碳化硅纳米线支撑轻质绝热碳泡沫及其界面组织结构演变研究

Our country is developing Mars lander and rover systems. It is known that Mars rover urgently needed new aerogel supporter to meet demand of thermal insulation, due to the harsh thermal environment on the Mar surface ( temperature change from -175~30℃). Therefore, a new aerogel supporter should possess low density, low thermal conductivity, high strength, and zero-shrink property under thermal cycling condition, while existing supporter could not satisfy this demand. On the basis of the excellent thermal insulation property of lightweight carbon foam, SiC nanowires are grown within the carbon foam via chemical vapor deposition process, in this project. The carbon foam was supported by SiC nanowires with high strength and modulus, which prohibits the deformation of carbon foam and maintains the foam structure stability. The macro-pores within the carbon foam are divided by random distribution of SiC nanowires resulted in much more micro-pores, which could reduce the thermal conductivity of carbon foam. Besides, high thermal radiation property and huge specific area of the SiC nanowires can also reduce the thermal conductivity of carbon foam. The SiC nanowires were growing via chemical vapor deposition after incompletely paralyzing melamine foam, which can avoid the great contraction and the decrease in volume and prevent the continuous SiC film generating on the carbon skeleton. As a result, the strength of carbon foam increases while the density was not affected. This project systematically studies the influence of SiC nanowires on strength, thermal insulation and contraction of the carbon foam and the evolution mechanism of the carbon wall interface structure. This project will also provide solutions and ideas for exploring new aerogel supporter.

火星温度从-175~30℃，环境非常苛刻，国家正在发展的火星探测迫切需要新型气凝胶承载体来满足保温需求，对气凝胶载体提出了低容重、低热导、高强度、冷热交变环境零收缩的指标，现有的载体难以达到要求。本项目基于柔性碳泡沫的优异隔热性能以及超轻特性，拟以化学气相沉积方法在碳泡内生长SiC纳米线，利用高强高模SiC纳米线支撑碳泡沫，抑制其收缩和膨胀，保障碳泡沫骨架的结构稳定性；同时利用SiC纳米线空间缠绕对碳泡进行分割，形成更多更细小空穴，利用SiC纳米线的热辐射特性和巨大的比表面积对热进行辐射，共同降低碳泡沫的热导率。创新性提出在三聚氰胺泡沫半分解后进行化学气相沉积SiC纳米线，避免了大的收缩和体积减小，阻止在碳泡壁上形成连续的SiC膜，对碳泡沫起到增强不增重的作用。系统研究SiC纳米线特征对强度、隔热、收缩性能的影响规律以及与碳壁的界面组织结构演变规律，为探索新的气凝胶载体提供解决思路和方法。

本项目以深空探测的隔热需求为背景，以满足我国未来火星探测为目标，针对目前深空探测器保温用气凝胶增强材料厚度大、重量重、易收缩变形、隔热效率低等问题，提出了一种以 SiC 纳米线嵌入碳泡沫孔内形成支柱支撑的低容重、低热导、高强度、热循环零收缩的气凝胶用碳泡沫增强材料。为获得低容重和高稳定性，在未完全分解的三聚氰胺泡沫骨架表面制备催化剂，再采用脉冲 CVI 结合强制 CVI 工艺制备 SiC 纳米线。纳米线生长过程中沉积和热分解同时进行，实现动态生长，抑制了三聚氰胺泡沫热解过程的收缩；在碳化硅纳米线生长完成后，再将泡沫高温碳化处理，由于 SiC纳米线支撑，泡沫壁原位碳化限制了泡沫体积收缩，从而保证了低容重。.依托本项目发表学术论文31篇，授权发明专利8项，获得相关国家级项目2项，获得相关省部级奖项3项。.依托本项目，为祝融号提供气凝胶载体，并获得应用，已在火星运行1年多时间，收到火星项目办公室感谢信，希望本项目继续推进，实现在探日方面的进一步应用。