Characterisation of Pyrogenic Aggregates with Static Scattering Techniques

1 Characterisation of Pyrogenic Aggregates with Static Scattering Techniques 

Scattering techniques measure the intensity of a scattered signal versus the value q of scattering vector (cf. Sect. 2.3.4). The principal shape of such a scattering curve is shown in Fig. 4.22. 

The curve was calculated for g-values from 0.3 pm to 0.3 and, thus, reveals properties of the whole aggregates as well as of the surface of the primary particles. However, such a broad g-range cannot usually be covered by a single scattering instrument. Typically, static light scattering (SLS) is operated in the range from 0.001 to 0.03 nm while laboratory SAXS instmmentation covers 

An alternative data analysis consists of fitting experimental scattering curves with model equations. Such equations can be established by combining analytical expressions for the form factor P(q) (e.g. Eq. (B.54)) with those for the aggregate stmcture (e.g. Eq. (4.26)). Hurd et al. (1987) proposed a four-parametric equation that is based on the Fisher-Burford approximation of the aggregate strucmre factor (Eq. (4.24))  

Once having obtained an analytical description of the scattering curve, it is possible to calculate the Porod invariant Q (cf. Eq. (2.25)) from the primary particle contributions 

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