A new model to describe small-angle neutron scattering from foams

Abstract

The modelling of scattering data from foams is very challenging due to the complex structure of foams and is therefore often reduced to the fitting of single peak positions or feature mimicking. This article presents a more elaborate model to describe the small-angle neutron scattering (SANS) data from foams. The model takes into account the geometry of the foam bubbles and is based on an incoherent superposition of the reflectivity curves arising from the foam films and the small-angle scattering (SAS) contribution from the plateau borders. The model is capable of describing the complete scattering curve of a foam stabilized by the standard cationic surfactant tetradecyltrimethylammonium bromide (C14TAB) with different water contents, i.e. different drainage states, and provides information on the thickness distribution of liquid films inside the foam. The mean film thickness decreases with decreasing water content because of drainage, from 28 to 22 nm, while the polydispersity increases. These results are in good agreement with the film thicknesses of individual horizontal foam films studied with a thin-film pressure balance.

Foam aging under free drainage analysed using associated operando techniques

“…The combination of these three techniques allows to perform this multiscale analysis in real time on a given sample. In particular, the analysis in absolute scale of the SANS data allows to quantify the specific surface areas from Plateau borders and from inter-bubble thin films as well for which time their evolution can be correlated to the film thickness variation, while the analysis of the SANS data in arbitrary units only provided reliable values for the foam film thickness 48,49 .…”

“…While several examples dealing with the analysis of SANS data from liquid foams can be found in the literature [40][41][42][43][44][45][46]48,49 , this is the first example of a quantitative analysis, in absolute scale, of the scattering data recorded from liquid foams. The fitting procedure was done considering a film roughness of σ = 1.5 nm.…”

“…In-situ foam film thickness measurement is possible performing small-angle neutron scattering (SANS) [40][41][42][43][44][45][46][47][48][49] . SANS data also provide information on the internal structure of the foam solution over a large length scale.…”

Probing foams from the nanometer to the millimeter scale by coupling small-angle neutron scattering, imaging, and electrical conductivity measurements

“…While several examples dealing with the analysis of SANS data from liquid foams can be found in the literature [39][40][41][42][43][44][45]47,48 , this is the first example of quantitative analysis, in absolute scale, of the scattering data recorded from liquid foams. The analysis was performed using a value for the film roughness Σ of 1.5 nm, which is much larger than the roughness due to thermal fluctuation of around 0.3 nm.…”

“…In-situ foam film thickness measurement is possible performing small-angle neutron scattering (SANS) [39][40][41][42][43][44][45][46][47][48] . SANS data also provide information on the internal structure of the foam solution over a large length scale.…”