"Development of interface morphologies in the tert butyl alcohol-water system

L. M FABIETTI; R. K. TRIVEDI

JOURNAL OF CRYSTAL GROWTH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1997 vol. 182 p. 185 - 197

0022-0248

The process of interface pattern formation in a complex crystal structure is examined through directional solidificationexperiments in the tert butyl alcohol (TBA) ~ water system. The transition from a planar interface to cellular and needlemorphologies with increasing velocity is examined. The anisotropic effects in the complex crystal structure have beenshown to exhibit new features that have not been observed previously. The anisotropy effects have been found to precludecell elimination and cell creation by the tip splitting processes, so that the wavelength of the cellular pattern is determinedby the initial wavelength of perturbation on a planar interface. At higher velocities, a cellular structure is found totransform to a needle structure with highly faceted sides which stabilize the interface against sidebranch instability. Thetip region of the needle morphology also exhibits a unique structure that resembles a fingernail, whose formation isgoverned by the anisotropic properties of the advancing interface. In this complex crystal structure, the growing planesare not symmetrical and the growth occurs preferentially only along specific orientations of the advancing interfacewhich give rise to a fingernail morphology. The scaling law for the primary spacing and the variation of interfacetemperature with velocity have been found to show a behavior analogous to that for isotropic materials.