Preparation And Application Of 316L-ZrO₂ Composite Gradient Porous Material

The unique physical properties of ceramic make it have many performance advantages,such as acid and alkali resistance,high temperature resistance,etc.However,its brittleness and low permeability are the urgent problems to be solved in the practical application of high-precision asymmetric ceramic porous membrane materials.Asymmetric metal-ceramic composite porous membrane materials can effectively solve the above problems,so that the advantages of metal membrane and ceramic membrane are complementary to each other,and can meet the needs of special porous membrane materials for special working conditions in process industry.In this paper,the 316L stainless steel porous material was prepared by cold isostatic pressing technology.With the material as the porous matrix,the ZrO₂ gradient porous membrane on the inner surface of the porous matrix was formed and the thickness of the porous membrane was controlled by centrifugal deposition technology.The effects of different gradient layer thickness,powder size and sintering process on the micropore morphology,gas permeability and filtration performance of gradient porous membrane were studied.The pore structure of the composite porous material was analyzed by SEM.It was found that the cross section of the ZrO₂membrane formed under the action of centrifugal force showed a gradient pore size structure,and the average pore size of the membrane was 0.16～0.31μm.The thickness of the membranes obtained were 25μm,40μm and 55μm,respectively,and the results were basically consistent with the experimental design values.The phase analysis of porous membrane by X-ray diffraction showed that the Y₂O₃ doped ZrO₂ membrane had no phase transition after sintering,and the crystalline form of a large amount of cubic phase and a small amount of tetragonal phase coexist stably.It was found that the gas permeability of 316L-ZrO₂ composite gradient porous material decreased gradually with the increase of sintering temperature,the decrease of powder size and the increase of gradient layer thickness.The minimum relative gas permeability coefficient was2.14 m³·m^-2·k Pa^-1·h^-1.The mean pore size of the membrane was mainly related to sintering temperature and powder size,while the thickness of gradient layer had little effect on the pore size.With the increase of sintering temperature and the decrease of powder size,the pore size of the porous membrane decreased gradually,and the minimum pore size can reach 0.16μm.The filtration experiments were designed to verify the filtration effect of 316L-ZrO₂composite gradient porous material in oily wastewater.Under the dead-end filtration method,the suspended matter in oily wastewater can be completely removed by the ZrO₂ membrane with powder size of 1μm,and the filtration efficiency can reach 100%.The removal efficiency of COD was 43.8%higher than that of porous matrix.However,due to the larger pressure difference during the dead end filtration,the interception efficiency of salts and ammonia-nitrogen organic matter become worse,which indicated that the selection of filtration pressure difference parameter was particularly important to realize the efficient interception of such pollutants in industrial wastewater.