窒化けい素の湿式微粉砕におけるメカノケミストリー

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  • Mechanochemistry on Wet Fine Grinding of Silicon Nitride Powder
  • チッカ ケイソ ノ シッシキ ビフンサイ ニ オケル メカノケミストリー

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Silicon nitride powders such as amorphous, α- and β-Si3N4 were ground by a vibration ball mill, a pot and balls of which were made of silicon nitride, in methanol medium containing various concentrations of water, and the mechanochemical activation (the amount of ammonia formation, the variation of specific surface area of the ground powders and the relative crystallinity) has been investigated.<BR>Silicon nitride powders were activated by fine grinding and ammonia was produced by the presence of water contained in methanol. The amount of formed ammonia increased with an increase of grinding time and was closely related to the concentration of water contained in methanol. Reaction rate was expressed as r=k[CH2O ][Csite (t)]7 (n>1) under some assumption. The activity sequence per unit specific surface area of three types of silicon nitride for this reaction was amorphous> α-> β-Si3N4. The specific surface area of ground powders decreased with an increase of hydrated ratio, and the rate of decrease was in the following order: amorphous> α-> β-Si3N4. This sequence corresponded to that of amount of formed ammonia. Infrared spectra of treated powders revealed that the surface layer of Si3N4 was changed into SiO2. In the case of grinding in the medium of purified methanol free from water, the specific surface area of ground powders increased with an increase of grinding time, and the rate of increase was as follows: α-> β->amorphous Si3N4. The relative crystallinity(It) for α-and β-Si3N4 decreased by grinding and an enlargement of lattice distance (d) was observed.

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