Enhancing superconducting performance and microhardness of bulk MgB2 through novel melamine doping

This study investigates the effect of melamine (C3H6N6), a novel carbon-based compound, on the superconducting and mechanical properties of MgB2. Samples were synthesized using the composition 1 Mg + 2B + x(C3H6N6), with x ranging from 0 to 0.0050 g. X-ray diffraction analysis confirmed that melamine successfully introduced carbon into the MgB2 lattice, resulting in a slight reduction in the a and c lattice parameters. Despite these structural modifications, both doped and undoped MgB2 samples exhibited a consistent superconducting transition temperature (Tc) of around 37.7 K. The critical current density (Jc), calculated using Bean's critical state model, increased from 246 to 332 kA/cm2 at 20 K in self-field conditions, when the melamine content reached 0.0035 g. Vickers microhardness tests revealed a reverse indentation size effect, indicating increasing hardness with higher applied loads. The optimal melamine concentration of 0.0035 g, combined with homemade nano boron, achieved the highest Jc of 720 kA/cm2 at 10 K. These findings demonstrate the potential of melamine-doped MgB2 for enhanced performance, reinforcing its promise for a wide range of industrial applications.