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

摘要：

为了提高烧失法制备的多孔莫来石材料的气孔率和隔热性能,以SiO₂微粉和α-Al₂O₃微粉为主要原料,分别以固含量为3%(w)的SiO₂溶胶、固含量为5%(w)的ZrO₂溶胶、固含量为7%(w)的Al₂O₃溶胶浸渍的核桃壳粉为造孔剂,以PVA为结合剂,经球磨混合、压制成型、自然干燥、1 500 ℃保温3 h热处理制成多孔莫来石材料,检测了材料的显气孔率、体积密度、常温耐压强度、热导率,并分析了材料的物相组成和显微结构。结果表明:1)与以未浸渍核桃壳粉为造孔剂制备的多孔莫来石材料相比,以SiO₂溶胶、ZrO₂溶胶或Al₂O₃溶胶浸渍的核桃壳粉为造孔剂制备的多孔莫来石材料的烧后线收缩率显著减小,显气孔率显著增大,热导率显著减小;常温耐压强度虽然显著减小,但均超过30 MPa。2)比较发现,以SiO₂溶胶浸渍核桃壳粉为造孔剂制备的多孔莫来石材料的综合性能较佳,其显气孔率约为39%,常温耐压强度为55 MPa。

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