用粉煤灰和菱镁矿低温制备堇青石质多孔材料

在粉煤灰中添加不同比例菱镁矿,于1 200、1 250℃和1 300℃烧成温度下制备出堇青石质多孔耐火材料。研究表明：菱镁矿在烧成过程中于700℃分解产生CO2,起到造孔剂和发泡剂的作用,分解生成的MgO将与粉煤灰中的Al2O3、SiO2反应生成堇青石;随着菱镁矿添加量的增加,粉煤灰中Al2O3和SiO2与MgO的反应更完全,主要生成堇青石和少量镁橄榄石;当菱镁矿添加量过多时,新生成的MgO与粉煤灰中SiO2反应,产生液相过多,造成部分气孔封闭,使得烧成后试样的显气孔率随菱镁矿添加量的增加呈先增加后减小的趋势。优化烧成工艺条件为1250℃并保温3h,当菱镁矿添加量为15%（质量分数）时,制备出显气孔率达48%、孔径为20～40μm、体积密度为1.27g/cm3、抗压强度为38MPa、抗折强度为29MPa的堇青石质多孔材料。

Low-Temperature Preparation of Porous Cordierite Materials with Fly Ash and Magnesite

The porous cordierite materials were prepared with fly ash and magnesite as raw materials at 1 200, 1 250 ℃ and 1300 ℃, respectively. It was indicated that magnesite could be used as a pore-forming agent and a foaming agent during the formation of porous cordierite materials since the magnesite produced CO 2 at 700 ℃ in the firing process. MgO obtained from the decomposition of magnesite could react with Al2O3 and SiO 2 in fly ash, leading to the formation of cordierite. The results show that the reaction among Al2O3 , SiO 2 and MgO is more complete as the addition of magnesite increases, and cordierite is the main product with a small amount of forsterite. However, the interface reaction between newly generated MgO and SiO 2 was proceeded and a mass of liquid phase was generated as the excessive amount of magnesite was added, causing the sealing of the partial pore. The porosity of porous cordierite ceramics firstly increased and then decreased with increasing magnesite addition amount. The optimal calcination process occurred at magnesite addition of 15% (mass fraction) and 1 250 ℃ for 3h. The porous cordierite materials prepared via the optimized process exhibited the superior properties (i.e., apparent porosity of 48%, pore size of 20–40 μm, bulk density of 1.27 g/cm 3 , compressive strength of 38 MPa, and flexural strength of 29 MPa).