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Experimental Study on Phase Transformation Between MgB 2 and MgB 4
Author(s) -
Yan S. C.,
Yan G.,
Liu C. F.,
Lu Y. F.,
Zhou L.
Publication year - 2007
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.01664.x
Subject(s) - scanning electron microscope , differential scanning calorimetry , stoichiometry , analytical chemistry (journal) , materials science , microstructure , phase (matter) , powder diffraction , crystallography , chemistry , metallurgy , thermodynamics , composite material , physics , organic chemistry , chromatography
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.