A Research On The Preparation And Modification Of Ceramic Membrane Based On Inorganic Salts

This thesis aims to adopt sol-gel method to get Al₂O₃-ZrO₂ composite membranes by heat treatment through preparing Al₂O₃,ZrO₂ single sols and Al₂O₃-ZrO₂composite sols based on using Aluminium isopropoxide and Zirconium nitrate as raw materials.The results of the characterized analysis which use testing instruments such as thermogravimetric（TG-DTG）,fourier transform infrared（FT-IR）,X-ray diffraction（XRD）,scanning electron microscope（SEM）,nitrogen adsorption-desorption method and Laser particle size distribution（DLS）to analyze thermal stability,crystal phases,surface morphology,specific surface area and pore structures of Al₂O₃-ZrO₂ composite membranes demonstrate that:⑴The optimum parameters of preparing ZrO₂ sol by using Zirconium nitrate as precursor are as follows:0.2 mol/L H₂C₂O₄ is added dropwise to 0.6 mol/L solution of zirconium nitrate on the condition of 20rad/min stirring to make nZr⁴⁺/nH⁺=10;heating to50℃at water bath;besides,4%（volume fraction）polyvinyl alcohol and 35%（volume fraction）glycerol alcohol were added;stirring at reflux for 3 hrs,aging 12 hrs at room temperature,then you can get light blue,transparent and stable ZrO₂ sol.⑵The optimum parameters of preparing Al₂O₃-ZrO₂ composite sols by using Al₂O₃and ZrO₂ single sols are as follows:Al₂O₃/ZrO₂=1,hydrolysis temperature is 30℃,stirring time is 45mins,the additive amount of DMF is 40%（volume fraction）.⑶Heat treatment system of Al₂O₃-ZrO₂ composite membranes are as follows:the gels are dried at a temperature of 50℃,relative humidity of 60%,and heated to 1000℃at a rate of 0.5℃/min in a muffle furnace and insulated for 2 hrs,meanwhile heated slowly at69℃、165℃and 365℃at a rate of 0.25℃/min and insulated for 30mins,finally cooled to room temperature.Then you can get complete Al₂O₃-ZrO₂ composite membranes.So,this system can effectively solve the problem of film cracking.⑷The analysis of TG-DTG、FT-IR、XRD、SEM and BET shows that:Al₂O₃-ZrO₂composite membranes become thermal stable after sintering at 450℃.Al₂O₃-ZrO₂composite membranes are mainly tetragonal zirconia with a little ofAlZrO at the temperature of 1000℃.When the temperature raises to 1200℃,tetragonal zirconia transforms to monoclinic zirconia phase with the generation ofα-Al₂O₃ crystal phase.While there are a large number of monoclinic phase in ZrO₂ membrane at 600℃.It is obvious that alumina plays crystal stability role in the zirconia,and it significantly increases the transition temperature of zirconia.Moreover,aluminum oxide and zirconium oxide are not a simple physical mixing but a real composites.What’s more,Al₂O₃-ZrO₂composite membranes have smooth surface,uniform particle distribution and size,dense structure,small pore size and narrow distribution range and the BJH median pore diameter reaches to 12.403257nm.