ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15670.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The reaction between nitrogen dissolved in chromium and a dispersion of magnesium aluminate particles in chromium at high temperatures is discussed. The equilibrium state for various nitrogen concentrations in a 94 chromium‐6 spinel mixture was investigated between 1200° and 1400°C. Experimental techniques included electron‐beam microprobe analysis and mass spectrometry. Partitioning of nitrogen between chromium and spinel was strongly in favor of the spinel. Mass spectrometry indicated coordination of nitrogen with magnesium in the spinel lattice. The spinel‐nitrogen reaction is important because it can prevent the embrittling of chromium by n

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15671.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Low‐temperature sintering of beryllium oxide powders from 300° to 1000°C was studied by measuring crystallite growth and changes in specific surface. Sintering is enhanced by the presence of water vapor. Adsorbed phosphate almost completely inhibits sintering up to 850°C, even in water vapor at 10

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15672.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The characteristics of spinels in the series MgCr2O4‐MgFe2O4were determined. The plot of cell size vs. molar composition is unusual in series showing complete solid solution because an unusually large deviation from Vegard's law was observed. This deviation is caused by changes in spinel structure with composition and temperature, and an equation was derived which applies a correction in terms of the degree of inversion. The effects of temperature on compositions high in MgFe2O4include changes in density and refractive index. Solid solution of forsterite in MgCr2O4decreases the cell size to 8.329 A but apparently is less than 1%. Changes in composition caused by vapor loss or by dissociation are small enough that this series is essentially binary below 1400°

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15673.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The dissolution and diffusion of the three oxides of iron in sodium disilicate glass from 900° to 1100°C were controlled by diffusion in the molten glass. Concentration profiles were determined with an electron microprobe. Diffusion kinetics were applied on the basis of an ideal binary couple with concentration‐independent inter‐diffusivities. Concentration dependence of the inter‐diffusivities was determined by the Boltzmann‐Matano method, and the resulting interdiffusivities were interpreted in terms of a ternary diffusion model. The relation among the self‐diffusion coefficients wasThe activation energy for the interdiffusion process for all the iron oxide‐sodium disilicate couple

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15674.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The properties of many sulfide and selenide glasses correspond closely to related oxide systems; this correspondence can be correlated with the ratios of the valences and of the radii of the anions and cations. The analogy of chalcogenides to oxides in phase separation behavior is striking. Systematic substitutions prove the validity of Zachariasen's rules for covalent materials. The glass‐former cations which tend to polymerize during cooling have a coordination number of 3 or 4. The comparison has been extended to network modifiers among the sulfides and selenide

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15675.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Crystals of In2O3grown from a PbO‐B2O3melt show habit changes and imperfections that appear to result from the growth mechanisms and the relative supersaturations in the melt. The habit of the crystals is {100} at high super‐saturations and {100} modified by {211} at low super‐saturations. Surface features indicate growth by two‐dimensional corner and edge nucleation followed by growth spirals caused by screw dislocations. Striations and trapped flux occurred in the crystals grown by corner and edge nucleation. The striations occurred in three zones, each of which was related to the growth mechanism and to the supersaturations. The frequency of the striations decreased when the primary mechanism changed from edge nucleation to screw disl

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15676.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The surface states of silica in the forms quartz, cristobalite, and silicic acid were studied by investigating the kinetics of para‐ortho hydrogen conversion and of hydrogen‐deuterium equilibration from 93° to 773°K. The products of conversion were analyzed by microthermal conductivity, and those of equilibration by mass spectrometry. The results are discussed in terms of the reaction mechanisms. The active sites for low‐temperature conversion are thought to be stable free radicals produced by the thermal removal of hydroxyl groups from the surfaces. Reactivity at high temperatures depends on thermal activation procedure and time. The order of reactivity for equilibration at all temperatures is: quartz>cristobalite>silicic acid. For conversion at low temperatures the order is: quartz>cristobalite>silicic acid; at high temperatures, cristobalite>quartz>silic

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15677.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The CdS‐MnS and CdSe‐MnSe phase diagrams were determined by lattice constant measurements, visual examination of quenched specimens, and DTA. Melting points are 1258°± 2°C for CdSe, 1397°± 2° for CdS, and 1460°± 8° for MnSe. The solid solution limit of MnS in CdS (wurtzite type) is 49 mole % MnS at 8007deg; and 447% MnS at 1385°; the limit of CdS in MnS (rock salt type) is 11.57% CdS at 800° and 37% CdS at 1390°. The solid solution limit of MnSe in CdSe is 50 MnSe at 700° and 44% MnSe at 1175°; the limit of CdSe in MnSe is 5% at 700° and 19% at 1265°. The phases recovered after application of high pressur

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15678.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Densification and grain growth rates at the intermediate stage of the sintering of pressed zinc oxide pellets were measured in air and oxygen. Application of a lattice diffusion model to the results gave calculated diffusion coefficients in good agreement with directly measured diffusion coefficients for zinc. The change of atmosphere from air to oxygen resulted in lowering of grain size and calculated diffusivity; the diffusion decrease is consistent with lattice diffusivity of zinc occurring by an interstitial mechanism. The results can be expressed by the relations:in air, andin oxygen, from 900° to 100°

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb15679.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY