ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13812.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

An effort was made to determine the cause of high dielectric losses at 106cps and 25°C in dense, essentially alkali‐free, high‐alumina bodies. Emphasis was placed on secondary crystalline phases in the fired bodies. The flux systems BaO‐SiO2, CaO‐MgO‐SiO2, and SrO‐SiO2were investigated. All high‐alumina bodies having high dielectric losses contained one of the synthetically formed feldspars, BaO.Al2O3.2SiO2, CaO.Al2O3.2SiO2, or SrO.Al2O3.2SiO2. The mechanism by which the feldspars caused the high dielectric losses was tentatively attributed to thermal expansion mismatch. The expansion curves of the feldspars were similar, but they were lower than the expansion cu

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13813.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The magnetic and dielectric properties of some ilmenite‐hematite solid solutions are reported. These properties resemble those of the ferrites. Compositions possessing high electrical resistivities and low dielectric losses were prepared. The introduction of manganese into the system (1 ‐ x)Ni1‐vMnvTiO3+ xFe2O3increases the room temperature magnetic moments and decreases the resistiv

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13814.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The changes in Young's modulus brought about in various glasses by exposure to irradiation in a nuclear reactor are reported. These changes are a function of glass composition and particularly of the alkali content. The proposed interpretation of the changes observed at low doses is based on comparisons with the temperature ratio of Young's modulus and consideration is given to both a “hot” structural configuration and a rearrangement in cation sites. The changes observed at higher doses are explained by an increase in the specific gravity due to compaction and those at very high doses by temper

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13815.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The transformation from one resistance state to another by glasses in the system As‐Te‐I is discussed and a model is postulated. The anomalous behavior of the electrical properties of glasses in this system is shown to result from thermal breakdown of the dielectric during which reversible glass‐to‐crystal phase transformation occurs. Results of compositional studies and the measurement of the electrical characteristics of resistivity, Seebeck coefficients, and current‐voltage curves are given. Resistivities of 103to>107ohm‐cm and Seebeck coefficients of +800 to ±4300μv per OC were measured for glasses i

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13816.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Dielectric measurements and direct‐transmission electron microscopy were used to analyze the phase separation and alteration in sodium borosilicate glasses. Metal impregnation of the glasses after leaching was particularly useful in observing the topology of separated phases whose characteristic dimensions are about 100 A. The results indicate that borosilicate glasses such as Vycor and Pyrex are fully phase separated when rapidly cooled from the melt and that subsequent heat treatment serves only to alter the structural characteristics of the separated phases. The topological characteristics of the initially segregated phases suggest that phase separation may occur by spinodal decompositio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13817.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The coloration produced by X‐irradiation in silicate glasses prepared under oxidizing and reducing conditions was studied. These glasses differed both in the position of the absorption maximums and in the thermal stability of the color centers formed. Maximums were observed at 4.10, 2.70, and 1.96 ev in oxidized glasses and at 2.15 ev in reduced glasses. Additions of a wide variety of cations to the basic glasses modified the coloration produced by X‐irradiation. These modifications appeared as new centers or in the enhancement or reduction of coloration produced by X‐irradiation in the base glasses. The reduction of ions such as Ce4+, Eu3+, and Yb3+by X‐irradiation is observed. Although several of the color centers appeared to be associated with the glass network itself, there was some correlation between the added cations and the coloration of the glass by X‐ir

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13818.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Relative grain boundary energy measurements were made by the tracrystal method for [100] tilt boundaries in NaCl. The dependence of boundary energy on grain misorientation was similar to that in metals; however, the presence of significant torque term effects, i.e. dependence of the boundary energy on boundary orientation, is indicated. A method of measuring the relative magnitudes of the torque terms by applying a driving force to boundaries in bi‐crystals is describe

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13819.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The mechanical behavior of high‐purity (greater than 99.9%) polycrystalline MgO, with relative density exceeding 9875, is described. By fracto‐graphic techniques, it was determined that inter‐granular cracks initiate fracture. These cracks originate from the extension of surface flaws into the MgO and are particularly severe in areas of high, localized, intergranular porosity. Ceramic machining techniques, such as diamond sawing and lapping with coarse abrasives, induce these surface flaws and limit the strength of MgO. The effectiveness of lapping, thermal conditioning, and chemical polishing techniques in removing these flaws and producing a substantial increase in mechanical strength is shown to be dependent on grain size and por

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13820.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Compositions in the system Fe2O3‐FeO‐BaO in the vicinity of the compound BaFe12O19were studied at temperatures from 1300° to 1550°C and oxygen pressures from 10−2to 102atm. Equilibrium relations involving several barium ferrous ferrites are described. Barium ferrite can be crystallized congruently from the melt at 40 atm oxygen pressure and

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb13821.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY