Study On The Preparation And Characteristics Of Low Thermal Expansion Cordierite Ceramics

Study pressing and calcining technology on the preparation and the characteristics of cordierite ceramics with different raw materials, pure oxide, the mixture of pure oxide and prepared cordierite powder, the raw material with the addition of the mixture of TiO₂ and Al₂O₃ and prepared cordierite powder. Experiment on cordierite ceramics, which was prepared with three kind of different raw material mentioned before through structure analyzing with XRD and SEM, testing TEC (Thermal expansion coefficient). If with the first kind of raw material at 1340, the experimental result showed that it can prepare cordierite ceramics, but the major composition of which is low temperature B-cordierite, the TEC of which is 2.22×10^-6℃^-1. If with the second raw material, it can prepare mixed cordierite(α-cordierite +β-cordierite) at 1300, and its TEC is 1.8×10^-6℃^-1, but its Burning shrinkage is high relatively. If with the third kind of raw material, it not only can prepare mixed cordierite(α-cordierite +β-cordierite ) at lower temperature, but can reduce TEC, TEC reduce to as low as 1.6×10^-6℃^-1. And at the meanwhile burning shrinkage is low. It is because the mixture of TiO₂ and Al can prepare Al₂TiO₄, TEC of which is far small and which have apparent thermal expansion anisotropy, and prepared cordierite powder can promote a reaction, which can prepare cordierite, specially, the promotion affection of a-cordierite is more positively that the specimens which is prepared of the third raw material show excellent characteristic. MgO in the raw material can promote the reaction, which prepare Al₂TiO₄, and can prevent Al₂TiO₄ from decomposing because MgO and Al₂TiO₄ create MgTiO₅. Thus, the ration of the volume of Mg and Al in the material, is an important factor, which affect TEC of cordierite ceramics.