The doping effect of multiwall carbon nanotube on MgB2/Fe superconductor wire

TL;DR

This study investigates how multiwall carbon nanotubes with different aspect ratios affect the microstructure and superconducting properties of MgB2/Fe wires, revealing that short CNTs enhance critical current density and flux pinning.

Contribution

It provides new insights into the doping effects of CNTs with different aspect ratios on MgB2 superconductors, highlighting the potential of short CNTs for improved performance.

Findings

Short CNT doping increases Jc at high fields and temperatures.

High-temperature sintering enhances Tc for long CNT doped samples.

Nanosized MgO particles and C substitution improve flux pinning.

Abstract

We evaluated the doping effect of two types of multiwall carbon nanotube (CNT) with different aspect ratios on MgB2/Fe monofilament wires. Relationships between microstructure, magnetic critical current density (Jc), critical temperature (Tc), upper critical field (Hc2), and irreversibility field (Hirr) for pure and CNT doped wires were systematically studied for sintering temperature from 650oC to 1000oC. As the sintering temperature increased, Tc for short CNT doped sample slightly decreased, while Tc for long CNT doped sample increased. This indicates better reactivity between MgB2 and short CNT due to its small aspect ratio and substitution of carbon (C) from short CNT for boron (B) occurs. In addition, short CNT doped samples sintered at the high temperatures of 900oC and 1000oC exhibited excellent Jc, and that value was approximately 104 A/cm2 in fields up to 8 T at 5 K. This suggests that short CNT is a promising carbon source for MgB2 superconductor with excellent Jc. In particular, inclusion of nanosized MgO particles and substitution of C into the MgB2 lattice could result in strong flux pinning centers.