Preparation Technology Of Iron Tailings Porous Ceramics By Foam Gelcasting And Carbothermal Reduction

Iron tailings,which produced in the beneficiation process,is a kind of industrial wastes.The stockpiling of huge amount of iron tailings is seriously affecting the environment nearby as well as the development of mining industry itself.In this thesis,iron tailings porous ceramics with high thermal conductivity are prepared by foam gelcasting and carbothermal reduction reaction technology using iron tailings and graphite powders as raw materials.The porous ceramics can be used as carriers of the composite phase change materials in the green energy-saving areas such as solar hot water floor heating system.The iron tailings that endangers the environment will be reused for energy conservation and environmental protection.Therefore,this study has significant economic and social benefits.Firstly,fine particle iron tailings and certain amount of graphite powders were used as raw materials.Iron tailings ceramics were prepared by cold moulding and then sintering in a nitrogen atmosphere.The phase composition of the products was determined by X-ray diffraction analysis.The effects of graphite content,sintering temperature and holding time on the product were studied,and the raw material ratio and sintering technology parameters were determined.Secondly,iron tailings porous ceramics was prepared by foam gelcasting and carbothermal reduction reaction technology,and the effects of material formulation and solid content of slurry on porous ceramics were studied.Finally,the thermal conductivity of iron tailings porous ceramic was calculated and measured.The results show that the sintering temperature is an essential factor to affect the reaction of iron tailings with graphite to produce SiC.The initial temperature of the reaction is about 1500 ?.With an increase of sintering temperature,the content of SiO2 decreases while SiC increases.The content of SiC reaches the maximum at 1600? whiclh can be regarded as the ideal sintering temperature in this project.Longer holding time is beneficial to entirely reaction.With the graphite content of 25 wt.%and the sintering temperature of 1600?,the SiC content in the product reaches the highest value with two hours the holding time,which could be regarded as the ideal holding time.When the graphite content increases,the content of SiC in the porous ceramics increases first and then decreases.When the porous ceramic sintered at 1600 °C for two hours,the relative content of SiC reaches the maximum of 87 wt.%with 25 wt.%graphite.When the content of graphite exceeds 30 wt.%,the relative content of SiC decreases with an increase of graphite content.Adding small amount of SiC powders in the raw materials can prevent deformation of the porous ceramics during sintering process and improve its thermal conductivity.The optimum SiC content in the experiment is 15 wt%.With an increase in solid content of slurry,the skeleton of porous ceramics becomes thicker,and the linear shrinkage,volume density and compressive strength increase,while the porosity and water absorption rate decrease at the same time.Balancing all kinds of properties,the porous ceramics with the best performance was obtained,when the solid content of the slurry is 45 wt.%.Thermal conductivity of the porous ceramics prepared by foam gelcasting and carbothermal reduction reaction technology can up to 0.69 W/(m·K),which is 20 times higher than that of ordinary iron tailings porous ceramics with the same porosity.