The synergistic role of Ti microparticles and CeO2 nanoparticles in tailoring microstructures and properties of high-quality Ni matrix nanocomposite coating
In current work, Ni-Ti-CeO 2 nanocomposite coatings were achieved by co-adding Ti microparticles and CeO 2 nanoparticles. Designed experiments and COMSOL computer simulation were applied to reveal the synergistic role of Ti microparticles and CeO 2 nanoparticles in tailoring the spatial microstructures and properties of Ni-Ti-CeO 2 nanocomposite coating. Unilaterally, the conductive Ti microparticles conducted the growth behavior of Ni grains by current density concentration, distorting electronic field lines and heterogeneous nucleation. Individual domains consisting of inner nanograins and outer radial columnar grains surrounded Ti microparticles, where Ti microparticles acted as seeds. Ti microparticles tended to be aggregated, leading to spatial heterogeneity of microstructures. Ni deposits buried the Ti microparticles in forms of “covering model”, contributing to the formation of inside voids and rough surface and aggregation of Ti microparticles; on the other hand, the non-conductive CeO 2 microparticles hardly changed the distribution of current density and electronic field lines on the cathode surface. Ni deposits buried the CeO 2 microparticle in forms of “stacking model”, avoiding the inside voids and aggregation of particles. The incorporation of CeO 2 microparticle brought in microstructure evolutions only on its top side without disturbing the growth behavior of Ni grains on its lateral side or bottom, suggesting the limited effects. This was correlated with the presence of current concentration above the CeO 2 microparticle at the last stage of burying CeO 2 microparticle. The co-addition of Ti microparticles and CeO 2 nanoparticles into Ni deposits exploited the complementary action of the two particles, which gave birth to satisfied spatial microstructures and improved hardness. Ti microparticles took major responsibility for microstructure evolutions, while the CeO 2 nanoparticles were mainly in charge of the microstructure homogeneity.
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