Nano-to-macroporous TiO2 (anatase) by cold sintering process

Cold Sintering Process (CSP) was applied on commercial nanopowders to produce nanostructured TiO2 anatase with nano-to-macro porosity. Nanoporous TiO2 based materials were obtained by applying CSP at 150 degrees C and pressures up to 500 MPa on three TiO2 nanopowders with different specific surface area (s.s.a. = 50, 90 and 370 m(2)/g), using water as transient aqueous environment Although TiO2 is insoluble in water, a density of 68% and s.s.a. = 117 m(2)/g were achieved from the powder with the highest specific surface area. A post annealing process at 500 degrees C increased the density up to 73% with a s.s.a. = 59 m(2)/g, and the crystallites dimensions passed from 110 angstrom in the powder to 130 angstrom in CSP material and 172 angstrom after post annealing. Finally, macroporosity was produced by using thermoplastic polymer beads as sacrificial templates within TiO2 nanopowder during CSP, followed by a debonding at 500 degrees C.