Integrated Design And Preparation Of Composition And Performance Of Coal Mine Waste Foam Thermal Insulating Ceramics

The low utilization rate of coal gangue and shale in coal mine has caused serious environmental problems.The energy-saving of buildings requires enclosure materials with good thermophysical and mechanical properties.Motivated by the two urgent problems that the coal gangue is to be reused and self-insulating wall materials with reasonable thermophysical properties is needed to achieve energy conservation in buildings,this project proposed a sintered wall material preparation method which is expected to prepare materials meet the requirement of thermophysical and mechanical properties of building walls by using solid wastes from coal mine as the raw material,polishing slag as the main pore-forming agent and talc as the fluxing agent in hot and humid climate region.The relationship among the preparation technology of the sintered wall material,phase composition,microstructure,thermal conductivity,thermal inertia index,coefficient of thermal storage,hygroscopicity and the mechanical properties is researched in order to seek the theoretical foundation for integrated design of the structure of materials,strength and thermalphysical properties.Since the chemical composition of coal gangue and shale at different time and location varies greatly,a ternary phase diagram of SiO2-Al2O3-MgO which draws the isolines of mechanical properties and thermophysical properties is designed to investigate the influence of composition and structure of materials on the properties of the foam insulation ceramic,and achieve the purpose of integrated design and preparation of thermophysical l properties and mechanical properties of materials.A controllable preparation method and technique which meet the requirement of material design is studied.The results show that:?1?The bulk density of the foam insulation ceramic sintered at 1200?,with the sintering rate of 10?/min is under 0.77g/cm³,the porosity is greater than 70%,the water absorption is lower than 0.59%,the thermal conductivity is less than 0.14W/?m?k?,the thermal storage coefficient is no more than 3.2W/?m²?k?,the specific heat capacity is 0.52⁰.61kj/?kg?k?,the thermal diffusion coefficient is less than0.159�10^-2m²/h,the thermal inertia index is higher than 3.36,the material attenuation multiple is higher than 12.27,and the delay time is longer than 2.9h when the proportions of MgO is from 9%to 10%,Al2O3 is between 17%and 19%,and SiO2 is from 71%to73%.?2?Within the range of 71%⁷3%SiO2 content,17%¹9%Al2O3 content and9%¹0%MgO content,the main crystal phase of foam insulation ceramics were cordierite.?3?The microscopic analysis and thermophysical properties analysis of the material demonstrate that the porosity and pore characteristics are the main factors affecting the thermal conductivity of the material.The structure of the material and mineral composition also influence the thermal conductivity.The main crystalline phase of the foam insulation ceramic sintered with the solid waste from coal mine are the cordierite and enstatite.The cordierite crystals with complex structure has greater effect on lattice wave scattering process and smaller heat conduction,while the heat conduction of the enstatite containing lower atomic weight Mg²⁺in the structure is better.In other words,the thermal conductivity of cordierite is lower than that of enstatite.The phase composition of cordierite and enstatite increases the specific heat capacity of foam ceramics.At the same time,gaps and cracks in the pore walls cause scattering of phonons and decrease the thermal diffusion coefficient.