MgB2的转变温度高，制备成本低，通过化学掺杂引入杂质相钉扎中心提高其临界电流密度水平，可使其满足在低磁场下磁共振成像领域的应用。然而，固相掺杂面临着过量掺杂剂聚集在晶粒间阻碍电流传输的问题。预实验结果表明，在氢气气氛下烧结MgB2，氢诱导MgB2晶粒中析出了氢化物Mg(BH4)2，同时过量的氢气可从材料中逸出，实现了“纯净”掺杂和高磁场下临界电流密度的初步提高。因此，本项目围绕“气体掺杂”的理念，利用Mg、B和MgB2的储氢行为，发展氢掺杂MgB2的制备技术。在分析氢化物形成的热力学条件及氢气气氛下MgB2成相的动力学机制的基础上，依靠氢压调控氢化物/MgB2复合组织，获得纳米级氢化物弥散分布在MgB2晶粒中的有利组织，制备高临界电流密度的氢掺杂MgB2材料，并澄清氢化物作为钉扎中心的机理。项目的实施对推进MgB2材料在高磁场下应用具有重要意义，也为超导材料的设计提供科学依据。

MgB2 with high transition temperature and low preparation cost is mainly used in the low-field magnetic resonance imaging. As a candidate to replace the conventional low-temperature superconductors for low refrigeration cost, chemical doping is commonly employed to introduce impurities as pinning centers and to improve the critical current density. However, excess dopants normally aggregate at the grain boundaries to obstruct the current transmission in the case of solid-state doping. Preliminary experiments have shown that Mg(BH4)2 hydrides were induced to precipitate within MgB2 grains when the samples were sintered in H2 atmosphere, and excess H2 could escape from the sample to realize “clean” doping and the enhancement of critical current density. In this regard, the pinning mechanism and the effect of hydrides on the critical current density are required to be investigated. Hence, the concept of gas doping is used in this project. Considering the hydrogen storage behavior of Mg, B, and MgB2, hydrogen is employed to dope MgB2 by in situ or ex situ synthesis techniques. Based on the thermodynamic and kinetics analyses, the formation mechanism of MgB2 and hydrides is investigated, and the complex structure of hydrides/MgB2 is regulated by tuning the H2 pressure. The ideal H-doped MgB2 superconductors contain nanoscale hydrides that finely dispersed in the MgB2 matrix, and the critical current density is expected to be enhanced, due to the flux pinning effects of these hydrides. The fabrication of high-performance H-doped MgB2 superconductors is conducive to the high-field application of MgB2. The relationship among H2 condition, microstructure, and superconducting properties could provide guidance for the design of superconducting materials.