Two γ-Al2O3 washcoats on FeCrAl substrate were prepared by dip-coating boehmite sol gel or γ-Al2O3 slurry. The effects of coating solution on the washcoat properties were extensively studied. The washcoat morphology

crystal structure

texture and adhesion to substrate were investigated by SEM

XRD

nitrogen physic sorption and ultrasonic vibration. At coating loading less than 3%(mass)

boehmite washcoats were crack-free but γ-Al2O3 washcoats were crack-rich. At coating loading above 8%(mass)

boehmite washcoats developed crack

flake and delamination whereas γ-Al2O3 washcoats developed only crackings without delamination. In case of requirement for relatively low coating loading (<8%)

boehmite washcoats were more suitable as carrier for monolithic catalysts due to higher specific surface area and pore volume than γ-Al2O3 washcoats. γ-Al2O3 washcoats were preferred as catalyst carrier if higher coating loading was needed (>8%).