Filamentary Crystals grown from the Solid Metal

Abstract

A theoretical analysis and experimental evidence show that a source of energy for spontaneous whisker growth is the elastic strain energy arising from the anisotropy of thermal expansion. Observation of whisker growth on a Bragg bubble raft suggests that the growth mechanism could be by cooperative repetitive movement of dislocations. The conditions for whisker growth from the solid are presented and by fulfilling them growths were produced on gold, silver, bismuth, lead, indium, and lead-indium alloys. The crystallographic orientations of a number of tin whiskers are reported, one of which had a transition between two orientations although it was straight. The tensile strengths of several tin whiskers were measured and observed to be lower than calculated from bending tests. The high elastic strain of 5% in bending was observed for an indium one.