bluuebunny/crossref_metadata_2025 huggingface dataset:
Variations of Surface Tension with Body and Surface Concentrations
Authors: BESTUL A. B.
Published: June 2006

Mathematical derivatives of surface tension with body concentration and with surface concentration are examined analytically for solutions in which the activity coefficient of the solute is taken as a linear function of solute concentration in the body, and as fixed at unity in the surface. As an approximation, the surface concentration is taken as a uniform value maintained throughout a surface domain extending from the geometrical surface to a fixed depth into the solution, at which the concentration changes as a step function to the body concentration. The writer accepts previous experimental and theoretical conclusions that for an ionic solute the increment of surface tension per surface ion increases with decreasing ionic radius. The Debye‐Hückel equation for the activity coefficient of electrolytes predicts that the activity coefficient of an ionic solute increases with increasing ionic radius. Experimentally, this predicted dependence and its reverse are observed about equally often. For those solutes which behave according to the Debye‐Hückel prediction it is found that a negative derivative must exist between the derivatives of surface tension with body and with surface concentration at sufficiently high values of the increment of surface tension per surface ion.
The Glassmelting Process: II, Glass Structure and the Effects of “Melting History” on Glass Properties
Authors: McKINNIS CHARLES L. , SUTTON JOHN W.
Published: June 2006

Interpretations are made of experimental and practical aspects of glass structures in terms of a postulated distribution of anionic structures in glass. The existence of effects determined by the “melting history” of a glass is demonstrated by specially programmed experiments on viscosity and tensile strength. The viscosity curve of glass melted at a relatively low temperature lies above that for the same glass which had been previously melted at high temperatures. The two curves merge in the high‐temperature region. It also is found that the tensile strength of glass fibers increases as the maximum melting temperature increases.
Precise Determination of the 3CaO·SiO2 Cells and Interpretation of Their X‐Ray Diffraction Patterns
Authors: YAMAGUCHI GORO , MIYABE HISAKO
Published: June 2006

The cell dimensions of pure triclinic 3CaO·SiO2 and monoclinic 3CaO·SiO2 solid solution (54CaO·16SiO2·Al2O3·MgO) were determined and the powder diffraction patterns were indexed by the method of precise measurement of the spacings. The lattice constants are expressed in terms of triclinic or monoclinic cells corresponding to pseudo‐orthorhombic cells derived from Jeffery's trigonal cell. The apparent lattice constants for pure 3CaO·SiO2 are a= 12.195 a.u., b = 7.104 au., c = 25.096 a.u., α= 90°, β= 89°44’γ= 89°44′; for 54CaO·16SiO2.‐Al2O3MgO, a= 12.246 a.u., b = 7.045 a.u., c = 24.985 a.u., β= 90°04′. Precise lattice constants of Jeffery's monoclinic lattice for 54CaO.‐16SiO2‐Al2O3·MgO are derived as a = 33.091 a.u., b = 7.045 a.u., c = 18.546 a.u., β= 94°08′. High‐temperature X‐ray patterns showed that pure triclinic 3CaO·SiO2 transformed to a monoclinic form at about 920°C. and then to a trigonal form at about 970°C. Monoclinic 54CaO.16SiO2·Al2O3–MgO transformed to trigonal at about 830°C. These transitions were reversible and reproducible and were accompanied by only slight deformation of the structure forms.
Thermal Conductivity in Ceramic‐Metal Laminates
Authors: FRANCIS R. K. , TINKLEPAUGH J. R.
Published: June 2006

Thermal conductivity measurements were made on a forsterite‐stainless steel laminate series. Values were measured parallel and perpendicular to the laminas and then compared with results calculated from electrical analogy relations. Thermal conductivity values measured parallel to the laminas were approximately 12% higher than calculated values. Thermal conductivity values measured perpendicular to the laminas were approximately 10% lower than calculated values. Interfacial conductivity in the laminates was considered as measured perpendicular to the laminas, but a value consistent for all laminates measured was not obtained.
Electrical Properties of Lead‐Barium Niobates and Associated Materials
Authors: BAXTER P. , HELLICAR N. J.
Published: June 2006

The electrical properties of materials in the system lead‐barium niobate are described. Particularly useful materials are obtained when between 25 and 50 mole % of lead niobate is replaced by barium niobate. Materials with a 40 to 45 mole % replacement have permittivities of more than 1500 and radial electromechanical coupling coefficients of more than 0.35, but the Curie temperature is then only about 250°C, the minimum value obtained in the system. Higher Curie temperatures are accompanied by somewhat lower values of permittivity and coupling coefficient. An indication is given of the effects of several other additives on the properties of lead niobate, and it is shown that barium‐strontium niobates are only weakly ferroelectric at room temperature.
The System Iron Oxide‐TiO2‐SiO2 in Air
Authors: MacCHESNEY J. B. , MUAN ARNULF
Published: June 2006

Phase relations at liquidus temperatures in the system iron oxide‐TiO2‐SiO2 have been determined in air. The equilibrium existence of the crystalline phases magnetite (ss), hematite (ss), pseudobrookite(ss), rutile(ss), and silica (tridy‐mite or cristobalite) has been established. Three isobaric eutectic points are formed by the intersections of quaternary liquidus univariant lines of the system Fe‐Ti‐Si‐O and the 0.21 atmosphere isobaric surface. The liquid misci‐bility gaps present in the bounding “binary” systems iron oxide‐Si02 and TiO2‐SiO2 extend across the composition triangle representing the “ternary” system iron oxide‐TiO2‐SiO2. Liquidus temperatures decrease within the two‐liquid region from approximately l<57Qa C. in the system iron oxide‐SiO2 and 1780°C. in the system Ti(VSiO2 to 1540°C. at the cristobalite‐rutile(ss) boundary curve which bisects the two‐liquid region. Paths of equilibrium crystallization of representative mixtures are discussed with reference to a simplified projection into the plane FeOFe2O3‐TiO2‐SiO2 as well as in terms of the tetrahedron representing the system FeO‐Fe2O3‐TiO2‐SiO2.
Causes of Chipping of a Stiff‐Mud Facing Brick
Authors: WEST R. R. , FLEISCHER D. H. , HECHT N. , HOSKYNS W. R. , MUCCIGROSSO A. , SCHELKER D. H.
Published: June 2006

A smooth‐textured face brick manufactured from a buff‐burning fire clay was studied to determine causes of chipping during handling. An impact test was devised to evaluate the chipping resistance of brick and specimens prepared in the laboratory. The cause of chipping is related to a high degree of orientation of plate like particles produced by friction between the clay column and the die during extrusion. Mullite needles are stratified at the surface during firing as they are formed in the plane of the oriented kaolinite particles. Weak interlayer bonding forces at the surface of the brick allow chips to be removed with the application of low impact forces. Improvements in chipping resistance were observed when the particle size of the ground clay was increased or when calcined clay was added to the raw mixture to reduce the number of fine plate like particles which are more easily oriented in one plane than are the larger more equidimensional particles. Lengthening the time at the maturing temperature during firing and decreasing the cooling rate also improved the chipping resistance of the brick.
Structure and Properties of Rare‐Earth and Yttrium Hard Metals
Authors: BINDER IRA
Published: June 2006

This paper is a review of the preparation, structures, and properties of rare‐earth and yttrium hard metals, with emphasis on borides and silicides. A literature review includes some of the writer's work previously reported.
Technology of Spinel‐Bonded Periclase Brick
Authors: EUSNER G. R. , HUBBLE D. H.
Published: June 2006

This study covers the development of a new basic brick with outstanding resistance to load deformation, slagging, and spalling. This brick is made of 92% high‐purity periclase and 8% high‐purity alumina. During firing for a ceramically bonded brick or in service for a chemically bonded brick, the fine periclase and alumina react to form a spinel (MgO.Al2O3) bond. As the magnesia content of the periclase is increased, the properties of this brick become more outstanding.
Method for Measuring the Dielectric Constant of Ferroelectric Ceramics at S‐Band Frequencies
Authors: SHARPE C. B. , BROCKUS C. G.
Published: June 2006

A method is presented for measuring the complex dielectric constant of ferroelectric ceramics at microwave frequencies. The method employs a disk‐shaped sample in a radial‐line configuration at the end of a coaxial‐line structure. An equivalent circuit, established by admittance measurements, is used to relate the radial admittance at the sample face to the measured admittance on the slotted line preceding the coaxial sample holder. The nonuniform variation of electric field over the face of the sample is taken into account by means of a continued fraction expansion of xJt(x)/J0(x) in terms of x=k′a, where k′ is the wave number in the ferroelectric sample and a is its radius. Representative data on the variation of the complex dielectric constant with temperature at 3 kmc. are given for two samples of BaTiO3 fired under atmospheric pressure and 5000 lb. per sq. in. The frequency spectrum of hot‐pressed Cd2Nb2O7 in the range 1.8 to 4.0 kmc. is also presented.
The Ternary System MgO‐MnO‐SiO2
Authors: GLASSER F. P. , OSBORN E. F.
Published: June 2006

A ternary phase equilibrium diagram is presented for the system Mg0‐Mn0‐Si02. Two peritectic points exist at 1536° and 1538°C. at liquid compositions of (a) 32 MgO, 5 MnO, 63 SiO2 and (b) 36 MgO, 5.5 MnO, 58.5 SO,. Each of these liquids is in equilibrium with a hodonite (Mn‐SiO,) and a high enstatite (MgSiO,) solid solution, the third crystalline phase being cristobalite (SiO2) with (a) and olivine ((Mg,Mn]2,Si04) with (b). Metasilicate solid solutions form a congruently melting rhodonite series in the central part of the MgSi03‐MnSi03 join, but melt incongruently to olivine plus liquid at the MgSiO3 end and to tridymite plus liquid at the MnSi03 end. X‐ray diffraction data are given for two new high enstatite solid solution structures. Rhodonite solid solutions form a continuous structural series extending from MnSi0, to 94.5 weight % MgSi03. Continuous series of solid solutions exist between Mg,Si04 and Mn2SiO4 and between MgO and MnO. Compositional data are given for coexisting condensed phases, and courses of crystallization are described for certain ternary mixtures. A plot is presented of variation of refractive index of glasses which form an almost colorless series in the region of the rhodonite and high enstatite fields. The quenching technique was used in the investigation, with oxygen partial pressure controlled to maintain manganese as Mn2+.
Low‐Temperature Equilibria Among ZrO2, Tho2, and UO2
Authors: MUMPTON F. A. , ROY RUSTUM
Published: June 2006

Studies made on low‐hafnium‐content ZrO2, show that the monoclinic‐tetragonal inversion temperature is 1170°C., and it is raised to approximately 1190°C. in the “natural” ZrO2, which contains approximately 2% HfO2. No explanation could be found for the knownmarked hysteresis during cooling, when the reverse polymorphic transformation takes dace at 1040°C. In the system ZrO2‐ThO2 the monoclinic‐tetragonal ZrO2, inversion temperature is lowered to 1000°C., although the maximum solid solution extent of ZrO2, in Thon and vice versa is approximately only 2% at this temperature. Below about 400°C. under hydrothermal conditions it was possible to prepare a continuous, although metastable series of solid solutions with the fluorite structurewith compositions varying from ThO2, to nearly pure ZrO2. Contrary to earlier work only 8 mole ZrO2, dissolves in UO2 and less than 4 mole of UO, in ZrO2 at temperatures up to 13OO0C. A continuous series of solid solutions could be made between Th2 and UO2 at 13OO°C., and extensive defect fluorite solid solutions could be prepared between Tho2 and U3O8; there is some evidence for exsolution into uranium‐rich and thorium‐rich members at low temperatures.
Fibrillar Colloidal Boehmite; Progressive Conversion to Gamma, Theta, and Alpha Aluminas
Authors: ILER R. K.
Published: June 2006

The conversion of boehmite to transition aluminas and to alpha (corundum) was studied with (a)fibrillar colloidal boehmite, about 50 a.u. in diameter, (b)finely divided boehmite in the form of thin elongated platelets, and (c)macroscopic boehmite crystals. In the range 500o to 700o C., (a)was converted to fibrillar gamma, essentially unchanged in size or shape, (b)was dehydrated to gamma, but the platelets appeared to be partly cracked longitudinally about every 70 a.u., and (c)was similarly cracked into much smaller crystallites of gamma. At about 1000oC., (a)yielded only rodlike theta alumina, whereas (b)and (c)appeared to give a mixture of theta and delta aluminas, characterized by round holes or pores developed from the cracks. In the range 1000o to 1100oC., all the aluminas were converted to alpha, at a rate which was strongly dependent on temperature. The conversion of (a)and (b) to alpha could be followed by subsequent examination with the electron microscope. The alpha crystals, once nucleated, apparently grew rapidly to 0.5 or 1.0 μ in size, since there was no evidence of smaller alpha crystals. The smaller alpha crystals appeared to grow while embedded in a glassy matrix which must have been amorphous alumina. This phase acted as a bridge between the diminishing theta particles and the growing alpha crystals and may have consisted of the alumina which was in the process of being transported.
The System Iron–Titanium–Oxygen at 1200°C. and Oxygen Partial Pressures Between 1 Atm. and 2 × 10−14 Atm.
Authors: WEBSTER A. H. , BRIGHT NORMAN F. H.
Published: June 2006

The 1200°C. isotherm in the system Fe‐Ti‐O has been studied by equilibrating mixtures of iron oxide (Fe2O3) and titanium oxide (TiO2) with atmospheres of controlled oxygen partial pressure. These atmospheresmnsisted of CO2, air, oxygen, mixtures of CO2 and H2, and mixtures of CO2 and CO. The resulting oxide mixtures were examined at room temperature by chemical analysis and by X‐ray diffraction. The stability regions of the α‐oxides (FemTi2‐mO3), of the spinels, (FenTi3‐nO4), and of the orthorhombic oxides (FepTi3‐p O5)were determined. Some nonstoichiometry occurs in the spinels and in the α‐oxides. The oxygen partial pressures at which spinel is reduced to (iron +α‐oxides) and at which α‐oxide (ilmenite) is reduced to (iron + orthorhombic oxide) were determined as 2.1 × 10−13 and 9.3 × 10−14atm., respectively. The orthorhombic solid solution series extends over the whole range of oxygen partial pressures studied.
Water of Hydration in the System Fe–O
Authors: BERG T. G. OWE
Published: June 2006

Fe or Fe + Fe2O3 was heated in a stream of carefully dried oxygen, and the amount of water carried by the gas was determined as a function of time and temperature in the range 300° to 1100°C. Water was evolved as a result of a reaction with the crucible. This water was absorbed by FeO when FeO was present, and was released when the FeO was converted to Fe3O4. The apparent excess of O or deficit of Fe in FeO, reported in the literature, therefore may be due to the presence of water or hydroxide in the FeO. The other oxides, which occur in the phase diagram with exact stoichiometry, absorbed and held much less water, if any.
Dielectric Properties of Solid Solutions of Sodium Niobate‐Lead Zirconate and Sodium Niobate‐Lead Titanate
Authors: BRATSCHUN WILLIAM R. , COOK RALPH L.
Published: June 2006

Solid solutions based on sodium niobate with limited amounts of lead and zirconium or lead and titanium solute ions have been investigated with respect to their dielectric constant versus temperature at 1 kc. per second from −175° to 300°C. Lead zirconate additions to sodium niobate up to 15 mole % cause an increase in dielectric constant, with a value of 1345 at 6°C. being the maximum recorded. Lead titanate additions to sodium niobate cause a general increase in dielectric constant up to 25 mole %, with 675 at 30°C. and 4670 at 154°C. being the maximum values recorded. Polarization versus applied field measurements up to 30,000 volts per cm. show nonreversible polarity for the lead zirconate compositions, whereas the compositions containing from 10 to 50 mole lead titanate are ferroelectric. An induced ferroelectricity phenomenon occurs for the composition containing 5 mole % lead titanate. A remanent polarization of 15 microcoulombs per sq. cm. at a coercive force of 7800 volts per cm. was obtained at room temperature for the composition 0.85 NaNbO3–0.15 PbTiO3.
Effect of Environment and Surface Condition on Strength of Lithium Fluoride Single Crystals
Authors: PHILLIPS W. L.
Published: June 2006

Lithium fluoride single crystals which had been annealed in various gases, abraded with papers of different grits, etched, polished, and coated with metals before testing were deformed in compression. Another series of tests was performed in which the specimens were deformed while immersed in mineral, fatty, dicarboxylic, and tricarboxylic acids and in xanthates, Aero‐floats, amines, water, and bases. Attempts to correlate the observed mechanical properties and the environment or surface condition were partly successful. The appearance of the stress lines and the fracture characteristics of these crystals were also investigated.
Ferroelectric Phase Transitions in the System PbTiO3,‐KNbO3,
Authors: TIEN T.‐Y. , SUBBARAO E. C. , HRIZO J.
Published: June 2006

The formation of a complete series of solid solutions in the system PbTiO3‐KNbO3 was established by X‐ray and dielectric studies. The room‐temperature symmetry of the entire system was tetragonal except for compositions containing more than 96 mole % KNbO3, which had orthorhombic symmetry. The axial ratio, c/a, and the ferroelectric Curie temperature decreased from both the end‐members. The lowest Curie temperature observed in the system was 175°C for the composition with 80 mole % KNbO3. A generalization has been made on the variation of ferroelectric Curie temperatures with compositions in binary systems of perovskitetype solid solutions with and without a common cation.
Viscosity Determination of Boron Oxide and Binary Borates
Authors: LI PEI‐CHING , GHOSE ANIL C. , SU GOUQ‐JEN
Published: June 2006

The anomalous behavior of rubidium and cesium borate glass and the boron coordination in alkali borate liquids are discussed. The viscosity‐composition isotherms of rubidium and cesium borates have been found to follow the same trend as those of other alkali borates. For boron oxide at temperatures between 500° and 775°C, the activation energy for viscous flow, Evis= (4.213 × 104) (1/T) ‐ 22.15 and for temperatures above 775°C, Evis= (1.121 × 104) (1/T) + 7.40, in which T is in °K. The activation energies for viscous flow, Evis, in kcal per mole, increase with all molten alkali borates in the order Li > Na > K > Rb > Cs to about 20 mole % of akali oxide. This phenomenon is explained on the basis of Douglas's hole theory.
Interface Reactions Between Metals and Ceramics: Refractory Metals–Fused SiO2 System
Authors: ARMSTRONG W. M. , CHAKLADER A. C. D. , De CLEENE M. L. A.
Published: June 2006

In a study of the interfacial reactions between SiO2 and the refractory metals Ta, Nb, V, and Mo, a wide range of reactions was observed. Investigation of normal and tapered sections at the interface showed considerable reaction and solution in the case of V, reactions in the cases of Ta and Nb, and very little reaction in the case of Mo. The major interfacial reaction was oxygen corrosion followed by (most possibly) reaction with silica glass to form silicates. X‐ray data showed that the oxides were the principal components at the interface. Evidence was obtained for the formation of silicides in the case of the system Ta‐SiO2. A very low melting silicate was formed in the case of V and silica.
Decarburization of an Iron‐Nickel‐Cobalt Glass Sealing Alloy
Authors: NOTIS M. R.
Published: June 2006

A study was made of the decarburization of an Fe‐Ni‐Co glass sealing alloy in wet hydrogen and its effect on glass‐to‐metal sealing. Rods of this alloy were decarburized in wet hydrogen, and the decarburization process was found to be controlled by a diffusion mechanism where Do= 8.5 × 10‐3 cm2 per second and Q= 25.6 kcal per mole. The decarburized rods were then sealed with glass and the effects of the various decarburization treatments on glass‐to‐metal sealing were observed. These effects are described, and a decarburization schedule for production is suggested.
The System La2O3— TiO5; Phase Equilibria and Electrical Properties
Authors: MacCHESNEY J. B. , SAUER H. A.
Published: June 2006

Phase relations at liquidus temperatures in the system La2O3‐TiO2 were studied in air. The existence of two previously unreported compounds, La2O3. TiO2 and 2La2O3‐TiO2, is postulated on the basis of X‐ray and microscopic examination of crystalline samples, and in the case of La2O3.‐TiO2, on a maximum in the liquidus curve at that composition. Quenched liquids of the primary‐phase field of rutile were found to be semiconducting. This property was related to oxygen loss from both liquid and crystalline phases and is discussed in the light of weight loss experiments, microscopic examination of quenched samples, and information obtained from the literature. Dielectric constant and loss factor of the compounds La2O3‐TiO2, La2O3‐2TiO2, and 2La2O3‐9TiO2 are reported at 1 Mc over the temperature range 25° to 500°C.
Surface Structure in Corundum: II, Dislocation Structure and Fracture of Deformed Single Crystals
Authors: SCHEUPLEIN ROBERT , GIBBS PETER
Published: June 2006

The dislocation structure in plastically deformed single crystals of corundum (α‐A12O3) was studied by etching and optical techniques. A special method of deformation was used which encouraged the participation of both the basal (0001), (1120) and the prismatic (1210), (1010) slip systems concurrently. This deformation resulted in highly stressed crystals which fractured spontaneously once the outside surface was scratched. Incoherent surface like imperfections, accompanied by distinctive dislocation arrays, were found embedded in the deformed crystals. These “surfaces” appeared as discontinuities, on each side of which dislocations etched differently. A possible origin of observed failure making use of the dislocation reaction ± [1010] = 3=1/3[2110] ± 1/3[1120] is suggested. A mechanism for the observed strain hardening in prismatic bending is presented.
Dilatometric and X‐Ray Data for Lead Compounds, II
Authors: ARGYLE J. F. , HUMMEL F. A.
Published: June 2006

Linear thermal‐expansion data are presented for PbAl2O4, Pb2GeO4, PbMoO4, PbWO4, the perovskite‐type structures Pb2MgWO6, Pb2FeTaO6, and Pb3Fe2WO9, and the apatite‐type structures Pb5(SiO4)(VO4)2, Pb5(GeO4)(VO4)2, and Pb5(GeO4)(PO4)2. X‐ray powder data are given, and the behavior of the compounds is correlated with previous information from the literature.
Thermogravimetric Analysis of Five Salts of Praseodymium, Neodymium, and Samarium
Authors: WILFONG ROY L. , DOMINGUES LOUIS P. , FURLONG LeROY R.
Published: June 2006

The thermal decomposition of the ammonium sul‐fate, carbonate, nitrate, oxalate, and sulfate salts of praseodymium, neodymium, and samarium was investigated thermogravimetrically in the temperature range 25° to 1400° C. Each salt was decomposed at a heating rate of 2.5° C per minute. The pyrolytic sequences have been identified, and the temperatures of formation of intermediates and of the sesquioxides have been determined. The sesquioxide formation temperatures increased in the order samarium, neodymium, and praseodymium irrespective of the anion. The nonstoichiometric ranges between Pr6O11 and Pr2O3 and the extent of these ranges have been determined for oxides derived from the carbonate, nitrate, and oxalate salts of praseodymium. The nonstoichiometric oxides of praseodymium were not observed in the decomposition of the alum and sulfate salts.
Studies in the System MgUO3—MgUO4
Authors: HAAG R. M. , MUNCY C. R.
Published: June 2006

Magnesium uranate was prepared by standard solid‐state synthetic techniques. Decomposition pressures were measured between 1000° and 137OOC. At oxygen contents less than MgUO3.5 a solid solution of fluorite structure was found. Above MgUO3.75 the orthorhombic magnesium uranate phase was observed. The two phases were in equilibrium in air at 126OOC. The heat of solution of O2 in the fluorite phase was 45 kcal mole−1 and the heat of the reaction MgUO3.5+ 0.12O2→ MgUO3.75 was 83.3 kcal mole−1 (O2).
Phase Relations in the System Uranium—Carbon—Oxygen
Authors: STOOPS ROBERT F. , HAMME JOHN V.
Published: June 2006

The ternary system U‐C‐O was investigated and a diagram is given expressing the phase relations in specimens which were reacted at 1800°C in vacuum or in inert atmospheres and furnace cooled. A U(C,O) single‐phase area exists in this diagram. The limit of substitutional solid solution of oxygen atoms for carbon atoms in UC is 12.5 at.%, which means that only 25% of the carbon atoms in UC can be replaced by oxygen atoms. The oxygen‐saturated UC phase, U(C0.75O0.25), has a lattice parameter of 4.953 ± 0.001 A. The carbon monoxide partial pressures in equilibrium with this phase were determined for temperatures between 1705° and 1855°C.
Barium Zirconate Modified with Lanthanum, a High‐Temperature Capacitor Dielectric
Authors: KOENIG J. , JAFFE B.
Published: June 2006

The electrical properties of BaZrO3 containing 2 to 6 at. % La were investigated. Room‐temperature dielectric constants at 1 Mc were about 43 and the mean temperature coefficients of K were about −240 ppm per °C. The admixture of La3+ raised the volume resistivity by several orders of magnitude. Values as high as 10° ohm‐cm were observed at 500° C. Q values at 1 Mc and 500° C ranged between 100 and 400. Wafers 10 mils thick endured 1000‐hour life tests at 250° and 350°C in a field of 60 volts per mil and at 500°C in a field of 30 volts per m.il with good stability. Breakdown strengths as high as 680 volts per mil were measured for specimens 10 mils thick. The mechanism of conduction was indicated to be P‐type, with La3+ improving resistivity by lowering the hole concentration.
Growth and Morphology of Magnesium Oxide Whiskers
Authors: WOLFF E. G. , COSKREN T. D.
Published: June 2006

Magnesium oxide crystals and whiskers were grown by vapor phase reactions between MgO and tungsten, hydrogen, and carbon. The large number of morphologies obtained are described in terms of two, three, and fourfold growth symmetry and are related to the growth conditions by current heterogeneous nucleation theory. Threefold (or 〈111〉) growth occurred principally with MgO + H2 reactions, and in all experiments 〈100〉 and 〈110〉 growth occurred under closely similar conditions of temperature and vapor supersaturation. Observations of growth steps suggest that {100} surfaces are favored only at the highest vapor supersaturation. Tensile strength measurements of whiskers with l/d ratios of about 300 show increasing strength with decreasing cross section. A value of 8.13 × 104 psi was observed for a whisker 9.76μ in diameter. The results are of particular interest to the formation of refractory oxides crystallizing in the simple cubic NaCl structure.
Model for Compaction of Ceramic Powders
Authors: SCHWARTZ E. G. , WEINSTEIN A. S.
Published: June 2006

The use of the Coulomb yield criterion to describe the compaction of granular material is proposed. Its use is demonstrated by the numerical solu tion of the stress and displacement equations de scribing the axisymmetric pressing of a cylindrical compact. The model is applied to the pressing of uranium dioxide pellets; to do so, the shear strength of the pellets is measured as a function of normal stress. These measurements showed an increase of shear strength with normal load and permitted assignment of values of cohesion and angle of internal friction to be used in the Coulomb failure condition. The computed re sults of die wall friction, normal force at the die wall, and stress distribution in the compact are compared with measured results.
Microseparation in Lead Borate Glasses
Authors: LIEDBERG D. J. , SMID R. J. , BERGERON C. G.
Published: June 2006

The microstructure of a series of lead borate glasses was studied by electron microscopy and small‐angle X‐ray scattering techniques. Although the glasses were optically homogeneous, microheterogeneities of the order of 2000 to 3000 A were detected in glasses with compositions near the region of two‐liquid stability. The size of these heterogeneities increased as the composition approached the region of immiscibility.
Constitution of Fireclays at High Temperatures: II, Mineralogical Composition
Authors: McGEE THOMAS D.
Published: June 2006

Quantitative X‐ray diffraction analysis of quenched specimens, supplemented by HF solution and X‐ray fluorescence, was used to determine the mineralogical composition of three refractory clays after heating at 1150° to 1500°C. The three clays represent a range of purity found in high and superduty fireclay refractories: an impure plastic clay, a flint fireclay, and a kaolin. The results show the percentages of mullite, cristobalite, quartz, and liquid. The quantity and composition of the liquid phase were estimated by difference. Iron and titanium oxide impurities in the mullite decreased with increased firing temperatures.
Method for Predicting Creep in Tension and Compression from Bending Tests
Authors: FINNIE IAIN
Published: June 2006

It is shown that tensile and compressive creep behavior may be deduced from deflection measurements in creep bending tests on beams of trapezoidal cross section. In the analysis it is assumed that creep strains are proportional to stress and are large relative to elastic strains.
Molybdenum Phosphate Glasses Containing Ag2O or K2O
Authors: PROVANCE J. D. , WOOD D. C.
Published: June 2006

Glasses in the systems MoO3‐P2O5‐Ag2O and MoO3‐P2O5‐K2O were investigated and general areas of composition for good glass formation were determined by X‐ray diffraction methods. Temperature coefficients of electrical resistivity and linear expansion were determined for the glasses along with density, durability, and other thermal characteristics. Resistivity of the glasses was effectively reduced by the addition of Ag2O.
Dielectric Loss in CaF2 Doped with Oxygen Ions
Authors: JOHNSON HOWARD B. , MILLER G. R. , CUTLER IVAN B.
Published: June 2006

Dielectric loss was measured on CaF2 single crystals heated in air at 750° C for 30 hr to introduce O2‐ ions. The loss measurements were made in parallel and in perpendicular directions to the CaF2 surface region which contained most of the O2‐. The layer containing O2‐ was more conducting and therefore produced a space charge relaxation near 10 kcps at 210°C. A similar loss peak was previously reported as due to oxygen ion‐fluorine vacancy dipole relaxation.
Thermoluminescence of Alumina
Authors: KELLY P. J. , LAUBITZ M. J.
Published: June 2006

Results of measurements of thermoluminescence for γ‐irradiated pure, and magnesia‐doped alumina ceramics are presented. A self‐consistent method of glow curve analysis led to results differing from those previously reported in the literature, with smaller trapping energies and realistic attempt‐frequency factors.
Stress Distribution in Multiphase Systems: I, Composites with Planar Interfaces
Authors: OEL H. J. , FRÉCHETTE V. D.
Published: June 2006

Calculated stress distributions within materials sealed together across planar interfaces and having subsequently undergone differential dimensional change were compared with values measured in glass composite pairs sealed together at high temperature and slowly cooled. Where interdiffusion had occurred, dramatic departures from simple theory were observed both in the magnitude and in the sign of the corresponding stresses.
Effect of Micromechanical Stress Cocentrations on Strength of Porous Glass
Authors: BERTOLOTTI RAYMOND L. , FULRATH RICHARD M.
Published: June 2006

The effect of micromechanical stress concentrations around elastic discontinuities in a glass was investigated. Specimens of glass containing porosity of controlled size and volume fraction were fabricated by vacuum hot‐pressing and strength was tested under uniaxial and biaxial stress conditions. Results were interpreted as a function of the relative sizes of Griffith flaws and the volume of material over which stress concentrations act. For the glass investigated, assuming an adequate flaw density, the strength was dependent on pore size and volume fraction as well as on the loading conditions. It is suggested that differences in uniaxial and biaxial strength are due to differences in stress concentration geometry.
Grain Shape Change During Creep in Magnesium Oxide
Authors: HENSLER JOHN H. , CULLEN G. V.
Published: June 2006

Measurements of length‐to‐width ratios of grains in polycrystalline magnesium oxide show no change in grain shape after creep deformation up to 30% compression. This observation is interpreted as implying that all the strain has been produced by grain boundary sliding, with accommodation at triple points being achieved by a process of boundary diffusion.
X‐Ray Topography of Czochralski Ruby
Authors: BELT ROGER F.
Published: June 2006

Single crystals of ruby (Al2O3: 0.05 wt% Cr) were grown by the Czochralski method as 60° type rods. Crystal slices were taken at 30°, 60°, and 90° to the boule axis. Dislocations were observed by Lang X‐ray transmission topographs. All sections revealed a relatively defective central region with a dislocation density of about 104/cm2. Examples were found of polygenization and small‐angle boundaries emanating from the center. Areas near the circumference of the boule had easily resolved dislocation lines and densities as low as 102/cm2. These regions also showed a Frank‐type network with node formation. On all slices distinct parallel groups of dislocation lines were observed. Burgers vector, b, for these dislocations was examined by contrast methods involving alternate orientations of the diffraction vector, g. Burgers vector lay along . A simple model of basal slip of the type (0001) was used to explain these dislocations.
Elastic Behavior of MgO Matrix Composites
Authors: JANOWSKI K. R. , ROSSI R. C.
Published: June 2006

Young's and shear moduli of MgO‐pore and MgO‐nickel‐pore composites were measured at low concentrations of the included phases. The effect of these phases was greater than was predicted from theory. The deviation of the experimental data from theory was explained on the basis of the shape of the included phases. The Young's and shear moduli for fully dense MgO were 3060 and 1305 kbars, respectively.
Kinetics of Opacification of a TiO2‐Opacified Cover Coat Enamel
Authors: EPPLER R. A. , McLERAN W. A.
Published: June 2006

Quantitative X‐ray diffraction measurements were used to study the firing behavior of a typical TiO2‐opacified cover coat enamel. A model was developed for predicting the anatase and rutile concentrations as a function of time and temperature of firing. The model consists of three first order reactions: crystallization of anatase, crystallization of rutile, and inversion of anatase to rutile. It predicts successfully over a wide range of time‐temperature conditions. Discrepancies are found, however, for short‐time, low‐temperature firings. The reflectance data do not correlate well with the crystalline concentration data. The correlation with color data is better, but is not perfect.
Moisture Stress in Unfired Ceramic Clay Bodies
Authors: PACKARD R. Q.
Published: June 2006

The specific energy of water in a clay‐water system, called the moisture stress, is a fundamental parameter governing physical behavior in unfired clay bodies. The importance of moisture stress for studying moisture movement, changes in strength, and other physical properties during drying, is shown. The relations between moisture stress and moisture content for 18 typical New Zealand ceramic bodies have highly characteristic shapes from which the suitability of the material for ceramic use can be deduced. Moisture stress ranges from approximately 0.4 × 106 ergs/g at extrusion, through 2 × 107 ergs/g at the shrinkage limit, to 1010 ergs/g at oven dryness. The dependence of moisture stress on the structural arrangement of clay particles, resulting in a very marked hysteresis, is discussed. The usefulness of the moisture stress concept in understanding practical problems is emphasized.
Initial Sintering of Rutile
Authors: ANDERSON HARLAN U.
Published: June 2006

The initial shrinkage of powder compacts of rutile was measured in air at 700° to 1130°C. The shrinkage behavior agrees well with a model based on grain‐boundary diffusion. The apparent activation energy for the shrinkage rate is 76.9 ± 2.5 kcal/mole. Changes in ambient atmosphere (O2, N2, vacuum) had no effect on the initial sintering kinetics.
High‐Temperature Elasticity and Expansivity of Forsterite and Steatite
Authors: SOGA NAOHIRO , ANDERSON ORSON L.
Published: June 2006

The elastic constants and coefficients of thermal expansion of polycrystalline forsterite (Mg2SiO4) and steatite (MgSiO3) were determined from room temperature to 1000°K. Two elastic moduli, the adiabatic bulk modulus, Bs, and the shear modulus, G, decrease linearly with temperature above 500°K. The Grüneisen constant γ and a parameter δ, defined as — (dBs/dT)/αBs, calculated from the present data were virtually independent of temperature at the high‐temperature range. Poisson's ratio, δ, rises linearly with temperature over the range of measurement; the slope is highest for materials with the lowest room‐temperature value of σ.
Optical and Microstructural Variations with Electric Field in Barium‐Strontium Titanate Ceramics
Authors: SANVORDENKER VIOLA C.
Published: June 2006

Quasi‐thin sections of large‐grained ferroelectric barium‐strontium titanate ceramic compositions were observed under crossed polars. Dielectric constant and light transmission were measured as a function of temperature and applied dc voltages. Microscopic observations, such as changes in structure and in optical anisotropy with temperature and simultaneously applied electric fields, are described. Optical data indicate that static electric fields readily induce anisotropy in the isotropic grains at the ferroelectric to paraelectric transition of the ceramic. Below the transition temperature, the effect of the field on the optical and dielectric properties diminishes. Contrary to single‐crystal barium titanate, a field‐produced reorientation of domains in the ceramic at temperatures below the transition proceeds with difficulty, and is sometimes achieved only after long exposures to high‐biasing fields.
Vaporization of Lead Zirconate‐Lead Titanate Materials
Authors: NORTHROP DAVID A.
Published: June 2006

A thermogravimetric investigation of the vaporization of cold‐pressed Pb(Zr0.65Ti0.35)O3 in vacuum from 690° to 1130°C shows that the vaporization occurs in two steps. An initial loss of 1 to 7 wt% proceeds by a mechanism with a logarithmic time dependence and represents the vaporization of the unreacted PbO that remains after the initial calcining. The second step proceeds by a slower, diffusion‐controlled mechanism with a parabolic time dependence. It is shown that this rate‐determining step is bulk diffusion across a thickening lead‐depleted layer in the cold‐pressed pellet, despite pore volumes of 24 to 42%. The rate constant, g/cm2 sec½, for the parabolic weight loss process is expressed by: log K= (3.37 ± 0.14) ‐ (8.46 ± 0.16) (103/TK). The activation energy is 38.7 ± 2.0 kcal/mole.
Thermal Simulation of In‐Reactor Microstructures in ThO2‐UO2
Authors: KERR JOHN M.
Published: June 2006

A device was built to provide the capability for out‐reactor simulation of the microstructures seen in irradiated fuel. Out‐reactor simulation of nuclear heating makes possible the precise measurement of temperature gradients in the fuel and provides data for correlating microstructural alterations with temperature. The simulation apparatus was designed to produce controlled thermal gradients sufficient to produce both equiaxed and columnar grain growth in the specimens. Provision was made for calorimetric measurements from which thermal conductance could be determined. Micro‐structural alterations in UO2 and ThO2‐UO2 materials were achieved, and thermal conductivity data were recorded. Microstructural alterations in the ThO2‐10 wt% UO2 specimens were similar to those that other investigators have observed in UO2 at lower temperatures.
Approximate Theory of Thermal Stress Resistance of Brittle Ceramics Involving Creep
Authors: HASSELMAN D. P. H.
Published: June 2006

The effect of stress relaxation by creep on the thermal stress fracture of brittle ceramics at high temperature under conditions of quasi‐static heat flow is discussed. It is shown that, to a good approximation, thermal stress relaxation rates can be calculated on the basis of creep rates which correspond to the minimum temperature of the ceramic workpiece. For materials exhibiting linear stress‐creep rate dependence, expressions for the relaxation time and maximum temperature difference or heat flux to which ceramic bodies can be subjected are derived in terms of the material variables affecting thermal stress fracture and stress relaxation by creep. A numerical example shows that high‐temperature creep can materially affect the thermal stress behavior of brittle ceramics. Appropriate thermal stress parameters are proposed to form the basis of proper material selection for high‐temperature environments involving thermal stress and stress relaxation by creep. Conditions for which thermal stress calculations should be based on an elastic or viscoelastic analysis are outlined.
Mechanism of Creep in MgO Brick
Authors: KREGLO J. R. , SMOTHERS W. J.
Published: June 2006

Creep of selected brands of periclase refractories was studied using rate process theory to provide information on activation energy and on the dominant method of deformation. A brand studied over the range 2200° to 2600°F at 25 psi gave an activation energy of 62 kcal/mole. All brands were studied at selected stresses and 2500°F to determine the flow mechanism. Plastic flow was indicated for all brands tested.
Heats of Solution, Density, and Refractive Index Changes in Sodium Borate Glasses Subjected to High Pressure
Authors: STEWART DANIEL R. , RINDONE GUY E. , DACHILLE FRANK
Published: June 2006

The densification produced in sodium borate glasses by pressures to 40 kbars at 25° and 250°C was measured. At a constant temperature and pressure, the densification decreased with increasing alkali content. For specimens pressed at 40 kbars and 250°C, the densification ranged from 14.2% for B2O3 to 6.3% for the 33.3 mole % Na2O composition. Under the same conditions, the refractive index increase ranged from 4.8 to 1.1%, and the decrease of the molar refraction of the oxygen ions ranged from 2.5 to 1.5%. The heats of solution of the pressed glasses were more negative than those of the corresponding unpressed glasses. The heats of solution of both the pressed and unpressed glasses pass through a minimum near 20 mole % Na2O. A decrease in density was observed at room temperature for all pressed specimens. Electron micrographs were made of two of the pressed specimens. The results could be explained on the basis of a repacking of structural units.
Direct Observation of Nonbasal Dislocations in Sintered Alumina
Authors: GULDEN T. D.
Published: June 2006

The Burgers vectors of several nonbasal dislocations in sintered α‐Al2O3 were determined from diffraction contrast experiments in the electron microscope. They are consistently of the type ⅓. This is also likely to be the Burgers vector for prismatic slip in α‐Al2O3. It has been generally accepted that is the Burgers vector for prismatic slip, but the evidence for this is not conclusive.
Kinetics and Mechanism of the Reaction Between Zinc Oxide and Barium Carbonate
Authors: HULBERT SAMUEL F. , KLAWITTER JEROME J.
Published: June 2006

The kinetics of reaction between BaCO3 and ZnO were studied using thermogravimetric analysis to monitor the percent reaction versus time. Solid state reaction models based on (a) product growth controlled by diffusion through a continuous product layer, (b) product growth controlled by phase boundary reactions, and (c) the concept of an order of reaction, were invalid for the reaction studied. The kinetics of the reaction were described by the kt=–ln (1 –x)⅔ nuclei growth equation. The defect nature of the zinc oxide studied was altered by doping with Li2O and Cr2O3. The activation energy for the reaction of BaCO3 and pure ZnO was 54.6 kcal/mole. The changes in activation energy with the type and amount of ZnO doping cannot be accounted for by the quasi‐chemical theory of solids.
The Quaternary System U‐C‐0‐N at 1700 C
Authors: HENRY JACK L. , BLICKENSDERFER ROBERT
Published: June 2006

The quaternary system U‐C‐O‐N was examined at 1700°C by microstructural and X‐ray analyses of sintered powder compacts. Subliquidus phase relations, oxycarbonitride solid solution lattice parameters, and equilibrium pressures of N2 and CO were studied. Although the emphasis was on the solid‐solution field in the uranium monocarbide‐mononitride‐monoxide region, phase fields in the uranium‐rich region and the carbon‐nitrogen‐oxygen‐rich region were examined. Nineteen fields were established experimentally, and their boundaries were located. Two other fields are postulated on the basis of phase rule and topological requirements. An isothermal phase diagram of the system is proposed.
Characterization of Porosity in Porcelain‐Bonded Porous Alumina Ceramics
Authors: ROY SALIL K.
Published: June 2006

A water removal method was used to determine pore sizes in highly porous large‐pore‐size specimens. The maximum, minimum, and equivalent pore sizes, as well as complete size distributions (number of pores vs pore sizes), were obtained. The results agree with those obtained using a mercury porosimeter. Characterizing parameters such as permeable porosity, labyrinth factor, and structure factor were estimated from the water removal porosimeter data. Electrolytic resistance was measured to determine the tortuosity and inert porosity. A physical meaning of Archie's law which correlates the formation resistivity factor with porosity is also given. Sonic Young's and shear moduli depended on both the porosity and particle sizes. The Young's modulus was linearly related to the modulus of rupture.
Interaction of Radiation and Conduction in Glass
Authors: CHUI GRANGER K. , GARDON ROBERT
Published: June 2006

The interaction of radiation and conduction was rigorously treated for one‐dimensional heat transfer, both transient and steady‐state. In this paper only some steady‐state results are discussed. They show that the interaction of radiation and conduction affects temperature distributions and heat fluxes in a variety of ways, depending on physical properties and boundary conditions. The illustrations include a computer simulation of experiments to measure the thermal conductivity of glass and an attempt to predict the vertical temperature profile in a glassmelting tank.