Preparation of continuous Al₂O₃/Y₂O₃ coating on carbon fiber by a novel aqueous plasma electrolysis

A novel aqueous plasma electrolysis applied for depositing a uniform and continuous Al₂O₃/Y₂O₃ ceramic coating on each fiber within a carbon fiber bundle are reported in this study. All equally spaced tungsten wires generated plasma arc, where the plasma was overlapped, excluded and extruded each other, finally a cylindrical plasma arc zone was formed, promoting the full coverage of the coating on each fiber. The Al₂O₃/Y₂O₃ coating protected the carbon fiber from oxidation above 850oC. Similarly, the coating significantly improved the oxidation resistance of the carbon fiber with the mass loss of ~5% after isothermal oxidation in N₂ atmosphere at 800°C for 30 min, compared to ~14% of bare carbon fiber. By the movement of the T300 carbon fiber bundle, 1500 m coated carbon fiber bundle with the high-quality Al₂O₃/Y₂O₃ coating deposited on each fiber was successfully realized. It is believed that the novel aqueous plasma electrolysis will find a wide range of applications in modifying the interface of the carbon fiber reinforced composites. The present investigation will also open up a new horizon for preparing a protective coating on each fiber within two/three-dimensional carbon fiber fabric.