Scattering curves, shoulders

The effect of mineral matter is so small that it is completely negligible compared to the combined specific surface of the macropores and transition pores in coals with scattering curves which have a shoulder. 

There are pronounced shoulders on the scattering curves for PSOC Coals 105, 022, and 188, while there are no shoulders on the curves for Coals 197 and 138. The shoulders in the scattering curves from Coals 185 and 181 are less evident, and a shoulder can be seen for Coal 212 only after careful inspection. These results suggest that there will be well-defined shoulders in the scattering curves only when the specific surface of the transition pores is at least ten times as great as that of the macropores. 

Figure 7 X-ray scattering curves from human SC hydrated to different extents, (a) Scattering curves hydrated to levels from 6% (w/w) to 60% (w/w). The shoulder on the...

Between 60 and 75°C, a disordering of the lamellar structure appears to occur that coincides roughly with a thermal transition (Bouwstra et al., 1989 Golden et al., 1986 van Duzee, 1975). The scattering curve measured at 75°C, shown in Fig. 9, shows only a shoulder on the descending scattering curve. 

Figure 9 Scattering curves from human SC at 75 and 95 C. On both curves a small shoulder appears (arrow) that disappears after heating to I20°C followed by recrystallization at room temperature and then reheating to 75"C.

Small angle scattering experiments confirm that the polymer-bound micelles form distinct necklaces (12). Figure 4 shows the scattering curves of micelles bound to a FEO of M - 1.35E5. Here the shoulder corresponds to a separation between bridged micelles, with a low coordination number and a separation d 3 diameters. 

The scattering curves of samples of the gel region, shown in Fig. 9, show a more or less pronounced shoulder between 0.07 and 0.22 nm . This feature can be interpreted as a smeared correlation peak caused by periodic lamellar structures. It occurs in a similar range of Q values as the peaks observed for the more concentrated SDS/CA-SA/water system investigated by X-ray scattering [1]. For sample J3 the lamellar correlation peak corresponds to a periodic distance of 39.3 nm, which is higher than the value observed for the more concentrated system with a mixture of the alcohols CA and SA. There is no obvious trend in position or shape of the correlation peak for samples with different y. This may be due to the fact that the applied protocol of sample preparation does not ensure a fully reproducible structure of the samples. 

There is a range of thermoplastics whose chemical configuration consists of phenylene units bridged by a variety of groups. Table II indicates the stracture of the polymers considered. Figure 23 shows the reduced intensity functions si (s) for these six polymers. Although there is considerable variety in the shapes and relative intensities of the peaks within these curves, they have several features in common. First, they exhibit an intense peak at s 1.5 with other weaker peaks at j = 3 and 5.5 A l. A number of these polymers have been considered in detail,and their intrachain, orientational, and spatial parameters evaluated. Here we would like to focus our attention on one particular feature also common to all these si (s) curves, namely the shoulder or feature at 5 = 1.9 A l. In particular we shall consider the scattering curve for polyphenylene sulfide (PPPS). 

When Fernandez et al. studied partially polymerized Series P PB/PS systems, SANS results yielded peaks in the scattering patterns, see Figure 14 [ ]. Early attempts at understanding these peaks were troublesome due to the multiple causes for such peaks. Later, similar peaks were observed in another set of samples, which were partially swollen, then fully reacted (series S) by An et al. [41], but, in this case, shoulders instead of distinct maximum were observed (Figure 15). In both cases, such maximum or shoulders appeared at mid-range compositions, then were replaced by smoothly decreasing curves on further polymerization of monomer II. 

Fig. 1. Powder x-ray profiles of solid Ceo at atmospheric pressure (top) and 1.2-GPa hydrostatic pressure (bottom). Dots are experimental points (approximately 70 per point), and the solid curves are least-squares fits to an fee structurewith adjustable lattice constant a. The fitted relative intensities have no physical significance in this simple model. The scattered wave vector Q = 4TTsin6/X, where 0 is the Bragg angle for these profiles wavelength = 0.71 A. Indexing of the strongest peaks is indicated. The high-Q shoulder on the (311) is the weak (222) reflection the low-Q shoulder on the (111), observed to some extent in all our nominally pure Cfio samples, is presently unidentified. The variable intensity of this shoulder has litde eflfect on the lattice constant of a particular sample, so we can safely conclude that it has no effect on the compressibility derived from the present data.

In Figure 1, the total coherent scattering intensities from a 3.9 mol% aqueous solution of TBA (solid curve) and pure water (dotted curve) are shown. A monotonically decreasing curve (thin solid curve) is the theoretical self-scattering intensity. The difference in the intensity between water and solution is clearly seen in the large first peak and the second shoulder peak, but there is no difference in the phase (peak position) in the two curves. Note that, in spite of the very low concentration of TBA, the decrease in the intensity mentioned above is drastic. 

By the Fourier transformation of the scattering intensities, radial distribution functions (RDF) are obtained as sho n in Figure 2. A shoulder-like small peak is detected at r = 1.6 A in the RDF for the solution, which is ascribed to the intramolecular C-C and C-0 interferences of TBA. However, due to the low concentration of TBA, the contribution of the structural correlation between water and TBA molecules to the RDF is very small and smeared. The radial distribution curve shows only water-water(more exactly, oxygen-oxygen) correlation even for the TBA aqueous sulution. ... 

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