Shape of ammonium chloride dendrite tips at small supersaturation

TL;DR

This study measures the tip shapes of ammonium chloride dendrites grown at small supersaturation, comparing models to find the best fit and analyzing deviations from theoretical predictions.

Contribution

It provides detailed shape measurements and evaluates the effectiveness of parabolic and power law models for dendrite tip shapes at small supersaturation.

Findings

Fourth-order fit best describes the tip shape.

Fourth-order coefficient is about half the theoretical value.

Neither model perfectly fits the data.

Abstract

We report detailed shape measurements of the tips of three-dimensional ammonium chloride dendrites grown from supersaturated aqueous solution. For growth at small supersaturation, we compare two different models: parabolic with a fourth-order correction, and power law. Neither is ideal, but the fourth-order fit appears to provide the most robust description of both the tip shape and position for this material. For that fit, the magnitude of the fourth-order coefficient is about half of the theoretically expected value.