Zero‐Waste Progress for the Synthesis of High‐Purity β‐Sialon Ceramics from Secondary Aluminum Dross

Abstract

β‐Sialon materials are synthesized by nitriding reduction reaction using secondary aluminum dross and Si powder as the raw materials. The results indicate that the phases of products are stratified, in which the lower layer is pure β‐Sialon and the upper layer is mainly β‐Sialon, Al2O3 and spinel. This is caused by the transformation of the Si powder from solid to liquid phase and the metal oxide floating to the upper layer under the action of gravity. The aspect ratio of elongated β‐Sialon grains rapidly increases as the Si/Al ratio increases, and β‐Sialon grains finally became fibrous. Rod‐like and fluffy whiskers are observed and their growth mechanisms are the double‐stage vapor–liquid–solid mechanism at the base and vapor–solid mechanism at the tip. In the upper layers, the whiskers mainly grow on the surface and the gap, and the reactions are solid–gas reaction and gas–gas reaction, respectively.