Fabrication Of Flexible Silica Nanofibers And Their Applications In Separation

With the accelerating process of industrialization in our country, the air pollution is paid much more attention by the nation. The high temperature smoke (600-1000℃) produced by the industries of metallurgy, power generation, steel, etc. has caused the PM2.5(particulate matter with an aerodynamic diameter of less than2.5μm) pollution which could lead to the asthma, bronchitis, cardiovascular disease and so on. It has caused serious damage to people’s health and ecological environment, thus, it’s of great significance to develop filter materials for high temperature smoke.The conventional filter materials made of organic polymer materials can only fit for the smoke with temperature around300℃, the high temperature smoke needs to be cooled down before filtration, which will cause energy waste. Meanwhile, the heat-resisting inorganic ceramic fiber filters we have now usually get the diameters of micron scale, can’t intercept the PM2.5effectively. The inorganic oxide nanofibers with good chemical, thermal stability and diameters of nanoscale can be used for nanoparticles filtration, which show great potential in high temperature filtrations. As we know, electrospinning is an effective method to produce continuous nanofibers, which also can produce inorganic nanofibers. But the electrospun inorganic nanofibers almost have the problem of brittleness, which has limited the range of their applications.In this paper, we utilized aretetraethyl orthosilicate as silicon source, polyvinyl alcohol as polymer carrier during the fabrication, combined with sol-gel method and calcination technique, we successfully fabricated flexible silica nanofibers with good mechanical strength and thermal stability. The morphology, flexibility, and tensile strength of the the silica nanometer fiber (SNF) membranes were investigated by tuning the precursor fiber composition and calcination temperature. Moreover, the filtration performance of the SNF membranes with various fiber diameters and basis weights for300-500nm sodium chloride aerosols was also studied. The membrane with excellent performance could be applied as a promising filtration media for high temperature dust which comes from industrial processes.In addition, in case of further improving the performance of SNF membranes and explore the other potential applications, we used fluorinated polyurethane (FPU) to decorate the SNF membranes. The SNF/FPU membranes were fabricated by dip-coating the SNF membranes in the DMF solutions with various FPU concentrations for a certain amount of time at room temperature. Then the as-prepared membranes were dried in an oven. Then, we tested various performance of the membranes. The test results showed that tensile strength of composite membranes increased obviously compared with the original SNF membranes. Further more, the SNF/FPU membranes exhibited robust waterproof and breathable performance. The SNF1/FPU1membranes with both low surface energy and fine roughness structure showed the highest WCA of147°and OCA of125°. Significantly, the SNF4/FPU1membranes with the large fiber diameter and low FPU concentration exhibited excellent hydrostatic pressure (13.5kPa), good air permeability (54.04mm/s), and relatively high tensile strength (15.2MPa). Thus, the SNF/FPU membranes exhibited nice functions of gas-liquid separation, suggesting a promising candidate for protective clothing, bioseparation, water purification, tissue engineering, etc.