IFME software

Several approaches have been done to quantify membrane morphology parameters from SEM images. The first attempts were made in the early 1990s. They permitted more quantitative information to be obtained from membrane SEM micrographs and they showed the potential power of computer-aided SEM analysis [30, 31]. More recentiy, other approaches based on different model equations have been reported [32, 33]. The IFME software [32], was developed by our research group within the past years and permits numerical results of the main morphological parameters to be obtained from SEM micrographs. 

The most important is the last one. To obtain it, the sample needs to be previously treated. The membrane has to be broken, but not cut in order to preserve the porous structure. To do this, the most used technique is to dip the sample in an ethanol bath (to ensure that all the pores of the membranes are filled with the alcohol) and afterwards to immerse it in a liquid nitrogen bath to freeze the ethanol. Then, the membrane can be broken. Once the micrograph is obtained, it has to be interpreted. It is desirable to obtain numerical results of the main morphological parameters, such as the pore size distribution, porosity, symmetry, regularity and tortuosity. To obtain these parameters in a systematic and fast way the IFME software can be used [32]. 

Figure 33 (a) Cross-section SEM micrograph of a membrane obtained with 15% PSf in DMF and precipitated in water as a nonsolvent. Scale bar=100pm. (b) Graphical results obtained by IFME software after interpreting a cross-section micrograph from a porous polymeric membrane. 

Figure 3.3a shows a typical cross-section micrograph obtained by SEM from a polysulfone membrane. If the micrograph is being interpreted by using the IFME software, graphical results are obtained as Figure 3.3b shows and numerical results are obtained as Table 3.1 shows. 

A study of asymmetric lignosulfonated modified polysulfone-polyamide PS/PA-LS20 membrane was also carried out by IS measurements. Figure 9.14 shows the cross-section SEM micrographs of the PS/PA-LSIO membrane, which were analyzed by using IFME software [52] these results indicate the membrane with a thickness of 92 pm presents an open central zone (porosity of 42%, mean pore radii of 2.95+ 0.13 pm) and a dense top layer of 2.7 pm thickness and (98.00 + 0.08) nm mean pore radii, where the lignosulfonate is mainly located [51]. 

The performance of an imaging system for IFM depends on several parameters including the temporal, spatial, and spectral resolution, the imaging detector sensitivity (signal-to-noise ratio), and the image analysis hard and software used to quantify and document the results. 

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