Vacuum Thermionic Energy Conversion Based on Nanocrystalline Diamond Films

Abstract:

Vacuum thermionic energy conversion achieves direct conversion of heat into electrical energy. The process involves thermionic electron emission from a hot surface and collection of the electrons on a cold surface where the two surfaces are separated by a small vacuum gap. Results are presented which indicate that nanocrystalline diamond films could lead to highly efficient thermionic energy conversion at temperatures less that 700°C. A critical element of the process is obtaining a stable, low work function surface for thermionic emission. Results are presented which establish that N-doped diamond films with a negative electron affinity can exhibit a barrier to emission of less than 1.6 eV. Films can be deposited onto field enhancing structures to achieve an even lower effective work function. Alternatively, nanocrystalline diamond films prepared with S doping exhibit field enhanced thermionic emission and an effective work function of ~1.9 eV. The field enhanced structures can reduce the effect of space charge and allow a larger vacuum gap. The possibility of a low temperature nanocrystalline diamond based thermionic energy conversion system is presented.

• Periodical: Advances in Science and Technology (Volume 48)
• Pages: 83-92
• DOI: https://doi.org/10.4028/www.scientific.net/AST.48.83
• Online since: October 2006
• Authors: F.A.M. Koeck, J.M. Garguillo, John R. Smith, Y.J. Tang, G.L. Bilbro, Robert J. Nemanich
• Keywords: Energy Conversion, Nanocrystalline Diamond, Thermionic Emission

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