Studies On The Relationship Between Glass Formation Kinetics And Thermodynamics And Its Applications

Glassy materials have an important role in industrial production and daily life,but the understanding of the nature of glass materials and glass transition is very limited.It is of great significance to clarify the role of thermodynamics and kinetics in glass transition or glass formation as well as the relationship between them,so as to understand the nature of glass state and to guide the design of glassy materials.In this work,firstly we studied the glass transition behaviors of chalcogenide Ge₂₂Se₇₈ and a variety of glass forming systems by using enthalpy relaxation method,and the key kinetic parameters in the glass transition process were clarified.The structure of the material was analyzed by combining the X-ray diffraction,Raman spectroscopy,liquid fragility m-index and the non-exponential parameter?_KWW.It was revealed that the structure of Ge₂₂Se₇₈ is the coexistence of GeSe₄ tetrahedrons and?Se?n chain basic structural unit.Meanwhile,the enthalpy relaxation behaviors of different glass forming systems were compared,and the relationship between m value and enthalpy relaxation spectrum was established,indicating that the smaller the m value,the stronger symmetry of the relaxation spectrum.Then,in order to clarify the role of thermodynamics and kinetics in glass formation,the glass transition of ionic compound sodium metaphosphate?NaPO3?and various glass forming systems was studied.The glass forming ability of materials was comprehensively discussed in terms of the kinetic melting viscosity??_m?and thermodynamic entropy of fusion?S_m.A close correlation between?_m and?S_m/beads was established when compared with various glass formers,and a critical melting viscosity??_m⁰.01 Pa-s?is denoting the breakage of thermo-kinetic correlation.In addition,we studied the glass transition characteristics of various glass formers,the melting characteristics of pure metals and metal halides,and have a deeper understanding of the key kinetic parameters m as well as the melting entropy?S_m in glass transition.These researches further expand the relationship between glass transition thermodynamics and kinetics.The melting entropies of different systems were studied,and their respective configuration entropy S_conf and excess vibration entropy?S_vib-ex were analyzed,revealing the proportion of vibration entropy in melting entropy?S_vib-ex/?S_m was closely related to the value of m,and the strong liquids of low m generally have relatively low values of?S_vib-ex/?S_m.The parameters of volumetric thermal expansion coefficient?_T,isothermal bulk modulus of a crystal K_T,and melting volume?V_m,were proven to be the key parameters in determining fragility m-index.In addition,when the relationship between ionicity and melting entropy is studied,it was found that there is a clear correlation between?S_vib-ex/?S_m and ionicity f_i,and the?S_vib-ex/?S_m generally increases with ionicity among ionic and oxide compounds.Finally,based on the guidance of low entropy of fusion and high melting viscosity are favorable for glass formatio,a new tellurium-based glassy material was designed and synthesized,which further verified the validity of the study on the thermodynamics and kinetics of glass transition in this paper.