Preparation And Properties Of Mullite Based Lightweight Thermal Insulation Materials By Foaming Method

Lightweight thermal insulation materials have been widely used in high-temperature industrial kilns,but with the increase of kiln temperature and the lightweight of kiln,the thermal insulation performance of thermal insulation materials becomes worse and the service life at high temperature is shortened.Therefore,it is imperative to develop new high temperature thermal insulation materials.Using Mullite powder,soft clay and silicon powder as raw materials,the effects of foaming mode,aluminate cement and Mullite fiber on the properties of Mullite lightweight thermal insulation materials are studied.The results show that the bulk density and compressive strength of the samples prepared by direct foaming process are better than those prepared by step foaming process.With rising of the amount of aluminate cement,bulk density of the sample decreased slightly.When the cement hydration products are removed during heating,the pore wall in the samples shrinks and the compressive strength of the sample decreases after firing.The specimens with 20wt%cement addition have relatively high mechanical properties and smaller linear shrinkage in the experimental range.The influence of mullite fiber on the performance of lightweight thermal insulation material was studied,the results show that the compressive strength of the material decreases gradually,the bulk density decreases gradually and the thermal conductivity decreases gradually with the increase of mullite fiber content.The decrease of thermal conductivity of thermal insulation material is due to the increase of the number of holes in the material,the continuity of the matrix is reduced,and the thermal conductivity path of the material becomes longer.When there are independent holes or micro-holes in the material structure,the number of holes that can be accommodated per unit area is more,and the matrix continuity of the material is worse.When there are small holes in the material structure,the number of holes that can be accommodated per unit area is less,and the heat transfer path is shorter.Compared with Mullite porous brick,the prepared Mullite foamed sample has a higher service temperature(1200?)and better insulation performance in all temperature segments than mullite porous brick.Mullite foamed sample has longer and stable thermal fatigue life than that of mullite perforated brick in the range of test temperature from 400? to 1000?.