Effect Of Addition And Conversion Of Silicon Nitride On Film Formation And Pore Size Of Silicon Carbide

In this article,a series of silicon carbide ceramic membranes had been prepared.Silicon carbide powder,silicon nitride powder,dispersant and other raw materials mixed with distilled water for preparing silicon carbide slurry.Then,wet film was coated on the silicon carbide support by dipping method.A series of pure silicon carbide ceramic films were prepared at high temperature in argon atmosphere after drying.The viscosity,Zeta potential,particle size distribution,settling ability and the surface condition of slurry were mainly studied.On this basis,the appropriate slurry formulation,reaction temperature and addition amount of silicon nitride were determined.The mechanism of transformation of silicon nitride was also researched.Firstly,the effects of the solid content,the type and content of dispersant,the addition amount of Si₃N₄ on the properties of the slurry and the surface condition of the membrane were discussed.The results show that:slurry had great performance when the solid content was 20%,pH was 9,add 0.6%TMAH.The slurry prepared by the best formula whose Zeta potential was 46.7 mv,viscosity was 2.10 mPa S and the size distribution was from 200 to800 nm,the average particle size was 500 nm,and it can keep the 48h.At the same time,the slurry can form wet film with a smooth surface and the film thickness was about 50?m.The addition amount of Si₃N₄ had little effect on the performance of silicon carbide slurry.Secondly,the effect of sintering temperature and the addition amount of silicon nitride on the film formation and pore size of silicon carbide membrane was investigated in the case of suitable slurry formulation.As the results shown,the crystal phases of samples were 6H-SiC.When the reaction temperature increased from 1900?to 2200?,the strength of film was first rise and then fall,the size particles of film was gradually increased and the flocs in the film decreased,the average pore size and pure water flux increased.At 2000?,there was no flocs in the film,the strength is high,and the particle was small.The average pore size was 1.1 m,the pore size distribution is 0.8 to 1.5?m,and the pure water flux is 35.78 m³/?m² h?.Finally,the effect of silicon nitride addition on the formation and properties of silicon carbide film at 2000?was studied.The results show that all of the sintered samples crystal phases were 6H-SiC.Si₃N₄ content increased from 2%to 10%,the sample size and the pure water flux decreased gradually,in addition 8%sample had great surface morphology,the average pore size is 1?m,pore size distribution from 0.8 to 1.2?m,the pure water flux was 33.23m³/?m² h?.