Papers by Author: Han Zhang

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Authors: Ying Zhang, Guang Hong Lu, Han Zhang, Tian Min Wang, Sheng Hua Deng, Xue Lan Hu
Authors: Jun Zhao, Han Zhang, Yong Ming Yang, Jiu Chuan Chen, Quan Xing Wen, Zhi Wang, Li Tao Zhang, Yu Wei Gao
Abstract: In this paper, the process of severe cold-rolling and annealing for Q235 steel with lath martensite has demonstrated a new promising technique for producing in-situ composite multi-nanolayer steel. Cold rolling and subsequent annealing have great impact on microstructure evolution as well as mechanical properties. In the as-rolled state, the strength (b 2112 MPa) is approximately four times increased than as-received material, which is attributed to work hardening and grain refining during cold rolling. As cold-rolled sample subjected to further annealing below 500 °C, deformed microstructure underwent further recovery and recrystallization and finally became refined equiaxed grains; ultrafine ferrite grains, nano-carbides precipitated uniformly were seen in the specimen annealed at 500 °C, and the phenomenon of fracture delamination was observed from the specimens, the delamination plane was parallel to the rolling plane, in-situ composite weak interfaces effect has great impact on the fracture surface. Annealing at and above 600 °C resulted in coarse ferrite grains with spheroidized coarse carbides, causing grain growth.
Authors: Jun Zhao, Han Zhang, Zhi Wang, Hong Yan Zhai, Quan Xing Wen, Min Wang, Yu Wei Gao
Abstract: A new type of in-situ composite nano-multilayer plate with ultra-high strength (b 2112 MPa), Q235 steel plate with nano-layered structure of lath martensite produced by severe cold-rolling, was developed. After cold-rolling, subsequent annealing has great effect on the deformed lath morphology and grain refinement. Microstructure recrystallizing course have taken place after long time annealing at 350 °C. The recrystallization activation energy is 151 kJmol-1. Microstructure characteristics along rolling direction arrangement was decreased after annealing at 400 °C. In addition to the ultrafine ferrite grains, nano-carbides precipitated uniformly in the specimen annealed at 500 °C. Annealing at and above 600 °C resulted in coarse ferrite grains with spheroidized coarse carbides, causing grain growth. The average crystal size is about 4.7 m after annealing for 60 min at 600 °C.
Authors: L. Zhang, Jing Yu, Han Zhang
Abstract: A series of samples of Y1-xCaxBa2Cu3Oy (YCBCO) were synthesized with 0.05≤x≤0.3 and characterized by DC magnetization, X-ray diffraction (XRD), and Rietveld refinement. It was found that Ca replaces Y and Ba in YBa2Cu3Oy (YBCO) simultaneously, and the amount of Ca in the Y and Ba positions is estimated by the refinement,respectively. The experimental results showed that the structural changes had a close correlation with Tc. With careful analysis of the change of the Tc below and above x=0.2 and the changes of the bond lengths, such as Cu(2)-O(2) and Cu(2)-O(3), it is suggested that the Ca substitution for Y suppresses the Tc more strongly than that for Ba.
Authors: Y.W. Liu, X.F. Rui, Y.Y. Fu, Han Zhang
Abstract: a-Fe2O3 nanowire was successfully synthesized by oxidation of pure iron. The as-synthesized a-Fe2O3 nanowire arrayed normal to the surface of the substrate, were perfect single crystals with diameters of 20 to 40 nm and lengths varying from 2 to 5 µm. The magnetic property of the nanowires was studied, and some interesting phenomena were observed. The magnetic moment of the nanowire shows an antiferromagnetic behavior at high temperature and a weakly ferromagnetic behavior at low temperature. The block temperature of the a-Fe2O3 nanowire was found to be significantly higher than that of a-Fe2O3 nanoparticle.
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