Fundamental Aspects of Hard Ceramics

This chapter is an overview of the fundamental aspects of hard ceramics. Following an introduction to bonding and crystal structure of ceramics, an outline on processing directed particularly to near-net shaping techniques is given. High-temperature consolidation techniques discussed include surface and bulk transport processes, mechanisms of densification in solid state, liquid-phase sintering, and pressure-assisted sintering. Since microstructure strongly influences the mechanical properties, principally strength, fracture resistance, and hardness are specifically discussed. Additionally some examples of hard ceramics including silicon nitride, silicon carbide and borides are illustrated.