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KMID : 1102020170470030110
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Applied Microscopy
2017 Volume.47 No. 3 p.110 ~ p.120
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Evaluation of Kinetic Parameters and Thermal Stability of Melt-Quenched BixSe100?x Alloys (x ≤7.5 at%) by Non-Isothermal Thermogravimetric Analysis
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Ahmad Mais Jamil A.
Jafar Mousa M. Abdul-Gader
Saleh Mahmoud H.
Shehadeh Khawla M.
Ziq Ahmad Telfah, Khalil A.
Hergenroder Roland
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Abstract
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Non-isothermal thermogravimetry (TG) measurements on melt-quenched BixSe100?x specimens (x=0, 2.5, 7.5 at%) were made at a heating rate β=10°C/min in the range T=35°C~950°C. The as-measured TG curves confirm that BixSe100?x samples were thermally stable with minor loss at T?400°C and mass loss starts to decrease up to 600°C, beyond which trivial mass loss was observed. These TG curves were used to estimate molar (Se/Bi)-ratios of BixSe100?x samples, which were not in accordance with initial composition. Shaping features of conversion curves α(T)?T of BixSe100?x samples combined with a reliable flow chart were used to reduce kinetic mechanisms that would have caused their thermal mass loss to few nth-order reaction models of the form f[α(T)] [1?α(T)]n (n=1/2, 2/3, and 1). The constructed α(T)?T and (dα(T)/dT)?T curves were analyzed using Coats-Redfern (CR) and Achar-Brindley-Sharp (ABS) kinetic formulas on basis of these model functions, but the linearity of attained plots were good in a limited α(T)?region. The applicability of CR and ABS methods, with model function of kinetic reaction mechanism R0 (n=0), was notable as they gave best linear fits over much broader α(T)-range.
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KEYWORD
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Non-isothermal kinetics, Thermogravimetric analysis, Coats-Redfern kinetic model, Achar-Brindley-Sharp kinetic model, Bismuth-selenium alloys
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