本项目拟采用化学法制备纳米孪晶结构的B4C粉体(约10~30nm左右)为原料，经SPS或高压烧结后制备出新型纳米孪晶B4C陶瓷材料。为防止在烧结过程中B4C晶粒长大，用原子层沉积系统ALD在纳米孪晶B4C粉体的表面均匀沉积一层TiO2或其它氧化物薄膜涂层。分别研究无涂层/有涂层纳米孪晶B4C粉体在SPS或高压烧结过程中组织结构变化和烧结体致密化规律，测定B4C烧结体块材的硬度、压缩强度、断裂韧性和抗氧化性能等特性，研究纳米孪晶厚度对纳米孪晶B4C块材性能的影响规律；确定出具有高硬度、高韧性B4C块材的组织结构特征以及相应的工艺参数，阐明B4C块材力学性能、抗氧化性能与其微观结构的关系，获得具有超硬、高韧性和高抗氧化性能的B4C陶瓷材料。采用第一性原理和分子动力学计算与透射电镜测试分析相结合，揭示B4C纳米粉体颗粒中高密度孪晶的形成机理和孪晶对B4C强化的微观机理。

A new nano-twinned crystal B4C ceramic material will be prepared by SPS or high pressure sintering with nano-twinned B4C powder (about 10 ~ 30nm) prepared by a chemical method. In order to prevent the B4C grains from growing up during the sintering process, a layer of TiO2 or other oxide film coating will be uniformly deposited on the surface of the nano-twinned B4C powder by the atomic layer deposition system ALD. The changes of microstructures and the densification of sintered compacts of uncoated/coated nano-twinned B4C powder during the SPS or high pressure sintering process will be studied respectively. The hardness, compressive strength, fracture toughness and oxidation resistance of B4C sintered compacts will be detected. The effect of nano-twinned thickness on the properties of nano-twinned B4C compacts will be studied. The structural characteristics of B4C block with high hardness and high toughness as well as the corresponding process parameters will be determined. The relationship between mechanical properties, oxidation resistance and microstructure of B4C bulk will be clarified. B4C ceramic materials with superhard, high toughness and high oxidation resistance wii be obtained. The formation mechanism of high density twinning in B4C nanometer powder particles and the microscopic mechanism of twinning on B4C strengthening will be revealed by the combination of the first principle and the molecular dynamics calculation and the transmission electron microscopy test.