title: Passivation of pigment-grade TiO(2) particles by nanothick atomic layer deposited SiO(2) films.
abstract: Pigment-grade TiO(2) particles were passivated using nanothick insulating films fabricated by atomic layer deposition (ALD). Conformal SiO(2) and Al(2)O(3) layers were coated onto anatase and rutile powders in a fluidized bed reactor. SiO(2) films were deposited using tris-dimethylaminosilane (TDMAS) and H(2)O(2) at 500 °C. Trimethylaluminum and water were used as precursors for Al(2)O(3) ALD at 177 °C. The photocatalytic activity of anatase pigment-grade TiO(2) was decreased by 98% after the deposition of 2 nm SiO(2) films. H(2)SO(4) digest tests were performed to exhibit the pinhole-free nature of the coatings and the TiO(2) digest rate was 40 times faster for uncoated TiO(2) than SiO(2) coated over a 24 h period. Mass spectrometry was used to monitor reaction progress and allowed for dosing time optimization. These results demonstrate that the TDMAS-H(2)O(2) chemistry can deposit high quality, fully dense SiO(2) films on high radius of curvature substrates. Particle ALD is a viable passivation method for pigment-grade TiO(2) particles.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, UCB 424, Boulder, CO 80309-0424, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: King
authors.forename: Xinhua
authors.initials: X
authors.lastname: Liang
authors.forename: Beau B
authors.initials: BB
authors.lastname: Burton
authors.forename: M
authors.initials: M
authors.lastname: Kamal Akhtar
authors.forename: Alan W
authors.initials: AW
authors.lastname: Weimer