低导热微孔刚玉骨料的湿法制备及其抗渣机制研究

Fabrication of low thermal conductivity microporous corundum aggregate by wet process and its slag resistance mechanism

为了制备轻质高强且耐渣蚀的工作衬耐火材料,首先以α-Al_2O_3微粉为主要原料,采用铝溶胶、淀粉为结合剂,通过湿磨法经1 780℃煅烧后制备了一种微孔刚玉骨料,其体积密度为3.05 g·cm^(-3),显气孔率为9.1%,闭口气孔率达12.3%,中位孔径为0.43μm,800℃下热导率为6.5 W·m^(-1)·K^(-1),较普通刚玉降低41.6%。然后采用浸泡法研究了微孔刚玉骨料的抗渣性能,并与普通刚玉骨料进行对比研究,以揭示微孔刚玉骨料的抗渣机制。结果表明:微孔刚玉骨料的抗渣性能明显优于普通刚玉骨料的。显微结构及能谱分析显示:在微孔刚玉骨料与熔渣反应界面形成了一层连续的隔离层,隔离层中主要为大量的CA_2及CA_6柱状晶体;而普通刚玉骨料与熔渣反应界面的柱状晶体分布则不连续,熔渣大量侵蚀或渗透进入骨料内部。其抗渣机制主要是微孔更有利于CA_2及CA_6柱状晶体成核、长大,由于微孔刚玉骨料孔径更为细小,在熔渣与骨料反应过程中熔渣达到饱和时,微孔刚玉及普通刚玉的临界溶解厚度分别为0.16及0.34μm;并且第二相熟化速率增大,微孔刚玉骨料的第二相熟化速率为普通刚玉的9.7倍。

Microporous corundum aggregate was prepared by wet grinding process and calcining at 1 780 ℃,using α-Al_2O_3 micropowder as the main raw material,as well as alumina sol and starch as binders in order to fabricate lightweight lining refractories with high strength and good slag resistance. The microporous corundum aggregate had the bulk density of 3. 05 g·cm^（-3）,the apparent porosity of 9. 1%,the closed porosity of12. 3%,the median pore diameter of 0. 43 μm. The thermal conductivity of the microporous corundum was 6. 5W·m^（-1）·K^（-1） at 800 ℃,41. 6% lower than that of common corundum. The slag resistance of the microporous corundum aggregate was studied by the immersion method and compared with that of the common corundum aggregate to reveal the slag resistant mechanism. Experimental results show that the microporous corundum aggregate has obviously better slag resistance than the common corundum aggregate. On the reaction interface between microporous corundum and molten slag,a continuous isolation layer,mainly consisting of columnar crystals of Ca Al_（12）O_（19）（ CA_6） and CaAl_4O_7（ CA_2）,is observed. However,on the reaction interface between common corundum and molten slag,the distribution of columnar crystals is discontinuous,and the aggregate is significantly corroded and penetrated by molten slag. The mechanism is mainly that the microporous structure is more advantageous to nucleation and growth of CA_2 and CA_6 columnar crystals. In the reaction with the aggregate,the molten slag gets saturated and the critical solution thickness of the microporous corundum and the common corundum is 0. 16 μm and 0. 34 μm,respectively,this is caused by the smaller microporous corundum aggregate pores. The smaller pores also increase the second phase ripening rate of microporous corundum,which is 9. 7 times of that of the common corundum.