The Preparation Of Anorthite/Mullite Composite Material And Its Lightweight Refractories

Energy conservation and emissions reduction is a very important problem for high temperature industry such as metallurgy,building materials,chemical industry and so on.The development of anorthite/mullite lightweight refractory materials with high performance for industrial energy saving and environmental protection is of great significance.The effect of different mineral compositions on the synthesis of anorthite and the phase composition and microstructure of anorthite/mullite material were studied.Using starch as pore-forming agent,the anorthite/mullite lightweight refractory materials were fabricated by starch in-situ consolidation.The anorthite and anorthite/mullite composite materials were fabricated by using different kinds of raw materials.The effect of different mineral compositions of raw materials on the phase composition and microstructure of anorthite/mullite materials were studied.It was found that wollastonite and gehlenite phases were firstly formed from quartz?fused quartz or quartz sand?,Ca?OH?₂,?-Al₂O₃ and then formation of anorthite.Mullite phases were obtained by corundum and cristobalite reaction after fired at 1350?.However,using the natural wollastonite or calcium aluminate powder and natural Al₂O₃-SiO2 system raw materials like kyanite and clay as raw materials,anorthite could be directly formed and mullite could be obtained by the process of mullitization.The major phases were anorthite,mullite and a little corundum in the specimens sintered at 1400?.The crystals of anorthite and mullite existed together in anorthite/mullite composite materials,and the crystal size of columnar mullite was large,while the size of anorthite crystallites sizes was small.The anorthite/mullite lightweight refractory materials were fabricated by starch insitu consolidation,using kaolin,wollastinite,kyanite,?-Al₂O₃,Ca?OH?₂ as raw materials.The different kinds of starches?the starch of corn,wheat,potato,cassava and sweet potato?were used as pore forming agent and binder.The influence of types of starch on viscosity of the slurry,strength of green body samples,pore and properties of samples after sintered were studied.The results show that the temperature range in which the different starch removed by calcining was almost the same,between 200?-300?.Because the slurry with corn starch had higher viscosity and most of the wheat starch in the slurry after pasting formed spherical particles to increase the pressure anddegree of binding between powder particles,their green bodies after drying would have greater compression strength?5.37 MPa and 5.26 MPa respectively?than others.The sintered samples with wheat starch had the maximum compression strength?9.12MPa?,because of most of spherical pores existing in the sample which was smaller than those in other samples.When the size?d0.5?of the starch was greater?potato> corn> wheat>cassava> sweet potato?,the volume after it gelatinization was greater.And the sample after sintering had the larger pore diameter,higher apparent porosity and lower bulk density.The anorthite/mullite lightweight refractory materials were also prepared by adding foaming agent of AC and SDS.The effect of foaming agent on the properties of materials was studied.Adding to the foaming agent,the obvious foarming effect took place in the low viscosity slurry with wheat starch.By means of starch and foaming agent forming pore the lightweight refractory materials with excellent properties can be obtained.The anorthite/mullite lightweight refractory materials developed in this study have good properties,and it is superior to similar products in industrial application at present.