Research On The Preparation Of Molybdenum Slag Glass-ceramics And Its Microstructure

The solid waste mining molybdenum residue, as the main raw material, was used to prepare high-performance construction decorative glass-ceramics by sintering process. The research which has a comprehensive effects on resources, environment and ecology also conforms to China’s strategic goals of sustainable development has important economic and social significance.The major components of molybdenum residue are SiO2, Al2O3, CaO and Na2O, which is proved from theory to meet the chemical composition requirements of preparing CaO-Al2O3-SiO2glass-ceramics. A group of basal glass formulas adding molybdenum residue50-80wt%have been designed in the paper. By a large number of exploratory experiments, the optimum heat treatment temperature system has been determined. Experiments of preparing the glass-ceramics made from molybdenum residue show that the decorative glass-ceramics whose surfaces are smooth and bodied are compact can be prepared when the molybdenum residue content is50-80wt%. The best crystallizing and nucleating temperature of1#glass contained80wt%molybdenum residue is: nucleation700℃, lh; crystallization850℃,2h. The best crystallizing and nucleating temperature of2#～4#glass contained70wt%-50wt%molybdenum residue is:nucleation700℃, lh; crystallization870℃,2h.The sintering molybdenum slag glass-ceramics samples performance excellent. Obvious porosity is0.50-3.07%, water-absorbing capacity0.20～1.29%, bulk density above2.39-2.49g/cm3, acidresistivity0.17-0.29%, alkali resistivity0.12～0.18%. Drying rate of shrinkage in length is0.05%, sintering rate of shrinkage in length is11.93～18.10%, total rate of shrinkage in length is11.98～18.14%. Diamond penetrator hardness is534.2-661.3HV. Bending strength46.02MPa-65.96MPa. Bending strength,bulk density and thermal dilatation of molybdenum slag glass-ceramics are smaller when adding molybdenum slag more while obvious porosity,water-absorbing capacity,rate of shrinkage are bigger,the performance of Acidresistivity and alkali resistivity are excellent. The thermal expansion coefficient of the glass-ceramics samples are4.15x10-6/℃-4.63x10-6/℃.Thermal stability is good.150℃-20℃, room temperature water-cooled, four kinds of glass-ceramics samples had no cracks in ten cycles. Add the right amount of flux such as albite or transparent frit2001to the glass-ceramics system (molybdenum slag from50%to80%) can significantly reduce the contraction of the glass-ceramics samples and the high-temperature viscosity of the glass, but the main crystalline phase didn’t change, can accelerate mass transfer, reducing nucleation and crystallization barrier, being more conducive to the growth of wollastonite, purifying the main crystalline phase of glass-ceramics.TG-DTA analysis showed that the four kinds of basic glass samples didn’t have obvious nucleation peak, but crystallization exothermic peak was obvious, and the area of exothermic peak is big. This kind of glass dosen’t prone to be softening deformed during heat treatment, crystallize well, cystalline grain is small, performance is good,one-step or two-step heat treatment process can be used. XRD analysis showed that the main crystalline phase of glass-ceramic had not been affected by the adding amount of molybdenum slag, were wollastonite (CaSiO3), also contained a very small amount of mullite phase.Crystallization decreased while residue added. SEM microstructure studies have shown that molybdenum slag glass-ceramic crystallization performance was good, the main crystalline phase of wollastonite were granular crystal grain with size of about0.05-0.5μm, a very small amount of rod-like or flaky crystals existed.0.05-50μm round closed pores equally distributed in the glass phase. This structure gives the sample good physical and chemical properties.The glass-ceramic crystallization kinetics studies have shown that the activation energy E of1#-4#glass-ceramics were13.49kJ·mol-1,44.35kJ·mol-1,141.4kJ·mol-1and55.29kJ·mol-1respectively. The Crystallization rate constant k (Tp) are9.47x10-3、3.08x10-2、1.24x10-1and3.81x10-2. The crystallization index are8.53,3.17,2.69and3.19respectively. The crystallization mechanism of the molybdenum slag glass is volume crystallization and whole crystallization. Simply select the appropriate heat treatment process, samples can precipitate microcrystalline well.