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Preparation of Silicon Nitride Whiskers from Diatomaceous Earth: I, Reaction Conditions
Author(s) -
Mizuhara Yukako,
Noguchi Masao,
Ishihara Tatsumi,
Takita Yusaku
Publication year - 1995
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/j.1151-2916.1995.tb08368.x
Subject(s) - whiskers , yield (engineering) , silicon nitride , materials science , carbothermic reaction , whisker , earth (classical element) , silicon , mineralogy , nuclear chemistry , chemical engineering , metallurgy , chemistry , composite material , mathematics , carbide , engineering , mathematical physics
Whiskers and powder of silicon nitride were prepared by the carbothermal reduction and nitridation of diatomaceous earth in the presence of flowing N 2 and NH 3 . The optimum temperature for the formation of Si 3 N 4 whiskers was 1350°C and the yield reached almost 20% after 24 h. The α‐Si 3 N 4 content decreased with increasing nitridation temperature. Yields of the whiskers were dependent on NH 3 concentration and the total gas feed rate. The maximum yield of inside whiskers was obtained for a 25 vol% NH 3 /N 2 mixture, while the maximum quantity of outside whiskers was produced for 75 vol% NH 3 /N 2 . The sum of the yield of the inside and outside whiskers increased with decreasing total gas feed rate. However, no nitridation of SiO 2 was observed at a feed gas rate below 0.18 mmol·min −1 . The yield of the inside whiskers increased gradually with increasing reaction time up to 36 h, whereupon a constant value was attained. Although the amount of outside whiskers produced was relatively small, the quantity seemed to increase until 60 h.