Study On Dispersion And Stability Of Low Concentration SiC Slurry And Its Effect On The Properties Of SiC Membrane

In this article,a series of silicon carbide ceramic membranes have been prepared.Silicon carbide powder,dispersant mixed with distilled water and ethanol for preparing silicon carbide slurry.Then,wet film was coated on the silicon carbide support by dipping and spraying.A series of pure silicon carbide ceramic films were prepared at high temperature in argon atmosphere after drying.Firstly,the single factor effects of milling time,pH,dispersant,solid content and particle size distribution on SiC ceramic slurry were discussed.The results showed that the particle size of SiC slurry disperses gradually from 1 hour to 3 hours after ball milling,and the particle size decreased.After 4 hours of ball milling,the particle size started to agglomerates.With the increase of slurry pH value,the absolute Zeta potential of SiC slurry increased first and then decreased,and reached its maximum at pH.=8.At the same time,the slurry viscosity,sedimentation height and transmittance had the same trend.With the increase of TMAH content,the viscosity of slurry decreased first and then increased,and the absolute value of Zeta potential increased first and then decreased.When the content of TMAH is 1.6%,the viscosity was the lowest and the absolute value of Zeta potential was the largest.With the increase of CMC-Na content,the slurry viscosity increased first and then decreased.The slurry sedimentation height and transmittance were the lowest when the addition is 0.4%.The slurry viscosity and sedimentation height increased with the increase of slurry solid content.The slurry viscosity was the lowest when the gradation of SiC particles was changed at m(F1):(F2)=7:3.Furthermore,L9(3~4)orthogonal experiment has been designed to investigate the effects of solid content,TMAH,CMC-Na and pH on slurry and ceramic membrane.The results showed that the viscosity and sedimentation height of slurry were most affected by solid content,and the average pore size of ceramic membrane was most affected by the addition of CMC-Na.Synthetically,taking these factors into account,the optimum slurry formulation was determined as follows:solid content was 6%,pH value was 9,1.6%TMAH and 0.4%CMC-Na.Secondly,the effects of particle size distribution,solid content and sintering temperature on the micro-morphology,phase,pore size distribution and pure water flux of the ceramic membranes were investigated.As the results shown,the crystal phases of sintered samples were 6H-SiC,the optimum scheme was spraying method,and the grain composition was 5:5.When the temperature was 2050?,the surface of the ceramic film was smooth,no obvious defects,the grains of SiC were round,the thickness of the film was about 20?m,the pore size distribution was 0.67 to 1.89?m,the average pore size was1.154?m and the pure water flux was 15 m~3/(m~2·h).Thirdly,the effects of particle size distribution and sintering temperature on the micro-morphology,phase and pore size distribution of the ceramic membranes were studied.The experimental results showed that the crystal phases of sintered samples were6H-SiC,when the grain composition was m(F3):m(F4)=7:3 and the sintering temperature was 1900?,the surface of the ceramic membrane was defectless,the strength of the membrane was high,the thickness of the membrane was about 50?m,the grains were round,the pore size distribution was 0.4~0.7?m,and the average pore size was0.6139?m.