Synthesis of MgB₂ at Low Temperature and Autogenous Pressure

Ian D R Mackinnon; Abigail Winnett; Jose A Alarco; Peter C Talbot

doi:10.3390/ma7053901

Synthesis of MgB₂ at Low Temperature and Autogenous Pressure

Materials (Basel). 2014 May 15;7(5):3901-3918. doi: 10.3390/ma7053901.

Authors

Ian D R Mackinnon¹, Abigail Winnett², Jose A Alarco^{3

4}, Peter C Talbot^{5

6}

Affiliations

¹ Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4001, Australia. ian.mackinnon@qut.edu.au.
² Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4001, Australia. a.winnett@qut.edu.au.
³ Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4001, Australia. jose.alarco@qut.edu.au.
⁴ Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia. jose.alarco@qut.edu.au.
⁵ Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4001, Australia. p.talbot@qut.edu.au.
⁶ Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia. p.talbot@qut.edu.au.

Abstract

High quality, micron-sized interpenetrating grains of MgB₂, with high density, are produced at low temperatures (~420 °C < T < ~500 °C) under autogenous pressure by pre-mixing Mg powder and NaBH₄ and heating in an Inconel 601 alloy reactor for 5-15 h. Optimum production of MgB₂, with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.0 MPa, with the reactor at ~500 °C. Autogenous pressure is induced by the decomposition of NaBH₄ in the presence of Mg and/or other Mg-based compounds. The morphology, transition temperature and magnetic properties of MgB₂ are dependent on the heating regime. Significant improvement in physical properties accrues when the reactor temperature is held at 250 °C for >20 min prior to a hold at 500 °C.

Keywords: magnesium diboride synthesis; sodium borohydride; superconductivity.