Laser Induced Dielectric Breakdown as a Novel Method for the Synthesis of Molybdenum Boride

Laser induced dielectric breakdown (LIDB) on a surface of solid Mo in H 2 /BF 3 atmosphere at 30–760 Torr and in a gaseous mixture MoF 6 /H 2 /BF 3 + at 760 Torr pressure is tested for synthesis and deposition of superhard molybdenum borides that are needed in many areas of industry and technology. The emission spectra of the plasma and the dynamics of the gas discharge near the substrate are investigated. A comparative analysis of the gas mixture before and after exposure to LIDB plasma is carried out using IR spectroscopy. The conditions for the formation of molybdenum borides are determined. A thermodynamic analysis of the MoF 6 /H 2 /BF 3 and Mo/H 2 /BF 3 systems is carried out to determine the temperature range for the formation of molybdenum borides and establish the main chemical reactions responsible for their formation. Deposits containing MoB and MoB 2 phases are obtained. For the mixture MoF 6 /H 2 /BF 3 , the deposit exhibits an amorphous layered structure, which contains 19.15 wt% F, 30.45% O, and 0.8% Si. For the Mo/H 2 /BF 3 system at the pressures 30 and 160 Torr, nanopowder of molybdenum boride is produced with a characteristic grain size of 100 nm. At pressures above 160 Torr, Mo nanopowder with a grain size