二元金属间化合物MgB2因其简单的化学组成和优异的物理性能受到了世界各国科学家的关注。由于缺少有效的磁通钉扎中心，MgB2的临界电流密度随着磁场强度的增加而急剧减小。近些年来的研究证实，金属掺杂可以在晶体内部形成第二相纳米颗粒，使其作为有效的磁通钉扎中心，进而提高了MgB2的载流能力。人们试图减小金属颗粒的尺寸，即通过金属纳米颗粒掺杂期望在超导样品内部获得更多纳米级的第二相颗粒。据此，本项目提出一种制备Ni纳米颗粒的新方法，即在B基体上对NiO进行原位还原制备金属Ni纳米颗粒。通过掺杂实验研究微观组织结构和超导性能之间的关系，进一步澄清第二相纳米颗粒的形成机制。在此基础上，以Ni纳米颗粒作为催化剂，采用化学气相沉积法在B基体上沉积单质碳。通过研究碳产率、形态及结构的变化规律，完善碳掺杂机制。结合纳米C和Ni共同掺杂MgB2样品的结构和超导性能分析，进一步探索双重掺杂的机理和有效性。

The discovery of superconductivity at 39 K in the binary intermetallic compound MgB2 has evoked worldwide attention because of its simple chemical composition and superior properties. However, the current carrying capability of pure MgB2 sintered at ambient pressure is largely limited by the increase of magnetic fields due to the weak flux pinning. In the past years, metal doping has evoked tremendous interest in fabricating high quality MgB2 tapes and wires by formation of secondary phase nanoparticles as the effective flux pinning centers. Moreover, it is suspected that the metallic nano-particle doping has aroused considerable interest in expect of successfully inducing more nanoparticle in the MgB2 matrix. In this study, a novel experimental approach for efficient Ni doping on the nanoscale via reduction of NiO in the B matrix will be developed, and the corresponding microstructure characteristics and superconducting properties of MgB2 sample will be thoroughly studied. Based on the formation kenitics of the secondary phase nanoparticles in the Ni-doped MgB2 superconducting materials, carbon will be also doped into MgB2 over Ni catalyst by chemical vapor deposition (CVD). The influences of CVD technics on the carbon yield, morphology and structure will be further investigated. According to discuss the possible relationship between the microstructure and the superconducting properties, the detailed mechanism of coaction of C and Ni doping of MgB2 will be probed. .