Solid-state NMR study of crystallizing process of silicon nitride powder synthesized by the thermal decomposition method of imide

Our recent investigation established a method for quantifying the amount of amorphous silicon nitride by Si-29 MAS NMR technique, which involved the f ull relaxation of the Si-29 nuclear spin system between pulses in order to make the signals proportional to the number of nuclei in each phase, In thi s work, solid-state NF;IR study of the crystallizing behavior of silicon ni tride powder, synthesized by the thermal decomposition method of imide, has been attempted, Because the crystalline and amorphous phases of Si3N4 have different thermal expansion and oxidation susceptibilities, this differenc e strongly affects sinterability and the mechanical properties of the final sintered body, In view of the effects of crystalline vs, non crystalline p hases on sinterability and mechanical properties, it is crucial to establis h a reliable method for measuring the quantities of alpha-, beta-, and amor phous Si3N4 in the batches of Si3N4 powder before carrying out the sinterin g process, IVloreover, because remains of hydrogenous products generally ex ist on the surface of the silicon nitride powder, this affects the characte ristic of slurry and sinterabilitly of the Si3N4 powder, Thus, the quantifi cation of the amount of hydrogenous products in the silicon nitride powder is also required, According to Si-29 MAS NMR spectra of silicon diimide (Si (NH)(2)) during thermal decomposition at a series of temperatures, the crys talline phase increased as calcination temperatures increased, The integrat ed intensities of H-1 MAS NMR spectra varied directly as specific surface a reas, The bands near 1630 and 3300 cm(-1) arising from adsorbed molecular w ater and the unknown band near 1400 cm(-1) were observed in IR spectre, Thi s result can be interpreted as indicating that there exists a proportional amount of compound consisting of hydrogen to specific surface area on the s urface of silicon nitride powder, which was measured by H-1 MAS NMR.