Preparation,Properties And Characterization Of Aluminum Titanate Flexible Ceramics

Aluminum titanate has been widely used in chemical industry,metallurgical,ceramics and environmental protection fields due to its low thermal expansion coefficient,high melting point,good thermal shock resistance,low thermal conductivity.However,aluminum titanate ceramics tend to generate a large number of microcracks during the cooling process because of the anisotropy of thermal expansion coefficient,which makes this material exhibit lower mechanical strength.Thus,that can limit their further application.Likewise,the"characteristic"of aluminum titanate can also make it possible to prepare flexible ceramics with a kind of special microstructure that is similar to itacolumites.Firstly,the aluminum titanate flexible ceramics were prepared by solid phase sintering method with using aluminum titanate powders as raw material,and the effects of sintering temperature and holding time were studied in detail.The results showed that the holding time,especially the sintering temperature,had a great influence on the microstructure and mechanical properties of the samples.The states of microcracks mainly affected the bending flexibility of the sample.When the sintering temperature increased from low to high,the grains inside the sample increased and the grain boundary microcracks gradually widened.The widened microcracks can allow the grains to undergo more displacement when subjected to applied load,which led to more obvious bending flexibility of samples.At the same time,the presence of microcracks also affected the mechanical strength of the sample.And then the sintering properties,microstructure and bending properties of three different flexible samples（NF（Non Flexible）,F（Flexible）,VF（Very Flexible））were systematacially analyzed.The results showed that the VF sample sintered at 1550℃ for 12 h had the best bending flexibility with deformation of 0.53 mm and flexural strength of 13.38 MPa.The distance between the two support points is 30 mm at three-point bending test.Secondly,the aluminum titanate flexible ceramics also prepared by additives method with using analytically pure Al₂O₃,TiO₂ and some additives（MgO,Fe₂O₃ and SiO₂）.The effects of single additive and multiple additives on the microstructure and properties of aluminum titanate flexible ceramics were investigated in detail.The optimum additive dosage and composition formula determined by exploratory experiments were as follows:Al₂O₃ 56wt%,TiO₂ 44wt%,MgO 4wt%,Fe₂O₃ 4wt%,that was ATFM sample doped with binary additive MgO-Fe₂O₃.The effects of sintering temperature and holding time on ATFM samples were systematically investigated,and the function mechanism of the binary additive MgO-Fe₂O₃ was also analyzed.The results showed that co-doped MgO-Fe₂O₃ can effectively reduce the formation temperature of aluminum titanate,and promote the formation of elongated grains and grain boundary microcracks,which can make samples exhibit a better bending flexibility and enhance the flexural strength.As the temperature rised,the bending flexibility of the ATFM sample increased gradually,but the strength continued to decrease.The holding time had a promoting effect on the bending flexibility of samples sintered at 1400℃,but the effects was not well at the subsequent sintering temperature.The ATFM sample sintered at 1500℃ for 2 h showed a better performance.The deformation was 0.55 mm,and the flexural strength was 19.57 MPa.The distance between the two support points is 30 mm at three-point bending test.Finally,two kinds of flexible ceramic samples（VF and ATFM）with excellent performance prepared by using different raw materials were selected for comparative analysis in this paper.The results showed that the ATFM sample prepared by additive method had a lower sintering temperature（1500℃）,a shorter holding time（2 h）,a higher flexural strength（19.57 MPa）,a larger deformation（0.55 mm,the distance between the two support points is 30 mm at three-point bending test）and better bending cycle performance.Therefore,the flexible ceramics prepared by the additive method had higher flexural strength while ensuring a higher deformation value.In this study,aluminum titanate flexible ceramics were innovatively prepared by additive method with using solid-phase sintering,which enhanced the performance of flexible ceramics and improved the process conditions for preparation.It also provided a new practical way for the preparation of flexible ceramics and had a great significance on broadening the application of ceramic materials.