Optimization of time-temperature schedule for nitridation of silicon compact on the basis of silicon and nitrogen reaction kinetics |
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Authors: | J Rakshit P K Das |
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Affiliation: | (1) Central Glass and Ceramic Research Institute, 700 032 Jadavpur, Calcutta, India |
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Abstract: | A time-temperature schedule for formation of silicon-nitride by direct nitridation of silicon compact was optimized by kinetic
study of the reaction, 3Si + 2N2 = Si3N4 at four different temperatures (1250°C, 1300°C, 1350°C and 1400°C). From kinetic study, three different temperature schedules
were selected each of duration 20 h in the temperature range 1250°-1450°C, for complete nitridation. Theoretically full nitridation
(100% i.e. 66.7% weight gain) was not achieved in the product having no unreacted silicon in the matrix, because impurities
in Si powder and loss of material during nitridation would result in 5–10% reduction of weight gain.
Green compact of density < 66% was fully nitrided by any one of the three schedules. For compact of density > 66%, the nitridation
schedule was maneuvered for complete nitridation. Iron promotes nitridation reaction. Higher weight loss during nitridation
of iron doped compact is the main cause of lower nitridation gain compared to undoped compact in the same firing schedule.
Iron also enhances the amount of Β-Si3N4 phase by formation of low melting FeSix phase. |
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Keywords: | Reaction sintered silicon nitride nitridation reaction kinetics |
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