Nodular Structure of the Top Surface

Height Angle Plane Angie Clear Calculator 

It is interesting to note that the PPO-CS2 membrane with the supernodular aggregates exhibited the highest selectivity for the CO2/CH4 gas pair. Filling the interstitial gap between nodular aggregates may, therefore, lead to higher selectivity of the gas separation membrane. 

Asymmetric polyimide membranes with an ultrathin defect-free skin layer were fabricated by the dry-wet process [15]. Composition of casting solution used for the preparation of asymmetric membranes was 12 wt.% polyimide, 55 wt.% methylene chloride, 23 wt.% 1,1,2-trichloroethene, and 10 wt.% butanol. In the dry process (solvent evaporation) the evaporation period was changed from 15 to 600 s, while in the wet process (coagulation process) the coagulation media was methanol. It was possible to control the thickness of the skin layer by controlling the evaporation period. From this AFM study, it was observed that the nodule formation was controlled by evaporation time, while the coagulation media controlled the roughness parameter. 

Membrane Average nodule diameter, scan size 500 nm (nm) Mean roughness, Ra, scan size 1 Xm (run) 

Oh et al. took AFM pictures of TFC nanofiltration membranes, each consisting of a polycimide skin layer formed by in situ polymerization on a polyacrylonitrile (PAN) support layer [29]. PAN support membranes were prepared from casting solutions with different PAN concentrations (10,15, and 20 wt.%) by the phase inversion technique, followed by treatment with a sodium hydroxide solution. The pictares taken for the top surfaces of these membranes are shown in Fig. 4.14. The figme clearly shows that the smface morphology depends on the PAN concentration. 

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