摘要:

The effects of rare‐earth oxide additions on the oxidation of sintered Si3N4were examined. Insignificant oxidation occurred at 700o and 1000oC, with no evidence of phase instability. At 1372oC, the oxidation rate was lowest for Y203 and increased for additions of La2O3, Sm2O3, and CeO2, in that order. Data obtained from X‐ray diffraction, electron microprobe analysis, and scanning electron microscopy indicate that oxidation occurs via diffusion of cationic species from Si3N4grain boundar

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10157.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The transformation of spherical alumina powders precipitated from an aluminum sulfate solution was studied using a combination of X‐ray diffraction and transmission electron microscopy. Particles calcined at 900°C consisted of poly‐crystalline γ‐alumina which transformed to essentially single‐crystal a‐alumina on further

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10158.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Soda‐lime‐silica glass canes were ion‐exchanged in a bent mode in a molten KNO3salt bath. After ion exchange and cooling, the specimens showed asymmetry of residual stresses. Measured penetration profiles of potassium showed that the maximum diffusion occurred from the tension side, the minimum from the compression side, with the neutral side being in between. These observations support the notion that externally applied stresses can alter the average site size for cation diffusion in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10159.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Semiconducting barium titanate elements with positive temperature coefficient of resistance (PTCR) are usually subjected to different degrees of stress levels during processing operations like grinding, ultrasonic drilling, and slicing, etc. In this work we have examined the influence of these operations on the semiconducting properties of PTCR barium titanate using X‐ray diffraction and electrical resistivity measurement

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10160.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Several oxynitride glasses were synthesized with and without the addition of a few weight percent of free silicon. For Mg‐Si‐0‐N and Si‐Al‐0‐N glass compositions, the severe frothing (or “bubbling”) which was observed during melting could be eliminated completely by the addition of silicon. In a Y‐Si‐Al‐0‐N composition, frothing was not observed, even when no silicon was added. The results are used to explain why A1N is superior to Si3N4for synthesizing transpa

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10161.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The surface ‐OH profile in a 15BaF2‐28.3ZnF2‐28.3YbF2‐28.3ThF4(mol%) glass resulting from reaction with atmospheric water for 22.5 h at 344°C was determined by monitoring the 2.9‐pm absorption band as material was removed from the surface by polishing. The ‐OH penetrated ‐10 pm into the surface. The‐OH concentration profile agreed with that predicted from a diffusional analysis, allowing determination of the surface ‐OH concentration; this corresponded to replacement of one of sev

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10162.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Pure hexagonal BaNb2O6crystallizes at 640° to 700°C from an amorphous material prepared by simultaneous hydrolysis of barium and niobium alkoxides. The structure is characterized by layer networks of NbO6octahedra. Crystallization isotherms are described by the Avrami equation In (1—f) = ‐ktnwith n=2; the activation energy is 268 kJ‐mol‐'. Hexagonal BaNb2O6transforms to the ortho‐rhombic modification one at 12.50

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10163.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The interfacial reaction between Y2O3‐partially‐stabilized ZrO2and α‐Al2O3was studied. It was noted that α‐Al2O3forms inside the periphery of the β‐Al2O3grains; its formation suggests the loss of Na2O from the p‐Al2O3, either by evaporation or by dissolution in the ZrO2matrix. The presence of Na2Zr

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10164.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effect of alkali ion identity on the dc electrical conductivity of alkali‐doped Zr‐Ba‐La‐Al fluoride glasses containing 5 mol% MF, where M is Li, K, or Cs, was measured. The electrical conductivity increases in the order Li

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10165.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effect of time and temperature on the density and strength of α‐Sic was studied and mathematically modeled using a central composite experimental design. A sintering temperature of 2150°C for 1.7 h maximized the flexural strength and densification values. However, temperatures above 2200°C promoted abnormal grain growth, with resulting appreciable decreases in strength. Flexural strength increased exponentially with increasing density for specimens with densities<92% of theoret

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb10166.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY