采用球形Mg粉(Q-Mg)、屑状Mg粉(X-Mg)和无定形B粉, 按照MgB2的化学计量比充分混合后, 在10 MPa的压力下压制成块材, 分别在650, 750和800℃下进行烧结. X射线衍射(XRD)结果表明, Q-Mg样品的成相速率远低于X-Mg样品.扫描电镜(SEM)观察显示, 样品中的孔洞形状和尺寸依赖于初始Mg粉的形状和尺寸. 差示扫描量热法(DSC)研究结果显示, 两类样品在升温过程中, 均先后发生了固--固反应、Mg熔化以及液-固反应. 但是, 由于球形粉末表面积较小, 表面能较大, 且表面原子活性较差, 导致了Q-Mg样品的固-固反应起始温度比X-Mg样品高出53.7℃. 基于DSC, XRD和SEM研究结果可知, 球形Mg粉提高了固-固反应温度并延缓了低温下的Mg-B反应速率, 但不改变MgB2晶体的形成和生长机制.
The MgB2 bulks were prepared using the spherical magnesium powder (denoted as Q-Mg) and scrapping magnesium powder (denoted as X-Mg) as raw materials. The two kinds of magnesium powder were mixed with amorphous boron powder with a nominal stoichiometry of MgB2, then pressed into pellets under a pressure of 10MPa. The pellets were sintered at 650℃，700℃，750℃ and 800℃ respectively. The X-ray diffraction analysis results for the sintered samples show that the phase formation rate of Q-Mg series samples is lower than that of X-Mg series samples. The differential scanning calorimetry (DSC) results indicate that the solid-solid reaction , Mg melting and liqiud-solid reaction during the temperature increasing occur in turn at 527.1℃，650.7℃ and 660.8℃ for the X-Mg series samples, but for the Q-Mg series samples, the Mg melting and liqiud-solid reaction occur in turn at 640.9℃ and 712.3℃.
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