固体NMRによるイミド熱分解法により合成した窒化ケイ素粉末の結晶化過程の観察

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Our recent investigation established a method for quantifying the amount of amorphous silicon nitride by ^<29>Si MAS NMR technique, which involved the full relaxation of the ^<29>Si nuclear spin system between pulses in order to make the signals proportional to the number of nuclei in each phase. In this work, solid-state NMR study of the crystallizing behavior of silicon nitride powder, synthesized by the thermal decomposition method of imide, has been attempted. Because the crystalline and amorphous phases of Si_3N_4 have different thermal expansion and oxidation susceptibilities, this difference strongly affects sinterability and the mechanical properties of the final sintered body. In view of the effects of crystalline vs. non-crystalline phases on sinterability and mechanical properties, it is crucial to establish a reliable method for measuring the quantities of α-, β-, and amorphous Si_3N_4 in the batches of Si_3N_4 powder before carrying out the sintering process. Moreover, because remains of hydrogenous products generally exist on the surface of the silicon nitride powder, this affects the characteristic of slurry and sinterability of the Si_3N_4 powder. Thus, the quantification of the amount of hydrogenous products in the silicon nitride powder is also required. According to ^<29>Si MAS NMR spectra of silicon diimide (Si(NH)_2) during thermal decomposition at a series of temperatures, the crystalline phase increased as calcination temperatures increased. The integrated intensities of ^1H MAS NMR spectra varied directly as specific surface areas. The bands near 1630 and 3300 cm^<-1> arising from adsorbed molecular water and the unknown band near 1400 cm^<-1> were observed in IR spectra. This result can be interpreted as indicating that there exists a proportional amount of compound consisting of hydrogen to specific surface area on the surface of silicon nitride powder, which was measured by ^1H MAS NMR.
社団法人日本セラミックス協会の論文
2001-02-01

固体NMRによるイミド熱分解法により合成した窒化ケイ素粉末の結晶化過程の観察

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