基于有机先驱体的SiCf/BN/SiBN复合材料的制备及其力学、介电性能

In order to solve the problems existed in the high-temperature microwave absorbing materials, SiCf/BN/SiBN composites fabricated from organic precursor were put forward. In SiCf/BN/SiBN composites, SiC fiber was employed as reinforcement and microwave absorbent. BN prepared by CVD process deposited from borazine was employed as interphase which was used to improve the compatibility between mechanical and dielectric properties of the composites. SiBN ceramic fabricated from liquid polyborosilazane was employed as matrix which was used to improve the temperature stability of microwave absorbing properties and enhance the densification efficiency of the composites, which are due to the "neutralization effect" derived from the opposite temperature coefficient of dielectric constant between SiC fiber and SiBN ceramic and the high ceramic yield characteristics of polyborosilazane, respectively. To the best of our knowledge, the investigations on the SiCf/BN/SiBN composites have not been reported before. The mechanisms of BN deposition, principles of cross-linking and pyrolysis of polyborosilazane and regulations of dielectric temperature characteristics of SiBN ceramic will be studied as primary research contents. The original works about the polarization mechanisms of SiBN ceramic at high-temperature and modeling of dielectric temperature characteristics of SiCf/BN/SiBN composites will be executed. This project is important for enhancing the properties of high-temperature microwave absorbing materials and expanding the material system of high-temperature functional ceramic. At the same time, the foundations can be made for the investigations on the dielectric properties and their temperature characteristic regulations of high-temperature functional ceramic, such as high-temperature microwave absorbing materials, high-temperature microwave transmitting materials and high-power-density microwave dielectric ceramic.

本项目提出了基于有机先驱体制备的SiCf/BN/SiBN复合材料以期解决目前高温雷达吸波材料存在的问题。其中，碳化硅纤维为增强体和吸波体；环硼氮烷为气源的CVD工艺制备的BN为界面相，以改善复合材料的力学与介电性能兼容性；高陶瓷产率的液态聚硼硅氮烷为先驱体制备的SiBN陶瓷为基体，利用其与碳化硅纤维相反的介电常数温度系数特性产生的"中和效应"改善复合材料的吸波性能温度稳定性，同时提高复合材料的致密化效率。目前关于此材料体系的研究工作尚未见报道。本项目将重点开展BN沉积机理，聚硼硅氮烷交联、裂解机制，SiBN陶瓷介电性能温谱特性调控等研究内容，将在材料高温极化机理、介电性能温谱特性建模等方面开展原创性工作。本项目对提升高温雷达吸波材料性能、拓展高温功能陶瓷材料体系具有重要意义，可为高温吸波、高温透波、大功率密度微波介质陶瓷等高温功能陶瓷材料的介电性能及其温谱特性调控研究工作奠定基础。

项目研究背景针对目前高温吸波材料体系存在的力、电性能难以兼容、电性能随温度变化较大、吸波性能不稳定的问题，提出了基于有机先驱体制备的SiCf/BN/SiBN复合材料以期解决目前高温雷达吸波材料存在的问题。主要研究内容包括碳化硅纤维表面BN涂层的制备、PBSZ的交联、裂解机制、SiCf/BN/SiBN复合材料的制备及其力学性能分析、SiCf/BN/SiBN复合材料的介电性能研究等。本项目以硼吖嗪为气源，采用CVD工艺成功的在碳化硅纤维表面制备出BN涂层，采用全氢聚硅氮烷（PHPS）与硼氮烷（PBZ）按一定比例混合反应得到了SiBN陶瓷先驱体PBSZ。采用先驱体转化工艺成功制备出SiCf/BN/SiBN复合材料，研究结果表明，BN界面相可以显著提高复合材料力学性能，同时SiBN陶瓷具有较好的介电性能温度稳定性，以其为陶瓷基体制备的SiCf/BN/SiBN复合材料介电常数随温度变化幅度不大，达到了项目解决复合材料力学与介电性能兼容、减小复合材料介电常数随温度变化幅度的目的。科学意义在于针对特殊背景的应用问题提出了一种全新的陶瓷基复合材料体系，研究的关于BN涂层沉积机理、SiBN陶瓷以及SiCf/BN/SiBN复合材料的介电性能及其随温度的变化规律及机理具有普适意义，对于从事本领域研究工作同行具有一定借鉴意义。