摘要:

A steady‐state demixing of initially homogeneous solid solution which occurs in binary oxides under oxygen partial pressure gradient is treated by the path probability method of irreversible statistical mechanics from an atomistic point of view. The larger the difference between the diffusion coefficients of constituent species is, the larger is the degree of demixing. Essential features of demixing by diffusion, however, do not depend on whether the driving force is the chemical potential gradient, the electric field, or other

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15241.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The nomenclature and classification of ferrospinel structures and textures are presented. Conditions for their formation are described. In this respect, the classification suggested may be used both as a basis for closer investigation and as a means of obtaining ferrites with the desired structure.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15250.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Composites of Al2O3and Y2O3partially‐stabilized ZrO2were isostatically hot‐pressed using submicrometer powders as the starting material. The addition of Al2O3resulted in a large increase in bending strength. The average bending strength for a composite containing 20 wt% Al2O3was 2400 MPa, and its fracture toughness was 17 MN·

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15251.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Stoichiometric mullite powder (3Al2O3·2SiO2) prepared by spray pyrolysis and sintered at 1650°C attained 95% of theoretical density. The flexural strength was 360 MPa at room temperature and decreased slightly at 1400°C. A fairly high KIcvalue (2.8 MN/m3/2) was obtained. These mechanical properties can be attributed to the highly homogeneous stoichiometric composition of the raw powd

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15252.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Amorphous red phosphorus formed in reduced phosphate glasses was found to show a photodarkening effect by illuminating the glasses with light approximately equivalent to its absorption edge; the optical transmission edge shifts toward longer wavelengths on illumination, and then a distinct deepening of the reddish color is observable visually. The photo‐darkened specimen recovers its original transmission when it is heated at 300° to 350°C. This darkening‐restoring process is confirmed to be reversible by repeated illumination and heating. Transmission measurements over a range of elevated temperatures suggest that this optical characteristic of red phosphorus is unique to its amorphous

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15242.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The proton free induction decay of a portland cement paste in an advanced stage of hydration can be roughly divided into three main components: (1) a component with a very short spin‐spin relaxation time, T2, representing the protons of the solid OH groups and the water of crystallization, (2) a component with an intermediate T, representing the bonded water in the gel phase, and (3) a third component with a relatively long T2representing the water in the micropores and layers. The dependences of the intensities, T2's, and spin‐lattice relaxation times (T1's) of these three components on the cement hardening time have been determined. The proton spin‐lattice relaxation time of the “solid” component increases with hardening time whereas T1decreases for the other two components. The observed time dependence of the diffusion coefficient, D, of water in a tricalcium silicate paste supports the findings of the above correlat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15243.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Kinetics of precipitation in a binary or a pseudobinary system, where diffusion and interface transfer are comparable, were examined along lines similar to those proposed by Wert and Zener. An equation which explicitly relates annealing time to the fraction transformed is derived. The possibility of change‐over from diffusion to interface control of the kinetics in ceramics through appropriate doping is suggeste

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15254.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Thermal diffusivities of cordierite glass and glass‐ceramics measured by the laser‐flash method using remote optical sensing to monitor the transient temperature of the specimen were higher than those obtained with a thermocouple. The latter data were thought to be lower because of thermal contact resistance, the heat capacity of the cement used to adhere the thermocouple, and heat loss along the thermocouple wire. It is concluded that remote optical sensing yields more reliable d

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15255.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Micrographic evidence is presented suggesting that perturbation phenomena of the type described by Rayleigh and others may play a role in the development of closed pores in powder compacts undergoing densification. Several difficulties in applying the thermodynamic and kinetic analyses based on cylindrical pore geometries are discussed.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15256.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The production of β‐sialon (Si3A1303N5) and nonoxidic powders by carbothermal reduction of oxides is discussed. Special attention is paid to the rate‐determining steps in the conversion process performed in a packed‐bed reactor. It is shown that powders with specific surface area>10 m2/g can be produced by the correct choice of pellet size, gas flow rate, temperature, and raw ma

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1985.tb15244.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY