银钯复合微纳米晶的可控制备及其结构稳定性的微观机理

Due to the composite effect among the compositions, the precious metal materials' performances get significant improvement, but the lack of knowledge for the growth mechanism of the binary alloys or core-shells composited structures, and the inherent law of the composited structure stability have been the main obstacles to enhance the property and enlarge application for two-component noble metal systems. This project will firstly aim at some important scientific problems to study, for example, the effective preparation for the precious metal composite powders; further, we will focus on resolving its performance requirements in the field of electronic information. by choosing a variety of preparation method to continuously control the compositions or sizes, and find the physical and chemical laws during binary metal nucleation and growth in solution; and then the composite structure are treated in a different atmosphere with heating to achieve adjustable evolution of interface structure and the changes of the composite' microstructures; by the microstructure characterization combined with the analysis of the thermal stability and the silver migration behavior, we will obtain the relationship laws between microstructure and stability of the system. At the same time, the project will reveal the microstructure evolution process and mechanism of silver-based composite structures at the atomic and electronic level by combining the experiment with theoretical calculation. The implementation of the project will bring important theoretical and practical value to explore the facile preparation for other noble metal micro/nanocrystals and also efficiently, scientifically design other composite materials.

材料的复合效应成功地实现了贵金属性能的明显改善，而对二元合金与核壳复合结构的液相生长机理认识不足及微组织结构稳定性规律探索的有限性，一直是制约双组分贵金属体系推广应用的主要障碍。本项目瞄准当前贵金属复合粉体的科学、高效制备所面临的重要科学问题，以其在电子信息领域应用中所面临的性能要求为导向，拟通过选取多种液相制备方法和手段，可控制备组分或尺寸连续可调的银钯复合微纳米晶并寻找存在于液相中的二元金属成核生长的物理化学规律；进而通过在不同气氛中对复合结构进行热处理，实现界面结构演化与体系微结构的可调变化；通过微结构的表征分析，结合复合体系热稳定性与银迁移特性的评估，获得晶体微结构与稳定性的关系规律；项目同时拟通过实验表征与理论计算相结合的方式，从原子与电子层次上揭示银基复合结构中微结构演化过程与机理。项目实施对于高效、科学的设计和制备其它贵金属复合微纳米粉体提供理论和实验指导。

银钯的复合可成功地实现银电极性能的明显改善，而对银钯合金与核壳复合结构的液相生长机理认识不足及微组织结构稳定性规律探索的有限性，一直是制约双组分贵金属体系推广应用的主要障碍。本项目根据氧化还原电位理论和规律，通过液相化学方法成功实现了球形、片状、枝状等不同形态、不同尺寸和不同组分的的银钯复合粉，并采用了水热法和固相法两种不同的手段对获得的银钯复合结构进行了热稳定性和抗银迁移能特性研究，最后通过第一原理分子动力学理论计算，从原子与电子层次上揭示银基复合结构的热稳定性机理。.研究发现,通过调整银钯前驱体电极电位和还原剂种类，可实现银钯合金与核壳结构的选择性合成，相同条件下钯含量越高，越易于形成核壳结构，而温度越高，获得的银钯颗粒尺寸越小；核壳结构银钯粉也可以通过后续水热液相或固相热处理而朝着合金化的方向转变；对于不同结构的银钯粉，核壳结构银钯粉的抗银迁移能力最强，混合粉最差，而环境中电解质的存在对银迁移的影响非常大；理论计算发现银钯共晶温度随着粒径减小或尺寸增加而下降，其中尺寸效应是主要因素，而维数效应是次要的。.项目研究成果为高可靠厚膜电极材料制备和片式共烧元器件用银钯电极的性能优化提供重要保证。鉴于银钯核壳结构的优异性能，其二维核壳结构有可能作为高可靠柔性光电子器件用电极材料而值得进一步研究。