Papers by Author: Xian Guo Hu

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Authors: B. May, M.R. Hartwich, R. Stengler, W.P. Weinhold, Xian Guo Hu
Authors: Xian Guo Hu, Wen Ju Cai, Jiu Cong Wan, Yu Fu Xu, Xiao Jun Sun
Abstract: The electroless nickel-phosphor coatings containing molybdenum disulfide nanoparticles were prepared and analyzed in this paper. The effects of incorporation of MoS2 into the Ni-P coating on the morphology of the coating surface and corrosion properties were also studied. Corrosion tests were conducted inside a salt spray box with NaCl solution (5.0 wt%). The corrosional surfaces were studied and analyzed through optical microscope, X-ray spectrometer (XRD) and scanning electron microscopy (SEM). The investigation on the relationship between heat-treatment and the corrosion resistance of the coatings showed that the corrosion resistance of the composite coating became worse because of the occurrence of transformation from non-crystalline to crystalline, and then increased the metastable intergradation of the composite coating. Meanwhile, the experimental results also showed that corrosion resistance of the coating containing MoS2 was higher than that of steel substrate. The corrosion mechanism of the composite coatings was mainly ascribed to the formation of micro-cell around the nanosized MoS2 particles, and the active ion like Cl- destroyed the surface film and induced the corrosion towards the inside part of coating.
Authors: Kun Hong Hu, Xian Guo Hu, Xiao Jun Sun, He Feng Jing, Song Zhan
Abstract: Molybdenum sulfide nanoparticles were prepared via quick homogeneous precipitation method (QHPM) by the reaction between Na2MoO4 and CH3CSNH2 in the presence of sulfuric acid at 80 oC. The as-synthesized molybdenum sulfide particles were studied by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results showed that the as-synthesized molybdenum sulfide was amorphous MoS3 nanoparticles with an average size of 40 nm. The resultant amorphous MoS3 nanoparticles were then calcined under hydrogen gas flow at a selected temperature for 50 minutes. The results of XRD, TEM, and HRTEM confirmed that the MoS2 nanoparticles with about 40 nm were prepared from the amorphous MoS3 nanoparticles at 780 oC.
Authors: Yi Jian Feng, Chang Lin Gui, Ji Gui Chen, Xian Guo Hu
Abstract: Nanoparticles can be made into bulk material by sintering process in order to obtain some excelled properties of nanomaterials. Because ZrO2 has a good thermal-resistance property, it has been widely used as thermal-barrier material, including functionally graded material (FGM) and thermal barrier coating (TBC). In the present paper, ZrO2 nanoparticles with a size of 10, 50, 80 and 100 nm were fabricated into bulk material respectively with the help of cold and isostatic pressing processes. The thermal diffusion coefficient, the hot expand coefficient and the specific heat of these bulk materials were measured. The experimental results showed that after ZrO2 nanoparticles being pressed and sintered, the nanoparticles were found in a state of aggregation in the bulk materials, but there are some nanometer size effects in their thermal physic properties. It was found that the thermal diffusion coefficients between 100-150oC were obviously different, as the samples were made of ZrO2 with different nanometer dimensions. The less the nanometer size of particles, the higher the thermal diffusion coefficient. The hot expand coefficient of the sample from 100 nm ZrO2 particles was 96.9741×10-7 K-1 between 30-300 oC. However, the hot expand coefficient of the sample from 10 nm ZrO2 particles was 100.2345×10-7 K-1. On the other hand, the specific heat of the bulk material from ZrO2 nanoparticles was much higher than that of the bulk material from micron ZrO2 particles. When the temperature was over 350 oC, the size of ZrO2 nanoparticles influenced the specific heat of bulk material even more. With the decreasing of size of ZrO2 nanoparticles the specific heat of bulk material increased continuously.
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