Study On The Effect Of Sintering Aid On The Sintering Character Of Ceramic Microfiltration Membrane Supports

To reduce the penetration resistance,ceramic microfiltration membrane usually has an asymmetric structure,i.e.,the top separation membrane is prepared on the support with a larger pore size.This structure requires the support has the character of high strength,high porosity,large pore diameter and narrow pore size distribution.However,these performances are mutually restricted.For example,to increase the mean pore size,alumina powder with large particle size is chosed to prepare ceramic membrane support.This results in the required higher sintering temperature and the lower contact area.The support has a low bending strength.To solve such problem,adding the sintering aid to alumina powder is usually chosen to controlling the microstructure of ceramic membrane support.The influences of the different kinds of sintering additives on the sintering properties of ?-Al2O3 porous ceramic membrane support were studied.The bending strength,the porosity,the pore size distribution and the anti-alkali resistance were considered.The conclusions can be drawn as follow:(1)Kaolin,talc and the mixture of them(kaolin:talc=3:1,mass ratio)were used as sintering aids.The mixture has the better sintering-aid effect than kaolin or talc because the reaction bwtween kaolin and talc results in the generation of mullite and cordierite.When 10wt%of the mixture was added,the support sintered at 1450? has the bending strength of 104.44 MPa,the porosity of more than 32%,the average pore diameter of 6.23?m,and the alkali corrosion rate of 0.92%.(2)Nano ZrO2 and nano Y2O3 were also used as sintering aid using ZrCl4 and Y(NO)3 as precursor,which is generated by the decomposition reaction.Both nano ZrO2 and nano Y2O3 can distribute evenly on the surface of alumina paticles.The obtained ceramic membrane support had the higher porosity(43 to 44.5%)and the good acid/alkali corrosion(<0.5%).However,the bending strength of the support is poor because the nano ZrO2 or Y2O3 could not wet the alumina particles.The strength of the support body was less than 15MPa,which can not meet the requirement of bending strength of ceramic membrane support.(3)Nano-alumina layer is uesed as sintering aid prepared by solvent-thermal method using aluminum isopropoxide as precursor.Under the co-action of nano-alumina and aluminum oxide(the average particle size was 1?m),the support body sintered at 1650? has the bending strength of up to 20MPa,the porosity of more than 30%,the average pore diameter of 6.5?m,and the alkali corrosion rate of less than 0.2%.It is suitable for the ceramic membrane support applied in high alkali conditions.(4)Nano TiO2 is also used as sintering aid prepared by infiltrating,drying and calcination using TiCl4 as the precursor.When the TiCl4 concentration is 75 g/L,the sintering temperature is 1650?,the holding time is 2h,the pressure pressure 6 MPa,the corn starch is 8wt%,the excellent performances of the ceramic membrane support body is prepared,of which bending strength is more than 55 MPa,porosity is more than 38%,the mean pore diameter is 8?m,the pore size distribution is very narrow and the alkali corrosion rate is less than 0.25%.