基于水基树脂凝胶制备的多孔碳调控B4C-SiC-Si复合材料组织与性能的研究

During the fabrication of B4C-SiC-Si ceramic composite via molten silicon infiltration process, the structure and property of ceramic composite are dependent on the amounts and distributions of residue silicon and SiC, which, fundamentally, can be controlled by the porosity and distributions of carbon in the B4C-C perform. In this respect, this project aims to prepare porous B4C-C perform from the water-based resin gel with controllable structures in order to tune the amounts, morphologies and distributions of residue silicon and SiC and thus to optimize the structure and properties of B4C-SiC-Si ceramic composite. This project will investigate the casting process of water-based resin gel, the pore-forming principle of the B4C-C perform, the tuning method of structure of porous carbon as well as the influence of the latter on the amounts, morphologies and distributions of residue silicon and SiC. The establishment of the underlying principle to tune the structure and properties of B4C-SiC-Si ceramic composite via controlling the porous carbon is intended for the optimization of the structure and properties of B4C-SiC-Si ceramic composite. In this work, the stabilization and significant enhancement of the property can be expected for B4C-SiC-Si ceramic composite prepared by molten silicon infiltration method, providing theoretical support to the fabrication of key wear resistant and armor protection materials for our country.

在熔渗Si制备B4C-SiC-Si复合材料过程中，残留Si及SiC的含量和分布直接影响材料的组织与性能，这一问题的本质是B4C-C坯体中孔隙和C分布的控制问题。针对这一问题，本项目利用水基树脂凝胶法制备多孔碳/碳化硼坯体，通过多孔碳调控残留Si和SiC的含量、形貌及分布，实现B4C-SiC-Si复合材料组织与性能的优化。项目将研究多孔碳/B4C坯体的水基树脂凝胶注模成形过程、多孔碳的形成机理、多孔碳孔隙和孔径的调控方法、多孔碳对残留Si和SiC的含量、形貌及分布的影响，建立水基树脂凝胶制备多孔碳、及多孔碳对复合材料中残留Si和SiC的含量、形貌及分布的调控机制,最终通过多孔碳优化B4C-SiC-Si复合材料的组织与性能。通过本课题的研究将使Si熔渗法制备B4C-SiC-Si陶瓷复合材料的性能稳定且大幅度提高，为我国耐磨、防弹领域的关键材料及其制备提供理论支撑。

碳化硼(B4C)材料具有高硬度、低密度，在军工防护领域具有广泛的应用前景。基于凝胶注模成形结合渗Si工艺可以获得致密度高、组织均匀、性能优良的B4C陶瓷材料。但制备的B4C-SiC-Si复合材料存在组织和性能不易调控的问题，本项目通过树脂水基凝胶工艺制备了碳含量及孔隙结构可调的多孔C/B4C坯体；通过研究多孔C形成过程、多孔C孔隙的调控机制、多孔C对残留Si和SiC的含量、形貌和分布的影响规律，并基于熔渗反应的动力学过程，建立了水基树脂凝胶注模成形制备多孔C、及多孔C调控复合材料中残留Si与SiC的含量、形貌和分布的机制；进而实现了B4C-SiC-Si复合材料组织与性能的优化。项目研究为我国军工防护、核电保护和耐磨领域的关键材料制备及应用提供理论支撑。项目主要取得以下研究结果：（1）确立了间苯二酚-甲醛体系凝胶注模成型机理：间苯二酚与甲醛在碱性催化剂的作用下发生缩聚反应，生成以亚甲基键和亚甲基醚键连接的聚合物，并将B4C颗粒“固定”其中实现成型。固化体经高温碳化后形成多孔B4C/C预制体。利用渗硅工艺制得B4C-SiC-Si陶瓷复合材料。（2）通过粉体预处理、颗粒级配及添加分散剂提高了浆料固含量。确定当添加TMAH、B4C颗粒级配F320：F800：W3.5=6:1:3时浆料粘度最低。（3）选用不同体系催化剂对预制体孔径进行了调控。利用Na2CO3、NaHCO3、NaOH、KOH四种催化剂及不同Na2CO3含量均可实现对多孔B4C/C预制体孔径的精确调控，并分别制备了单一大孔、单一介孔和等级大孔-介孔结构的多孔B4C/C预制体。（4）研究了B4C-SiC-Si陶瓷复合材料的组织，确定材料由BxC、SiC、B12(C,Si,B)3和残余Si相组成。残余Si含量最低可降至7.22 vol%。当预制体最可几孔径为49 nm时，B4C-SiC-Si陶瓷复合材料弯曲强度和断裂韧性分别为419±17 MPa和4.12±0.12 MPa·m1/2。（5）研究了新型AM-MBAM凝胶体系对B4C-SiC-Si复合材料组织与性能的影响。确定了适宜的引发剂用量为0.5~0.7 wt%；固相体积分数为60 vol%的B4C-水浆料为比较适合凝胶注模成型的浆料，成型坯体的组织均匀，无明显缺陷，密度达到1.56 g/cm3；渗Si得到的B4C-SiC-Si复合材料硬度、抗弯强度、断裂韧性和密