激光液相烧蚀制备超硬立方氮化硼量子点

Cubic boron nitride (cBN), as a superhard material, possesses a similar molecular structure to diamond. Single cubic boron nitride crystal has a Vickers hardness of 62GPa, but polycrystalline cubic boron nitride has an even higher hardness than diamond. Meanwhile, cBN exhibits better thermal and chemical stability than diamond. For superhard materials, grain refinement is an effective means of improving the hardness. Previous studies had shown that the hardness of cBN was continuously increasing along with the particle size decrease at a few nanometers scale, following the Hall-Petch relationships in other words. Laser ablation in liquid (LAL) is a simple and versatile method to synthesize various nanoparticles, and for the past ten years, researchers have adequately used the unique features of LAL to fabricate various products with novel morphologies, metastable or new phases, which were usually unattainable by other methods. Ammonia borane (AB) is an important material for hydrogen storage, but the morphology and properties of the final boron nitride product has not yet studied. In this proposal, we suggest a hypothesis on the preparation of cBN quantumdots, which involves dehydrogenation of AB by the induction of pulse laser. Such a hypothesis was supported by our primary experimental results. To testify this hypothesis, we design research plan from the calculation and experiment aspects. Furthermore, the mechanisms of the dehydrogenation of AB and formation of cBN are studied. Finally, we plan to investigate the influence of particles size on the phase of BN so as to provide experiment support to the construction of H-P phase of BN.

立方氮化硼作为一种超硬材料，具有与金刚石中的碳原子结构类似的原子结构，其单晶体的维氏硬度为62GPa，但其纳米孪晶体的硬度甚至超过了金刚石。同时，立方氮化硼具有比金刚石更好的热稳定性和化学稳定性。对于超硬材料，细化晶粒是提高硬度的有效手段。研究表明立方氮化硼的硬度与粒径在几个纳米尺度仍然遵循霍尔佩奇关系。激光液相烧蚀法是一种制备纳米材料的优异手段，研究人员利用激光液相烧蚀法制备了很多其他方法很难得到的新颖的结构以及亚稳相材料。氨硼烷是一种重要的储氢材料，其完全脱氢后的产物为氮化硼。本项目提出采用脉冲激光诱导氨硼烷分解制备立方氮化硼量子点的设想，得到了前期实验结果的支持。围绕这一设想，本项目从理论计算和实验研究两方面系统设计了研究方案，深入研究激光诱导氨硼烷的脱氢机理及立方氮化硼的形成机理，调查激光诱导储氢材料脱氢的普适性，研究粒径对氮化硼物相的影响，为构建氮化硼的温度压力相图提供实验依据。

立方氮化硼作为一种超硬材料，具有远高于金刚石的氧化温度（1500℃）和较大的禁带宽度，在高精度切割和深紫外吸收和发光等领域具有广泛的应用前景。但是目前立方氮化硼的制备方法都具有较大的局限性，并且立方氮化硼纳米晶的光学性能还未见报道。本项目首先采用激光液相烧蚀的方法，制备了立方氮化硼量子点，揭示了激光诱导立方氮化硼的形成机理，并测试了光吸收性能；其次，本项目系统研究了C、O掺杂的BN的发光性能，通过调控不同C、O的含量及金属离子类型，获得了不同发光波长的BN。此外，通过激光辐照调控了BN的C、O掺杂量，系统研究了激光能量、辐照时间等与缺陷的关系，获得了具有导电性的BN，并将其用在电催化领域，获得了良好的催化性能。