Sidebranch characteristics of pivalic acid dendrites grown under convection-free and diffuso-convective conditions

This work investigates the sidebranch characteristics of pivalic acid dendrites grown under convection-free (cf) and diffuso-convective (dc) conditions for supercoolings over the range of 0.1-1.0 K. Results indicate that the distance from the dendrite tip to the first detectable sidebranch and to the first detectable coarsening event normalized by the tip radius, R, are independent of the supercooling. The sidebranch spacing in the uniform region near the dendrite tip, and the spacing in the coarsening region when normalized by R, do not appear to have a significant dependence on convection or supercooling. When the envelope enclosing all sidebranches from the tip to the end of the coarsening region was fitted to a power law as a function of distance from the tip, we found that the pre-exponential and exponential terms were significantly different for the convection-free and diffuso-convective results. This supports the observation that the absence of convection seems to alter the size of the sidebranches. Lastly, the predictions from theoretical models of sidebranch spacings are much lower than experimental observations, while the predicted sidebranch amplitudes were larger than those observed.