Critical current density, J c , in superconductors is strongly connected with size of defects in the material. Frequently, the smaller defects, the higher J c . In this work, we tried to reduce the size of cheap commercial boron precursor powder using high energy ultra-sonication in ethanol media. The resulting powder was then utilized in synthesizing bulk MgB 2 via sintering at 775 °C. Effect of boron powder ultra-sonication on superconducting properties of the bulk MgB 2 was studied and discussed. SEM of ultra-sonicated boron showed fine particles with sharp edges (high-energy surfaces), irregular shapes and clustering of fine particles occurred for longer ultra-sonication durations. XRD proved a high quality of MgB 2 with only small traces of MgO. Around 36% improvement in J c at 20 K and T c close to 39 K were observed in MgB 2 bulk prepared with boron ultra-sonicate...

中文翻译：

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通过高功率超声减小硼颗粒的尺寸以优化块状MgB 2

超导体中的临界电流密度J c与材料中缺陷的大小密切相关。通常，缺陷越小，J c越高。在这项工作中，我们试图通过在乙醇介质中使用高能超声来减小廉价的商业化硼前驱体粉末的尺寸。然后将所得粉末用于通过在775°C下烧结来合成块状MgB 2。研究和讨论了硼粉超声处理对块状MgB 2超导性能的影响。超声波处理的硼的SEM观察到细颗粒具有锋利的边缘（高能表面），不规则的形状和细颗粒的聚集发生在较长的超声波处理期间。XRD证明了MgB 2的质量很高，只有少量的MgO。