Research On Preparation Of Porous Alumina Ceramic By Electrophoretic Deposition And Deposition Mechanism

Porous alumina ceramic is one of the porous ceramic materials which have excellent heat resistance,wear-resistance,corrosion resistance,good biocompatibility and permselectivity.Its combination of good mechanical properties,good physical and chemical property leads to wide range of application,such as environment purification,filter of molten metal,bioengineered material etc.At present,mixing method,template impregnation method,sol-gel method and freeze-drying method have beenused to prepare porous alumina ceramic.Electrophoretic deposition(EPD)is a new technique ofpreparing ceramiccoating and body.Main advantages which areusedin ceramic processing arethe applicability of this method topowders with particlesizesinthesubmicronor nanometerrangeand the dense,homogeneousparticle packingwhich couldbe obtained by EPD from well-dispersed,stable suspensions.Whenaqueous-suspensions are used in EPD,gas bubbles areformed by electrolysis above the decomposition voltage ofwater,which result in the porous structure of ceramic.In this work,water-based EPD to prepare porous alumina and the formation mechanism of pores were studied.The results were as follows:1.The influences of the deposition conditions on porous alumina prepared by EPD were studied.With the increase of temperature,dielectric constant and viscosity of water solvent decreased,and the ionization constant increased,leading to effects on the deposition rate and water electrolysis,and thus affected the deposition.When the temperature was 15?,porous alumina ceramics with the most regularly arranged pores would be formed;The size of the grid used as cathode electrode would influence distribution of electrical field intensity of electrode under the applied electric field,thus influenced the deposition.As the grid size increased,the average pore diameter of porous alumina ceramics increased gradually.The grid size which was too large or too small was unfavorable to improve the regularity of pore arrangement;With the extension of deposition time,the deposition thickness increased gradually,distribution of electrical field intensity on the electrode changed.The average pore diameter increased as the deposition time prolonged;Deposition voltage change would affectthe electric field distribution on the electrode and thus affect deposition.Under the applied voltage of 10V,porous alumina ceramic with regularly arrayed pores could be produced.When the deposition voltage was greater than 15V,the arrangement of the pores in porous alumina was less regular.2.The effects of acid on porous alumina prepared by EPD were studied.The amount of acid would influence the deposition result.Too high levels of acid was unfavorable to form the regularly arranged pores neither did too low levels of acid.There was a proper range of acid content for regular arranged pores formation,and the range was different among different acid;Relations between the Zeta potential and the pH value of the suspension would affect preparation of porous alumina ceramic by EPD.In different range,porous alumina ceramic with different characteristics would be formed.