Norbert Moskała, Waldemar Pyda Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, al. Mickiewicza 30, 30-059 Kraków

Quarterly No. 1, 2005 pages 56-62

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abstract Composite powder in the TiO2-Y2O3-ZrO2/TiB2 system was prepared by using an in situ rout in which the reaction among titanium oxide dissolved in the Y2O3-ZrO2 solid solution, boron oxide and carbon was utilized. A mixture of the zirconia nanopowder containing 1.5 mol % Y2O3, 18 mol % TiO2 and 80.5 mol % ZrO2 in solid solution, boric acid and carbon was used for the synthesis. Carbon was incorporated into the mixture as the 20 wt.% alcohol solution of fenol-formaldehyde resin. The uniform mixture was first dried in the argon flow to decompose H3BO3 and the resin. Then it was heat treated for 4 h at 1500°C in vacuum to synthesize composite powder containing TiB2 grains. Finally, the heat-treated powder was milled by wet attrition in isopropyl alcohol. Usefulness of the composite powder for production of the zirconia-based composites by means of hot pressing was checked. Phase composition and morphology of the composite powder was characterized by means of X-ray diffractometry and transmission electron microscopy (TEM), respectively. Energy-dispersive X-ray spectroscopy (EDS) was used to analyze chemical composition of the powder particles. Specific surface area of the powder was measured by the BET method. The differential thermal analysis (DTA) combined with thermogravimetry (TG) was also carried out for the powder. X-ray diffractometry, three point bending and Vickers’ indentation was used to determine phase composition, bending strength and fracture toughness of the dense composite, respectively. Its microstructure was also observed by using scanning electron microscopy. The composite zirconia powder contained in situ synthesised TiB2 inclusions (Fig. 1). Small amounts of TiC, ZrC and ZrB were also detected. The composite derived from the powder contained TiB2 as the main inclusion and small amount of TiC (Fig. 5). A bending strength of 912 ±72 MPa and a fracture toughness of 8.8 ±0.5 MPa • m1/2 were measured for the composite hot pressed at 1500°C. Key words: composite powder, composites, TZP, TiB2, TiC, in situ synthesis, TZP-TiX