Effect of buffer gas pressure on phases and size of oxide nanoparticles produced by exploding wires

The effects of Ar + 20 % mol. O₂ buffer gas and partial oxygen pressures on phase composition and mean sizes of nanosized particles of tungsten, molybdenum, iron and copper oxides obtained using exploding wires (EW) have been investigated. The buffer gas (BG) pressure increase from 0.1 to 0.3 MPa allowed increasing the mean particle size of all oxide powders while it was kept almost constant in further increasing the pressure from 0.3 to 0.4 MPa. The increase in the buffer gas pressure provided better cooling conditions for the synthesized nanosized particles, which also contained more of high-temperature Fe₂O₃, WO₃, and MoO₃ oxides. Increasing the partial pressure of oxygen from 0.02 to 0.08 MPa did not resulted in complete oxidizing of the nanoparticles because of simultaneous increasing the mean particles size and their cooling rate. The experiments showed that the minimal BG pressure required for obtaining copper and iron oxides was 0.2 MPa, whereas for tungsten and molybdenum oxides it was 0.4 MPa. The established in these work dependencies could be of fundamental meaning for developing novel process of multi-wire EW synthesis of nanoparticles and coatings from multicomponent (high-entropy) oxides