Preparation of transparent, hard thermochromic polysiloxane/tungsten-doped vanadium dioxide nanocomposite coatings at ambient temperature

摘要

Polysiloxane/tungsten-doped vanadium dioxide [VO_2(W)] nanocomposite coatings were prepared by de-agglomerating and modifying the self-made VO_2(W) particles with 3-methacryIoxypropyItrimethoxysilane in butyl acetate, then mixing MPS-functionalized VO_2(W) nanoparticles with polysiloxane oligomers and curing the product at ambient temperature with the aid of 3-aminopropyltriethoxysilane. The VO_2(W) particles were obtained by hydrolysis of vanadyl sulfate mingled with tungstate dopant and subsequent calcination. The structure and properties of the VO_2( W) particles and nanocomposite coatings were characterized by X-ray diffraction analysis, differential scanning calorimetry, visible-near infrared spectroscopy, pendulum hardness tests, and nanoindentation. The effects of the synthesis conditions and the de-agglomeration process on the properties of the VO_2( W) particles were investigated. Crystalline VO_2(W) particles were obtained only with an appropriate amount of air and temperature during the calcination step and were easily reduced to nanometer size by bead-milling. The obtained nanocomposite coatings exhibited high transparency, good thermochromic performance, and ultra-high hardness (-1.0 GPa).