Preparation And Performance Research Of Phosphorus Slag-gangue Glass-ceramics

As China's industrialization and urbanization process continues to accelerate,the number of cities continues to increase,industries and populations continue to gather in urban areas,and emissions of various industrial solid wastes increase year by year.As the environment itself has limited capacity to carry these industrial solid wastes,it triggers a range of environmental and ecological problems.Phosphorus slag and coal gangue are one of the industrial wastes with relatively large emissions in China,and they are also very valuable reusable resources.For phosphorus slag,its main components are SiO₂ and CaO,which are high-silica-calcium materials.For coal gangue,its main components are SiO2and Al₂O₃,which are high-silicon-aluminum materials.Theoretically,the composite of the two can prepare CaO-Al₂O₃-SiO₂ system glass ceramics.Due to its excellent performance,glass-ceramics have been widely used in defense technology,electronics,biomedicine,architectural decoration and other fields,and have broad development prospects.In recent years,domestic and foreign scholars have carried out a lot of research on the preparation of glass-ceramics from industrial solid waste,and the preparation of glass-ceramics by various solid waste composites has received extensive attention.However,in the process of preparing glass-ceramics by industrial solid waste,industrial solid waste often cannot meet the conditions for directly preparing excellent glass-ceramics due to limitations of its own chemical composition and its content.The use of industrial solid waste combined with excipients to prepare glass-ceramics not only increases the cost of preparing glass-ceramics,but also causes problems such as low utilization rate of industrial solid waste.In order to solve these problems,this paper studies the preparation of phosphorus slag-gangue total solid waste glass-ceramics,exploring the way to prepare glass-ceramics at low cost;studying the influence of different phosphorus slag and coal gangue ratio on the melting properties of base glass and the crystallization property of glass-ceramics,and determining the best ratio of phosphorus slag and coal gangue;From the perspective of reducing energy consumption,the best proportion of phosphorus slag-coal gangue composite and phosphorus slag were used to prepare glass-ceramics.The microstructure and macroscopic properties of glass-ceramics were studied.Based on the determination of the optimum ratio of phosphorus slag and coal gangue,the influence of heat treatment temperature on the microstructure and macroscopic properties of phosphorus slag-coal gangue glass-ceramic was studied,and the optimum heat treatment temperature was sought.Finally,the preparation of phosphorus slag-coal gangue porous glass-ceramics was explored,and the effect of calcium carbonate content on the structure and properties of porous glass-ceramics was studied.Through the above research,the following conclusions were obtained:?1?The ratio of phosphorus slag to coal gangue was selected as 8:2,6:4,4:6,2:8 for trial melting and heat treatment experiments.As the amount of phosphorus slag is increased,the melting temperature of the base glass gradually decreases from the highest 1500�Cto1250�C,which is due to the fact that the amorphous form of the phosphorus slag has a good fluxing effect.It was found that when the ratio of phosphorus slag to coal gangue is 8:2,the base glass can be melted and clarified only at 1250�C,and the crystallization property is good,and pseudo-wollastonite crystal can be precipitated.?2?Phosphorus slag-coal gangue base glass powder and phosphorus slag were heat treated at 950�C for 2 h to prepare the glass-ceramics with the main crystal phase as wollastonite crystal phase.With the decrease of phosphorus slag content,the wollastonite phase crystals were precipitated.The number is gradually increased,increasing the viscosity of the glass phase,causing the sintering to be hindered,resulting in a large amount of pores remaining inside the glass ceramic sample.As the amount of phosphorus slag increases,the relative content of the glass liquid phase decreases,forming a viscous effect,which hinders the densification of the sample,so that the water absorption rate and porosity of the glass ceramic sample gradually increase,and the sintering shrinkage rate and bulk density gradually decrease.?3?During the heat treatment of phosphorus slag-gangue glass-ceramics,the crystallized glass precipitates as a spherical shape at the heat treatment temperature of 750�Cand 800�C.At this time,the main crystal phase Ca₃?Si₃O₉?phase of the glass ceramics begins to appear.In the CaSiO₃ crystal phase,the crystal grains adhere to each other and tend to grow further.As the temperature rises to 850�C,the crystal gradually develops and transforms from spherical to acicular.The main crystalline phase of glass-ceramics changes from Ca₃?Si₃O₉?to CaSiO₃,and the crystal distribution tends to be uniform;when the heat treatment temperature rises to At 950�C,the needle-like crystals disappeared in the glass ceramic,and short columnar CaSiO₃ crystals appeared.Continue to raise the temperature to 1000�C,the short columnar CaSiO₃ crystals grow further,and the spherical crystals,short columnar crystals and glass phases are inlaid with each other to form a tight network structure,which is advantageous for the toughness of the sample.?4?With CaCO₃ as the foaming agent,the CaCO₃ dosage increased from 2%to 12%.The apparent density of the porous glass-ceramic sample decreased first and then increased,and the porosity first increased and then decreased,and the compressive strength first increases and then decreases.When the amount of CaCO₃ is 6%,the apparent density of the porous glass-ceramics can reach 0.86g.cm^-3,the porosity can reach 70.3%,and the crystallization phase is a single wollastonite crystal phase structure.After many experiments,it was found that the porous microcrystalline glass green body began to be sintered and densified at 760�C,and obvious pores appeared at around 850�C.