Structure and performance of γ-alumina washcoat deposited by plasma spraying

An alumina–titania coating and an alumina composite coating was deposited on a FeCrAl metal support as a washcoat by a plasma spraying technique, and an alumina-dipped coating was prepared for comparison. The microstructures and performances of the coatings were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), the Brunauer–Emmett–Teller method (BET), as well as an ultrasonic vibration simulation. The results showed that the combined properties of the alumina composite sprayed coating were comparatively optimized in three kinds of samples. Due to the high-temperature stabilizers of CeO2, La2O3, SiO2 and ZrO2, its surface phase was mainly composed of γ-Al2O3 with some α-Al2O3. With a large number of nanoscale particles stacked on the honeycomb framework, this complex structure provided a firmer cohesive ability between the alumina composite sprayed coating and metal support, as well as a much higher resistance to mechanical vibration and thermal shock than the dipped coating. Moreover, it was supplied with a high geometric specific surface area of 32.1 m2/g. Thus, it has great possibilities for the alumina composite sprayed coating deposited by plasma spraying to be used directly as a washcoat of metal-supported catalysts on controlling motorcycle exhaust gas emission.