摘要:

Previous results for ultimate tensile fracture strengths of partially stabilized zirconia (PSZ) containing preexisting finite cracks are reformulated in terms of a new transformation‐strengthening parameter. This allows a simplified method for estimating the strengths of bulk PSZ containing arbitrarysized, preexisting critical crack

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05566.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A thermochemical etching procedure, comprising a short chemical etch followed by a low‐temperature thermal anneal (typically 10 min at ≲70% of the sintering temperature), has proved successful for the preparation of alumina, aluminum nitride, and nickel zinc ferrite ceramics for micro‐structural studies. Good‐quality results have been achieved in times much shorter than those normally associated with chemical etching and at temperatures lower than those usually used for thermal etching. Under such conditions, grain growth and surface modification are believed to be

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05567.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Retrograde densification of pelletized calcines and glasses having an approximate (Bi,Pb)2Sr2Ca2Cu3O10starting stoichiometry and sintered at ∼850°C can be described by first‐order rate equations. Retrograde densification in the calcine precursors was largely due to the development of open pores, and was approximately proportional to the concentration of the (Bi,Pb)2Sr2CaCu3O10phase. In the glasses, retrograde densification is mainly caused by porosity accompanying the growth of a needlelike Sr─Ca─Cu─O phase, together with (Bi,Pb)2Sr2Ca2Cu3O10and (Bi,Pb)2

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05568.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Fully tetragonal and sintered 13 mol% TiO2─3 mol% Y2O3─84 mol% ZrO2was thermally treated at 1300°C for 1 h in argon in the presence of carbon. No phase changes occurred on the as‐received surface and in the bulk of the material, butt→mtransformation occurred on polished surfaces under reducing conditions, and it resulted in increased fracture toughness, Young's modulus, and modulus of rigidity. Deoxidation of the system occurred and 0.174 wt% of carbon was found in the sample. This seemed to stabilize the tetragon

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05569.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Several researchers have reported the formation of convoluted, silica‐rich, dispersed‐phase particles during amorphous phase separation in some glass‐forming silicate systems. These appear to be analogous to crystalline growth instabilities such as dendritic, fingered, and cellular structures that can arise during diffusion‐controlled solidification in undercooled

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05570.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The intent of this project was to evaluate any changes in the flexure strength of magnesia‐partially‐stabilized zirconia when aged in distilled water for time periods of 6, 12, and 18 mos. The aging conditions were autoclaved specimens in air (AA) or distilled water (AW) and nonautoclaved specimens in distilled water (NW) at stressing rates of 10.0, 1.0, or 0.1 mm/min. The statistical analysis showed no significant difference between the aging times. The aging‐time data were then pooled and a statistical analysis run between the different aging conditions (AA, AW, and NW) and stressing rates. The specimens tested in air were significantly stronger than those tested in water autoclaved or nonautoclaved. For the pooled data, all stressing rates were statistically significant from each

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05571.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

It is experimentally observed that the peritectic reaction, 211 + liquid → 123, can be driven essentially to completion in 1 h at an undercooling of only ∽30°C. The kinetic data, together with the observed microstructures, are inconsistent with the normal mechanism of the peritectic reaction. It is proposed that the mechanism of the reaction involves dissolution of 211 particles into the liquid and precipitation of solid 123. The aligned grain structure is explained through sympathetic nucleation of new 123 grains on existing gr

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05572.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A line‐focus acoustic microscope and a depth‐sensing nanoindenter have been used to directly measure the elastic moduli of glass‐ceramic thick films on copper and copper/invar/copper substrates. Both techniques proved successful in determining Young's modulus of the films. Measured moduli of the films were close to those of bulk glass‐ceramic values for both techniques. The nanoindenter produced slightly higher values than the acoustic mic

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05573.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Active wustite (FeδO, with a δ value of 0.98) was prepared by keeping normal wustite (δ value of 0.94) in a N2atmosphere at 300°C for 10 min. This reaction is given by (4δ2–3)Feδ1O→(4δ1–3)Feδ2O + (δ2–δ1)Fe3O4where δ1= 0.94 and δ2= 0.98. The equation indicates that the normal wustite undergoes eutectoid decomposition into active wustite and stoichiometric magnetite (Fe3O4). Carbon dioxide (1.013 × 105Pa) was almost completely (100%) decomposed into carbon (zero valence) by the active wustite at the low temperature of 300°C, which was associated with the transformation of the active wustite into the stoichiometric magnetite. The internal pressure of the reaction cell event

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05574.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of surface modification of lead lanthanum Zirconate titanate (PLZT) powder on sintering and transparency were investigated by sintering hydrophobic powders modified with various alcohols. When alcohols with longer chain lengths were used for surface treatment, aggregation forces among the particles were reduced, resulting in dense, highly transparent ceramics.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05575.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY