Materials for engineering, 3rd Edition - (Malestrom)

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Materials for engineering
Table 4.3 Properties of some engineering ceramics
Property Units Alumina Zirconia Silicon Silicon
nitride carbide
(RBSN) (RSSC)
Modulus of rupture MPa 300–400 200–500 200–350 450
Compressive strength MPa 3000 2000 2000 2000
Young’s modulus GPa 380 138 150–180 400
Thermal expansion 10 –6 K –1 8.5 8 2.6 4.5
coefficient
Thermal conductivity W m –1 K –1 25.6 1.5 12.5 100
Toughness (G c ) Jm –2 25 80 10 25
of typical strengths, but test data from current suppliers should be used for
analytical design or life prediction calculations.
4.3.2 Alumina
Many hundreds of tons of alumina (Al 2 O 3 ) powder is produced annually
from the mineral bauxite and used in the manufacture of porcelain, crucibles,
wear-resistant parts such as cutting tools and grinding wheels, medical
components and a variety of other components. It forms ionic crystals of
hexagonal structure, Fig. 4.4, with close-packed layers of oxygen ions, with
the Al 3+ ions occupying interstices such that each is surrounded by six O 2–
+
Empty hole
Al 3–
+
O 2
4.4 Crystal structure of alumina.