Atomic Force Microscopy (AFM)

The surface morphology of the pure Phenoxy membrane and the Ph-modified nanocomposite membranes were analyzed by Tapping Mode – Atomic Force Microscopy (TM-AFM). Quantitatively, the differences in the morphology can be expressed in terms of various roughness parameters such as the mean roughness Ra, the root mean square (rms) of vertical data Rq, and the maximum height Rmax. Here, the mean roughness is the mean value of surface relative to the center plane, the plane for which the volume enclosed by the image above and below this plane are equal; Rmax the height difference between the highest and lowest points on the surface relative to the mean plane and Rq is the standard deviation of the Z values within the given area. The roughness parameters were calculated for pure Ph and Ph nanocomposite membrane surfaces with critical loading of filler and have been summarized in tabular format. The TM-AFM images of the Pure Phe membrane is depicted in Fig. 29. The AFM images of Phe membrane showed randomly distributed hard crystalline regions (crystallites) of 50 – 200 nm in dimension on the membrane surface as evident from the observed morphology. The pure Phe membrane surface has a mean roughness of 3.297 nm.

The nanocomposite membrane with critical loading percentage of 3 wt. % ORM (i. e., PNC3) content (Fig. 29) showed a homogeneous and non-porous morphology. The mean roughness for the surface topography of the membrane was found to be 4.045 nm.

Atomic Force Microscopy (AFM)

Fig. 29. Tapping mode (3D) AFM images of (a) Phe (b) PRC3 (c) PRC2

This shows that there is a good compatibility between the filler (ORM) and the Ph matrix. This is in consistent with the results of SEM studies. While critical loading surface topography of PRC3 showed some non-uniform regions with non-porous morphology. The mean roughness of PRC3 was observed to be 4.562 nm as shown in table 16. This showed that the phosphomolybdic acid modified red mud with 3 wt% loading percentage tends to form some aggregated particles within the polymer matrix leading to higher roughness values as compared to the PNC3.

Sample

Ra (nm)

Rmax (nm)

Rq (nm)

Pure Ph

3.297

27.668

4.173

PNC3

4.045

57.648

5.497

PRC3

4.562

116.65

7.003

Table 16. Roughness parameters for Pristine Ph and the Ph nanocomposite membrane surfaces