Preparation of aluminum titanate flexible ceramic by solid-phase sintering and its mechanical behavior

Abstract

Ceramics are known as a very brittle material. If this brittleness could be overcome, they can be applied in more fields. Itacolumite is regarded as a highly flexible rock for many narrow gaps at the grain boundaries in microstructure that allow a slight displacement of the particles when stressed. In this study, a ceramic mimicking the cracked microstructure of flexible sandstone (itacolumite) was successfully fabricated by sintering aluminum titanate (Al2TiO5: AT) powders. The phase compositions, apparent porosity, firing shrinkage and microstructure as well as mechanical behavior are examined. The influence of sintering temperature and holding time on the flexibility and microstructures of AT ceramics is studied. The results of fied-emission scanning electron microscopy and three-point bending test showed that the fired products benefited a microstructure with many grain boundary microcracks and showed a non-linear mechanical behavior due to its high thermal expansion anisotropy, which led to its flexibility like itacolumite. The flexibility of AT ceramics can be improved gradually with increasing sintering temperature and holding time. The optimal values for sintering temperature and holding time were determined as 1550 °C and 12 h. Three types of AT samples were chosen as reference: NF, F, and VF. NF sample had brittle behavior featuring a wide linear elastic zone, as typical ceramic materials. But F and VF sample had nonlinear ductile behavior that led to a higher flexibility due to grain boundary microcracks network and the interlocking of grains. The VF sample was more flexible than the F sample because of the greater average microcracks width.