Superconducting performance and interface characteristics with metals of Al modified MgB2 materials
The use of MgB2 superconducting material in liquid hydrogen level sensors has problems with signifi-cant differences in critical transition temperature and liquid hydrogen liquefaction temperature and interface re-actions between the original powder and metal sheath.These problems make it difficult to measure and control the liquid hydrogen level sensors.We studied the Al doping modification technology to reduce the critical transi-tion temperature of MgB2.And we studied the effects of the interface reaction between the original powder and the metal sheath Fe,Monel and annealing temperature on its superconducting transition width.The results show that when the doping amount x=0.15,the critical transition temperature of Mg1-xAlxB2 polycrystalline sample is about 30 K,which meets the requirements for the use of liquid hydrogen level sensors.There is a dif-fusion interface between the metal sheath Fe,Monel and the precursor powder Mg,Al.The diffusion layer thickness of the Fe metal sheath sample is relatively small,approximately 25 μm.So,the Fe metal sheath is more suitable for preparing sheath materials for Al doped MgB2 superconducting wires.Fe and Monel modified MgB2 samples with metal sheaths at different annealing temperatures still exhibit significant superconducting transitions,and the superconducting transition temperature meets the operating environment of liquid hydrogen level sensors.
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