Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials

The Processing Optimization on the Preparation of MgB2 Film by Molten Salt Electrochemistry

Author SongLiang
Tutor QiYang
School Northeastern University
Course Materials Physics and Chemistry
Keywords MgB2 molten salt electrochemistry crystal properties process optimization
CLC TB383.2
Type Master's thesis
Year 2008
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MgB2 superconductor, a common intermetallic compound, has attracted much attention due to its high critical transition temperature, high critical current densities(Jc,105A/cm-2) and simple structure. In this paper, MgB2 films were fabricated on different cathodes via the molten salts electrochemical technique. Using this method, the closed-loop joint problem which can not be settled by traditional method could be solved. The application of magnesium diboride superconductor in highfield and intense magnetic field can be improved. In addition, the sensitivity of the device can also be greatly improved, and the cost can be reduced.In the experiment, the range of electrolysis parameters was set according to the calculation of decomposition voltages and the analysis of pHase and fusibility diagram. First, the electrolytic apparatus was modified. Secondly, MgB2 films were successfully prepared on graphite, stainless steel and copper cathodes. Then, the optimal parameter for MgB2 films preparation on different substrates was obtained by adjusting the ratio of molten salt, electrolysis voltage, electrolysis temperature and pretreatment technic. At last, X-ray diffraction was adopted to investigate the crystalline properties, and growth mechanics of MgB2 film was discussed considering the experimental process and theoretical study.The results show that the crystallinity of MgB2 film is improved through the pre-electrolysis of molten salt system. The dmso and dmf with the ratio of 1:1.5 can soften and dissolve impurities that on the surface of MgB2 film. The optimal electrolysis temperature and electrolysis voltage is 598℃and 4.2V for copper substrate,608℃and 3.8V for grapHite substrate,598℃and 4.6V and molar rate of NaCl-KCl-Mg(BO)2-MgCl2 is 5:5:2:10.4 for stainless steel substrate, respectively.

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