Low-Temperature Synthesis of Nanodispersed Titanium, Zirconium, and Hafnium Carbides

摘要

Nanosized refractory titanium, zirconium, and hafnium carbides were manufactured from highly dispersed metal dioxide–carbon starting mixtures at moderate temperatures of 1200℃ or lower. The prod-ucts were characterized by powder X-ray diffraction, elemental analysis, and transmission electron micros-copy. The average size of particles (in nanometers) manufactured at 1200℃ was as follows: for TiC, 13 ± 4; for ZrC, 17 ± 3; and for HfC, 16 ± 3; the average crystallite size (in nanometers) was as follows: for TiC, 8 ± 2; for ZrC, 5 ± 2; and for HfC, 8 ± 3. Thermodynamic modeling was performed for the synthesis of Group IVB carbides via carbothermal reduction of the corresponding oxides. The results show that in the titanium dioxide–carbon system, for example, titanium monocarbide formation is possible at a temperature as low as 850℃ (p = 10~(-4) MPa). Highly dispersed metal dioxide–carbon starting mixtures were prepared using sol–gel technology from metal alkoxyacetylacetonates in the presence of a polymeric carbon source.