Study On The Relationship Between The Composition,Preparation Parameters And Properties Of Foam Thermal Insulation Ceramics With Coal Mine Waste

Coal gangue and associated shale are coal mine solid wastes with huge emissions,polluting surrounding land,water and air,causing serious environmental problems.On the other hand,there are fewer kinds of self-insulating materials which can be used in building envelopes with good mechanical and thermal insulation properties,so it is urgent to develop new self-insulating wall materials.In this study,foam thermal insulation ceramics were prepared by using coal gangue and shale as the main raw materials,talc as a fluxing agent and polishing slag as a pore-forming agent.Based on the analysis method of ternary phase diagram,the SiO₂-Al₂O₃-MgO ternary system was designed to carry out experimental research to solve the material design and preparation problems when the composition of raw materials fluctuated greatly in different mining areas or different sampling points.The mineral composition of foam thermal insulation ceramics was determined by XRD.The pore structure and distribution were analyzed by Image J software.The SiO₂-Al₂O₃-MgO ternary system diagram of porosity,bulk density and water absorption rate was plotted by Matlab software.The influence of chemical composition on mineral composition,pore structure,porosity,bulk density,water absorption,compressive strength and thermal conductivity of foam thermal insulation ceramics was studied.This optimizes the range of composition and proportion of materials.The results show that the main mineral composition of foam thermal insulation ceramics is cordierite and enstatite,and the amount of cordierite and enstatite is mainly related to the amount of MgO.The suitable chemical composition ranges from SiO₂ 72%to 75%,Al₂O₃ 16%to 19%,and MgO 9%to 12%.At this time,the main phase of foam thermal insulation ceramics is cordierite,the pore size distribution is uniform,the average pore size is 0.55⁰.65 mm,the porosity is greater than 70%,the water absorption is less than 0.8%,the compressive strength is greater than 10 MPa,and the thermal conductivity is less than 0.36 W/?m k?.Taking the process parameters such as firing temperature,holding time and milling time as factors,the effects of the process parameters on the mechanical properties and thermal conductivity of foam thermal insulation ceramics were studied,and the optimum technological parameters for preparing foam insulation ceramics were determined.The results show that the process parameters are more suitable for firing temperature of more than 1200 degrees,holding time longer than 30 minutes and milling time longer than 40 minutes.When the firing temperature,holding time and milling time were 1220 degrees,30 minutes and 40 minutes respectively,the pore distribution of foam thermal insulation ceramics was uniform,porosity was greater than82%,compressive strength was more than 6 MPa,and thermal conductivity was less than 0.17 W/?m k?.