Characteristics of hydrogen plasma treatment on Al2O3/CrxOy/AlmOn composite film via Al-ion-implantation and ultra-low partial pressure oxidation

Abstract In this paper, the preparation of Al2O3/CrxOy/AlmOn composite film and the stability of the composite film in a hydrogen plasma environment are studied. Al ions were implanted into the surface of pure chromium substrate, which was expected to induce the transformation of alumina into α-Al2O3 by using Cr2O3 formed under ultra-low oxygen partial pressure conditions as a template for crystal nucleation. This was to improve the hydrogen barrier properties of the film. The surface morphology evolution and phase composition of three different implanted doses (2 × 1017 ion/cm2, 3.5 × 1017 ion/cm2, and 5 × 1017 ion/cm2) were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and the cross-sectional structure of the film was analyzed by transmission electron microscopy (TEM). The stability of the film in a hydrogen plasma environment was evaluated by electrochemical methods. The experimental results show that the composite coating is composed of a three-layer structure of Al2O3/CrxOy/AlmOn. The Al2O3 layer is mainly composed of γ-Al2O3 and a small amount of α-Al2O3. The CrxOy and AlmOn layers are partial metallic Cr or Al, and they contain a small amount of corresponding oxides. The composite coating shows high stability after hydrogen treatment. Electrochemical tests show that the composite film has good hydrogen permeation resistance. This research provides a new coating for potential hydrogen permeation barrier application.