Papers by Author: Wen Jing Li

Abstract: Nb_1-xTi_xSe₂ (x=0～1) micro/nano-particles have been successfully prepared via solid-state thermal (750°C) reaction between microsized Nb, Ti with Se powders under seal environment in a seal quartz tube and characterization by X-ray diffractometer and scanning electron microscopy. It was found that the morphologies of the as-prepared products changed from microplates to micro-nanoparticles or aggregations composed of layer structure with the doping of Ti. And the amount of regular hexagonal microplates evidently reduced and nanoscaled particles increased with the increase of the contents of Ti dopant within a certain limit (1-20 atwt. %). The tribological properties of the as-prepared products as additives in paraffin were investigated by UMT-2 multispecimen tribotester. By the addition of Nb_1-xTi_xSe₂ micro/nanoparticles in paraffin, the antiwear ability was improved and the friction coefficient was decreased. The paraffin with Nb_1-xTi_xSe₂ micro/nanoparticles showed better tribological properties than that with pure NbSe2. A combination of the molecule-bearing mechanism of sliding friction, and fill in-repair work between the rubbing surfaces can explain the good friction and wear properties of Nb_1-xTi_xSe₂ micro/nanoparticles.

Abstract: The inorganic materials（MoSe₂/C) and MoSe2 were synthesized via solid-state reaction methods and characterized by a series of techniques. The growth process of the products was discussed on the basis of the experimental facts. The tribological properties of MoSe₂/C and MoSe₂ as additives in 150bn basic oil were investigated by UMT-2 multispecimen tribotester. Under the determinate conditions, the friction coefficient of the basic oil containing MoSe₂/C (or MoSe₂) was lower than that of the basic oil. Moreover, the tribological property of the basic oil with the MoSe₂/C was better than that with MoSe₂ nanoflakes. A combination of sliding friction, stable tribofilm and fill in-repair mechanisms on the rubbing surface could explain the good friction and wear properties of MoSe₂/C and MoSe₂ as additives.

Abstract: The YBa₂Cu₃O_x/Ag and Bi₂Sr₂CaCu₂O_x/Ag self-lubricating composites were prepared using powder metallurgic method. The crystal structure and morphology of the as-synthesized samples were characterized by XRD and SEM. The YBa₂Cu₃O_x/Ag and Bi₂Sr₂CaCu₂O_x/Ag self-lubricating composites were found to compose of superconductor phase and Ag phase. The tribological properties from ultra-low temperature to room temperature of the composites were studied by pin-on-disk friction test. It was found that the friction coefficients of pure YBa₂Cu₃O_x (YBCO) and Bi₂Sr₂CaCu₂O_x (BSCCO) were both dropped abruptly when the temperature cooled below the superconducting transition temperature. At room temperature, the friction coefficient of pure YBa₂Cu₃O_x is 0.68~0.95, when mixing 15wt% Ag, the friction coefficient of the sample decreased to the lowest value 0.11. The friction coefficient of pure Bi₂Sr₂CaCu₂Ox is 0.15~0.17, When Ag content reach 10wt%, the coefficient was lowest (average value is 0.13). The addition of appropriate amount of Ag obviously improve the tribological property of YBCO, while only slightly meliorate that of BSCO. On the other hand, the YBCO/Ag composites exhibit better tribological properties than BSCCO/Ag composites at higher load under the same experimental condition.