Effect Of The Composition And Heat Treatment On Performance Of Tailings Glass Ceramics Made By Direct-Sintering Method

Glass ceramics is a distributing material contained micro crystal and glass phase, which is made by the control of crystallization behavior of base glass. It has a low coefficient of thermal expansion with high mechanical strength, significant corrosion resistance, wear resistance, weather resistance and good thermal shock resistance. It has a broad application prospect in building, military, aviation, biomedical, mechanical engineering and other fields.Every year there were 2 tons of metal mine tailings discharged and most of them were disposed as wastes, which caused ecological damage, environmental pollutionand waste of resources. The content of SiO2 metal mine tailings is above 60%, other ingredients are also in the glass forming range which can meet the requirements of the chemical composition.In this paper,CaO-MgO-Al2O3-SiO2 system glass ceramics were prepared using iron tailings as raw material.At present the main glass ceramics preparation methodsare the overall crystallization method(melting process) and sintering method. The two kinds of methods all require high melting temperature, long production cycle and high energy consumption.In this paper, aiming at the above problems the effect of mixing ratio of basic oxide and types of flux with different additions and heat treatment regime on the glass ceramic sintering and crystallization properties of iron ore tailings were investigated, respectively, which considered the maximum use of the premise of iron ore tailings and focused on the key problem on how to reduce the temperature of the preparation,and proposed a new way of preparing glass ceramics from the tailings of directly sintering systemResearch results of the basic composition of the oxide showed that, it can be concluded from the variance analysis on the results of orthogonal testof materials composed by basic oxide that, the effect degree of the four kinds of oxides on the crystallization temperature of the glass ceramic was CaO>SiO2>Al2O3>MgO,in which the content of CaO had significant effect on the crystallization temperature.And with the increased content of CaO, temperature of glass-ceramic nucleation and crystallization decreased; acid resistance, density and compressive strength of glass ceramic increased first and then decreased.With the crystallization temperature as evaluation indexes, the optimal ratio of based oxide was SiO2:55%, CaO:18%, MgO:10%, Al2O3:7% through orthogonal test.In this compositionthe nucleation temperature was 830℃ and the crystallization temperaturewas 925℃, precipitation the main crystal phase was diopside and the secondary crystalline phase was anorthite.In order to lower the sintering temperature of batch and get better sinter qualitywithin the limited firing time, this paper added different kinds of flux with different additions according to the optimal ratio of base oxide. The initial sintering temperature and the temperature range of sintering and the volume density of sintering product were made as evaluation index studying on the effect of flux on the sintering performance of glass.The results showed that, when Na2O+K2O and CaF2 were compound used, the best addition was 4%. Compared with not adding cosolven, the initial sintering temperature was effectively reduced for 70℃, the range of temperature was expanded for 55℃,the volume density increased for 1.06g/cm3.Based on composition of the basic oxideand mixing co-solvent determined in the above, this paper studied the heat system of mixtures treated by directly sintering method. The results showed that, with the increase of time of sintering and time of crystallization, The amount of crystallization of iron tailings glass ceramics increased first and then decreased and the nucleus size gradually increased, which led to the bulk density of glass ceramics products increased first and then decreased.In ensuring the premise of crystallization rate reached above 50% with the bulk density as assessment index., the sintering time of the heat treatment system ultimately determined were 60 min respectively and the crystallization time was 60 min, and the heating rate was 10℃/min through the orthogonal optimization.