On the oxidation kinetics of an Si{sub 2}N{sub 2}O-ZrO{sub 2} composite material

The oxidation kinetics of a porous Si{sub 2}N{sub 2}O-ZrO{sub 2} composite material are investigated. Samples were oxidized at different temperatures between 1,000 and 1,450 C. Transmission electron microscopy was used for investigations of the formed oxide layer. Samples of pure Si{sub 2}N{sub 2}O and reaction couples of ZrO{sub 2}/SiO{sub 2} were prepared by a thin-film technique and heat-treated at 1,250 and 1,350 C, respectively. The thickness of the formed reaction layers was determined by spectroscopic ellipsometry. The formation of amorphous silica on Si{sub 2}N{sub 2}O was found to be faster than on Si, and this may have significant impact on the oxidation rate of the composite material. At 1,350 C, ZrSiO{sub 4} starts to form considerably in the ZrO{sub 2}/SiO{sub 2} reaction couple and may retard further oxidation in the composite material. At 1,350 C, ZrSiO{sub 4} starts to form considerably in the ZrO{sub 2}/SiO{sub 2} reaction couple and may retard further oxidation in the composite material. This process is favored at higher temperatures.