【摘要】 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）观察照示,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．更多还原

【Abstract】 MgB_s bulks were prepared by using the spherical magnesium powder（Q-Mg）and scrapping magnesium powder（X-Mg）as raw materials.The two kinds of magnesium powder were mixed respectively with amorphous boron powder with a nominal stoichiometry of MgB₂,then pressed into pellets under a pressure of 10 MPa.The pellets were sintered at 650,750 and 800℃,respectively. XRD 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.SEM observations show that the shape and size of holes are evidently correlated with the shape and size of the raw magnesium powder.DSC results indicate that the solid-solid reaction,Mg melting and liqiud-solid reaction during increasing temperature occur in turn for the X-Mg and Q-Mg series samples.However,because of the small surface area,large surface energy and low activity of the surface atom the starting temperqture of the solid-solid reaction of Q-Mg sample is 53.7℃higher than that of X-Mg sample.The results of DSC,XRD and SEM also showed that the starting temperqture of the solid-solid reaction increases,the reaction rate between Mg and B decreases at low temperature if the spherical magnesium powder was used as raw materials, but the formation and growth mechanism of MgB₂ crystals are not changed.更多还原