bluuebunny/crossref_metadata_2025 huggingface dataset:
Fundamentals of Glass‐to‐Metal Bonding: VII, Wettability of Iron by Molten Sodium Silicate Containing Iron Oxide
Authors: ADAMS ROBERT B. , PASK JOSEPH A.
Published: June 2006

Contact angles, and adherence of sodium disilicate glasses with varying iron oxide additions on platinum and iron were studied at 1000°C. in vacuum. In the glass‐platinum systems the iron concentration in the glass did not affect either the contact angle or the adherence. No devitrification occurred in the glass‐platinum systems. The glass‐iron systems showed a lowering of the contact angle with increasing iron content in the glass, ranging exponentially from 55° to approximately 22°. Adherence was poor with no iron in the glass, and it increased as the iron content and reaction at the interface increased. Crystals, identified as fayalite (Fe2SiO4), were observed in some of the glass drops from the glass‐iron systems. Polished cross sections of the glass‐iron assemblies showed a greater attack of the metal surface as the iron content in the glass increased. The configuration suggests greater attack along the grain boundaries.
Preparation and Properties of Spinel Made by Vapor Transport and Diffusion in the System MgO‐Al2O3
Authors: NAVIAS LOUIS
Published: June 2006

In a hydrogen atmosphere, MgO was vaporized by heating MgO (periclase) in the range 1500° to 1900° C, and the vapor products diffused into Al2O3 (sapphire) to form a uniform outer layer of spinel on all surfaces. At 1900°C. a spinel layer 48 mils thick could be obtained in 16 hours. The rates of spinel formation were determined and the activation energy was calculated to be about 100 kcal. per mole. In the spinel layer, the lattice constant, Vickers hardness, and the refractive index varied from the outer surface to the inner boundary in a fairly uniform manner, indicating a continuous change in composition from 1MgO: 1Al2O3 to 1MgO: 2–3Al2O3. In conversion to spinel a volume increase of 47% over that of the original sapphire took place. Transparent clear shapes of spinel such as disks and rods were obtained from clear sapphire and from translucent polycrystalline alumina. Clear rods of spinel with polished ends acted as thin lenses, round rods as convex lenses, and flat rods as planocylindrical lenses owing to the increase in refractive index from the outer surface to the inner central portion. Objects made of opaque polycrystalline alumina were also converted to spinel. The MgO periclase blocks were etched in the hydrogen atmosphere, and the vapor products of Al2O3 entered the MgO to form tiny spinel droplets in an opalescent border. In an oxidizing atmosphere, spinel was formed only on the surface of the sapphire directly in contact with periclase, in the range 1500° to 1900°C.
Correlation of Strength of Glass with Fracture Flaws of Measured Size
Authors: SHAND ERROL B.
Published: June 2006

The purpose of this study was to develop a method of producing a single small crack on a glass surface which would become the initiating flaw in the fracture process. Techniques for measuring dimensions of this flaw also formed an essential part of the study. The cracks were formed by pressing a wedge‐shaped tungsten carbide point against the glass. Measurements were made from visible patterns found on the fracture surface after the glass was broken. Strict adherence to carefully worked out procedures was found to be essential for obtaining satisfactory cleaved cracks. Based on fracture caused by a semicircular crack 0.002 in. deep, the 1‐second breaking stresses of five different glasses were as follows: lead‐alkali glass 6800, soda‐lime glass 9000, 96% silica glass 11,500, low‐expansion borosilicate glass 12,000, and aluminosilicate glass 13,800 lb. per sq. in. These values are believed to correlate with the intrinsic strengths of the glasses. This method should have definite advantages in the investigation of fracture phenomena in glasses and in other brittle materials, specifically the effects of composition on strength and the causes of stress fatigue
Crystalline Thorium Borate
Authors: BASKIN Y. , HARADA Y. , HANDWERK J. H.
Published: June 2006

Crystalline thorium borate (ThB2O5) has been synthesized by the reaction of thoria with boric oxide at elevated temperatures; crystals of size suitable for single‐crystal X‐ray studies were grown in molten boric oxide at 1300°C. Crystallographic, chemical, and some physical properties of thorium borate crystals are presented as well as the results of a preliminary phase study of the system ThO2‐B2O3. Amorphous thorium borate gel, formed by reaction of aqueous solutions of borax and thorium nitrate, is transformed into crystalline thorium borate and thoria on firing at elevated temperatures. Boric oxide does not appear to react with either zirconium oxide or uranium dioxide to form any crystalline compounds. The fact that uranium dioxide does not react with boric oxide, but thoria does, affords a basis for effecting a chemical separation of the two oxides from thoria‐urania solid solutions. Preliminary data on the reactions between boric oxide and different thoria‐urania solid solutions are given.
Stability of Refractories in Hydrogen‐Fluorine Flames
Authors: EBNER M.
Published: June 2006

The flame resistance of six refractories of commercial purity was measured in the well‐mixed stoichiometric portion and in the unmixed fluorine‐rich portion of a hydrogen‐fluorine diffusion flame. Graphite, silicon carbide, zircon, alumina, zirconia, and magnesia are decreasingly resistant to the test flame in the order indicated. The rate of ablation is about three times more rapid and the average surface temperatures are 130° to 745° C. higher where the flame is fluorine‐rich. Graphite and silicon carbide are suggested for use in HF flames because of their good thermal‐shock resistance and relative chemical inertness to the flame. Consideration of the ablation chemistry indicates that zircon dissociates and then, like graphite, silicon carbide, and zirconia, ablates by flame‐solid reaction, whereas alumina and magnesia form liquids which flow from the impingement area.
Fracture Velocity and Fracture Energy of Glass in the Fatigue Range
Authors: SHAND ERROL B.
Published: June 2006

A method is developed for determining crack velocities from the stress‐time curve of fracture. Velocities of glass broken in air and in vacuum converge at a value between 1 and 10 mm. per second. This convergence is considered to be the upper limit of the fatigue range. Fracture energy has been computed in terms of strain energy release rates. For glass broken in air under low stresses this energy is about equal to the surface energy of the glass, but when in vacuum it is fifteen times greater. At the upper limit of the fatigue range it is thirty times greater, whereas at the terminal velocity of fracture it is of the order of fifty times greater. It is concluded that surface energy must constitute only a small part of the energy absorbed in the fracture process. This excess energy has a pronounced influence on the fracture process and on the measured strength of glass.
Sintering of Oxide and Carbide‐Metal Compositions in Presence of a Liquid Phase
Authors: KINGERY W. D. , NIKI E. , NARASIMHAN M. D.
Published: June 2006

Observations of microstructure changes in several systems and the rate of densification during sintering of magnesium oxide, titanium carbide, and tungsten carbide in the presence of a liquid phase indicate that the densification rate is controlled by diffusion through a liquid film between particles. Dependence of the sintering rate on time, particle size, and temperature are in agreement with predictions. Theoretical estimations of the sintering rate are in reasonable agreement with experimental measurements.
A Study of Basic Brick from Copper Anode Furnaces
Authors: RIGBY G. R. , HAMILTON B.
Published: June 2006

Samples of basic and alumina brick were examined after service in copper anode furnaces. Copper oxides penetrating the brick had reacted with the chrome grains, with the periclase, and with the alumina. These reactions were studied by examining the stability of the compounds formed when copper oxides were heated with various spinels and oxides. In general, spinels of the series CuO R2O3 decomposed to the compound CU2O R2O3 with the liberation of R2O3, when R was Al3+, Cr3+, or Fe3+. With magnesia, cupric oxide formed the mineral güggenit, CuO–MgO, which during heating decomposed with the evolution of oxygen to MgO and Cu2O.
Microwave Properties of Polycrystalline Hybrid Garnets
Authors: HARRISON GORDON R. , HODGES L. R.
Published: June 2006

The microwave properties of a number of polycrystalline mixed garnets have been studied. The compositions investigated included solid solutions of yttrium iron garnet with gadolinium iron, samarium iron, yttrium aluminum, yttrium gallium, and yttrium chromium garnets. Ball‐mill mixing techniques were employed in specimen preparation. Line width, saturation magnetization, and effective g‐factor measurements were made as a function of composition and temperature for all specimens studied. Curie temperatures were also measured for each specimen. The merits of using these garnet compositions for microwave component applications are amplified by the fact that some of their properties may be independently controlled. Data on temperature compensation and high‐power effects are presented as well as a discussion of the applicability of these materials to microwave solid‐state devices.
Studies in the System Li2O–Al2O3–Fe2O3‐H2O
Authors: STRICKLER D. W. , ROY RUSTUM
Published: June 2006

Subsolidus equilibrium relations in a portion of the system Li2O‐Fe2O3‐Al2O3 in the temperature range 500° to 1400°C. have been determined near po2= 0.21. Of particular interest in this system is the LiFe5O8‐LiAl5O8 join, which shows complete solid solution above 1180°C. Below this temperature the solid solution exsolves into two spinel phases. At 600°C. approximately 15 mole % of each compound is soluble in the other. The high‐temperature solid solution and the low‐temperature exsolution dome extend into the ternary system from the 1:5 join. There is no appreciable crystalline solubility of LiFeO2 or of α‐Fe2O3 in LiFe5O8. An attempt to confirm HFe5O8 as the correct formulation of the magnetic ferric oxide “γ‐Fe2O3” was inconclusive, but in the absence of positive evidence, the retention of γ‐Fe2O3 is recommended. All the metallic oxides of the Group IV elements increase the temperature of the monotropic conversion of ‐γ‐Fe2O3 to α‐Fe2O3. Silica and thoria have a greater effect on this conversion than does titania or zirconia.
Decomposition of Higher Oxides of Chromium Under Various Pressures of Oxygen
Authors: KUBOTA BUICHI
Published: June 2006

The formation of Cr3O8, Cr2O5, CrO2, and Cr2O3 by the decomposition of anhydrous CrO3 under a high oxygen pressure and their physical and chemical properties are presented. The crystal structure of CrO2 is a rutile type and its lattice constants do not vary with the ratio O/Cr. The specific gravity of CrO2 decreases with an increase in the ratio O/Cr. This is explained by assuming that the crystal structure of CrO2 contains an excess of Cr ions at interstitial sites. This crystal model is supported by the low electrical resistivity of CrO2. An electron microscopic examination showed an abnormal grain growth of CrO2 during the decomposition of Cr2O5 to CrO2. The activation energies of the decomposition of Cr2O5 and CrO2 to Cr2O3 in air are 61.7 and 48.2 kcal. per mole, respectively. The pressure‐temperature diagram of various chromium oxides has been determined. From the pressure‐temperature curve of CrO2‐Cr2O3 the heat of decomposition is found to be 26.3 kcal. per mole.
Sintering Behavior of Beryllium Oxide
Authors: FELTEN E. J.
Published: June 2006

The sintering behavior of beryllia in a reducing atmosphere was studied between 1500° and 2100°C. Above 1700°C. the firing temperature had only a small effect on the density after heating for 24 hours. Examination of the time dependence of sintering showed that at 1700°C. during the first 3 to 5 hours there was a large increase in the density of the body accompanied by a simultaneous rapid rate of grain growth. Firing for longer times resulted in more moderate increases in both density and grain growth. The grain‐growth characteristics of beryllia were unchanged by most oxide additions although compacts of higher density resulted. Oxide additives which formed a liquid phase at the sintering temperature enhanced both the sinterability and grain growth of beryllia.
Gamma Irradiation Studies of Some Borate Glasses
Authors: BISHAY ADLI
Published: June 2006

The gamma‐ray‐induced optical absorption in a series of cabal (calcium‐boron‐aluminum) glasses was studied and is interpreted, wherever possible, in terms of structural concepts. A resolution of the observed absorption spectra showed that three Gaussian‐shaped bands were induced with their maxima at about 2.3, 3.5, and 5.0 e.v. (550, 350, and 250 mμ). The 2.3‐e.v. band decreased in intensity with increasing CaO content, reaching a minimum intensity at a composition corresponding to the four‐coordination of about 20% of the boron. Further increase in CaO content was associated with an increase in the intensity of this band. The intensity of the 3.5‐e.v. band decreased gradually with increased mole per cent of CaO and increased with increased Al2O3. The 5.0‐e.v. band showed an abrupt increase in intensity which corresponded to the appearance of non‐bridging oxygens in the network. Replacing Ca2+ by Mg2+, Sr2+, or Ba2+ or replacing Li+ by Na+ or K+ showed that glasses containing large ions of low field strength give less induced absorption than glasses containing small ions of high field strength. A potassium alumina borate glass melted under reducing conditions gave a considerably higher ultraviolet transmission, before irradiation, as compared with the same glass melted under normal conditions. The gamma‐induced absorption of these two glasses showed that reducing conditions resulted in a decrease in the intensity of the 2.3‐ and 3.5‐e.v. bands, whereas it caused an increase in the far‐ultraviolet‐induced absorption. The effect of additions of arsenic, thallium, titanium, germanium, and some rare‐earth oxides is discussed.
Heat‐Conductivity Processes in Glass
Authors: KINGERY W. D.
Published: June 2006

Two main processes account for heat conduction in glass. At low temperatures the major process corresponds to energy transfer via thermoelastic waves. The thermal conductivity resulting from this process is low as a result of strong scattering by the random structure. At high temperatures this conduction process is overshadowed by radiation heat‐transfer processes.
A Review of Radiant Heat Transfer in Glass
Authors: GARDON ROBERT
Published: June 2006

This review is aimed at a nonmathematical elucidation of the physical phenomena underlying radiant heat transfer in glass. In transparent materials, unlike the more familiar opaque materials, the emission and absorption of radiation are bulk, rather than surface, phenomena. Interaction of the simultaneous emission and absorption of radiation throughout the volume leads to a dependence of the emissivity of transparent bodies on their thickness. The interaction also leads to a mechanism of radiative heat transfer in the interior of transparent materials entailing not the familiar radiation through them but internal radiant exchanges between nearby layers. The analogy of this mechanism with thermal conduction has led to the definition of an equivalent ‘radiative conductivity.” The origin and limitations of this concept are briefly discussed, together with conditions at the boundaries of transparent bodies and applications to unsteady‐state processes.
Spectral Transmission of Glass at High Temperatures and Its Application to Heat‐Transfer Problems
Authors: GROVE F. J.
Published: June 2006

The variation of absorption coefficient with wave length and temperature has been measured for a number of glasses containing iron oxide and chromium oxide. From these results, an effective mean free path F has been calculated, in which all the information on the variation of absorption coefficient, at a given temperature, is compounded. This value of F then has been used to calculate the coefficient of radiation conductivity Kr. It has been shown that there is a correlation between the mean free path F and the iron oxide content of soda‐lime‐silica glasses. Examples are given of the method of estimating furnace bottom temperatures and temperature gradients through a mass of glass.
Temperature Measurement of Glass by Radiation Analysis
Authors: VAN LAETHEM R. , LEGER L. , BOFFÉ M. , PLUMAT E.
Published: June 2006

In a previous work, the possibility of determining the general aspect of the vertical temperature distribution of a glass layer from analysis of both total and spectral emitted brilliancy was shown. The theoretical analysis has been developed further in the present paper. A numerical and graphical calculation method, devised by Czerny and Walther, is used. The analytical solution of the brilliancy integrals is also discussed. If the conditions for analytical integration are realized and if the vertical temperature distribution is assumed to follow a linear or quadratic law, this distribution can be calculated on the basis of a few radiation measurements. One measurement was made in the region beyond 4.2 μ the others were made in various spectral regions ranging from 0 to 4.2 μ to which associated values of the glass absorption coefficient correspond, according to the temperature. Close agreement was obtained between measured and calculated temperatures.
Temperature Distribution and Heat Flow in Glass in Blank Molds of Container Machines
Authors: TRIER W.
Published: June 2006

A new method is described that helps to determine the temperature distribution of glass in blank molds. The effective coefficient of thermal conductivity, the heat flow within the glass, and the proportions of radiation and conduction may all be deduced from temperature profiles depending on the duration of contact between the glass and the mold. The results obtained lead to deductions as to the mechanism of heat transfer between glass and mold surfaces.
Properties of Soda Aluminosilicate Glasses: I, Refractive Index, Density, Molar Refractivity, and Infrared Absorption Spectra
Authors: DAY DELBERT E. , RINDONE GUY E.
Published: June 2006

The density, refractive index, molar refractivity, and infrared absorption spectra of soda aluminosilicate glasses containing up to 34.8 wt% alumina have been determined. Changes in these properties with composition can be explained by existing theories which assume that the aluminum ions form only A104 tetrahedra when the Al/Na ratio of the glass is equal to or less than 1. The aluminum ions in glasses having an Al/Na ratio larger than 1 are in both fourfold and sixfold coordination.
Crystal Chemistry of Mixed Bismuth Oxides with Layer‐Type Structure
Authors: SUBBARAO E. C.
Published: June 2006

Several compounds with m= 2, 3, 4, and 5 in the general formula (Me2′O2)2+ (Mem–1 RmO3m+1)2– were synthesized, a number of them for the first time. They possess a layer‐type crystal structure. Bi3+ may be the only suitable ion for the Me′ sites; R may be Gas+, Ti4+, Nb5+, or Ta5+. The restrictions on the size of Me ions increases with increasing value of m. Lattice parameter data for the compounds and indexed X‐ray powder patterns for m= 5 compounds are presented.
Mechanical Properties and Chemical Reactivity in Mullite—Glass Systems
Authors: STUDT PERRY L. , FULRATH RICHARD M.
Published: June 2006

Mullite‐glass systems were studied by vacuum hot‐pressing sized mullite crystal particles with known glass compositions. During the hot‐pressing at relatively low temperatures, significant chemical reactivity was observed between mullite and a soda borosilicate glass. This reaction led to the precipitation of a silica‐rich crystalline phase in the glass matrix and to a change in the mullite structure as evidenced by the X‐ray diffraction pattern. Wetting studies at elevated temperatures indicated an interfacial chemical reaction. The modulus of rupture increased when the second crystalline phase was present. Increased volume fraction of the crystalline phase and development of a stronger interfacial bond between mullite and glass may be the primary factors responsible for the increase in mechanical strength.
New Statistical Treatment of Ball Indentation Data to Determine Distribution of Flaws in Glass
Authors: SUCOV EUGENE W.
Published: June 2006

Ring fractures generated by a steel ball indenting a flat glass plate occur outside the contact circumference, not at the circumference as theory predicts. It has been proposed by others, and is accepted as a basis for the present work, that the position of ring fracture is not determined by the locus of maximum stress but by the presence of a flaw which is severe enough to initiate fracture under the local condition of stress. The ring fracture radii thus locate flaws of various sizes at various distances from the center of contact. A new statistical method is introduced for calculating the distribution of such flaws with respect to both sizes of flaw and surface density of flaws. Application of this analysis to data taken from indentations of HF‐etched surfaces shows that flaw densities range from 15 to 30 per mm2per 5 A depth interval (150 to 300 flaws per mm2over the range detected by the indenter). Since continued removal of the surface did not change this density distribution, it is concluded that these flaws are due to inhomogeneities in the glass structure rather than to surface flaws which are accidental in origin. The limitation of the strength of flat glass to 300,000 psi is due to these inhomogeneities.
The Binary System Nb2O5— SiO2
Authors: IBRAHIM M. , BRIGHT NORMAN F. H.
Published: June 2006

The binary system Nb2O5— SiO2 has been shown to include an extensive two‐liquid region over the range 5 to 80% Nb2O5. The minimum temperature of the two‐liquid area is 1695°C. A eutectic composition occurs at 95% Nb2O5 and 1448°C. and another at approximately 5% Nb2O5 and 1695°C. The experimental results were obtained by the cone‐fusion method.
Revised Phase Diagram for the System Al2O3—SiO2
Authors: ARAMAKI SHIGEO , ROY RUSTUM
Published: June 2006

On the basis of 190 runs made up to 1860°C in sealed noble‐metal containers the following revisions have been made in the equilibrium diagram for the system A12O3–SiO2. Mullite melts congruently at 1850°C. The extent of equilibrium solid solution in mullite at solidus temperature is from approximately 60 mole % Al2O3 (3/2 ratio) to 63 mole % A12O3. Metastable solid solutions can be prepared up to about 67 mole % Al2O3. There is no evidence for stable solubility of excess SiO2 beyond the 3/2 composition at pressures below 3 kbars. Refractive indices are presented for glasses containing up to 60 mole % Al2O3 and from them the composition of the eutectic is confirmed at 5 mole % SiO2. The variation in lattice constants of the mullite solid solution is not an unequivocal guide to composition since mullites at one composition produced at different temperatures show differences in spacing, no doubt reflecting Al‐Si ordering phenomena. The possibility of quartz and corundum being the stable assemblage at some low temperatures and pressures cannot be ruled out. A new anhydrous phase in the system is described, which was previously thought to be synthetic andalusite; it is probably a new polymorph of the Al2SiO5 composition with ortho‐rhombic unit‐cell dimensions a=7.55 A, b=8.27 A, and c= 5.66 A.
Calcination and Sintering Study of Thoria
Authors: HARADA Y. , BASKIN Y. , HANDWERK J. H.
Published: June 2006

Data on the effect of calcination temperature on surface area, apparent crystallite size, compactibility, sintered density, and volume shrinkage are presented for thoria prepared from the oxy‐carbonate, chloride, nitrate, and oxalate. Surface area and volume shrinkage decreased with rising calcination temperature. Thoria obtained from the oxycarbonate exhibited the greatest sinterability; material derived from the nitrate showed the least. Maximum bulk densities were achieved using material resulting from the calcination of the oxycarbonate between 600° and 100°C. Densities of 95 to 98% of the theoretical value of thoria were attained by compacting these powders at pressures above 20 tsi and firing at 1500°C for 24 hours. Urania‐thoria solid solutions incorporating thoria obtained by calcination of the chloride exhibited the highest fired densities.
Stability of Solid Phases in the Ternary Systems of Silicon and Carbon with Rhenium and the Six Platinum Metals
Authors: SEARCY ALAN W. , FINNIE LIES N.
Published: June 2006

Possible reactions in the ternary systems of carbon and silicon with rhenium, ruthenium, rhodium, osmium, and iridium have been studied at 1600°, 1340°, 1170°, 1350°, and 1340°C, respectively. At these temperatures the only stable phases are solid metal silicides and silicon carbide. Approximate ternary diagrams are fixed for the systems carbon‐silicon‐palladium and carbon‐silicon‐platinum by examination of phases formed during cooling from above the liquidus temperatures. Lower limits to the thermodynamic stability of many of the metal silicides are set by the stability of these phases relative to reaction with carbon to form silicon carbide. Higher limits to the stability of the other metal silicides are set by their instability relative to reaction with carbon to form silicon carbide. These limits are used to estimate heats of formation for the platinum‐family metal silicides. Measured and estimated heats of formation of other transition metal silicides are tabulated.
Phase Relations and Structures in the System PbO–Fe2O3
Authors: MOUNTVALA A. J. , RAVITZ S. F.
Published: June 2006

A detailed study of the system PbO‐Fe2O3, largely by X‐ray diffraction analysis, has been made. The results indicate the existence of three intermediate phases: (1) a phase (beta) extending from PbO·5Fe2O3 to PbO·6Fe2O3, (2) a phase (gamma) extending from PbO ‐ 2Fe2O3 to PbO ‐21/2Fe2O3, and (3) a phase (delta) 2PbO·– Fe2O3. Structures are proposed for the beta and gamma phases that explain their solubility limits, magnetic properties, and very great similarity in structure and in lattice dimensions.
Gamma‐Ray‐Induced Coloration in Solids; Application to Glass Systems
Authors: CROPPER WILLIAM H.
Published: June 2006

General aspects of radiation‐induced coloration in solids are discussed. It is considered that the most significant initial effect of the radiation is to produce free electrons and trapped holes in a track. The decay of the track from the initial condition is described in some detail, assuming (a) that the rate of diffusion of electrons from the track is small compared with the rates of other processes and (b) that primary processes which form color centers can be considered to be independent of secondary processes which cause destruction of color centers. A method of calculation is described which gives the concentration of color centers formed at various doses. With plausible assumptions for the parameters, agreement with the data of Schulman et al. on a silver phosphate glass is obtained. The treatment of glasses less simple than the silver phosphate glass is also discussed.
The Binary System CaO–Nb2O5
Authors: IBRAHIM MOHAMMAD , BRIGHT NORMAN F. H. , ROWLAND JOHN F.
Published: June 2006

The binary system CaO‐Nb2O5 has been shown to include three compounds: CaO·Nb2O5, which melts congruently at 1560°C; 2CaO·Nb2O5, which melts congruently at 1576°C; and 3CaO·‐Nb2O5, which melts incongruently at 1560°C. Three eutectic compositions occur at 6% CaO (1362°C), 23% CaO (1492°C), and 34% CaO (1535°C). These results were obtained by the cone‐fusion technique. The compound 3CaO‐Nb2O5 has been shown to exist in two forms: type I, face‐centered cubic with a = 7.978 A, having a superlattice with a = 23.934 A, and type II, orthorhombic (pseudotetragonal, distorted cubic) with a = 11.51 A, b = 11.10 A, c = 15.98 A, having a pseudocell with a = 5.754 A, b = 5.551 A, and c = 7.990 A. The conditions controlling the formation of these two forms were not determinable from the experiments conducted.
Synthesis of Calcium Titanate Single Crystals by Flame Fusion Technique
Authors: MERKER LEON
Published: June 2006

A technique has been developed for growing un‐fractured calcium titanate boules up to 25 mm long and 12 mm in diameter by flame fusion. Large untwinned sin.gle crystals have been prepared from which optical properties, density, hardness, dielectric constant, and melting point have been determined.
Formation of Cubic ZrO2 with Transition Metals of Groups V and VI and Their Oxides
Authors: HOCH MICHAEL , MATHUR MOOL‐RAJ
Published: June 2006

Cubic ZrO2 can be formed at 1500°C from tetragonal ZrO2 and transition metals of groups V and VI or their monoxides only in the presence of TiO2. The 1500° isotherm of the pseudo‐ternary system ZrO2‐TiO2‐VO was investigated and the extent of the single‐phase cubic ZrO2 region was determined. In the system Ta‐Ta2O5 the lower oxides cannot be formed by reacting Ta and Ta2O5 between 1450° and 1815°C.
Acid‐Base Equilibria in the System PbO–SiO2
Authors: FLOOD H. , KNAPP W. J.
Published: June 2006

The acid‐base equilibria in the liquid silicates in the system PbO–SiO2 are discussed, Data reported by Richardson and Webb, wherein the PbO activity is determined over a composition range of 0 to 60 mole % SiO2, are used for comparison with activities computed from structural models with consideration of the acid‐base equilibria. The results suggest that the liquid silicates in the system PbO–SiO2, for the composition and temperature ranges studied, are constituted of a relatively low number of anionic species and that these anions are of a relatively small size (i.e., O2–, SiO4–, (SiO3)36−. and (SiO2.5)66−).
Isomorphous Substitution for Silicon in Fluorphlogopite
Authors: SCHATZ ELIHU A.
Published: June 2006

Attempts to substitute for silicon in the fluorphlogopite structure resulted in the synthesis of a fluorgermanium mica and a boron phosphate micalike orthorhombic crystal. The batch material contained Al2O3, MgO, MgF2, K2CO3, plus GeO2 for forming the fluorgermanium mica and BPO4 for forming the boron phosphate crystal. Optical analysis with a polarizing microscope and by X‐ray diffraction verified the mica structure of the germanium crystal and disproved the mica structure of the boron phosphate crystal. The indices of refraction and unit‐cell constants were determined for both crystals. A study of the electrical properties up to temperatures of 1000°F showed that the dielectric properties of the fluorgermanium mica were very similar to that of fluorphlogopite.
End‐Point Density of Hot‐Pressed Alumina
Authors: McCLELLAND J. D. , ZEHMS E. H.
Published: June 2006

Hot‐pressed aluminum oxide has been found to exhibit an asymptotic end‐point density. The temperature and pressure dependence of this end‐point density has been investigated over the range of temperature from 1100° to 1500°C and pressure from 500 to 6000 psi. The pressure dependence of the end‐point density can be explained in terms of a plastic‐flow model which exhibits a critical shear stress. The temperature dependence suggests that this critical shear stress is a thermally activated process with an activation energy of 39 kcal per mole.
Phase Studies on Arc‐Melted Plutonium‐Carbon Alloys Near the Monocarbide Composition
Authors: KRUGER OWN L.
Published: June 2006

The phase boundaries and structure of plutonium monocarbide were studied in arc‐melted alloys containing between 42 and 60 at.% carbon. Metallographic and X‐ray diffraction techniques were used to determine the phases present in as‐cast and heat‐treated alloys. The phase boundaries of cast PuC were found to be about 42.5 at.% carbon on the low‐carbon side to between 48.5 and 50 at.% carbon on its high‐carbon side. At 1000° and 400°C the low‐carbon compositions of about 45.5 and 46 at.% carbon, respectively. A comparison of the experimental densities with the theoretical densities showed that PuC was a defect structure with some of its carbon atom lattice sites vacated.
Low‐Temperature Sintering of Uranium Dioxide
Authors: FUHRMAN N. , HOWER L. D. , HOLDEN R. B.
Published: June 2006

Studies of the fabrication of uranium oxide fuel pellets by the low‐temperature sintering of nonstoichiometric oxide are described. Completer reversion to stoichiometric UO2 in the sintered pellets was attained by two methods: (1) Sintering in a nitrogen atmosphere which contained a small amount of hydrogen and (2) sintering in pure nitrogen and then exposing the pellets to hydrogen at the sintering temperature. Large variations in sinterability were found in commercially procured ceramic‐grade UO2 powder. In studying these variations, it was discovered that fluorine was a powerful inhibitor of low‐temperature sintering. This impurity could be readily removed by oxidation in air at 500°C. The data strongly indicated that the primary mechanism responsible for the removel of residual fluorine was pyrohydrolysis. It was found that a preliminary oxidation‐reduction cycle activated the less‐sinterable oxides so that in every case densities of at least 95% of theoretical were obtained by sintering at 1200°C.
Thermal Expansion of Uranium Pyrophosphate and of Ceramic Bodies in the System UO2–UP2O7
Authors: KIRCHNER HENRY P. , MERZ KENNETH M. , BROWN W. RICHARD
Published: June 2006

During an investigation of methods of predicting the thermal expansion of pure, single‐phase ceramics, uranium pyrophosphate (UP2O7) was synthesized and the thermal‐expansion properties were measured by the X‐ray diffraction and dilatometer methods. The basis for the selection of UP2O7 is discussed. Cubic UP2O7 expands with increasing temperature up to 400°C. Above this temperature the material contracts so that the specimen returns to the room‐temperature length at about 1000°C. Intermediate phases in the system UO2–UP2O7 were prepared and the thermal‐expansion properties were measured. Ceramic bodies in the system UO2–UP2O7 were prepared. The thermal‐expansion properties of these bodies are discussed in relation to the properties of the individual phases.
Evidence for High‐Temperature Forms of Zirconium and Tantalum Monocarbides
Authors: SHAFFER PETER T. B.
Published: June 2006

Evidence has been found which suggests the existence of high‐temperature crystalline modifications of both zirconium carbide and tantalum carbide. The high‐temperature inversion in zirconium carbide, indicated by a sharp decrease in spectral emisivity, in electrical resistivity, and in density, was reversible. No permanent changes in microhardness or in X‐ray diffraction patterns were found after cooling to room temperature. Emissivity measurements showed a hysteresis effect of approximately 400° C for zirconium carbide. A similar, although less sharply defined, effect was noted for tantalum carbide. No such effect was found in solid solutions of these two monocarbides.
Rapid Orientation of Sapphire Monocrystals
Authors: SHAW ROBERT R.
Published: June 2006

An optical method of orienting sapphire (α‐Al2O3) single‐crystal rods with respect to the basal plane has been devised. Measuring times are on the order of 1 minute per specimen, and the accuracy is to within a few degrees. The direction of inclination of the basal plane may be easily determined. Relations describing the relative intensity of light through a uniaxial crystal in a polarized light field have been derived. Simple equipment built around a photovoltaic cell has been used to confirm these relations experimentally.
Crystal Structure of Yttrium and Other Rare‐Earth Borates
Authors: NEWNHAM R. E. , REDMAN M. J. , SANTORO R. P.
Published: June 2006

The crystal structures of YBO3 and several isomorphous rare‐earth borates have been determined from X‐ray diffraction powder patterns. The unit cell is hexagonal with the borate groups parallel to c, and each rare‐earth ion is coordinated to a distorted cube of eight oxygens. Magnetic‐susceptibility measurements on ErBO3 show only slight deviations from ideal paramagnetic behavior at low temperatures.
High‐Temperature Thermophysical Properties of Uranium Monocarbide
Authors: GROSSMAN L. N.
Published: June 2006

Thermal conductivity (k), electrical resistivity (p), total hemispherical emittance (εt), and normal spectral emittance (ε0.65μ) of dense, arc‐cast uranium monocarbide (5.3 wt % total carbon) were measured in the temperature range 1150° to 2050°K. The results were as follows: k, 0.057 cal/sec‐cm‐deg, 1200° < T < 2050°K, probable error ± 0.002; p, 20.4 × 10−6+ 114.8T× 10−9 ohm‐cm, 1175° < T < 2050°K, probable error ± 1.7 × 10−6; εt0.42, 1250° < T < 1980°K, probable error ± 0.02; ε0.65 0.539 – 0.02T× 10−3 1150° < T < 1890°K, probable error ± 0.02. Experimental methods are discussed and error sources are analyzed. Uranium monocarbide exhibited typical metallic behavior in its thermophysical properties.
Studies of Early Stages of Paste Hydration of Different Types of Portland Cements
Authors: CHATTERJI S. , JEFFERY J. W.
Published: June 2006

The early stages of hydration of four different types of portland cements were studied by electron‐optical and X‐ray diffraction techniques. It was observed that, except for low‐heat cement, very little ettringite formed up to 3 hours of hydration and that the alite present in the cements was more reactive than the laboratory form. Ettringite formed earlier in the low‐heat cement than in other cements. Ettringite was found to be the stable sulfate‐bearing phase in sulfateresistant cement, at least up to 30 months, although in other cements ettringite began to change to monosulfate by 14 days. Direct evidence was found for the formation of gypsum from either CaSO4±0.5H2O or soluble anhydrite in some cements.
Study of Optical Glass Surfaces by Leaching with Nitric Acid: I, Polishing Lines
Authors: de la CIERVA P. , ARROYO L.
Published: June 2006

A study was made of the origin of fine lines that appeared on polished glass surfaces after leaching with nitric acid. The results were considered on the basis of theories of nonreflecting films and the polishing lines developed by hydrofluoric acid etching. The conclusions reached are compatible with the existence of deep fields of compression where the ionic exchange is enhanced.
Liquidus Temperatures in the System FeO—Fe2O3—TiO2
Authors: TAYLOR R. W.
Published: June 2006

Liquidus temperatures in the system FeO–Fe2O3–TiO2 have been estimated from data in the literature supplemented with experimental determinations of the liquidus temperature for about fifty different compositions within the system using the quenching method.
Dislocations and the Tensile Strength of Magnesium Oxide
Authors: STOKES R. J. , LI C. H.
Published: June 2006

It has been shown with single crystals, bicrystals, and polycrystalline material that the strength of magnesium oxide depends on the availability of mobile dislocation sources. Mobile dislocations, introduced by mechanical contact at the surface, are responsible for the ductility normally observed in single crystals. When mobile dislocations are removed by a chemical polish, single crystals become extremely strong (>160,000 psi) and elastic. In the absence of mobile dislocations bicrystals are also extremely strong and elastic but in their presence bicrystals are relatively weak (10,000 psi) and brittle. The brittleness is due to the direct interaction of slip bands with grain boundaries to generate cracks. The strength of high‐density polycrystalline magnesia is similarly sensitive to the presence of mobile dislocations. When care is taken to eliminate surface defects and to immobilize dislocations, tensile strengths of 30,000 psi can be attained, but when mobile dislocations are present the strength drops to 15,000 to 20,000 psi. Mobile dislocations can be introduced directly by mechanical contact or indirectly through the presence of pores.
Hot‐Pressing Alumina—Mechanisms of Material Transport
Authors: COBLE R. L. , ELLIS J. S.
Published: June 2006

The effect of load on initial neck growth between alumina single‐crystal spheres has been measured at 1530°C. The neck areas are larger than those observed in pressureless sintering and constant for all times between 10 and 480 minutes. The neck areas are proportional to the loads; i.e. they equilibrate at equal stresses (50,000 psi). It is shown quantitatively that the initial enhanced neck growth observed cannot be attributed to enhanced sintering by diffusion under the influence of stress. The plastic flow contribution to densification during hot‐pressing is calculated from the stress inferred from the foregoing measurements, from the applied load in hot‐pressing, and from geometric relations between particles. It is shown that for aluminum oxide the contribution of plastic flow to densification at the pressures normally used in hot‐pressing is small. It is concluded that the final stage of densification of alumina during hot‐pressing occurs by enhanced diffusion under the influence of stress.
Oxygen Penetration Into Single Crystals of Calcium Fluoride
Authors: PHILLIPS W. L. , HANLON J. E.
Published: June 2006

Oxygen penetration in calcium fluoride single crystals was determined along the [111], [110], and [112] directions by the micrographic method. The penetration depths were equal in all directions. The activation energy for the process was 46 kcal per mole. It is suggested that the penetration may be limited by the intrinsic diffusion rate of oxygen.
Sintering of Zinc Oxide
Authors: NORRIS L. F. , PARRAVANO G.
Published: June 2006

Sintering studies have been conducted with single crystal spheres of zinc oxide in air at total pressures of 10−3 to 1.0 atm over the range 1050° to 1250°C. Quantitative observations were made on the rate of growth of a neck between the spheres. No change in the distance between the geometrical centers of the spheres was observed. An analysis of the kinetic data shows that sintering was predominantly achieved by distillation through the surrounding gas phase. At 1150° the rate of welding was inversely influenced by the total pressure when the latter was changed from 0.003 to 0.75 atm. No conclusion could be reached on the effect of the oxygen partial pressure at constant total pressure. A brief summary of the various sintering mechanisms of zinc oxide from 700° to 1250°C is presented.
Phosphate–Halide Systems: I, Constitution of NaPO3‐NaF Glasses
Authors: MURTHY M. KRISHNA , MUELLER A.
Published: June 2006

The influence of sodium fluoride additions on the constitution of sodium metaphosphate glass has been determined by paper chromatographic techniques. Glasses with Na/P ratios varying from 1.5 to 1.22 and melted in air have been studied. It has been found that fluorine is lost from the melt during the normal preparation of glasses. When, however, the melt is quenched immediately after the components have melted into a homogeneous liquid, most of the fluorine is retained. With an increase in the melting time, the amount of fluorine retained by the melt decreases and after about 10 minutes all the fluorine is replaced by oxygen. The constitution of NaPO3‐NaF glasses with the varying Na/P ratios and with melting periods up to 15 minutes has been determined. When the glasses contain a considerable amount of fluorine, there is a breakdown in the structure of phosphate polymers. The results obtained are discussed in relation to the data reported by earlier investigators.
Modified Ferromagnetic Chromium Dioxide
Authors: KUBOTA BUICHI , NISHIKAWA TOMOZO , YANASE AKIRA , HIROTA EIICHI , MIHARA TOSHIHIRO , IIDA YOSHIO
Published: June 2006

Several mixtures in the system Te‐CrO2 were prepared by the decomposition of anhydrous chromic acid, CrO3, and telluric acid (H6TeO6) under high oxygen pressures; the physical and chemical properties were then studied. When Te was added, the grain size of CrO2 decreased rapidly from 5 to 10μ to 0.1 to 1.0μ and the magnetic coercive force increased from 20 to 120 oersteds. The magnetic Curie temperature and the lattice constants of CrO2 did not vary, however, with additions of Te up to 20 atomic %. X‐ray analysis showed that the CrO2 plus Te was not a solid solution but a mixture of CrO2 and TeCr2O6 that was nonmagnetic.
Phase Equilibria in the System NiO–Al2O3–SiO2
Authors: PHILLIPS BERT , HUTTA J. J. , WARSHAW I.
Published: June 2006

Equilibrium diagrams for the systems NiO‐SiO2, NiO‐Al2O3, NiAl2O4‐SiO2, Ni2SiO4‐NiAl2O4, and NiAl2O4‐Al6Si2O13 were drawn from data obtained by quenching and direct observational techniques. The only intermediate compound in the binary system NiO‐SiO2 is Ni2SiO4, which has the olivine structure. Unlike other olivines which melt congruently, nickel olivine has an upper temperature of stability (1545°C) and at temperatures between 1545° and 1650°C, NiO and SiO2 coexist in equilibrium. The only compound in the binary system NiO‐Al2O3 is NiAl2O4, which has a spinel structure. The nickel aluminate spinel varies in composition from 50 to 35 mole % Al2O3 at 1800°C, and the stoichiometric NiAl2O4 composition has a melting point near 2110°C. Of the joins within the ternary system NiO‐Al2O3‐SiO2 which were studied, only Ni2SiO4‐NiAl2O4 is not binary. In this join, crystals of NiO exist in equilibrium with liquid and a ternary assemblage of NiO + NiAl2O4+ liquid is stable to 1775°C. The decomposition temperature of Ni2SiO4 is decreased from 1545°C in the binary system to approximately 1490°C, presumably the result of solubility of NiAl2O4 in Ni2SiO4. The join NiAl2O4‐SiO2 is binary in that the compositions of crystalline phases can be expressed in terms of the chosen components. The eutectic temperature in the system is 1495°C. The join NiAl2O4‐Al6Si2O13 is binary for the same reasons and has a eutectic temperature at 1720°C. Using the data obtained in this study and those published for the well‐known system Al2O3‐SiO2, a liquidus surface diagram for the system NiO‐Al2O3‐SiO2 is proposed. Nickel olivine, even though it has an upper limit of stability in the binary system, has a primary field in the ternary system NiO‐Al2O3‐SiO2. This is the only refractory oxide system known to illustrate this so‐called “typical case,” the governing principles of which have been clearly presented in discussions of phase equilibria.
Calculation of Temperature Distribution in Glass Tanks by Use of a Special‐Purpose Electric Analog
Authors: COOPER A. R. , BUCHANAN R. C.
Published: June 2006

A low‐cost special‐purpose electric analog simulating heat flow in a transverse half section of a glass tank is described. It is easily constructed and is useful for studying steady‐state temperature distributions and heat‐flux densities in regions where convection can be ignored. Results are presented for physically realistic boundary conditions at the outer refractory surface, for an assumed symmetry about the transverse center line, and for three classes of boundary conditions at the free surface of the melt, namely the temperature distribution specified, heat‐flux density distribution specified, or a given relation between temperature and heat‐flux density. Heat transport by radiation is treated as radiation conductivity, and it is shown that even near the boundaries of the glass the error from this approximation is small provided the boundaries can be treated as blackbodies.
Volatility of PuO2 in Nonreducing Atmospheres
Authors: PARDUE WILLIAM M. , KELLER DONALD L.
Published: June 2006

The vapor pressure of plutonium dioxide (PuO2) was investigated in the range 1450° to 1775°C in air, argon, and oxygen atmospheres by a transpiration technique. There were strong indications that PuO2 can vaporize congruently or as a suboxide species, depending on the atmosphere. The δH°298 for vaporization in 1 atm of oxygen is approximately 154,000 cal per mole. The estimated standard free energy of formation (δG°f) of gaseous PuO2 is −121,000 + 10.7 T from 1227° to 1827°C.