Carbon nanoreactor for the synthesis of nanocrystalline high-temperature oxide materials

The use of nanocrystalline oxides as precursors for the synthesis of new nanomaterials in which the initial nanoparticle size is preserved is of considerable interest. Here, the major problem is the sintering and growth of the initial nanoparticles at high temperature. One method for solving this problem is the deposition of a coating on the surface of nanoparticles so that it would prevent the sintering of the nanoparticles without hindering their interactions with the molecules of the gas phase and the solid-state transformations inside the shell. This study demonstrates that a carbon coating deposited on the surface of nanocrystalline oxides can be permeable for gaseous reagents and is able to function as a rather firm shell for the nanoreactor, so that the nanoparticles of the oxides under the shell can undergo transformations into nanomaterials of different chemical origins or different phase compositions. The carbon coating prevents the nanoparticles of the solid-state reaction product from sintering and makes it possible to synthesize new nanomaterials, the particle sizes of which are similar to those of the initial nanooxide precursors. This approach was shown to be efficient for the synthesis of finely dispersed oxide materials based on TiO₂and Al₂O₃.