| Popis: |
The effect of composition and porosity on the strength and toughness of a binary oxide, HfTiO4, was investigated. This material has several interesting characteristics: (a) a near-zero thermal expansivity (in polycrystalline form) arising from a negative expansivity along one of the crystallographic axes, and (b) a large solid solubility range, based on the composition HfTiO4, and extending from around 35 mole % TiO2 to beyond 50 mole % TiO2. Strength was measured in 4-point bending while fracture energy was measured on side-grooved double-cantilever-beam (DCB) specimens. Increasing porosity in the range from 12 to 26% had little effect on strength and caused a slight decrease in fracture energy. Compositions in the range from 30 to 40 mole % Ti2 exhibited lower strengths and greater fracture energies than did compositions containing 45 to 50 mole % TiO2. A simple microcrack model was developed to rationalize both the fracture strengths observed and the effect of composition. |
