Vacuum Thermionic Energy Conversion Based on Nanocrystalline Diamond Films |
| Journal |
Advances in Science and Technology (Volume 48) |
| Volume |
Diamond and Other New Carbon Materials IV |
| Edited by |
P. VINCENZINI and E. CAPPELLI |
| Pages |
83-92 |
| DOI |
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 |
| 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 700ºC. 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. |
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