Microstructure and properties of zirconia-based nanocomposites derived from a powder containing TiC crystallised in situ and carbon

The reaction between carbon and titanium originated from zirconia–titania solid solution was used to produce TiC inclusions in situ in zirconia powders and dense materials. The co-precipitated powder composed of 1.5 mol% Y2O3, 18 mol% TiO2 and 80.5 mol% ZrO2 was mixed with phenol-formaldehyde resin in an amount giving 200% excess of carbon in terms of the stoichiometry of the carbothermal reduction of TiO2. The mixture was heated for 2 h at 1500 °C in argon. The resultant composite powder was composed mainly of tetragonal and monoclinic phases and contained 9 wt.% TiC and non-reacted carbon. The mixture of the composite powder and the original co-precipitated one (25/75 wt.%) was used to prepare composite materials by means of pressureless sintering in argon. The sintered bodies were composed mainly of tetragonal and monoclinic phase and contained nanocrystalline TiC inclusions which showed two different morphologies: oval and elongated. The role of oxygen vacancies in the in situ formation of the elongated TiC inclusions is discussed. Improvement in the characteristics of the zirconia materials was obtained.