Growth Mechanism of Helicoidal Nickel Whiskers

NICKEL whiskers obtained by reduction of the
iodide of the metal can be classified into two
categories :
(i) rectilinear whiskers
(ii) helicoidal whiskers

In general, these whiskers are formed by a stacking
of small idiomorphic crystals. The law governing such
stackings was determined theoretically in a previous
investigation .1,2 It was shown that they were formed
from nickel iodide in fusion and that the theory of
dendritic growth was quite true for rectilinear
whiskers ; the axes of growth are of low indices
( <111->, ---100> ) and the conditions required for
dendritic growth as described by Papapetrou3 are
fulfilled.
Rectilinear whiskers without branches are obtained,
because one of the directions of dendritic growth is
favoured and the development takes place only in that
direction.
This paper presents a study of the growth mechanisms
of helicoidal whiskers.