bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical and Electrical Properties of a Nickel Ferrite as Affected by Compositional Changes
Authors: MUM S. L. , ZNEIMER J. E.
Published: June 2006

A series of ferrites was prepared in the form Ni1‐αCoαFe2O4, where α varied from 0.00 to 0.05. It has been shown experimentally that the width of the curve of magnetic loss versus magnetic field can be minimized by the proper value of α. The large crystal anisotropy of cobalt enables one to choose the composition where the resultant crystal anisotropy constant should equal zero. Techniques are discussed which could increase the resistivity of these ferrites.
Pressure Effects in the Transformation Range of Glass
Authors: MAURER R. D.
Published: June 2006

Survey experiments have been made to find the effect of pressure on relaxation rates and volume in the transformation range of glass. An empirical equation used to describe relaxation effects for volume changes at atmospheric pressure has been extended to describe the influence of pressure. Data for glass cooled at a constant rate through the transformation range under pressure are adequately described by this empirical equation. The effect of pressure on the volume of liquid glass has been measured indirectly using a sample rapidly cooled under pressure, providing an approximate value for the compressibility of liquid glass.
Backup Materials as a Source of Efflorescence
Authors: YOUNG JAMES E.
Published: June 2006

Because white stains on the face of brick masonry walls are often the same salts that are associated with Portland cement, an investigation was made to determine whether efflorescing salts can originate in concrete backup block. The soluble‐salts content was determined for selected clap brick, concrete block, and clay tile; wick tests were run on the material. Composite walls were built of nonefflorescing brick backed with clay tile or with concrete block; high humidity was maintained on the back side of the walls and the moisture was allowed to migrate to the dry brick face. The discoloration of the face brick was compared and the salts were identified.
Fundamentals of Glass‐to‐Metal Bonding: III, Temperature and Pressure Dependence of Wettability of Metals by Glass
Authors: FULRATH RICHARD M. , MITOFF STEPHAN P. , PASK JOSEPH A.
Published: June 2006

The effects of temperature and pressure on the wettability of metals by glass were studied. A system was completed that was capable of subjecting test combinations to temperatures up to 1400°C. at a working pressure of 10−5mm. of Hg. The variation in wetting with change in pressure and temperature was analyzed by the use of Young's equation primarily for the systems gold–, platinum–, and iron‐sodium silicate glass. The interfacial energy for the system gold‐sodium silicate glass was calculated to be 1230 dynes per cm. The limitations imposed on the use of Young's equation for analyzing wettability in systems in which an interfacial compound is formed are discussed.
Properties of Yttrium Oxide Ceramics
Authors: CURTIS C. E.
Published: June 2006

The cubic structure of yttrium oxide is stable to 1800°C. in air as indicated by petrographic, X‐ray, and differential thermal analyses. A change in lattice parameter of less than ±0.007 a.u. was observed on heating the oxide to 1800°C. The mean specific heat of Y2O3 to 1600°C. was 0.13 cal. per gm. per °C. The coefficient of linear expansion to 1400°C. was 9.3 × 10−6 in. per in. per °C. Compacts of Y2O3 required a temperature of 1800°C. for vitrification. In equimolecular binary mixtures heated in the powdered state at 1500°C., Y2O3 formed compounds with Al2O3 and Fe2O3 and solid solutions with ZrO2 and HfO2. Y2O3 did not react with CaO, MgO, or ThO2. Crystal types and unit‐cell sizes of the reaction products are included.
Directional Dilatation of Crystal Lattices at Elevated Temperatures
Authors: BEALS R. J. , COOK R. L.
Published: June 2006

The X‐ray measurement of lattice parameters of crystals at elevated temperatures provides a means of determining the true thermal expansion of a crystal. In this investigation, a furnace in which temperatures above 1200°C. could be accurately maintained and a specially designed circular back‐reflection X‐ray camera were employed in measuring the thermal dilatation of crystals representative of the cubic, hexagonal, rhombohedral, and tetragonal systems. Thermal‐expansion values up to 1200°C. are reported for magnesia, alumina, zinc oxide, rutile, beryllia, calcium oxide, and strontium oxide and for magnesia‐alumina, magnesia‐chrome, zinc‐alumina, and zinc‐chrome spinels.
Constitution of Sodium, Potassium, and Lithium Phosphate Glasses
Authors: WESTMAN A. E. R. , GARTAGANlS P. A.
Published: June 2006

The chain‐length distributions in solutions of sodium phosphate glasses were reinvestigated using improved paper chromatographic techniques. The range of compositions was extended to glasses of higher Na/P ratios by using a through‐flame technique for their preparation. The distributions obtained confirmed the earlier work with the exception that cyclic phosphates were found in solutions of glasses having or approaching the metaphosphate composition despite prolonged heating of the glasses in the molten condition. The earlier observation was that prolonged heating eliminated the cyclic phosphates. As before, no orthophosphate was found, as predicted by Van Wazer, and neither the Poisson nor the “random reorganization” distributions fitted the data for both high‐ and low‐average chain lengths. Although some sort of rearrangement is occurring in the melt, it may not be a completely random process; a rapid change of chemical properties with chain length of the short polymers may have to be taken into account. This was confirmed by similar studies of potassium and lithium phosphate glasses, whose distributions were found to be different enough to demonstrate a cation effect. Consequently, more than stoichiometry is involved.
Thermal Conductivity: XIII, Effect of Microstructure on Conductivity of Single‐Phase Ceramics
Authors: CHARVAT F. R. , KINGERY W. D.
Published: June 2006

The thermal conductivity of Al2O3, MgO, TiO2, and CaF2 single crystals and single‐phase poly‐crystalline aggregates of controlled microstructure was measured between 0° and 1000°C. The conductivity of pure single‐phase dense polycrystalline aggregates agrees with that of the corresponding single crystals at temperatures below the onset of radiant‐heat transfer. Small amounts of impurities and the pore geometry may considerably affect the conductivity of aggregates.
Cermets: II, Wettability and Microstructure Studies in Liquid‐Phase Sintering
Authors: PARIKH N. M. , HUMENIK M.
Published: June 2006

The microstructures of polyphase, heterogeneous systems, sintered in the presence of a liquid phase, are analyzed on the basis of wettability and surface‐energy relations. General principles relating to the primary factors affecting the microstructure are discussed. The application of these principles to such diverse systems as metal‐carbide, metal‐glass, and metal‐metal show that the microstructure and distribution of the solid in the liquid is primarily determined by various surface‐energy relationships. A general “coalescence hypothesis” based on this work is proposed.
Kinetics of Cristobalite Formation from Silicic Acid
Authors: VERDUCH A. G.
Published: June 2006

Rate experiments made on the transformation of silicic acid into cristobalite, in the temperature range 945° to 1085° C, have demonstrated the existence of a measurable nucleation period. From its variation with temperature, a value of 102.8 kcal. per mole has been calculated for the activation energy of the nucleation process. A second step of the transformation, involving the growth and perfecting of the new phase, has been shown to occur with an activation energy of 50.9 kcal. per mole. From the shape of the rate curves it has been calculated that a superstructure having fairly well‐defined sequence rhythms of alternating three‐ and two‐layer structural units might be the end product of heating silicic acid in the temperature range covered by the present experiments. It also has been demonstrated that the degree of disorder increases from the core to the surface of the transforming cristobalite crystals.
Temperature Dependence of Strength and Brittleness of Some Quartz Structures
Authors: WESTBROOK J. H.
Published: June 2006

The temperature dependence of the microhardness of the quartz structures of both SiO2 and the isomorphous compounds AlPO4, GeO2, and LiAlSiO4 has been examined. Particular attention has been given to the effects of the high‐low inversion, which has been found to be anomalous relative to the behavior of other polymorphic transformations. The high quartz structure has been found to be much harder and more brittle than low quartz, despite their very close structural similarity.
Phase Equilibria in the Alkali Fluoride‐Uranium Tetrafluoride Fused Salt Systems: II, The Systems KF‐UF4 and RbF‐UF4
Authors: THOMA R. E. , INSLEY HERBERT , LANDAU B. S. , FRIEDMAN H. A. , GRIMES W. R.
Published: June 2006

Mixtures of alkali fluorides with uranium tetra‐fluoride are of potential importance in molten‐salt reactors and in the reprocessing of nuclear fuels. In this paper detailed phase diagrams are presented for the binary systems KF‐UF4 and RbF‐UF4. Data for the determination of phase boundaries were obtained in large part by quenching after equilibration. Thermal analysis and visual observation were used as supplementary methods. Phase identifications were made by X‐ray powder diffraction and by optical microscopy. In the system KF‐UF4 four compounds have been identified. Two of these, 3KF.UF4 and 7KF.6UF4, melt congruently at 957°C. and at 789°C., respectively. The compound 2KF UF4 melts incongruently to 3KF.UF4 and liquid at 755° C., and the compound KF.2UF4 melts incongruently to UF4 and liquid at 765° C. There are three eutectic points in the system: 15.0 mole % UF4, 735° C.; 38.5 mole % UF4, 740° C.; and 54.5 mole % UF4, 735° C. The compound 2KF.UF4 decomposes during cooling to 3KF.UF4 and 7KF 6UF4 at 608° C. Two other compounds, KF 3UF4 and KF.6UF4, have been described by another investigator. One of these, KF 3UF4, was not obtained at all in the present investigation. The other, KF.6UF4, was not obtained under equilibrium conditions and was found only in KF‐UF4 mixtures that had been exposed to the atmosphere while molten. Seven solid compounds are present in the system RbF‐UF4. All of these melt incongruently with the exception of 3RbF.UF4 and RbF‐UF4, which melt at 995° C. and at 735° C., respectively. The incongruently melting compounds and their melting points, peritectic compositions, and melting products are: 2RbF UF4, 818°C., 38 mole % UF4, 3RbF ‐UF4+ liquid; 7RbF.6UF4, 693° C., 44 mole % UF4, RbF.UF4+ liquid; 2RbF.3UF4, 722° C., 56.5 mole % UF4, RbF.3UF4+ liquid; RbF. ‐3UF4, 73O°C., 57 mole % UF4, RbF.6UF4+ liquid; and RbF.6UF4, 832°C., 70.5 mole % UF4, UF4+ liquid. The three eutectic temperatures and compositions in the system are: 10.0 mole % UF4, 710°C.; 43.5 mole % UF4, 675°C.; and 55.0 mole % UF4, 714°C.
Efflorescence Resulting from Sulfates in Clay Raw Materials
Authors: BROWNELL WAYNE E.
Published: June 2006

An attempt has been made to isolate the effects of sulfates in clay raw materials on efflorescence from the effects of sulfides and sulfurous fuels. A low‐sulfur shale was used and sulfates were added in different amounts and particle sizes. It was found that sulfates react with clays between 1800° and 1900°F. with the result that efflorescence is reduced. Sulfates were not considered as a serious source of soluble salts causing efflorescence. Recommendations are given for minimizing efflorescence when sulfates occur in the raw material.
Studies in Lithium Oxide Systems: I, Li2O B2O3–B2O3
Authors: SASTRY B. S. R. , HUMMEL F. A.
Published: June 2006

Phase relationships in the system Li2O, B2O3‐B2O3 were studied by the quenching method using twenty compositions. The crystalline phases encountered were (a) Li2O, B2O3, which melts congruently at 849°± 2°C., (b) Li2O.‐2B2O3, which melts congruently at 917°± 2°C., (c) a new compound, 2Li2O‐5B2O3, which melts incongruently at 856°± 2°C. and dissociates below 696°± 4°C., (d) Li2O.3B2O3, which melts incongruently at 834°± 4°C. and dissociates below 595°± 20°C., and (e) probably Li2O.4B2O3, which melts incongruently at 635°± 10°C. Reactions were sluggish at temperatures near 600°C., resulting in metastable relations. Hence phase equilibrium data relating to the lower stability limit of Li2O.3B2O3 and to the upper stability limit of Li2O.4B2O3 are considered to be tentative. Properties of the glasses and crystalline phases were studied. The refractive index of the glasses increased with the addition of Li2O up to 22%, but further additions up to 40% had no substantial effect. Glasses containing less than 30% Li2O were water soluble. Limited data on the density and thermal expansion of the glasses are presented. Li2OB2O3 was euhedral, lath‐shaped, length‐fast, biaxial negative (2V = 27°), with nα= 1.540, nβ= 1.612, nγ= 1.616. Li2O.2B2O3 was uniaxial negative, with ne= 1.560, nw= 1.605. Li2O.3B2O3 was biaxial negative (2V = 75° to 80°), with nα= 1.576, nβ= 1.602, nγ= 1.605. X‐ray powder diffraction data for the five crystalline compounds are presented. Thermal expansion data for Li2O‐B2O3 and Li2O.2B2O3 and limited data on the fluorescent properties of the compounds are given. X‐ray diffraction data are also presented for Li2O.B2O3.4H2O and Li2O.‐5B2O3. 10H2O. Li2O B2O3 was obtained by heating the first hydrate at 450° to 680° C. X‐ray diffraction showed Li2O.4B2O3 and Li2O‐3B2O3 to be the crystalline products obtained during heating the decahydrate at 500°C. and 600°C., respectively.
Effect of Atmosphere on Surface Tension of Glass
Authors: PARIKH N. M.
Published: June 2006

The surface tension of a commercial soda‐lime‐silica glass was measured in various atmospheres in the temperature range 500° to 700° C. The method of fiber elongation was used and its usefulness is illustrated. Water vapor was found to exhibit the most pronounced effect, causing a lowering from 315 to 205 dynes cm.−1 for a vapor pressure of 16 mm. Hg.
Use of Nepheline Syenite Tailings in Sewer‐Pipe Bodies
Authors: WILSON ROBERT C. , KOENIG C. J.
Published: June 2006

Small additions of ground nepheline syenite tailings were incorporated into various sewer‐pipe bodies. The lost‐cost tailings contained 2 to 3% Fe2O3 and significantly improved the physical properties of the sewer‐pipe bodies.
The Ternary Systems BaO–TiO2–SnO2 and BaO‐TiO2‐ZrO2
Authors: JONKER G. H. , KWESTROO W.
Published: June 2006

An investigation of the ternary systems BaO‐TiO2‐SnO2 and BaO‐TiO2‐ZrO2 led to the discovery of two new compounds belonging to the system BaO‐TiO2. These compounds, Ba2Ti9‐O20 and Ba2Ti9O20, are stabilized by minute additions of SnO2 or ZrO2. The known compound BaTi2O5 can be obtained only from the molten phase and decomposes below 1300°C. into Ba2Ti5O12 and BaTiO2. In these systems no ternary compounds are found. The ternary phase diagrams can be divided into regions with high and low dielectric losses, which are in accordance with the phase relations. Tables with crystallographic data of the new compounds are included.
Electron Microscope and Electron Diffraction Studies of Sintering of Magnesite
Authors: PANDE A. , SINGH RABINDAR
Published: June 2006

Electron micrographs and electron diffraction patterns of chemically pure and natural magnesite samples heated from 400° to 1050°C. were obtained and interpreted. It was found in general that at lower temperatures (400° to 600°C.), small MgO particles were formed by the decomposition of MgCO3 (MgO + CO2). As temperatures were increased (600° to 800°C.), these particles grew into large secondary aggregates showing higher porosity. The porosity of the main particles (unchanged MgCO3) also increased. Sintering began at 850° C., and the particles seemed to adhere more strongly to each other and aggregation and porosity decreased. Sintering was completed at 1050°C., and sharply defined cubic crystals were observed in large numbers varying in size from 0.1 to 0.35 μ. In natural magnesites that contained traces of iron and aluminum oxides the decomposition began at higher temperatures than in the chemically pure samples, but the recrystallization process was delayed, which is contrary to expectations.
Study of Surface Structure of Glass as Related to Its Durability
Authors: SIMPSON H. E.
Published: June 2006

The durability of various glasses was studied by first submitting test samples to a controlled cyclic humidity test and evaluating the degree of surface breakdown by means of a haze meter. Electron microscope replicas were made of many samples and the pictures revealed the degree of attack and appearance of the eroded glass surfaces. This study carried out at high magnification indicated that the various glasses showed surface failures dependent on their composition and previous surface treatment. The technique is believed to offer considerable promise for the study of the durability of glass surfaces.
Phase Equilibria in the Alkali Fluoride‐Uranium Tetrafluoride Fused Salt Systems: I, The Systems LiF‐UF4 and NaF‐UF4
Authors: BARTON C. J. , FRIEDMAN H. A. , GRIMES W. R. , INSLEY H. , MOORE R. E. , THOMA R. E.
Published: June 2006

Detailed phase diagrams, and a description of the techniques which were employed, are presented for the systems LiF‐UF4 and NaF‐UF4. The phase diagrams are complete with respect to the stable phase boundaries from the liquidus to 300°C. and are accurate to within 5°C. with respect to temperatures. The data were obtained from thermal analysis, equilibration followed by quenching, differential thermal analysis, and visual observation methods closely coupled with examination by X‐ray diffraction techniques and optical identification of the cooled melts from all these procedures. The system LiF‐UF4 contains only incongruently melting compounds with the following peritectic liquid compositions and temperatures: 4LiF. UF4, 26 mole % UF4, 500° C.; 7LiF.6UF4, 40 mole % UF4, 610°C.; and LiF‐4UF4, 57 mole % UF4, 775° C. A single eutectic occurs at 27 mole % UF4 and 490°C. The compound 4LiF.UF4 has a lower limit of stability at 470° C., whereas 3LiF.UF4 is metastable. Five compounds occur in the system NaF‐UF4 Congruent melting points were found for 3NaF.UF4 at 629°C. and 7NaF.6UF4 at 718°C. Peritectic liquids occur at 32.5 mole % UF4 and 648° C. for 2NaF UF4 and at 37 mole % UF4 and 673° C. for 5NaF.3UF4. NaF‐2UF4 has a subsolidus upper limit of stability at 660° C. Eutectic liquids appear at 21.5 mole % UF4 and 618°C., 28 mole % UF4 and 623°C., and 56 mole % UF4 and 680°C. The compound 3NaF.UF4 has a transition at 528°C. and is unstable below 497°C.; the compound 5NaF‐3UF4 is not stable below 63O° C. The only stable modification of 2NaF.UF4 above 273°C. is a hexagonal form not previously reported. The “α‐2NaF.UF4” phase reported by Zachariasen apparently is 5NaF.3UF4, and the γ‐2NaF. UF4 which he described is metastable.
Reactions in Silica‐Alumina Mixtures
Authors: WEST RICHARD R. , GRAY THOMAS J.
Published: June 2006

Examination of mixtures of extremely pure silica and alumina shows that the greatest reactivity is not encountered with stoichiometric ratios to form mullite with the formula 3Al2O3. 2SiO2 but rather with the formula 2A12O3‐SiO2, and that reactivity also depends on the crystalline modification of alumina. A sharp exothermic differential thermal peak at 980°C. is attributed to three simultaneous reactions dependent on the silica‐alumina ratio of the mixture: (1) the crystallization of gamma alumina, (2) the crystallization of a hydrogen aluminum spinel (HAl5O5), and (3) the reaction of silica with the hydrogen aluminum spinel to form mullite.
Effect of Surface Conditions on Room‐Temperature Ductility of Ionic Crystals
Authors: GORUM A. E. , PARKER E. R. , PASK J. A.
Published: June 2006

With the progress on dislocation theories and a better understanding of flow phenomena, it was predicted that a class of materials normally considered to be brittle, namely, ionic solids having cubic crystal structures, would possess a degree of ductility. Experimental results on a number of ionic materials indicate that face‐centered cubic and body‐centered cubic ionic materials can exhibit a considerable amount of ductility under controlled conditions. It was found that these materials are inherently ductile rather than brittle and that there appear to be two factors, a surface reaction with components of the air and impurity concentration, that exert control over the ductility. The examination of the air embrittlement indicated that oxygen and nitrogen are the cause of decreased ductility in water‐soluble salts such as KC1 and KBr. The effect on the surface can be inhibited by surface treatment or by immersion in oil. Other materials such as MgO and LiF do not seem to exhibit a surface embrittlement. MgO does, however, show a time‐dependent ductility that is attributed to the presence of impurities.
Measurement of Stress‐Optical Coefficient and Rate of Stress Release in Commercial Soda‐Lime Glasses
Authors: VAN ZEE ARTHUR F. , NORITAKE HENRY M.
Published: June 2006

A method is described for measuring the stress‐birefringence properties of soda‐lime glasses in the range 23° to 650°C. Data on three glasses show that the stress‐optical coefficient increases slowly with temperature, reaching a definite maximum in the range 570° to 590°C. The same apparatus was used to measure the rate of stress release in two of these glasses. Data obtained under thermal equilibrium conditions can be represented by equations that suggest that two or more concurrent mechanisms are involved in stress release in these glasses within the viscosity range log 12 to log 14.5 (a rapid one of 0.4 to 10 minutes in duration and a slow one of 2 to 60 minutes).
Shape of Liquid Immiscibility Volume in the System Barium Oxide‐Boric Oxide‐Silica
Authors: LEVIN ERNEST M. , CLEEK GIVEN W.
Published: June 2006

The shape of the immiscibility volume in the system BaO‐B2O3‐SiO2 is determined from data on seventeen compositions. The ternary critical solution curve originates at the critical point in the binary system BaO‐B2O3, located at 1225°C. and 15 weight % BaO. It extends almost linearly to its terminus on the silica primary‐phase surface, at about 1405° C. and the composition 18 weight % BaO, 10.5% B2O3, 71.5% SiO2. By extrapolation of the ternary critical solution curve, the critical point of the postulated meta‐stable immiscibility region in the binary system BaO‐SiO2 is located at 1430° C. and 18.5 weight % BaO.
Steam Sintering of Uranium Dioxide
Authors: ARENBERG C. ARNE , JAHN PAUL
Published: June 2006

The following variables were considered in an investigation of the sintering of uranium dioxide: (1) sintering aids, i.e., small additions of substances that might aid the densification process, (2) soaking temperature, (3) soaking time, (4) furnace atmosphere, and (5) particle size of the uranium dioxide. The incipient sintering temperature, the effect of binders, and the effect of fabricating pressure also were determined. The data obtained in the investigation led to the following optimum conditions for obtaining dense UO2 by cold pressing and sintering: (1) preparing the UO2 as a submicron powder but not fine enough to be pyrophoric, (2) cold pressing at 20 to 30 tons per sq. in. without the use of organic binders, (3) using the following sintering schedule: (a) in H2 to 1400°C., (b) in steam or a wet inert gas from 1400° to 1500°C., (c) in steam or a wet inert gas at 1500°C. for a 1‐hour soak, and (d) cooling in H2 from 1500°C. to room temperature. By following this procedure, pellets of UO2 (3/8 in. in diameter by 1/4 in. high) were obtained that were 97 to 98% of theoretical density.
High‐Temperature Mechanical Properties of Ceramic Materials: I, Magnesium Dititanate
Authors: BUSH E. A. , HUMMEL F. A.
Published: June 2006

The thermal expansion, modulus of rupture, and modulus of elasticity of sintered magnesium dititanate were measured as functions of temperature and thermal history. The values increased with increasing temperature up to 1000°C., and hysteresis effects were found during cooling. Delayed strain effects were observed. These phenomena were attributed to the occurrence and recombination of internal fractures that result from stresses arising from the high anisotropy of thermal expansion of magnesium dititanate.
Calculation of Temperature Distributions in Glass Plates Undergoing Heat‐Treatment
Authors: GARDON ROBERT
Published: June 2006

A method is presented for calculating temperature distributions in diathermanous sheets that are being heated or cooled. It differs from previous calculations of this type in that it takes a more comprehensive account of radiative effects that play a part in these processes. Principally, these effects are the penetration of external radiation into the sheet, the emission and partial re‐absorption of radiation within the sheet, and multiple internal reflection between the surfaces of the sheet. A high‐speed digital computer has been programmed to perform these calculations. The results of a few representative examples are presented to illustrate the influence of diathermancy on the thermal history of glass plates undergoing various heat‐treatments.
Glass Formation and Properties of Glasses in the System Na2O‐B2O3‐SiO2‐TiO2
Authors: STRIMPLE J. H. , GIESS E. A.
Published: June 2006

An investigation was made of the effect of TiO2 on the glassforming region and on the physical properties of glasses in the system Na2O‐B2O3‐SiO2TiO2. Glasses containing up to 45 mole % TiO2 may be formed with an alkali content of 30 mole %. At lower alkali contents (10 mole % Na2O) glasses may be formed containing up to 22 mole % TiO2. The way in which the coefficient of linear thermal expansion and the transformation and softening temperatures are affected by TiO2 additions has been determined.
Design of Extrusion Augers and the Characteristic Equation of Ceramic Extrusion Machines
Authors: PARKS J. R. , HILL M. J.
Published: June 2006

Since the invention of the auger‐type extrusion machine, there has developed a large business devoted to the production of extrusion machines of various types and sizes for the ceramic industry. During this time, a vast body of empirical knowledge concerning the design of augers, dies, and machines to do particular jobs has grown. As of today, no method has been proposed by which values may be assigned to the design parameters of an auger so that there may be reasonable assurance that it will extrude a material, the plastic properties of which may be known. This paper proposes a model for the operation of an auger on a material and adapts the theory of the screw conveying of solids in organic thermoplastic extrusion machines to the study of this model. The concept of the characteristic function, which describes the action of a particular extruder on a plastic material, is discussed.
Thermodynamics of Arsenic in Glass
Authors: BAAK TRYGGVE
Published: June 2006

Vapor pressures of arsenic trioxide over glass have been determined. From these results, together with analytical data of trivalent and pentavalent arsenic in the glass and the oxygen pressure, the free energies of solution of arsenic trioxide and arsenic pentoxide have been calculated. In a similar way the free energy of formation of Na4As2O7 from the oxides has been determined for comparison.
Oxide Adherence and Nickel Flashing in Vitreous Enameling
Authors: CRYSTAL H. , BULLOCK G.
Published: June 2006

The influence of iron deposition and nickel flashing on the adherence of oxides to enameling‐grade sheet steel has been examined. Nickel flashing promotes oxide adherence, and a correlation between oxide adherence and adherence of a directly applied titania self‐opacified cover‐coat enamel has been established. Further work is necessary, however, to obtain a satisfactory enamel surface texture under these conditions before the direct application of a cover‐coat enamel can become a commercial possibility. Similarly, good adherence of a titania self‐opacified cover coat applied directly to steel has been promoted by nitric acid pickling with and without a nickel‐flashing treatment. Finally, the iron content of a hydrochloric acid pickling bath and the amount of hydrogen absorbed by the steel during pickling have been shown to influence the amount of nickel deposited on the steel during flashing.
Aging and the Double Hysteresis Loop of PbλCa1‐λTiO3 Ceramics
Authors: SAWAGUCHI E. , CHARTERS M. L.
Published: June 2006

Double hysteresis loops were observed in a solid solution, Pb0.5Ca0.5TiO3, which was held at room temperature for several hours after cooling from a high temperature (200°C.). To discover the mechanism of the processes causing the peculiar hysteresis loops, the loops and the dielectric properties were examined under various conditions. It was found that specimens of the foregoing composition exhibit a remarkable aging effect at room temperature. The double hysteresis loop is explained as follows. Each small region in the specimen has an asymmetric hysteresis loop. The observed propeller‐shaped hysteresis loop is the result of random superpositions of all these asymmetric hysteresis loops. Experimental results show that the asymmetry of the elemental hysteresis loop originates in an interaction between two phases which are formed as the aging proceeds. A phenomenological theory is developed in which the effects of the mutual interactions between the two phases are considered. This interaction causes the elemental hysteresis loops to be asymmetric. The theory succeeds, at least qualitatively, in explaining the main features of the observed facts.
Directional Hardness of Strontium Titanate by Peripheral Grinding
Authors: GIARDINI A. A. , CONRAD M. A.
Published: June 2006

A study has been made of the directional variation of grinding hardness in strontium titanate. The method used is that of peripheral (zonal) grinding on oriented thin single‐crystal disks. A significant anisotropy, consistent with the m3m symmetry of the crystal structure, has been observed. Experimental data are presented in detail for the three principal zones: [100], [110], and [111].
Factors Affecting Sinterability of Oxide Powders:BeO and MgO
Authors: QUIRK JOHN F.
Published: June 2006

Data on the sintering of BeO and MgO were reviewed with reference to the diffusion sintering model devised by Kuczynski and Herring. Sintering rates for compacts of the dead‐burned oxide powders were in agreement with the bulk diffusion model with grain‐boundary sinks, but those of the active low‐calcined powders were not. During isothermal sintering the low‐calcined powders had very high initial shrinkages, after which the shrinkage rate was low, corresponding to a rate index of about 10. The initial high rate was ascribed to crystallization and coalescence of the material comprising individual particles. The activation energy associated with the sintering of active BeO was estimated as 249 kcal. per mole.
Phase Equilibria in the System CaO‐Iron Oxide‐SiO2, in Air
Authors: PHILLIPS BERT , MUAN ARNULF
Published: June 2006

Phase equilibrium relations in the liquidus temperature region of the system CaO‐iron oxide‐SiO2 in air were determined, using the quenching technique. The results are illustrated by means of a projection of the liquidus surface onto the composition triangle CaO‐Fe2O3‐SiO2. A supplementary diagram is presented in order to indicate true compositions of liquids at liquidus temperatures. Data obtained in the present investigation are combined with literature data to construct diagrams showing stability relations among crystalline phases at subsolidus temperatures. A diagram is also presented to show phase relations along the join CaO SiO2‐2CaO Fe2O3.
Permeability of Blast‐Furnace Refractories
Authors: EUSNER G. R. , SHAPLAND J. T.
Published: June 2006

The permeability of refractories is a governing factor in the deterioration of blast‐furnace linings by liquids and gases. Permeability tests there fore were performed on 17 carbon, 11 mullite, 85 castable, and 7 super‐duty and 11 high‐duty fire‐clay brands. The rate of gas flow was measured through a 2‐in. cube in three directions by using an improved laboratory permeameter. The range and mean of permeability in centidarcys for each class of refractory were as follows: carbon, 0.3 to 42 (20); mullite, 7 to 158 (48); castable, 0.2 to 43 (4.5); super‐duty fire‐clay, 28 to 207 (76); and high‐duty fire‐clay, 33 to 147 (72). The permeability of the different axes of the brick usually varied widely, with the face axis usually exhibiting the lowest values. The improved permeameter should prove to be especially valuable for determining resistance to gas flow and for controlling the quality of refractories.
Precipitation in Microscopic Cracks
Authors: PULLIAM GEORGE R.
Published: June 2006

It is shown that precipitation occurs in Griffith‐type surface cracks in solids from solutions or from vapors under conditions in which a plane surface would be dissolved or vaporized. A reduction in the equilibrium vapor pressure at the crack tip from that of a plane surface is produced by the driving force to reduce the surface energy of the crack. An equation is derived relating vapor pressure at the tip of the crack to vapor pressure over an infinite plane. This relation is used in deriving an expression for the fill‐up of cracks with time. Experimental data on the measurement of the retreat of the crack edge with time appear to be in good agreement with the derived expression. A discussion of the effect of such crack healing on the mechanical properties of the solids is included.
Reactions in the System TiO2‐P2O5
Authors: HARRISON DON E. , HUMMEL F. A.
Published: June 2006

The system TiO2‐P2O5 was investigated in the compositional range TiO2.P2O5 to 100% TiO2. Two compounds exist, TiO2.P2O5 and 5TiO2.‐2P2O5. TiO2.P2O5 begins to lose P2O5 at 1400°C. and both fusion and vaporization proceed rapidly at 1500°C. 5TiO2.2P2O6 melts congruently at 1260°± 3°C. to a glass which can be retained in substantial quantities at room temperature. Physical properties of certain compositions are described.
Investigation of Role of Beta Alumina in the System Na2O‐Al2O3‐SiO2
Authors: DE PABLO‐GALAN LIBERTO , FOSTER WILFRlD R.
Published: June 2006

Beta alumina was once considered to be merely a metastable polymorph of corundum. Its status as a distinct and stable compound (Na2O.‐11Al2O5 and analogous formulas) is now quite firmly established. Yet the published phase diagram for the system soda‐alumina‐silica takes no cognizance of its existence. A study of the alumina‐rich portion of the system was conducted to determine whether or not beta alumina should be incorporated in the diagram. Conventional methods of investigation were used, with certain innovations designed to overcome difficulties inherent in the system. Solid‐state sintering and modified quenching techniques were utilized to minimize soda loss. Sintering was at 1400°C. or thereabout, in platinum envelopes which were immersed in buffering mixtures so as to reduce volatilization. To the same end, extra‐large quenching charges were employed, and these were held at 1600°C., far below the liquidus temperatures of most of the mixtures studied. Phase identification was primarily by the X‐ray powder method. The results of these studies confirm the status of beta alumina as a discrete compound, and are believed to justify the insertion of an additional tie line, linking beta alumina to carnegieite, in the soda‐alumina‐silica diagram. A large primary field of beta alumina, occupying a portion of the present corundum field, is also strongly indicated. The phase diagram accordingly has been modified so as to incorporate these latest findings. The revised diagram, although in some respects tentative, is believed to be in fuller accord with technological experience. It is believed also to be in complete agreement with all recent laboratory studies in the system lime‐soda‐alumina‐silica.
Effect of Impurities on Electrical Solid‐state Properties of Barium Titanate
Authors: PULVARI CHARLES F.
Published: June 2006

Results are presented in which BaTiO2 single crystals with various impurity additions were grown and their effect on crystal quality, switching behavior, and electrical solid‐state properties was investigated.
Dependence of Mechanical Strength of Brittle Polycrystalline Specimens on Porosity and Grain Size
Authors: KNUDSEN F. P.
Published: June 2006

An empirical equation form, approximating the apparent dependence of the strength of brittle polycrystalline specimens on the combined effect of porosity and grain size, has been developed from concepts and data in the literature. The form is shown to be applicable to data for thoria and chromium carbide specimens.
On the Growth of Alpha Aluminum Oxide Platelets from the Vapor
Authors: MAY JOHN E.
Published: June 2006

The formation of alpha aluminum oxide micro‐crystals on objects heated in resistance furnaces with an aluminum oxide tube and a hydrogen atmosphere is reported. It is deduced that the crystals grow from the vapor produced by the reaction between the aluminum oxide furnace tube and the hydrogen atmosphere. Evidence for growth by the screw dislocation mechanism is presented.
Subsolidus Reactions in the System Fe2O3‐ TiO2
Authors: KARKHANAVALA M. D. , MOMIN A. C.
Published: June 2006

A study has been made of the binary system Fe2O2‐TiO2 by solid‐state reactions under dry and hydrothermal conditions. Under dry conditions only one binary compound, pseudobrookite (Fe2O3‐TiO2), was formed and no evidence of solid solution on either side of this compound at temperatures up to 1200°C. was obtained. The system under these conditions is a simple binary with a single binary compound. Under hydrothermal conditions of 300° C. and 1200 Ib. per sq. in. the system is apparently also binary, with a single unstable compound closely resembling, if not identical with, the naturally occurring mineral arizonite (ferric metatitanate, Fe2(TiO3)3).
Thermal Chemistry of Colloidal Titanium Dioxide
Authors: SULLIVAN WILLIAM F. , COLE SANDFORD S.
Published: June 2006

Chemical and physical analyses have shown that hydrous titanium dioxide, prepared from titanium sulfate solution, consists of flocculates of small anatase crystals. Water and sulfur trioxide appear to be present as adsorbed layers and in capillaries between and within the flocculates. During heating, loss of water occurs at about 150°C., loss of sulfur trioxide at about 650°C., crystallite and particle‐size growth at about 600°C., and the transformation of anatase to rutile in the range 700° to 950°C., depending on the method of preparing the samples. The kinetics of the transformation were found to be first order, following an induction time which appeared to depend on a nucleation process. Activation energies were of the order of 100 kcal. per mole and frequency factors of the order of 1020 to 1022 hr.‐1. Precision X‐ray diffraction studies showed that the anatase lattice expanded slightly before the transformation and that the initial rutile formed was expanded.
The Kaolinite‐Mullite Reaction Series: II, Metakaolin
Authors: BRINDLEY G. W. , NAKAHIRA M.
Published: June 2006

By applying single‐crystal X‐ray techniques, it is shown that kaolinite transforms to meta‐kaolin and subsequently to a cubic spinel‐type phase by a process of orderlyrecrystallization. The dimensional and directional relations between the phases are established. On the basis of this information, together with the density of metakaolin, a crystal structure is suggested for metakaolin. X‐ray examination of partly transformed kaolinite provides evidence for some long‐range regularity in the transformation process which is not shown by microcrystalline kaolinite.
The KaoIinite‐MuIIite Reaction Series: Ill, The High‐Temperature Phases
Authors: BRINDLEY G. W. , NAKAHIRA M.
Published: June 2006

X‐ray diffraction data for the high‐temperature phases show that a spinel‐type structure develops with marked orientation at about 925°C. This phase is considered to be an aluminum silicon spinel with vacant cation sites. Mullite is thought to be formed by the decomposition of the spinel. Silica is eliminated progressively as metakaolin transforms to the spinel phase and thence to mullite. The X‐ray data show variation in the mullite parameters between 1200° and 1400°C.; at 1400°C., the composition probably approximates 3A12O3·2SiO2. The nature of the intermediate spinel‐type phase is discussed in relation to the crystal chemistry of spinels.
Silica‐Uranium Fuel Systems
Authors: CASHIN W. M.
Published: June 2006

Presented are the irradiation results on two uranium‐silica systems: a uranium oxide Vycor‐brand glass system and a 10% uranium oxide glass prepared by melting. The glasses were irradiated up to 15% depletion of the uranium at temperatures up to the softening points with no appreciable loss of fission‐product gases. Included is an outline of a procedure for impregnating leached, unfired Vycor‐brand glass with uranium.
Study of Surface Durability of Container Glasses
Authors: SIMPSON H. E.
Published: June 2006

After containers were exposed to a controlled cyclic‐humidity test, the durability of their outside and inside surfaces was evaluated. All tests were made on containers as received; the determination of the influence of “finish” or constriction of the opening at the mouth of the bottle on the Surface durability therefore was possible. The study was enhanced by the use of replicas utilizing various electron microscope techniques. The results indicated that the smaller the opening of the container, the greater was the deterioration of the interior surface.
Electromechanical Properties of Lead Titanate Zirconate Ceramics Modified with Certain Three‐or Five‐Valent Additions
Authors: KULCSAR FRANK
Published: June 2006

When small amounts of lanthana, neodymia, niobia, or tantala are added to lead titanate zirconate compositions near the morphotropic (rhombohedral‐tetragonal) phase boundary, the modified ceramics show piezoelectric planar coupling coefficients of about 0.50 and substantially increased dielectric constants of up to 1545. The mechanical Q factor is decreased to about 70, and there is a marked increase in volume resistivity at temperatures up to 500°C. Other effects noted are better shelf‐aging characteristics, improved stability with respect to temperature dependence of resonant frequency, and a lowering of the Curie temperature. Except with neodymia, a definite refinement of the grain structure is also observed. By similar modification of Pb0.95Sr0.05(Zr.0.54 Ti0.45)O3 dielectric constants up to 1792 are obtained along with planar couplings of at least 0.49.
Dielectric Absorption in Ferroelectric Titanates
Authors: BROWN FIELDING
Published: June 2006

Dielectric absorption currents in ceramic Ba0.74‐Sr0.26TiO3 (Curie point 48°C.) have been measured from 7.5 seconds to 2 hours and from room temperature to 91°C. It has been found that irreversible polarization of domains contributes to the absorption in the ferroelectric region, and that the apparent change in activation energy for conduction, which occurs at the Curie temperature, may be associated with dielectric absorption effects rather than with a change in the width of the forbidden energy gap. Similar results have been found in other titanates.
Growth of Single Crystals of Incongruently Melting Yttrium Iron Garnet by Flame Fusion Process
Authors: RUDNESS R. G. , KEBLER R. W.
Published: June 2006

Single crystals of yttrium iron garnet (Y3Fe5O12) have been grown using the flame fusion process, even though the compound is reported to melt incongruently. The growth of these single crystals involves a mechanism different from that which has been proposed for the growth of single crystals of incongruently melting mullite. Crystal boules were grown at varying linear growth rates and analyzed with chemical, X‐ray, and metallographic techniques. With high linear growth rates, the samples are uniformly polycrystalline and three‐phase, containing Fe2O3, YFeO3, and Y3Fe5O12. When slow linear growth rates are used, single‐crystal Y3Fe5O12 can be grown. The mechanism is as follows: At the beginning of growth the first phase to precipitate is YFeO3, and during this stage in growth the molten cap becomes enriched in Fe2O3, compared with the Y3Fe5O12 composition. The liquid cap composition thus changes to the limit of the peritectic on the Fe2O3‐rich side, and Y3Fe6O12 then crystallizes from the bottom of the melt as Y3Fe5O12 powder is added to the top of the molten cap. The central sections of these boules are single‐crystal yttrium iron garnet.
A Structural Study of Talc and Talc‐Tremolite Relations
Authors: STEMPLE IRENE S. , BRINDLEY G. W.
Published: June 2006

About forty specimens of talc have been examined by X‐ray powder methods. Variations in the degree of crystallinity of the mineral have been observed, but no evidence has been obtained for polymorphic structural varieties. Single‐crystal data have confirmed the two‐layer mono‐clinic cell. Little evidence has been obtained of talcs containing mixed‐layer sequences. Electron micrographs have revealed a variety of platy and fibrous forms, and in the latter a close structural relation between talc and tremolite has been established. Talcs prepared synthetically in the presence of aluminum showed small lattice parameter differences from talcs prepared in the absence of aluminum, and the results are consistent with the substitution of small percentages of A1 ions in the talc structure. New X‐ray powder data and unit‐cell parameters for talc and tremolite are listed.
Surface Area and Exchange Capacity Relation in a Florida Kaolinite
Authors: ORMSBY W. C. , SHARTSIS J. M.
Published: June 2006

In connection with the study of certain properties of clay‐water systems, an investigation was made of the exchange behavior‐surface area relations of a series of controlled particle‐size (monodisperse) fractions of a domestic kaolin. Surface areas were estimated by application of the Brunauer‐Emmett‐Teller theory to low‐temperature nitrogen adsorption isotherms. Similar estimates were made based on room‐temperature water adsorption isotherms. Exchange behavior was studied using direct quantitative techniques involving the exchange of divalent manganese. Good correlation was found to exist between the computed Brunauer‐Emmett‐Teller areas and the exchange capacities over the particle‐size range 10 to 0.05 μ, equivalent spherical diameter. These results suggest that the exchange behavior in kaolinites is primarily a surface phenomenon and does not depend on isomorphous substitutions.
Magnetic Ceramics: VII, Effect of Iron Oxide Particle Size on Nickel Ferrite Formation
Authors: ECONOMOS GEORGE , CLEVENGER T. R.
Published: June 2006

Five iron oxides of increasing particle‐size distribution, mixed with nickel oxide of a constant‐size range, were heated at various temperatures and time intervals. The extent of nickel ferrite formation, as influenced by particle‐size distribution of the iron oxide constituent, was measured with a compensating‐coil magnetometer. Using the Jander relation for this type of reaction, activation energies ranging from 54 to 70 kcal. were computed for increasing particle size. These results are examined and compared with current procedures for the production of ferrite powders.
Sublimation of Cr2O3 at High Temperatures
Authors: WANG KE‐CHIN , DREGER LLOYD H. , DADAPE V. V. , MARGRAVE JOHN L.
Published: June 2006

The sublimation of chromic oxide, Cr2O3, has been observed in vacuum by the Langmuir technique using induction and solar heating. Extensive sublimation did not yield any new phases on the basis of X‐ray powder studies, and condensates of Cr2O3 were always obtained. Flash vaporization and flow experiments in CO or O2 atmospheres and in vacuum indicated no appreciable differences in rates of sublimation. Weight‐loss experiments showed that the rate of sublimation was slightly higher than predicted for decomposition to the elements and suggested that small amounts of complex molecules, e.g. CrO and CrO2, were also present in the equilibrium vapor.