NMR study on the formation mechanism of β-SiAlON from zeolite by nitridation using ammonia gas

Abstract

β-SiAlON was synthesized from a zeolite by NH₃ gas nitridation and its formation mechanism was investigated using X-ray diffraction and ²⁹Si and ²⁷Al NMR spectroscopy. It was revealed that most of the Si and Al atoms react to form β-SiAlON via amorphous forms of Si-Al-O-N and O-SiAlON. Nitridation using NH₃ gas is an effective means of preventing mullite formation and promoting the introduction of nitrogen into aluminosilicate materials at lower temperatures than temperatures required by the carbothermal reduction nitridation process. Further, the NMR spectra showed that the siliceous part of the system changed into low z-value of Si_6-zAl_zO_zN_8-z (β-SiAlON) and the incorporation of Al components into the β-SiAlON was promoted in the later stages of the reaction.