• Shahbazi, Mahboobeh

Abstract

We demonstrate synthesis of the ternary intermetallic MgNi<sub>3</sub>B<sub>2</sub> using autogenous pressure from the reaction of NaBH<sub>4</sub> with Mg and Ni metal powder. The decomposition of NaBH<sub>4</sub> to H<sub>2</sub> and B<sub>2</sub>H<sub>6</sub> commences at low temperatures in the presence of Mg and/or Ni and promotes formation of Ni-borides and MgNi<sub>3</sub>B<sub>2</sub> with the increase in temperature. MgNi<sub>3</sub>B<sub>2</sub> aggregates with Ni-boride cores are formed when the reaction temperature is >670 °C and autogenous pressure is >1.7 MPa. Morphologies and microstructures suggest that solid–gas and liquid–gas reactions are dominant mechanisms and that Ni-borides form at a lower temperature than MgNi<sub>3</sub>B<sub>2</sub>. Magnetic measurements of the core-shell MgNi<sub>3</sub>B<sub>2</sub> aggregates are consistent with ferromagnetic behaviour in contrast to stoichiometric MgNi<sub>3</sub>B<sub>2</sub> which is diamagnetic at room temperature.<

Topics

• impedance spectroscopy
• microstructure
• nickel
• Magnesium
• Magnesium
• intermetallic
• boride
• decomposition