Synthesis of Dimolybdenum Pentaboride Nanoparticles via Reaction of Amorphous Boron with Molybdenum in Ionic Melts

A new technique has been developed for the synthesis of dimolybdenum pentaboride nanoparticles via reaction between molybdenum powder and amorphous boron in the molar ratio 2 : 5 after mechanochemical activation in argon. The reaction was run in ionic salt melts with various compositions at temperatures of 750, 800, and 850°C in a hydrogen atmosphere. Using X-ray diffraction, X-ray energy spectrometry, simultaneous thermal and elemental analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and specific surface area measurements, we demonstrate that the use of ionic melts makes it possible to obtain nearly spherical single-phase Mo₂B₅ particles ~30 nm in average diameter only at a reaction time of at least 28 h. The particles have a rhombohedral structure with unit-cell parameters a = 0.3007–0.3015 nm and с = 2.090–2.095 nm.