Preparation and properties of a γ-Al2O3 washcoat deposited on a ceramic honeycomb

Washcoat deposited on ceramic honeycomb was prepared using pseudoboehmite, the CeO₂–ZrO₂–La₂O₃ solid solution, pore enlarger and other additives. The microstructures and surface performances of washcoat/honeycomb were investigated by SEM, BET surface area, XRD, ultrasonic vibration and hot shock simulation. The results show that the performance and loading of washcoat are affected obviously by the properties of slurry gel, such as the apparent viscosity, solid content, particle size and its distribution. When the apparent viscosity of slurry is lower, the gel with a narrow particle size distribution and finer particles can be obtained, with which the coating having an excellent performance can be prepared. Adding a small quantity of the CeO₂–ZrO₂–La₂O₃ solid solution can promote the thermal stability of washcoat, such as, after calcined at 1000 °C for 5 h the sample exhibits mainly the γ-Al₂O₃ phases and the θ-Al₂O₃ -Al₂O₃ and κ-Al₂O₃ phases have not been detected in the XRD spectra. It is found also that the washcoat prepared has excellent properties of the vibration-resistant, heat-resistant and its BET surface area reaches 50 m²/g.