Preparation Of Doped Al₂O₃interlayers On Porous Stainless Steel Support

Membrane separation is one of the most promising high-tech and has been widely used infood industry, water treatment, petrochemical and other fields. Porous metal-ceramiccomposite membrane is one of the most outstanding membrane materials. But their interfacebonding property is poor because of their different natrue performance. Metal elements, suchas Ag, Ni and Cu can be used to modify the interface of the two materials, thereby enhancingthe binding of Al₂O₃ceramic interface with stainless steel substrate. This study focuses on thesol-gel preparation of doped Al₂O₃sol with the dopants Ag, Ni and Cu in the form of AgNO₃solution, NiO sol and Cu （NO₃）2solutions, respectively. Then the316L porous stainless steelsubstrate was dip-coating and heated to obtain doped Al₂O₃interlayers. The impact of thedoping amounts of metal elements in the casting solution, heat conditions of dried gel films,sintering atmospheres and membrane moprhologies were deeply explored and the optimalpreparation of the doped Al₂O₃interlayers on porous stainless steel support has been obtained.The main results were listed as follows:1. Continuity and smooth doped Al₂O₃interlayers were obtained. The different metalelement ratio in the casting solution obtained different morphologies. The optimal dopingamount of Ag, Ni, Cu was0.5,8and3%（mol/mol）, repectively.2. The interlayer sintered in air composed of round or square particles and the interlayersintered in air-nitrogen composed of columnar particles. The sintering atmosphere in thisstudy is chosen as air-nitrogen two-step method.3. The atmosphere changing temperature affected the membrane morphology. Themembrane had pinhole defects and particle agglomeration at400°C and the particles meltedand bonded at600°C. When the temperature was550°C, the three kinds of doped Al₂O₃interlayers had the optimal morphology with a complete continuous membrane and clearangular particles. The optimal temperature of change atmosphere in this study was550°C.4. The highest heat temperature affected the differences of membrane morphologies. Themembrane had poor continuity, porosity defects, and particle agglomeration at650°C and notyet formed particles at750°C. The three kinds of doped Al₂O₃interlayers had the optimalmorphology with the particles growth completely at850°C. The optimal highest heattemperature was decided at850°C. 5. The three kinds of doped Al₂O₃interlayers on porous stainless steel support wereprepared under the condition of the optimal doping amount, sintering atmosphere, thetemperature of change atmosphere and the highest heat treatment temperature. Then heatingto the interlayers in hydrogen atmosphere was executed at800℃in order to promote thebonding performanece between the interlayer and porous stainless steel substrates. Themembrane is mainly composed of columnar particle with a length of about5μm.