Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1615213 | Journal of Alloys and Compounds | 2013 | 9 Pages |
In this paper, the direct nitridation of Al powder was carried out under N2 and NH3 atmosphere in temperature range from 900 to 1400 °C, respectively. The structures, morphologies and compositions of the products were measured and analyzed by XRD, SEM and EDX. The SEM results showed core–shell structures of Al/AlN below 900 °C under N2 atmosphere, whereas tadpole-like and branches structures of AlN over 1200 °C under NH3 atmosphere. EDX results demonstrated that Al-rich AlN with extensive N/Al ratio could form in the direct nitridation process. The XRD results indicated that the pure AlN powders were obtained at 1400 °C under N2 atmosphere and at 1100 °C under NH3 atmosphere, respectively. The reaction analysis revealed that intensive passivation effect of Al occurred below 900 °C under NH3 atmosphere and hindered the nitridation, while the passivation effect was eliminated beyond 1000 °C and nitridation was boosted. In contrast, Al crust formed below 1100 °C under N2 atmosphere and ceased the nitridation, while the crust became unstable because of convection originated from intensive evaporation beyond 1200 °C and the nitridation was accelerated. So the reaction process played essential roles in preparing pure AlN by the direct nitridation of Al powder.
► Core-shell structures of Al/AlN, and tadpole-like structures of AlN are produced. ► Fully nitridation temperature using NH3 is 300 °C lower than that using N2. ► The molten Al layer and passivation effect are major resistances for nitridation. ► Al-rich AlN with extensive Al/N ratio could form in the direct nitridation process.