Microstructure and Properties of Partial Stoichiometry Cordierite Ceramic Materials

Due to their characteristics of low thermal expansion coefficient, strong thermal shock resistance and high temperature resistance, cordierite ceramics have been widely used in environments with rapid changes between high and low temperatures. How to further reduce the thermal expansion coefficient of cordierite ceramics to improve their mechanical strength is still a research hotspot. With Suzhou kaolin, talc and γ-Al₂O₃ with single-layer sheet structure as raw materials, cordierite ceramic samples with different compositions were designed, in order to achieve low thermal expansion. The samples were characterized by using XRD, SEM, CTE and EPMA and so on. The effects of partial stoichiometry on microstructure and properties of the cordierite ceramics were studied. It is found that single phase cordierite ceramics could be derived from metamagnesium (Si/Al is 1.34), with thermal expansion coefficient of 1.91×10⁻⁶ ℃⁻¹ (25–800 ℃), flexural strength of 50 MPa, porosity of 20%, bulk density of 1.90 g·cm⁻³, while the loss rate of flexural strength is only 2.66% after 30 cycles of air-cooling and heat-shock cycle test (25–1000 ℃). MgO in the metamagnesium promoted the formation of liquid phase at high temperatures, which boosted the chemical reaction, leading to the content of cordierite to be 99 wt.%. In addition, because the cordierite grains are oriented, the thermal expansion coefficient of the samples are reduced. As a result, thermal shock resistance of the sample is improved.