复合法制备多晶金属表面Ti-Si-C MAX相涂层及其形成机理和性能研究

In this project, a combined method ( magnetron sputtering/post annealing) is adopted to form Ti-Si-C MAX phase (Tin+1SiCn) coatings on polycrystalline metal substrates, i.e., first, TiCx/Si nano-structured multilayer coatings are deposited on polycrystalline metal substrates by a magnetron sputtering technique and then the multilayer coatings are post-annealed to produce continuous Tin+1SiCn coatings by the mechanism of the intercalation of Si into TiCx crystalline. To further understand the synthesis mechanism of Ti-Si-C MAX phase coating, the effects of extent of crystalline distortion in TiCx and degree of Si saturation adjacent to TiCx on the Si diffusion path, diffusion rate and critical temperature will be explored and the results will reveal the formation mechanism of Tin+1SiCn compounds with various n values. The properties of synthesized MAX phase coatings are studied under the simulated proton exchange membrane fuel cells (PEMFCs) bipolar plates conditions and the feasibility of the Tin+1SiCn material using as bipolar plate coatings is discussed.The objective of this project is to find a viable method to deposit Tin+1SiCn MAX phase coating on polycrystalline metal substrates to solve the problem that Tin+1SiCn is difficult to grow on polycrystalline metal substrates by physical vapor deposition techniques. It will have great scientific significance in better understanding of the properties and formation mechnism of Tin+1SiCn MAX phase coatings.

本项目采用磁控溅射-涂层热处理复合方法在多晶金属基体表面制备Ti-Si-C MAX相（Tin+1SiCn）涂层，即先采用磁控溅射方法在多晶金属表面制备TiCx/Si纳米多层结构涂层，再对涂层进行热处理，应用Si扩散进入相邻TiCx晶格形成晶内插层的机理，合成连续Tin+1SiCn涂层。深化研究涂层生成机理，探索TiCx晶格畸变程度和TiCx周围Si饱和度对Si的扩散路径、扩散速度、扩散要求的最低温度的影响规律，揭示具有不同n值的Tin+1SiCn化合物的生成机理。并对生成的多晶MAX相涂层在模拟质子交换膜燃料电池金属双极板应用条件下的性能进行研究，探讨其应用于金属双极板的可行性。该项目旨在解决物理气相沉积Tin+1SiCn涂层难以在多晶金属表面生长的问题，为Ti-Si-C MAX相涂层的合成提供新方法，对进一步理解Tin+1SiCn的形成机理，了解多晶MAX相涂层的性能具有重要的科学意义。

本课题研究采用等离子辅助磁控溅射技术和热处理二步复合方法在不锈钢基体表面制备Ti-Si-C MAX相涂层，并对其在模拟质子交换膜燃料电池双电极板应用条件下的性能进行研究。通过本课题的研究，掌握涂层制备参数与涂层结构和性能之间的规律，揭示Ti-Si-C MAX相涂层生成机理。实验结果表明，采用磁控溅射制备的TiCx/Si 纳米多层结构涂层，当其单个周期层厚度到5 nm时，Si层在热处理条件下，进入TiCx晶格中，并形成Si晶内层，从而生成Ti-Si-C MAX相涂层。而Si进入晶格的程度与TiCx内的晶格畸变和缺陷有关。该Ti-Si-C涂层的接触电阻与不锈钢相当，但是在阴极电极板应用条件下的耐腐蚀性能要好于不锈钢材料。因此该成果为Ti-Si-C MAX相涂层的制备提供了新方法，为PEM燃料电池金属双极板提供了新型的保护涂层材料。