Study On Porous Thermal Insulation Ceramic Composites Prepared By Low-grade Potassium Feldspar

The use of thermal insulation materials is an effective way to reduce building energy consumption,and porous thermal insulation ceramics have been widely used in recent years due to their excellent non-combustibility,durability,and good thermal insulation performance.Minerals are often used as the raw materials for the manufacture of building materials.The production of thermal insulation materials and foamed ceramics by using mine tailings has been proposed in the 2018 National Industrial Solid Waste Resource Comprehensive Utilization Product Catalogue.Thus,in order to solve the resource waste and environmental pollution caused by a large number of abandoned tailings in the mining and utilization of potassium feldspar,this study uses low-grade potassium feldspar tailings to prepare porous thermal insulation ceramic composites,which is beneficial to the comprehensive utilization of mineral resources and the reduction of environmental pollution and production costs.The high-temperature foaming method was used to prepare porous foamed ceramics with potassium feldspar as the main raw material and silicon carbide as the foaming agent.The effects of sintering system,ball milling time,forming pressure and foaming agent content on the properties of porous ceramics were studied in detail.Borax and light calcium carbonate were used as fluxing agent to reduce the sintering temperature of porous ceramics,and ferric oxide was used as foaming stabilizer to adjust the foaming process of porous ceramics.The porous ceramics composites with decoration and thermal insulation was prepared by combining glass-ceramics and porous ceramics.The results indicate that:(1)Using potassium feldspar as the main raw material,and silicon carbide as foaming agent,porous thermal insulation ceramics with good performance can be fabricated by high-temperature foaming method.And the best process conditions are the ball milling time 50 min,the forming pressure 15 MPa,the content of foaming agent 1wt%,and sintering temperature 1250?for 30 min.Under this condition,the ceramic has a bulk density of 0.427 g/cm~3,a water absorption rate of 17.39%,a thermal conductivity of 0.065 W/(m·K),and a compressive strength of 5.375 MPa.(2)Both borax and light calcium carbonate have obvious fluxing effects,which can help reduce the foaming temperature of porous ceramics.However,the porous structure of ceramics prepared with borax is nonuniform,and ferric oxide is needed as the foam stabilizer to improve the foaming process.When 7 wt%borax was used as the fluxing agent,coupled with 1 wt%silicon carbide and 2.5 wt%ferric oxide,after calcined at1150?,the bulk density,water absorption rate,thermal conductivity and compressive strength of the porous ceramic were about 0.541 g/cm~3,12.01%,0.064 W/(m·K),and5.133 MPa,respectively.When using 2 wt%light calcium carbonate as the fluxing agent,without ferric oxide,the porous ceramics show the data of 0.474 g/cm~3,13.32%,0.061W/(m·K),and 4.108 MPa,respectively.(3)Porous thermal insulation ceramic composites with good properties and smooth surface without cracking can be prepared by the process of secondary distribution and one-time sintering.The vickers hardness of the glass-ceramics can reach 7.91 GPa.The compressive strength,bulk density,and the water absorption of the porous thermal insulation ceramic composite were about 4.27 MPa,0.57 g/cm~3,and 9.62%,respectively.