ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13207.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

A search was made for evidence of metastable phase separation in binary alkali metal oxide‐silica glasses which had been subjected to the usual glassmaking procedures of melting, relatively fast cooling, and annealing. Electron microscopy and electrical properties measurements were the principal tools of investigation. Evidence for phase separation in Li2O and Na2O silica systems is given together with critical temperature estimates. Although K2O‐SiO2glasses showed some slight evidences of structural segregation it is concluded that binary K2O, Rb2O, and Cs2O silica glasses generally show simple solution behavior and allow reasonable correlations of properties with cation size, type, and separat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13208.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The Flory distribution of molecular weights of linear polymers resulting from the condensation of bifunctional monomers was used by Van Wazer to calculate the constitutions of thepoly phosphoric acids. Jost and Wodtcke proposed a modification to the Van Wazer approach for sodium phosphate glasses. By modifying and extending these ideas, it is shown that, by using a few empirical parameters, it is possible to calculate chain length distributions for polyphosphoric acids and polyphosphate glasses, which give a satisfactory fit to available data. These distributions are useful for smoothing and extrapolating data and for emphasizing deviations from the Flory distributions taken as “ideal

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13209.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

A fracture theory is proposed for a composite system based on a continuous glass matrix. It is hypothesized that hard crystalline dispersions within the glass matrix will limit the size of Griffith flaws and strengthen the composite. Quantitative relations are derived for the effect of a dispersed phase on composite strength. At low volume fractions of the dispersed phase, the average flaw size is statistically reduced independent of the size of the dispersed particles. At high volume fractions of the dispersed phase, the average flaw size is governed by the average distance between particles dispersed in the matrix. The strength of a composite should, therefore, be a function of the volume fraction of the dispersed phase at low volume fractions and dependent on both the volume fraction and particle size of the dispersed phase at high volume fractions. For verification of the theory, cross‐bending strengths were measured on a sodium borosilicate glass containing varying volume fractions of spheroidized alumina over a range of particle sizes. The average distance between dispersed particles ranged from approximately 15 to 500μ. Good agreement with theory was found. Values of glass surface energy calculated from the experimental data agree well with literature da

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13210.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The high‐temperature deformation of magnesia single crystals with a [110] tensile axis is described and related to previous observations on [001]crystals. The [110] tensile axis favors slip on systems with oblique vectors (i.e. at 120°). Two main modes of deformation are identified and distinguished by the interpenetrability of oblique slip: (1) Between 1400° and 1700°C interpenetration does not occur. The crystal becomes subdivided into distinct blocks slipping on different systems. These blocks are separated by sharp kink boundaries which act as barriers to further slip. Voids form in the kink interfaces and lead to brittle fracture. (2) Above 1700°C slip on all systems interpenetrates and a stable substructure develops throughout the gage section. At high strains the single crystal recrystallizes. The specimen work hardens and elongates 100% before necking down to completely ductile fracture. This behavior is discussed in terms of dislocation interac

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13211.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The microstructure of a series of lead borate glasses was studied by electron microscopy and small‐angle X‐ray scattering techniques. Although the glasses were optically homogeneous, microheterogeneities of the order of 2000 to 3000 A were detected in glasses with compositions near the region of two‐liquid stability. The size of these heterogeneities increased as the composition approached the region of immiscib

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13212.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Qualitative X‐ray diffraction of a fireclay brick revealed no major change in crystalline composition, other than the inversion of cristobalite, from room temperature to 1500°C. Methods of quantitative analysis of specimens at room temperature were considered. The internal standard technique of quantitative X‐ray diffraction was selected as the most reliable. Using this technique the effectiveness of quenching was investigated. Quenched analyses appear to be suitable for representing the constitution at high temperat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13213.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Quantitative X‐ray diffraction analysis of quenched specimens, supplemented by HF solution and X‐ray fluorescence, was used to determine the mineralogical composition of three refractory clays after heating at 1150° to 1500°C. The three clays represent a range of purity found in high and superduty fireclay refractories: an impure plastic clay, a flint fireclay, and a kaolin. The results show the percentages of mullite, cristobalite, quartz, and liquid. The quantity and composition of the liquid phase were estimated by difference. Iron and titanium oxide impurities in the mullite decreased with increased firing tempera

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13214.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The hot‐pressing characteristics of kaolin, fireclay, and plastic fireclay were determined between 1150° and 155O°C at 3000 to 10,000 psi under oxidizing conditions. Each clay could be pressed to near its true density at an optimum temperature. Insufficient temperature produced low bulk density; excessive temperature caused bloating. Synthetic glasses were prepared to represent the composition of the liquid phase estimated to be present at the optimum pressing temperature. Viscosities of the synthetic glasses were measured, and those of the optimum pressing temperature were estimated. The deformation characteristics are in reasonable accord with the Mackenzie and Shuttleworth hot‐pressing equation for viscous

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13215.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The diffusion of Be was measured in single crystals of BeO in directions normal and parallel to the hexagonalcaxis. The diffusion coefficients,D, in the two directions were nearly equal to each other. The values ofD, measured between 1500° and 2000°C were quite similar to values reported previously for high‐density, high‐purity, polycrystalline BeO. The single‐crystal data, taken in conjunction with polycrystalline data, show that the observed diffusion in polycrystalline BeO proceeds entirely by volume diffusion with no significant diffusion along grain boundaries, although there is some evidence of rapid surface diffusion along microcracks in the surface. The data are interpreted in terms of extrinsic impurity‐dependent diffusion via mobile

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13216.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY