Studies On Thermodynamics And Glass Transition Behaviors In Binary Molecular Eutectic Systems

In previous studies,there were many studies on thermodynamics and glass forming ability(GFA).and also presents many criteria for measuring the GFA of a substance,such as Gibbs free energy AG,melting entropy ?Sm,and heat of mixing ?Hix and so on.The results of thermodynamics and GFA studies have shown that the effect of melting entropy on the GFA to a system is very important,and the low melting entropy is more conducive to the formation of amorphous,but the previous research is more on pure substances,so there is little research on eutectic systems.For binary or multicomponent systems,the heat of mixing is related to the intermolecular interactions within the system and is therefore a significant parameter.So if present a certain correlation between thermodynamic parameters mentioned above(heat of mixing AHmix and melting entropy ASm)and if it also affect the eutectic system's GFA?This article mainly selects the simple binary eutectic system as the research object,and then studies the relationship between the thermodynamic parameters of the eutectic system at the eutectic point and the glass forming ability.We mainly chose two molecule eutectic systems are BZL(benzil)-MNA(metanitroaniline)and BZL(benzil)-MDHB(m-dihydroxybenzene)that present different mixing modes,namely positive and negative heat of mixing respectively,then obtain the eutectic components of the two systems by constructing phase diagrams to research the effects of heat of mixing on melting entropy change at eutectic components,respectively.We show the change in melting entropy at the eutectic point by the excess melting entropy ?Sm-exc(??Sm-?Smave=?Sm-(X?SmA+xB?SmB),the results shown that the excess melting entropy at the eutectic point is positive for the system with positive heat of mixing,whereas the excess melting entropy at the eutectic point is negative when system with negative heat of mixing,so the mixed mode of the mixed system can also be reflected by the positive and negative values of the melting entropy of the eutectic system at the eutectic point relative to the average melting entropy.This paper also describes the simple binary eutectic system of metal,and the mixing mode and the excess melting entropy at the eutectic point were studied.It was found that the excess melting entropy for the positive heat of mixing system is on the curve of the ideal mixing entropy,but it does not exceed the curve,and the systems with negative heat of mixing are located below the curve.After clarifying the correlation between the heat of fusion and the entropy of entropy of the eutectic system at the eutectic point,we investigated the glass forming ability of the two systems at the eutectic composition by low-temperature DSC.The results show that the simple binary eutectic system BZL-MDHB with negative excess melting entropy and heat of mixing has a strong ability to form amorphous alloys,and the results have important guiding significance for designing systems with strong amorphous forming ability.