Accession Number : AD0803783

Title :   ACICULAR CRYSTALS.

Descriptive Note : Edited translation,

Corporate Author : FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH

Personal Author(s) : Hartmann, Ervin ; Jeszenszky, Bela

Report Date : 21 NOV 1966

Pagination or Media Count : 31

Abstract : The study of whiskers is not yet a completed discipline. Some areas such as the electrical and optical properties of acicular crystals have hardly been studied. It is an accepted theory that most whiskers grow by screw dislocation. On the other hand, it is shown that if there is an axial screw dislocation in the acicular crystal the crystal lattice must be twisted. The twist was demonstrated in a few cases, but it is not clear, nor is the question of where they grow. When the first high strength values were measured, it was assumed that acicular crystals have an ideal structure without dislocation which no multiplication mechanism could develop. Studies of dislocation structures of whiskers indicate that this assumption is correct. Price's studies show that a perfect surface also contributes to high strength values of some whiskers because surface defects promote plastic deformation. The surface can be expected to have an important role because the surface/volume ratio is much higher than that of common crystals. Perfect acicular crystals give an opportunity for studying the ideal crystal lattice. But the immediate technical application of acicular crystals would be evident. The small size, however, hinders this. Hopefully the advancement of growing methods will facilitate the production of larger acicular crystals. At the beginning the average length of whiskers was a few millimeters; today 20 cm acicular crystals can be grown from some materials. There have been attempts to use short whiskers after thickening them by various methods. (Author)

Descriptors :   (*WHISKERS(CRYSTALS), CRYSTAL GROWTH), MECHANICAL PROPERTIES, ELASTIC PROPERTIES, PHYSICAL PROPERTIES, CRYSTAL STRUCTURE, CRYSTAL LATTICES, DEFORMATION, CRYSTAL DEFECTS.

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE