摘要:

Differential scanning calorimetry has been used to study ordering, disordering and recrystallization of cold-rolled Fe‒70 at.% Co in both the initially ordered and the disordered states. The effect of the initial state of order on the transformation temperatures and energies of both reordering and recrystallization decreases as the rolling reduction increases, until after 90% rolling reduction they are almost unaffected by the initial state of order, suggesting that the initially ordered material is almost completely disordered. The results support a hypothesis that gliding antiphase-boundary-coupled superlattice dislocations leave disorder behind them.

ISSN:0950-0839    

DOI:10.1080/09500839308242424

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

X-ray diffraction measurements on a nanocrystalline Pd sample transformedin situto PdH0·56are described. Debye-Waller parameter measurements at several temperatures showed unexpected increases in both thermal and static atomic displacements caused by the hydriding. These increased displacements are associated either with the creation of new point defects on the Pd sublattice or with an increase in the magnitude of the strain fields of previously existing point defects. Substantial X-ray peak broadening due to the production of large numbers of dislocations is seen when coarse-grained Pd is hydrided. In contrast, measurable changes in the peak breadths were not observed for the nanocrystalline sample as a result of hydriding, indicating that dislocations with long-range displacement fields are not created when nanocrystalline Pd is hydrided. A preference to produce or modify short-range defects instead of dislocations during hydriding may occur as a result of the larger stresses required to generate dislocations when the grain size of the material is small.

ISSN:0950-0839    

DOI:10.1080/09500839308242425

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The superconducting transition temperature of then= 2 member of the homologous series HgBa2Can-1CunO2n + 2 + δwith two CuO2layers per unit cell has been measured under quasi-hydrostatic pressures up to about 18·5 GPa. Superconductivity up to 147 K has been detected with a main transition at 138K at 18·5 GPa without saturation. This represents the highest superconducting transition temperature ever reported in a cuprate compound with two CuO2layers. It is expected that superconductivity at temperatures higher than 147 K can be achieved in this compound either under higher pressures or by chemical substitution at ambient pressure.

ISSN:0950-0839    

DOI:10.1080/09500839308242426

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This letter contributes to the study of processes taking part during the formation of porous silicon. Elementary analysis has revealed a possible connection between intrinsic sound waves in the basal material, surface chemical reactions and the forms of porous silicon.

ISSN:0950-0839    

DOI:10.1080/09500839308242427

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Ornstein-Zernike equations for the structure of a fluid of positive ions in equilibrium with a disordered matrix formed by chlorine ions are solved numerically in the hypernetted-chain approximation, and the results are compared with those obtained for the corresponding molten salt at complete equilibrium. Quenching of the halogen framework in a model appropriate to CuCl enhances the delocalization of the Cu ions. A similar, although less striking, reduction in the short-range order of the metal-ion component is accompanied by an enhancement of its state of intermediate-range order in models appropriate to trivalent metal halides with octahedral- or tetrahedral-type coordination.

ISSN:0950-0839    

DOI:10.1080/09500839308242428

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The recently established linear growth law for three-dimensional diffusive coarsening shows zero average growth for grains with 15·8 faces, while the average number of faces per grain in the pattern is 13·7 ± 0·1. In the better-known two-dimensional case, grains with six sides (the average number) show zero growth. We show that the three-dimensional zero growth value is a consequence only of the linear form of the law and the cubic dependence of average area per grain on the number of faces.

ISSN:0950-0839    

DOI:10.1080/09500839308242429

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor