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Vol.32, No.7, 815 ~ 824, 1994
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| Title |
| Fabrication of Molybdenum Disilicide by Self - Propagating High - temperature Synthesis |
| 심건주Gun Joo Shim, 장대규Dae Kyu Jang, 서창열Chang Youl Suh, 김원백Won Baek Kim, 조통래Ton Grae Cho |
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| Abstract |
| MoSi₂ powders were prepared by the SHS (Self-Propagating High-Temperature Synthesis) Method. The measured reaction temperatures varied from 1600K to 1900K, while the reaction rate varied from 1 to 4 ㎜/sec. More than 50% of major metallic impurities were removed through evaporation during the high-temperature synthesis. The reaction temperature and rate were the highest when the precursor Mo and Si powders were mixed at the stoichiometric ratio(Si/Mo=2). At this composition, the measured temperature at the reaction front was 1853K, slightly lower than the theoretical adiabatic temperature, 1900K. The small discrepancy indicates that the reaction is close to adiabatic but not perfectly so. When the precursor powders contained either Mo or Si in excess, both the reaction temperature and rate were found to decrease, with the decreasing rate steeper in Si-rich composition than in Mo-rich one. the difference was explained in terms of the amounts of MoSi₂ at each composition. The reaction rate increased with the apparent bulk density and decreased with the particle size. The apparent activation energy for the reaction was found to be 40±3 ㎉/㏖. This value corresponds to the activation energy of 43 ㎉/㏖ calculated from the growth of Mo_5Si₃ in Mo_5Si₂-Mo diffusion couple. The interdiffusion of Mo and Si through MoSi₂ controls the synthesis reaction. |
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