Development of a Commercial Process for the Production of Silicon Carbide Fibrils - Draft Phase II Final Report

Nixdorf, RD

Oak Ridge National Laboratory

关键词: 25 Energy Storage;    Aluminium;    Heating;    Hydrochloric Acid;    Scanning Electron Microscopy;   

DOI  :  10.2172/814172
RP-ID  :  ORNL/SUB/98-SU604/02
RP-ID  :  AC05-00OR22725
RP-ID  :  814172

美国|英语

来源: UNT Digital Library

【 摘 要 】

The current work continues a project completed in 1999 by ReMaxCo Technologies in which a novel, microwave based, VLS Silicon Carbide Fibrils concept was verified. This project continues the process development of a pilot scale commercial reactor. Success will lead to sufficient quantities of fibrils to expand work by ORNL and others on heat exchanger tube development. A semi-continuous, microwave heated, vacuum reactor was designed, fabricated and tested in these experiments. Cylindrical aluminum oxide reaction boats are coated, on the inner surface, with a catalyst and placed into the reactor under a light vacuum. A series of reaction boats are then moved, one at a time, through the reactor. Each boat is first preheated with resistance heaters to 850 C to 900 C. Each reaction boat is then moved, in turn, to the microwave heated section. The catalyst is heated to the required temperature of 1200 C to 1300 C while a mixture of MTS (methyl trichlorosilane) and hydrogen are introduced into the annulus of the boat. The MTS is dissociated to allow the carbon and silicon components to be dissolved into the catalyst. The catalyst saturates and precipitates silicon carbide onto the surface of the reaction boat to grow the Fibrils. The reaction continues as long as the MTS is introduced into the reactor. The major obstacle that had to be overcome during this project was the performance of the reactor. The original design of the reactor focused the microwaves in such a manner that they missed the catalyst/Fibrils growth zone. The microwaves did react with the insulation and the reactor was heated by heating the insulation. Modifications were made to the reactor to focus the microwaves on the catalyst. SiC Fibrils were produced using both MTS and Starfire SP4000 as feed-gas precursors. Both precursors produced fibrils at temperatures of less than 1000 C. The new Starfire SP4000 produced fibrils as low as 800 C, without the use of hydrogen and without producing the hazardous hydrochloric acid. Experimental results and scanning electron microscopy of the Fibril products are presented. Future work to improve on these results is discussed.