Solidification and thermal behaviour of binary organic eutectic and monotectic; succinonitrile–pyrene system

Abstract

Transparent binary alloy models are important in metallurgical and materials science, as phase transformations can be observed during solidification. This communication concerns the solidification and thermal studies of succinonitrile (SCN)–pyrene (PY) system, which is an organic analogue of a metal–nonmetal-type system. Phase diagram of the SCN–PY system, determined by the thaw-melt method shows the formation of a monotectic and a eutectic at 143.3°C and 55.3°C with 0.025 and 0.744 mole fractions of SCN, respectively. The critical solution temperature of the system lies 48.7°C above the monotectic temperature. The growth velocity ( v) data at different undercoolings obtained from the capillary method, obey the Hillig–Turnbull equation, v= u(Δ T) n . The heats of fusion of the binary as well as single materials were obtained from the DSC (Mettler DSC-4000 system) from which the entropy of fusion, enthalpy of mixing, Jackson's roughness parameter, excess thermodynamic functions, interfacial energy and radius of the critical nucleus were calculated. The optical microphotographs of the eutectic and monotectic show their characteristic features.