ABSTRACT
The need for greater energy efficiency has placed increased thermal demands on materials used in advanced heat engines and other energy-consuming devices. As a consequence, a substantial research effort has been devoted to the search for high temperature structural materials that can keep pace with these engineering demands. For several years now, ceramic materials, such as silicon nitride and silicon carbide, have received the focused attention of the design community as plausible successors to the more traditional metallic alloys. The reason for this attention is shown in Fig. 5.1. The creep rupture resistance of modern grades of silicon nitride far exceeds that of the best single-crystal superalloys currently available. The potential for high tem perature use of these ceramics is apparent and their utilization in elevatedtemperature applications is evolving. Reasons for the delay in application include the high cost of producing advanced ceramics and the lack of a credible data base for these materials at elevated temperatures. Nonetheless, it is in the high-temperature world of gas turbine engines and other related aerospace applications that advanced ceramics have their greatest potential.
