Figure 1: Densified CNT array and performance of the outer-wall membrane.
(a) SEM image of super-grown CNT forest (scale bar, 500 μm). (b) Optical photographs of densified CNT forests that were used as the outer-wall CNT membranes. The Df is the ratio of the CNT area before densification to that after densification. The area (A) is 1 cm2 for all cases, whereas the area occupied by as-grown CNTs (A0) varies depending on the Df value. In the case of a Df of 10, 10 cm2 of as-grown CNTs were densified into 1 cm2 of compressed CNTs. (c–f) Cross-sectional SEM images (× 300,000 magnification, scale bar, 100 nm) of densified CNTs. Greater Df values indicated that the CNTs were more closely packed and more straightened. The figures present the fracture plane images of the CNT array. (g) Water permeability, as affected by the Df for the outer-wall CNT membrane. Data are shown as the mean±s.d., n=3 independent outer-wall membranes tested for the permeability measurement. (h) Rate of rejection by the densified outer-wall CNT membranes obtained with seven types of dextran (5–670 kDa). Dextran solutions with a concentration of 100 mg l−1 were filtered by the densified outer-wall CNT membrane under a pressure of 1 bar at 20 °C.
