Search

Titanium alkoxide (titanicone) thin films were coated on large quantities of sub-micron sized silica particles at 100 °C using molecular layer deposition (MLD) in a fluidized bed reactor. Titanium tetrachloride and ethylene glycol were used as precursors. The content of titanium on the particles increased linearly as the number of MLD coating cycles increased. The conformity of the films, with a thickness of ~12 nm, was verified using TEM for silica particles coated with 50 cycles of titanicone. The composition of the titanicone films was confirmed using energy dispersive X-ray spectrometry. Porous titanium oxide films were formed for the particles coated with 50 cycles of titanicone MLD by oxidation in air at 400 °C or by decomposition of the organic components of the titanicone films in the presence of water. The thicknesses of the films were reduced from ~12 nm to ~8 nm after oxidation in air at 400 °C for 1 hr. The effect of aging on the titanicone films was studied at different lengths of aging time in the presence of water. A greatly increased surface area of 48.8 m 2 g −1 was obtained for the particles exposed to water for 24 hr, compared to the as-deposited 50 cycles of titanicone coated sample with a surface area of 7.7 m 2 g −1 . The decomposition of titanicone films, after exposure to water vapor for various lengths of time, was studied using Fourier transform infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Highly structured porous alumina thin films have many practical uses, including membrane applications and catalyst encapsulation. One route to synthesizing these films that offers exceptional control over film thickness to several angstroms starts with the molecular layer deposition (MLD) of an aluminum alkoxide (alucone) film. Oxidizing the alucone film removes the organic component and produces the desired nanoporous alumina. The pore size can be controlled by selection of the length of the carbon chain in the polymer film. In this study, 500nm silica nanoparticles were coated with 10–40cycles of alucone using a three-step ABC MLD process. Trimethylaluminum, ethanolamine, and maleic anhydride were used as precursors. The organic component of the alucone films was removed in air by calcination at elevated temperature or in water at room temperature. It is shown that the pore size of the porous films can be increased from 0.6 to 0.8nm by depositing an alucone film having longer carbon chains. Film surface area, composition, thickness, and pore size were measured, confirming that the ABC MLD process can produce high quality porous alumina films and provide a pathway to tune nanopore size in these films. [Copyright &y& Elsevier]

The article describes the usage of molecular layer deposition (MLD) for the conformal coating of ultra-thin aluminum alkoxide (alucone) polymer films on primary silica and titania nanoparticles within a fluidized bed reactor. The usage of in situ mass spectrometry to demonstrate the self-limiting nature of alucone MLD film growth as a function of the individual exposures of trimethylaluminum and ethylene glycol is noted. Also noted is the fact that the highest growth rate was found to coincide with the lowest sample temperature.