摘要:

Studies of Al2O3particles impacting (111) silicon single crystal surfaces at normal incidence show that the initial shape or transient in the weight loss vs dose curve depends on the condition of the surface prior to erosion. If the surface is pre‐eroded by particles larger than the incident particles, a decelerating transient is observed, while an accelerating transient is observed when the surface is pre‐eroded by particles smaller than the incident particles. The transient effects can be used to describe the results of mixing experiments when two sizes of particles are used simultaneou

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09905.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A fracture mechanics analysis is presented to study the effect of collinear crack interaction on the crack stability and propagation behavior in a brittle material subjected to thermal stress failure. It is shown that collinear crack interaction may result in crack coalescence and complete failure.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09906.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Plasma‐sprayed alumina coated on 316L stainless steel and Ti‐6A1–4V ELI substrates was aged in deionized‐distilled water, saline solution, Ringer's solution, and medium‐199. Reduction in adherence was observed after aging in all media with statistical analysis indicating at least two different processes occurring in the tensile pull‐off (adher

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09907.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Differences in the Raman spectra of various heat‐treated TiO2· SiO2glasses could be related to their thermal and chemical histories. For instance, while rutile could be detected in batch‐prepared glasses heated at 1100°C, only α‐cristobalite could be detected in heat‐treated devitrified flame‐prepared glasses with comparative TiO2‐concentrations. Thermal expansion coefficients increased for batch‐prepared glasses upon heat treatment due to exsolution of rutile from the glasses. Earlier work had noted similar behavior at lower temperatures due to exsol

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09908.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

An expression is developed for the slow growth of radial cracks after indentation using established notions of slow crack growth and residual stresses at the tip of radial cracks. This expression is substantiated by data gathered on indentation of microscope slides tested in air and water environments. The agreement is reasonable with the published values of the glass stress‐corrosion susceptibility coefficients. It is suggested that the present approach represents a simple and straightforward method of measuring the stress‐corrosion susceptibility of glas

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09909.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09910.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

High‐temperature thermoelectric power was measured on single‐crystal samples of wustite in equilibrium with a carbon dioxide‐carbon monoxide atmosphere. These measurements were made using a “heat pulse” technique which allowed the thermoelectric power of a sample to be determined in seconds. The short time required for this measurement precluded any possibility of an ionic contribution to the measured thermoelectric power. The results of this study are similar to those of earlier workers in that the measured thermoelectric power changed sign from positive to negative with increasing defect concentration. A defect model for wustite is proposed to explain these results. This model assumes a defect structure dominated by clusters of four vacancies coordinated around a trivalent iron cation in a tetrahedral position. Due to the high negative charge of such a cluster, electron holes are trapped in octahedral sites adjacent the cluster vacancies. Conduction occurs through the thermally activated hopping of these trapped holes between cluster near‐neighbor sites. The high defect concentrations in wustite result in these near‐neighbor sites being shared between different clusters. It is therefore possible for a given electron hole to hop through the crystal on a continuous path of near‐neighbor sites. A modified Heikes‐type equation is used to show that such a model is consistent with the measured values of the thermoelectric power. The proposed model is qualitatively consistent with other studies using X‐ray and neutron diffraction, electrical conducti

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09891.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Two special types of anhydrous aluminum sulfate with extreme grain shapes were prepared; one, obtained by precipitation from concentrated sulfuric acid solution, is rhombohedral near cubic single‐crystal grains and the other, from acetic acid solution, consists of very thin flaky particles. The morphology of sulfate and calcined alumina, the sulfate decomposition, the η‐α alumina transformation, and the crystallite growth of α alumina were studied and compared with those processes for reagent‐grade sulfate. The morphology of anhydrous sulfate was shown to greatly affect the heat‐treatment characteristics of alumina and the sulfate decompositio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09892.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Raman spectra were measured on B2O3‐SiO2glasses heat‐treated at different temperatures and for different periods of time. It was found that the intensity ratio of the 810‐ and 475‐cm−1bands depended on the thermal history and composition of glass. The intensity vs heat‐treatment temperature curve exhibited a maximum in the glass‐transition temperature range. High‐temperature Raman spectra were measured on 0.5B2O3‐0.5SiO2glass, both with increasing and decreasing temperature, between room temperature and 600°C. Above 300°C with increasing temperature, the intensity of the 810‐cm−1band decreased, whereas the intensity of the 475‐cm−1band increased. The changes reversed with decreasing temperature. The reversible change of the intensity of the two bands was interpreted as a reversible formation and decomposition of boroxy rings with temperature. The reaction becomes very sluggish below the glass transition so that the intensity ratio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09893.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Scanning electron microscopy and electron probe micro‐analysis were used to investigate the microstructure of both slow‐cooled and quenched polycrystalline BaTiO3specimens with a small excess of TiO2(Ba/Ti=0.995 to 0.999) or of BaO (Ba/Ti=1.002 and 1.005). The electron micrographs of polished and etched TiO2‐excess BaTiOs samples, and of fracture surfaces of quenched samples, showed a second phase in the grain boundaries and triple‐point regions, whereas no second phase was observed in samples having Ba/Ti=1.000. Microprobe analysis of the second phase gave compositions near that of the reported adjacent phase of higher TiO2content, Ba6Ti17O40. The results indicate that the solubility of TiO2in BaTiO3is<0

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1981.tb09894.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY