Double dendrite growth in solidification

Abstract

We present experiments on the doublon growth morphology in directional solidification. Samples used are succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as the solute. Doublons, or symmetry-broken dendrites, are generic diffusion-limited growth structures expected at large undercooling and low anisotropy. Low anisotropy growth is achieved by selecting a grain near the {111} plane leading to either seaweed (dense branching morphology) or doublon growth depending on experimental parameters. We find selection of doublons to be strongly dependent on solute concentration and sample orientation. Doublons are selected at low concentrations (low solutal undercooling) in contrast to the prediction of doublons at large thermal undercooling in pure materials. Doublons also exhibit preferred growth directions and changing the orientation of a specific doublonic grain changes the character and stability of the doublons. We observe transitions between seaweed and doublon growth with changes in concentration and sample orientation.

Insights into Polymer Crystallization from Phase-Field Theory

“…The orientational dependence of the free energy of the solid-liquid interface has been established experimentally and theoretically as a primary parameter governing nonequilibrium crystal growth (Kurz and Fisher 1990;Glicksman and Marsh 1993;Billia and Trivedi 1993). For moderate undercooling, low g, and modest fluid viscosities, the tips of the crystal trunks tend to split regularly in the center, corresponding to the "doublonic" growth mode (Utter and Bodenschatz 2005). This leads to a somewhat disordered crystallization morphology that has some resemblance to naturally occurring seaweed.…”

“…The following image shows that polymer dendrites have long been observed on surfaces of polymer solutions. (d) Ni/Cu dendrite grown within the phase-field theory using a sixfold symmetry (k ¼ 6) of the interface free energy anisotropy Encyclopedia of Polymers and Composites DOI 10.1007/978-3-642-37179-0_30-1 # Springer-Verlag Berlin Heidelberg 2013 studied by Bodenschatz and coworkers (Utter and Bodenschatz 2005;Utter et al 2001). In the blends of mass ration 40/60-30/70, well-formed symmetric dendrites are observed, in which the fourfold symmetry of equilibrium PEO crystallization asserts itself at a macroscopic scale ( Fig.…”

Synthesis of Silicon Carbide Dendrite by the Arc Plasma Process and Observation of Nanorod Bundles in the Dendrite Arm

“…Accumulation of solute and heat at the interface sometimes produces super cooling, which introduces instability in the interface at all points, thus producing a tree‐like structure, called “ dendrite ,” in the resulting solid. It is now known that surface tension isotropy and anisotropy of the liquid melt, diffusion, super cooling, etc., play significant roles in deciding dense branching morphology or seaweed growth 27 . Super cooling can be constitutional super cooling or simple thermal super cooling 28 .…”

“…It is now known that surface tension isotropy and anisotropy of the liquid melt, diffusion, super cooling, etc., play significant roles in deciding dense branching morphology or seaweed growth. 27 Super cooling can be constitutional super cooling or simple thermal super cooling. 28 In the literature of carbothermic synthesis carried out in electric arc and thermal plasma, one finds that Si(l) participation in SiC growth has been highlighted by several workers.…”

Anomalous α-Mg Dendrite Growth During Directional Solidification of a Mg-Zn Alloy

“…The seaweed structure seems to grow with an angle of~40 deg to the trunk initially, but then bends to a larger angle (~60 deg). Prior studies have observed seaweed-like structures during solidification either at near-isothermal conditions [24][25][26][27] or in deeply undercooled metallic melts. [28][29][30] Textured seaweed structures were also observed by Rappaz et al [8][9][10]19] in aluminum alloys when zinc was added at compositions of 25 to 55 wt pct.…”