Research On Preparation And Foaming Mechanism Of Foamed Architectural Ceramic Materials By Alumnium Ash

Aluminum ash is a solid waste produced in the process of preparation,processing and use of metal aluminium.At present,there are still some problems in the utilization of aluminium ash resources at home and abroad,such as low utilization rate,complex process,secondary pollution and so on.In this paper,aluminium ash is used as blowing agent to prepare foamed architectural ceramics.It not only expands the raw material source of foamed ceramics,but also puts forward a new method for the resource utilization of aluminum ash.In this paper,the composition and thermal properties of aluminum ash were analyzed by XRD,XRF and TG-DTA.The results show that the main phase composition of aluminum ash is Al2O3,SiO2,NaCl,AlN and MgAl2O4.AlN will oxidize at high temperature and release gas.It is theoretically feasible to use aluminum ash as blowing agent.Using aluminium ash,potash feldspar,quartz and kaolin as raw materials,the basic formula of aluminium ash foamed architectural ceramics was designed.The effects of alumina ash on the structure and properties of foamed architectural ceramics were investigated through single factor experiments.The results show that the content of aluminium ash increases from 5%to 45%,the volume density decreases from 1.5g/cm~3to 0.75g/cm~3,the compressive strength decreases from 45.1MPa to 8.8MPa,the water absorption increases from 1.2%to 4.1%,the pores were irregular and the average pore size increased;when the content of aluminium ash exceeds 45%,the volume density increases,the pores were irregular and the average pore size decreased.Secondly,the flux material in the formula is adjusted.In order to explore the influence of different fluxes on the structure and performance of aluminium ash foamed architectural ceramics,some potassium feldspar was replaced by glass powder,albite and talc.The results show that replacing part of potassium feldspar with glass powder increases from 0%to 24%,water absorption increases from 3.5%to 4.4%,bulk density decreases from 0.85g/cm~3 to0.31g/cm~3,and compressive strength decreases from 15.2MPa to 1.5MPa,The pore were irregular and the aperture is quite different.When potassium feldspar is replaced by albite,the independent spherical pore appears in the structure,and the uniformity of the structure is improved.When the replacement amount increases from 0%to 30%,the water absorption decreases from 3.5%to 1.5%,the bulk density decreases from0.85g/cm~3 to 0.58g/cm~3,and the compressive strength decreases from 15.2MPa to5.5MPa.Independent spherical pores appeared in the sample and the pore structure was improved.The replacement amount increases from 0%to 15%,the water absorption decreases from 1.5%to 0.9%,the bulk density decreases from 0.58g/cm~3 to 0.38g/cm~3,and the compressive strength decreases from 5.5MPa to 3.7MPa.Most of the pores in the samples are spherical,and the pore structure has been improved obviously.Finally,iron oxide was introduced into the formula,the amount of iron oxide increased from 0%to4%,the bulk density decreased from 0.38g/cm~3 to 0.22g/cm~3,the compressive strength decreased from 3.7MPa to 2.2MPa,the average pore size decreases,and the spherical pore gradually changes to irregular shape.Aluminum ash foamed architectural ceramics which meet the requirements of JG/T511-2017"Foamed Ceramic Thermal Insulation Board in Buildings"were prepared.The properties were as follows:porosity 88%,water absorption 0.8%,bulk density0.28g/cm~3,compressive strength 2.5MPa,thermal conductivity 0.09W/m·K.The formula is:aluminium ash 25.00%,albite 18.75%,potassium feldspar 6.25%,quartz 25.00%,kaolin10.00%,talc 15.00%,iron oxide 1.00%.The results of thermal analysis of the optimum formulation show that the main temperature range of bubble formation and growth in green body is 1100~1200?.The effects of sintering temperature,heating rate and holding time on the structure and properties of aluminium ash foamed architectural ceramics were investigated.The optimum sintering system was obtained.The sintering temperature was 1200?,the heating rate of room temperature to 1100?was 10?/min,the heating rate of 1100~1200?was 3?/min,and the holding time was 20min.Based on the comprehensive analysis of the composition of aluminum ash and the preparation process of architectural foaming ceramics,the foaming mechanism of aluminum ash was revealed.In this paper,it is considered that the high temperature gas source,liquid content and liquid properties of the green body have great influence on the structure and properties of foamed ceramics.Aluminum nitride in aluminium ash has obvious oxidation behavior at 550?~950?,and nitrogen is released.This oxidation process can be sustained to more than 1100? in ceramic body.