SiC纳米线增韧SiC镜面涂层的原位可控制备与强韧机制

CVD-SiC coating is the most ideal coating for C/C composites applied in space mirror. However, the CVD-SiC coating has great brittleness and low bonding strength with C/C substrate, which will results in the coating easily cracked and poor optical finishing property. In order to solve these problems, this project proposes the idea about introducing SiC nanowires (SiCNWs) reinforced skeleton to prepare SiCNWs toughened SiC coating (SiCNWs-SiC). This project will focus on morphology and microstructure controllable growth of SiCNWs, controlling the microstructure of SiCNWs-SiC coating and strengthening and toughening mechanism of SiCNWs. The final aim is to improve the properties of CVD-SiC coating by means of toughening and strengthening of SiCNWs. To achieve controllable preparation of SiCNWs, this project will study the process of SiCNWs growth on C/C substrate systematically and reveal the growth mechanism of SiCNWs. Furthermore, the strengthening and toughening mechanism of SiCNWs in SiC coating or interface between C/C matrix and the coating will be explored through investigating the effect of SiCNWs with different morphology and microstructure on the densification process, microstructure and properties of SiCNWs-SiC coating, and finally obtain the technics of microstructure controllable preparation of SiCNWs-SiC coating. The accomplishment of this project will provide a meaningful way for producing SiC mirror coating with excellent properties on C/C composites applied in the field of space mirror.

针对反射镜用C/C复合材料表面理想镜面涂层CVD-SiC脆性大、与C/C基体结合力弱及其导致的涂层易开裂、光学加工性能差等问题，本项目提出在C/C表面引入SiC纳米线（SiCNWs）增强骨架制备SiCNWs增韧的SiC涂层（SiCNWs-SiC）。围绕SiCNWs形貌和结构可控生长、SiCNWs-SiC涂层微观结构控制及SiCNWs的强韧机制开展深入研究，旨在借助SiCNWs增强增韧作用，实现SiC镜面涂层性能提升。拟系统研究SiCNWs在C/C表面的生长过程，揭示不同形貌和结构SiCNWs的生长机理，实现其可控制备；阐明SiCNWs形貌和结构对SiCNWs-SiC涂层致密化过程、微观结构和性能的影响规律，揭示涂层中及界面处的SiCNWs的强韧机制，实现涂层微观结构可控制备，为空间反射镜用C/C复合材料表面高性能SiC镜面涂层的制备奠定理论基础。

针对反射镜用C/C复合材料表面理想镜面涂层CVD-SiC脆性大、与C/C基体结合力弱及其导致的涂层易开裂、光学加工性能差等问题，本项目提出在C/C表面引入SiC纳米线（SiCNWs）增强骨架制备SiCNWs增韧的SiC涂层（SiCNWs-SiC）。围绕SiCNWs形貌和结构可控生长、SiCNWs-SiC涂层微观结构控制及SiCNWs的强韧机制开展深入研究，旨在借助SiCNWs增强增韧作用，实现SiC镜面涂层性能提升。系统研究了SiCNWs在C/C表面的生长过程，揭示了不同形貌和结构SiCNWs的生长机理，实现了其可控制备；阐明了SiCNWs形貌和结构对SiCNWs-SiC涂层致密化过程、微观结构和性能的影响规律，揭示了涂层中及界面处的SiCNWs的强韧机制，实现涂层微观结构可控制备，为空间反射镜用C/C复合材料表面高性能SiC镜面涂层的制备奠定理论基础。结果如下：引入SiCNW后，SiC涂层C/C试样的弯曲强度从107.2 MPa提高到134.3 MPa，涂层的断裂韧性也从9.1 MPa·m-1/2提高到19.7 MPa·m-1/2，CVD-SiC涂层与C/C基体的结合力从6.7 MPa提高到14.2 MPa；SiCNW通过裂纹偏转、桥联、拔出等机制，显著有效地增韧了SiC涂层，使得SiCNW-SiC涂层的抗氧化性能明显优于纯CVD-SiC涂层，其在1400℃下氧化420 h，失重仅为0.4%，热震30次后失重也仅有2.5%。