SiC纳米纤维改性Cf/Si3N4吸波材料微结构优化及微波响应特性与机理研究

With the rapid development of the military high and new technology, the development of high-speed aircraft and a new generation of fighter in our country urgent need high-temperature structural absorbing materials to improve their survival and penetration ability. In this project, through in-situ growth SiC nanofibers (SiCNF) on the ordinary domestic carbon fibers, SiCNF are designed to improve the electrical properties and synergize the mechanical properties of carbon fibers, and solve the chemical incompatibility between carbon fibers and Si3N4 matrix. Thus, optimize the interface microstructure and increase the fiber content, and give full play to the absorbing and enhance toughening effect of the carbon fibers and SiCNF, and finally improve the microwave absorption efficiency and loading capacity of Cf/Si3N4 absorbing materials.The interface binding characteristic between carbon fibers and Si3N4 matrix are studied. The influencing mechanism of SiCNF on the forming process of Si3N4 matrix and the microstructure of interface layer are investigated. The mechanical properties and failure mechanism of the nanofiber modified absorbing materials are studied. The microwave response characteristic and mechanism under different temperatures are investigated. The relationship between microwave response mechanism and material microstructure, the match between microwave response properties and mechanical properties are explored, and the optimal control method is proposed, which lays the theoretical and methodological basis for the design, preparation and application of high-performance Cf/Si3N4 high-temperature structure absorbing materials.

随着军事高新技术的迅猛发展，我国高速飞行器和新一代战机的研制迫切需求耐高温结构吸波材料，提高其生存与突防能力。本项目设计具有优异吸波和力学性能的SiC纳米纤维（SiCNF）新组元，通过在普通国产炭纤维表面原位生长SiCNF，改善炭纤维的电性能并协同其力学性能，同时解决炭纤维与Si3N4基体的高温化学不相容，优化界面微结构并提高纤维含量，充分发挥炭纤维和SiCNF的吸波及增强增韧作用，提高Cf/Si3N4吸波材料的雷达微波吸收效率和承载能力。研究炭纤维与Si3N4基体的界面结合特征，阐明SiCNF对Si3N4基体成型过程以及界面层微结构的影响机制；研究不同温度下改性吸波材料介电及吸波性能的演变规律、SiCNF对材料微波响应特性的影响机制，揭示改性材料的微波响应机理及其与材料微观组织结构的内在关联，提出优化控制方法，为设计制备高性能耐高温Cf/Si3N4结构吸波材料及其应用奠定理论和方法基础。

本项目组开展研究工作三年来，已完成或超额完成了各项研究内容，优化设计了SiC纳米纤维改性Cf/Si3N4吸波材料结构，研究了炭纤维/Si3N4界面层微结构及改性材料的力学性能、吸波性能温度演变规律，探明了SiC纳米纤维（SiCNFs）对界面层微结构的影响机制以及材料微波响应特性与机理。. 研究结果表明：表面原位生长SiCNFs是一种有效改善碳纤维微波吸收性能的方法，同时显著其提高抗氧化性。引入SiCNFs，可以有效提高Cf与Si3N4基体在高温下的化学相容性。Cf/Si3N4复合材料的介电响应和微波吸收性能受SiCNFs含量的影响显著，含有8wt％SiCNFs的Cf/Si3N4复合材料在X波段可以实现-14dB的最佳反射损耗和96％的吸收带宽。相比于短Cf内自由电子的弛豫损耗，SiCNFs之间的电子跃迁弛豫对SiCNFs改性Cf/Si3N4吸波材料优异的微波衰减能力具有更明显的贡献。SiCNFs改性Cf/Si3N4吸波材料的弯曲强度从521MPa降低到371MPa，而断裂韧性从3.51MPa•m1/2增加到7.23MPa•m1/2，增加两倍以上。当温度从25℃升高到800℃时，改性材料表现出温度相关的复介电常数，衰减常数和阻抗。改性材料在高温下具有高的微波衰减能力，在800℃、厚度2.0mm时，最小反射损耗可达-20.3dB。. 在本项目的资助下，项目的相关研究成果被项目负责人以第一或通讯作者发表SCI收录期刊论文21篇，并参与发表SCI/EI收录期刊论文8篇，获得授权国家发明专利1项，获湖南省科学技术发明奖二等奖1项（排名第四），参加国内学术会议4次，以访问学者身份在德国拜罗伊特大学陶瓷工程材料系合作研究1年，联合培养硕士研究生1人。