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Experimental Study on Phase Transformation Between MgB 2 and MgB 4

2007; Wiley; Volume: 90; Issue: 7 Linguagem: Inglês

10.1111/j.1551-2916.2007.01664.x

1551-2916

Shicheng Yan, Yan Guo, C. F. Liu, Y.F. Lu, Liucheng Zhou,

Magnesium Alloys: Properties and Applications

Using X‐ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC), we have investigated the reaction between MgB 4 and Mg in its solid, liquid, and gas physical states. The XRD results indicate that the reaction of MgB 4 +Mg=2MgB 2 always occurs independently of the different states of Mg. DSC measurements show that the solid–solid reaction MgB 4 ( s )+Mg( s )=2MgB 2 ( s ), the Mg melting Mg( s )→Mg( l ), and the Mg volatilization occur in turn with increasing temperature for mixed (MgB 4 +Mg) powder with a nominal stoichiometry of MgB 2 . SEM observations indicate that the resulting synthesized MgB 2 samples, obtained from the MgB 4 +Mg mixtures, have a denser microstructure than those obtained directly from Mg+B mixtures. On the basis of XRD, DSC, and SEM results, a kinetic model for the reaction between MgB 4 and Mg is proposed.