Ultra-refractory ceramic composites of composition ZrB2 + (5 to 20) vol% MoSi2were produced by pressureless sintering at 1830 °C under argon atmosphere.Sintering cycles and microstructural analysis point out that at least 20 vol% molybdenum disilicide is necessary for obtaining a dense material. Thereafter, the composite 80 vol% ZrB2 + 20 vol% MoSi2 was used to test the thermal stabilityunder oxidizing environment. Oxidation tests were carried out in flowing syntheticair in a thermogravimetric analyzer from 700 to 1400 °C with exposure time of30 h. In the low-temperature range (700–1000 °C), the oxidation of the composite resembles that of monolithic ZrB2 ceramics, for temperatures >1200 °C the silica resulting from oxidation of molybdenum disilicide seals the sample surface, preventing zirconium diboride from fast degradation.
To improve mechanical properties of mullite, a mullite-Al2O3\mullite laminate composite
was prepared. Lamination generates residual stresses within the structure, measured by piezospectroscopy.
A preliminary and complete piezo-spectroscopic characterization of the Al2O3\mullite
system was carried out. A method to determine the concentration of Al2O3 in the composite by
Raman spectrum was proposed and used to assess the composition of the laminated structure along
the cross section. The experimental results evidenced a gradual change of composition and residual
stress state between the two layer.
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