ISSN:0232-1300    

DOI:10.1002/crat.2170170917

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170918

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170919

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170920

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170921

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170170922

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe paper deals 1) with the regularities of the formation of (N+ 1)‐atomic clusters during the growth ofN‐atomic one‐, two‐, and three‐dimensional crystals and 2) with the distribution with respect to stability of the (N+ 1)‐atomic clusters. TheN‐atomic crystals have the structure of a hypothetical metal with a simple cubic lattice and a small number of one‐electron atoms. The binding energy (BE) of the clusters calculated by the Hückel molecular orbital method was assumed to be a measure of their stability. Interactions between nearest‐neighbours only were taken into account.The most stable (N+ 1)‐atomic cluster formed from a one‐dimensional crystal is that in which theN+ 1‐st atom is bonded to the end atom of theN‐atomic one‐dimensional crystal.For two‐dimensional crystals, theN+ 1st atom forms the strongest bond with an atom from the diagonal of the square.With three‐dimensional crystals, theN+ 1st atom is most strongly bonded to a corner atom of the small crystal.The inhomogeneity in the bond energy of theN+ 1st atom to a surface atom of the smallN‐atomic crystal decreases with increasingN.According to earlier studies of ours, the BE per atom increases, whereas the mean energy of a nearest‐neigh

ISSN:0232-1300    

DOI:10.1002/crat.2170170902

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractExperimental results are presented and conceptions are developed for the qualitative understanding of the fast densification which is frequently observed in the shrinkage stage during the sintering of disperse one‐component compacts. They are based on a dislocation multiplication in the powder particle contact regions which is temporarily connected with the contact growth. Thus, a defect structure state is developed due to which it seems possible that the powder particles as a whole move into the pore space through alternating sliding and deformation processes and get densely packe

ISSN:0232-1300    

DOI:10.1002/crat.2170170903

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractBy transmission electron microscopy (TEM), the structural state of a Ti–Al alloy subjected to low temperature thermocycling from 300 to 77 K has been investigated. As the result of this observation, helical dislocations were revealed with the density 109cm−3. These were generated mainly by grain boundaries or subboundaries. Their formation is thought to be associated with thermomechanical stresses arising during thermocycling. Thermomechanical stresses at the interface of neighbouring grains, estimated with making allowance for the anisotropy of the linear expansion coefficient, appeared to be about 7 kg/mm2. It is assumed that helical dislocation formation is one of the ways in which local internal stresses are relie

ISSN:0232-1300    

DOI:10.1002/crat.2170170904

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractGrowth structuress on prism surfaces of synthetic quartz grown by hydrothermal crystallization technique, indicative of microtwinning in them are described, illustrated and discussed. The microtwins are revealed by the misorientation of the growth structures, and it is observed that microtwinning is manifested in different forms. Twinned domains appear in the form of strictly oriented, square striated (stepped) structures with inclined surfaces, seemingly overlapping square striated structures, square and irregular regions demarcated by black line‐like boundaries, patch‐like structures enveloping irregularily bound domains, tongue‐like terraces bordered by irregular line of discontinuity of varying height and the regions with both differently shaped as differently oriented growth structures. From the orientations of the square shaped growth structures, it is shown that crystals consist of domains which are in twin relationship to the main crystal. Twins by rotation around an axis perpendicular to (10ī0) with rotation angles of 60°, 90°, and 180° have been observed. Critical examination of some twin boundaries delineated by black line‐like matter, with the application of multiple beam interferometry and FECO reveal that the black boundary is a ridge (line‐elevation). The line elevation along such a twin boundary is explained to be as a result of preferential adsorption of impurity atoms along the trace of the boundary. It is further observed that discontinuity in crystalline structure along the twin boundary leads to growth forms with distorted morphology thus establishing strong dependence of growth forms on the underlying crystalline structure. Causes for generation of the microtwins (twinning on a microscale) in synthetic quartz

ISSN:0232-1300    

DOI:10.1002/crat.2170170905

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY