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A Unique Application of a Microwave Induced Plasma for Material Synthesis.

Salsman-JB; Holderfield-SP
Paper in Materials Research Society Symp Proceedings Volume 189 Mater Res Soc PP 81-86 :81-86
Research conducted at the U.S. Bureau of Mines Tuscaloosa Research Center has resulted in a process of forming tungsten carbide (wc) in a microwave induced plasma (mip). This process allows for the formation of 99.96 pct wc with a 0.04 pct free carbon content and grain sizes on the order of 0.05 Um in approximately 10 min. Commercial methods of producing wc require that a mixture of metallic tungsten and elemental carbon be heated to 1,500 deg c for up to 7 h. Therefore, the new Bureau-developed method is significantly less energy intensive, requiring only 13 pct of the energy used in conventional wc processing methods, and is less expensive, although initial capital outlay may be high. The Bureau process involves using a 915-mhz, 30-kw variable-power microwave generator to sustain a carbon monoxide plasma. The reaction chamber is constructed of a wr 975 rectangular waveguide that is short- circuited at the end. The reaction takes place inside the waveguide at an electric field maximum. After the reaction chamber is readied, the microwave generator is turned on, which ignites the plasma within seconds. In approximately 10 min. The reaction is complete, resulting in a commercially acceptable product.
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OP 244-91
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Paper in Materials Research Society Symp. Proceedings Volume 189. Mater. Res. Soc., PP. 81-86