中文摘要：

采用X射线衍射仪，扫描电镜，超导量子干涉仪等仪器对纳米C和SiC掺杂的MgB2带材进行了表征，并采用标准四引线法对样品的临界电流进行了测试。实验表明，C和SiC掺杂在提高MgB2带材高场下的临界电流密度方面具有显著效果。在温度为4．2K、磁场大于9T条件下，C和SiC掺杂样品的临界电流密度与未掺杂样品相比均提高一个数量级以上，掺杂样品高磁场下良好的临界电流性能主要归因于c对B的替代所产生的晶格畸变、位错等缺陷和局部成分变化而导致的有效晶内钉扎作用。实验结果表明，SiC掺杂的MgB2带材之所以具有非常好的高场电流特性，和C掺杂的样品一样，C对B的替代起到十分关键的作用。

英文摘要：

Nanoscale C and SiC doped MgB2 tapes were prepared by the in situ powder-in-tube method. The samples were characterized using X-ray diffraction, scanning electron microscope, superconducting quantum interference device magnetometer etc. Transport Jc and its magnetic field dependence were evaluated by a standard four-probe technique. It is found that Jc for all the C and SiC doped tapes was significantly enhanced in magnetic fields up to 14 T compared to the undoped ones. For the 5% C and SiC doped samples, at 4.2 K and 10 T, Jc increased by a factor of 32 and 26, respectively. The improvement of Jc-B properties in C and SiC doped MgB2 tapes is attributed to good grain linkage and the introduction of effective flux pining centers with the doping. Furthermore, our results clearly prove that the observed positive effects after mixing with SiC are nothing else than the result of the decomposition of this compound and substitution of carbon for B in MgB2.