摘要:

This paper reports the minimum concentrations of second cations that must be added to phase‐separated binary borates to produce single‐phase glasses when batches of approximately 100 gm. are melted at 1300°C. and poured into an 8‐ by 10.5‐cm. steel mold at room temperature. Surface tensions are also reported for the melts at 900°, 1000°, 1100°, 1200°, and 1300°C. Alkali and alkaline‐earth cations and Pb++, Cd++, and Al+++were used as auxiliary cations to make single phased the phase‐separated binary borates of the principal cations Ba++, Sr++, Ca++, Cd++, Zn++, and Mg++. Within any group of the periodic table the minimum homogenizing concentration increases with decreasing ionic radius of either the auxiliary or the principal cation. The surface tensions of layered binary melts are independent of cation identity and content, indicating an upper layer of nearly pure B2O3. For layered or unlayered ternary melts containing alkali auxiliary cations, surface tension increases with increasing cation content at rates that decrease with the ionic radius of either cation, indicating that in these layered ternary melts the cations enter the upper (B2O3‐rich) layer more freely than in the corresp

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12906.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The solubility and solution rates of porous glass and silica gel in nitric acid solutions at 95°, 65°, and 36° C. were determined. The solubility depends on the acid concentration, decreasing with increasing strength of free HNO3in accordance with the following equation: logC = ‐aN ‐ b, whereCis the silica solubility,Nis the acid normality, andaandbare empirical constants. The rate of solution of silica depends on acid concentration, the initial rate being a maximum at about 0.8N.The amount of silica dissolved is a function of time and acid concentration. For short periods of time (1 to 40 hours) a maximum amount of silica is dissolved in about 0.8NHNO3. For long periods of time this maximum is at 0.1Nor less. A curve showing the decrease in silica solubility with temperature in water is in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12907.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The collective effects of the reaction products on the reaction between water and soda‐lime‐silica glass were studied by investigating the reactions of the glass with each individual reaction product. The rate‐controlling processes in the reaction between water and the glass are considered to be the diffusion of cations and the breakdown of the glass network. A qualitative description of the mechanism of the reaction between the glass and water is sugg

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12908.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The sulfate side of the phase diagram of the system NazSO4‐Na2SiO3has been investigated by means of a high‐temperature filtration technique. On the basis of the measurements obtained it is concluded that the metasilicate forms rings of four tetrahedra when dissolved in sodium sulfate. The results for this system are compared with data from other related silicate‐containing mix

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12909.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The experimental results given in this paper show that (1) alumina lost oxygen when heated at 1400° to 1500°C. in water vapor but retained its weight unchanged when heated in air or in nitrogen and (2) kiln gases dissolved in a mullitic material at temperatures between 800° and 1200°C., and their solubility increased with temperature. These separate facts verify two theories that often have been suggested to explain the effect of the composition of the kiln atmosphere, viz., that(a)deviation from the stoichiometric composition occurs in stable ceramic oxides, such as Al2O3, at moderately elevated temperatures, even though the ambient gas phase does not affect the ceramic oxide in the ordinary chemical sense, and (b) lattice defects are caused by the solution of gases in the ceramic oxides. The frequency of lattice defects is assumed to depend on the surrounding gas ph

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12910.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

It is demonstrated experimentally that even in the purest laboratory silicas available the temperature of the α‐β inversion in cristobalite is variable and depends on the structure of the starting material and on the temperature and length of heat‐treatment. It is shown that this variability is an index of the order achieved in the cristobalite structure quite independent of impurities. There is no specific order characteristic of a particular temperature; the completely ordered 3Cstacking of cristobalite is the most stable cristobalite throughout the temperature range and has an α‐β inversion temperature of 267°± 2°C. All disordered cristobalites will tend toward the3C267° cristobalite with time. The conversion of cristobalite to tridymite involving the 3C→2H stacking change doesnotalter the cristobalite inversion temperature, nor have any regular polytypes other than those recognized as tridymite b

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12911.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

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‐UF4and 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‐UF4four compounds have been identified. Two of these, 3KF.UF4and 7KF.6UF4, melt congruently at 957°C. and at 789°C., respectively. The compound 2KF UF4melts incongruently to 3KF.UF4and liquid at 755° C., and the compound KF.2UF4melts incongruently to UF4and 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.UF4and 7KF 6UF4at 608° C. Two other compounds, KF 3UF4and 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‐UF4mixtures 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.UF4and 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 % UF

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12912.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The precipitate formed during partial reduction of magnesium ferrite raises the coercive force by setting up high stresses in the ferrite matrix as a result of the difference in thermal expansion of the two phases. The slower the cooling rate, the smaller is the final stress and the smaller the influence on the coercive force. Only the magnitude and not the sign of the difference in thermal expansion is of importance, as is shown by making additions of inert phases with thermal expansions both larger and smaller than that of the ferrite. The maximum radial tensile stress set up in the ferrite by the reduced phase is approximately 40,000 1b. per sq. in. in a specimen air‐quenched from 1400° C. The formation of a reduced phase in magnesium ferrite is accompanied by a fourfold reduction of the residual porosity. It is not known whether this is the result of a change in stoichiometry of the ferrite with the development of an oxygen‐deficient structure and hence enhanced oxygen diffusion rate, or whether the reduced phase prevents grain growth until most of the vacancies have collapsed. The reoxidation of such a two‐phase material gives a polycrystalline material with greatly improved magnetic prop

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12913.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The sinterability of europium, samarium, gadolinium, and dysprosium pure oxides was investigated at various temperatures under both oxidizing and reducing conditions as well as hot pressing. Data are presented on the density, grain size, thermal expansion, resistance to water corrosion, and the microhardness of these oxides. Photomicrographs showing grain growth and microstructure are included. The results indicate that dysprosium oxide is the most stable of the four oxides investigated. It sinters with small grain size, is similar to alumina in coefficient of thermal expansion, and does not undergo a phase transformation.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12914.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1958.tb12915.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY