螺旋竹节状SiC纳米线结构精细调控及其强韧化硅基陶瓷涂层研究

Silicon-based ceramic coating is an important coating system against oxidation and ablation for C/C composites. In the project, directed by the investigation of toughening Silicon-based ceramic coating efficiently, the in-suit helical bamboo-shaped SiC nanowires are considered as the key materials for strengthening and toughening to further improve the intrinsic fracture toughness and the bonding ability with C/C substrate of these coatings. In order to realize precisely controlled microstructure droplets is proposed. Synergy control of magnetic field and temperature was suggested for regulating the morphology to construct the helical bamboo-like structure of SiC nanowires. Raw material composition and ratio, the reaction environment parameters were regulated to explore the control discipline of solid-liquid interface dynamic process of SiC nanowire growth, analyze the microstructure evolution rule and reveal the structure regulation mechanism of helical bamboo-like SiC nanowire.e of helical bamboo-shaped SiC nanowires, the idea of regulating morphology of catalyst alloy.. Synergistic regulation discipline for the strength and toughness performance of silicon-based ceramic coating was revealed by controlled structure and distribution of the SiC nanowire. Additionally, the failure mechanism of the coating in several service environments will also be discussed to help revealing the strength and toughness mechanism of SiC nanowires with special morphology. and provides a theoretical basis for the technology of high efficient toughening silicon based ceramic coating by helical bamboo-like SiC nanowires.

硅基陶瓷涂层是C/C复合材料重要的防氧化抗烧蚀涂层体系，本项目针对硅基陶瓷涂层自身固有的脆性以及与基体之间弱界面结合等难题，以高效增韧硅基陶瓷涂层的研发为导向，提出了原位螺旋竹节状SiC纳米线强韧化硅基陶瓷涂层技术。为了实现SiC纳米线螺旋竹节状结构的精细控制，提出了催化剂合金液滴形态调控SiC纳米线结构的思路。利用磁场与温度协同调控催化剂合金液滴形态，通过控制原料组成、配比及反应环境参数，探索SiC纳米线生长固液界面动力学过程的控制规律，解析SiC纳米线组织结构演变规律，揭示螺旋竹节状SiC纳米线的结构调控机制。. 通过控制SiC纳米线的结构参数及分布状态，揭示SiC纳米线结构、分布与硅基陶瓷涂层强韧性能的协同调控规律；通过分析涂层极端环境服役的失效机理，揭示特殊形貌SiC纳米线的强韧机制，为螺旋竹节状SiC纳米线高效强韧化硅基陶瓷涂层技术提供理论基础。

本项目从原位生长螺旋竹节状SiC纳米线的结构调控、SiC纳米线高效强韧化硅基陶瓷涂层等关键技术存在的瓶颈进行深入研究。在SiC纳米线结构调控方面，利用催化剂调控SiC纳米线结构的思路，通过控制催化剂种类、反应温度、气体引入及制备方式，能有效调整SiC纳米线的形貌，直径在60-300nm范围内的可控调节，并且实现了螺旋状和竹节状SiC纳米线的原位制备，得到的螺旋状结构的SiC纳米线的直径约为80 nm，螺距约为160 nm；竹节状SiC纳米线的直径约为200nm，竹节节点约为300-350nm，竹节的周期性可通过反应温度的周期性变化调节。在SiC纳米线高效强韧化硅基陶瓷涂层方面，通过控制SiC纳米线的数量、厚度和活性位点等分布，可以实现涂层与基地结合强度的大幅度提高和抗热震性能的显著提升。针对在C/SiC复合材料表面利用CVD法制备的SiC涂层，SiC纳米线的合理引入使涂层与基体的结合强度达到4.5MPa，相比未引入线状SiC纳米线时提高了约1.5倍，基本达到C/SiC复合材料的层间强度，此时涂层在经过从室温到1873K的9次热震实验后，其失重率仅为4.6%。此外，在不同厚度的Si涂层中引入同样的SiC纳米线，Si涂层的抗热震性能差异较大，表明涂层的特点对SiC纳米线的强韧化效果有较大的影响。本项目的研究通过SiC纳米线结构的调控，解决了陶瓷涂层固有脆性以及基体截面结合较弱的问题，有效改善涂层极端环境的服役性能，有望实现硅基陶瓷涂层的长效应用。