Investigations of near infrared reflective behaviour of TiO2 nanopowders synthesized by arc discharge

• TiO2 spherical nanopowders were successfully synthesized by arc discharge method.
• Anatase to rutile phase transformation occurred before arc current reached to 50 A.
• TiO2 crystallite size was significant effected by the arc discharge current.
• Up to 50% of near infrared reflection of TiO2 nanopowders was shown in this paper.

Titanium dioxide (TiO2) nanopowders with different polymorphic phases were successfully synthesized by an arc discharge method. Samples were characterized using synchrotron radiation X-ray diffraction, high resolution scanning electron microscopy, high resolution transmission electron microscope and near infrared diffuse reflectance spectroscopy. Spherical structures were obtained after arc discharge. A mixture of both anatase and rutile phases was discovered in TiO2 samples synthesized at an arc current of 50 A, showing a majority particle size of 34 nm with size distribution between 5 nm and 60 nm. Completed anatase to rutile phase transformation was observed when the arc current increased from 50 A to 74 A. The crystallite size of the TiO2 nanopowders was significant effected by the arc discharge current during synthesis. After the arc current increased from 74 A to 110 A, the majority particle size of the obtained TiO2 increased to 85 nm with a size distribution in the range between 50 nm and 1800 nm. Diffuse reflectance of the TiO2 nanopowders synthesized at different arc discharge currents was measured. Broadband near infrared reflection (800–950 nm) of up to 50% was observed for TiO2 nanopowders synthesized at an arc current of 74 A. It is considered that rutile phase together with an appropriate mean crystallite size of the TiO2 nanopowders synthesized at an arc current of 74 A contributes to the best near infrared reflectivity in this study. The developed TiO2 nanoppowders will be of immense use in NIR reflective pigment.