Commercial MgB₂ powder manufactured by Alfa Aesar was mechanically sieved in order to obtain powder samples with different particle size. As-sieved powders were used for single-core wires with FeNiCo sheath made by ex-situ process and heat treated at the same conditions, 950 °C/30 min. Resistive transitions of extracted MgB₂ cores allowed to obtain the critical temperature and normal state resistivity for different particle size and estimate the connectivity by the Rowell approach. In field critical currents were also affected by the particle size of sieved MgB₂ powder. The highest current densities were measured for the wire with particles 15-25 µm, which is explained by the dominant effect of grain-boundary pinning.

将由Alfa Aesar制造的商品MgB ₂粉末进行机械筛分，以获得具有不同粒径的粉末样品。筛分后的粉末用于通过非原位工艺制成的带有FeNiCo护套的单芯线，并在950°C / 30分钟的相同条件下进行热处理。提取的MgB ₂核的电阻跃迁允许获得针对不同粒径的临界温度和正常状态电阻率，并通过Rowell方法估算连通性。在现场，临界电流也受到筛分的MgB ₂粉末粒径的影响。对于颗粒尺寸为15-25 µm的导线，测量出的电流密度最高，这可通过晶界钉扎的主要作用来解释。