The kinetic analysis of formation behavior for the MgB2 phase
The kinetic analysis of formation behavior for the MgB2 phase
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DOI：
10.1016/j.jallcom.2006.11.133
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发表时间：
2007-09
影响因子：
6.2
通讯作者：
S. Yan;Yafeng Lu;Guoqing Liu;G. Yan;Lian Zhou
中科院分区：
文献类型：
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作者：
S. Yan;Yafeng Lu;Guoqing Liu;G. Yan;Lian Zhou
用差示扫描量热法(DSC)和X射线衍射法(X射线衍射仪)研究了用有盖和无盖两种氧化铝坩埚(记为样品A)和无盖(记为样品B)的Mg-B系统的物相组成。采用5、10、15和20°C/min的升温速率对1：2的混合粉末进行了DSC测试。样品A的DSC曲线表明，随着温度的升高，Mg-B体系经历了固-固、镁熔化和液-气-固三种过程。但样品B的DSC结果显示了镁熔化、液-气-固反应以及可能的氧化过程的三个变化。在类似于DSC过程的烧结实验中，进一步研究了样品A和B之间的差异。对烧结体的X射线衍射分析表明，在镁气氛中，镁与B反应生成了镁B2。用Ozawa-Flynn-Wall和Kisinger方法计算了Mg-B体系固-固反应的活化能，计算值分别为58.18和72.75kJ/mol。指前因子的计算值为2.0×10~(15)S·−~(-1)。E值较小，表明镁和B之间容易发生反应生成镁B_2。
By using differential scanning calorimetry (DSC) and X-ray diffraction (XRD), we have investigated the phase formation for the Mg–B system, where two kinds of alumina crucible, with a cover (denoted as sample A) and without cover (denoted as sample B), were used during measurements. Heating rates of 5, 10, 15 and 20°C/min were employed in the DSC measurement for the mixed powder of Mg:B=1:2. The DSC curves of sample A show that the Mg–B system undergoes three kinds of process; solid–solid, Mg melting, and liquid–gas–solid reaction with increasing temperature. But the DSC results of sample B present three changes of Mg melting, liquid–gas–solid reaction, and a possible oxidation process of MgB2. The difference between samples A and B was further investigated in a sintering experiment similar to the DSC process. The XRD analysis for the sintered samples indicates that the reaction between Mg and B to form MgB2occurs easily in the Mg atmosphere. The activation energy of the solid–solid reaction for the Mg–B system was calculated by using the Ozawa–Flynn–Wall and Kissinger methods, and the calculated values are 58.18 and 72.75kJ/mol, respectively. The calculated value of the pre-exponential factor is 2.0×1015S−1. The relatively small value of E indicates that the reaction between Mg and B to form MgB2occurs easily.