Papers by Keyword: Solid-Liquid Interface Energy

Abstract: The reduction of size of the low dimensional materials leads to a dramatic increase of surface-to-volume ratio. The properties of a solid are essentially controlled by related surface/interface energies. Although such changes are believed to dominate behaviors of nanoscale structures, little experience or intuition for the expected phenomena, especially the size dependent properties and their practical implications, are modeled. In this contribution, the classic thermodynamics as a powerful traditional theoretical tool is used to model different bulk interface energies and the corresponding size dependences where emphasis on the size dependence of interface energy is given, which is induced by size dependence of coherent energy of atoms within nanocrystals. It is found that solid-vapor interface energy, liquid-vapor interface energy, solid-liquid interface energy, and solid-solid interface energy of nanoparticles and thin films fall as their diameters or thickness decrease to several nanometers while the solid-vapor interface energy ratio between different facets is size-independent and is equal to the corresponding bulk ratio. The predictions of the established analytic models without any free parameter, such as size and temperature dependences of these four kinds of interface energies, are in agreement with the experimental or other theoretical results of different kinds of low dimensional materials with different chemical bond natures.

Abstract: Magnetic field texturing of superconducting oxides has shown the possible existence of intrinsic solid nuclei surviving above the melting temperature Tm and governing the solidification. Tiny crystals could survive above Tm and act as growth nuclei with undercooling ratios θ= (T-Tm)/Tm larger than the theoretical value −2/3 if a negative supplementary volume energy −ε v is added in the Gibbs free energy change associated to the formation of a critical cluster. A double layer of opposite charges could create the solid-liquid interface electrostatic -εv. The observed maximum values θ1 and the dimensionless surface energies α1ls calculated for 38 elements assuming that their melts homogeneous,
 used to determine εv(θ). The εv values at T=Tm were equal to 21.7% of the fusion heat per volume unit. The quantity α2ls 3× Sm was nearly the same for all elements, α2ls being the dimensionless surface energy and Sm the fusion entropy. After melting these tiny crystals around Tm2=1.20Tm, all the undercooling ratios could tend to -2/3. The bidimensional texture of Bi2212, Bi2223 tapes can be induced by these nuclei during crystal growth when the prereacted compounds in the sheath are melted and annealed at a weak overheating temperature smaller than a critical value.