Supernodular aggregates

Supernodular aggregates—aggregates of nodular aggregates, from 1000 to 20 000 A (2 j,m) in diameter. 

As shown in Table 4.1, the mean diameter of the supernodular aggregates is 1.20 j,m. Figure 4.9 shows the AFM image of the top surface at a scan size of 1 pm. From Fig. 4.9, it seems that a supernodular aggregate contains smaller units that correspond to nodular aggregates, the mean diameter of which is 43.7 nm. Figure 4.10... 

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. 

Samples Nodules (nm) Nodule aggregates (nm) Supernodular aggregates (nm)... 

The diameter of the nodules appears to be 20 and 16 nm for S and M membranes, respectively. For the H membrane, supernodular aggregates of 620 nm contained 6-8 nodule aggregates of 140 nm (Fig. 4.27). In addition to their small diameter (12 nm), the Si02 nodules are more discernable than those of M and S membranes. 

Khulbe and Matsuura characterized the dense PPO membrane etched by oxygen plasma [54] and studied the structural changes in the depth direction by AFM. Carbon disulfide was used as a solvent when the dense membrane was prepared. It should be recalled that unhke other solvents, carbon disulfide produced a dense PPO membrane, and supernodular aggregates could be observed on its surface. 

Fig. 4.31. Arrangement and size of supernodular aggregates and nodular aggregates in dense PPO-C 2 membrane. Reprinted from [54]. Copyright 2000, with kind permission from Elsevier...

Table 4.7. Mean width and length of the gap between supernodular aggregates after various etching times, at 5-gm scan range (A), and at l-gm scan range (B) in the PPO-CS2 membrane ...

Fig. 8.5. Mean distance between supernodular aggregates at 5- xm scan range (4) and between nodular aggregates at 1- xm scan range B) in the PPO-CS2 membrane after various plasma etching times...

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