Preparation And Modification Of Aluminum Titanate Materials

Aluminum titanate(AT) is the only known structural material of low inflation and high temperature resistance till now.Its strength is very low and it will decompose into Al₂O₃ and TiO₂ during 850℃-1280℃.These two weaknesses severely restricted its use.In this paper, with inorganic salts as raw materials,AT was synthesized in a solid-state routine and with alkoxides,AT was prepared at a lower temperature comparatively.AT composited with the MgO,CeO₂ A₃S₂ powders,A₃S₂ fiber,SiC and other materials was further systematic studied.Sintering,mechanical properties,thermal stability,thermal expansion and thermal shock resistance of the prepared product was investigated.And also study the the relationship between firing process and material properties.Based on the status of AT ceramics research,In this paper withα-Al₂O₃ and chemical pure TiO₂ according to the stoichio-metric ratio of AT compound,a relatively pure AT was first synthesized in 1450℃for 2 hours in the laboratory.AT composites material properties was studied by the introduction of stabilizer agent MgO or CeO₂ The introduction of MgO can reduce the micro-cracks and strengthen the AT densification,effectively increase the thermal expansion coefficient,and also inhibit the abnormal grain growing up in AT. Bending strength of the AT with 3%MgO compared to the pure AT,increased from 13.07MPa directly to 32.60MPa,about 2.5 times more.But then as the content of MgO increaseed,bending strength increases slowly.The effect of CeO₂ on the stability and bending strength of AT is little and effect were not evident as the amount of CeO₂ increased. In the preparation of AT composite ceramic modified by MgO and CeO₂,the introduction of CeO₂ additives can reduce the eutectic temperature,formate liquid phase at a lower temperature,promote sintering of the materials and then improve the density of the samples. AT modified with 3%MgO +4%of CeO₂ is a appropriate formula in improving the mechanical strength of materials and maintenance of a low thermal expansion coefficient and good thermal stability.In this paper we also tried to synthesize AT by non-hydrolytic sol-gel method at 750℃with(C₄H₉O) ₄Ti,AlCl₃,and C₂H₅OH as raw materials in the laboratory.The synthesized temperature of AT reduced 500-600℃compared to the general solid-phase synthesis of AT,laying certain foundation for industrialization of AT.It will be nano-scale particles of AT heated at 750℃for 2 hours,the size of AT particles gradually changed from the nano-scale to the micron level as the temperature rising.The particle morphology is also becoming more and more complete,forming the surface of needle-like spherical.In the composite AT system with Mullite(A₃S₂),the samples with the content 20%of A₃S₂ not only have minimal coefficient of thermal expansion,but also a higher retention rate of thermal shock strength.The density of the specimen gradually increased with the added amount of powder A₃S₂.The grain of samples is gradually refined with A₃S₂ accession in the same trend.The growth of AT grain was inhibited in the firing process as A₃S₂ added.Together with high strength of A₃S₂,the mechanical performance of the composite was improved.In the SiC + Al₂O₃ + AT system,with the content of SiC increased in the system,the oxidation of the sample surface become more and more serious and the specimen surface gradually become dense,leading to the gradual increase of mechanical strength of the specimen.The cross-section of A₃S₂ fibers and AT composites fired in 1400℃for 2 hours,still remains intact,not very close to the AT base materials.Heated at 1500℃for 2 hours,fiber and matrix materials melted and disappeared,with a certain improvement in strength.The shrinkage of composite specimens with A₃S₂ fiber and AT gradually increased as A₃S₂ added,bending strength also increased gradually...