用不同粒度的洋葱BN和不同规格的BN纳米管为原料，采用Rocklend T25压机，在~25GPa、~2000℃的高温高压实验参数范围内，合成具有不同性能的纳米孪晶cBN块材。系统地研究洋葱BN的粒度和BN纳米管规格、合成条件（压力、温度、高压介质材料）和相变产物(纳米孪晶cBN及新型BN亚稳相)结构与性能之间的关系，测绘纳米孪晶cBN的高压相图。 研究洋葱BN和BN纳米管向纳米孪晶cBN和BN新相转变的相变机理，结合第一性原理计算研究纳米孪晶BN的组织结构和BN新相的晶体结构。研究合成产物的硬度、韧性和抗氧化温度的影响因素，通过调控原料尺度和合成工艺条件得到具有不同孪晶厚度的纳米孪晶cBN块材，获得具有最高硬度、最高韧性和最高抗氧化温度纳米孪晶cBN的最佳工艺条件。

Nanotwinned cubic boron nitride (nt-cBN) bulk materials with various properties will be synthesized by employing onion BN with different diameters and BN nanotube with different sizes as raw materials under pressure of ~25 GPa and temperature of ~2000 C by Rockland T25 press. The relationships among the raw materials features, external conditions (e.g. pressure, temperature, and pressure transmitting medium) , the microstructure of quenched phase (e.g., nt-cBN and novel metastable BN allotropes) and properties of the products will be systematically researched. Furthermore, the high pressure phase diagram of nt-cBN will be detected. The mechanism of transitions of o-BN→nt-cBN, BN nanotube→nt-cBN, o-BN→new BN and BN nanotube→new BN will be studied. By means of first principle calculations, the microstructures of nt-cBN and the crystal structure of novel metastable BN allotropes will be simulated. The influencing factors of hardness, toughness, and antioxidation temperature of the synthesized products will be investigated. The nt-cBNs bulk with different twin thickness would be obtained through adjusting the dimensions of raw materials and synthesizing process. The best synthesizing processes of the nt-cBN bulks with the highest hardness, toughness, and antioxidization temperature will be gained.