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In this study, SiC nanocoatings were prepared on graphite substrates via a laser treatment process. Different laser energy densities were employed in the laser treatment. The surface morphology and elemental composition were systematically studied by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) were used to characterize the phase composition and coating microstructure. A high-temperature oxidation test was also conducted to determine their anti-oxidation performance. The results show that laser irradiation triggers the transformation from micro SiC particles into SiC nanocoating consisting of numerous polycrystalline SiC nanoparticles. At the laser energy density of 10.42 kJ cm−2, the prepared SiC nanocoating reveals the best oxidation resistance at a high-temperature environment in tested samples. In addition to its dense and crack-free surface morphology, the formation of SiO2 in the SiC nanocoating also helped to enhance the high-temperature oxidation resistance as a self-healing agent. Laser preparation of SiC nanocoating enhances the high-temperature oxidation resistance and protects the underneath graphite substrate, which serves as an efficient and effective manufacturing method for SiC protective coatings.

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In this study, novel magnetite composites FeS2/Fe3O4 were facilely synthesized by a one-pot hydrothermal method. It is applied as an adsorbent for chromium (VI) removal from aqueous solution. The pyrite (FeS2) and the magnetite (Fe3O4) were also synthesized and compared. The analysis results of XRD, SEM and XPS confirmed the formation of FeS2/Fe3O4 composite. The magnetic characterization revealed that the saturation magnetization value for FeS2/Fe3O4 was 50.89 emu/g, which is helpful for the separation. The effects of the initial pH values, adsorbent dosage, contact time and reaction temperatures on the Cr (VI) removal by various materials were studied and contrasted in detail through experiments. It is found that the composite FeS2/Fe3O4 had high removal ability for Cr (VI) at high pH. 86.1% of Cr (VI) removal efficiency was obtained when the pH value is at 12.0, the contact time is 3h and the temperature is controlled at 35 °C. FeS2 component was inferred as the major contribution for the composite to the Cr (VI) removal. FeS2/Fe3O4 displayed a promoted Cr (VI) removal efficiency with the increasing temperature and its absorption process is proved spontaneous.