Research On Performance Of Al₂O₃ /ZnO Composite Nanopowder As Lubricant Additive

In this paper Al₂O₃/ZnO composite nanopowder were prepared and modified by a nonhydrolytic sol-gel route with anhydrous AlCl₃ and anhydrous ZnCl₂ as raw materials. In order to compare the performances of composite nanopowder and single nanopowder, Orthogonal test 1 with four factors and three levels was designed: Zn/Al (1:0, 0:1, 1:2); temperature (115℃, 125℃, 135℃); oxygen donor (glycerin, PEG400, oleic acid); constant temperature time (1.5h, 2h, 2.5h). In order to prepare relatively small nanopowder orthogonal test 2 with four factors and three levels was designed: Zn/Al (1:2, 1:1, 2:1); solvent (absolute ethyl alcohol, acetone, normal propyl alcohol); oxygen donor (glycerin, laurinol, oleic acid); constant temperature time (1.5h, 2h, 2.5h).Nanopowder were characterized through laser particle size analysis, x-ray diffraction analysis(XRD), infrared spectrum analysis(IR), scanning electron microscope (SEM) analysis, transmission electron microscopy (TEM) analysis, zeta potential analysis and uv-vis spectrophotometer analysis. Tribological Properties of Al₂O₃/ZnO composite nanopowder using as lubricant additive were researched through the four-ball friction test and thrust ring friction test.Factors affecting the average particle size of Al₂O₃/ZnO composite nanopowder were obtained through analyzing the orthogonal test, they were oxygen donor, solvent, Zn/Al and constant temperature time in descending order; and the optimum project preparing Al₂O₃/ZnO composite nanopowder was obtained, it was: Zn/Al (1:1), solvent (absolute ethyl alcohol), oxygen donor (glycerin, laurinol), constant temperature (2h). In this condition, Al₂O₃/ZnO composite nanopowder were obtained with the average particle size of 61nm, The distribution of particle size from 40nm to 100nm was comparatively centralized. The Al₂O₃/ZnO composite nanopowder were amorphous through XRD, SEM, TEM and IR analysis, with the particle size was uniform, the morphology was regular, the bounds was clear and monodisperse, no reunion phenomenon. The Al₂O₃/ZnO composite nanopowder prepared using oleic acid as oxygen donor performed good oil-solubility and dispersed stability in No.20 mechanical oil through zeta potential and ultraviolet absorbance analysis. Oleic acid not only was used as oxygen donor, its peculiar long organic chain was showed well modification effect, modified the Al₂O₃/ZnO composite nanopowder and made the preparation and modification processes synchronous.From the friction tests with the nanopowder prepared by oleic acid as No.20 mechanical oil additive, we found that the firction coefficients and the worn scars were smallest and the antiwear and antifriction performances were best when the concentration was 0.1wt%, and different nanopowder showed different antiwear and antifriction performances. The firction coefficients fall of thrust ring: Al₂O₃(25.3%), ZnO(41.7%), Al₂O₃/ZnO(37.5%); the average diameter fall of four-ball worn scars: Al₂O₃(7.2%), ZnO(3.2%), Al₂O₃/ZnO(6.0%). The Al₂O₃/ZnO composite nanopowder were not only showed nice antifriction performance, but also nice antiwear performance, causing the composite effect of Al₂O₃ and ZnO nanopowder, with the antiwear and antifriction synthetical performances better than single Al₂O₃ and ZnO nanopowder. From the surface morphology and element analysis of thrust ring friction test and the four-ball worn scars analysis, we found that the antiwear and antifriction mechanisms of Al₂O₃/ZnO composite nanopowder using as lubricant additive mainly covered microbearing effect, surface restoring effect and strengthening effect.