Carbon Doping of MgB2 by Toluene and Malic-Acid-in-Toluene

TL;DR

This study investigates how toluene and malic acid influence carbon doping in MgB2, affecting its superconducting properties, with detailed thermal analysis and measurements showing different impacts on critical fields and current densities.

Contribution

It demonstrates that toluene and malic acid contribute significant carbon to MgB2 and differentially enhance its superconducting properties, providing insights into doping mechanisms and effects.

Findings

Toluene contributes ~0.4 wt% C, malic acid contributes ~1.5 wt% C.

Toluene/malic acid doping increases Bc2.

Toluene doping yields higher Jc in most magnetic fields.

Abstract

The decomposition of malic acid in the presence of Mg and B was studied using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) which revealed that malic acid reacted with Mg but not B. Also, the addition of toluene to dissolve malic acid followed by subsequent drying resulted in no reaction with Mg, indicating that the malic acid had decomposed during the dissolution/drying stage. The total carbon contributed by toluene versus a toluene/5 wt% malic acid mixture was measured using a LECO CS600 carbon analyzer. The toluene sample contained ~0.4 wt% C while the toluene/malic acid mixture had ~1.5 wt% C, demonstrating that the toluene contributed a significant amount of carbon to the final product. Resistivity measurements on powder-in-tube MgB2 monofilamentary wires established that the toluene/malic acid doped sample had the highest Bc2. However, the toluene-only sample had the highest transport Jc over most of the magnetic field range (0-9 T), equaled only by that of toluene/malic acid sample in fields above 9 T.