Oxide Coating of Alumina Nanoporous Structure Using ALD to Produce Highly Porous Spinel

In this work we show that atomic layer deposition (ALD) stands out as a very promising method for coating nanomaterials and, more specifically, nanoporous materials of technological interest in heterogeneous catalysis. ALD is capable of coating extremely complex shapes with high conformality and high aspect ratios. The current work describes deposition of ZnO and CoO thin films on ?-alumina nanoporous particles with sizes ranging from 20 to 100 mu m in diameter, as well on aluminum membrane discs (anodiscs), and converting the surfaces into nanoporous, mechanically more robust spinel phases. We maintain the porosity of the supporting ?-alumina particle, despite the addition of material to the 16?nm pores, by utilizing subsequent reactions between the coated layer and ?-alumina, following the Kirkendall mechanism. The oxide thin film coatings are deposited at 175 and 167 degrees C for ZnO and cobalt oxide, respectively, and thereafter annealed at from 600 to 1000 degrees C for 3?h. This represents a new way to produce highly porous spinel particles and spinel-coated membrane discs.