基于金刚石与立方氮化硼薄膜的高效热电子发射机理研究

Thermionic power generation employs thermionic emission of electrons from material surfaces to convert thermal energy directly to electric energy, and the conversion process is clean and environmentally benign, which makes it an important research topic in the development of novel renewable energy sources. However, due to their limited power capacity, bulky and complex design, and high operating temperature, the conventional metal-based thermionic devices have not met the requirements of commercial applications. The development of new thermionic materials with superior characteristics is believed the key in the further advances of thermionic technology. As proposed in this project, diamond and cubic boron nitride (cBN) are materials with negative electron affinity (NEA) which enables electron emission at reduced temperatures. Moreover, both diamond and cBN have extremely high thermal and chemical stabilities, high radiation resistance and excellent thermal conductivity, which make them very promising materials for the highly durable thermionic device applications.In this proposal, the work functions of diamond and cBN films will be tuned by doping; the dependence of turn-on temperature and current density on the surface modification, surface nanostructuring and light irradiation processes of diamond and cBN electrodes will be investigated systematically; and the thermionic emission and enhancement mechanisms will be explored. The prototypes of thermionic devices utilizing diamond and cBN film electrodes will be constructed, and the influences of device configuration on power conversion efficiency and output power will be studied. The implementation of the proposed project will provide theoretical fundamentals and technological guidelines for designing and manufacturing new thermionic energy conversion devices, and promote their practical applications.

热电子发电技术利用材料表面的热电子发射将热能直接转化为电能，发电过程清洁环保，是新型可再生能源领域的重要研究方向。然而，传统的金属基热电子发电器件发电容量小，所需工作温度极高，结构复杂、体积庞大，难以推广应用。高性能材料的开发是热电子发电技术发展的关键问题。在本项目的研究中，金刚石及立方氮化硼（cBN）具有负的电子亲和势，可在较低温实现电子发射。同时，其耐高温、抗辐射、耐腐蚀、高热导等特性也有助于器件长期稳定的工作，是较理想的热电子发射材料。实验中我们将利用掺杂的方法调控材料的功函数，并系统地研究材料表面改性、表面纳米化及光辐射等因素对电子发射温度及电流密度的影响，阐明热电子发射及增强机理。我们也将研制基于金刚石及cBN薄膜的热电子发射原型器件，探讨器件结构与能量转换效率及输出功率的关系。本项目的实施可以为新型热电子发电器件的设计与制造提供理论支持及技术路线，并促进其在新能源领域的应用。

热电子发电是利用材料表面的热电子发射将热能直接转化为电能，是新型的可再生能源技术。金刚石和立方氮化硼（cBN）具有负电子亲和势、高热导、耐高温、抗辐射、耐腐蚀等特性，是理想的低温高效热电子发射材料。由于传统的金属基热电子发电器发电容量小、工作温度高、结构复杂，难以推广应用，本项目提出研究开发金刚石和cBN的热电子发射性能，以纳米技术提升发射效率，探讨发射机理以及实现高效热电子发射的关键技术。..本项目采用CVD技术制备了高质量金刚石和cBN薄膜，利用等离子体刻蚀在表面构造了多种纳米阵列，并进行表面改性。采用电场辅助电子发射系统，深入研究了它们的电子发射性能与温度、纳米结构形貌、表面改性的关系，讨论并初步明确了发射机理，揭示了其高效热电子发射特性，展现出金刚石和cBN在热电子发电器件中的应用前景，为新型热电子发电器件的设计和开发提供了理论及实验依据。项目成果将促进热电子发电在新能源领域的发展，有助于舒缓能源危机，处理及利用废热，保护环境，实现特殊环境下的能源需求。本项目的研究还表明，金刚石表面纳米阵列的在电化学、药物输运及抗菌应用中也有优良表现。..研究中取得并报道了多项创新性成果，在Chemical Society Reviews、Advanced Materials、Advanced Energy Materials、Advanced Functional Materials、Chemical Communications、ACS Applied Materials & Interfaces、Journal of Materials Chemistry A、NPG Asia Materials、Small、Nano Research、Applied Physics Letters、Scientific Reports等主要国际期刊上发表论文23篇。