ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14381.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14382.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Chemical mechanisms which could be active in the wear process are reviewed. Identification of mechanisms present in the wear of single‐crystal sapphire spheres on steel has been attempted by examining worn surfaces and wear debris with the electron microscope. The reaction of iron oxide with aluminum oxide is confirmed by electron and X‐ray diffraction of the debris removed from the steel. The variation of instantaneous interface temperatures as detected by radiation pyrometry was correlated with the location of the wear debris on the wear tr

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14383.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Rapidly cooled castings formed from certain liquids in the system Mg0‐MgA1204 are observed to have an enrichment of the low‐melting spinel in the early solidified skin of the casting. Periclase, the high‐melting phase, is concentrated in the core of the casting. Following the metallurgical literature, an explanation for this nonequilibrium phenomenon, known asinverse segregation, is advanced which involves volume contraction upon solidification and flow‐back of residual, spinel‐rich liquids along interdendritic channels to the contraction volumes. The dependence of phase segregation on cooling history is discussed. Inverse segregation is negligible near the eutectic and extreme near the 70 wt% MgO conc

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14384.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The relation between refractive index and elastic modulus is found to be a sensitive indicator of the nucleation and separation of submicroscopic phases in glass. In a study of the changes in properties with heat treatments of a wide variety of glasses containing SOa, B20s, and ZnO as major constituents, it was observed that large decreases in Young's moduli were not accompanied by decreases in refractive indices of the magnitude usually observed. The abnormal changes in properties resulted from a sequence of two heat treatments. The results indicate that during the first heat treatment an immiscible phase is nucleated which, on subsequent heat treatment at a higher temperature, develops into heterogeneous regions producing changes in the relation between the refractive index and the elastic modulus.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14385.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The phase relations in the system U02‐U03‐Yz03, particularly in the Y203‐rich region, were examined by X‐ray and chemical analyses of reacted powders heated at temperatures up to 1700°C in H2, CO2‐CO2and air. Four phases were identified in the system at temperatures between 1000° and 1700°C: U308, face‐centered cubic solid solution, body‐centered cubic solid solution, and a rhombohedral phase of composition (U,Y)7O2ranging from 52.5 to 75 mole % Y2O3. The rhombohedral phase oxidized to a second rhombohedral phase with a nominal composition (U,Y), at temperatures below 1000°C. This phase transformed to a face‐centered cubic phase after heating in air above 1000° C. The solubility of UO, in the body‐centered cubic phase is about 14 mole % between 1000° and 1700°C but decreases to zero as the uranium approaches the hexavalent oxidation state. The solubility of Yz03 in the face‐centered cubic solid solution ranges from 0 to 50 mole % Y2O3 under reducing conditions and from 33 to 60 mole % Y2O3 under oxidizing conditions at 1000°C. At temperatures above 1000° C, the face‐centered cubic solid solution is limited by a filled fluorite lattice of composition (U,Y)O2. For low‐yttria content, oxidation at low temperatures (<300°C) permits additional oxygen to be retained in the structure to a composition approaching (U,Y)O2.25A tentative ternary phase diagram for the system UO2‐UO3‐Y2O3is presented and the change in lattice parameter and in cell volume for the solid‐solution ph

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14386.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Large‐scale grain‐boundary movements, apparently due to temperature‐gradient zone melting, have been observed in macroscopic LiF bicrystals. Bicrystals containing bodndaries of varying orientations were prepared by sintering LiF single crystals at temperatures 20’to 3O° C below their melting point in air and in argon. Although no appreciable amount of sintering was observed during prolonged heating periods at very slightly lower temperatures, at these temperatures a boundary capable of large‐scale movement formed rapidly. Subsequent heating at the same temperature resulted in boundary movements of 5 mm or more within 12 hours, frequently in a direction opposed to the radius of curvature. In some specimens boundary sliding and rotation, strongly suggestive of the presence of an inter‐facial liquid layer, w

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14387.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

X‐ray diffraction, electron microscopy, and infrared spectroscopy were used to study the changes in BeO powders produced by the calcination of basic acetate‐derived Be(OH)2. Weight loss, hydroxyl ion content, particle configuration, and crystallite growth were observed as a function of increasing calcination temperature. Low‐temperature calcining (375°C) formed Be0 showing the theoretically predictable weight loss and very little water present. The size of the beryllia crystallites increased with increasing calcination temperature, but the size and shape of the particles remained constant. Basal‐plane stacking faults were observed in the cal

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14388.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The constitutions of binary alkali halide systems are considered for the fluorides, chlorides, and bromides of lithium, sodium, and potassium. These systems are divided equally into those that are simple binary systems having a common ion and those that are capable of double decomposition into reciprocal salt pairs, AB + CD ⇌ AD + BC. The simple binary systems having been examined previously, the present work was principally concerned with the constitution of the pseudobinary systems. Using thermal analysis, X‐ray methods, and microscopy, the liquidus and temperature horizontals were determined for 18 such systems and the equilibria were interpreted with reference to quaternary systems. The tendency of a given salt pair to precipitate the reciprocal salts may be related to the relevant lattice energies. Microscopic examination of directionally frozen specimens revealed that true binary eutectic mixtures freeze with regular two‐phase distributions very similar to those observed in metallic eutectics; these distributions are illust

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14389.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

This is Part I of a two‐part series on space charge in glass. This part is primarily a review and covers the general nature of the observed phenomena, the relation of these phenomena to usual concepts such as dielectric constant and electrical conduction, and the present understanding of these phenomena in glass. This review serves to describe the background and motivation for the work set forth in Part 11, which is a discussion of recent theory and experiment on space charge in glass. Areas for further investigation also are suggeste

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14390.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY