Porod scattering

Figure 1. SANS of evacuated mesoporous Figure 2. Dependence of I(Q) for sample silica, SIM (dp - 6nm). SANS contains two SIM in the Porod Scattering region (at Q = components (a) at low Q - Porod Scattering 10-2A-1) on fractional volume filling of (b) at high Q - Diffraction. mesopores, 0, with matched benzene.

Thus for Porod scattering from a two phase system we have (11,12) ... 

II. (b), has an intensity which decays with a power law close to that observed in the Porod scattering region, viz. 

The term Ip/q in Eq. (4.144) accounts for the Porod scattering [104], which is caused by the granular. structure of the CPG-10 and the resulting contrast between the matrix and the liquid in the interstitial space. The term /bg accounts for the noncoherent scattering background resulting from the nondeuterated organic liquid. 

Aggregates representing large three-dimensional objects with sharp interfaces give rise to Porod scattering [48] ... 

Other than PEB-11, in addition to the low temperature power law behavior, a correlation peak evolves at aroimd Q = 0.025 A . For the intermediate temperature range (between 40 and 20 °C), a Q behavior at low Q appears. The low-Q Porod scattering indicates formation of large aggregates featuring a weU-defined surface, while its attenuation with decreasing tern-... 

Figure 9.11 Scattered intensity (black dotted Une) of PCL60 with Porod fit (light gray line). The continuous fine gives the sum of the Porod scattering and a background (dashed fine) due to density fluctuations.

As pointed out by Klee et al., such a system can also be modeled using Eq. (6.33). This was accomplished by approximating the dilute phase as a polydisperse system of core-shell particles [37] and assuming a hard sphere structure factor however, the effect of polydispersity on the structure factor was not accounted for [62]. As well, the GIFT analysis has also been used to verify the presence of a core-shell structure [73]. Ultimately, there is more than one single model that can accurately describe the SAXS in terms of the peak intensity, average size, and Porod scattering law. For example, a eore-shell structure can correctly account for the shell of amphiphilic molecules at the surface of the microemulsion, which Eq. (6.36) cannot. 

Here, Eq. 30 represents the mean square of the sectional curvature averaged around the normal vector. The first term in Eq. 28 is the Porod scattering [81]. The crossover from q "(n>6) to q with increasing q in the structure factor occurs at qcRm— [78, 79]. 

For stmctures that display Porod scattering, following eqn [2] with P = 4, a relationship exists between the Porod prefactor, B,... 

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