Thermal, solid-liquid equilibrium, crystallization, and microstructural studies of organic monotectic alloy: 4,4'-Dibromobiphenyl-succinonitrile

The phase equilibrium data on an organic analogue of a metal-nonmetal system involving succinonitrile-4,4'-dibromobiphenyl shows two immiscible liquid phases are in equilibrium with a single liquid phase. The phase diagram study infers the formation of a eutectic and a monotectic with a large miscibility gap containing 0.9997 and 0.15 mole fractions of succinonitrile, respectively. The consolute temperature being 67.0 oC above the monotectic horizontal. The thermal study such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated from the enthalpy of fusion values, determined using differential scanning calorimeter (DSC) method. The effects of solid-liquid interfacial energy on morphological change of monotectic have also been discussed. The microstructures of monotectic, eutectic and pure components show their peculiar characteristic features.