| The Effect of Si3N4 Addition on Nitriding and Post-Sintering Behavior of Silicon Powder Mixtures |
| Young-Jo Park, Jae-Woong Ko, Jae-Wook Lee, Hai-Doo Kim |
| Engineering Ceramics Research Group, Korea Institute of Materials Science |
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| ABSTRACT |
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Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with $Si_3N_4$ content, while the highest extent of nitridation was measured in $Si_3N_4$-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the $Si_3N_4$-free specimen. On the other hand, pores from the decomposed pore former were retained in the $Si_3N_4$-added specimen. Introduction of small $Si_3N_4$ particles ($d_{50}=0.3{mu}m$) into a powder compact consisting of large silicon particles ($d_{50}=7{mu}m$) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to $Si_3N_4$ size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body. |
| Key words:
Reaction bonding, Silicon nitride, Porous, Diluents |
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