the motion of dislocations. The present paper describes optical and electron transmission microscope evidence for a precipitation reaction in magnesium oxide. The observations correlate fairly well with mechanical test data. Mechanical tests also show that mobile dislocations are locked by heating above 600°C. The room‐temperature yield strength increases with time and temperature particularly when the aging temperature exceeds 1000°C. Studies to determine the nature of this locking mechanism are described. Etch pit studies show that dislocations aged above 600°C etch at a slower rate than fresh dislocations. This corresponds precisely with the change in mechanical behavior and both effects are attributed to impurity diffusion to dislocation lines. Electron transmission studies indicate a redistribution of point defects, left by moving dislocations, above 600°C. Eventually these result in a change in dislocation configuration which is considered responsible for the strong locking observed above 1000°C.
Ionic Conductivity in Calcium Silicate Glasses
Authors: SCHWARTZ MICHAEL , MACKENZIE J. D.
Published: June 2006

Glasses in the system CaO–SiO2 were prepared with the composition varying from 40 to 55 mole % CaO. The Na2O impurity content ranged from 0.01 to 1.30 mole %. The electrical resistivity was insensitive to the Na2O content but decreased with increasing CaO concentration. The activation energy for conduction ranged from 33.54 to 31.23 kcal/mole as the CaO concentration increased. The conduction mechanism was considered in terms of three arbitrary parameters: (1) equivalent oxygen packing density, (2) ionic radius, and (3) ion‐oxygen attraction.
Strengthening of Glass Surfaces by Sulfur Trioxide Treatment
Authors: MOCHEL ELLEN L. , NORDBERG MARTIN E. , ELMER THOMAS H.
Published: June 2006

Removal of soda from a glass surface at high temperature can, on cooling, give appreciable strengthening due to lowering of the expansion coefficient at the surface. Soda depletion has been accomplished previously by treating a high‐expansion soda‐lime glass with SO2 in the presence of oxygen and water. The depletion rate can be doubled by using dispersed platinum to catalyze the oxidation of SO2 to SO3 before the gas reacts with soda from the glass. The data are consistent with the soda depletion being Fickian both with and without the catalyst. Alumina in the glass composition markedly increases the strength which can be attained by sulfur oxide treatment. Although the percentage of soda retained in the leached layer increases, the total amount of soda removed from the glass also increases as alumina increases. It must follow that the depth of the layer is increased.
Infrared Spectra of GeO2‐P4O10‐V2O5 Glasses and Their Relation to Structure and Electronic Conduction
Authors: JANAKIRAMA‐RAO BH. V.
Published: June 2006

Infrared spectra of binary and ternary compositions in the glassy state and in the devitrified crystalline state in the system GeO2‐P4O10‐V2O5 were studied and compared with infrared spectra of crystalline spinels, which are known to contain V5+ ions in sixfold coordination. Results indicated that the fundamental vibration frequency of the V—O bond occurred at wave number 1015 cm−1. The spectra also provided evidence that the V5+ ion existed in sixfold coordination in the glassy state, as well as in the devitrified crystalline state, and that the VO6 octahedron retained its identity even at low concentrations and melting temperatures of 1450°C. Conductivity measurements indicated that, as the concentration of V2O5 decreased below the critical range of 5 to 10 mole %, there was an abrupt loss in the electronic conductivity of the glasses; the conductivity decreased with increasing concentration of the lower valence states of vanadium. A mechanism of conduction compatible with the structure of glasses in the system is suggested to explain these observations.
Mechanical Properties of Chemically Strengthened Glasses at High Temperatures
Authors: KERPER M. J. , SCUDERI T. G.
Published: June 2006

Young's modulus, shear modulus, and modulus of rapture for two chemically strengthened glasses were determined at high temperatures. The Young's modulus and shear modulus decreased with increasing temperature, with a sharp inflection slightly above room temperature. The region of inflection indicated an internal friction peak. For comparison Young's modulus and shear modulus were determined as a function of temperature on a thermally tempered soda‐lime‐silica glass and on a semitempered borosilicate glass. Curves of these moduli, in contrast to those for the chemically strengthened glasses, did not reveal regions of inflection. The modulus of rupture is not affected by short exposure to heat up to 260°C., but decreases appreciably when exposed to temperatures above 204°C for 200 hr or more. Deflection measurements at room temperature showed that the two chemically strengthened glasses had about five times as much delayed elasticity as did thermally tempered soda‐lime‐silica glass.
Subsolidus Equilibria in the System MgO–GeO2–MgF2
Authors: McCORMICK GEORGE ROBERT
Published: June 2006

Four MgO‐GeO2‐MgF2 compounds, analogous to the humite minerals, were synthesized by solid state reaction by substituting germanium for silicon. The 43 selected compositions were sintered at 800° to 1200°C. Solid state compatibility relations were established from petrographic and X‐ray diffraction analyses. The optical properties and characteristic X‐ray diffraction data for the four MgO‐GeO2‐MgF2 compounds were determined, and 2MgO.GeO2 MgF2, 4MgO.2GeO2 MgF2, and 6MgO.3GeO2 MgF2 were indexed by Ito's method.
Thermal Decomposition of Brucite: I, Electron and Optical Microscope Studies
Authors: GORDON RONALD S. , KINGERY W. D.
Published: June 2006

The decomposition of brucite was studied directly in electron and optical microscopes. A small amount of decomposition caused marked changes in the physical state of the brucite crystal. The decomposition was interpreted as a normal nucleation and growth process in which magnesium oxide nuclei formed coherently with the brucite matrix. This process accounts for: (a) the structural relations between parent and product phases, (b) the small crystallite size of the product, (c) the cracking process occurring in the initial stages of decomposition, and (d) the range of d spacings observed for the magnesium oxide formed during the decomposition.
Hydrothermally Grown ZnO Crystals of Low and Intermediate Resistivity
Authors: KOLB E. D. , LAUDISE R. A.
Published: June 2006

Single crystals of zinc oxide in the resistivity range 101 to 1010 ohm‐cm were prepared by hydrothermal crystallization using controlled lithium doping. Lithium concentration in the crystals ranged from 0.4 to 6 × 1018 atoms/cm3 when the LiOH concentration in the hydrothermal growth solutions ranged from 0 to 2.0 molal. The logarithm of the resistivity is nearly linear with the lithium concentration of the grown crystal. Calculations of apparent mobility show that either the donor concentration is a function of the lithium concentration during growth or not all the lithium in the grown crystals acts as acceptors. Crystals with resistivities as low as 10−2 ohm‐cm were prepared by doping with indium which acts as a donor. Crystals were grown in solutions containing NH4++ LiOH. The NH4+ had a negligible effect on resistivity but it markedly increased the rate of crystallization on the (1010) (prism) face. A study of the occasionally produced anomalous crystals grown in silver‐lined autoclaves showed that resistivity anomalies were not due to silver‐doping of the grown crystals.
Thermal Shock Resistance of Zirconia with 15 Mole % Titanium
Authors: ARIAS ALAN
Published: June 2006

The thermal shock resistance of zirconia with 15 mole % titanium prepared either by cold‐pressing and vacuum‐sintering or by vacuum hot‐pressing was determined by radially quenching disks with thermally insulated faces under various conditions of heat transfer. The thermal shock resistance of calcia‐stabilized zirconia disks was determined for comparison. For quenches from below the transformation temperature range of zirconia, the thermal shock resistance of zirconia with 15 mole % titanium was much better than that of calcia‐stabilized zirconia, but for quenches from above the transformation range it was slightly inferior. The thermal shock resistance of zirconia with 15 mole % titanium is fairly insensitive to the methods of manufacture used in this investigation. In an attempt to identify the physical properties responsible for the improved thermal shock resistance of zirconia with 15 mole % titanium, the heat capacity, thermal expansion, modulus of rupture, modulus of elasticity, and thermal conductivity as functions of temperature were determined.
Mechanism by Which Metal Additions Improve the Thermal Shock Resistance of Zirconia
Authors: ARIAS ALAN
Published: June 2006

The relatively good thermal shock resistance of zirconia with 15 mole % titanium for quenches from below the transformation temperature of zirconia is attributed to the metal in the grain boundaries. The discrepancy between calculated and experimental thermal shock resistance of the same compositions for quenches through the transformation range is traced to the plastic behavior of these materials through the transformation range. The same type of plasticity was observed through the transformation range of zirconia‐zirconium compositions. Metals other than titanium also improved the thermal shock resistance of zirconia.
Born Model Calculation of Enthalpies of Solution in CaF2
Authors: FRANKLIN A. D.
Published: June 2006

The Born model of ionic solids was used to calculate the lattice energy, as an estimate of the enthalpy of solution, needed to dissolve NaF and YF3 in CaF2, in the limit of infinite dilution. For NaF sufficient experimental data are available to provide reasonable estimates for the parameters describing the repulsive interactions between Na+ and surrounding ions, and the calculated enthalpy of solution is in good agreement with the available experimental value, 1.4 ± 0.3 ev for NaF. For YF3 the experimental data are not available and the estimated enthalpy of solution of about zero is subject to a large uncertainty. The results for NaF are consistent with the model normally assumed, in which each substitutional Na+ ion is accompanied by an F− vacancy; however, they do not rule out charge compensation by interstitial Na+ ions. The calculations also yield an estimate for the lattice expansion.
Equilibrium Nitrogen Pressures and Thermodynamic Properties of UN
Authors: INOUYE H. , LEITNAKER J. M.
Published: June 2006

Pressures of nitrogen over UN(s) + U(1) were measured between 1300′ and 1500°C. These data, coupled with literature data, extend the measured range of pressures to nearly 11 orders of magnitude and 1550 centigrade degrees. The best value of AH°298, UN from the available data is taken to be ‐69.6 +1.0 kcal/mole. The second and third law calculations agree satisfactorily.
Adsorption of Admixtures on Portland Cement Hydration Products
Authors: ROSSINGTON D. R. , RUNK ELLEN J.
Published: June 2006

The adsorption of calcium lignosulfonate and salicylic acid was studied on the hydration products of the four principal components of portland cement. To investigate the adsorption as a function of development of hydration product, the determinations were made after varying hydration times. The times allowed were from 5 min to 24 hr for tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF) and from 1 hr to 28 days for β‐dicalcium silicate (β‐C2S) and tricalcium silicate (C3S). Samples were characterized with respect to surface area and poresize distribution. The effect of gypsum on the adsorption was also investigated. The results indicate that the amounts of salicylic acid and calcium lignosulfonate adsorbed on the hydration products of C3A, and of calcium
Effects of Irradiation on Beryllia‐Based Fuels
Authors: HICKMAN B. S. , ROTSEY W. B. , HILDITCH R. J. , VEEVERS K.
Published: June 2006

Dispersions of (UTh)O2 in beryllia containing 1.7 to 25 vole%, (UTh)02 in coarse (150 to 200P), medium (33 to 35P), and fine (<10 and <5μ) fuel particle sizes were irradiated to burnups of 3 to 10% of heavy metal atoms between 300’and 900°C, in both fast and thermal fluxes. Changes in volume, lattice parameter, line breadth, and modulus of rupture were measured; volume changes in the fine dispersions were ascribed wholly to fission fragment damage and were about 50% greater than those caused by fast neutrons alone; they increased with increasing fission fragment flux, and decreased as irradiation temperature increased. Volume changes in medium and coarse dispersions were about 25% greater than those caused by fast neutrons alone; the increased damage is attributed to the additional β‐flux. As fuel particle size increased, deterioration in strength under irradiation was more marked. This was attributed to more intense fission fragment damage in the recoil zone around larger particles causing volume increases which exceeded those of the remainder of the matrix. For maximum initial strength and retention of strength under irradiation, the fuel particle size should not exceed 5β, and the interparticle spacing should not exceed 30μ.
Melting Point of Cryolite
Authors: FOSTER PERRY A.
Published: June 2006

The melting point of ultimate‐purity cryolite was determined by evaluating the liquid fraction r of selected natural mineral samples over the melting range. A plot of the reciprocal of the liquid fraction l/r, as a function of the temperature T from which samples were quenched, gave a straight line that indicates a melting point for the sample of 1009.2°C at l/r= 1 and extrapolates to a value of 1012° f 2°C at l/r= 0 for pure cryolite.
Dielectric Properties and Phase Transitions of Sodium‐Strontium‐Cadmium Niobates
Authors: TENNERY VICTOR J.
Published: June 2006

Solid solution was observed in the system Na1‐xSrN CdPNbO3 where N + P = x/2 between ≤ x 0.40 when the ratio of N:P was within the limits 1:2 → 2:1. Solid solution was observed at N:P ratios outside these limits but these materials were not studied extensively. A ferroelectric pseudomonoclinic perovskite phase was observed at 25° C when ≤ x & le; 0.10 in the compositional series studied. At higher values of x a ferroelectric pseudotetragonal phase with c/a 1 appeared between the pseudomonoclinic ferroelectric phase and the para‐electric pseudocubic phase which was stable at high temperatures. The pseudotetragonal phase, which exhibited much larger values of €/€0 than the pseudomonoclinic phase, had a large peak in the electrical permittivity when it transformed to the pseudocubic state. The high‐temperature phase observed in these materials became a small‐cell perovskite structure when the subcell edge length attained 3.942 ± 0.002 A as a result of thermal expansion.
Dorn Method in the Study of Initial Phase of Uranium Dioxide Sintering
Authors: BACMANN J. J. , CIZERON G.
Published: June 2006

The Dorn method, most commonly used to measure the activation energy of creep, was used to study the initial stage of sintering uranium dioxide in hydrogen from 700° to 850°C. The activation energy was approximately 100 kcal/mole. This result agrees with the value determined from analysis of isothermal shrinkage curves in the same temperature interval.
High‐Temperature Cermets: I, Compatibility
Authors: MANNING CHARLES R. , STOOPS ROBERT F.
Published: June 2006

The stability of refractory oxides (Y2O3,‐stabilized HfO2 and ZrO2, Tho2, CeO2), carbides (HfC, NbC, TaC, and ZrC), borides (NbB2 and TaB2), and HfN was determined in combination with the Groups VIA and VIIA refractory metals and combinations thereof. Thermodynamic calculations were made to predict stability up to 2500°K between the ceramic oxides and carbides in contact with Mo, Re, and W. Reaction studies were conducted between the ceramics and the Groups VIA and VIIA refractory metals in vacuum and in helium to 2750°C. The Mo‐40 wt% Re, Re, and W were stable in contact with the carbides, nitrides, and oxides to 2450°C with two exceptions. These occurred when CeO2 reacted with W at 1700°C and Mo‐40 wt% Re reacted with WC. The Mo‐40 wt% Re and Re also reacted with the NbB2 and TaBa above 2200°C to form very hard single‐phase compounds.
Deposition and Microstructure of Vapor‐Deposited Silicon Carbide
Authors: GULDEN T. D.
Published: June 2006

Vapor deposition of Sic from methyltrichlorosilane in a fluidized bed and the microstructure of the deposit were studied over a range of deposition temperatures, carrier gas flow rates, and reactant fluxes. The rate‐determining factor for the deposition of Sic was the rate of supply of reactant. The microstructure of vapor‐deposited Sic was primarily dependent on the deposition temperature; however, carrier gas flow rate and reactant flux had a secondary influence on microstructure. At low temperatures and high carrier gas flow rates, laminar deposits containing excess silicon were produced. At higher temperatures and lower carrier gas flow rates deposits were characterized by faulted columnar grains. The grain diameter increased from about LP at 1400°C to about 15 μ at 1800°C. The grain size also increased, but less markedly, with increasing reactant flux. The deposits characterized by columnar grains were predominantly β‐Sic with traces of a‐SiC and excess carbon.
Prediction of the Elastic Moduli of Composites
Authors: ROSSI R. C.
Published: June 2006

The description of the elastic behavior of composite materials by mathematical expressions presently in the literature is restricted by the microstructural models on which they were based. An extension has been made to one of these expressions in which the shape of the included phase is considered as well as the moduli of the individual phases. The results allow a more general application of the theoretical expressions to composite materials in which the included phase is contained at low concentrations.
X‐Ray Measurement of Strain in Quartz Particles of Whiteware Bodies
Authors: CUCKA PAUL , OLIVA R. F.
Published: June 2006

Work on internal stresses in whitewares caused by differential thermal expansion of the crystalline and vitreous components is reviewed briefly. Thermoelastic strains in the quartz of four whiteware bodies containing mono‐disperse quartz particles 2 to 4, 6 to 9, 20 to 27, and 44 to 54p in diameter, respectively, at concentrations of approximately 20 wt% were measured by X‐ray diffraction. A high‐temperature technique, involving measurement of dllo, d110, d201, and d211 spacings at 25° and 650° C using Mo Kα, Cu Kα, and Fe Kα radiations, and a room‐temperature technique using these radiations plus Cr Kα gave consistent results in agreement with theoretical predictions of the effect of nonuniformity of stress in particles near the sample surface. Strain determinations on powdered samples and changes in line shapes with temperature indicate that the measured strains were due to thermoelastic stress. The measured stresses were 4200 kg/cm2 parallel to the quartz c axis and 5700 kg/cm2 parallel to the quartz a axis. The stresses in the body containing the largest particle size quartz may be somewhat lower because of the formation of cracks.
Silica Transformations in the System PbO‐SiO2
Authors: NEGAS TAKI , SORRELL CHARLES A.
Published: June 2006

Mixtures of PbO and silicic acid were fired at 710°, 820°, and 910°C for periods up to 1000 hr in air. At each temperature cristobalite and tridymite crystallized rapidly, with the greatest development in samples with compositions of 1 mole PbO to 50 and 60 moles SO2. At 820° and 91O°C tridymite continued to crystallize at the expense of cristobalite. At 710°C quartz formed, after a nucleation time of approximately 200 hr, at the expense of cristobalite and tridymite. The equilibrium assemblages were cristobalite and tridymite at 820° and 910°C and quartz and PbSiO2 at 710°C. The results are interpreted in terms of the tentative phase relations outlined by Holmquist for the high‐silica regions of binary silicate systems. Phase development curves and lattice parameter measurements characterize the initially formed cristobalite as a metastable solid solution containing approximately 2 mole % PbO. Equilibrium was approached by exsolution of PbO from the cristobalite structure.
Thermal Expansion of Synthetic β‐Spodumene and β‐Spodumene—Silica Solid Solutions
Authors: OSTERTAG W. , FISCHER G. R. , WILLIAMS J. P.
Published: June 2006

Synthetic β‐Spodumene and several β‐Spodumene‐silica solid solutions were prepared, and their thermal expansion behavior was studied using high‐temperature X‐ray diffraction techniques. Data indicate that all β‐Spodumenes are characterized by a pronounced anisotropy of thermal expansion much the same as that of the silica polymorph keatite. Anisotropy increases slightly and the volume expansion decreases as the compositions become richer in SiO2. Specimens with more than 80.8 wt% SiO2 at 130O°C and 1 atm contain P‐cristobalite along with β‐Spodumene. The lattice parameters of β‐Spodumene compositions throughout the solid solution range were determined. The structural aspects of the anisotropy of thermal expansion are discussed.
Studies in Germanium Oxide Systems: IV, Phase Equilibria in the System K,O‐GeO,
Authors: MURTHY M. K. , LONG L. , IP J.
Published: June 2006

Phase relations in the binary system K2O‐GeO2 were determined by conventional quenching techniques. Three compounds, K2O.2GeO2, 3K2O.11GeO2, and K2O.7GeO2, exist in the composition range 65 to 100% GeOn. The compound 3K2O.1lGeO2 melts congruently at 1055°C, whereas K2O.2GeO2 and K2O.7GeO2 melt incongruently at 761° and 950°C, respectively. Thermal expansion data for the crystalline compounds are presented. The structure of potassium germanate glasses is discussed.
Constitution of Ternary Ta‐Mo‐C Alloys
Authors: RUDY ERWIN , BRUKL C. E. , WINDISCH STEPHAN
Published: June 2006

The ternary system Ta‐Mo‐C was investigated by X‐ray, melting point, DTA, and metallographic methods on chemically and thermally characterized specimens; a phase diagram for temperatures from 1500°C through the melting range was established. At high temperatures, the cubic monocarbides, TaC and αMOc1‐x, as well as the hexagonal subcarbides, Ta2C and Mo2C3 form continuous series of solid solutions. Below 1960°C, the homogeneity range of the β phase is temperature‐dependent. At 2230°C, the ternary subcarbide solid solution disproportionates into metal and monocarbide alloys. The sub‐lattice order‐disorder transformation temperatures in both subcarbides are lowered by the mutual exchange. The ternary range of the η‐MoC1‐x, phase is very restricted, and the metastable ζ‐Ta‐C phase is stabilized in the ternary. Seven isothermal reactions occur in the system in the range from melting to 1500°C; two further isotherms between 1400° and 1500°C are indicated to result from the order‐disorder transition in Mo2C. Using existing literature data for the thermodynamic properties of the binary carbides, the phase relations in the Ta‐Mo‐C system were thermodynamically analyzed. The calculated equilibria are in good agreement with experimental observations.
Structural Characteristics of Liquid Mixtures of Feldspar and Silica
Authors: FLOOD Silica H. , KNAPP W. J.
Published: June 2006

Thermodynamic properties of liquid mixtures of feldspar and silica were considered in attempting to interpret them in terms of melt structure. Two sources of data were used: the heats of formation and free energies of formation of the crystalline and glassy compounds, and the published phase diagrams. The systems albite‐silica, orthoclase‐silica, and anorthite‐silica were studied, and some data from the system celsian‐silica were included. A model which assumes a random distribution of AlO4 tetrahedra and SiO4, tetrahedra is generally applicable to silica‐rich liquid mixtures of albite‐silica and orthoclase‐silica. For mixtures of albite‐silica, it is suggested that minor amounts of polymeric aluminosilicate units are also present. In liquid mixtures of anorthite and silica, however, it is necessary to assume that polymeric units like 4AlO2.3SiO2 or 4AlO2.2SiO2, are the dominating feature of the structure.
Grain Boundary Energies in NaCl in the Rigid Lattice Approximation
Authors: GIBBON C. F.
Published: June 2006

Grain boundary energies are computed for twist boundaries in NaCl with the assumption that there is no relaxation of the lattice at the boundary. The energy is 573 ergs/cm2 and is independent of angle over the range studied. Comparison is made with recent experimental results for twist boundaries in KCl.
Phase Separation in the System BaO‐SiO2
Authors: SEWARD T. P. , UHLMANN D. R. , TURNBULL DAVID
Published: June 2006

A simple, rapid‐quenching device was used to investigate the extent of liquid‐liquid immiscibility in the system BaO‐SiO2. A metastable miscibility gap was found with an upper consolute point at about 10 mole % BaO and 146OOC. Bulk glass samples of different compositions and heat treatments were examined by direct‐transmission electron microscopy to determine the phase separation morphology. At low BaO contents the separation was characterized by spherical barium‐rich particles in a silica‐rich matrix. For compositions near the center of the gap, the structure consisted of two phases continuously interconnected throughout the bulk of the glass. At higher BaO contents, spherical silica‐rich particles were found in a barium‐rich matrix. The dependence of the morphology on quench rate and heat treatment was investigated. Predictions of other authors concerning the occurrence of BaO‐SiO2 immiscibility are compared with the present results.
Fusion and Vaporization Characteristics of ZrTe3O8
Authors: SORRELL CHARLES A.
Published: June 2006

The only intermediate phase stable in air in the system ZrO2−TeO2 is ZrTe3O8 with a cubic, distorted, fluorite‐type structure. The compound melts congruently at 1014°± 5°C to an unstable liquid. Vaporization occurs, with loss of TeO2, at high temperatures with an activation energy of 64 kcal per mole of ZrTe3O8. No glass formation was observed in the system.
Residual Stress and Grain Deformation in Extruded Polyerystalline BeO Ceramics
Authors: SMITH DEANE K. , WEISSMANN SIGMUND
Published: June 2006

Residual strain measurements on a series of sintered BeO tubes indicate that significant stresses developed during processing from the thermal expansion anisotropy. X‐ray topographic studies show that the resulting strains are preferentially located near grain and subgrain boundaries. Fine‐grained samples, 20μ and less, do not show pronounced subgrain structure and exhibit lower dislocation densities in the grain interiors than do coarse‐grained samples.
Formation of Active Carbon in Twin‐Crucible Studies of Vanadium Carbonitride Solutions
Authors: SPEAR KARL E. , LEITNAKER JAMES M.
Published: June 2006

Twin‐crucible experiments with vanadium carbonitride solutions in equilibrium with carbon and nitrogen gas gave evidence for the formation of carbon in a state more energetic than graphite. These studies show that the V(C, N) lattice parameter depends on whether the starting material was vanadium carbide or a mixture of vanadium nitride and graphite. The postulate that a high‐energy form of carbon may result from any decomposition or reaction leading to free carbon is discussed relative to metal carbide evaporation and to the decomposition of uranium dicarbide to the sesquicarbide and carbon.
Alkali Strontium‐Barium‐Lead Niobate Systems with a Tungsten Bronze Structure: Crystallographic Properties and Curie Points
Authors: GIESS E. A. , SCOTT B. A. , BURNS G. , O'KANE D. F. , SEGMÜLLER A.
Published: June 2006

Crystallographic parameters, Curie points, and freezing temperatures are presented for a series of A+A22+Nb5O15 compositions with tungsten bronze‐related structures, where A+=Na, K, or Rb, and A2+=Sr or Ba. Results are also reported for bronze solid solutions in the systems KNbO3‐PbNb2O6, K(Sr‐Ba)2Nb5O15, K(Ba‐Pb)2Nb5O15, K(Sr‐Pb)2Nb5O15, and (KSr2‐K2La)Nb5O15. On the basis of these data, an empirical relation is shown between the ferroelectric transition temperature, Tc, and axial ratio °10 co/a0. The Tc vs °10 c0/a0 curve for compositions with polar axes perpendicular to [00l] has a negative slope, whereas that for compositions with polar axes parallel to [00l] has a positive slope of about the same magnitude. These results are compared with measurements of the temperature dependence of c0/a0 for KSrPbNb5O15, and KBa2Nb5O15; the latter is discussed in terms of the Devonshire free energy theory.
Phase Relations in the System Li2O.B2O3‐B2O3‐NiO
Authors: BERKES JOHN S. , WHITE† WILLIAM B.
Published: June 2006

Phase equilibria were determined by standard quench methods in binary systems NIO‐B2O3, the binary join Li2O.B2O3‐NiO, and three other sections through the Li2O.B2O3‐B2O3‐NiO system. The only new compound observed was 2NiO.B2O3, which is stable from 1303° to 1480°C.