Papers by Author: Jian Lu

Abstract: A gradient nanostructured layer (GNsL) was generated on the two sides of bulk sample in 304L stainless steel by means of the surface mechanical attrition treatment. The microstructure of the GNsL was characterized via TEM observation. The prominent microstructural features involve the intersection of multi-system twin operation, subdividing the original grains into blocks, a martensite transformation mainly occurring at the interface of the twins as well, and the randomly orientated nanocrystallites at the top of surface. After annealing at 750°C for 10 min, recovery had occurred and the dislocation density was much reduced. The vast majority of the grains at the top surface were in the nanocrystalline/ultrafine range, with some recrystallization regions. The uniaxial tensile tests were performed to obtain the mechanical property of bulk samples with GNsL. The yield strength was about 2 times higher than that of the coarse-grained counterpart, but with a decrease in uniform elongation and elongation to failure as well. The relationship between the microstructure and mechanical property was discussed in detail.

Abstract: A well-aligned titania nanotube array grown on titanium sheet was fabricated by an anodization process in hydrofluoric acid-phosphoric acid-ethylene glycol aqueous electrolyte. Electroactive ruthenium oxide was filled into independent titania nanotubes or deposited on the surface of planar titanium sheet by an electrodeposition-oxidation process. Electrochemical capacitances of these well-designed ruthenium oxides were investigated for supercapacitor applications. Accordingly, ruthenium oxide-titania/titanium (RuO2-TiO2/Ti) nanocomposite exhibits a much higher specific capacitance, power and energy density than ruthenium oxide/titanium (RuO2/Ti) in sulphate acid electrolyte. The utilization efficiency of RuO2 is intensively improved by introducing a novel electrode substrate with a nanotube array structure. Such a superior performance of RuO2-TiO2/Ti nanocomposite is ascribed to its highly accessible reaction sites of well-tailored RuO2 on TiO2 nanotubes.

Abstract: Different Power types and parameters in the electrodeposition process result in different microstructures and hence mechanical properties. In this paper, direct current and double pulse power with different combinations of on and off time have been used for electrodeposition. The tensile properties of the electrodeposited (Ed) Cu with different parameters in process have been studied and also the microstructures of the Cu obtained have been examined by SEM. This paper aims at explaining the effects of one of the important parameters in electrodeposition: different power types on the tensile properties. The tensile properties of Ed Cu after Surface Mechanical Attrition Treatment (SMAT) are also shown in this paper.

Abstract: Mechanical properties of two different types of silkworm silk fibers under three conditions: (i) Bombyx mori; (ii) twisted Bombyx mori; and (iii) Tussah silk fibers were under investigations. The values of ultimate tensile strength, elongation at break and Young’s modulus were examined by performing tensile test on single bave. Scanning electron microscopy (SEM) was used to observe the morphologies of the two different types of silk fibers, and measure their general diameters so as to determine the cross-sectional area of the two different types of silk fibers and convert the experimental load-extension data into stress-strain data accordingly.