Synthesis of High Entropy Boride Using Atomic Hydrogen Via MW-Plasma

We explore the synthesis of MoNbTaVWB₁₀ high-entropy borides (HEBs) in a reactive versus inert environments using microwave plasma. The dissociation of molecular hydrogen into atomic hydrogen allows the efficient reduction of metal oxide precursors, minimizing the loss of boron during heating. Our results demonstrate that the reactive hydrogen atmosphere promotes the formation of the hexagonal AlB2-type HEB structure at lower temperatures compared to an argon environment. X-ray diffraction analysis reveals that annealing at temperatures as low as 1750°C in hydrogen plasma produces a predominantly single-phase structure through the enhanced reducing capability of atomic hydrogen allowing for uniform crystalline structure. By comparing hydrogen and argon-rich environments, we further demonstrate, via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), the benefits of hydrogen plasma, including improved purity and consistent elemental distribution, highlighting its effectiveness in optimizing high entropy material synthesis.