Papers by Author: Xiao Na Li

Abstract: Concurrent engineering claims all influence factors within product lifecycle should be took into account during the stage of product design. After analyzing the relationship between concurrent engineering and virtual prototyping, the human-machine system simulation process and method based on virtual prototyping technology were discussed and illustrated with bicycle design, and the product design method based on virtual prototyping was proposed in this paper.

Abstract: [(Mo,Sn)(Ti,Zr)₁₄]Nb₁ serial alloy compositions were designed using a cluster-plus-glue-atom model to receive BCC β-Ti alloys with low Youngs modulus (E) in Ti-based multi-component systems, where the square brackets enclose the coordination polyhedron cluster CN14 of the BCC structure and Nb is the glue atom. These serial alloys were prepared into rods with a diameter of 6 mm by copper-mould suction casting method. XRD and tensile test results indicated that all these alloy series possessed a monolithic BCC structure except [SnTi₁₄]Nb₁ and [(Mo_0.5Sn_0.5)Ti₁₄]Nb₁ due to Sn deteriorating BCC structural stability. A combination of Mo_0.5Sn_0.5 at the cluster center, as well as low-E Nb and Zr in the glue and cluster shell respectively, can reach simultaneously low E and high BCC stability, incarnated in the [(Mo_0.5Sn_0.5)(Ti₁₃Zr)]Nb₁ alloy which has the lowest E of 48 GPa in the suction-cast state.

Abstract: In this study, Cu films doped with different Sn concentrations from 0.6-1.4 at.% were prepared by magnetron co-sputtering. The electrical resistivities and microstructures of Cu (Sn) films after annealings were investigated. The results showed that a sharp increase of the resistivity of Cu (1.4 at.% Sn) and Cu (1.1 at.% Sn) films were found after annealing above at 500°C. The existence of 0.6 at.% Sn in the Cu film is in solid solution state. A minimum electrical resistivity value of ~3.2μΩ•cm was obtained after annealing at 600°C for 1h . Even after a annealing at 700°C, the Cu/Si interface of Cu (0.6 at.% Sn) film still remained sharp without any Cu-Si and Cu-Sn compounds. The results confirmed that the lower resistivity and higher stability of Cu films can be achieved by strictly control of the doping concentrations and the existing state (solid solution without compounds and precipitates) of Sn element.

Abstract: High current pulsed electron beam (HCPEB) is a fairly new technique for improving surface properties such as corrosion and wear resistances. One of the negative effects induced by HCPEB is the potential formation of craters on the surface of the HCPEB treated materials. These changes can impair the corrosion-resistance by promoting pitting. The mechanisms of nucleation and growth are detailed and the effect of the number of pulses on crater formation is discussed.

Abstract: Fe/Si multi-layer films were fabricated on Si (100) substrates utilizing radio frequency magnetron sputtering system. Si/β-FeSi2 structure was found in the films after the deposition. Structural characterization of Fe-silicide sample was performed by transmission electron microscopy, to explore the dependence of the microstructure of β-FeSi2 film on the preparation parameters. It was found that β-FeSi2 particles were formed after the deposition without annealing, whose size is less than 20nm ,with a direct band-gap of 0.94eV in room temperature. After annealing at 850°C, particles grow lager, however the stability of thin films was still good.

Abstract: A 10-T magnetic field was introduced to investigate precipitation behavior of Al-4wt.%Cu alloys during short time aging at 130°C. DSC, Vickers micro-hardness tests, EPMA and TEM were used to characterize aging process. The results show that high magnetic field improves the diffusion of Cu atom, lowers the stability of G.P.( I )zone and speeds up its solution, and lowers the precipitation temperature of the phases, thus accelerates the ageing course during the early stage at low temperature. Furthermore the high magnetic field has influence on the size of the θ″-phase. The micro-hardness of the field-treated specimen is always higher than the non-field ones, which indicates the high magnetic field strengthens the hardening effect.

Abstract: Carbon-doped b-FeSi2 films synthesized by ion implantation are investigated with the aim to fabricate high-quality semiconducting b-FeSi2 layer on silicon substrate. According to transmission electron microscopy cross-section observations, carbon-doped films, with homogeneous thickness and smooth b/Si interface, have higher quality than binary Fe-Si films. In particular, annealing at 500 °C ~ 700 °C leads to the formation of a flat and continuous b-type silicide layer. Improved thermal stability of the b phase is also found. Optical emission spectroscopy measurements show that the doping influences only slightly the band gap values.