9.1 INTRODUCTION TO THE JOINING OF CERAMICS, GLASSES, AND GLASS CERAMICS

Ceramics, inorganic glasses, and glass-ceramics comprise what are known collectively as "ceramic materials." Ceramics are crystalline and are generally harder, stronger (especially in compression), stiffer, and higher melting than metals, but are generally electrically and thermally insulating and are far less ductile and tough; in fact, they are generally brittle. Most are also generally much more resistant to chemical attack. Inorganic glasses derived from or related to ceramics exhibit generally similar properties to ceramics but usually exhibit quite different optical properties, being transparent to light, in most cases. Glass-ceramics, being crystalline materials created from amorphous inorganic glasses by thermal treatments known as "devitrification," are more like ceramics than glasses.

Many of the properties that make ceramics and glasses attractive for certain functionally-specific properties and for harsh operating environments render them difficult to process into large and/or complex shapes (see Sections 9.2 and 9.5). To produce parts with sizes or shape complexity that exceeds the limits of available processing methods, joining of smaller, less complex parts becomes especially important. Furthermore, while attractive for their special physical, electrical, thermal, optical, and chemical properties compared to metals, ceramics and glasses often need to be combined with metals in devices or structures where structural integrity is important. Thus, joining of dissimilar combinations of ceramics or glasses with metals is particularly important.

The requirements imposed on joints in ceramic materials vary with the application but include one or more of (1) hermeticity ^[1];