bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of the Properties of Glazes by the Aid of Eutectics
Authors: WATTS ARTHUR S.
Published: June 2006

Published equilibrium eutectics and other low‐temperature invariant points were investigated regarding deformation temperatures and rates. Their solubility in dilute acid, alkali, and phosphate solutions was also studied, and the one showing no solubility and the lowest deformation temperature was chosen as the center of the deformation series in each of the alkali‐alumina‐silica systems. The KAS, LAS, and NAS deformation eutectics were assembled in a triaxial system in which fusion temperatures and rates were determined, and the deformation eutectic was thus determined. Similar data were developed on combinations of the individual alkali eutectics and the lead‐alumina‐silica deformation eutectic reported in Part I of this study. The deformation eutectic of the combined alkali series and the lead‐alumina‐silica eutectic were combined in a series and the deformation eutectic was determined.
Efflorescence Resulting from Pyrite in Clay Raw Materials
Authors: BROWNELL WAYNE E.
Published: June 2006

In opening this investigation on the effect of pyrite on the efflorescence of structural clay products, the oxidation behavior of this sulfide was studied. The slow oxidation rate and the evolution of 2 moles of sulfur dioxide for every mole of pyrite present combined to make this impurity the major source of efflorescing salts. The retention of part of the sulfur dioxide by the clay material and the subsequent efflorescence tendency were found to depend on the composition, on the concentration of sulfurous gases, on the temperature of firing, on the time of firing, and on the duration of exposure to sulfur dioxide in the manufacturing process. The conditions necessary to reduce efflorescence from this source are described. The use of ammonium chloride to assist in the control of efflorescence was studied in detail.
Ultra Low Loss Ceramic Dielectrics
Authors: BUNAG M. M. , KOENIG J. H.
Published: June 2006

The object of this research was to develop ultra low loss ceramic dielectrics. The possible causes of the dielectric loss of ceramic bodies were first analyzed theoretically. Experimental bodies, designed on the basis of this analysis, provide for ultra low dielectric loss.
Refractory Compositions Based on Silicon‐Boron Oxygen Reactions
Authors: RIZZO H. F. , WEBER B. C. , SCHWARTZ M. A.
Published: June 2006

The nature and properties of a novel refractory material formed by reacting silicon and boron in air are described. The resulting material consists of free silicon and a new compound, SiB, dispersed in a borosilicate matrix. This refractory is stable in air to temperatures exceeding 1550°C., is thermal‐shock resistant, and has a low density.
Determination of the Cryolite‐Alumina Phase Diagram by Quenching Methods
Authors: FOSTER PERRY A.
Published: June 2006

The phase diagram of the system cryolite‐alumina, from 0 to 18.5% alumina, was determined by quenching techniques. No compounds appeared and no solid solubility was detected on either side of the eutectic. The eutectic point was established at 10.5 weight % alumina at 961°C.
Reaction Sequence and Structural Changes in Cordierite Refractories
Authors: Sorrell Charles A.
Published: June 2006

In order to determine temperatures of mullitization and cordierite formation, to outline the reaction sequence by which cordierite is formed, and to determine the effects of prolonged heating on cordierite development and structure, two separate series of experiments were performed. Specimens were fired for 1 hour at temperature intervals between 1000° and 1360°C. and analyzed for cordierite and mullite by X‐ray diffraction for the purpose of correlation with differential thermal analyses. Specimens were also fired at four different temperatures for periods of 1 to 192 hours and analyzed by X‐ray diffraction for cordierite content and structural changes. Mullitization occurred by exothermic reaction at 1267°C. Endothermic peaks at 1238° and 1330°C. are attributed to the formation of cordierite. Prolonged‐heating studies indicated that a progressive change takes place in cordierite by which a metastable hexagonal form is converted with time, through all intermediate stages, to the orthorhombic form which is stable at that temperature. Temperature was apparently the critical factor in cordierite development, time being of greater importance at lower temperatures.
Radiation Dosimeter Glasses
Authors: PAYMAL J. , BONNAUD M. , CLERC P. Le
Published: June 2006

Ionizing radiations produce visible colors in glasses containing certain multiple valence ions. The coloration, which is dependent on the radiation dose, is generally unstable. Combinations of certain ions can produce glasses with sufficient color stability to be used as dosimeters. Combinations of Mn‐Fe, Mn‐V, and Mn‐V‐Fe were studied. The response of glasses containing Mn‐V‐Fe was independent of the intensity of radiation and they may be used in the range between 105 to 2 × 107 roentgens.
Liquid us Curves in the Quaternary System NaF—AIF3—CaF2—Al2O3
Authors: FOSTER PERRY A.
Published: June 2006

THE electrolyte that is employed in the commercial production of aluminum generally consists of a fused mixture of cryolite, aluminum fluoride, calcium fluoride, and alumina. The aluminum fluoride is added to alter the cryolite ratio (3NaF/AlF3)* from the stoichiometric value of 1.5 to some lower value. Calcium fluoride is added to permit lower operating temperatures. Typically, the calcium fluoride content of the commercial electrolyte is usually between 7 and 9%. Alumina, of course, is continually being consumed in the production of aluminum. Periodic additions of alumina to the cell maintain the level between 2 and 50%.
Glass‐Migration Mechanism of Ceramic‐to‐Metal Seal Adherence
Authors: COLE S. S. , SOMMER G.
Published: June 2006

The basic mechanism of adherence in high‐alumina ceramic‐to‐metal sealing has been studied. A sealing mechanism has been established which involves the migration of the glassy phase of the high‐alumina ceramic into the interstices of the molybdenum‐based coating. The study was conducted on 94 and 99% aluminas, using molybdenum‐manganese, molybdenum‐titanium, and pure molybdenum metallizing compositions. The possibility of the formation of chemical compounds by either the molybdenum or the added metals has also been studied. A means of isolating and identifying any reacted or migrated phases has been developed.
Experimental and Theoretical Comparison of Radiation Conductivity Predicted by Steady‐State Theory With That Effective Under Periodic Temperature Conditions
Authors: CHARNOCK H.
Published: June 2006

The use of the steady‐state radiation conductivity, calculated from the high‐temperature absorption coefficients, to describe a periodic temperature change within a large volume of glass is investigated. Analysis shows that this steady‐state effective conductivity can be thus used, provided the amplitude and frequency of the temperature variation are small enough. These conditions are shown to have been fulfilled at the higher temperatures used in the experimental investigation. The general equations presented provide a basis for testing the assumption that the steady‐state radiation conductivity can be used to describe any transient temperature change.
Control of Dielectric Constant and Loss in Alumina Ceramics
Authors: ATLAS LEON M. , NAGAO HIKARU , NAKAMURA H. HENRY
Published: June 2006

The dissipation factors and dielectric constants of alumina ceramics containing less than 100 ppm of impurities and of specimens doped with Si, Ti, Ca, Mg, Fe, and Cr ions were measured in the region 102 to 8.5 × 109 cps and 25° to 875° C. Multiple regression analysis of the data at 500° C and 106 cps showed a linear relation between impurity concentration and tan δ, with a correlation coefficient of 0.93. Si ions caused the greatest rise of tan δ, Mg and Ti were second, Ca third, and Cr and Fe had no significant influence. These effects diminished with rising frequency and became negligible in the microwave region. Activation energies of conduction for pure and doped alumina were estimated from measurements of δ at 105 cps and 500°C. Values between 1.2 and 1.6 ev were calculated for all compositions except the one containing Mg2+, for which 2.0 ev was obtained. At low frequencies, the dielectric constant (k′) rose exponentially with temperature, reflecting a similar rise in the number of free charge carriers contributing to interfacial polarization. At higher frequencies the temperature variation of k′ fell to a shallow positive slope of about 120 ppm per °C. This coefficient was not influenced by low concentrations of impurities but could be effectively compensated without excessive loss by additions of 10 to 20% SrTi03.
Studies of Early Stages of Paste Hydration of Cement Compounds, I
Authors: CHATTERJI S. , JEFFERY J. W.
Published: June 2006

The paste hydration of C4AF with and without the addition of lime and/or gypsum was studied by means of electron‐optical and X‐ray diffraction techniques. It was found that in the paste hydration of C4AF iron did not separate out but remained in the structure of the hydrated compounds, probably substituting for aluminum. In a neat paste of C4AF and H2O, at first di‐ and tetracalcium aluminate hydrate crystals formed, but later cubic C3AH6 crystals appeared. In the presence of Ca(OH)2, C2AHx crystals did not form; otherwise the course of the reaction was the same as without lime. Any CO2 present formed monocarboaluminate. When gypsum alone was present, ettringite crystals first appeared which later changed to monosulfate hydrate. In the presence of both lime and gypsum, the reactivity of C4AF was much reduced. Ettringite crystals were somewhat stabilized by lime. The formation of monocarboaluminate was hindered in the presence of gypsum.
Preparation and Properties of Spinel Made by Vapor Transport and Diffusion in the System MgO‐AI2O3: II, In Hydrogen and Argon at Medium Pressures and in Vacuum
Authors: NAVIAS LOUIS
Published: June 2006

In a previous investigation it was found that a spinel layer was formed uniformly over the surface of sapphire when heated at 1500O to 1900°C in the presence of magnesia at 1 atm of hydrogen. Experiments of a similar nature were performed at reduced pressures (H2, 20 to 30 cm Hg; argon, 30 cm Hg; and in vacuum) in the same temperature range. Sapphire specimens were placed in enclosed periclase crucibles and on top of these crucibles, and the growth of spinel on the sapphire was examined. Enclosed specimens in vacuum gave the heaviest layer of spinel, equal to that obtained at 1 atm of hydrogen (21 mils at 1800°C in 6.4 hours).
Phase Relations in the Ternary System Fe2O3—FeO—YFeO3
Authors: VAN HOOK H. J.
Published: June 2006

Equilibrium data are presented for the ternary system Fe2O3–FeO–YFeO3 in ambient atmospheres of air, oxygen, and carbon dioxide at melting temperatures. The temperature range for the coexistence of yttrium‐iron garnet and oxide liquid decreases with decreasing oxygen partial pressure from 127°C in oxygen to 86° C in air to 28° C in carbon dioxide. In addition, the composition of the garnet phase crystallizing from these melts changes with variations of temperature and oxygen pressure. The experimental data are discussed in terms of a polythermal‐polybaric model of the system. Some conclusions are drawn as to the limiting conditions in different atmospheres for the growth and the resulting composition of yttrium‐iron garnet crystals in equilibrium with ternary oxide liquids.
Properties of Aluminoborate Glasses of Group II Metal Oxides: II, Electrical Properties
Authors: HIRAYAMA CHIKARA
Published: June 2006

The dc resistivities and dielectric properties at 0.060 to 100 kc and temperatures of 100° to 500° C have been determined for the Group II aluminoborate glasses. These glasses have resistivities as high as 1011.5 ohm‐cm at 450°C and activation energies ranging from 26 to 42 kcal per mole. The covalent character of the Group II‐B aluminoborates is demonstrated.
Thermal Conductivity of Anisotropic Solids at High Temperatures—The Thermal Conductivity of Molded and Pyrolytic Graphites
Authors: VARDI JOSEPH , HOCH MICHAEL
Published: June 2006

A method has been developed for the determination of the thermal conductivities of anisotropic solids under conditions of two–dimensional, steady–state heat conduction in a cylinder of finite length heated in vacuum by high–frequency induction and radiating heat to the surroundings. The method has been used to determine the radial thermal conductivity, Kr, and the axial thermal conductivity, Kz, of molded ZT‐type and pyrolytic graphite in the temperature range 1260° to 2200°K. For ZT‐type graphite, Kz/Kr=–0.101 + 2.002 × 10−4±T (1260°K < T < 2200°K); for pyrolytic graphite, Kz/Kr= 0.0376 at 1817°K.
Design and Performance of a High‐Temperature X‐Ray Diffractometer Furnace
Authors: SCOTT ROBERT K. , RUH EDWIN
Published: June 2006

A high‐temperature X‐ray diffractometer furnace that can be operated for extended periods at 2700°F in air has been constructed. The furnace has been operated successfully for shorter periods to 2800°F in air. Construction details are presented. This research tool has been used to follow the polymorphic inversions of silica from quartz in various high‐purity silica materials. The rate of inversion from quartz to cristobalite and tridymite has been found to be a function of crystallite size rather than of particle size.
Effect of Grain Boundaries on Plastic Deformation of Sodium Chloride
Authors: LONG STANLEY A. , McGEE THOMAS D.
Published: June 2006

Sodium chloride single crystals were joined at a melt zone with a hot‐wire technique to produce bicrystals of controlled crystallographic orientation. The plastic deformation properties of the bicrystals were measured in bending while the birefringence was observed with a petrographic microscope. The birefringence at the boundary was interpreted to indicate that significant deformation across the grain boundaries occurred. The stress required for deformation across the boundary was found to increase with increased angle between crystallographic axes. Twist boundaries were found to be more resistant than tilt boundaries. Behavior was consistent with the dislocation model for grain boundaries.
Energy of Grain Boundaries in Halite
Authors: MOMENT ROGER L. , GORDON ROBERT B.
Published: June 2006

Relative grain boundary energy measurements were made by the tracrystal method for [100] tilt boundaries in NaCl. The dependence of boundary energy on grain misorientation was similar to that in metals; however, the presence of significant torque term effects, i.e. dependence of the boundary energy on boundary orientation, is indicated. A method of measuring the relative magnitudes of the torque terms by applying a driving force to boundaries in bi‐crystals is described.
Etch Pits in BaTiO3 Single Crystals
Authors: ROTHWELL W. S.
Published: June 2006

Several new etch‐pit features in BaTiO3 single crystals are shown and discussed. Etch‐pit resolution was facilitated by using a 4% HNO3, 2% HF etchant and by prepolishing the crystals. Etch‐pit patterns in plastically deformed regions suggested that the preferred mode of slip in cubic BaTiOs is the 110, (110) direction. An etch‐pit structure possibly associated with twins was also observed.
Electron Probe Microanalysis of Ceramic‐to‐Metal Seals
Authors: REED LEONARD , HUGGINS R. A.
Published: June 2006

The electron microprobe technique was used to provide information on reactions occurring during the metallizing of alumina ceramics and their subsequent brazing to metal members. During a 1425°C metallizing firing, the refractory metal component of the metallizing paint sintered and bonded to, but did not measurably diffuse into, the oxide phases of the seal systems studied. Conversely the oxide components of the paint reacted with the alumina phase and interdiffused with the grain boundary phase of the ceramic. Copper and copper‐gold alloys with small amounts of nickel did not attack a copperplated molybdenum metallizing layer. Use of nickel plate is to be avoided with such brazes.
Chemical Strengthening of Polycrystalline Ceramics
Authors: KIRCHNER H. P. , GRUVER R. M.
Published: June 2006

The feasibility of strengthening polycrystalline ceramic bodies by low‐expansion solid solution surface layers was established. Failure, by shearing of the surface layers, was prevented by establishing gradual variations in composition and in thermal expansion coefficient which, in turn, resulted in gradual variations in stresses and reduction of the maximum shear stress. Titania ceramics were strengthened by TiO2‐SnC2 surface layers and alumina ceramics were strengthened by Al2O3‐Cr2O3 surface layers.
Oxidation of Magnesiowustite Single Crystals: II, Dependence on Temperature, Oxygen Pressure, and Crystal Composition
Authors: FICALORA P. J. , BRINDLEY G. W.
Published: June 2006

Single crystals of magnesiowustite (Mg,Fe)O containing up to 79 at.% Fe were prepared, and the proportions of ferrous and ferric ions were determined by chemical analysis. The rate of oxidation of individual crystals was studied at temperatures from 1000° to 1100°C and oxygen partial pressures of 2 × 10−1 to 3 × 10−6 atm. The reaction follows an equation based on diffusion through a product layer. The rate constant varies with temperature according to the Arrhenius relation, and activation energies range from 52 kcal/mole with 13 at.% Fe to about 17 to 20 kcal/mole when Fe atoms occupy one third or more of the cation positions. The rate constant is independent of oxygen partial pressure within the pressure range studied. Spectrographic measurements show that Fe in magnesiowustite occupies mainly octahedral sites, but some tetra‐hedral positions appear to be occupied. The mechanism of the oxidation reaction is considered.
Microstructure and Room‐Temperature Mechanical Properties of Hot‐Pressed Magnesium Aluminate as Described by Quadratic Multivariable Analysis
Authors: CHAY DONG M. , PALMOUR HAYNE , KRIEGEL W. W.
Published: June 2006

Polycrystalline spinel (MgA12O4), hot‐pressed in graphite dies, yielded densities ranging from ∼64 to ≊100% of theoretical. Average grain size of compacts varied from 4 to 125μ depending on hot‐pressing conditions. Room‐temperature mechanical properties also varied widely; average strengths for the 15 experimental combinations ranged from 3500 to 34,000 psi in bending and from 21,700 to 389,000 psi in compression, and Young's modulus ranged from 0.54 X lo7 to 3.5 X 107 psi. Variations in bulk density, average grain size, room‐temperature transverse and compressive strengths, and Young's modulus of elasticity were separately expressed as multiple quadratic regressions in terms of 1/T (temperature), In t (time), and P(pressure) over the hot‐pressing range 1227’to 1750°C, 5 to 320 min, and 1000 to 3000 psi. From these regressions, empirical equations expressing mechanical properties in terms of regression solutions of density and grain size were derived which statistically indicate a principal dependence on density and only a minor grain size dependence.
Fracture of Tempered Glass
Authors: BARSOM JOHN M.
Published: June 2006

The fracture of thermally tempered glass is discussed in terms Of both the stored elastic strain energy in the glass due to tempering and the elastic energy release rate Of crack extension, 9. The latter is used to obtain an analytical correlation between the maximum tensile stress and the average particle size at time of fracture. The theoretical predictions are supported by experimental data obtained for various glass thicknesses and temper levels.
Hemispherical Spectral Emittance of Selected Rare Earth Oxides
Authors: McMAHON W. R. , WILDER D. R.
Published: June 2006

The hemispherical spectral emittances for the sesquioxides of yttrium, samarium, gadolinium, erbium, thulium, and ytterbium are given for five wavelengths in the visible portion of the spectrum over the range of 1400° to 3000°K. A reflectance technique incorporating a carbon arc image furnace and a standard of reflectance was used in the determinations. The emittance of zirconium dioxide was measured to check the validity of the method.
Phase Diagrams for the Systems Si‐O and Cr‐O
Authors: JOHNSON R. E. , MUAN ARNULF
Published: June 2006

Equilibrium studies in the systems Si‐O and Cr‐O at high temperatures indicate that no stable intermediate compounds exist between the metals and the oxides, SiO2 or Cr2 O3, up to solidus temperatures. In both systems, there is a large concentration range of coexistence of two liquid phases above liquidus temperatures.
Neutron Damage in Single Crystal Aluminum Oxide
Authors: BARBER D. J. , TIGHE N. J.
Published: June 2006

Synthetic aluminum oxide crystals were irradiated with fast neutrons to a dose of 1.8 × 1020 nvt and examined by. transmission electron microscopy. As‐irradiated crystals contained damage on a fine scale, revealed by diffraction contrast, and showed a 28% increase in Knoop diamond hardness compared with unirradiated material. Annealing above 600° C decreased the hardness and caused the small defect clusters to grow, forming dislocation loops on [100] planes with 1/3(101) Burgers vectors. High temperature annealing caused the loops to interact to give dislocation segments. These tended to align with the (100) and (1120) directions, and some of them had 1/3(101) Burgers vectors. Grown‐in dislocations also began to climb but showed evidence of impurity pinning. Isolated platelike precipitates on [101] planes were observed in samples annealed at high temperatures. Possible effects of the observed damage on physical properties are considered; there is qualitative agreement between predictions and existing data.
Pressure‐Temperature Study of Sulfospinels
Authors: TRESSLER R. E. , HUMMEL F. A. , STUBICAN V. S.
Published: June 2006

Several new compounds with the formula AB2S4 were synthesized. Pressure‐induced polymorphism of the sulfospinels was investigated. The only spinels which transformed to the NiAs derivatives were those in which the A and B cations had unfilled d orbitals. Pressure‐temperature phase relations were investigated for a series of sulfochromites. At 600°C the transformation pressure decreased in the order MnCr2S4, FeCr2S4= CoCr2S4, NiCr2S4 (an NiAs structure at P= 1 atm). Sulfospinels which produced new high‐pressure phases were NiRh2S4, FeYb2S4, CrIn2, NiIn2S4, CoIn2S4, and MnIn2S4.
Effect of Water on Toughness of MgO Crystals
Authors: SHOCKEY D. A. , GROVES G. W.
Published: June 2006

It was possible to drive plastically blunted cleavage cracks through double cantilever beam specimens of impure MgO monocrystals in a series of small propagations. The forces required to propagate the cracks often defined a fairly constant apparent surface energy and provided an environment‐sensitive measure of toughness. Apparent surface energies between 1700 and 3100 ergs/cm2 were obtained on MgO crystals tested in air. Values of apparent surface energy obtained from crystals tested in a low water content environment agreed well with values obtained on the same specimens in air, suggesting that water vapor in laboratory air does not significantly affect the toughness of MgO. Specimens tested while immersed in water, however, were approximately 30% tougher than those tested in air and exhibited a faceted fracture surface in contrast to the relatively smooth fracture surface produced in air.
Ionic Conduction in Alkali and Thallium Silicate Glasses
Authors: OTTO KLAUS , MILBERG M. E.
Published: June 2006

Electrical conductivities of binary alkali and thallous silicate glasses have been measured as a function of composition, temperature, and frequency. The best approximation to the activation energy for dc conduction can probably be obtained by extrapolating its frequency dependence to zero frequency, although values obtained at frequencies below 2500 hz do not differ greatly from the dc values. The plot of activation energy for conduction against modifier content consists of two straight lines of different slope. For all the alkali silicate glasses the break in slope occurs near 25 mole % alkali oxide and at an activation energy near 14.7 kcal/mole. The slope of the line below 25 mole % alkali oxide is proportional to the alkali ion radius. The behavior of thallous silicate glass is similar but not identical to that of the alkali silicates. It is concluded that (1) the reported conduction behavior does not result primarily from phase separation, (2) the principal contribution to the activation energy is probably the work required for a mobile ion to pass through the glass network rather than to leave its initial position, and (3) a structural change independent of the nature of the modifier cation occurs near a modifier content of 25 mole %.
Low‐Frequency Grain‐Boundary Relaxation in Alumina
Authors: TURNBAUGH JERRY E. , NORTON F. H.
Published: June 2006

The internal friction spectrum of polycrystalline, sintered alumina was determined at 15 to 25 cps and 25° to 1550°C. Two relaxation mechanisms appeared to be operative. A high‐temperature relaxation interpreted as stemming from diffusion‐controlled grain‐boundary motion was dominant above 1150°C. Assuming a mean diffusion path of 10−4 cm gave a diffusivity of D = 5.2 × 10−2 exp (−52,000/RT) which was independent of impurity content. A lower‐temperature relaxation was observed in specimens of higher impurity content at 900° C. This relaxation reached a maximum but did not behave as a Debye‐type relaxation. Single‐crystal alumina exhibited neither of these relaxations.
Elastic Behavior of Arc‐Cast Zirconium Carbide‐Graphite Alloys
Authors: CARNAHAN R. D. , JANOWSKI K. R. , ROSSI R. C.
Published: June 2006

The Young's and shear moduli of arc‐cast zirconium carbide‐graphite alloys were measured as a function of graphite content and were found to depend strongly on the microstructure of the alloys. Attempts to fit several theoretical analyses to the data were unsuccessful. The simplified physical models from which these analyses were derived limit their usefulness in predicting elastic behavior for materials having complex microstructures.
Plasticity and Creep in Single Crystals of Zirconium Carbide
Authors: LEE D. W. , HAGGERTY J. S.
Published: June 2006

High‐temperature deformation in ZrC single crystals was studied. Seeded crystals were grown by a direct rf‐coupling floating‐zone process. Yield stresses were measured from 1080° to 2000°C as a function of stress axis orientation. The Burgers vector was shown to be parallel to the 〈110〉 axes by transmission electron microscopy. Slip was observed on {100}, {110}, or {111} planes, depending on the orientation of the stress axis; it always occurred on the most favorably oriented slip system. The dependence of steady‐state creep rate on the applied stress indicated that recovery occurred by a dislocation climb mechanism. Examination of the dislocation structure in deformed crystals by transmission electron microscopy supported this conclusion.
Mechanism of Formation of Zircon Stains
Authors: EPPLER R. A.
Published: June 2006

The mechanism of formation of iron‐zircon pink and vanadium‐zircon blue stains was studied, primarily by the marker technique. Reaction occurred at the site of the reactant ZrO2. The primary function of the mineralizer in these stains is to react with SiCK and to assist in its transport to the reaction site. Although the basic mechanism of formation of both stains is the same, important differences result from the physical properties of the dopants at reaction temperatures.
Compression Permeability of Al2O3 Cakes Formed by Pressure Slip Casting
Authors: FENNELLY TERRENCE J. , REED JAMES S.
Published: June 2006

The pressure gradient naturally effected across the cake on pressure casting can lead to pore‐character gradients and dimensional distortion if the cake is significantly compressible. The compressibilities of cakes formed on pressure slip casting of aqueous Al2O3 slips defiocculated with an organic polyelectrolyte were determined for applied pressures ≤500 psi. In general the compressibility decreased with increasing pressure. Improved deflocculation of slips from which cakes were formed drastically reduced the level and pressure dependence of compressibility; cakes cast from well‐deflocculated slips were insignificantly compressible. Specific resistances determined concurrently agreed well with results obtained previously in kinetic studies. Compression‐permeability behavior can serve as a quality control test for the slip casting of technical ceramics.
Adsorption of Water Vapor on E‐Glass
Authors: HUANG R. J. , DEMIREL T. , McGEE T. D.
Published: June 2006

The thermodynamics of a water‐vapor‐E‐glass system were studied by adsorption‐isotherm analysis. The seven isotherms completed were Brunauer type IV with permanent hysteresis. The first adsorbed water layer could not be removed by pumping, indicating permanent hydrolysis. Application of heat removed the remaining water to close the hysteresis loop. Calculation of isosteric heat of adsorption indicates that the adsorbed state is between the solid and the liquid states, equivalent to the loss of one vibrational and one translational degree of freedom. A new plot of energy vs thickness is proposed which describes the adsorption independent of surface area, as contrasted to the usual energy‐vs‐volume plot which was found to depend on surface area. A modified Clausius‐Clapeyron equation is proposed for computing the isosteric heat of adsorption.
Influence of Pseudo‐Alkali Cations on Network Depolymerization in Mixed‐Cation Germanate Glasses
Authors: RIEBLING E. F.
Published: June 2006

Mixed‐cation germanate glasses that contained ≥69 mol% GeO2 and equimolar amounts of Na2O/K2O, Ag2O/Tl2O, Tl2O/K2O, or Ag2O/K2O were prepared. Densities, refractive indices, and infrared absorptions were measured and colors noted. In all glasses, the expected shift of the ir absorption to longer wavelengths is enhanced by the presence of the second cation. The mixed‐alkali glasses are less voluminous and the mixed‐cation glasses more voluminous than predicted. The mixed‐cation glasses in some cases also exhibit more intense colors than anticipated and deviations of the refractive index from additivity. These results are interpreted in terms of slight differences in the mode of network depolymerization which appear to be caused by the polarizing nature of Tl+ and Ag+
Interactions Between Cement Minerals and Hydroxycarboxylic‐Acid Retarders: IV, Morphology of the Aluminosalicylate Complex*
Authors: DIAMOND SIDNEY
Published: June 2006

The morphology of the particles of aluminosalicylate complex precipitated from salicylic acid solution by tricalcium aluminate (C3A) was examined by scanning electron microscopy. Agglomerations of small (0.3 μm) equiaxed particles are precipitated from concentrated solutions and are accompanied by peculiar hexagonal prismatic “crystallites” with rounded ends thought to be Ca(OH)2. In more dilute solutions distorted hexagonal plates of C4AH13‐type compounds are also formed.
Systems of Na‐Fe‐SiO2 Glasses and Steel: I, Wetting and Adherence
Authors: BHAT VASANTH K. , MANNING CHARLES R.
Published: June 2006

Wetting behavior of molten Na2O‐Fe2O3‐SiO2 and Na2O‐FeO‐SiO2 glasses on very‐low‐carbon steel at 900°C in purified Ar was studied. The steel surface was dry‐polished and cleaned by ion bombardment. Glass frit was then placed on the metal, and the system was introduced into the furnace without exposure to air. Dynamic advancing and receding contact angles were measured. Shear (push‐off) tests were performed on the glass‐steel composite at room temperature to determine adherence. The equilibrium contact angles were obtained from the arithmetic mean of the final advancing and receding angles. As the Fe oxide content of the glasses increased, the degree of wetting improved; Fe3+ was more effective than a combination of Fe3+ and Fe2+ in improving the wettability. Glasses very nearly saturated with Fe oxide exhibited high adherence values and chemically adhered to steel.
Microstructural Development in Partially Stabilized ZrO2 in the System CaO‐ZrO2
Authors: GREEN DAVID J. , MAKI DENNIS R. , NICHOLSON PATRICK S.
Published: June 2006

The microstructures of 3 zirconias partially stabilized with CaO were investigated using scanning electron microscopy and qualitative and quantitative X‐ray analysis. The structure was closely related to the heat treatments involved in fabrication. A bimodal structure with small grains of pure ZrO2 dispersed along the grain boundaries of larger cubic solid‐solution grains developed during slow cooling from 1850° to 1300°C. The presence of a liquid phase greatly enhances the growth of the pure ZrO2 phase. An anneal at 1300°C induces precipitation of fine ZrO2 particles within the solid‐solution grains. The relative mechanical strengths of the materials are explained in terms of the weakening of the grain boundaries associated with the transformation of the grain‐boundary phase on cooling.
Index of Reaction—A Unifying Concept for the Reaction Kinetics of Powders
Authors: TAPLIN JOHN H.
Published: June 2006

The index‐of‐reaction equation, dF/d(tz) = k'(1‐βF)m, generalizes the linear, competing‐nuclei, Austin‐Rickett, limited‐extent, and other kinetic equations for the reaction of solids. It is also a good approximation for both parabolic kinetics and simple diffusion.
Empirical Relation Between Self‐Diffusion and Electrical Conduction in Mixed‐Alkali Glasses
Authors: VARSHNEYA A. K.
Published: June 2006

An empirically modified Nernst‐Einstein‐type equation is proposed to relate the electrical conductivity of mixed‐alkali glasses to the self‐diffusivities of the alkali ions. Conductivities were calculated for 3 glass systems using measured self‐diffusivities and the proposed equation. These calculated conductivities and those measured directly agree quite well.
Properties of Surface Barrier Layer Formed on a Semiconducting BaTiO3 Ceramic
Authors: WAKINO KIKUO
Published: June 2006

A mechanism for formation of a capacitive layer is described. Copper was vacuum‐evaporated onto the surface of a semiconducting BaTiO3 ceramic, Ag paste was applied to this layer, and the capacitor was fired in air. A transition layer ∼3 μm thick was formed between the electrode and the n‐type semiconducting ceramic; this layer exhibits characteristics typical of a p‐n junction.
Strength and Durability of a Glass‐Ceramic Containing Spodumene Crystals
Authors: KAY J. F. , DOREMUS R. H.
Published: June 2006

A glass‐ceramic containing β‐spodumene crystals showed little decrease in fracture strength between liquid‐nitrogen temperature and room temperature, and the strength was not reduced by water in the surrounding air. Its delayed failure was less than that of other glasses and crystalline ceramics. These results are attributed to the low reactivity of β‐spodumene crystals with water. Reasons for this lower reactivity are discussed in terms of the structure of the crystals.
Effect of Test Environment on Stress‐Corrosion Susceptibility of Glass
Authors: RITTER JOHN E. , LAPORTE R. P.
Published: June 2006

The stress‐corrosion susceptibility of abraded and acid‐polished soda‐lime and borosilicate glasses in test environments of 6N NaOH, distilled water, and 6N HCI was measured by dynamic fatigue techniques. Dynamic‐fatigue data for these glasses agree well with crack‐velocity data for the water and 6N NaOH environments. The lack of agreement in the 6N HCI environment suggests that the failure mechanism for glass in HCI is not simply crack propagation by stress corrosion. The agreement in failure predictions based on strength and crack‐velocity data in 6N NaOH and water suggests that either set of data may be used for effective design calculations; however, caution should be used when basing strength calculations on crack velocity data in 6N HCI.
Bubble Formation in Glass by Reaction with Silicon and Silicon‐Germanium Alloys
Authors: EAGAN ROBERT J. , JONES GARY J.
Published: June 2006

The cause of bubbles at a glass/Si, glass/SiGe interface, which form when some glasses are fused on Si or SiGe, was determined. Water, bonded as OH groups in the glass, was reduced by the Si at high temperatures to form H2. The gas released by this reaction formed bubbles only in those glasses with low permeability to H2.
Electrical Resistivity Surface for FeO‐Fe2O3‐P2O5 Glasses
Authors: VAUGHAN JAMES G. , KINSER DONALD L.
Published: June 2006

The dc electrical properties and microstructure of x(FeO‐Fe2O3)‐(100 –x)P2O5 glasses were investigated up to a maximum of x= 75 mol%. Results indicate that, in general, the minimum resistivity of the glass does not occur at equal Fe2+] and Fe3+] concentrations, although for the special case where x= 55 mol% the minimum does occur at Fe2+]/Fe total = 0.5, as reported by other investigators. Evidence presented shows that the position of the minimum resistivity is a function of total iron content. The minimum shifts to glasses richer in Fe2+] at higher total iron concentrations.
Influence of Irradiation Temperature, Burnup, and Fuel Composition on Gas Pressure (Xe, Kr, CO, CO2) in Coated Particle Fuels
Authors: HORSLEY G. W. , WELDRICK G. J. , TURNBULL J. A. , SHIPP R.
Published: June 2006

Relations have been derived from gas analyses of irradiated PyC‐coated UO2 fuel particles that enable the quantity of permanent rare gas (Xe+Kr) released within the particle to be predicted from known conditions of irradiation temperature, time, and burnup. The experimentally determined influence of fissions in uranium and plutonium isotopes on the growth of intraparticle CO + CO2 pressure is discussed and its elimination by an appropriate getter is described.
Analysis of Structural Relaxation in Glass Using Rate Heating Data
Authors: DEBOLT MARY ANN , EASTEAL ALLAN J. , MACEDO P. B. , MOYNIHAN CORNELIUS T.
Published: June 2006

A method was developed to determine the kinetic parameters controlling structural relaxation in the glass transition region from data acquired during continuous heating or cooling. The nonexponential character of the relaxation is accounted for by assuming an equilibrium isothermal relaxation function of the form exp [−(t/Toe)ß], where Toe is a relaxation time and 0<β1. The data are linearized using the method of Narayanaswamy, and the continuous temperature variation during heating or cooling is dealt with by invoking the superposition principle. The analysis yields the kinetic parameters A, the relaxation‐time preexponential term; Δh★, the relaxation‐time activation enthalpy; x, a term describing the relative effects of temperature and structure on the rate of relaxation; and β. The method was applied to analysis of the variation of the enthalpy of vitreous B2O3 during rate heating through the transition region following rate cooling through the same region at a variety of rates.
Fracture Toughness of Al2O3 with an Unstabilized ZrO2Dispersed Phase
Authors: CLAUSSEN NILS
Published: June 2006

The fracture toughness of Al2O3 is considerably increased by the incorporation of fine monoclinic ZrO2 particles. Hot‐pressed composites containing 15 vol % ZrO2 yield Klcvalues of ∼ 10 MN/m3/2, twice that of the A12O3 matrix. It is hypothesized that this increase results from a high density of small matrix microcracks absorbing energy by slow propagation. The microcracks are formed by the expansion of ZrO2during the tetragonal → monoclinic transformation. Since extremely high tensile stresses develop in the matrix, very small ZrO2 particles can act as crack formers, thus limiting the critical flaw size to small values.
Subsolidus Equilibria in the System BaO‐TiO2‐GeO2
Authors: GUHA J. P.
Published: June 2006

Subsolidus phase relations in the system Ba0‐Ti02‐Ge02 were investigated using conventional solid‐state reaction techniques and X‐ray powder diffraction. The existence of 2 ternary compounds, BaTiGe309 and BazTiGeZ08, was confirmed and their X‐ray crystallographic data are presented. The compound BaTiGe309 has a lower limit of stability at 1135°C and melts incongruently at 1232°C; Ba2TiGe2O2 melts congruently at 1228°C. Subsolidus compatibility relations in the ternary system were established and tie lines between the various phases which constitute a total of 12 compatibility triangles at 1000°C are shown in a subsolidus phase diagram.
Electrical Conduction in Single‐Crystal Thallic Oxide: I, Crystals “As‐Grown” from the Vapor in Air
Authors: SHUKLA V. N. , WIRTZ G. P.
Published: June 2006

Thallic oxide, “T12O3,” has been shown to be a degenerate n‐type semiconductor with resistivity varying from 60 to 150 μΩ‐cm over the range 4° to 900°K. The carrier concentration was 7 × 1020 cm−3 and is temperature independent. Room‐temperature Hall mobility was 105 cm2 V−1 s−1, increasing to 130 cm2 V−1 s−1 below 70°K. Donor states were shown to be native defects, probably oxygen vacancies.
Measurement of Mobility and Zeta Potential of Beta‐Alumina Suspensions in Various Solvents
Authors: KENNEDY JOHN H. , FOISSY ALAIN
Published: June 2006

Mobilities and zeta potentials of β‐alumina particles have been measured in 1‐pentanol, nitromethane, and dichloromethane media. The effects of grinding, aging, water content, and acid solute content were observed; all of these variables were critical. The charge on the β‐alumina particles could be either positive or negative, depending on the suspension conditions.
Phase Relations in the System Si3N4‐SiO2‐MgO and Their Interrelation with Strength and Oxidation
Authors: LANGE F. F.
Published: June 2006

Phase relation studies of Si3N1, SiO2, and MgO have established three important subsolidus tie lines, viz. Si3N4‐MgO, Si3N4‐Mg2SiO4, and Si2N2O‐Mg2SiO4 for nonoxidizing fabrication conditions. Strength measurements at 1400°C show that optimum strengths are obtained for compositions approaching the Si3N4‐MgO and Si3N4‐Si2N2O tie lines and that inferior strengths are obtained for compositions approaching the Si3N4‐Mg2SiO4 tie line. Oxidation measurements at 1375°C show that the oxidation kinetics depend on the content of MgO and Mg2SiO4 phases. Optimum oxidation resistance is observed for compositions approaching the Si3N4‐Si2N2O tie line. Strength and oxidation results are discussed with regard to phase equilibrium considerations.
Energy Levels of Donor and Acceptor Dopants and Electron and Hole Mobilities in α‐Al2O3
Authors: TIKU S. K. , KRÖGER F. A.
Published: June 2006

The relation between activation energy of conduction and the position of energy levels of donors and acceptors is discussed. Level positions of donor and acceptor dopants in A12O3 at 1600°C are recalculated from published data. Carrier concentrations calculated from the new level positions lead to carrier mobilities with values scattering around 1 cm2/V·s, leaving the question of which conduction model is preferable unanswered. Relations of acceptor level positions with values of ionization potentials, redox potentials, and charge transfer bands are used to predict level positions for other transition metal acceptors.
Phase Equilibria in the System AlN‐Si3N4‐Be3N2
Authors: SCHNEIDER G. , GAUCKLER L. J. , PETZOW G.
Published: June 2006

An isothermal section of the system AlN‐Si3N4‐Be3N2 was investigated at 1760°C. The equilibrium relations involve the previously known compounds of the system Si3N4‐Be3N2 and a newly found complete solid solution between AlN and BeSiN2.
Acoustic Surface Wave Measurements of Surface Cracks in Ceramics
Authors: KHURI‐YAKUB B. T. , KINO G. S. , EVANS A. G.
Published: June 2006

Acoustic surface wave techniques were devised for detecting and characterizing surface cracks in ceramics. These techniques detect cracks at least as small as 60 μm deep on polished samples. The crack detectability was diminished by surface grinding, because of a background effect, attributed to backscattering from surface microcracks. Preliminary experiments conducted on turbine blades indicated that the techniques can be applied to components of complex shape.
Electrical Conductivity of Pure and Fe‐Doped Magnesium‐Aluminum Spinel
Authors: WEEKS R. A. , SONDER E.
Published: June 2006

The electrical conductivity of nominally pure and Fe‐doped MgAl2O4 spinel was measured at 700 to 2000 K. The results for pure stoichiometric spinel can be fitted by exponential expressions with different activation‐energy parameters in three ranges of temperature. The conductivity of a sample containing 0.1% iron is the same as that of pure samples when the iron is in the Fe2+ form; it increases approximately a factor of two when the ion is in the Fe3+ form. The results are consistent with ionic conduction due to motion of cation vacancies.
The Set Point of Glass in Glass‐to‐Metal Sealing
Authors: VARSHNEYA ARUN K.
Published: June 2006

The stress‐relaxation theory of glass was extended to calculate the net strains developed in a glass‐to‐metal seal which, in turn, was used to calculate a set point of glass which can be shown to depend not only on the cooling rates but also, to some extent, on the metal used. The importance of the knowledge of the glass expansion in the transition range is recognized. Calculated net strains reveal that for those glass‐to‐metal sealing operations where rapid cooling is used, the calculated effective differential expansion differs significantly from the conventionally quoted 25° to 300°C value. An empirical equation is proposed to relate the set point primarily to the seal cooling rate.
Preparation of Ultrafine SiC Particles by Gas Evaporation
Authors: Ando Yoshinori , Uyeda Ryozi
Published: June 2006

A new method for preparing ultrafine powder of SiC is proposed. A carbon rod is mounted vertically with a block of silicon at the bottom of the system. The apparatus is held in rarefied inert gas and heated by an electric current. The SiC produced by the heating then evaporates forming a smoke, the particles of which are β–SiC <100 nm in diam.
Stabilization of β‐Bi2O3 by Sb2O3 Doping
Authors: Miyayama Masaru , Terada Hiroya , Yanagida Hiroaki
Published: June 2006

The metastable β form of bismuth sesquioxide was obtained by doping antimony oxide. The solubility of antimony was 4 to 10 at. %in β specimens, where more than 75% of the antimony atoms were valenced at 5+.
Fabrication of Translucent ZrO2 Film by a Modified Doctor Blade Method
Authors: Yanagida Hiroaki , Takata Masasuke , Nagai Masayuki
Published: June 2006

Dense, translucent ZrO2 (stabilized by Y2O3) films were made by a modified doctor blade method. Loosely coagulated ceramic powders left after decomposition of methylcellulose film were pressed onto polystyrene films to densify the powder compact. The films were heated at 1700°C in air. The thickness of the films was ∼100 μm. Very few grain boundaries appeared along the direction perpendicular to the film surface.
Orientation Effects on the Thermal Diffusivity of Hot‐Pressed Silicon Nitride
Authors: Zlegler G. , Bentsen L. D. , Hasselman D. P. H.
Published: June 2006

The thermal diffusivity perpendicular to the hot‐pressing direction for a variety of silicon nitrides was found to be higher than parallel to the hot‐pressing direction. This effect was attributed to the preferred elongation of the β‐grains perpendicular to the hot‐pressing direction.
Vapor‐Phase Hydration of Submicrometer CaO Particles
Authors: BERUTO DARIO , BARCO LUIGI , BELLERI GABREELE , SEARCY ALAN W.
Published: June 2006

Reaction of water vapor at 25°CC with CaO powder of either high or low surface area yields Ca(OH)2 with broad XRD peaks. Relative rates of reaction of these hydroxides with CO2 at 250°CC depend mainly on the sample surface areas per unit weight. SEM observations show that the exterior shapes of porous 1 to 30 μm particles of CaO formed by decomposition in vacuum of CaCO3(sr‐CaO) or Ca(OH)2 (h‐CaO) are only slightly changed when they are converted to Ca(OH)2, except for surface roughening, which increases with time of exposure to water vapor. The N2 adsorption‐desorption isotherms of h‐CaO and sr‐CaO, and of their hydration products, are used to calculate the average particle expansion, the probable pore shapes, and the changes in pore‐size distributions that accompany the reaction. These data show that the reaction causes expansion perpendicular to ulterior surfaces of the porous powder particles. A possible mechanism is suggested. Both h‐CaO and sr‐CaO dissolve in liquid water to yield Ca(OH)2 by subsequent precipitation.