Synthesis And Application Of Cordierite Ceramic With Low TEC

Cordierite material has low thermal expansion coefficient（TEC）and good thermal stability.It is widely used in many fields such as refractory,ceramic support of catalyst,regenerative body and honeycomb ceramics.Cordierite based honeycomb ceramics are used as the key element of environmental protection equipment that used for treating high temperature dust containing gas,and the most important performance parameter is the TEC.However,the TEC of cordierite honeycomb ceramic produced in domestic is usually relative high,limiting its service life and scope of application.To reduce the TEC and improve the comprehensive performance of the cordierite ceramics product are extremely urgent.In the present work,we explored the influence laws of minor changes of MgO,Al₂O₃ and SiO₂ content on TEC of the synthesized cordierite ceramics,studied the effects of kaolin kinds and materials calcination on the properties of the synthesized cordierite,and discussed the effect of TiCl₄ and Al₂TiO₅ as additives on the TEC of synthesized cordierite.In the end,large-size honeycomb ceramics based cordierite-Al₂TiO₅ were prepared by extrusion molding.The main conclusions are obtained as following.The chemical composition has a great influence on the TEC of the cordierite ceramic,and minor changes of SiO₂,Al₂O₃ and MgO will lead to a significant change in the TEC of the synthesized materials.The firing temperature range for cordierite ceramics is narrow,the suitable sintering temperature ranges from 1420℃to 1450℃,and the holding time is appropriate for 2-3 h.When the sintering temperature is 1445℃and the soaking time is 2h,a cordierite based ceramic with TEC of 1.42×10^-6℃^-1 can be obtained.Addition of TiCl₄ can lower the TEC of the synthesized materials by promoting the crystal phase transition fromβ-cordierite toα-cordierite.When the content of TiCl₄ is 4 wt.%,a cordierite based ceramic with TEC of 1.16×10^-6℃^-1 can be obtained.When the content of TiCl₄ is more than 6.0 wt.%,spinel and sapphire crystal can be found in the ceramics.Addition of Al₂TiO₅ can effectively reduce the TEC of cordierite ceramic.Increasing the molding pressure is helpful to decrease the TEC of cordierite-Al₂TiO₅compound material,but improve the sintering temperature and extending the soaking time is disadvantageous to decrease the TCE.When the content of Al₂TiO₅ is 40wt%,molding pressure is 10MPa,sintering temperature is 1320℃and soaking time is 1.0h,a cordierite-Al₂TiO₅ composite material with TEC of 1.04×10^-6℃^-1 can be obtained.Using the synthesized cordierite-Al₂TiO₅ composite as raw material,adding a proper amount of additives to make it plastic,the honeycomb ceramic green body with no obvious defect was obtained by extrusion method.When sintering temperature was 1320℃and the soaking time was 1h,the high performance honeycomb ceramics based on cordierite-Al₂TiO₅ composite were prepared,the TEC of ceramics is 1.01×10^-6℃^-1 and the apparent porosity is 41.3%.