Reactive spontaneous infiltration of Al-activated TiO_2 by molten aluminum

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.

Spontaneous infiltration and wetting behaviors of a Zr-based alloy melt on a porous SiC substrate

The spontaaleous infiltration aald wetting behaviors of a Zr-based alloy melt on porous a SiC ceramic plate were studied using tile sessile drop metilod by continuous heating and holding for 1800 s at different temperatures in a high-vacuum furnace. The results showed that tile Zr-based alloy melt could pastly infiltrate tile porous SiC substrate without pressure due to tile effect of capillary pressure. Wettability and infiltration rates increased witil increasing temperature, and interracial reaction products （ZrC0.7 and TiC） were detected in tile Zr-based alloy/SiC ceramic system, likely because of tile reaction of tile active elements Zr and Ti witil elemental C. Furtilelinore, tile redundant ele- ment Si diffused into tile alloy melt.

Synthesis of SiC/Al Co-Continuous Composite by Spontaneous Melt Infiltration

Investigation has been made on the process of synthesizing SiC/Al co-continuous composite by spontaneous melt infiltration. It is found that nitrogen atmosphere is an indispensable factor for spontaneous infiltration of melt Al into SiC preform with continuous porosity. The critical temperature for spontaneous infiltration occurrence can be lowered and spontaneous infiltration rate increased by doping a small amount of Mg into the Al alloy. Adding fine SiO2 powders into the ceramic preform can play the similar role as Mg-doping by increasing wetting through the chemical reaction of 3SiO2+4AI=2Al2O3+3Si at the infiltration front. Infiltration rate can also be increased by Si-doping to lower the viscosity of the molten Al alloy. In addition, sufficient Si content in the molten Al is also indispensable to avoid the formation of Al4C in the synthesized composite.