Microemulsion-assisted hydrothermal preparation and infrared radiation property of TiO2 nanomaterials with tunable morphologies and crystal form

TiO2 nanomaterials with adjustable crystalline phases and morphologies were prepared via a mild condition of microemulsion-assisted hydrothermal method. The effects of various reaction conditions, such as the species of inhibitor acid, the concentrations of acid and the reaction temperatures on the crystal forms and morphologies of the TiO2 nanoparticles were investigated. The particles were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and Fourier transformed infrared spectrometer. Experimental results showed that the inhibitor acid of hydrochloric acid in the high concentration was conducive to the formation of rutile TiO2. Nitric acid led to the formation of anatase TiO2. The crystallinity of the TiO2 was improved and the particle size was increased with the increase of the reaction temperature and the acid concentration. The morphologies of the TiO2 nanoparticles also depended on the species and the concentration of the acids. TiO2 nanoparticles with various structures of irregular granular, spherical, cosh and donuts-like were presented. Moreover, the infrared emissivity values of the TiO2 nanoparticles were measured at wavelength of 8–14 μm. The irregular TiO2 granular with single crystal phase exhibited the optimal infrared radiation property owing to the enhanced scattering ability and attenuation effect.