Study On The Preparation Of Porous Cordierite From Coal-series Kaolin By Freeze-Drying

In this paper,the porous cordierite was prepared by the coal-series kaolin,silica and magnesia powder,the water as pore forming agent and polyvinyl alcohol as binder,the preparation technique of porous cordierite by freeze-drying is studied.Including the effects of freezing method,freezing temperature and freezing time on the structure and properties of the cordierite,and the solid waste coal-series kaolin is recycled.The main phase of the product is cordierite and Si O2 at 1200? sintering for 3hours.At the same time,a small amount of quartz is found.With the sintering time extended to 5 hours,the reaction of cordierite is aggravated,and the Si O2 diffraction peak is weakened.Therefore,the reaction of cordierite can be promoted by prolonging the sintering time,but the reaction is not thorough.At 1300? sintering for3 hours is all cordierite phase,the prolongation of sintering time and sintering temperature have not obviously enhanced the reaction of cordierite.This indicates that the cordierite can react completely when the material is sintered at 1300? for 3hours.The porous cordierite with layered structure is prepared by directional-freeze casting of liquid nitrogen.The porosity is 79.9-81.8%,the pore size is 10-40?m,the compressive strength is 0.7-3.9MPa,the volume density is 0.38-0.56g/cm3,and the thermal conductivity is 0.153-0.203W/m·K.The porous cordierite with a disordered and poorly connected network structure is prepared by free-freeze-casting of frozen storage room.The porosity is 80.1-85.8%,the volume density is 0.33-0.50g/cm3,and these channels are square,flat and interlaced.When water is used as a solvent,the cordierite structure of porous sphere with a diameter of 10?m-150?m was obtained by spray freezing of liquid nitrogen;When TBA is used as a solvent,the cordierite structure of long strip with a diameter of 50?m-500?m was obtained by spray freezing of liquid nitrogen.The directional porous cordierite was prepared by ultra-low temperature control device.When the solid content is 20wt%,the porosity is kept at 79.9-81.8%,and porosity decreases with freezing temperature decreasing.When the freezing temperature of-30?,porous diameter of 70?m,thickness of hole wall is 30?m,the compressive strength is 1.71 MPa.When the freezing temperature of-150?,porous diameter of 10?m,thickness of hole wall is 20?m,the compressive strength is3.86 MPa.The preparation of porous cordierite ceramics by ultra-low temperature control device,and the pore structure can be regulated by adjusting the freezing temperature of the frozen medium.The cryopreservation technology is used to prolong the freezing time,which can promote the growth of ice crystals.When the freezing time is 60 days,the interlayer spacing is about 10-12?m,the thickness of the wall is about 8-10?m,the ordered arrangement rectangular channels with the long aperture is 30-200?m,and the porosity is 79.3%.The porous cordierite was prepared by composite freezing,the obtained phase is all cordierite phase.At the same time,the gradient pore structure was obtained.the large pores left after the sponges are burned.The moderate pores and small porous left after the ice crystals are sublimated,and the microporous structure left after the binder was burned.The porosity was 78.9%.In this paper,porous cordierite materials were prepared based on freeze drying method,and the factors influencing of freeze-drying were studied.The effects of freezing method,freezing temperature,freezing time and compound freezing on pore structure of porous cordierite were studied.There has not been a systematic study of the factors affecting the freeze drying process,especially there is no report on the preparation of cordierite from coal-series kaolin by freeze-drying...