MgB2超导线材掺杂优化与致密化机理的探索研究

MgB2 superconducting wires have large potential applications and good application prospects. The superconducting properties of MgB2 wires still have great scope for further improvement in the coming years. The main problem is the formation of many pores during the synthesis of MgB2 at ambient pressure, which limites the further improvement of superconducting properties of MgB2 wires. The pores reduce the effective current area and the boundary density as effective pinning centers. This project aims to study the preparation of MgB2 superconducting wires by stepwise synthesis. We use MgB4 as the resource of B to reduce the reaction activity of B and change the process of Mg-B diffusion reaction, and explore the new synthesis method of preparing high density MgB2 superconducting wires. The effect of element doping on the diffusion reaction is explored. The forming model of pores in MgB2 superconductor is established. The main factors on preparation of high density MgB2 superconducting wires will be revealed. It is elucidated that the reaction mechanism in order to tune the density of superconducting MgB2 wires. And based on above conclusions, the influence law of element doping on superconducting properties of MgB2 wires prepared by stepwise synthesis methode will be investigated. The results will lay the fundations on practical applications and further improve the superconducting properties of MgB2 superconducting wires.

MgB2超导线材具有巨大的应用潜力和良好的应用前景。目前，MgB2超导线材的性能仍存在很大的提升空间，限制其性能进一步提高的主要问题是在常压合成条件下MgB2中生成大量孔洞，导致有效载流面积和作为有效钉扎中心的晶界密度减小。本项目通过分步反应法制备MgB2超导线材，采用MgB4作为B源，降低B源的反应活性以改变Mg-B间扩散反应行为和过程，探索常压条件下制备高致密度MgB2超导线材的新合成方法；探索分步反应中元素掺杂对Mg-B扩散反应的影响，建立MgB2超导体中孔洞的生成模型，揭示影响生成高致密度MgB2线材的主要因素，阐明分步反应法制备高致密度MgB2的反应机制，达到对MgB2超导线材的密度调控。并在此基础上研究掺杂对分步反应法制备的MgB2超导线材性能的影响规律。相关研究对于进一步提高MgB2超导线材的性能，推动其实现实用化具有重要意义。

MgB2超导线材具有巨大的应用潜力和良好的应用前景。目前MgB2超导线材的性能仍存在很大的提升空间，限制其性能进一步提高的主要问题是在常压合成条件下MgB2中生成大量孔洞，导致有效载流面积和作为有效钉扎中心的晶界密度减小。本项目通过分步反应法制备MgB2超导线材，采用MgB4作为B源，降低B源的反应活性以改变Mg-B间扩散反应行为和过程，探索常压条件下制备高致密度MgB2超导线材的新合成方法。我们完成了Mg-B体系的成相研究，建立了反应模型，获得了该体系的成相反应规律。研究表明采用45-100 μm的屑状Mg粉末作为先驱粉末，可以得到反应完全、致密度和纯度相对较高的MgB2超导体。开展单相MgB4粉末合成实验，确定MgB4亚稳相的最佳合成条件。研究了MgB2超导粉末的两步反应制备法，确定MgB4+Mg→MgB2反应的合成参数。探索分步反应中元素掺杂对Mg-B扩散反应的影响，建立MgB2超导体中孔洞的生成模型，揭示影响生成高致密度MgB2线材的主要因素，阐明分步反应法制备高致密度MgB2的反应机制，达到对MgB2超导线材的密度调控，结果显示该方法可以较好地改善掺杂体系的反应活性，更容易将掺杂元素引入MgB2晶格。课题组采用分步反应方法制备高致密性的MgB2超导导线，利用该方法有效地提高了MgB2超导线材的芯丝致密度，在常压制备MgB2超导线材过程中，有效抑制孔洞的形成，同时通过掺杂使得超导体的磁通钉扎和Jc性能达到最优化。相关研究将为常压制备in-situ PIT法MgB2超导线材的新技术提供理论和实验基础，对于进一步提高MgB2超导线材的性能，推动其实现实用化具有重要意义。