超硬材料c-BN纳米晶的可控制备与压电性质研究

Semiconductor nanocrystals composed of limited number of atoms usually show distinct physicochemical properties when compared with their bulk counterpart. This phenomenon can be recognized as the quantum size effect, which is of crucial importance to suit either a particular technological application or the needs of a certain experiment designed to address a specific research problem. As a member of semiconductor materials, ultrahard material c-BN with a nano-sized dimension has already been predicted to possess numerous excellent merits by modern calculations. However, extremely strong covalent interactions existed between lattice atoms makes it a great challenge to obtain fine c-BN nanocrystals with perfect grain boundaries. In our recent work, we suggest an effective method to gain monodispersed c-BN nanoparticles with an average diameter of about 3.4 nm via electrochemical shock. A six-time enhancement in piezoelectric properties over bulk c-BN has been observed with our c-BN nanocrystals. In this project, we will explore an effective way to more precisely modulate the size and facet of the obtained nanocrystals, investigate the relationship between crystal structure and electromechanical coupling of c-BN with quantum size, and uncover the dimensionally reduction mechanism of ultrahard materials under electrochemical conditions. The study will provide a new route to the preparation of nano-sized ultrahard semiconductors, and bring new vigor and vitality to the development of both basic and applied research of these materials.

量子尺寸效应下，仅由有限原子组成的半导体纳米晶通常展现出与块体不同的物理化学性质，这对理论探索或技术应用都有着重要价值。作为半导体材料的成员之一，超硬材料c-BN纳米晶的众多优异性能已被当代理论计算所预测，然而其晶格原子间极强的共价相互作用使得目前获得小尺寸且晶界完整的c-BN纳米晶仍是一项技术难题。在前期工作中我们通过电化学冲击的方式获得了平均粒径约为3.4 nm的单分散c-BN纳米晶，并观察到其压电效应较块体有着近6倍的提升。然而这些工作还有许多关键科学问题没有得到清晰的解释和证明。本项目拟通过对材料尺寸、晶面的可控调节，研究量子尺寸效应下c-BN晶体结构与机电转换性质之间的关系，并探讨电化学条件下超硬材料纳米晶的生成机制。该项研究将为超硬材料纳米晶的制备与应用探索提供全新途径，为纳米尺度下超硬材料的应用或基础研究注入新的活力。

通过本项目的实施，我们初步掌握了超硬材料纳米晶的电化学低维化方法，揭示压电材料晶体结构、小尺寸效应和电子结构与机电转化性能之间的关联。在达到项目预期目标的基础上，我们进一步探索了微观界面效应对BN材料晶格形变以及压电性能的影响，获得了单原子（W元素）锚定的BN材料，并显著提升其压电性能。. 此外，在本项目资助下，我们聚焦于低维材料制备、表界面效应与光电化学应用之间的联系，在能源催化、表面增强拉曼散射（SERS）、电致变色三个应用方向做了一系列的探索工作，并取得了突破进展。项目标注论文23篇，申请发明专利20项，授权发明专利4项，培养研究生8名。. 本项目成果将为超硬材料的低维化提供新方法，为理解低维材料表界面结构与光电性质联系提供新知识，并为拓展传统材料在新领域的应用提供新途径。