原位自生构建双元SiC多孔材料及其微波吸收与力学性能研究

The shortage of lightweight, high-performance and thermostable structural radar microwave absorbing materials has become the bottleneck of development of high-temperature stealth aircrafts. To address this issue, present research proposal will design and fabricate novel dual SiC porous materials where SiC heterojunction nanowires with superplastic and coupled dielectric property as the frameworks, which will integrate the microwave absorbing and mechanical properties together. The dual SiC nanowires are connected as heterojunction, which will enhance the microwave absorption by synergistic interaction. The mechanical property of the materials will be improved by native superplastic and draw bridging of the SiC nanowires. By carrying out systematical investigation, the nucleation and growth of second SiC nanowires within the SiC porous will be clarified. The controllable fabrication model with desired structure and morphology is to be proposed. Through lucubrating the dependency of electromagnetic parameters and dielectric relaxation on the microstructure and temperature, the mechanism of synergistic interaction to enhance microwave absorption from dual SiC dielectric hybrids will be discussed. Meanwhile, researching into the variation of strength and toughness with the microstructure and temperature makes the fracture mechanism of the dual nanowires-based porous materials clarified. Based on these analyses, the optimum selection of high-performance functional-structural integral microwave absorbers will be achievable. The carrying out of this research will be beneficial to knowing the physical essence of the attenuation of electromagnetic waves within dielectric-dielectric hybrid materials, broadening the application of in situ growth processing in material science and propelling the development of novel high-performance stealth materials. Furthermore, this research has the obvious interdisciplinary characteristic and prominent innovation on integrating theories, methods and techniques. This research will develop stealth science and technology, and give the scientific guideline for the design of thermostable stealthy materials.

轻质、高效、耐高温结构型吸波材料匮乏是当前高温隐身武器发展的瓶颈问题，本项目拟利用原位自生技术构建以具有超塑性和不同介电性能的双元SiC纳米线异质结为骨架的多孔材料，双元SiC异质结通过介电弛豫耦合实现高效吸波，通过自身超塑性和拔出桥联等强化力学性能。通过本项研究，将明确多孔SiC内原位自生第二元SiC的生成/生长过程，发展微结构可控的双元SiC多孔材料制备方法；研究双元SiC的介电弛豫对微结构及温度依赖关系，确定异质复合增效吸波机制，明确双元SiC多孔材料断裂失效行为，建立微观结构与吸波/力学性能之间的构效关系。本项研究有助于学术界认识电磁波在介电-介电异质结中传输损耗的物理本质和共性科学规律，拓展原位自生技术在材料制备方面的应用范畴，促进新概念高性能隐身材料研发。同时，本研究有明显的学科交叉特色和突出的理论、方法和技术集成创新，可丰富和发展隐身理论，为高温隐身材料设计奠定科学基础。

本项目从多组元功能材料的制备入手，实现了双元多孔SiC材料可控制备和表征。考察了不同催化剂浓度、微观形貌和电子结构对第二元SiC纳米线形核、生长，双元SiC多孔材料的雷达微波吸收特性和力学性能的影响规律，并对雷达微波吸收和力学性能的高温稳定性进行了评价。明确了双元SiC多孔材料可控制备机理，确立了骨架组元-双元结构-吸波性能的构效关系，实现了大幅度提升SiC基材料的微波吸收和力学性能。研究发现如下：.（1）在第一元SiC多孔骨架内部以二茂铁作为催化剂提供第二元SiC成核位点，基于气液固三相反应调控，成功制备出具有串珠状形貌第二元SiC相。相对比单一SiC多孔骨架，双元多孔SiC的C未占据轨道态密度降低。.（2）双元多孔SiC具备优异的高温吸波性能，其吸收性能取决于第二元SiC生长数量，常温下最佳吸波性能在2.2mm厚度下可达到-29dB，低于-10dB的有效吸收带宽为3.2GHz，高温环境下最低反射损耗可进一步低至-51dB。.（3）双元SiC结构通过介电弛豫耦合增效吸波性能，高孔隙率利于阻抗匹配的形成使电磁波进入材料内部；碳化硅晶须与珠状碳化硅之间存在大量界面，有利于界面极化，触发界面偶极子极化以及弛豫现象的产生；第二元SiC的生长引入异质结处电荷累积促进介电损耗，Fe基催化剂的存在引入磁损耗，这些多重损耗机制带来提升的吸波性能。.（4）第二元SiC作为桁架在多孔结构内部交织生长，与SiC晶须编织在一起，共同抵抗和延迟了多孔碳化硅的脆性断裂，这种原位自生结构会大大提高材料的力学性能。.这些研究对于集优异力学性能、高效电磁波吸收性能于一体的材料设计和开发具有借鉴意义。项目执行阶段，在J. Am. Chem. Soc.、J. Mater. Chem. A、ACS Appl. Mater. Interfaces等SCI期刊上发表学术论13篇，影响因子总和为88.33，其中3篇文章被选为封面，1篇被选为期刊亮点论文。发表中文核心期刊论文1篇。申请专利10项，其中获得授权专利2项，在国际学术会议上作分会场报告5次，在国内学术会议上作分会场报告3次。