Processing of biomorphic porous TiO2 ceramics by chemical vapor infiltration and reaction (CVI-R) technique

Porous biomorphic TiO2 ceramics were manufactured from paper preforms by chemical vapor infiltration and reaction (CVI-R) in a three-steps process. First, the cellulose fibers of the paper were converted into carbon (Cb) by pyrolysis in an inert atmosphere. Then, Cb-template was infiltrated with a precursor system consisting of TiCl4, CH4 and H2 to produce porous TiC ceramics, which were oxidized in a final step with air at temperatures in the range of 400–1200 °C. Depending on the conversion degree, TiC/TiO2 or TiO2 ceramics were obtained. The kinetics of the oxidation process was studied by thermal gravimetric analysis (TGA) and activation energies of 63 and 174 kJ mol−1 were estimated for the lower (400–800 °C) and higher (950–1200 °C) temperature regions, respectively. The TiO2 ceramics were characterized by Raman spectroscopy (anatase/rutile ratio), SEM/EDX (morphology, composition) and nitrogen gas adsorption (pore structure). It was shown, that the anatase/rutile ratio as well as the pore structure of the resulting TiO2 ceramics could be controlled varying the oxidation temperature. The TiO2 samples obtained by oxidation of TiC biomorphic porous ceramics are lightweight but nevertheless have very good mechanical performances. Their bending strength varies between 30 and 40 MPa at a porosity of 65–70%. These structures have many potential applications, e.g. light structured materials, implants because of their bio-compatibility, catalyst support or catalyst for photo catalytic applications.