High temperature heat treatment of B precursor and P.I.T. process optimization to increase Jc performances of MgB2-based conductor

TL;DR

This study optimizes the PIT process for nano-sized boron powders produced via magnesiothermic reaction to enhance the critical current density (Jc) in MgB2 conductors, addressing manufacturing challenges and improving material properties.

Contribution

It introduces a new boron preparation method and optimized PIT process, including crystallization and lubrication techniques, to improve MgB2 conductor performance.

Findings

Improved crystallinity of boron powder enhances Jc.

Lubrication with magnesium reduces friction during cold working.

Optimized process yields better mechanical and superconducting properties.

Abstract

Promising results reported in our previous works led us to think that production of B powder plays a crucial role in MgB2 synthesis. A new method for boron preparation has been developed in our laboratory. This particular process is based on magnesiothermic reaction (Moissan process) with the addition of an initial step that gives boron powder with nano-metric grain size. In this paper we report our efforts regarding optimization of PIT method for these nanometric powders and the resolution of problems previously highlighted such as the difficulty in powder packaging and the high friction phenomena occurring during cold working. This increases cracking during the tape and wire manufacturing leading to its failure. Packaging problems are related to the amorphous nature of boron synthesized in our laboratory, so a crystallization treatment was applied to improve crystallinity of B powder. To prevent excessive friction phenomena we synthesized non-stoichiometric MgB2 and using magnesium as lubricant. Our goal is the Jc improvement, but a global physical-chemical characterization was also made to analyze the improvement given by our treatments: this characterization includes X-ray diffraction, resistivity vs. temperature measurement, SEM image, besides magnetic and transport Jc measurements.