Study On Making Porous Ceramics From Rectorite

Porous ceramics were prepared by two methods using rectorite ,a new developed clay with special physical and chemical properties ,one is that pore-forming material was added to raw materials and formed by pressing ,the other is the organic precursor dip forming process . The physical and chemical properties and microstructures of product have been tested by KZL-30 type electric bending strength tester,JVC reading microscope,SX-40 SEM and D/MAX XRD. The results show that apparent porosity is 28.53-49.21%,water adsorption is 15.36-36.26%,bulk density is 1.36-1.86%,bending strength is 12.20-22.3MPa,the coefficient of. thermal expansion is 2.95 X 10-6 at 20-750 ,refractoriness is 1390,gradient pore of sample range from 7 n m to 180 Mm,thermal shock resistance is good. In addition,the results compared with that of porous ceramics made of kaolinite.The conclusions were below through this study:Gradient porous ceramics with continuous pore size used raw material of retorite(or kaolinite),talc and alumina were prepared by compounding different size of grain and pore-forming materials at 1220,product adopted coal powder as pore-forming materials,with increasing pore-forming materials,the apparent porosity was increased too,whereas strength and bulk density were decreased.(2)Polyurethane organic precursors with different pore siize were dipped in slip,then super posited them together and the gradient porous ceramics were made by drying and firing.(3)At the same condition,the bending strength and bulk density of sample made of retotite were better than that of sample of kaolinite.Cordierite in rectorite sample is much than that in kaolinite sample.(5)Thermal expansion coefficient of rectotite sample was lower than that of kaolinite sample,but thermal shock resistance of rectotite sample was better than that of kaolinite sample.Body with made of retotite could be pressed with no additive,had a certain strength. If it wanted a certain strength using material of kaolinite ,it must added 7%-8% additive.When it was pressed by dipping organic precursors ,containing water rate of the sample made of rectorite was 54-60%,proportion of slurry was 1.282-1.360 ,whereas containing water rate of the sample made of kaolinite was 45%,proportion of slurry was 1.495.Homogeneity of pore of sample by dipping was better than that of sample by pressing.A key technology in pression was made particles and mixed materials,but in dipping method,adjusting slip proportion was a important step.