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Materials 2015, 8(3), 1249-1263; doi:10.3390/ma8031249

Gas-Phase Deposition of Ultrathin Aluminium Oxide Films on Nanoparticles at Ambient Conditions

Department of Chemical Engineering, Delft University of Technology, 2628 BL Delft, The Netherlands
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Academic Editor: Silvia Gross
Received: 1 December 2014 / Revised: 26 February 2015 / Accepted: 9 March 2015 / Published: 19 March 2015
(This article belongs to the Special Issue Inorganic Core-Shell Structures)
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Abstract

We have deposited aluminium oxide films by atomic layer deposition on titanium oxide nanoparticles in a fluidized bed reactor at 27 ± 3 °C and atmospheric pressure. Working at room temperature allows coating heat-sensitive materials, while working at atmospheric pressure would simplify the scale-up of this process. We performed 4, 7 and 15 cycles by dosing a predefined amount of precursors, i.e., trimethyl aluminium and water. We obtained a growth per cycle of 0.14–0.15 nm determined by transmission electron microscopy (TEM), similar to atomic layer deposition (ALD) experiments at a few millibars and ~180 °C. We also increased the amount of precursors dosed by a factor of 2, 4 and 6 compared to the base case, maintaining the same purging time. The growth per cycle (GPC) increased, although not linearly, with the dosing time. In addition, we performed an experiment at 170 °C and 1 bar using the dosing times increased by factor 6, and obtained a growth per cycle of 0.16 nm. These results were verified with elemental analysis, which showed a good agreement with the results from TEM pictures. Thermal gravimetric analysis (TGA) showed a negligible amount of unreacted molecules inside the alumina films. Overall, the dosage of the precursors is crucial to control precisely the growth of the alumina films at atmospheric pressure and room temperature. Dosing excess of precursor provokes a chemical vapour deposition type of growth due to the physisorption of molecules on the particles, but this can be avoided by working at high temperatures. View Full-Text
Keywords: atomic layer deposition (ALD); coating; nanoparticles; aluminium oxide; thin films; fluidized bed reactor; ambient conditions; room temperature; atmospheric pressure atomic layer deposition (ALD); coating; nanoparticles; aluminium oxide; thin films; fluidized bed reactor; ambient conditions; room temperature; atmospheric pressure
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Valdesueiro, D.; Meesters, G.M.H.; Kreutzer, M.T.; van Ommen, J.R. Gas-Phase Deposition of Ultrathin Aluminium Oxide Films on Nanoparticles at Ambient Conditions. Materials 2015, 8, 1249-1263.

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