Ceramic materials components

Mikijeli B, Mangels J (2001) SRBSN Material Development For Automotive Applications. In Heinrich JG, Aldinger F (eds) Ceramic Materials Components for Engines, Wiley-VCH, Weinheim, p 393... 

Wotting G, Hennicke J, Feuer H, Thiemann KH (2001) Reliability and Reproducibility of Silicon Nitride Valves Experiences of a Field Test. In Heinrich LJ (ed) Proceedings of the 7 Conf on Ceramic Material Components for Engines, Goslar, Wiley-VCH, Weinheim... 

G. Bandyopadhyay and co-workers in J. Tennery, ed., Proc. 3rd. Int. Sjmp. on Ceramics Materials and Components for Engines, American Ceramic Society, Westerville, Ohio, 1989, p. 1397. 

FIG. 8-69 Ecc( ntric plii valve shown in erosion-resistant reverse flow direction, Shaded components can he made of hard metal or ceramic materials, Cm 1 li(isy Fislier-R/iseuimini. ... 

Uniform microstractuie is cracial to the superior performance of advanced ceramics. In a cerantic material, atoms are held in place by strong chentical bonds that ate impervious to attack by corrosive materials or heat. At the same time, these bonds are not capable of much "give." When a ceramic material is subjected to mechanical stresses, these stresses concentrate at minute imperfections in the microstmcture, initiating a crack. The stresses at the top of the crack exceed the threshold for breaking the adjacent atomic bonds, and the crack propagates throughout the material causing a catastrophic brittle failure of the ceramic body. The rehability of a ceramic component is directly related to the number and type of imperfections in its microstmcture. 

The spent fuel matrix is a ceramic material with a fascinating chemical composition and a large degree of phase heterogeneity. The physical state and chemical composition of spent fuel largely depends on the bum-up of the fuel once it is taken out of the reactor. In Fig. 6 we indicate the dependence of the chemical composition on the bum-up for a series of PWR fuels. However, the fact that remains constant is that U02 constitutes the major component of spent fuel, ranging within a total of 95-98% in weight (see Fig. 7). 

At this point, experiments must be performed. Experimental results for the erosive wear of the selected candidate ceramic materials in coal slurries are presented in Table 8.4. Notice that the wear rate has a very rough inverse correlation with which is consistent with some of the descriptions of erosive wear from the previous section. Any of these ceramic materials is suitable for the piping and pump components based solely on wear rate, with the lowest wear rate for SiC being the most attractive. Formability and economic criteria can be applied to assist in the final material selection. 

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