کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
7718478 | 1497485 | 2014 | 14 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Nanocrystalline β-γ-β cyclic phase transformation in reacted ball milled MgH2 powders
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
الکتروشیمی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Nanocrystalline β-γ-β cyclic phase transformation in reacted ball milled MgH2 powders Nanocrystalline β-γ-β cyclic phase transformation in reacted ball milled MgH2 powders](/preview/png/7718478.png)
چکیده انگلیسی
Pure magnesium powders were ball milled under a hydrogen pressure of 50 bar at room temperature, using reactive ball milling (RBM) approach. The results have shown that a single stable phase of β-MgH2 is obtained upon RBM for 25 h. Increasing the RBM time leads to a significant decreasing on the grain size and an increase in the iron contamination that were introduced to the powders upon using hard steel milling tools. Remarkable changes in the transformed mass fractions of β-MgH2 phase to a metastable γ-MgH2 phase with increasing the RBM time could be detected. Cyclic β-γ-β phase transformations were observed several times upon changing the RBM time. After 200 h of RBM time, the decomposition temperature and activation energy were recorded to be 399 °C and 131 kJ/mol, respectively. Moreover, the times required for complete absorption and desorption of 7 wt.% of hydrogen at 250 °C were recorded to be 3140 s and 35,207 s under 10 and 0 bar, respectively. At 300 °C, the powders that were obtained upon RBM time for 200 h possess excellent hydrogenation properties for any pure MgH2 system, indexed by high hydrogen storage capacity (7.54 wt.%) with complete 600 absorption/desorption cycles. Improvements of hydrogenation/dehydrogenation kinetics are attributed to the presence of γ-phase, the existence of Fe contamination and the nanocrystallinity of the ball milled powders.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Hydrogen Energy - Volume 39, Issue 24, 13 August 2014, Pages 12727-12740
Journal: International Journal of Hydrogen Energy - Volume 39, Issue 24, 13 August 2014, Pages 12727-12740
نویسندگان
M. Sherif El-Eskandarany, Ehab Shaban, Badryiah Al-Halaili,