Ultra High Temperature Ceramics for Aeropropulsion and Aerospace Use

摘要

This report results from a contract tasking University of Seville as follows: The poor oxidation resistance of UHTCs is the predominant factor limiting their applicability to aerospace applications. The purpose of this study is to perform an extensive research of these materials under conditions representative of propulsion environments, that will lead to an understanding of process that will improve these materials performance. The initial materials to be studied will be ZrB2 plus 20 vol.% SiC (abbreviated as ZS), ZrB2 plus 14 vol.% SiC plus 30 vol.% C (ZSC), and SCS-9a SiC fiber reinforced ZrB2 plus 20 vol.% SiC (ZSS). The PI proposes a program with four broad, integrated objectives to be pursued each one with the others feed-back. These objectives are: 1.Determination of the mechanical behavior of these Ultra High Temperature Ceramics by compression tests. It must be noted that there is no data under these solicitation conditions in the literature. The knowledge of the dependence of mechanical properties with stress, temperature and time at temperature will be expressed as a phenomenological equation, that will allow the mechanical behavior prediction in other conditions. 2.Study in depth of the as-fabricated materials microstructure, and its evolution after mechanical tests, using a wide variety of characterization techniques. Determination of the optimal microstructure to minimize residual stresses. 3.Understanding of the correlation between microstructure, properties and thermal history. 4.Modifications on the fabrication process will be suggested, at the end of this one year period, to further improve the UHTC properties.