Direct Synthesis of Controllable Microstructures of Thermally Stable and Ordered Mesoporous Crystalline Titanium Oxides and Carbide/Carbon Composites

The mesoporous titanium oxides- and carbide-carbon nanocomposites (Ti-C nanocomposites) with different morphologies at various Ti/C mass ratios were directly synthesized via supramolecular self-assembly with in situ crystallization process. The microstructures including surface area, morphology, and crystallinity were characterized by surface area analyzer, TEM, and SAXS/XRD respectively. The specific BET surface areas (178-639 m(2) g(-1)), micropore surface areas (6 3-47.3%), and total pore volumes (0 18-0 46 cm(3) g(-1)) increase with the increase in calcination temperatures and Ti/C mass ratios. The calcination temperature and carbon content have significant effect on the thermal stability of titanium-based nanomaterials. The crystallinity changes from anatase, rutile, Magneli phases, and then to TiC when the carbon content is lower than 35 wt%, while the crystal phase of Ti-C composites at 50 wt % changes directly from anatase to TiC. However, Mageli products lose the mesostructures. The sizes of TiO2 nanocrystals are in the range 2 6-9 7 nm, and increase with increasing temperature to slightly distort the ordered mesostructured regularity up to 800 degrees C, and low distorted octahedrons with 6-fold coordinated titanium carbide are formed at 1000 degrees C. In addition, the graphitized carbons, determined by sp(2)- and sp(3)-bonded carbon contents from XAS spectra, increased upon increasing calcination temperature, depicting the increase in graphitization after calcination Results obtained in this study allow us to elucidate the microstructural changes of titanium-based materials inside the highly ordered mesoporous carbon matrices and open an avenue to the design and synthesis of a multitude of coperatively functional organic-inorganic materials with attractive novel properties.