Crystal growth branching

Dendrite - A tree-like crystalline pattern often observed, for example, in ice crystals and alloys in which the crystal growth branches repeatedly. 

Cardew, P. T. and Davey, R. (1982). Tailoring of Crystal Growth. Institute of Chemical Engineers, North Western Branch, Symposium Papers, Number 2 (ISBN 090663623X). pp. 1.1-1.8. [44]... 

Figure 6. Schematic representation of molecular deposition on the crystal growth face (a, d), the NIF form (b, e), and the F2 form (c, f) for a linear alkane (a—c) and the branched alkane Cg6Hig3CH(CH3)C94Hi89 (d—f). (From 59 with permission of American Chemical Society).

From the observations on branched PEO and alkanes more general conclusions can be drawn about the overcrowding problem at the crystalline—amorphous interface in polymers and about the mechanism of chain deposition during crystal growth. Thus, e.g., although for the Y-shaped alkane the energeti-... 

Chord length measurement is not ideal for these sort of branched crystal growth... 

Precise studies of the structural imperfections in copper single crystals were carried out by F. W. Young, Jr. after he received the Ph.D. degree and joined the Solid State Branch of ORNL. Young developed etchants that brought out the dislocations which intersected the surface. He was thus able to determine the number of imperfections that was present as a consequence of the single crystal growth process and to determine those that were introduced by various mechanical treatments. 

This form of crystal growth differs from that of dendrites in that (a) it tends to have a still larger ratio between the longitudinal and the lateral dimensions with an almost perfect preservation of the latter during growth, and (b) it exhibits no tendency to side branching. Impurities or additives in the electrolyte seem to be a prerequisite for its appearance [11, 119]. 

Measurement of relative crystallinity 0 as a function of time, t, can be very simple, and the results are informative. However, some limitation for applying the Avrami equation must be taken into account. The volume is not constant during crystallization, the crystal growth rate may not be constant, the nucleation may vary with time, and the crystal lamellae branching and perfection process may occur over the course of crystallization. 

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