Reproducibility in the preparation of alumina slurries for washcoat application—Role of temperature and particle size distribution

The deposition of thick layers of γ-Al2O3 is often performed by the washcoating method consisting of immersing the object to coat in a slurry containing γ-Al2O3 powder and nitric acid. Although this method gives very satisfying results in terms of adherence and BET surface, it shows a bad reproducibility in terms of viscosity of the slurry and thus layer thickness. Characterizations of the slurry were performed at different preparation steps to try to understand and control the chemistry involved.