Study On Properties And Crystallization Mechanism Of Slag Glass-ceramics Prepared By Microwave Irradiation

The large amount of mining and metallurgical solid waste generated and deposited not only occupies land resources and greatly causes environmental pollution,but also seriously hinders the sustainable development of the natural environment and ecological civilization construction.As the composition of mining and metallurgical solid waste contains a large amount of Si O₂,Al₂O₃,Ca O,Mg O,etc.,using it to prepare slag glass-ceramics is one of the important ways to realize the high value and resource utilization of solid waste,to solve the contradiction between the sound and sustainable development of green industry and resources and environment,and to accelerate the development of solid waste-based construction and industrial new materials industry.In this study,based on glass forming theory,slag glass-ceramics were obtained by two processes,ohmic heating,and microwave irradiation,using typical mineral and metallurgical solid waste such as dolomite tailings,fly ash,iron-rich tailings,stainless steel slag,and copper slag as the research objects.The synergistic-coupling relationship between the slag components,the relationship between the crystallization properties and the performance of glass ceramics,and the high-efficiency preparation of glass ceramics by microwave irradiation are the objectives of the study.With the help of XRD,SEM,DSC,FT-IR,Raman,and other testing methods,we systematically investigated:1)the effect of the ohmic heating regime on the mineral phase structure and physical and chemical properties of glass ceramics;2)the crystallization properties of glass by microwave process and microwave effect and Fe₂O₃,Ca F₂synergistic-coupling on ion migration,diffusion mechanism;3)comparison of ohmic heating and microwave irradiation process Ce O₂migration pattern on the crystallization characteristics;4)multi-solid waste system in the type and content of Fe ions,heating mode on the slag glass structure,crystallization characteristics and properties of the regulatory role.The main research conclusions obtained are as follows:（1）Firstly,glass ceramics were prepared by using dolomite tailings as the main raw material to investigate the effect of conventional heat treatment systems on the mineral structure and properties of slag glass ceramics.Compared with the conventional two-step crystallization method,the glass creep and structural activation by increasing T_grelaxation time promote augite crystallization.The heat treatment system effectively improves the crystallization ability,augite grain refinement,and the degree of self-forming crystals,thus optimizing the overall performance of the material and increasing the thermal stability and three-point bending strength.（2）Secondly,the experimental formulation was optimized to make synergistic use of dolomite tailings and fly ash to prepare slag glass ceramics by two heat treatment processes,ohmic heating,and microwave irradiation.It was found that microwave irradiation heat treatment,lowering the glass crystallization temperature,induced homogeneous augite crystallization and grain size refinement.The synergistic effect of microwave thermal and non-thermal effects improved the declustering ability of the glass network structure,increased the number of ionic defects in the glass network structure,induced non-uniform nucleation and crystallization of glass,and reduced the activation energy of crystallization of glass.At the same time,the coupling effect of microwave electromagnetic field and wave-absorbing medium in the glass during crystallization enhances the migration and diffusion efficiency of ions,leading to the aggregation of Fe ions and Ca F₂in glass ceramics to form a"micro-focusing effect",which increases the value of nucleation agent.（3）Based on the preparation of slag glass-ceramics based on Bayan Ebo tailings with fly ash as the main raw material,doped with 0%-3%content of Ce O₂.To investigate the effect of Ce O₂on the crystallization behavior of glass ceramics and the migration pattern of Ce ions in the effect of ohmic heating and microwave irradiation.The results show that a small amount of Ce O₂doping promotes the crystallization of augite,and with the increase of Ce O₂content,Ce⁴⁺cannot be completely reduced to form[Ce O₄]structural units,and[Ce O₄]couples with alkali metal ions to form stable glass structure groups,which inhibits the glass network polymerization and leads to the inhibition of augite crystallization..Further,the relationship between temperature and glass structure during microwave irradiation and conventional ohmic heating was investigated by the Raman spectroscopy method.The results show that the microwave effect effectively lowers the glass structure transition temperature,enhances the aggregation of glass networks,and induces the conversion of Ce³⁺to Ce⁴⁺in the parent glass,which reduces the augite crystallization efficiency.（4）In order to clarify the crystallization characteristics of Fe₂O₃on slag glass ceramics.Fe₂O₃was added to iron-rich tailings to prepare slag glass ceramics,and the effects of Fe content and iron ion valence changes on glass crystallization properties were investigated.The results showed that a small amount of Fe₂O₃could be used as a nucleating agent to promote augite crystallization.With the increase of Fe₂O₃content,[Fe O₄]formed by Fe³⁺combines with[Fe O₆]formed by Fe²⁺to induce the crystallization of magnetite,and the augite crystallization is inhibited.The relationship between magnetite and augite crystal growth was analyzed by the EBSD test technique,and it was determined that magnetite and augite have a common crystal growth interface,and magnetite can be used as a crystalline nucleating agent in glass-ceramics.However,magnetite precipitation reduces the Fe ion content in the glass,decreases the crystalline nucleating agent content,increases the glass viscosity,and thus inhibits augite crystallization.Further,the magnetic properties of the glass-ceramics were tested using MFM and VSM,and factors such as magnetite content,crystallographic orientation,grain size,and structure modulate the magnetic properties of the materials to different degrees.（5）In order to investigate the general rule of iron ion on the crystallization characteristics of slag glass-ceramics.In the study,fly ash,stainless steel slag,and copper slag（as a supplement to Fe₂O₃）were used synergistically to design formulations for the preparation of augite slag glass ceramics.To investigate the effect of the migration mode of Fe ions on the crystallization properties of glass ceramics during microwave irradiation and ohmic heating.The experimental phenomenon shows that the microwave field coupled with Fe ions promotes augite crystallization.With the increase of Fe ion content,the crystallization of magnetite was induced.It can be seen that the excessive content of Fe³⁺ions promotes the preferential binding of Fe³⁺-O with Fe²⁺-O and induces magnetite crystallization.In addition,it is known that the heavy metal Mn,Zn,and Cr ions in stainless steel slag and copper slag enter the spinel in the glass crystallization process,and the spinel induces the augite to epitaxially grow its crystallization.The spinel and augite form a core-shell structure,which enables the augite to form a complete wrapping around the spinel and effectively prevents the migration and diffusion of heavy metal ions.Thus,it is concluded that glass ceramics is one of the effective ways to co-cure heavy metals.The above study shows that the preparation of slag glass ceramics using the microwave irradiation process is fully feasible.Based on this study,it is clarified that the microwave effect generated by microwave irradiation can reduce the activation energy of crystallization and promote augite crystallization.It is clear that the microwave-material interaction depends on the structure and composition of the glass and its crystallization properties,and the wave-absorbing medium is the source of promoting crystallization.This study provides theoretical guidance and data support for the preparation of materials by comprehensive utilization of mining and metallurgical solid waste in China.