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A Unique Application of a Microwave Induced Plasma for Material Synthesis

Published online by Cambridge University Press:  28 February 2011

Johanina B. Salsman  and
S. P. Holderfield
Johanina B. Salsman
Affiliation:
U. S. Bureau of Mines, Tuscaloosa Research Center, P. O. Box L, Tuscaloosa, AL 35486
S. P. Holderfield
Affiliation:
U. S. Bureau of Mines, Tuscaloosa Research Center, P. O. Box L, Tuscaloosa, AL 35486
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Abstract

Research conducted at the 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 pet WC with a 0.04 pet free carbon content and grain sizes on the order of 0.05 µm in approximately 10 minutes. Commercial methods of producing WC require that a mixture of metallic tungsten and elemental carbon be heated to temperatures of 1,500°C for up to 7 hours. 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 minutes, the reaction is complete resulting in a commercially acceptable product.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 189: Symposium L – Microwave Processing of Materials II , 1990 , 81
Copyright
Copyright © Materials Research Society 1991

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References

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