Mullite based oxidation protection for SiC-C/C composites in air at temperatures up to 1900 K

Abstract For an industrial Si–SiC coated C/C material (reference material) the temperature dependence of the linear rate of mass loss is interpreted in the temperature range 773 T T 2 laser pulses (j=3·10 7 W cm −2 ) lead to melting and evaporation of the target material in a single step. Therefore the flux of the metal components is stoichiometric. Deposited green layers did not show IR peaks typical for mullite. After a short oxidation treatment (15 min at 1673 K) the formation of mullite in the coating was completed as was confirmed by IR spectroscopy and XRD investigations. Thin PLD-mullite layers (900 nm) did not markedly improve the oxidation resistance of the reference material in the high temperature range 1473 T 2 formation at the mullite–SiC interface all samples exhibited a mass increase on oxidation. The inward diffusion of oxygen across the outer mullite-containing layer controlled the kinetics of the reaction as was deduced from 18 O diffusivity measurements in PLD mullite layers. The calculated oxidation rates resulting from the diffusion parameters in SiO 2 and mullite are close to the thermogravimetric data. For oxidation durations of three days only amorphous SiO 2 is formed at the mullite–SiC interface.