Small-angle scattering SANS

SANS see Neutron, small angle scattering (SANS)... 

The GNOM program [38] was used for treatment of the experimental small-angle scattering (SANS and SAXS) data. It reads one-dimensional scattering curves and calculates the distance distribution function p(r). The least-squires... 

The most frequently encountered use of neutrons in the study of polymers is the measurement of small angle scattering (SANS). Use of neutrons with wavelengths in the range 0.5-2 nm and scattering angles between 0.1° and 10° readily allows... 

The experimental techniques for the study of conformational branched properties in solution are the same as used for linear chains. These are, in particular, static and dynamic light scattering, small angle X-ray (SAXS) and small angle neutron (SANS) scattering methods, and common capillary viscometry. These methods are supported by osmotic pressure measurements and, nowadays extensively applied, size exclusion chromatography (SEC) in on-line combination with several detectors. These measurements result in a list of molecular parameters which are given in Table 1. 

Nevertheless, small-angle scattering techniques are not very suitable for the study of lower dendrimer generations because such dendrimers yield only weak scattering signals and a high uncertainty factor therefore exists. SANS and SAXS experiments are not only costly, but also make substantial demands on time and require relatively large amounts of substances (several 100 mg). These methods are therefore out of the question for routine use, such as for the determination of the molar mass of dendrimers. 

Small-angle scattering SAXS, SANS (higher generations)... 

Small-angle scattering SAXS, SANS only suitable for higher dendrimer generations SANS is particularly time-consuming and costly, and requires large amounts of sample compared to mass-spectrometric methods... 

Since the porosity of carbons is responsible for their adsorption properties, the analysis of the different types of pores (size and shape), as well as the PSD, 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 texture, from which we can underline the physical adsorption of gases, mercury porosimetry, small angle scattering (SAS) (either neutrons—SANS or x-rays—SAXS), transmission and scanning electron microscopy (TEM and SEM), scanning tunnel microscopy, immersion calorimetry, etc. 

A critical region of the shape parameter (see above) is the range around 5=1, where various phases may coexist and in which small changes of parameters such as hydration and ion concentration may lead to a phase transition. Since frequently the packing parameter cannot be estimated with a sufficient precision, physical techniques such as small-angle scattering with X-rays (SAXS) or neutrons (SANS) must be applied for a reliable determination of the structures. 

For more information on small-angle scattering, see (a) http //www.isis.rl.ac.uk/largescale/loq/ documents/sans.htm (b) http //www.eng.uc.edu/ gbeaucag/Classes/XRD/SAXS%20Chapter/... 

Small Angle scattering (SAS) techniques have been frequently used to provide information about the structure of porous materials as well as the structure of molecular species sorbed within the pore space of these materials (for a recent review see [1]). According to SAS theory, the intensity 1(h) (h is the scattering vector) scattered by a two phase system is related to the electron (SAXS) or scattering length (SANS) densities (s.l.d.) p, and p2 of the phases in terms of the expression ... 

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