Carbothermic reduction of anatase and rutile

Initial stages of oxidation of near-stoichiometric titanium carbide at low oxygen pressures

“…The presence of carbon within the scale during the oxidation of transition metal carbides very often leads to the formation and stabilisation of oxides that would normally be unstable in this range of temperatures [21]. A similar situation has been observed in the present study, as the anatase phase, contained in the oxide scale, was observed up to 800 • C. According to recent data by Zhang et al [22], the polymorphic transition of the anatase to rutile phases begins at 500 • C and reaches about 95% at 700 • C. Another key observation is that the anatase phase, in contact with carbon, is more chemically stable; this is confirmed by noting that the carbothermic reduction of anatase starts at higher temperatures when compared with those for the rutile phase [23]. From the obtained experimental data, a convincing argument would be that, during the oxidation of TiC 1−x , the anatase-rutile phase transition is directly connected with the 'ridge' temperature, as the intensive polymorphic transformation is concurrent with deeper carbon burn-off in the scale.…”

Effect of elemental iron on the carbothermic reduction of the anatase and rutile forms of titanium dioxide

“…A thorough analysis of the TGA and XRD data for the reduction in the absence of iron has been presented previously [11] and will only be summarised here as required.…”

“…The as-milled anatase sample did not show any evidence for srilankite-TiO 2 which showed broad peaks at 2θ = 36.7, 49.1 and 49.8 • in the as-milled trace in the absence of iron [11]. Srilankite has been shown to be an intermediate in the milling-induced phase transformation of anatase to rutile [34][35][36][37][38][39][40].…”

“…It should also be noted that where anatase has been used, it has invariably undergone a thermal transformation to rutile prior to the onset of reduction. Thus, there had not previously been a study of the reduction of anatase to TiC, until recently [11].…”

“…A previous paper [11] has compared the mechanism of carbothermic reduction of rutile and anatase, this paper investigates the effect of iron on the same reduction reactions.…”