6 Concluding Remarks
Oxide CMCs are attractive materials because they are inherently resistant to oxidation. Efforts to develop the oxide CMCs were intensified in the last decade, relying onto these and similar high temperature properties. Previous to oxide CMCs, the non-oxide CMCs were successfully developed, mainly bearing in mind the structural applications. Recently, demanding requirements for the conditions in air were set bringing the need for better materials withstanding even higher temperatures and longer exposure times (i.e. ≥ 1200°C and >10.000 hours) than those initially given. In general, space applications entail higher temperatures (i.e. 1500°C) than those anticipated for gas turbine engines, however, hereby much shorter exposure times are required (< 5 hours) making it bearable for non-oxide CMCs. Thus, the non-oxide CMCs having relatively high ultimate fracture strengths (e.g. 300–600 MPa) found an appropriate use in space applications.
KeywordsCrystallization Pyrolysis Scheelite
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