Papers by Author: Jing Long Gao

Abstract: LY12 aluminum alloy samples were treated by microarc oxidation in sodium metasilicate electrolytes. The effects of treatment time on cell violate and ceramic coating thickness were investigated. The results indicate that the micro-arc oxidization process was divided into two stages, at the first stage, the cell voltage increased linearly at a very high rate of 70 V/min, at the second stage, in the range of 430-470 V, the cell voltage reached a relative stable value. The thickness of the coating increased linearly at the whole stage with increasing treating time. XRD analyses indicate that the ceramic coatings fabricated on the surface of aluminum alloys by micro-arc oxidization are composed of Al phase Al2O3 phase. SEM show that the maximum porosity of the ceramic coatings with distributing uniformly pore diameter are decreased with the increasing treatment time.

Abstract: LY12 aluminum alloy samples were treated by micro-arc oxidation in sodium metasilicate electrolytes with graphite powder. The effects of graphite concentration on thickness, roughness, friction coefficient and phase composite of ceramic coating were investigated. The results indicated that the roughness and friction coefficient of ceramic coatings increased linearly. However, the thickness decreased adding graphite powder. XRD analyses indicated that the ceramic coatings fabricated on the surface of aluminum alloys by micro-arc oxidization were composed of graphite phase. SEM showed that the porosity of the ceramic coatings with distributing nonuniform micropore diameter were inceased with the increasing graphite concentration.

Abstract: In this work, the carbon nanotubes(CNTs) were reinforced with polypropylene(PP)matrix resins to improve the electrical and thermal properties of PP/ CNTs composites in different contents of 0,1, 3,and 5 wt.%. The surface, volume resistivity and crystallization type of the composites were investigated. As a result, the maximum degradation rate temperature of the composite is improved 30 °C, the surface resistivity and volume resistivity of composite are 5 ×10⁶, 7 ×10⁵,respectively, for the optimum composition of composite (CNTs 3 wt.%). The integrated XRD pattern of the composites shows the typical α-form PP crystals.

Abstract: Polypropylene(PP)/carbon nanotube(CNTs) nanocomposites with different CNTs fraction were prepared by the melting blend method. The effects of CNTs content on the wear properties and mechanical properties were mainly investigated. The results show that the friction coefficient of the nanocomposites decreased as the concentration of CNTs is increased. With increasing CNTs content, tensile strength, ultimate strain, compact strength and Young’s modules increase firstly and then decrease. For the composite with an effective CNTs content of 3 wt, its tensile strength, ultimate strain, compact strength and Young's modules were improved by 72, 44.4,88 and 37 %, respectively, as compared to PP.

Abstract: High-density polyethylene (HDPE)/silica composites with different silicon dioxide fraction were prepared by the melting blend method. The effects of silicon dioxide content on the thermal properties and mechanical properties were mainly investigated. The results show that the thermal degradation of the composites shifts towards higher temperatures as the concentration of silicon dioxide is increased. With increasing silica dioxide content, the tension yield strength of HDPE/silicon composites increased, but its breaking elongation decreased. When silicon dioxide content is 5 %, the tension yield strength and its breaking elongation are 29.33 MPa and 102.82 %, respectively.

Abstract: Recycled polypropylene (PP)/carbon nanotube (CNTs) composites with different CNTs fraction were prepared by the melting blend method. The effects of CNTs content on the thermal properties and mechanical properties were mainly investigated. The results show that the thermal degradation of the composites shifts towards higher temperatures as the concentration of CNTs is increased. With increasing CNTs content, tensile strength and elongation at break increase firstly and then decrease. When CNTs content is 3 %, tensile strength and elongation at break are 34.71 and 27.00, respectively. Moreover, a unique tensile rupture characteristic was found by SEM observations, which explained the critical broken theory of the PP/CNTs composites.