Studies on the Carbothermal Preparation of Titanium Carbide from Different Gel Precursors

Abstract

Different mixed organic–inorganic gels as precursors for the synthesis of titanium carbide and oxycarbides have been prepared in aqueous and organic solutions starting either from rutile or titanium alkoxide. The sol–gel processes have been controlled by complexing additives such as H 2O 2, acetic acid or ethyl aceto-acetate. Upon pyrolysis up to ∼600°C, composites of finely divided particles of amorphous titania and carbon are formed. Monitoring of the high-temperature treatment by TG, XRD and nitrogen adsorption up to 1600°C revealed a three-step carbothermal reduction mechanism through lower titanium oxides and oxycarbides. The intimate mixture of titania and carbon leads to a considerable lowering of the onset of the reaction temperature in comparison with rutile/carbon black and rutile/gel mixtures. Delayed reactions in the final steps, however, may be due to the interruption of the intimate contact of the reactants by pore generation. During the high temperature processes microporous and mesoporous intermediate materials have been prepared; the final products at 1600°C are finely divided particles of oxycarbides with oxygen contents of 1·2–3·4 wt% and grain sizes lower than 1 μ m.