Reactive spontaneous infiltration of Al-activated TiO2 by molten aluminum
(1. Department of Applied Science and Technology, Politecnico di Torino, Corso Duca Degli Abruzzi 24, 10129 Torino, Italy;
2. Research Center of Graphene Applications, Beijing Institute of Aeronautical Materials, Beijing 100095, China)
2. Research Center of Graphene Applications, Beijing Institute of Aeronautical Materials, Beijing 100095, China)
Abstract: The reactive spontaneous infiltration of Al-activated TiO2 (anatase) was investigated. Pure Al powder was blended with TiO2 for activation. They were compacted into the preform and then sealed within 6060 alloy mould. The activation and infiltration were carried out in 6060 alloy bath for 1 h and comparative sintering experiments were carried out in an argon protected environment under the same conditions of temperature and duration. X-ray diffraction analysis proved that the Al sealed environment was superior to the argon protection on activating the reaction between Al and TiO2. The blending ratio of TiO2 to Al and the temperature were found to play the most important role in infiltration by affecting infiltration and reaction kinetics. Three main types of microstructures were observed after infiltration: full infiltration, partial infiltration with the formation of cracks and no infiltration. The formation of these microstructures was explained on the basis of reaction kinetics and local volume changes due to the reactions. Ultimately, it is found that to obtain an overall good spontaneous infiltration, a TiO2 to Al blending ratio around 3:7 in volume and an infiltration temperature around 900 °C are the most suitable.
Key words: spontaneous infiltration; pressureless sintering; TiO2-Al reaction; infiltration kinetics; in-situ fabrication