Fabrication of TiO2 nanowhiskers by the heat treatment of bulk Ti3Si0.9Al0.1C2 in rough vacuum

Rutile TiO2 nanowhiskers with [0 0 1] growth direction were successfully fabricated by treating bulk Ti3Si0.9Al0.1C2 solid solution at 900 °C in 104 Pa air. In the initial stage, TiO2 nanowhiskers are preferentially formed on the side facets of Ti3Si0.9Al0.1C2 grains due to the rapid diffusion of Ti atoms along the basal planes. With the increase of treating time, a mixed oxide scale of TiO2, SiO2 and Al2O3 is gradually developed. Consequently, the growth of TiO2 nanowhiskers is controlled by the diffusion of Ti in the mixed oxide scale. In addition, it is found that the growth rate of TiO2 nanowhiskers strongly depends on the air pressure and the treating temperature. It diminishes dramatically with the decrease of temperature. However, only TiO2 nanosheets and large grains can be obtained above 1000 °C. In addition, air pressure around 104 Pa is appropriate for the growth of nanowhiskers.