Synthesis And Gas Permeation Properties Of Porous Ceramic Supported Carbon Nanotubes Membrane

Carbon nanotubes (CNTs) have wide application foreground because of their unique structure, extraordinary mechanical property, electrical ability, especial calorifics, remarkable magnetism and hydrogen storage capbility, which has dramatically stimulated intensive research since their discovery in 1991.There are many applications for 1D nano-pore structure of CNTs, which has not been completely exploited. Sholl and coworkers found that the transport rates in nanotubes were magnitude of orders faster than in zeolites with comparable pore size calculated by atomic simulation method. Thus, if CNTs are made into membrane, we predict that carbon nanotubes membrane will have fluxes that are orders of magnitude greater than crystalline zeolite membranes. Moreover, diameter size of CNTs can be adjusted for preparing membrane suitable for the separation of different complex materials.Martin had successfully synthesized gold nanotubes membrane, which could completely separate pyridine and quinine. The pyridine could permeate through the membrane because of its smaller moleculars size, while quinine couldn't. The membrane exhibited good separation selectiviy for pyridine and quinine. Thus we could expect that carbon nanotubes membrane will have broader applications, such as protein separation, nanoreactor and sensors. This will make CNTs become important inorganic membrane material, and explore CNTs new application area, and make CNTs possible for practical utilization. Also, this will enlarge the field of inorganic membrane preparation technique at the same time.For the first time, we synthesized vertically aligned carbon nanotubes on porous ceramic support, and successfully used carbon naotubes arrays to prepare supported carbon nanotubes membrane. Some gases permeability and separation ablity through the CNTs membrane were first reported in this study.We selected and prepared a suitable porous support, and then prepared vertically aligned CNTs on it. Gaps between CNTs were sealed by polymer; caps of CNTs and catalyst particles wrapped by CNTs were removed. Thusan ideal supported carbon nanotubes membrane (SCNTM) was successfully synthesized suitable for separation of gases.Experiment results show that Al₂O₃ particles are pressed into disk and then sintered at high temperature. The formed porous substrate has strong mechanical strength and gas permeation flux. It is good substrate for supported CNTs membrane because of its enduring steady property at severe acid, alkaline and high temperature conditions.Vertically aligned CNTs could grow on the substrate by improved floating catalyst method at specific reaction condition. This article discussed the effect of carrier gases and temperature on CNTs production. It was found that bamboo-like CNTs contained N element with low graphite degree formed in NH₃, where tubular-structure CNTs with high graphite degree in N2. CNTs diameter increased with the reaction temperature. Vertically aligned CNTs growth mechanism and formation reason of different type CNTs are given out. Density-controlling mechanism is confirmed for the growth of vertically aligned CNTs on porous ceramic support by improved floating catalyst method.Polystyrene could well seal the gaps among CNTs and enhance the combination intensity between tubes or CNTs and substrate. It is effective way to remove catalyst particles contained in CNTs and open CNTs by acid etch and mechanical method.This article also investigated gas permeability through the 1-dimension nano-pores of the prepared supported CNTs membrane. Experiment results show that the SCNTM has good gas ideal separation selectivity and fluxes. The selectivity increases with the decreasing of CNTs diameter and increasing of the time treated by acid.SCNTM has good separation selectivity and fluxes, suitable for practical application, which enlarges the application field of CNTs.