Preparation Of Alumina Ceramic Friction Materials With Waste Slag Of Aluminum Factory

A great deal of milky colloidal solution is produced during the surface treating procedure of aluminum factory, which is usually precipitated and filtered to form a solid state material called waste slag. In this thesis, waste slag of aluminum factory as a substitute for commercial alumina was used as main raw material with clay, flux and solid lubricant to prepare alumina ceramic friction materials under normal pressure and low temperature. It not only lower the cost of raw materials, but also protect environment and reuse the waste slag. Therefore, it has good econormic and social benefits.In this thesis, the chemical composition, crystal phase and microstruture of waste slag of aluminum factory were analyzed and characterized by methods of chemical analysis, XRD and SEM. The transformation law of crystal phase and microstruture under differernt calcining temperature of waste slag were studied. By testing the water absorption, porosity, density, bending strength, micro-hardness, friction coefficient and wear rete of samples and combining the analysis results of XRD and SEM, the effects of the content of calcined waste slag and flux on properties and microstrutures of samples have been studied for determining the optimal prescription. On the basis of defining the optimal prescription, the effects of sintering temperature and holding time on the properties and microstruture of the prepared alumina ceramic friction materials have been dicussed to obtain the best sintering technical conditions, which offers the experimental references for using waste slag of aluminum factory as basic raw materials to prepare the alumina ceramic friction materials.The results indicate that the major composition of waste slag of aluminum factory is Al₂O₃ existed in form ofγ-AlOOH, partly in crystalline and partly in amorphous solid state. It has superfine particle and high activities. The waste slag of aluminm factory can be completely transformed into stableα- Al₂O₃ at high temperatures, and the content of Al₂O₃ can reach up to 90% or so. Therefore, the waste slag of alumimum factory can replace commercial alumina as main raw materials to make alumima ceramic friction materials. In order to keep the activity of waste slag and avoid deformation and crack of samples in the process of sintering, the waste slag must be pretreated. The optimal calcining temperature of waste slag was 1000℃.The effects of the content of calcined waste slag and flux on properties and microstructure of samples have been studied. The results show that the optimal prescription consists of 80% waste slag, 10% clay, 4.5% talc, 1.5% TiO₂ and 4% BN at 1300℃for 2h. The effects of the sintering temperature and holding time on properties and microstructure of samples have been discussed. The results indicate that the properties of samples reach the extreme value and the synthetical properties are the best under the following sintering conditions: the sintering temperture is 1320℃and holding time is 2h. The performance indexes are: the water absorption is 0.14%, the porosity is 0.41%, the density is 3.14g/cm³, the bending strength is 292Mpa, the micro-hardness is 9.93Gpa, the friction coefficient is 0.625, the wear rate is 5.53×10-6mm³(N·m)^-1.The analysis results of XRD and SEM indicate that the main crystal phase isα- Al₂O₃, including a small amount of spinel phase.α- Al₂O₃ take platelike shape and the body has dense structure.