Articles - Microstructural study of a discoloration process during in reaction bonding of silicon nitride
- Kwan-ho Koa, Kook-soo Banga, Kwon-taek Limb, Dong-soo Parkc, Hai-doo Kimd and Chan Parka,*
- a Division of Materials Science & Engineering, Pukyong National University, Busan 608-739, Korea b Division of image Science and Engineering, Pukyong National University, Busan 608-739, Korea c Department of Future Technology, Korea Institute of Machinery and Materials, Chang-Won 641-010, Koea d Powder Materials Research Center, Korea Institute of Machinery and Materials, Chang-Won 641-010, Korea
Abstract
An inhomogeneous coloration near the surface area of a RBSN (Reaction Bonded Silicon Nitride) sample proceeded due to an interaction between the gas atmosphere and silicon nitride. This unwanted non-uniform band formation of alpha silicon nitride was controlled using a graphite crucible, which resulted in a lower nitrogen partial pressure in the atmosphere. The reduced nitrogen partial pressure improved the nitridation rate up to 99% and successfully removed the grey coloration. By varying the nitrogen partial pressure in the atmosphere, a physical explanation for the discoloration in the grey-colored area could be given.
Keywords: RBSN; nitridation; band formation; coloration
This Article
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