摘要:

The effect of acetic acid on acid‐catalyzed tetraethyl orthosilicate (TEOS) hydrolysis has been followed with1H NMR. The changes in [CH2] and [CH3] of TEOS, [OH]of ethanol, and the formation of ethyl acetate are observed during the sequential addition of acetic acid. Mixed SNl and SN2 reaction mechanisms are proposed to explain the TEOS hydrolytic behavior by the esterification proces

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05640.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Indentation cracks show the initial decrease and subsequent increase in crack velocity with the stress intensity factor whether the cracks are single or coalescent. The decrease in crack velocity is mainly due to the residual stress effects. For two collinear cracks, the individual cracks before coalescence show crack velocity much higher than would be expected on the basis of the stress intensity factor for single or coalescent cracks.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05641.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Silicon carbide test bars were made by a simple wet‐processing technique. The pressure casting method used the same equipment as conventional dry‐pressing, but with a modified die. This casting technique was employed in order to produce test bars with improved strength and smaller fracture flaws than produced by dry‐pressing. This was accomplished by eliminating pore clusters which were present in dry‐pressed specimens and identified as a common source of failure in SiC MOR te

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05642.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Solubility of NiO in Al2O3was determined by electron probe microanalysisy A diffusion couple method was used by coupling an NiO‐doped Al2O3polycrystal to a pure single crystal of Al2O3. The solubility of NiO in Al2O3in air was 230 wt ppm (157 at. ppm of cations) and 170 wt ppm (116 at. ppm) at 2073 and 1973 K, respectively. The solubility of NiO in Al2O3obtained in this work was compared with our previous work of the solubility of MgO in Al2o

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05643.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A method has been developed to produce an arbitrary pattern with a minimum feature size of 5 μm in a thin particle film on a snbstrate. In this method, a layer of photoresist is spun onto a continuous, uniform ceramic film which is then exposed to ultraviolet light under a mask with the desired pattern. After development of the photoresist the regions of the film no longer covered with photoresist are removed by immersion in an ultrasonic bath. The vacant regions in this first layer can then be filled with a second material, and multiple layers can be built up by slight modifications to this procedure

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05644.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Experimental techniques for the deposition and sintering of ceramic particle films on a rigid substrate have been investigated. Three representative systems (SiO2, ZnO‐Bi2O3, and Al2O3) were chosen to determine the validity of the conceptual processing model. Crack‐free, sintered films 1 to 50 μm thick were produced using single or multiple deposition/sintering cy

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05645.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The mechanical behavior of silicon carbide exposed to molten lithium was evaluated at exposure temperatures from 200° to 1000°C. For temperatures up to 600°C, there was little change in strength and the fracture was controlled by preexisting surface flaws on the specimen surface or edges. Above 600°C, two strength populations developed: a relatively high‐strength group characterized by transgranular fracture and a low‐strength group characterized by intergranular degradation. Quantitative chemical analysis was used to explain the lithiuminduced strength degradation. This information, coupled with the fractographic analysis, led to a description of the corrosion me

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05646.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

When compacts of BaTiO3powder containing small amounts of uncombined TiO2were sintered, marked differences in microstructural evolution were observed under varying heating rates. In fast heating, the liquid formed during heating agglomerated at the center of the specimen and resulted in an inhomogeneous microstructure. A slower heating rate resulted in a homogeneous microstructure.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05647.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

An X‐ray method for the measurements of the thickness of supported thin films in the microprobe is modified for silica films on silicon nitride and silicon carbide. The intensities of the oxygen Kα line are measured on bulk SiO2and on the film. The derivation of the caliboration curve giving the thickness of the film from the ratio of these intensities is outlined. The method has been used for silica films thinner than 1 μm with a lateral resolution of a few micromet

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05648.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Oxygen self‐diffusion coefficients for a single‐crystal MgO doped with 400 ppm Li were determined at 848° to 1300°C by isotope exchange technique using18O as the tracer. The diffusion coefficient increased with increasing temperature in the lower temperature range, as described by D = 7.8 × 10−4exp[−279 (kJ/mol)/RT] cm2/s, which was interpreted to be an extrinsic diffusion due to the oxygen vacancies introduced by substitutional Li ions. The oxygen diffusivity tended to decrease above 1050°C, presumably becauuse of evaporat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05649.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY