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Amorphous Alumina Coatings: Processing, Structure and Remarkable Barrier Properties

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Abstract:

Amorphous aluminium oxide coatings were processed by metalorganic chemical vapour deposition (MOCVD); their structural characteristics were determined as a function of the processing conditions, the process was modelled considering appropriate chemical kinetic schemes, and the properties of the obtained material were investigated and were correlated with the nanostructure of the coatings. With increasing processing temperature in the range 350 °C–700 °C, subatmospheric MOCVD of alumina from aluminium tri-isopropoxide (ATI) sequentially yields partially hydroxylated amorphous aluminium oxides, amorphous Al2O3 (415 °C–650 °C) and nanostructured γ-Al2O3 films. A numerical model for the process allowed reproducing the non uniformity of deposition rate along the substrate zone due to the depletion of ATI. The hardness of the Coatings prepared at 350 °C, 480 °C and 700 °C is 6 GPa, 11 GPa and 1 GPa, respectively. Scratch tests on films grown on TA6V titanium alloy reveal adhesive and Cohesive failures for the amorphous and nanocrystalline ones, respectively. Alumina Coating processed at 480 °C on TA6V yielded zero weight gain after oxidation at 600 °C in lab air. The surface of such low temperature processed amorphous films is hydrophobic (water Contact angle 106 degrees), while the high temperature processed nanocrystalline films are hydrophilic (48 degrees at a deposition temperature of 700 °C). It is Concluded that amorphous Al2O3 Coatings Can be used as oxidation and Corrosion barriers at ambient or moderate temperature. Nanostructured with Pt or Ag nanoparticles, they Can also provide anti-fouling or Catalytic surfaces.

Keywords: AMORPHOUS ALUMINA; CORROSION RESISTANCE; MECHANICAL PROPERTIES; MOCVD; OXIDATION RESISTANCE; PROCESS MODELING; WETTING

Document Type: Research Article

DOI: https://doi.org/10.1166/jnn.2011.5068

Publication date: 2011-09-01

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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