摘要:

Because of their method of preparation, ceramics contain point defects, the concentration of which may vary from the center to the boundary of the grains, which may change the bulk properties of the material. The electronic structure of the oxygen‐related defects has been studied by electron spectroscopy in yttria ceramics submitted to various heating conditions under controlled atmospheres. The differences in the mechanical and electrical behaviors are observed to correlate with the defect conten

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06418.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Two glass/alumina composites were examined as potential systems for stress‐induced microcrack toughening. A borosilicate glass/alumina material having a thermal mismatch strain of approximately 0.8% demonstrated toughness up to twice that of an aluminosilicate glass/alumina composite and other reported glass/alumina composites. High‐sensitivity density measurements confirmed a density reduction on application of a stress in the borosilicate glass/alumina system, providing indirect evidence for stress‐induced microcra

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06419.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Polycrystalline, Al‐doped samples in the TiO2‐SnO2ceramic system were made and annealed in the two‐phase field above the [001] coherent spinodal. The samples were examined, after various annealing times, using X‐ray diffraction and Raman spectroscopy. It was observed that time constants obtained from X‐ray studies were in good agreement with those obtained from Raman shifts, and both showed similar effects of grain size on the decomposition kinetics. These results suggest that Raman spectroscopy may be a useful technique for the study of phase transformations in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06420.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The formation of ZnAl2O4spinel in diffusion couples of Al2O3and ZnO was investigated between 1000° and 1390°C in air and in air containing 4.8 vol% Cl2by X‐ray diffraction, electron probe microanalysis, and scanning electron microscopy. The rate of formation of a spinel layer obeyed a parabolic rate law and was accelerated remarkably by the presence of Cl2. The interdiffusion coefficient, D̃, and the activation energy, E, were calculated to be 10−8to 10−9cm2/s and 123 kcal/mol (514 kJ/mol) in air and 10−7cm2/s and 31 kcal/mol (130 kJ/mol) in air containing 4.8 vol% Cl2, re

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06421.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The molecular interactions that act to stabilize a colloidal dispersion in solutions containing phosphazene trimers or polymers were investigated using31P nuclear magnetic resonance spectroscopy.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06422.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Local sintering rates were measured in two‐dimensional, ordered and disordered structures constructed from glass spheres. In ordered arrays, made from monosized spheres, the local sintering rates varied from 1/2 to 2 times the average sintering rate. In contrast, disordered arrays, made from bimodal particle sizes, sintered more homogeneously, the local sintering rate deviating less than 15% from the average. The total average densification strain was also greater for the disordered structures. As a result, for the same time and temperature cycle, the disordered structures sintered to near full density while the ordered structures did not. Poor densification in the ordered structure was attributed to packing defects such as domain walls and dislocations. Some evidence was obtained for a correlation between densification and the average coordination number of particle

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06423.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Most zirconia‐based toughened ceramics need specialized processes to achieve their desired properties. In this paper, we report the fabrication of toughened ceria‐stabilized tetragonal zirconia polycrystal by conventional processing, i.e., ball milling and cold‐pressing followed by sintering. We believe that ball milling works here because a somewhat coarser particle size is actually beneficial in this case. Although the samples were not fully dense (they need not be), a composition of ZrO2‐12 mol% CeO2yielded a fracture toughness value of 14.1 MPa·m1/2. This is comparable to values reported for materials processed by specialized techniques and can be rationalized in terms of R‐curv

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06424.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06425.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06426.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1988.tb06427.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY