Morphology and N2 Permeability of Multi-Wall Carbon Nanotube—Teflon Membranes
Abstract:We prepared buckypapers with surface densities in the 1.13–5.66 mg · cm−2 range by filtering multi-wall carbon nanotube (MWCNT) suspensions in acetyl-acetone (acac) and dimethylformamide (DMF) through 0.45 m nylon filters. Filtration curves were evaluated using the Carman equation. The average resistance of the filter itself was found to be Rm = 3.79 · 1010 m−1 for acac and 8.49 · 1010 m−1 for DMF. The specific resistance of the filter cakes decreased with increasing film surface density from 16.1 · 1012 m · kg−1 (for the 1.13 mg · cm−2 film from DMF) to 4.38 · 1012 m · kg−1 (for the 5.66 mg · cm−2 film from DMF). The effective diffusivity of N2 at 298 K and a pressure difference of 10 mbar was also determined for all membranes and found to fall into the 1.14 · 10−9–3.74 · 10−9 m2 · s−1 range. Both the porosity and the tortuosity of buckypapers increased with their thickness. An approx. 5 m thick Teflon (PTFE) coating was applied to the MWCNT membranes by pulsed laser deposition. The gas permeability of the MWCNT–PTFE membranes matches that of the uncoated nanotube films. This observation is an agreement with our SEM and AFM data on porous coating morphology.
Document Type: Research Article
Publication date: April 1, 2007
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