The results showed that under optimal experimental conditions i.e. tetrabutoxytitanium/calcium carbonate molar ratio (50 wt.%) and annealing temperature (773 K), the tube materials exhibited uniform tubular structure with a length of 8–15 μm and an inner diameter of ∼400 nm, a wall thickness of ∼40 nm, a surface area of 112.2 m2/g and a pore volume of
0.18 cm3/g.