Near-Net-Shape Ceramics by Reactive Processing

Abstract

Since conventional production of high-temperature materials involves high investments and costly consumption of both energy and time, reaction engineering methodology combined with near-net shaping is often the answer to problems associated with the fabrication of advanced materials. Over the last decades, the number of different reaction–based processing methods for near-net-shaped ceramics has gradually increased. In this review, different reactive processing techniques and their potential for near-netshaping are treated, e.g. SHTS (self-supporting high temperature synthesis), the Lanxide method DIMEX®, reaction bonding (RB), reactive processing of Alumina-Aluminide Alloys (3A) and Al2O3-Al alloyed metal composites (3AMC). In addition to their potential for near-net shaping, other advantages to reactive processing routes are recognized to be reduced processing temperatures, reduced glassy phase formation at the grain boundaries, fine grained microstructures and improved mechanical strength. Since the exothermic reactions constitute the base for reactive processing of high quality materials in an economic way, control of these reactions is essential. The process flows are described together with characteristic features of process and materials. In addition, specific aspects of reaction-based synthesis will be illustrated with examples from own work in the area of reaction bonding of silicon nitride and alumina.