The Comparison of Graphene and Reduced Graphene Oxide Added to MgB2 Prepared by Diffusion Method

The key to improve the application of MgB
₂
is to improve its critical current density Jc at high magnetic fields. The graphene and reduced graphene oxide (rGO) are added to MgB
₂
bulks to contribute to the flux pinning and Jc improvement. Graphene and rGO are added in the ratio of C:B = x:1-x, in which x = 0-5 wt% to the MgB
₂
bulks. The effects of the graphene and rGO addition on the superconducting properties of MgB
₂
bulks are investigated. The dense and uniform MgB
₂
bulks are obtained by diffusion method with the addition of graphene and rGO. The superconducting transition temperature Tc decreases with increasing graphene and rGO addition. The Tc of the rGO-added sample declines more dramatic than that of the graphene-added sample. The addition of graphene and rGO (in the ratio C:B = x:1-x, where x = 1-5 wt%) to the MgB
₂
shows the improved Jc at whole range of magnetic fields compared with the no-added MgB
₂
sample, except for the MgB
₂
sample with 5 wt% of rGO addition. The sample with 1 wt% rGO addition exhibits the highest Jc value, which is attributed to the improvement of intergrain connectivity and flux pinning caused by appropriate amount of rGO addition. However, nonsuperconducting phase MgB
₂
C
₂
appears and MgO content increases in the MgB
₂
bulk samples with 5 wt% rGO addition, which result in the reduction in Jc.