Synthesis and characterization of Mo-W co-doped VO_2(R) nano-powders by the microwave-assisted hydrothermal method

摘要

Mo-W co-doped VO_2(R) nano-powders were successfully synthesized by reducing V_2O_5 with oxalic acid via a microwave-assisted hydrothermal method. Pure nano-crystals of VO_2(R) powders were obtained by adding a proper amount of urea as precipitant at a relatively low-temperature (190 °C) and within a short time (3 days). Ammonium molybdate and ammonium tungstate were selected as dopants and their effect was also studied. The as-obtained products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). Mo-W co-doped VO_2-waterborne polyurethanes (WPU) was then fabricated with isophorone diisocyanate (1PDI), 2.2-bis(hydroxymethyl) propionic acid (DMPA) and nanosized Mo-W co-doped VO_2-poly(e-caprolactone) (PCL) as the starting materials. Organic-inorganic hybrid coatings are always achieved with adjustable contents of Mo-W co-doped VO_2. The hybrid coatings with Mo-W co-doped VO_2 loading on the glass substrate were characterized by variable-temperature UV-vis-IR transmittance spectroscopy and exhibited good optical properties and metal-insulator transition (MIT) properties in the infrared area. The results showed that the doping ions had little influence on the morphology of co-doped VO_2(R), but they effectively reduced the phase transformation temperature (T_c). The Mo-W co-doped VO_2(R) nano-powders showed prominent thermochromic properties with a low phase transformation temperature and highly visible light transmittance.