Structural Analyses Using SAXS Technique

The sample was heated at 200°C during the SAXS measurement so that the electron density difference between the crystalline and amorphous phases increases. The scattered intensities of the injection-molded pieces in the MD and TD were almost the same values, and hence the samples have no orientation. SAXS data were corrected for transmission, scattering from a cell and air, polarization, and incoherent scattering. The one-dimensional correlation function y(r) was evaluated by the Fourier transformation of the SAXS profile I q), given by [3,4] 

TABLE 18.2 Structural Parameters Obtaiued for SPS/PPO Bleuds with Different PPO Couteuts 

The thickness of the crystalline phase Zc , the amorphous phase /, , and the lamellar long period L are defined, (b) One-dimensional correlation function y(r) of SPS homopolymer. The values of L and l , which are obtained in the manner described in the text, are shown by the arrows. 

It should be noted that the lamellar long period L remains constant, while the thickness of the crystalline phase k decreases with increasing PPO content. The decrease of 4 may be closely related with the crystallization kinetics. In crystallization, SPS molecules segregate the PPO molecules away 

The spatial dimension of segregation of the PPO molecules is predicted by the expression [5] 

---

Because the ACFs are porous carbons that have no significant differences compared with other porous carbons, the techniques used for their characterization are almost the same. Since the porosity in carbons is the responsible for their adsorption properties, the analysis of the different types of pores (size and shape), as weU as the pore size distribution, is very important to foresee the behavior of these porous solids in final applications. We can state that the complete characterization of the porous carbons is complex and needs a combination of techniques, due to the heterogeneity in the chemistry and structure of these materials. There exist several techniques for the analysis of the porous structure, from which we can underline physical adsorption of gases, mercury porosimetry, small-angle neutron and X-ray scattering (SANS and SAXS), transmission and scanning electron microscopy (TEM and SEM), scanning tunnel microscopy (STM), immersion calorimetry, etc. 

Wide- and small-angle scattering are fully developed X-ray techniques for studying structural features. The theory is complete, the experimental devices are well developed, laboratory systems are commercially available, and dedicated X-ray facilities for special applications exist in several international research centers. Data analysis techniques have improved substantially in the last two decades through computers use of numerical methods. By nature, SAXS is used in the study of relatively large-scale structures, while wide-angle X-ray diffraction (WAXD) deals mainly... 

---