MgB₂超导材料合成工艺研究

【作者】 黄勇；

【导师】 刘心宇；

【作者基本信息】 中南大学 ， 材料加工工程， 2005， 硕士

【摘要】 本研究分别采用机械合金化和固相反应法,以粉末冶金为路线的方法,制备了MgB₂以及掺杂不同稀土（Y,Pr）含量的稀土-MgB₂超导材料,对MgB₂的合成工艺进行了深入系统研究。借助于现代分析检测仪器,对Mg-B混合粉末的机械合金化和固相反应合成以及材料的烧结工艺、氧化行为、二次烧结工艺、微量稀土掺杂对MgB₂结构的影响进行了深入系统的研究。研究结果表明:采用原子配比为Mg∶B=1∶2的混合粉末在进行球磨,完全可以获得微晶甚至于非晶的MgB₂粉末。MgB₂的机械合金化机理主要为扩散固溶。球料比对于MgB₂的合成有明显的影响,当采用玛瑙球进行球磨时,球料比为20∶1,装罐量为罐容量的1/2时较易形成MgB₂。在保持球料的体积比不变的情况下,采用质量大的不锈钢球代替玛瑙球,可以提高球磨时的撞击能量,大大加速MgB₂的形成。采用固相烧结法制备MgB₂超导块材,在制备过程中必须防止保温过程中Mg的氧化和挥发以及高温时MgB₂的分解。合成过程必须在保护气氛下或者真空状态中进行。在氩气流保护气氛下Mg∶B=1∶1.5,800℃下保温2h是最佳的合成条件。在密封石英管中,Mg∶B=1∶1.95,800℃下保温1h是最佳的合成条件。通过二次烧结可提高材料的致密度。微量稀土掺杂在MgB₂中形成固溶体,对MgB₂结构没有太大影响。适当的稀土含量可以提高块材的致密度。更多还原

【Abstract】 MgB₂ and RE-MgB₂ superconductive materials were produced by means of mechanical alloying and solid sintering reaction respectively. The processes mechanical alloying and solid reaction synthesis in the Mg-B system and sintering technology, oxidation behavior and the effect of rare earth doping on MgB₂ were investigated systematically by means of SEM and X-ray diffraction technique.Some microcrystalline and amorphous MgB₂ can be achieved in the Mg-B binary system （Mg:B=1 :2） induced by mechanical alloying （MA）. The formation mechanism of MgB₂ by MA is diffusion solution. The speed of mechanical alloying were different under different ball milling conditions such as the quality’s rate of ball to powder, the milling time, the kinds of ball. The quality’s rate of ball to powder is a decisive factor. Protecting Mg volatility and oxidized at elevated temperature and avoid MgB₂ decomposing at high temperature are the key factor of formation MgB₂ by solid-state sintering reactions, so the sintering must process under protect gas or vacuum. The sample which was prepared by mixed Mg and B with a atom ratio of Mg:B=1:1.5 must be held at 800℃ for 2h in a flowing atmosphere of Ar. However, to vacuum seal the sample which was prepared by mixed Mg and B with a atom ratio of Mg:B=1: 1.95 in a quartz , then held the sample at 800℃ for 1h is another synthesis method. The product must be powdered, compacted and reheated, and the density of MgB₂ can be raised. The additives of the rare earth （Y, Pr） were solution phase in MgB₂ and have not evident effect on MgB₂!s microstructure. The additives of the rare earth increase the density of the sintered MgB₂.更多还原