Low Temperature Thermally Activated CVD of Silicon on Molybdenum for Oxidation Protection

The United States Global Threat Reeducation Initiative (GTRI) is promoting the production of molybdenum-99 without the use of uranium-235. One possible route, called neutron capture technology, is through the activation of molybdenum-98 via irradiation. GE-Hitachi has identified a location within their boiling water reactors for molybdenum-98 irradiation, but the elevated temperatures present risk oxidizing the molybdenum. This work explored using a silicon coating to protect the molybdenum from oxidation. With silane gas as the precursor, chemical vapor deposition was employed to produce the silicon coating. Characterization was performed and showed a discrete silicon layer was deposited with little to no inter-diffusion occurring between the coating and the substrate. Oxidation performance was evaluated, and excellent results were observed with the silicon coated specimen having weight gain 3 orders of magnitude less than that of the bare molybdenum.