Intermediate gel coating on macroporous Al_2O_3 substrate for fabrication of thin carbon membranes

摘要

To fabricate carbon membranes based on a low-cost macroporous Al_2O_3 substrate, a pretreatment called "intermediate gel coating" on the substrate was introduced. It can be carried out simply by coating the substrate with an AlOOH sol and drying to form a gel layer. The PFA (polyfurfuryl alcohol) was synthesized and coated on the gel-modified Al_2O_3 substrate, and the carbon membranes were obtained after a carbonization treatment. Scanning electron microscopy (SEM), thermogravimetry (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and pore-size analysis were conducted in material characterization, and the permeation performances of the carbon membranes were tested with H_2, N_2,O_2 and CO_2. Upon the substrate surface modification for fabrication of carbon membranes, such an intermediate gel coating method is superior to the traditional sol-gel treatment because the intermediate gel layer effectively prevented the PFA from penetrating into the macroporous substrate during coating and carbonization treatments so that a thin and uniform carbon layer can be created. The resulting carbon membranes exhibited promising gas permeability and permselectivity.