Oxidation in air between ambient and 1000C was studied by thermogravimetry, X-ray diffraction and scanning electron microscopy with energy dispersion spectrometry. The results showed that the obvious oxidation process began at about 400C and became very strong when the temperature exceeded 700C. The X-ray diffraction showed that, after oxidation for a long time at high temperatures, most of the Mg became MgO. Analysis of the microstructure showed that the oxidation of MgB2 was a very complex process which was accompanied by the evaporation of B and Mg and the formation of MgO. Long MgO whiskers, with diameters of nm-scale, also appeared; mostly at the grain surface, due to the reaction of evaporated Mg with O. The oxidation activation energy of MgB2 was estimated by using the Freeman–Carroll method, based upon the Arrhenius equation. It was shown that, in the range of strong oxidation temperatures, the activation energy was 70 to 90kJ/mol.

Experimental Study on the Oxidation of MgB2 in Air at High Temperature. D.Yang, H.Sun, H.Lu, Y.Guo, X.Li, X.Hu: Superconductor Science and Technology, 2003, 16, 576-81