• Shahbazi, Mahboobeh

Abstract

<p>This study presents a comprehensive analysis of the effects resulting from the substitution of biowaste-derived carbon-dot (CD) from human hair on structural and superconducting properties of MgB₂. Syntheses of polycrystalline samples were accomplished through a standard solid-state reaction route. X-ray powder diffraction results confirm the formation of MgB₂ as a primary phase in all samples and show the successful substitution of carbon for boron in MgB₂. The critical current density, determined at 20 K and 4.5 T, for carbon-substituted MgB₂ synthesized at 850 °C was enhanced by more than four times compared with unsubstituted MgB₂. The observed improvement is due to the formation of efficient pinning centers resulting from the incorporation of carbon substituting for boron in MgB₂. Furthermore, x-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon bonding to boron in MgB₂ synthesized with biowaste-derived CDs, indicating successful incorporation into the structure. Ultraviolet photoelectron spectroscopy (UPS) results show that the carbon-substituted MgB₂ can lead to changes in the electronic band structure and values of work function. These changes significantly impact the properties of MgB₂ materials, including superconducting transition temperature, upper critical field, and critical current density. The XPS and UPS experimental results are in good agreement with density functional theory calculations for MgB₂ with and without carbon substitution.</p>

Topics

• density
• impedance spectroscopy
• Carbon
• phase
• theory
• x-ray photoelectron spectroscopy
• density functional theory
• Boron
• current density
• band structure
• ultraviolet photoelectron spectroscopy