Synthesis and characterization of novel binary organic monotectic and eutectic alloys

The phase diagram of biphenyl – 3-hydroxybenzaldehyde (BP–HB) shows the formation of a eutectic with HB-0.935 mole% BP and 4-bromochlorobenzene – m-aminophenol (BCB–AP) show the formation of a monotectic (AP-0.150 mole% BCB) and a eutectic (AP-0.996 mole% BCB). The BCB–AP shows large miscibility gap where the consolute temperature is 12.5 °C above the monotectic horizontal. Growth kinetics of pure components, the eutectics and the monotectic were studied by measuring the rate of movement of the solid–liquid interface which suggests the applicability of Hillig–Turnbullʹs equation. The thermodynamic functions 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 by the DSC method. The relation between interfacial energies of monotectic system satisfies the Cahnʹs wetting condition. The optical microphotograph of monotectic shows lamellar structure whereas eutectics show broken lamellar and lamellar pearlite structures.