Synthesis And Application Of Mullite/cordierite Composite Materials From Waste Slag Of Aluminium Factory

Mullite / cordierite composite materials, a new kind of kiln refractory, is applied to various kinds of porcelain products extensively. The conventional approach of manufacturing this kiln is done by synthesizing mullite and cordierite separately with industrial alumina firstly, and by developing kiln materials with different proportion of mullite and cordierite secondly. In this study, mullite / cordierite composite materials was synthesized successfully by using waste slag of aluminium factory directly, and then used to develop the kiln. Therefore, comparing this method with the existent method, there is an innovation on raw materials, technology and craft of this method, and an important environmental protection meanings. XRD (Philips.X'pert-MPD X-ray diffraction instrument) and SEM techniques (philips.XL3DE SEM ) were used to analyze and characterize the crystal phase structures and micro-structures of every sintered specimen, and the compositions of crystal phases were determined by the Rietveld Quantification method. The unit cell parameters in different specimen were calculated through X'pert plus software; The properties such as bending strength, water adsorption and porosity were also tested in this research. On the basis of the compositions of Germanic mullite / cordierite kiln (mullite and cordierite content account for about 50% separately), different prescriptions of synthesized materials were made up. The influences of different prescriptions, sintered temperature and holding time on the crystal phase structures and micro-structures of every sintered specimen ware discussed for determining the optimal prescription, and then the optimal prescription of kiln materials and the control conditions of technology were determined according to the performance of kiln materials. Through XRD analysis, the results show that three crystal phases of mullite, cordierite and magnesium aluminium spinel in different prescription were formed at most . The optimal prescription was D sample (48% of waste slag of aluminum factory , 36% of clays, 16 % of talc ), and its sintered materials contains about 50% of mullite and 50% of cordierite. The level of Germanic mullite / cordierite kiln is achieved; The optimal sintered temperature was 1350 ℃ and the holding time was 2 hours. In order to increase the ratio of mullite / cordierite in sintered materials and therefore improve the using temperature of the kiln ,the content of waste slag (mainly contains Al2O3 ) was increased and the content of talc (mainly contains MgO ) was reduced in prescriptions. The influences of different prescription and sintered temperature on the crystal phase structures and micro-structures of every sintered specimen was researched. By XRD analysis , the results show that four kinds of crystal phases of mullite, cordierite, magnesium aluminium spinel and α—Al2O3 were formed in different ingredients sintered at 1350℃, and two kinds of crystal phases of mullite and cordierite were formed in different ingredients sintered at 1370℃; and four crystal phases of mullite, cordierite, magnesium aluminium spinel and α—Al2O3 were formed in different ingredients sintered at 1390℃,and five crystal phases of mullite, cordierite, magnesium aluminium spinel, α—Al2O3 and SiO2 were formed in different ingredients sintered at 1410℃.The analysis results show that synthetic materials at 1370℃ was the optimal one. The influences of different prescriptions and sintered temperatures on the performance of kiln materials of every specimen was discussed by preparing kiln with the synthesized materials separately at 1370℃,1390℃ and 1410℃ . The results show as follows: the optimal prescription of preparing kiln with synthesized materials at 1370℃ was 3# and the optimal sintered temperature was 1370℃, and the optimal prescription of preparing kiln with synthesized materials at 1390℃ was 1# and the optimal sintered temperature was 1370℃, and the optimal prescription of preparing kiln with synthesized materials at 1410℃ was 1# and the optimal sintered temperature was 1390℃. The suitable amount of CaO mineralizer and feldspar can promote and improve the sintering process and intensity of kiln materials. Therefore, the optimal content is 1.0 % of CaO and 2.0% of feldspar.