Mechanochemical synthesis and characterisation of niobium silicide nanoparticles

Abstract

Abstract Mechanochemical synthesis (MCS) investigations of niobium silicide powders in Nb2O5 SiO2 Mg powder mixtures were conducted via high-energy ball milling and leaching by means of process parameters such as the milling duration, initial Nb2O5 crystal structure, and excess Mg amount. The compositional, thermal, and microstructural properties of the products were characterised using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), particle size analysis (PSA), stereomicroscopy (SM), scanning electron microscopy (SEM), and transmission electron microscopy/energy-dispersive spectrometry (TEM/EDS). After the 5 h milling of the stoichiometric mixtures, an instantaneous ignition occurred and NbSi2, Nb5Si3, Nb, and MgO phases formed with some residual Mg. In addition, the use of excess Mg inhibited the formation of Nb5Si3. Afterwards, leaching treatments (in a 4 M HCl solution) completely removed the Mg-based phases from the synthesised products. The XRD calculations revealed that the resultant product consisted of 97 wt% NbSi2 and 3 wt% Nb5Si3 phases. The TEM analyses indicated that each Nb silicide nanoparticle was coated with a SiO2 layer. According to random measurements, the average particle size of the Nb silicide cores and average thickness of the SiO2 layer were approximately 61 and 7.5 nm, respectively.