Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

Abstract

bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600 8C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties but an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.

Atomic Layer Deposition Al2O3 Coatings Significantly Improve Thermal, Chemical, and Mechanical Stability of Anodic TiO2 Nanotube Layers

“…Assuming the results by Rath et al . that larger number of oxygen vacancies promotes the ART, it is clear that the Al 2 O 3 coating within our TiO 2 nanotube layers influences the number of oxygen vacancies as it possesses a barrier against the oxygen diffusion . For example, the thickest Al 2 O 3 coating (42 nm) hinders the oxygen diffusion most significantly from all used coatings in this work, leads to highest number of oxygen vacancies within TiO 2 nanotubes, and boosts the ART process that ends up with the highest rutile content.…”

“…Assuming the results by Rath et al 43 that larger number of oxygen vacancies promotes the ART, it is clear that the Al 2 O 3 coating within our TiO 2 nanotube layers influences the number of oxygen vacancies as it possesses a barrier against the oxygen diffusion. 50 For example, the thickest Al 2 O 3 coating (42 nm) hinders the oxygen diffusion most significantly from all used coatings in this work, leads to highest number of oxygen vacancies within TiO 2 nanotubes, and boosts the ART process that ends up with the highest rutile content. In contrast, the oxygen diffusion into TiO 2 takes place more easily through thinner Al 2 O 3 coatings (1 and 10 nm), resulting in a lower number of oxygen vacancies, retarding the ART within TiO 2 nanotubes.…”

A Bioactive Chitosan−Based Film Enriched with Benzyl Isothiocyanate/α−Cyclodextrin Inclusion Complex and Its Application for Beef Preservation

“…These findings were in accord with the FTIR results ( Figure 2 a), suggesting that BITC−α−CD could be completely incorporated to the CS film matrix by physical interactions. In addition, it was reported that dense and amorphous characteristics rendered alumina−based films with excellent barrier capacity against high temperature [ 44 ]. The addition of amorphous poly (lactic acid) (PLA) to the poly (butylene succinate− co −butylene adipate) film matrix endowed the composite film with enhanced gas barrier property [ 45 ].…”

Nanocomposite thin film of Ag nanoparticles embedded in amorphous Al 2 O 3 on optical sensors windows: Synthesis, characterization and targeted application towards transparency and anti-biofouling

“…Constant pass energy of 30 eV and energy steps of 0.1 eV were used for high-resolution scans. Surface erosion was realized using Ar ions accelerated at 2 keV, resulting for a-Al 2 O 3 in an erosion rate of about 0.08 nm/s [21]. The atomic concentrations were determined from photoelectron peak areas using the atomic sensitivity factors reported by Scofield, taking into account the transmission function of the analyzer.…”