Mechanism Of Action Of B₂O₃ On MgO-Al₂O₃-SiO₂ System Glass-ceramics

With the rapid development of the iron and steel industry,solid waste such as tailings has accumulated in large quantities,which not only harms the ecological environment seriously,but also causes the loss of mineral resources.Achieving the tailings resource utilization is an important subject for the development of circular economy and sustainable development.Glass-ceramics is a new type of solid material made by sintering a variety of oxides.It has good mechanical strength,good corrosion resistance,and excellent insulation properties.It is used in the field of mechanical engineering,metal sealing and biomedical widely.The solid waste such as tailings or boron mud containing various oxides can be used as raw materials for the production of glass-ceramics through reasonable batching,which not only reduces the production cost of glass-ceramics,but also realizes the recycling of solid wastes such as tailings and creates more value.Flux is considered to be an important influencing factor in the preparation of glass-ceramics.Adding a suitable oxide as a flux to the glass system can reduce the high temperature viscosity of the glass,improve the melting performance,and then enhance the overall performance of the glass-ceramics.In this study,chemical pure substances were used as raw materials to simulate tailings components,glass-ceramics was prepared by sintering method,differential thermal analysis was used to determine the nucleation and crystallization temperature,X-ray diffraction was used to determine the type of mineral phase,SEM observed the microstructure,and infrared spectrum was used to analyze the effect of the structure of B₂O₃ added to the glass on the crystallization process,the law of crystallization was studied by kinetic calculations,and the effect of the amount of B₂O₃ addition on the crystal form transition and microstructure of the main crystal phase were summarized.The effect of different oxide additions on improving overall performance was also studied.The mechanism of B₂O₃ as flux on the structure and properties of MgO-Al₂O₃-SiO₂ glass-ceramics was investigated comprehensively.Thefollowing conclusions can be drawn:?1?When B₂O₃ in two different forms of [BO3] or [BO4] exists in glass,it has different effects on the crystallization process of glass-ceramics.When the amount of B₂O₃ added was 3%,[BO3] was less than [BO4] in the sample and [BO4] will destroy the network structural integrity,which can reduce the nucleation and crystallization temperature;?2?The amount of B₂O₃ added has different influences on the control of the crystallization behavior of microcrystalline glass,the microstructure and the crystal structure of the main crystal phase.Kinetic calculations showed that when the amount of B₂O₃ added exceeds a reasonable range,the crystallization activation energy increases,and the crystallization mode changes from overall crystallization to surface crystallization,which is not conducive to the good precipitation of the crystals.At the same time,the increase in the amount of B₂O₃ added will promote the transformation of ?-cordierite to ?-cordierite,the resulting glass-ceramics structure also becomes loose;?3?Under the conditions of this study,it was found that when the amount of B₂O₃ is 3%,glass-ceramics with excellent comprehensive performance can be obtained.The relative dielectric constant of the obtained product is 5.79,the dielectric loss is 0.0039,the apparent porosity is 1.59%,and the water absorption is 0.66%,bulk density is2.3968 g/cm³,and the rockwell hardness is 56.7 HRC.