Chemical vapor deposition of carbon on particulate TiO_2 from CH_4 and subsequent carbothermal reduction for the synthesis of nanocrystalline TiC powders

摘要

The present study aims to investigate chemical vapor deposition of carbon from CH4 on TiO_2 particles and to establish optimal conditions for the synthesis of nanocrystalline TiC powders. Mass measurements, XRD, HR-TEM and SEM were used to characterize the products at various stages of the reactions. Oxide particles gained mass rapidly at 1300 K under CH_4 atmosphere and were coated with thin pyrolytic carbon layers of 10-20 nm. XRD analysis showed that the coated powders consisted of C, TiO_2 and titanium sub-oxides. The powders containing ~33 ± 2 wt% carbon were used for the carbothermal reduction of TiO_2 to TiC at 1600-1800 K under Ar flow. Lattice constant and mass loss of the samples increased to the levels of TiC with temperature and time. Nearly pure TiC powders with a mean particle size of ~125 nm were synthesized at 1750-1800 K within 30 min.