ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11033.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

A study has been made of the microstructure of chromite spinel and its changes in basic refractory brick under service conditions. Part of the changes occurring resemble those described previously for slag‐free environments, frequently enhanced by extended periods of exposure. In addition, slagging by solid, liquid, and vapor phases produces interesting new spinel micro‐structures in open‐hearth furnace roofs and checker systems, in various furnaces of the copper industry, in rotary kilns and glass‐tank checkers, and in regenerato

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11034.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The dissipation factors and dielectric constants of alumina ceramics containing less than 100 ppm of impurities and of specimens doped with Si, Ti, Ca, Mg, Fe, and Cr ions were measured in the region 102to 8.5 × 109cps and 25° to 875° C. Multiple regression analysis of the data at 500° C and 106cps showed a linear relation between impurity concentration and tan δ, with a correlation coefficient of 0.93. Si ions caused the greatest rise of tan δ, Mg and Ti were second, Ca third, and Cr and Fe had no significant influence. These effects diminished with rising frequency and became negligible in the microwave region. Activation energies of conduction for pure and doped alumina were estimated from measurements of δ at 105cps and 500°C. Values between 1.2 and 1.6 ev were calculated for all compositions except the one containing Mg2+, for which 2.0 ev was obtained. At low frequencies, the dielectric constant (k′) rose exponentially with temperature, reflecting a similar rise in the number of free charge carriers contributing to interfacial polarization. At higher frequencies the temperature variation of k′ fell to a shallow positive slope of about 120 ppm per °C. This coefficient was not influenced by low concentrations of impurities but could be effectively compensated without excessive loss by additions of 10 t

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11035.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The liquidus‐solidus relations along the join Ca2SiO4‐Ca(OH), in the system CaO‐SiO2‐H2O have been determined at 1000 atm up to 1110°C. This join is binary and contains the calcium silicate hydrate, calciochondrodite, Ca5‐(SiO4(OH)2. Calciochondrodite melts incongruently to Ca2SiO2+ liquid (composition 23 wt% Ca2Si04) at 955°C. The eutectic between calcium hydroxide and calciochondrodite lies at 13% Ca2Si04and 822°C. Preliminary experiments, also at 1000 atm, in the ternary system CaO‐Ca2Si04‐Ca(OH), indicate that the eutectic at which the fields of primary Ca(OH)2, CaO, and Ca2(Si04)2(OH)2meet is close to the CaO‐Ca. (OH), side of the triangle at approximately 805° C. The ternary reaction point Ca2SiOl+ liquid ⇌Ca5(SiO4)2(OH)2+ CaO + liquid is believed to lie in the low‐CaO (<5%) high‐Ca(OH)2

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11036.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The Czochralski technique of pulling from the melt has been extensively used in the field of semiconductors. The criteria for its applicability are discussed and indicate that this technique should also be applicable to some of the high‐melting ceramic oxides and oxide compounds. In addition to the successful growth of large crystals of calcium tungstate, preliminary experiments were performed on several other oxides. A number of materials including ferrites, rutile, and barium titanate have been grown in single‐crystal form, and growth conditions are described. Crucible material and atmosphere control problems are also discus

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11037.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The steady‐state creep behavior of polycrystalline aluminum oxide from 97 to 100% dense has been examined at temperatures from 1600° to 1800°C over a range of stresses from 100 to 2000 psi under four‐point transverse bending. Grain size is shown to have an important effect on the deformation behavior. Stress‐strain rate dependence for the fine‐grained aluminum oxide (3 to 13μ) is of viscous behavior (°ε∼σ). The strain rate is also inversely proportional to the square of the grain size (°ε∼ 1/(GS)2). The creep behavior can be described by the Nabarro‐Herring diffusional flow model although the diffusion coefficient does not agree with that for oxygen diffusion in sapphire. When the grain size becomes coarse, the Nabarro‐Herring model no longer applies. Coarse‐grained aluminum oxide (50 to 100μl) behaves plastically when deformed (°ε∼σ). The strain rates observed on coarsegrained aluminum oxide are higher than one would predict from the deformation behavior of fine‐grained aluminum oxide. This plastic flow probably occurs through some disloc

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11038.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Tentative phase relations in the binary system BnOa‐A12O3are presented as a prerequisite to the understanding of the system Li2O‐B2O3‐Al2O3. Two binary compounds, 2A12O3.B2O3and 9A12O3.‐2B2O3, melted incongruently at 1030° f 7°C and about 144°C, respectively. Two ternary compounds were isolated, 2Li2O.A12O3.B2O3and 2Li2O. 2AI2O3. 3B203. The 2:1:1 compound gave a melting reaction by differential thermal analysis at 870°± 20° C, but the exact nature of the melting behavior was not determined. The 2:2:‐3 compound melted at 790°± 20° C to LizO.‐5Al2O3and liquid. X‐ray diffraction data for the compounds are presented and compatibili

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11039.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The density, refractive index, molar refractivity, and infrared absorption spectra of soda aluminosilicate glasses containing up to 34.8 wt% alumina have been determined. Changes in these properties with composition can be explained by existing theories which assume that the aluminum ions form only A104tetrahedra when the Al/Na ratio of the glass is equal to or less than 1. The aluminum ions in glasses having an Al/Na ratio larger than 1 are in both fourfold and sixfold coordination.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11040.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Internal friction measurements of soda aluminosilicate glasses, the physical properties of which were reported in Part I of this series, are discussed. The low‐ and intermediate‐temperature internal friction peaks were studied in detail and are shown to be due to the stress‐controlled movement of the sodium and nonbridging oxygen ions, respectively. A close correlation was found between the temperature shift of the low‐temperature peak and the activation energy for electrical conduction in the soda aluminosilicate glasses. The magnitude of the low‐temperature peak was found to depend more on the structural environment of the sodium ions than on the actual soda content. Changes in the intermediate‐temperature peak are explained on the basis of the structural model proposed for th

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11041.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11042.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY