Washcoating of low surface area cerium oxide on complex geometry substrates

ABSTRACT

An acid-free formulation based on water, glycerol, and polyvinyl alcohol (PVA) was studied to disperse and stabilize, via steric-like interaction, low surface area cerium oxide powders. A dispersion route that implies a milling process and a proper ratio among the components was experienced. PVA was used as viscosity modulator, to enhance viscosity and system stability. Newtonian fluids, suitable for foams dip-coating, were obtained in the application shear range. Foams with different porosities (20, 30, and 40 pore per inch density) were coated. It was found that withdrawal velocity did not affect deposition: a constancy in coating load was obtained once rheology was fixed, while multiple dipping was effective to enhance load. An optimal flash drying temperature (350°C) was identified to consolidate the coated layer and to decompose the organic additives. Good loads, homogeneous coverage, and no pore clogging were obtained after calcination at 900°C. Even though acceptable weight losses were obtained, further investigations need to be accomplished to understand data scattering after adhesion tests.