Molybdenum oxide micro- and nanorods: structure and thermal properties dependent on perturbation during synthesis

Molybdenum oxide micro- and nanoparticles were synthesized conventionally and under ultrasound perturbation (ultrasound-assisted syntheses). X-ray diffraction (XRD), vibrational infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used to characterize the structure, thermal properties and morphology of the samples. XRD analyses evidenced the formation of the metastable hexagonal phase, independently of the perturbation during synthesis while, after calcination at 600 °C, crystalline structure was converted to the most thermodynamically stable phase, α orthorhombic. FTIR results suggested an increasing number of interacting structures involving water molecules, with different interaction energies, which was corroborated by DSC analyses, showing an increasing number of evaporation processes, as a function of perturbation during synthesis. SEM analyses confirmed the formation of hexagonal rods, with diameter ranging in the nanometer scale, for low-temperature samples, while calcined ones exhibited a predominantly belt morphology.