Amorphous Alumina Barrier Coatings on Glass: MOCVD Process and Hydrothermal Ageing

Abstract

Amorphous alumina coatings are applied on the inner surface of glass containers aiming at improving their hydrothermal ageing barrier properties. A direct liquid injection technology is implemented in a metal-organic chemical vapor deposition (MOCVD) process to feed the reactor in a controlled and reproducible way with a solution of aluminum tri-isopropoxide (ATI) in anhydrous cyclohexane. Amorphous alumina coatings are characterized by X-ray diffraction, electron probe microanalysis, scanning electron microscopy, atomic force microscopy and scratch-test method. They are amorphous and hydroxylated at process temperatures between 360 and 420 °C and close to Al 2 O 3 stoichiometry between 490 and 560 °C. Hydrothermal ageing simulated by a standard sterilization cycle results in the increase of the root mean square of the surface of the coatings from ≈17 to 61 nm and in the increase of the porosity without affecting the adhesion of the coatings on the glass substrates.