基于热力学与动力学关联建立非晶成分设计热力学指导的研究

It has been a challenge in the community of amorphous materials to find out a strategy to guide the composition design for glass formation. The solution to the problem is also important to understand the glass transition in materials. Fortunately, a number of experimental evidences are displaying the strong correlations between the entropy of fusion with the formation and kinetics of glassy materials. In particular, our recent studies revealed the relation of the entropy of fusion in metallic and molecular glassformers and their melt viscosity at melting points. This suggests a promising fashion to understand the glass formation from the perspective of the entropy of fusion, probably offering a new key to the composition design of glasses. However, it needs to be noticed that experimental and theoretical interpretations of the relationship between the entropy of fusion and glass formation have been controversial for decades. The solution to it asks for extensive and intensive studies to clarify the specific contribution of the entropy of fusion to glass formation. In this context, the present project plans to carry out a series of studies started by establishing the thermodynamic and kinetic correlations in amorphous materials. The significance of the entropy of fusion for the glass formation in various materials will be evaluated. The basic characters of the entropy of fusion in various materials will be identified, and the relation of the entropy of fusion to the thermodynamic and kinetic behaviors of materials is explored. A strategy for guiding the composition design of glass formation will be proposed based on the data of the entropy of fusion. The idea in this project is quite different from the conventional practice in search of glass composition imposed by the deep eutectics in phase diagrams. An effective guidance for the composition design is expected to be formulated by referring to the entropy of fusion, with which the glass formation thermodynamics will be developed from conventionally qualitative accounts to quantitative guidance.

寻找实用的非晶成分设计指导原则是非晶金属合金研究领域一直探索的基本问题，也是理解非晶转变的关键。不断增加的实验证据表明，材料熔化熵与其非晶形成以及非晶动力学密切相关，尤其是最近本课题组建立了熔化熵与材料熔点粘度的关联。这意味着从材料熔化熵角度理解非晶形成具有可行性，也为寻找非晶成分设计方法打开了一扇门。然而，就熔化熵与非晶形成的关系而言，目前实验与理论观点相矛盾。为了澄清这一问题，同时深化对非晶形成热力学的理解，有必要围绕熔化熵开展深入研究。为此，本项目计划从非晶材料热力学与动力学关联入手，全面探索熔化熵在多种材料非晶形成中的作用与贡献，理解熔化熵与材料基本行为的关系，建立应用熔化熵指导非晶成分设计途径。这一研究思路突破以往依靠相图寻找共晶点指导非晶成分设计的局限性，使非晶形成组分选择更具针对性，也为理解和评估不同材料体系的非晶形成提供一个有力的参考和依据。

通过从非晶材料热力学与动力学关联入手，全面探索了熔化熵在多种材料非晶形成中的作用与贡献，理解了熔化熵与材料基本行为的关系，建立了应用熔化熵指导非晶成分设计途径。熔化熵与非晶形成和动力学特征有着强烈的关联，这是从一种全新的角度理解了非晶形成的机理。从本质上来讲，非晶形成最直接相关的热力学参量是吉布斯自由能，低的固液吉布斯自由能之差会降低结晶的驱动力从而提高非晶的玻璃形成能力。然而该值无法通过实验直接进行测量，限制了其在非晶形成及成分设计上的实际应用。通过熔化熵来评估了共晶玻璃、金属间化合物及它们临近成分的玻璃形成能力及晶化动力学，结果表明低的熔化熵对应着高的玻璃形成能力，慢的动力学行为和高的热稳定性。在一些金属间化合物和共晶玻璃中，偏共晶成分有着最好的玻璃形成能力和最低的熔化熵。基于低熔化熵原则，我们设计的玻璃形成体系的组分和文献报道的最佳组分相近，这无疑大大的提高了寻找最佳非晶成分点的效率。突破了以往依靠相图寻找共晶点指导非晶成分设计的局限性，使非晶形成组分选择更具针对性，也为理解和评估不同材料体系的非晶形成提供一个有力的参考和依据。