| Silicon carbide porous ceramic materials have been applied in many fields due to their excellent properties.However,their further development is limited by the harsh selection of raw materials and complex preparation techniques.Isostatic pressing ceramic products have the advantages of large coct density,uniform coct density,large length-diameter ratio and complex shape.The development of porous ceramic forming methods with irregular and complex shapes,such as groove,hollow and back cover,is a research hotspot in the ceramic field.The effects of particle morphology,type and amount of pore-making agent,binder type,particle size and amount of addition,firing and molding process parameters on the properties of porous ceramics were studied,with the help of the isostatic pressing technology to form the candle structure porous sic ceramics.The process parameters of porous ceramics were explored and the manufacturing level was improved.Aggregate particles with different morphology were prepared by different treatment methods,and the effect of particle morphology on sample performance was studied.The silicon carbide particles prepared by airflow grinding have better morphology,i.e.less edges and corners,no obvious sharp particles,approximately spherical,and high concentration.The porous ceramic material prepared by this kind of powder has good air permeability,small resistance,uniform pore diameter and high porosity.The comprehensive performance of the porous ceramics prepared by using lignocellulose as pore-forming agent,was better than that using walnut shell powder.When the amount of lignocellulose was adjusted to 9 wt%,porous ceramic samples with porosity not less than 36% and permeability resistance not more than 150 Pa could be obtained.The study on the influence of the binder formulation system,binder particle size and dosage on the properties of porous Si C ceramics shows that clay is a simple,feasible binder for the preparation method of porous Si C ceramics.At the appropriate sintering temperature,the high temperature binder and aggregate can fully react with each other,the pore passage is smooth,and the intergranular bond is firm.The mechanical properties of porous ceramic specimens are better when the size of D50 is 2 ?m.By coring the properties of the samples with different binder dosage,it was found that the bending strength not less than 20 Mpa and porosity not less than 32% could be obtained when 7 wt% binder dosage was employed.The powder preparation process,forming pressure,holding time and vibration time have important effects on the strength of green body,quality rate and homogeneity of products.With the increase of the pressure,the body changes from powder block to tube and candle,and the strength increases gradually.The strength of the sample increases rapidly with the increase of pressure and reaches the limit,and then gradually becomes stable.The porosity of the sample decreases with the increase of pressure,and the molding pressure has little influence on the pore diameter.The holding time had a great influence on the physical and chemical properties of the body.As the holding time increased,the strength of the body increased rapidly,with the strength approaching its limit after 60 s.The mechanical properties of the samples increased,and the porosity and pore diameter decreased with increasing time.The vibration time had little influence on the bending strength,porosity and pore diameter of the samples.The vibration only increased the weight and size of the samples,which promoted the increase of air permeability resistance.Optimized vibration time of 10 s,pressure holding time of60 s,and forming pressure of 70 MPa were obtained.By coring the performance of the samples under different sintering temperature,it was found that when the sintering temperature was between 1390?1430 ?,the stable performance of the samples could be achieved,with the bending strength not less than 22 MPa,porosity not less than 34%,pore diameter being 66?69 ?m,and the resistance not higher than 150 Pa. |
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