Taisuke Tanaka*, Xiaobao Fan, Takamasa Ishigaki and Gervais Soucy#

*Nisshin Flour Milling Co., Ltd. 5-3-1, Tsurugaoka, Oi-machi, Saitama 356-0045, Japan
ttanaka@nirim.go.jp

National Institute for Research in Inorganic Materials
1-1, Namiki, Tsukuba-shi, Ibaraki 305-0044, Japan

#Plasma Technology Research Center, University of Sherbrooke
Sherbrooke, Quebec, Canada J1K 2R1

The in-flight compositional modification of boron carbide (BxC; x=4~10.4) powder was carried out in an R.F. induction plasma of Ar-H2, Ar-N2 or Ar-H2-NH3. Reactor pressure, powder feed rate and plate power level were taken as the experimental parameters to alter the thermal history of the injected powder particles. In scanning electron microscopic study, the trace of crystal growth from melt and formation of fine powder were observed in all plasma-treated BxC. In all plasma-treated BxC, the carbon contents was lower than that of raw one (17.0 wt%), 16.2-16.8 and 15.5-16.7 wt% in Ar-H2, and Ar-N2 or Ar-H2-NH3 plasma-treated BxC, respectively. The formation of boron and the decrease of cell volume on BxC were shown in powder X-ray diffraction study of Ar-H2 plasma-treated powder. The boron, which was a kind of boron polytypes, has a doubled a length in comparison with BxC rombohedral cell. On the other hand, the remarkable change in profile intensity of rombohedral BxC, as well as the formation of boron, were observed in those study of Ar-N2 or Ar-H2-NH3 plasma-treated one, while there was no change in Ar-H2 plasma-treated one. The change suggested the structural modification on BxC in Ar-N2 and Ar-H2-NH3 plasma treatment. Also, thermodynamical consideration was carried out to explain the experimental results.