Surface Modification Of Alumina Bubble And The Application In Lightweight Castable

As the situation of resources and environment in China become increasingly serious, it’s necessary for high energy consumption industry such as iron and steel, metallurgy, petroleum and chemical industry to achieve the goal of energy conservation and emission reduction. Lightweight refractories with low density, low thermal conductivity and low line change could be used for reducing the heat loss of furnace and also saving the cost of equipment construction industrial furnace and thermal costs, reducing furnace heat, and then researchers have paid enough attention to the lightweight refractories. Alumina bubble is an ideal light aggregate which has great practical significance and theoretical value.In this paper, nano barium sulfate and nano calcium fluoride were used for modifying the alumina bubble with inherent defects. Castables were prepared with alumina bubbles as light aggregates, and then the effects of grading, addition of micro powder on the property of castables were studied. The inner mechanisms of how the factors affect the composition, structure and strength of castables were also described.(1) Nano barium sulfate was synthesized in liquid method by adjusting the pH value to5.2at room temperature. The products were uniform with the size less than50nm. Nano calcium fluoride was synthesized in different calcium ion concentrations with good morphology and uniform size.(2) After being modified and heated, the surface of alumina bubbles were coated uniformly, and the strength of alumina bubble modified was much higer than that of untreated one. When alumina bubbles been modified were used as aggregates, we got lightweight castables wit higher strength.(3) Best grading of castables was obtained by the experiment, and the effect of α-Al2O3micro powder on the properties of castables was also studied. Castables with low micro powder exhibited high liquidity, whereas with high content of α-Al2O3, it was functioned as the matrix material. Adjusting porosity in certain range, volume of closed pore was regarded as a linear function to the volume of open pore with a negative correlation.(4) Barium sulfate could decompose at1400℃and react with the matrix material to produce hex-celsian. Calcium fluoride could decompose at1400℃and the calcium hexa-aluminate with small amount of gehlenite were formed. There was volume expansion during the formation of calcium hexa-aluminate, which was the main reason for the change of castables.(5) After the addition of barium sulfate and calcium fluoride, castables got lower strength and high erosion resistance to molten aluminum. The erosion resistance to castables increased by barium sulfate got much higher than that increased by calcium fluoride.