Papers by Author: Fei Wang

Abstract: In this paper, homogeneous and well-crystallized LiFePO4 was synthesized by a novel modified solid-state reaction method following by heat treatment at relatively low temperature of 500°C in Ar. No impurities are detected in the XRD patterns. The initial charge specific capacity and discharge specific capacity reach 157.2mAhg-1 and 152.6mAhg-1 respectively at 20°C. Voltage plateaus at around 3.45V were observed in all the curves, indicating that the charge and discharge reaction proceeds as a two-phase reaction. The initial charge specific capacity is 157.2mAhg-1 at 0.1C rate, i.e. 92% of the theoretical capacity, and specific capacity decreases slightly after 100 circles at room temperature.

Abstract: The work of nanoindentation approach is developed and applied for measure of residual stress relaxation during indenter penetrates in thin films. The residual stress at given penetration depth is measured from the different integral area which under load-depth curve of different stress state. This method can measure residual stress relaxation without the need for estimating yield strength, strain hardening index and hardness.

Abstract: This paper introduces the recent progress in two-dimensional X-ray diffraction as well as its applications in microstructure and residual stress analysis. Based on the matrix transformation between diffraction space, detector space and sample space, the unit vector of the diffraction vector can be expressed in the sample space corresponding to all the geometric parameters and Bragg conditions. The same transformation matrix can be used for texture and stress analysis. The fundamental equations for both stress measurement and texture measurement are developed with the matrix transformation defined for the two-dimensional diffraction. Stress measurement using twodimensional detector is based on a direct relationship between the stress tensor and the diffraction cone distortion. The two-dimensional detector collects texture data and background values simultaneously for multiple poles and multiple directions.