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Combustion synthesis of MgSiN 2 powders and Si 3 N 4 ‐MgSiN 2 composite powders: Effects of processing parameters
Author(s) -
Xu Jingkun,
Hu Zunlan,
Han Yao,
An Di,
Xie Zhipeng
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16710
Subject(s) - sintering , composite number , whiskers , materials science , combustion , grain size , impurity , ceramic , economies of agglomeration , mineralogy , chemical engineering , nuclear chemistry , analytical chemistry (journal) , metallurgy , chemistry , composite material , organic chemistry , engineering
In the present work, high‐quality MgSiN 2 powders were prepared by a combustion synthesis method, based on Mg‐Si 3 N 4 ‐N 2 system. The effects of additive content (NH 4 Cl or NH 4 F) and N 2 pressure on phase composition and crystal morphology of products were investigated. The results suggested that both NH 4 Cl and NH 4 F additives alleviated agglomeration and decreased the grain size of MgSiN 2 . In addition, NH 4 Cl did not result in the formation of an extra impurity, while MgF 2 residue was found when NH 4 F was introduced. Therefore, NH 4 Cl additive was considered as a better choice for the preparation of MgSiN 2 powders in comparison with NH 4 F additive. According to the observation of some MgSiN 2 whiskers and notably increased Si content under low N 2 pressure, the pressure of N 2 over 0.5 MPa was essential to have a complete reaction in the present work. Finally, MgSiN 2 ‐Si 3 N 4 composite powders with quasi‐spherical morphology were prepared by adding excessive Si 3 N 4 and NH 4 Cl additive in reactant. The formation and growth mechanism of MgSiN 2 grains was reasonably speculated based on the experimental results. Because of the remarkable merits, the as‐prepared Si 3 N 4 ‐MgSiN 2 composite powders showed great potential for alternative sintering aid in the sintering of Si 3 N 4 ‐based ceramics.