bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristic Imperfections in Flux‐Grown Crystals of Yttrium Iron Garnet
Authors: LEFEVER R. A. , CHASE A. B. , TORPY JUANITA W.
Published: June 2006

Crystals of yttrium iron garnet grown from lead oxide and lead oxide‐lead fluoride flux systems are inhomogeneous and contain characteristic imperfections that may be significant in the evaluation of physical properties. A petrographic study of single‐crystal sections has revealed dendritic nuclei, oriented layers of submicroscopic foreign material located in the outer regions of the crystals, and oriented occlusions in intermediate positions. Changes in the appearance of thin sections resulting from the use of an oxygen atmosphere during synthesis combined with other observations indicate that divalent iron contributes to inhomogeneities and imperfections present in yttrium iron garnet crystals. Growth mechanisms involving an initial dendritic stage with (100) and (111) fast‐growth directions followed by layered growth parallel to major crystal planes, normally (110) and (211), can be deduced from the appearance and location of crystal imperfections.
High‐Temperature Energy Relations in the Alkali Borates: Binary Alkali Borate Compounds and Their Glasses
Authors: SMITH G. SHERWOOD , RINDONE GUY E.
Published: June 2006

The energy relations existing between the congruently melting compounds Li2O ‐2B2O3, Na2O–2B2O3, Na2O‐4B2O3, and K2O‐4B2O3 and their glasses have been determined for the temperature range 25° to 1100°C. High‐temperature heat‐content, entropy, and heat of solution data are given for both the glasses and the corresponding devitrified materials. A comparison of the heats of fusion of the alkali borates on a gram atom of oxygen basis shows that they follow the order Li > Na > K. The entropy differences between the glass and the corresponding crystalline material have been determined at 25°C. The free‐energy change at 25°C. for the reaction crystal → glass has been calculated for the four compounds.
Crystallization and Phase Relations of Boron Trioxide at High Pressures
Authors: MACKENZIE J. D. , CLAUSSEN W. F.
Published: June 2006

Crystalline B2O3 was readily obtained from the glassy phase at high pressures and temperatures. Single crystals 0.3 mm. in dimension of both α‐B2O2 (ordinary hexagonal) and β‐B2O3 (dense monoclinic) were prepared. The difference in the density of the two forms was about 20%. Crystals of β‐B2O3 were only slowly attacked by H2O and dilute HF. At atmospheric pressure, transitions between the α‐, β‐, and liquid phases were extremely sluggish. A tentative phase diagram was constructed up to 1100°C. and 90,000 atmospheres, the probable melting curve being calculated by the use of the Simon melting equation.
Immiscibility and the System Lanthanum Oxide–Boric Oxide
Authors: LEVIN ERNEST M. , ROBBINS CARL R. , WARING JON L.
Published: June 2006

The phase equilibrium diagram for the system La2O3‐B2O3 has been determined experimentally. The compounds La2O3‐3B2O3and La2O3‐B2O3 melt congruently at 1141°± 5°C. and 1660°± 15°C, respectively. At 1488°± 5°C, La2O3‐B2O3 inverts from the aragonite‐type structure to a high‐temperature form. Trilanthanum borate, 3La2O3 B2O3, melts incongruently at 1386°± 5°C. to give liquid and La2O3. No solid solutions exist in the system. A region of liquid immiscibility exists in the system and extends at 1136°± 5°C. from almost pure B2O3 to 21.5 mole % La2O3. The experimental value for the extent of immiscibility agrees with that calculated from theoretical considerations. A second method for estimating immiscibility in the system is demonstrated, which requires experimentally only the determination of the index of refraction of the modifier‐rich liquid. Principles governing immiscibility are discussed.
Reactions in the System PbO‐Ta2O5
Authors: SUBBARAO E. C.
Published: June 2006

Subsolidus phase relations in the binary system PbO‐Ta2O5 were investigated by the quenching method. The following compounds were identified by X‐ray diffraction patterns: PbO ‐2Ta2O5, PbO Ta2O6, 3PbO 2Ta2P5, 2PbO Ta2O6, 5PbO ‐2Ta2O5, and 3PbOTa2O5 The 1:1 compound has rhombohedral symmetry when it is prepared below 1150°C. Above this temperature, it yields an orthorhombic phase. Compounds with the same ratio of lead oxide to pentoxide exist in the systems PbO‐Ta2O6 and PbO‐Nb2O5.
Glassing Characteristics of Low‐Alloy Steels
Authors: DORMER GEORGE J. , NORTON GEORGE R. , PAYNE BURTON S.
Published: June 2006

Thermal‐expansion, stress‐temperature, and thermal‐shock tests were conducted on glassed low‐alloy and plain‐carbon steels. The addition of alloying elements increases the hardenability and strength of the steels but lowers the austenite‐to‐ferrite transformation temperature, thus decreasing the residual compressive stress in the glass coating and therefore its resistance to thermal shock. It is shown that D1, the calculated hardenability index, may be correlated with certain physical properties of the glass‐steel composites.
Investigation of the System Beryllium–Boron
Authors: HOENIG CLARENCE L. , CLINE CARL F. , SANDS DONALD E.
Published: June 2006

Mixtures of beryllium and boron powders were reacted under argon at elevated temperatures. X‐ray single‐crystal and powder diffraction analyses, chemical analyses, and Knoop micro‐hardness measurements were made. Melting‐point ranges were established for compounds of reasonable purity. One compound was identified. Beryllium diboride (BeB2) had a hexagonal unit cell. Its hardness was 3180 ± 100 (Hk100) and its melting point was greater than 1970°C. Beryllium hexaboride (“BeB6”) had a tetragonal unit cell, a hardness of 2577 ± 75 (Hk100), and a melting point between 2020°) and 2120°C. An anisotropic unknown phase existed whose Be: B ratio was between 6:1 and 2:1 and whose hardness ranged between 623 and 917 (Hk25), depending on orientation. A eutectic between beryllium and this unknown phase was observed at 972°± 15°C.
Influence of Platinum Nucleation on Constitution of and Phase Separation in Sodium Phosphate Glasses
Authors: MURTHY M. KRISHNA
Published: June 2006

Published work in the literature indicates that small amounts of platinum bring about phase separation in sodium phosphate melts which can be recognized in electron micrographs. The influence of 0.0038, 0.0076, 0.038, and 0.15% platinum on the constitution of and phase separation in sodium phosphate glasses with n, the number average chain length, varying from 3 to 9 has been investigated using both paper chromatographic and electron microscopic techniques. The results indicate that platinum nucleation apparently has no effect on the distribution of polyphosphates in the glasses studied, although electron micrographs show phase separation. The significance of the results in relation to immiscibility phenomena is discussed.
Elastic Stresses Produced by Indentation of Plane Surface of a Semi‐Infinite Elastic Solid by an Elastic Spherical Punch
Authors: SUCOV EUGENE W.
Published: June 2006

The general method of determining the stress in an infinite half‐plane elastic solid due to indentation by a rigid punch (originated by Sned‐don) is extended to include elastic, deformable indenters by measuring and introducing the equation of the deformed contour. This is an improvement over Hertz's method since, in addition to the elastic constants of the materials, which Hertz used, the deformed contour of the material while under load is available. The mathematics of the method is reviewed, and the tensile stress is calculated for a contour of the form uz(r) = A°+A2r4+A4r2 A description is given of the interferometric technique that was used to measure the indented contour in glass. The results of the calculation show that, for the specific case of a steel ball indenting a glass plate with moderate load, the simple Hertz theory is adequate. Application of this method to other materials and shapes is discussed briefly.
Fundamentals of Glass‐to‐Metal Bonding: VIII, Nature of Wetting and Adherence
Authors: PASK JOSEPH A. , FULRATH RICHARD M.
Published: June 2006

The sessile‐drop method for the evaluation of wetting is discussed in terms of forces acting on the liquid drop. For acute angles, or wetting of the solid, the driving force is the lowering of the solid‐gas surface energy by the liquid. Contact angles of approximately 25° and less, obtained under appropriate conditions, appear to be associated with interfacial conditions that lead to the development of a strong chemical bond (an interchange or sharing of electrons) and to good adherence. A theory is proposed whereby chemical bonding depends on the development of a balance of bond energies across the metal‐glass interface. The factors that lead to this condition are discussed. A modified Dupre's equation to take into account a strain factor and a contact coefficient is developed. Bonding of Na2Si2O5 molten glass to platinum, gold, and iron and oxidized iron in several atmospheres is discussed.
A Crystallographic Investigation of Calcium Diferrite
Authors: CHESSIN HENRY , TURKDOGAN E. T.
Published: June 2006

Calcium diferrite has been prepared at 1220°C in air. The lattice constants at 25° C of calcium diferrite have been determined by X‐ray powder data and have been based on the hexagonal system. They are a= 5.992 ± 0.004 A and co = 31.121 ± 0.008 A. The coefficients of thermal expansion were evaluated by X‐ray methods between‐130° and 25°C to be α1= 9.2 × 10−6 per°C and 3= 23 × lop6 per °C, where a3 is along the principal axis and α is perpendicular to it. The diferrite is ferromagnetic with a Curie point of 135°C. Comparison of the results obtained from the present work with those of some recent studies shows that the X‐ray data given by previous workers on compounds claimed to be Ca3FeleO15, Ca4Fe17O29, and Ca4Fe4O25 are for calcium diferrite. The present work, however, also indicates that when mixtures of calcium diferrite plus ferrous oxide (up to 6 wt%) are heat‐treated at 1220°C, a new phase appears together with the diferrite.
Direct Examination of Ceramic Surfaces with the Scanning Electron Microscope
Authors: THORNLEY R. F. M. , CARTZ L.
Published: June 2006

A direct electron‐optical method of observing an insulator surface is described and applied to a series of alumina ceramics. The surface of the object requires no previous treatment of any kind, and a resolving power of 2000 A has been obtained with a depth of focus of about 50p. Different phases and components can be distinguished. Fractured surfaces, a fault region, and polished surfaces of various alumina ceramics are examined.
Diffusion of Oxygen in Vitreous Silica
Authors: SUCOV EUGENE W.
Published: June 2006

The diffusivity of the oxygen ion in vitreous silica has been directly determined by exchange measurements employing the stable isotope 18O and mass spectrometer analysis. It was found that over the temperature range 925° to 1225°C the results can be represented by the equation D= 1.51 × 10−2 exp (‐71,200/RT) cm2 sec−1. These results are compared with other measurements of oxygen diffusion in silicate glasses. It is proposed that the controlling diffusion step in silicate glasses and nonstoichiometric silica is the rupture of a single oxygen bond to silicon and that the diffusion mechanism is interstitial motion through voids in the lattice. An analysis of theoretical expressions for the pre‐exponential term DO shows that present theories are unable to predict DO for oxygen diffusion in glasses. It is also shown that the mechanism for electrical conduction in vitreous silica or in electrolytically purified quartz is not migration of oxygen ions.
Melting Relations of CaO‐Manganese Oxide and MgO‐Manganese Oxide Mixtures in Air
Authors: RIBOUD P. V. , MUAN ARNULF
Published: June 2006

Melting relations in the systems CaO‐manganese oxide and MgO‐manganese oxide in air have been determined at temperatures up to 1705°C. In the system CaO‐manganese oxide four crystalline phases have stable existence in equilibrium with liquids: lime (approximate composition CaO‐MnO), spinel (approximate composition Mn3O4‐CaMn2O4), and two ternary solid solution phases in which Ca/Mn ratios as well as oxygen contents vary over considerable ranges. One of these ternary solid solution phases may for the sake of simplicity be represented approximately by the formula CaMnO3 and the other by the formula CaMn2O4. Three isobaric invariant situations exist, with temperatures and phase assemblages as follows: At 1588°± 10°C the two crystalline phases lime and CaMnO3 coexist in equilibrium with liquid (40 wt% CaO, 60 wt% manganese oxide) in a peritectic situation. Another peritectic at 1455°± 5°C is characterized by the equilibrium coexistence of CaMnO3, CaMn2O4, and liquid (25 wt% CaO, 75 wt% manganese oxide). A eutectic situation exists at 1439°± 5°C with CaMn2O4, spinel, and liquid (18 wt% CaO, 82 wt% manganese oxide) present together in equilibrium. In the system MgO‐manganese oxide in air periclase‐manganosite solid solution (approximate composition MgO‐MnO) and spinel (approximate composition Mn3O4‐MgMn2O4) are the only crystalline phases present in equilibrium with liquids. Liquidus and solidus temperatures increase with increasing MgO content. A peritectic situation exists at 1587°± 10°C, with the two crystalline phases coexisting in equilibrium with liquid (1 wt% MgO, 99 wt% manganese oxide).
Wettability of Kaolinite Treated with Ammonia. Methylanline, Ethylamine. or Their Corresponding Cations
Authors: KITAHARA AYAO , WILLIAMSON W. O.
Published: June 2006

Equations developed from simplifying assumptions related the flow rate of water into kaolinite plugs to the clay‐water contact angle, and showed that the wettabilities were reduced by ammonium, methylammonium, or ethylammonium as exchangeable cations, or by ammonia, methyl‐amine, or ethylamine as physically held adsorbates. Poorly crystalline kaolinites were especially affected by these cations. Both the exchangeable cations and the crystal surfaces between the exchange sites influenced wettability. These surfaces, unless partly or completely covered by ammonia or amines, enhanced wettability when crystallinity was poor. Ethylamine markedly decreased the wettability of kaolinite with good crystallinity, probably because it was difficult to displace from cavities in the stacklike crystals. Kaolinite with montmorillonite behaved anomalously.
Mechanical Properties of Pure, Dense Aluminum Oxide as a Function of Temperature and Grain Size
Authors: SPRIGGS R. M. , MITCHELL J. B. , VASILOS T.
Published: June 2006

The elastic modulus and transverse bend strength of pure, dense alumina specimens were determined as a function of grain size (1 to 250μ) and temperature (30° to 1500°C). The elastic modulus was essentially independent of grain size over the temperature range covered. The transverse bend strength for fine–grain–sized alumina was substantially greater than that for larger–grain–sized alumina over the entire temperature range, although, at the highest temperatures, the rate of decrease of strength with temperature was greatest for the he–grained material. Fine–grained alumina (1 to 2P) exhibited considerable yielding and nonlinear load–deflection behavior at 1000°C and above. At 150O°C, the 1‐ to 2‐μ specimens bent to the limit of the apparatus without fracturing (approximately 7% outer‐fiber strain).
Inverse Segregation of MgO and MgAI2O4 in Fusion‐Cast Bodies
Authors: RIBBE P. H. , ALPER A. M.
Published: June 2006

Rapidly cooled castings formed from certain liquids in the system Mg0‐MgA1204 are observed to have an enrichment of the low‐melting spinel in the early solidified skin of the casting. Periclase, the high‐melting phase, is concentrated in the core of the casting. Following the metallurgical literature, an explanation for this nonequilibrium phenomenon, known as inverse segregation, is advanced which involves volume contraction upon solidification and flow‐back of residual, spinel‐rich liquids along interdendritic channels to the contraction volumes. The dependence of phase segregation on cooling history is discussed. Inverse segregation is negligible near the eutectic and extreme near the 70 wt% MgO concentration.
Phase Relations in the System UO2‐UO3– Y2O3
Authors: BARTRAM S. F. , JUENKE E. F. , AITKEN E. A.
Published: June 2006

The phase relations in the system U02‐U03‐Yz03, particularly in the Y203‐rich region, were examined by X‐ray and chemical analyses of reacted powders heated at temperatures up to 1700°C in H2, CO2‐CO2 and air. Four phases were identified in the system at temperatures between 1000° and 1700°C: U308, face‐centered cubic solid solution, body‐centered cubic solid solution, and a rhombohedral phase of composition (U,Y)7O2 ranging from 52.5 to 75 mole % Y2O3. The rhombohedral phase oxidized to a second rhombohedral phase with a nominal composition (U,Y), at temperatures below 1000°C. This phase transformed to a face‐centered cubic phase after heating in air above 1000° C. The solubility of UO, in the body‐centered cubic phase is about 14 mole % between 1000° and 1700°C but decreases to zero as the uranium approaches the hexavalent oxidation state. The solubility of Yz03 in the face‐centered cubic solid solution ranges from 0 to 50 mole % Y2O3 under reducing conditions and from 33 to 60 mole % Y2O3 under oxidizing conditions at 1000°C. At temperatures above 1000° C, the face‐centered cubic solid solution is limited by a filled fluorite lattice of composition (U,Y)O2. For low‐yttria content, oxidation at low temperatures (<300°C) permits additional oxygen to be retained in the structure to a composition approaching (U,Y)O2.25 A tentative ternary phase diagram for the system UO2‐UO3‐Y2O3 is presented and the change in lattice parameter and in cell volume for the solid‐solution phases is correlated with the composition.
Grain‐Boundary Migration in LiF BicrystaIs
Authors: DAVIS M. P. , TALLAN N. M.
Published: June 2006

Large‐scale grain‐boundary movements, apparently due to temperature‐gradient zone melting, have been observed in macroscopic LiF bicrystals. Bicrystals containing bodndaries of varying orientations were prepared by sintering LiF single crystals at temperatures 20’to 3O° C below their melting point in air and in argon. Although no appreciable amount of sintering was observed during prolonged heating periods at very slightly lower temperatures, at these temperatures a boundary capable of large‐scale movement formed rapidly. Subsequent heating at the same temperature resulted in boundary movements of 5 mm or more within 12 hours, frequently in a direction opposed to the radius of curvature. In some specimens boundary sliding and rotation, strongly suggestive of the presence of an inter‐facial liquid layer, were observed.
Calcination of Be0 from Basic Acetate‐Derived Be(OH)2
Authors: RAU ROBERT C.
Published: June 2006

X‐ray diffraction, electron microscopy, and infrared spectroscopy were used to study the changes in BeO powders produced by the calcination of basic acetate‐derived Be(OH)2. Weight loss, hydroxyl ion content, particle configuration, and crystallite growth were observed as a function of increasing calcination temperature. Low‐temperature calcining (<360°C) yielded a Be0 product which showed incomplete weight loss, very small crystallite size, and appreciable water content. Calcining at high temperatures (>375°C) formed Be0 showing the theoretically predictable weight loss and very little water present. The size of the beryllia crystallites increased with increasing calcination temperature, but the size and shape of the particles remained constant. Basal‐plane stacking faults were observed in the calcined BeO.
Constitution and Microstructure of Some Binary Alkali Halide Mixtures
Authors: LOXHAM J. G. , HELLAWELL A.
Published: June 2006

The constitutions of binary alkali halide systems are considered for the fluorides, chlorides, and bromides of lithium, sodium, and potassium. These systems are divided equally into those that are simple binary systems having a common ion and those that are capable of double decomposition into reciprocal salt pairs, AB + CD ⇌ AD + BC. The simple binary systems having been examined previously, the present work was principally concerned with the constitution of the pseudobinary systems. Using thermal analysis, X‐ray methods, and microscopy, the liquidus and temperature horizontals were determined for 18 such systems and the equilibria were interpreted with reference to quaternary systems. The tendency of a given salt pair to precipitate the reciprocal salts may be related to the relevant lattice energies. Microscopic examination of directionally frozen specimens revealed that true binary eutectic mixtures freeze with regular two‐phase distributions very similar to those observed in metallic eutectics; these distributions are illustrated.
Adsorption of Colloidal Silica on Alumina and of Colloidal Alumina on Silica
Authors: ILER R. K.
Published: June 2006

The mutual adsorption of colloidal silica on alumina and of colloidal alumina on silica and silicate materials occurs in aqueous suspension at about pH 4. It is shown that the adsorption of colloidal particles on the surface of opposite charge is limited to essentially a monoparticle layer. An adsorbed layer of fibrils of colloidal alumina on the surfaces of silica, asbestos, graphite, and finely divided clay is shown in electron micrographs. The effect of the adsorbed colloid on dispersibility of the substrate materials is discussed.
Growth and Properties of Single Crystals of Hexagonal Ferrites
Authors: SAVAGE ROBERT O. , TAUBER ARTHUR
Published: June 2006

Single crystals of hexagonal ferrites up to 1/2 in. long were grown from the system NaFeO2‐Fe2O3‐BaO‐MeO, where Me = divalent Zn, Co, Ni, or Mg. NaFeO2 was the flux from which crystals were grown in platinum crucibles from a maximum temperature of 1250° to 1375°C. More than 150 single‐crystal growth experiments were attempted and the reaction products were studied by X‐ray diffraction and optical microscopy. Stability data for the principal single‐crystal products are given for initial compositions lying in quaternary planes. Such planes were considered for BaO/MeO ratios corresponding to the compounds 1/1 for Ba2Me2Fe12O22(Y) and Ba2Me2Fe28O46(X), 3/2 for Ba3Me2Fe24O41(Z), 2/1 for Ba4Me2Fe36O60(U), and 1/2 for BaMe2‐Fe16O27(W)(Me = Zn, Co, Ni, or Mg). A number of adjoining planes were also considered. All the five known structure types were grown as single crystals. A series of four new hexagonal ferrite structures was discovered. These were derived from Z by systematically adding blocks of Y. Magnetization as a function of temperature and field was investigated for crystals of two structure types. The room‐temperature ferromagnetic resonance and effective anisotropy were studied for substituted crystals of the same two structure types.
Mechanism of Decomposition of the Cubic Solid Solutions in the System ZrO2—MgO
Authors: VIECHNICKI D. , STUBICAN V. S.
Published: June 2006

The phase diagram for the system ZrO2‐MgO was reinvestigated by using coprecipitated gels. The thermal stability of the defective cubic solid solutions was investigated by a study of kinetics. The decomposition curves were sigmoidal, indicating that the formation of the tetragonal solid solutions proceeded by a process of nucleation and growth. Decomposition comprised: (1) formation of the nuclei of the tetragonal solid solution on the grain surface, (2) growth of the nuclei leading to the formation of an interface, and (3) the irregular growth of that interface into the interior of the grain. During the decomposition magnesium ions diffused out of the regions of the growth of the tetragonal phase and partly precipitated as magnesium oxide at the grain boundaries. The decomposition rate increased with the degree of ordering or clustering of defects and impurities and with the number of the anion defects; it showed a maximum at about 1200°C.
Calculation of Viscosity‐Temperature Curves for Porcelain Enamels from the Flow‐Button Test
Authors: DEKKER P.
Published: June 2006

A procedure was developed for relating the speed of flow of enamel on an inclined plate to the viscosity‐temperature curve of the enamel. The results of the flow‐button test are represented in three‐dimensional flow diagrams. An equation was developed for the calculation of the viscosity‐temperature curves of twelve types of enamels. The equation includes a constant Q, having a value of 2.565, for flow of enamel samples on a plate inclined at 45°. Application of this method as a control for enamel melts is demonstrated. The influence of overmelting and undermelting on the viscosity of the enamel at different temperatures was examined.
Vaporization of Tantalum Carbide‐Hafnium Carbide Solid Solutions
Authors: DEADMORE D. L.
Published: June 2006

The vaporization rates in vacuum of hot‐pressed HfC, TaC, and solid solutions of these carbides in the range 2225° to 2725°C were determined by a Langmuir‐type method. A composition near 80TaC.ZOHfC (mole %) exhibited the lowest vaporization rate of the compositions within this pseudobinary system. Variations in initial sample bulk density and vapor‐specie condensa tion on the furnace wall have negligible effects on the measured vaporization rates.
Optical Absorption Study of the Reduction Kinetics of Rutile Crystals
Authors: CARNAHAN R. D. , BRITTAIN J. O.
Published: June 2006

The early stages of the reduction kinetics of single‐crystal rutile, TiO2, were studied by optical absorption techniques for specimens re duced in the range 550° to 760°C at a constant vacuum level of 10−3 mm Hg. When reduced to a room‐temperature resistivity value of ∼103 ohm‐cm, rutile shows a blue coloration as a re sult of a broad infrared absorption band centered at a wavelength of 1.2μ. The kinetics of growth of the optical absorption coefficient at 1.2μ fit a parabolic relation of the form (Δα)2=K′t. The Arrhenius rate constant, K′, exhibited an activation energy of 111 ± 9 kcal/mole which is ∼50% too high for the diffusion of oxygen in rutile. It is postulated that the defect center is likely to be a Ti interstitial and that the kinetics reflect the self‐diffusion of Ti as the rate‐con trolling mechanism.
Preparation of Ultra‐High‐Purity Submicron Refractory Oxides
Authors: MAZDIYASNI K. S. , LYNCH C. T. , SMITH J. S.
Published: June 2006

A method was developed for preparing ultra‐ high‐purity submicron powders of refractory oxides from transition metal alkoxides. Compounds of the type M(OR)3 and M(OR)4, where R is an alkyl group such as C4H9‐, were thermally decomposed to oxides at 325° to 450°C at atmospheric pressure. Techniques were perfected to prepare, on a continuous basis, 99.95+% zirconia and hafnia with an average particle size of 100 to 200 A. The fine‐particle zirconia powder is cubic at room temperature and transforms completely to monoclinic when heated above 40O°C. The powder densifies at a considerably lower temperature than commercial spectrographic‐grade (99.9%) zirconia.
Effect of Crystal Orientation on the Mechanical Behavior of Magnesium Oxide at High Temperatures
Authors: DAY R. B. , STOKES R. J.
Published: June 2006

The high‐temperature deformation of magnesia single crystals with a [110] tensile axis is described and related to previous observations on [001] crystals. The [110] tensile axis favors slip on systems with oblique vectors (i.e. at 120°). Two main modes of deformation are identified and distinguished by the interpenetrability of oblique slip: (1) Between 1400° and 1700°C interpenetration does not occur. The crystal becomes subdivided into distinct blocks slipping on different systems. These blocks are separated by sharp kink boundaries which act as barriers to further slip. Voids form in the kink interfaces and lead to brittle fracture. (2) Above 1700°C slip on all systems interpenetrates and a stable substructure develops throughout the gage section. At high strains the single crystal recrystallizes. The specimen work hardens and elongates 100% before necking down to completely ductile fracture. This behavior is discussed in terms of dislocation interactions.
Constitution of Fireclays at High Temperatures: I, Methods of Analysis
Authors: McGEE THOMAS D.
Published: June 2006

Qualitative X‐ray diffraction of a fireclay brick revealed no major change in crystalline composition, other than the inversion of cristobalite, from room temperature to 1500°C. Methods of quantitative analysis of specimens at room temperature were considered. The internal standard technique of quantitative X‐ray diffraction was selected as the most reliable. Using this technique the effectiveness of quenching was investigated. Quenched analyses appear to be suitable for representing the constitution at high temperatures.
Constitution of Fireclays at High Temperatures: III, Deformation Characteristics
Authors: McGEE THOMAS D.
Published: June 2006

The hot‐pressing characteristics of kaolin, fireclay, and plastic fireclay were determined between 1150° and 155O°C at 3000 to 10,000 psi under oxidizing conditions. Each clay could be pressed to near its true density at an optimum temperature. Insufficient temperature produced low bulk density; excessive temperature caused bloating. Synthetic glasses were prepared to represent the composition of the liquid phase estimated to be present at the optimum pressing temperature. Viscosities of the synthetic glasses were measured, and those of the optimum pressing temperature were estimated. The deformation characteristics are in reasonable accord with the Mackenzie and Shuttleworth hot‐pressing equation for viscous flow.
Cation Diffusion in Single‐Crystal and Polycrystalline BeO
Authors: AUSTERMAN STANLEY B. , WAGNER J. W.
Published: June 2006

The diffusion of Be was measured in single crystals of BeO in directions normal and parallel to the hexagonalcaxis. The diffusion coefficients,D, in the two directions were nearly equal to each other. The values ofD, measured between 1500° and 2000°C were quite similar to values reported previously for high‐density, high‐purity, polycrystalline BeO. The single‐crystal data, taken in conjunction with polycrystalline data, show that the observed diffusion in polycrystalline BeO proceeds entirely by volume diffusion with no significant diffusion along grain boundaries, although there is some evidence of rapid surface diffusion along microcracks in the surface. The data are interpreted in terms of extrinsic impurity‐dependent diffusion via mobile vacancies.
Vibratory Compaction: II, Compaction of Angular Shapes
Authors: AYER J. E. , SOPPET F. E.
Published: June 2006

Experiments were conducted on compaction of steel grit in elongated cylindrical containers. The packing efficiency of angular shapes is a function of particle shape and absolute size. The derived relation between packing efficiency and particle size is similar to that for spherical systems with the addition of a shape factor. The equations allow calculation of packing fractions of multicomponent systems in terms of diameter ratios only. Application of the findings was made by loading sixteen nuclear fuel specimens by vibratory compaction.
Dry Strength of Pelletized Spheres
Authors: KAPUR P. C. , FUERSTENAU D. W.
Published: June 2006

Three limestone powders, differing only in specific surface area, were agglomerated in a balling drum to form pellets of various sizes. The pellets were tested for dry compressive strength at different rates of deformation. A limiting elastic energy criterion for failure was used to derive the relation (analogous to the classical Hertz relation for strength of an elastic isotropic sphere) between the pellet size, the total deformation, and the load at failure. The surface area of the powder, the porosity of the pellet, and its compressive strength are analytically related; the results are in good agreement with the experimental data.
Phase Equilibria in System CaO‐CO2‐H2O and Related Systems, with Implications for Crystal Growth of Calcite and Apatite
Authors: WYLLIE PETER J.
Published: June 2006

Conditions for crystallization of calcite from melts in the presence of a vapor or gaseous phase are reviewed to provide possible guidelines for growth of calcite. Phase equilibrium data for the system CaO‐CO2 show that to precipitate calcite from molten CaCO3 the temperature must be above 1230° C and excess CO2 must be present at pressures greater than 39.5 bars. Phase equilibrium data for the system CaO‐CO2‐H2O show that calcite can be precipitated from melts at 650°C in the presence of an aqueous vapor phase at 10 bars or more. Crystallization can be induced either by introducing temperature variations, or by changing the composition of the coexisting aqueous vapor phase under isobaric, isothermal conditions. The system CaO‐MgO‐CO2‐H2O is used to show that doped calcite crystals, CaxR1‐xCO3, could be precipitated, with precisely controlled compositions, from melts in the system CaO‐RO‐CO2‐H2O. Apatite phase relations are also presented.
Deformation Mechanisms in Polycrystalline Graphite
Authors: SLAGLE O. D.
Published: June 2006

The microstructure of SGBF graphite was observed under tensile and compressive stresses. Increasing stress generated extensive cracking parallel to the layering direction in the particles. Such cracking, however, was not necessarily directly attributable to the low strength of the graphite crystallites in the c direction but rather to flaws or weak regions which tended to occur between the layer planes. For tensile stress, the cracks were perpendicular to the direction of the applied stress, whereas in compression, the cracking was parallel to the applied stress. Analysis of the stress‐strain relations for SGBF graphite in tension indicates a discrepancy with the previously proposed plastic deformation model. The discrepancy is attributed to the effect of the observed cracking on the internal stress distribution. An alternative explanation is proposed on the basis of internal stresses, localized cracking, and interlayer slip.
Gamma‐Induced Absorption Bands Associated with Tl+, Pb2+, or Bi3+ in Potassium Borate Glasses
Authors: BISHAY A. M. , MAKLAD M. S.
Published: June 2006

Gamma irradiation of potassium borate glasses containing about 1.8 mole % Tl+, Pb2+, or Bi3+ resulted in two induced absorption bands which the authors call T and L bands. The T band was observed at about 1.1, 1.55, or 1.8 ev, and the L band was observed at about 1.8, 2.6, or 2.7 ev in alkali borate glasses containing Tl+, Pb2+, or Bi3+, respectively. The shifting of the band positions to higher energies was attributed to the increasing polarizing power of these ions as in the case of the F band induced in alkali halides. The effect of the addition of cerium on the intensity of the T and L bands induced in glasses containing lead or thallium and prepared under different melting conditions suggested strongly that these two bands are associated with electron trap centers near these ions.
Zinc Tellurite Glasses
Authors: REDMAN M. J. , CHEN J. H.
Published: June 2006

Glass formation was observed in the system ZnO‐TeO2 in mixtures containing 20 to 40 mole % ZnO. Softening occurred at 350°C and the glasses crystallized at 400°C. High dielectric constants (ca. 20) and high electrical resistivities (ca. 1011 ohm‐cm−1) were measured. The zinc tellurite glasses have a higher density and refractive index and are considerably softer than silicate glasses. The optical transmission range was between 0.38 and 6.6μ with two absorption bands in the infrared. Spectra of Cu2+ and Nd3+ doped samples are also given.
Cubic Phase Stabilization of Translucent Yttria‐Zirconia at Very Low Temperatures
Authors: MAZDIYASNI K. S. , LYNCH C. T. , II J. S. SMITH
Published: June 2006

Simultaneous decomposition of yttrium and zirconium alkozides was used to obtain an almost ideal mixture of powders of high surface activity. From this powder a translucent body, “Zyttrite,” was made with a grain size of less than 1μ. The mixed oxide was consolidated into a stabilized body by firing at 1000°C for 30 min. This is indicative of a phenomenal increase in solid state reactivity. High‐density fully stabilized cubic solid solutions of 6 mole % Y2O3‐ZrO2 were obtained on sintering at 1450°C. A typical specimen had a density of 5.9 g/cm3, a coefficient of thermal expansion of 11 × 10−6 in./in.°C, and a grain size of 2 to 4μ. Test pieces withstood 2200°C firings in air for 262 hr with grain growth of 35 to 50μ and virtually no change in composition, density, or stabilization.
Transitions in Vapor‐Deposited Alumina from 300° to 1200°C
Authors: DRAGOO A. L. , DIAMOND J. J.
Published: June 2006

The transition of amorphous alumina to α‐alumina was studied by X‐ray diffraction, electron diffraction, DTA, TGA, and microscopic observation. The amorphous alumina was prepared by condensing vapor from evaporating molten alumina in vacuo onto the glass envelope of the vacuum chamber. The amorphous alumina was transformed to a poorly crystalline material by heating for 16 hr between 570° and 670°C. Between 670° and 1200°C, the poorly crystalline alumina was converted to α‐alumina via two parallel series of transition aluminas. The principal series was γ‐alumina to δ‐alumina to α‐alumina. A minor amount of θ‐alumina developed from the initial crystallization and persisted throughout the duration of the principal series as a parallel path. Some conversion of δ‐ to θ‐alumina was detected above 900°C. DTA produced an unexplained exothermic peak at 320°C and a second exothermic peak at 860°C which corresponded to formation of metastable aluminas.
Phase Equilibrium in the System PbO‐TiO2–ZrO2
Authors: FUSHIMI SHOICHI , IKEDA TAKURO
Published: June 2006

Phase equilibrium relations in the system PbO–TiO2–ZrO2 were studied by quenching in the range where the PbO content is 50 mole % and more. Isotherms were examined at 1100°, 1200°, and 1300°C and tie lines were determined between the liquid and solid solution in equilibrium. The incongruent melting point of PbZrO3 was 1570°C and the equilibrium between liquid, PbO‐type solid, and PbZrO3 is peritectic. Pb(Zr,Ti)O3 solid solutions containing more than 14 mole % PbZrO3 decomposed to liquid, ZrO2, and Pb(Zr,Ti)O3 and the decomposition temperature rises from 1340° to 1570°C with increasing PbZrO3 content. The system PbTiO3–PbZrO3 should not be treated as a binary, but as a section of the ternary system.
Solid Solution of Boron in Graphite
Authors: LOWELL C. E.
Published: June 2006

The solubility of boron in graphite was determined in the temperature interval of 1800° to 2500°C. The maximum solubility was 2.35 at. % at 2350°C; the solution was shown to be substitutional.
Sensitive Resonant Frequency Technique for the Study of Sintering Kinetics
Authors: MARLOWE M. O. , WILDER D. R.
Published: June 2006

A technique is described for following the progress of sintering based on changes in the flexural resonant frequency of a prismatic bar. The relations involved are defined and a simple relation between the linear shrinkage and the resonant frequency is derived. These two are related by a multiplier which is shown to be a function of the initial porosity and the elasticity‐porosity relation of the material. Typical values of the multiplier are large (>25), making this a very sensitive method of detecting shrinkage. Sintering‐related shrinkage was observed in yttrium oxide, erbium oxide, dysprosium oxide, and aluminum oxide at very low temperatures, often as low as two tenths of the absolute melting temperature.
The System KAlSiO4–Mg2SiO4–KAlSi2O6
Authors: LUTH W. C.
Published: June 2006

Schairer's study (1954) on phase relations in the system KalSi2O6–Mg2SiO4–SiO2 was extended to include the system KalSiO4–Mg2SiO4–KalSi2O6. It is shown that this join is ternary; however, the relatively high vapor pressure of the condensed phases prohibits study by the usual quenching techniques. The apparent intersection of the (KalSiO4–Mg2SiO4–SiO3) join with the primary phase volume of spinel is attributed to loss of the alkali‐silicate constituents by vapor transport. This results in the effective bulk composition being moved away from this join toward the primary phase volume of spinel in the system K2O–MgO–Al2O3–SiO2.
Flow Properties of Aqueous Suspensions Containing Kaolins of Varying Degrees of Crystallinity
Authors: ORMSBY W. C. , MARCUS J. H.
Published: June 2006

The influence of varying degrees of crystal perfection of several Georgia kaolins on the flow properties of aqueous systems containing these clays was studied. The fractionated clay samples were characterized with respect to clay mineral composition, crystallinity, surface area, and cation‐exchange capacity. In general, results indicated that dilatant and associated properties were controlled by the degree of crystal perfection whereas the viscous and plastic properties, at a given water content, were usually dependent on particle size.
Condensed Phase Relations in the Systems ZrO2‐WO2‐WO3 and HfO2‐WO2‐WO3
Authors: CHANG LUKE L. Y. , SCROGER M. G. , PHILLIPS BERT
Published: June 2006

Phase relations for the systems ZrO2–WO2–WO3 and HfO2–WO2–WO3 from 1000° to 1700° C were determined by the quenching technique using sealed sample containers. In the system ZrO2–WO3, 1:2 compound, ZrW2O8 forms, having a cubic structure with a= 9.159 A. The ZrW2O8 melts incongruently at 1257°± 3°C to ZrO2 and liquid and has a lower limit of stability at 1105°C, below which ZrO2 and WO3 coexist in equilibrium. One eutectic and one peritectic were established: at 1231°± 3°C and 74 mole % WO3, and at 1257°± 3°C and 71 mole % WO3, respectively. Along the join ZrO2–WO2, no compound formed. Two invariant points were determined: ZrO2, WO2, W, and liquid are in equilibrium at 1430°± 5°C and 76 mole % WO2, whereas WO2, W18O49, W, and liquid coexist at 1530°± 5°C and 89 mole % WO2‐ Equilibrium relations in the system ZrO2–WO2–WO3 were investigated at four temperatures. At 1200°C, a cubic phase with composition near W20O58 was found; it exists in equilibrium with ZrO2, W18O49, W20O58, and WO3. As the temperature increases, the liquid formed along the ZrO2–WO3 join extends into the ternary system, crosses the join ZrO2–W20O58 at 1300°C, and crosses the join ZrO2–W18O49 at 1400°C. The cubic phase can take more zirconium into its solid solution at 1300° than at 1200°C. At 1500°C, the system can no longer be treated as a simple ternary oxide system because of the presence of metallic tungsten, and equilibrium relations are presented on the basis of the system ZrO2–W–WO3. Phase equilibrium relations in the systems HfO2–WO3, HfO2–WO2, and HfO2–WO2–WO3 in the temperature ranges studied are much like those in the corresponding zirconium system.
Phase Equilibria in the System MgO‐FeO‐Fe2O3: The 1300°C Isothermal Section and Extrapolations to Other Temperatures
Authors: SPEIDEL DAVID H.
Published: June 2006

The 1300°C isotherm of the system MgO–FeO–Fe2O3 was studied thermogravimetrically under conditions of controlled fugacity of oxygen. The magnesioferrite solid solutions that coexist in equilibrium with magnesiowüstite solid solutions have a cation to anion ratio experimentally indistinguishable, in the present study, from 0.750. Curves are presented expressing the change in composition of coexisting magnesioferrite and magnesiowüstite phases as a function of temperature and oxygen fugacity. These curves for the system MgO‐FeO‐Fe2O3 can be used (1) to predict compositional relations under isothermal conditions for temperatures where reaction rates are sluggish, (2) as additional oxygen buffer curves for experimental control of oxygen fugacity, and (3) in certain instances to distinguish equilibrium from nonequilibrium assemblages.
Lower‐Temperature Modifications of Nb2C and V2C
Authors: RUDY ERWIN , BRUKL CHARLES E.
Published: June 2006

The orthorhombic, low‐temperature α‐modification of Nb2C has a structure similar to that of ζ‐Fe2N (a = 12.36 A, b = 10.895 A, c = 4.968 A) and transforms at ∼1200°C into the hexagonal ε‐Fe2N type. A second transition at approximately 2500°C is associated with the destruction of long range order in the carbon sublattice. Alpha‐divanadium carbide (orthorhombic, a = 11.49 A, b = 10.06 A, c = 4.55 A) is isostructural with α‐Nb2C and transforms at ∼800°C into the hexagonal high‐temperature modification. The structures of α‐V2C and α‐Nb2C are distorted modifications related to the ε‐Fe2N type.
Superparamagnetic Behavior of MnFe2O4 and α‐Fe2O3 Precipitated from Silicate Melts
Authors: SHAW ROBERT R. , HEASLEY JAMES H.
Published: June 2006

Manganese ferrite and α‐Fe2O3 particles were precipitated within silicate melt systems to produce very unusual magnetic properties. Assemblies of particles of both kinds behaved super‐paramagnetically when the particle size was small enough. As the particle size was increased, the magnetic properties of the ferrite system increased, but those of the α‐Fe2O3 system decreased; the latter is expected from Néel's theory of a net spontaneous magnetic moment created by uncompensated magnetic sublattices at very small particle sizes. Liquid‐in‐liquid phase separation was pronounced in the manganese ferrite‐glass systems, which may have influenced the precipitation behavior. Room‐temperature initial mass susceptibilities were as high as 2 × 10 −2 cgs, and specific magnetizations as high as 26 gauss/g were observed. Precipitation of α‐Fe2O3 particles exhibiting super‐paramagnetic behavior was possible only with very low‐viscosity melts. Initial mass susceptibility values changed by as much as a factor of 30 between 296° and 77°K.
High‐Temperature Creep and Dislocation Etch Pits in Polycrystalline Beryllium Oxide
Authors: BARMORE WILLIS L. , VANDERVOORT RICHARD R.
Published: June 2006

Compressive creep of high‐density polycrystalline beryllium oxide was investigated in the range 1850° to 2050°C. Creep rate was dependent on the applied stress to the 2.5 power, and the apparent activation energy for creep was 145 kcal/mole. Etch pit studies showed that the dislocation density in tested specimens was two orders of magnitude greater than that in assintered material. The diffusion process controlling creep was ascribed to volume diffusion of the anion. The deformation behavior was governed by dislocation motion.
Localized Cooling in Flux Crystal Growth
Authors: CHASE A. B. , OSMER JUDITH A.
Published: June 2006

Large crystals of ZnO, Al2O3, Ga2O3, ThO2, Y3Ga5O12, ZnGa2O4, and ZrO2 were grown from PbO‐PbF2 flux systems using a temperature gradient and localized cooling induced by a jet of cold air directed on the crucible bottom. The temperature gradients in the crucible were much less than that in the furnace. The technique is described, and crystals grown with and without a temperature gradient are compared.
Comparison of Strength of Triaxial Porcelains Containing Alumina and Silica
Authors: WARSHAW S. I. , SEIDER R.
Published: June 2006

The types of fractures in a whiteware body containing quartz vary as a function of quartz grain size. The transition from one type of fracture to another is illustrated by strength, thermal expansion, and water absorption, as well as microstructural observations. The thermal expansion behavior of compositions containing alumina does not vary as a function of grain size, thus showing the absence of fracture in white‐ware bodies containing alumina.