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Yasumasa Takao, National Institute of Advanced Industrial Science and Technology (AIST)
Mutsuo Sando, Industrial Technology Center of SAGA
Synthesis of non-oxide materials includes solid-phase grinding, liquid building-up, plasma, and CVD. The raw powder of the sintered body is commercialized by solid-state synthesis; however, it is non-spherical in shape and its size is below the submicron range. We considered the changes in free energy of Al, O2, N2, NH3, liquefied petroleum gas (LPG) and focused on the reaction accelerator effect of LPG for Al nitridation or Al2O3 reduction. As a result, we found that, conceptually, some Al nitridation syntheses via LPG firing could occur. The LPG firing method can provide a gas diffusion nitridation mechanism, and can therefore produce Al-oxynitride (AlON) directly (Al powder did not convert to AlON completely), and AlN spherical powders with diameters above the submicron range.
In conclusion, we described the synthesis of non-oxide spherical powder by LPG firing.We considered the changes in free energy of Al, O2, N2, NH3 , LPGs and focused on the nitridation accelerator effect of LPG. The LPG firing method can provide AlON directly (Al powder did not convert to AlON completely), and AlN is prepared by the rapid and low-temperature transformation compared with the previous syntheses. Consequently, we found that some Al nitridation syntheses could occur via LPG firing (Fig. 1). The LPG synthesis involves the gas-diffusion mechanism, despite the gas-phase reaction. This is because this synthesis is favored to accelerate the reaction when NH3 mixing is carried out before Al heating, although the gas-phase reaction involves NH3 mixing after Al heating (Figs. 2(a–c)). Thus, the LPG synthesis can provide a spherical d-AlON spinel and AlN powder with a median diameter that is above the submicron range. (Figs. 3(b, c)). References