Controllable preparation of Na2Ti6O13 whiskers and their high reflectivity in UV-VIS-NIR

Na2Ti6O13 whiskers were prepared by a molten salt method using Na2CO3, TiO(OH)2 as raw materials and NaCl as the salt. The effects of the calcining temperatures, weight ratios of salt/reactant, and the molar ratios of Na2CO3/TiO(OH)2 on the morphology and phase composition of the products were investigated. The results showed that single-phase Na2Ti6O13 whiskers can be synthesized from a mixture of Na2CO3, TiO(OH)2 and NaCl when calcined at 900 °C for 3 h. We also proposed a synthetic mechanism. Moreover, the thermal conductivity of the Na2Ti6O13 was 0.729 W/(m.k) and the reflectivity among 500–1500 nm of the synthesized Na2Ti6O13 whiskers reached 90%, and have relatively high reflectivity from 350 nm to 400 nm, which indicated that Na2Ti6O13 was a highly reflective energy-saving material. CThe UV-VIS-NIR reflectance spectra of the products calcined at different temperatures are shown in (a). The reflectivity from to 500 nm–2500 nm reaches to 90%. It is interesting to note that there is a great difference of the reflectance spectra between 300 nm and 500 nm, as shown in (b). The reflectivity of the products calcined at 700 °C is very different from 750 °C, 800 °C, 900 °C, and 1000 °C. When the calcining temperature is increased to 750 °C, the starting wavelength of the high-reflectivity step shifts to the low-wavelength direction. The energy band gaps of products calcined at 700 °C, 750 °C, 800 °C, 900 °C, and 1000 °C are 3.58 eV, 3.65 eV, 3.68 eV, 3.67 eV, and 3.69 eV, respectively, as shown in (c)−(f). [Display omitted] •Na2Ti6O13 whiskers can be synthesized by a facile molten salt method.•The synthesized Na2Ti6O13 whiskers show high reflectivity in VIS-NIR wavelength.•The Na2Ti6O13 whiskers have relatively high reflectivity from 350 nm to 400 nm.