250

200 400 600 800 1000 1200 1400 Temperature (°C)

FIGURE 2.2 Silicon nitride ceramics strength improvements [2].

temperatures also has been improved, as shown in Figure 2.2 for silicon nitride materials. SiC ceramics retain strength to even higher temperatures.

One of the most significant advances in ceramics during the past 20 years has been to increase fracture toughness. Increased fracture toughness is important to industry because it reduces risk of fracture during installation and service, a risk that has always been a concern with glass and traditional ceramics. Figure 2.3 compares the toughness of some of the new ceramic materials with typical ceramics and other key engineering materials. Glass has fracture toughness of about 1 MPa ■ m1/2, and conventional ceramics range from about 2-3 MPa ■ m1/2. Steel

New Ceramics and Ceramic Matrix Composites Exhibit Increased Toughness

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