Experimental Investigation of the Oxidation Behavior of SiSiC Foams

Mach, FRA and Von Issendorff, Franz and Delgado, Antonio and Ortona, Alberto (2008) Experimental Investigation of the Oxidation Behavior of SiSiC Foams. Ceramic Engineering and Science Proceedings, 29 (7). pp. 299-311. ISSN 1940-6339

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Abstract

In porous medium burners, the combustion is stabilised within the cavities of an open porous ceramic structure. The ceramics used are exposed to unique thermal and mechanical stresses. sharp temperature gradients and corrosive high-temperature environments during porous burner operation. Silicon-infiltrated silicon carbide (SiSiC) ceramic foams are used due to their excellent hightemperature stability and oxidation resistance by forming a protective silica scale. Despite their high chemical stability. they are susceptible to different oxidation routes. The present stud) was aimed OJI assessiiig the oxidation processes of SiSiC ceramic foams since no data are available for this material under the given conditions. Studies on oxidation fall into two main categories: laboratory furnace and burner rig studies. The investigation can further be divided into isothermal oxidation and cyclic oxidation. Isothermal oxidation focuses on the mechanisms of scale growth and oxidation rates. With cyclic oxidation. the durability is investigated. The oxidation parameters of SiSiC ceramic foams during isothermal oxidation in a furnace and the cyclic oxidation in a porous burner test rig were determined. This includes the determination of oxidation rates and the effect of changing the oxygen partial pressure. The oxidation rates of the SiSiC foams are higher than that o f chemically vapour deposited S i c (CVDSiC). By decreasing the oxygen concentration the transition from passive to active oxidation starts at lower temperatures. In cyclic oxidation the ceramic foams show a generic mass change behaviour which can be predicted on the basis of crack test results and can be correlated with the lifetime of the ceramic foams.

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