The grain growth and thermal stability of nanocrystalline Ni–TiO2 composites were systematically investigated. The nanocrystalline Ni–TiO2 composites with different contents of TiO2 were prepared via electroplating method with the variation of TiO2 nano-particles concentration. The effect of TiO2 content on the grain size, phase structure and microhardness was investigated in detail. The corresponding grain growth and diffusion mechanisms during the heating process were also discussed. The optimal microhardness of HV50 270 was achieved for the composite with addition of 20 g/L TiO2 nano-particles after annealing at 400 °C for 90 min. The calculation of the activation energy indicated that lattice diffusion dominated at high temperatures for the nanocrystalline Ni–TiO2 composites. It was indicated that the increase of TiO2 nano-particles content took effect on restricting the grain growth at high temperatures by increasing the grain growth activation energy.

•The Al2O3 coating was continuously deposited by aqueous plasma technique.•The deposited Al2O3 coating was dense with the thickness of 80–120 nm.•The carbon fiber was effectively protected by the Al2O3 coating.•The tensile strength reached ∼1.3 GPa after oxidation at 700 °C for 20 min.A novel room-temperature aqueous plasma electrolysis technique has been developed in order to prepared Al2O3 nano-coating on each fiber within a carbon fiber bundle. The microstructure and formation mechanism of the Al2O3 nano-coating were systematically investigated. The oxidation resistance and tensile strength of the Al2O3-coated carbon fiber was measured at elevated temperatures. It showed that the dense Al2O3 nano-coating was relatively uniformly deposited with 80–120 nm in thickness. The Al2O3 nano-coating effectively protected the carbon fiber, evidenced by the slower oxidation rate and significant increase of the burn-out temperature from 800 °C to 950 °C. Although the bare carbon fiber remained ∼25 wt.% after oxidation at 700 °C for 20 min, a full destruction was observed, evidenced by the ∼0 GPa of the tensile strength, compared to ∼1.3 GPa of the Al2O3-coated carbon fiber due to the effective protection from the Al2O3 nano-coating. The formation mechanism of the Al2O3 nano-coating on carbon fiber was schematically established mainly based on the physic-chemical effect in the cathodic plasma arc zone.Download high-res image (123KB)Download full-size image

•A thick TiZrNiCuBe amorphous coating was successfully deposited on 304L.•The amorphous coating showed superior corrosion resistance in HNO3.•The heterogeneous surface structure deteriorated the corrosion resistance.•The coating will find a wide range of applications in corrosive environments.Electrospark deposition was applied to successfully deposit TiZrNiCuBe metallic glass coating on 304L stainless steel. The coating was fully amorphous with the thickness of ∼380 μm. The corrosion behavior was investigated in 1, 6 and 11.5 mol/L HNO3. The optimal corrosion resistance was achieved in 6 mol/L HNO3 for the coating. The corrosion mechanism was discussed based on the effect of the structural heterogeneity on the corrosion resistance. It was found that the heterogeneous surface structure deteriorated the corrosion resistance. We believe that the coating will find a wide range of applications for protecting working parks in corrosive environments.

•A fully amorphous Ti-based metallic glass coating was formed.•The amorphous coating exhibited superior corrosion resistance in HNO3.•A uniform and mix-structured TiO2 corrosion product was formed.•The coating may become the optimal candidate for nuclear applications.This paper investigated the corrosion resistance of a Ti-based metallic glass coating in concentrated HNO3 solution, and discovered the coating's superior corrosion resistance compared with 304 L substrate. The coating exhibited a fully amorphous and pore-free structure with the thickness of ∼380 μm. A relatively uniform and thick passivation film was formed on the surface of the coating as an oxygen diffusion barrier, leading to the much improved corrosion resistance. The Raman spectrum evidenced that the passivation film was mainly TiO2 with a mixed structure of anatase and rutile. We believe that the present findings will open up a new horizon for coatings in spent nuclear fuel reprocessing applications.

•Ni/Cu/Ni–P triple-layered coating was successfully prepared on Mg–Li alloy.•Superior corrosion resistance was obtained for the Ni/Cu/Ni–P coating.•The Ni/Cu/Ni–P coating achieved long-term protection for the Mg–Li alloy.•The outmost Ni layer significantly improved the pitting potential.•The outmost Ni was preferentially corroded, galvanically protecting Cu.In the present paper, a protective Ni/Cu/Ni–P triple-layered coating was successfully prepared on Mg–Li alloy. The Ni, Cu and Ni–P layers served as the outmost, middle and transition layers with the thickness of ~ 0 μm, ~ 20 μm and ~ 5 μm, respectively. The Ni/Cu/Ni–P coating showed superior corrosion resistance in 3.5 wt.% NaCl solution with the corrosion current density of 4.04 μA cm− 2 compared to 12,878.2 μA cm− 2 of the Mg–Li substrate. No corrosion was macroscopically observed after the coating was immersed in 3.5 wt.% NaCl solution for 360 h. The corrosion mechanism was systematically discussed based on cyclic voltammetry. It was revealed that the outmost Ni layer significantly improved the pitting potential. The Cu middle layer was galvanically protected. We believe that the coated Mg–Li alloy exhibiting superior corrosion resistance will find a wide range of applications in aeronautic, astronautic, electronic and automotive industries.