根据我们发展的理论模型，多晶共价材料的硬度应源于Hall-Petch效应和量子限域效应的共同贡献；在纳米尺度，量子限域效应引起的硬化完全可能补偿掉晶界滑移所引起的软化。根据这一原理，我们进行两个方面的探索：一是如何将超硬材料变得极硬，二是如何将硬材料变得超硬。为此，我们将研究极性共价前驱物材料在高压下的结构相变和组织演化，揭示相变条件和显微组织与前驱物材料的结构特征和晶粒尺寸的关系，开展纳米结构块材的微结构设计和力学性能调控研究。采用高温高压技术，合成出极硬的纳米结构金刚石、立方BN及其复合材料块材，并将SiO2和AlN这些非超硬材料制成超硬的纳米结构材料。在此基础上，我们将开展分子动力学模拟，揭示出高压下的组织演化规律，阐明纳米结构块材的硬化机制；力争在这些纳米结构材料中发现新的硬化和韧化现象，阐明其物理根源，为发展下一代高性能超硬材料提供科学依据、设计策略和合成技术。

According to the theoretical model we have developed, hardness of a polycrystalline covalent material should come from the common contributions of Hall-Petch and quantum confinement effects. At the nanoscale, the hardening from the quantum confinement effect could fully compensate the softening from grain-boundary sliding. According to this principle, our explorations are in the two aspects: how to make superhard materials ultrahard, and how to make hard materials superhard. We will study the structural phase transitions and microstructural evolutions of polar covalent precursor materials under high pressures, reveal the effects of structural characteristics and grain sizes for precursor materials on phase-transition conditions and microstructures of synthetic products, and explore the methods of microstructure design and performance adjustment for nanostructured bulk materials. Using high-temperature and high-pressure technology, we will synthesize ultrahard nanostructured bulks of diamond, cubic BN and their composites, and synthesize superhard nanostructured materials of SiO2 and AlN that are not intrinsically superhard. Based on these results, we will carry out molecular dynamics simulations to reveal the microstructural evolutions under high pressures and to clarify the hardening mechanism of the nanostructured bulk materials. In these nanostructured materials, we will strive to find new hardening and toughening phenomena, to clarify their physical origins, and to provide scientific basis, design strategy and synthesis technology for the development of the next generation of high-performance superhard materials.