摘要:

Residual surface stresses introduced into polycrystalline Al2O3during diamond grinding (320 grit) were examined by an X‐ray direction technique commonly used for metals. Compressive stresses, estimated to be in the range 135 to 170 MPa and to extend 15 μm deep, were observed at the surface. It is believed that the compressive surface layer coincides with the plastic layer produced by the elastie/plastic interaction of the abrasive grains with the ceramic. The results are discussed with regard to the effect of the compressive layer on the extension of surface crac

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb09996.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Continuous phase transitions were found to occur in ZrTiO4above and below a major discontinuity at 1125°±10°C. The space group of both forms of ZrTiO4is Pcnb. For specimens quenched from high temperatures, the volume of the unit cell decreases linearly from ∼1450°C to the discontinuity, with the major change occurring in the c axis. The volume decreases considerably at this temperature and continues to decrease with lower‐temperature annealing. Substitutional tin in solid solution stabilizes the high‐temperature struc

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb09997.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Densification studies of submicrometer ZrO2powders stabilized with 6.5 wt% CaO (CSZ) showed borate additions (1 to 10 wt%) to be effective sintering aids. Estimated densities>99% of theoretical were obtained on sintering at 1200°Cfor 4 h with 2 wt% B2O3or 5 wt% CaO·2B2O3additions to the CSZ powders. Average grain sizes obtained were typically<1 μm. Partial development of a monoclinic ZrO2phase was observed in the sintered samples. The amount of this phase varied from ∼7 to 75 wt% and was approximately linearly dependent on the additive concentration. The effect was most marked for the B2O3additions. Development of the monoclinic phase was attributed to progressive leaching of Ca from the CSZ phase by B2O3, in effect partially destabilizing the

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb09998.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Polycrystalline LaxSr1–xTiO3(0x0.01) was quenched following equilibration at 1325 K in oxygen activities within the range 10−20a0210−8. Electrical conductivity at 10 to 500 K supports an Sr vacancy model previously indicated by high‐temperature equilibrium measurements, with excess oxygen compensating the La donors for ao210−18and Ti site‐controlled valency conduction for stronger prequench reduction. Deductions about the reduced state from quenched‐condition conductivity are less straightforward than those obtained from high‐temperature measurements because of impurity scattering and impurity ban

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb09999.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A microstructure ranging from 5 to 20 nm in size was detected by small‐angle X‐ray scattering in Na2O·3SiO2and 4EaO·28Na2O·68SiO2glasses hydrated at ∼100° and 80°C, respectively. This observation suggests the presence of silica gel‐solvent (water) phas

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb10000.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Pitting in steatite ceramics was found to occur as a result of (1) deterioration with time, the familiar aging phenomenon, and (2) secondary recrystallization, which takes place immediately after fabrication. Differences in microstructural and other features observed in the two cases are pointed out.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb10001.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Values of KIcfor hot‐pressed AL2O3‐ZrO2composites were measured using notched‐beam and indentation strength techniques. The results are compared with K factors at the mirror/mist boundary and at crack branching. It was found that the indentation strength technique provides a more consistent estimation of KIc, than the notched‐beam te

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb10002.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Methods of improving the thermophoretic particle collection efficiency in optical‐fiber‐preform preparation are considered. One‐hundred percent collection efficiency may be effected by maintaining the temperature gradient in the gas or by suitably tailoring the initial particle concentration. The deposition efficiency is calculated for a simple nonuniform inlet concentration to illustrate the latter

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb10003.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Hot‐pressed Si3N4samples were preoxidized and tested in stress rupture. The lifetime of preoxidized samples was compared to samples that were not pretreated; for the test conditions chosen, lifetime was shorter for the preoxidized sample

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb10004.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1983.tb10006.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY