摘要
以煤矸石为主要原料,硅藻土粉、滑石粉及发泡剂SiC为辅料制备出高强度泡沫陶瓷,研究了煤矸石掺入量(质量分数)、SiC添加量(质量分数)和混合原料粒度对制备的泡沫陶瓷性能的影响。当煤矸石掺入量增加时,混合原料的硅铝质量比逐渐减小,样品抗压强度先增大后减小,煤矸石掺入量为70%(质量分数)时,制备出的样品具有均匀的孔结构;增加SiC加入量使得烧结过程中发泡产生的气体增多,样品抗压强度及表观密度随气孔率的增大而减小,SiC加入量为0.6%时,制备的泡沫陶瓷的性能最佳;样品平均孔径和开孔率随着混合原料的粒度的减小而降低,此时较小的孔径和均匀孔结构提高了泡沫陶瓷抗压强度,混合原料体积平均粒径为5.4μm时,总气孔率为80.6%,此时抗压强度达到6.1 MPa。本工作中煤矸石利用率高,制备的高气孔率高强度泡沫陶瓷为煤基固废的综合利用提供了借鉴与指导。
Introduction Ceramic foams is a kind of inorganic non-metallic material with a three-dimensional porous network structure after calcination at high temperatures.The mechanical properties are one of the important factor to evaluate the application of ceramic foams,which affected by the porosity,pore size,pore distribution and skeleton structure,etc.High porosity would reduce the bearing capacity of ceramic foams and limit its application fields.Therefore,this research is mainly focused on how to balance porosity and strength of ceramic foams,as compressive strength could be improved effectively by reducing the pore size,narrowing the pore size distribution or forming a closed pore structure.When coal gangue is used as raw materials to prepare ceramic foams,it still exists some problems,such as the low utilization,high energy consumption and unclear foaming principle.The key to producing a ceramic foam is to form a melt matrix with appropriate viScosity and to generate a certain amount of foaming gas in the matrix.Due to the complex composition of coal gangue,it is difficult to control the viScosity of the melt matrix at high temperatures,resulting in the pore structure distribution uneven and reducing the mechanical properties of ceramic foams.In this work,coal gangue was used as the main raw materials,and diatomite powder,talc powder,a small amount of silicon carbide(SiC)foaming agent were added to prepare the ceramic foams with high compressive strength.The effects of raw materials composition,SiC content(mass fraction)and particle size of feed mixture on the pore structure,apparent density and compressive strength and other properties of ceramic foams were investigated.Methods The coal gangue was crushed and sieved to less than 74μm.Based on the SiO_(2)-Al_(2)O_(3)-MgO ternary system,the coal gangue,diatomite powder and talc powder were mixed at different mass ratios,and then SiC powders were added as the foaming agent,the mixture and agate balls in a mass ratio of 1:1 were milled with a speed of 300 r/min.After ball milling,the powders were placed in a corundum boat and heated at 1190℃for 25 min,then cooled to room temperature in furnace.The chemical compositions of the raw materials were determined by X-ray fluoreScence spectrometer(XRF).The crystalline structure of raw materials and ceramic foams was determined by X-ray diffraction(XRD).The thermogravimetric analyzer(TG-DSc)was used to analyze the mass change and thermal analysis of raw materials.The particle size of mixed materials was analyzed via a laser particle size analyzer.The compressive strength of ceramic foams was measured via a pressure test machine.The pore size distribution of the sample was measured by Nano Measurer 1.2,and the water absorption and porosity of ceramic foams were measured by Archimedean method.Results and diScussion When amount of coal gangue reached 60%and 70%,the main phases of ceramic foams were cordierite and quartz,and when content of coal gangue exceeded 75%,sekaninaite phase appeared.When content of coal gangue reached 85%,the average pore size of the ceramic foams decreased from 2.01 mm to 0.80 mm,and the distribution of pore size became uneven as the increase of coal gangue could reduce the SiO_(2)/Al_(2)O_(3)mass ratio,which would lead to an increase of melting temperature of the matrix,and thus the generated silicate molten material at high temperature decreased and the viScosity increased.As a result,the pore structure with uneven distribution would decrease the bearing capacity.Compressive strength reached the maximum value of 2.2 MPa at the coal gangue content of 75%.When content of SiC foaming agent increased,more small pores were generated in the matrix,these pores could connect to form large pores during sintered process,resulting in a gradual increase in pore size.When content of SiC increased from 0.4%to 1.4%,the compressive strength of ceramic foams decreased from 2.9 MPa to 0.8 MPa,the reduction of particle size of the feed materials could be benefit to the agglomeration and sintering behavior of SiO_(2)at low temperature.When the average particle size decreased from 21.1μm to 5.4μm,the apparent density and porosity of ceramic foams changed slightly,while the compressive strength gradually increased from 2.6 MPa to 6.1 MPa,being due that the small particle size of SiO_(2)in feed mixtures could improve the densification of the pore wall and finally improve the bearing capacity of the ceramic foams.Conclusion The main conclusions of this work can be summarized as follows:With the increase of coal gangue content in the feed materials,SiO_(2)/Al_(2)O_(3)mass ratio decreased from 2.66 to 2.05,the pore structure of the sample deteriorated,and the compressive strength first increased and then decreased.When the content of SiC increased,more gases were released during calcination process,and thus increasing the porosity.When it exceeded 0.8%,the excess SiC should increase the open porosity and thus reduces the compressive strength of ceramic foams.Reducing the particle size of the feed mixture could improve the reaction activity of powders during the high temperature foaming process,the small pores and uniform pore structure could obviously improve the compressive strength of ceramic foams.When mass ratio of coal gangue:diatomaceous earth powder:talc was 7:2:1,content of SiC was 0.6%,the average particle size of the mixed materials was 5.4μm,the apparent density,porosity and compressive strength of the prepared samples were 0.45 g/cm3,80.6%,and 6.1 MPa,respectively,expected to be applied in the field of heat preservation wall.
作者
孟凡会
戴露霏
姚隆帆
汪洋洋
李忠
MENG Fanhui;DAI Lufei;YAO Longfan;WANG Yangyang;LI Zhong(State Key Laboratory of Clean and Efficient Coal Utilization,Tai yuan University of Technology,Taiyuan 030024,China)
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
2024年第9期2959-2968,共10页
Journal of The Chinese Ceramic Society
基金
山西省重点研发计划项目(202102090301026)。
关键词
泡沫陶瓷
煤矸石
抗压强度
孔结构
碳化硅发泡剂
颗粒粒径
ceramic foams
coal gangue
compressive strength
pore structure
silicon carbide foaming agent
particle size
