In:
Journal of Materials Research, Springer Science and Business Media LLC, Vol. 23, No. 7 ( 2008-07), p. 1840-1848
Abstract:
Differential thermal analysis, as the main means of measurement, was used to prepare bulk MgB 2 samples and monitor the sintering reaction process. Combined with microstructure observation by scanning electron microscopy and x-ray diffraction analysis, the formation process of MgB 2 phase at the temperature before Mg melting was summarized. Additionally, a new kinetic analysis (a variant on the Flynn–Wall–Ozawa) method under nonisothermal conditions was used to determine that the reaction between Mg and B powders involves random nucleation followed by an instantaneous growth of nuclei (Avrami–Erofeev equation, n = 2), which can properly explain the in situ formation process of bulk MgB 2 at the temperature before Mg melting. The value of activation energy E and the function of conversion f (α) are obtained independently, and thereby the determination of mechanism function is not affected by the value of E . The values of E decrease from 175.418 to 160.395 kJ mol −1 with the increase of the conversion degrees (α) from 0.1 to 0.8. However, as the conversion degrees approach 0.9, the value of E increases to 222.647 kJ mol −1 , and the corresponding pre-exponential factor A is about three orders of magnitude larger than the previous ones.
Type of Medium:
Online Resource
ISSN:
0884-2914
,
2044-5326
DOI:
10.1557/JMR.2008.0229
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2008
detail.hit.zdb_id:
54876-5
detail.hit.zdb_id:
2015297-8
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