关键词: 莫来石, 多孔材料, 烧失法, 造孔剂, 核桃壳粉, 溶胶, 浸渍

Abstract:

In order to improve the porosity and the thermal insulation performance of porous mullite materials prepared by ignition loss method,the porous mullite materials were prepared using SiO₂ micropowder and α-Al₂O₃ micropowder as the main raw materials,walnut shell powder impregnated by SiO₂ sol with solid content of 3 mass%,ZrO₂ sol with solid content of 5 mass%,and Al₂O₃ sol with solid content of 7 mass%,respectively,as the pore-forming agent,and PVA as the binder,ball milling,pressing,natural drying and 3 h heat treatment at 1 500 ℃.The apparent porosity,the bulk density,the cold compressive strength,and the thermal conductivity of the materials were determined,and the phase composition and the microstructure of the materials were analyzed.The results show that:(1)compared with the porous mullite prepared with unimpregnated walnut shell powder,the developed materials have significantly decreased linear shrinkage,and thermal conductivity,but obviously increased apparent porosity.The cold crushing strengthes decreased significantly,but all exceed 30 MPa;(2)it is found that the porous mullite material prepared by impregnating walnut shell powder with SiO₂ sol as pore forming agent has good comprehensive properties,with 39% of apparent porosity and 55 MPa of cold crushing strength.

Key words: mullite, porous materials, ignition loss method, pore-forming agent, walnut shell powder, sol, impregnation