SiCw-ZrB2-ZrC复相陶瓷中原位生长SiC晶须的尺度效应及其强韧化机制

In order to solve the problems of introduction and dispersion uniformity of SiC whiskers in ZrB2-ZrC ceramics, this project provides a rapid and low-cost method of in-situ growth of SiC whiskers strengthen ZrB2-ZrC ceramic composites with precursor conversion method combined with hot-press process, in which the SiC whiskers and ZrB2-ZrC ceramic matrix are in-situ grown simultaneously. The in-situ growth rule and mechanism will be revealed by investigating the influencing factors and mechanism of the growth of SiC whiskers during pyrolysis process of the precursor. Microstructure evaluation of the interface will be revealed based on comprehensively study of the interfacial state of the SiC whisker and ZrB2-ZrC ceramic matrix. The mechanical properties of the composites will be evaluated. The interfacial bonding mechanism, as well as the strengthening and toughening mechanism will be revealed. The effect of the SiC whisker size changes on the microstructure and mechanical properties of the composites will be explored. The relationship between the size of SiC reinforcement and interfacial state as well as the strengthening and toughening effect will be established. The preparation technology of SiC whiskers strengthen ZrB2-ZrC ceramic composites with good interface bonding and excellent toughening effect will be revealed. The rapid and low-cost method of SiC whiskers strengthen ceramic matrix composites will be established. This project will provide theoretical and technical guidance for the structure design and application of all kinds of multiple phase ceramic composites.

为解决晶须增强陶瓷基复合材料制备过程中SiC晶须的引入及分散均匀性问题，实现晶须的原位生长及高性能复相陶瓷的快速、低成本制备，本项目提出采用晶须与陶瓷基体同步原位生长的前驱体转化技术结合热压工艺制备SiC晶须增强ZrB2-ZrC陶瓷的新方法。研究前驱体转化过程中影响SiC晶须生长的因素及作用机理，揭示SiC晶须的生长规律及原位生长机理；研究热压过程中晶须与基体间界面的演变行为，揭示界面结合机制；表征复合材料的力学性能，评价原位晶须的强韧化效果，阐明强韧化机制；研究SiC晶须尺度变化对界面结构及强韧化效果的影响规律，阐明SiC晶须的尺度效应，建立增强体尺度-界面结合-强韧化效果之间的关联；阐明界面结合良好、力学性能优异的SiC晶须增强ZrB2-ZrC陶瓷的制备工艺，从而确立面向各类SiC晶须增强陶瓷基复合材料的快速、低成本制备方法，为各类复相陶瓷材料的结构设计及应用提供理论依据及技术指导。

ZrB2/ZrC等超高温陶瓷因其具有独特的优异性能，在航空航天领域有着广阔的应用前景。为改善陶瓷材料固有的脆性，设计和制备颗粒、晶须、纤维等第二相增强的陶瓷基复合材料是超高温陶瓷发展的必然趋势。实现晶须的原位生长，解决其引入及分散均匀性问题，开发出高性能复相陶瓷的快速、低成本制备工艺是陶瓷领域研究的重点。本项目采用前驱体转化法在SiC-ZrB2-ZrC复相陶瓷粉体中原位生长不同尺度的SiC晶须（SiCw），研究了SiC晶须原位生长的影响因素及作用机理，并研究了不同尺度的SiC晶须的强韧化效果，揭示前驱体转化法原位生长SiCw的生长规律及可控生长机理，阐明了SiCw的尺度效应及强韧化机制。研究表明，通过调节前驱体组成及裂解工艺，原位生长的SiC晶须直径可控范围为50nm到800nm，对应的长度为几微米到几百微米，且均匀地分散在陶瓷粉体中；SiCw-ZrB2-ZrC复相陶瓷的物相组成可实现连续变化，且陶瓷颗粒的粒径可细化到100nm左右；对比颗粒增强的陶瓷基体，引入直径约200nm，长度100um左右的SiC纤维，陶瓷基体的裂纹扩展能量释放率（GIC）提高了约56.45%，继续提高增强体纤维的直径，会导致GIC下降，陶瓷基体的断裂韧性降低。本项目为SiC-ZrB2-ZrC等系列超高温陶瓷粉体及SiC纤维增强体的制备积累了大量的技术数据，为SiC纤维增强陶瓷基复合材料的结构设计及应用提供了理论依据及技术指导，并且有望显著降低制备该复合材料的原料成本。此外，利用SiCw-ZrB2-ZrC复相陶瓷的同步原位及可控生长，采用浸渍裂解工艺制备多尺度SiC网络-ZrB2-ZrC改性碳/碳，充分发挥SiC纤维网络及SiC-ZrB2-ZrC陶瓷基体对材料氧化烧蚀的抑制作用，有望显著提高复合材料在极端环境中的抗氧化烧蚀性能，这为超高温陶瓷改性碳/碳复合材料的结构设计提供了借鉴思路。