| Iron tailings are solid mineral wastes with low metal content after grinding,screening,gradual gravity separation and ore precipitation.A large amount of iron tailings not only waste resources,but also cause serious ecological damage to soil and surface water.The effective processing and utilization of iron tailings is an effective way to improve energy conservation,environmental protection and economic benefits.In order to explore the secondary utilization of iron tailings,Si C powder was synthesized by carbothermal reduction using iron tailings as silicon source and anthracite as carbon source.Then silicon carbide ceramic materials are prepared on the basis of synthesizing silicon carbide powder.Finally,iron tailings porous ceramics with excellent properties were prepared by gel casting with triethanolamine dodecyl sulfate as blowing agent and xanthan gum as curing agent.The main conclusions are as follows:（1）Si C composite powders were synthesized from Anshan iron tailings by carbon thermal reduction.The main crystalline phase of the product isβ-Si C and the secondary crystal is Fe-Si compound.The optimum technological parameters are:the molar ratio of Si O2/C is 5,the sintering temperature is 1500℃.The grain size of Si C produced by carbothermal reduction is distributed in irregular lamellar and columnar forms and the grain surface is smooth.The formation process of Si C powder consists of three parts:first,chemical reaction occurs between Fe2O3,Si O2and C to form ferrosilicon compound,which melts when heating temperature reaches 1410℃to provide liquid environment for subsequent reaction;then Si O2is reduced by C to Si O;finally,Si O2reacts with surrounding C to form Si C（2）Si C ceramics were prepared by carbothermal reduction of iron tailings and anthracite.With the increase of sintering temperature and carbon content,the bulk density,apparent porosity and compressive strength decreased.At the sintering temperature of 1500℃,the molar ratio of Si O2/C is 6.The bulk density is 1.29 g/cm3,the apparent porosity is 59.3%and the compressive strength is 35 MPa.Si C ceramic surface has different shapes of pores,pores are produced by the carbothermal reduction of gas,free discharge form pores.The more complete the carbothermal reduction reaction,the more pores formed.（3）The viscosity of slurry increases with the increase of solid content,the viscosity of slurry over 50%will increase by more than 1 Pa·s,the best solid content is 50%.With the increase of the content of foaming agent in slurry,the porosity and pore size increase.With the increase of sintering temperature,the apparent porosity decreases,the uniformity of pore structure increases and the pore diameter decreases gradually.When the content of foaming agent is 0.2%and the sintering temperature is 1150℃,the pore size distribution is the highest.The apparent porosity was 62.42%,the bulk density was 0.839 g/cm3,and the compressive strength was 8.11 MPa. |
