The application of nanocrystalline oxides as precursors for synthesis of new nanomaterials with the preservation of the dimensions of the initial nanoparticles is of considerable interest. Its main problem is the sintering and growth of the nanoparticles during the solid-state chemical transformations at elevated temperatures. A promising approach to the solution of this problem is the deposition of a coating on the surface of the precursor nanoparticles that would prevent their sintering. Current study was devoted to the investigation of the solid-state phase and chemical transformations of nanocrystalline TiO2 and Al2O3 coated with carbon. In all cases the carbon coating acting as a carbon nanoreactor prevented the sintering of the nanoparticles. Meanwhile, such coating appeared to be penetrable by the molecules present in the gas phase. The anatase phase in all synthesized C@TiO2 nanocomposites could be completely converted to TiOF2 in the reaction with halocarbons. Intriguingly, this reaction was phase-selective: only anatase nanoparticles were converted. So, the carbon coating deposited on the oxide nanoparticles prevents their sintering and makes it possible to synthesize new nanomaterials. Small size of the oxide nanoparticles inside such carbon nanoreactor is the key factor preventing the phase transformations in the studied C@TiO2 and C@Al2O3 nanocomposites.
Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites
Published: June 21, 2010
Pages: 701 - 704
Industry sector: Advanced Materials & Manufacturing
Topicss: Advanced Materials for Engineering Applications, Composite Materials