Synthesis of β-SiAlON-AlN-Polytypoid Ceramics from Aluminum Dross

Abstract

Aluminum dross is one of the main secondary wastes during aluminum recycling procedure. It is utilized to synthesize β-SiAlON-AlN-polytypoid ceramics by the reduction-nitridation method in this paper. The effects of the reaction parameters, such as the Si/Al ratio, reaction temperature and holding time are studied in detail. The results indicate that the synthesized products are mainly composed of β-SiAlON and Mg-AlN-polytypoid at 1450°C to 1650°C for 6 h. As the Si/Al ratio changes from 1.0 to 2.5, the amount of β-SiAlON increases while the amount of Mg-AlN-polytypoid decreases. At 1750°C, the samples consist mainly of AlN and AlN-polytypoid because SiO gas is significantly evaporated. With the increment of synthesis temperature, the growth of elongated Mg-AlN-polytypoid grains is significantly accelerated. SEM and EDS analysis results for the samples formed at 1650°C for 6 h show that the β-SiAlON grains display a short platelet morphology, and Mg-AlN- polytypoid grains possess needle or lath morphology. This study suggests that it is possible to synthesize the low cost SiAlON ceramics with high toughness from aluminum dross.