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

An alumina-titania coating and an alumina composite coating was deposited o n 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), s canning 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 comparat ively optimized in three kinds of samples. Due to the high-temperature stab ilizers of CeO2, La2O3, SiO2, and ZrO2, its surface phase was mainly compos ed of gamma -Al2O3 with some alpha -Al2O3. With a large number of nanoscale particles stacked on the honeycomb framework, this complex structure provi ded a firmer cohesive ability between the alumina composite sprayed coating and metal support, as well as a much higher resistance to mechanical vibra tion and thermal shock than the dipped coating. Moreover, it was supplied w ith a high geometric specific surface area of 32.1 m(2)/g. Thus, it has gre at possibilities for the alumina composite sprayed coating deposited by pla sma spraying to be used directly as a washcoat of metal-supported catalysts on controlling motorcycle exhaust gas emission. (C) 2001 Elsevier Science B.V. All rights reserved.