Measurement of the Capillary Length for the Dendritic Growth of Ammonium Chloride

TL;DR

This paper introduces a novel method to measure the capillary length in dendritic crystal growth, specifically applied to ammonium chloride, reducing previous measurement discrepancies and providing more accurate data.

Contribution

A new measurement technique for capillary length in dendritic growth using a spherical crystal in an oscillating temperature field is proposed and validated.

Findings

Capillary length estimates varied over a factor of 20 in prior studies.

The new method yields a product of diffusion constant and capillary length as 0.78 ± 0.07 μm³/s.

Results are consistent with measurements for ammonium bromide crystals.

Abstract

We report the results of a new method of measuring the capillary length for the dendritic crystal growth of non-faceted materials. This method uses a nearly spherical crystal held near unstable equilibrium in an oscillating temperature field. For the growth of ammonium chloride crystals from aqueous solution, previous published estimates of the capillary length varied by over a factor of 20. With this new method, we find the product of the diffusion constant and capillary length $D d_0$ to be $0.78 \pm 0.07 \,\mathrm{\mu m^3/s}$, similar to that obtained for ammonium bromide crystals.