Mesoporous silica formation mechanisms probed using combined Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) and Small Angle Neutron Scattering (SANS)

International audienceThe initial formation stages of surfactant-templated silica thin films which grow at the air−water interface were studied using combined spin−echo modulated small-angle neutron scattering (SEMSANS) and small-angle neutron scattering (SANS). The films are formed from either a cationic surfactant or nonionic surfactant (C16EO8) in a dilute acidic solution by the addition of tetramethoxysilane. Previous work has suggested a twostage formation mechanism with mesostructured particle formation in the bulk solution driving film formation at the solution surface. From the SEMSANS data, it is possible to pinpoint accurately the time associated with the formation of large particles in solution that go on to form the film and to show their emergence is concomitant with the appearance of Bragg peaks in the SANS pattern, associated with the two-dimensional hexagonal order. The combination of SANS and SEMSANS allows a complete depiction of the steps of the synthesis that occur in the subphase

Evolution of dispersion in the melt compounding of a model polymer nanocomposite system: A multi-scale study

We investigate the morphological development of polystyrene (PS)-C 60 nanocomposites along the length of a prototype co-rotating twin-screw extruder with sampling capabilities. The effects of C 60 concentration and output on the morphological evolution along the extruder are studied employing a suite of characterization techniques covering a wide range of length-scales, thereby shedding new light on the dispersion mechanism in this model system. We show that the relatively new spin-echo small-angle neutron scattering (SESANS) technique is well suited to probe both the distribution and the dispersion of C 60 . SESANS complements optical microscopy (OM) data as it covers sampling areas several orders of magnitude larger than OM. The multi-scale morphological information conveyed by OM, SESANS, SANS and rheological data shows that for larger outputs, C 60 agglomerates are eroded as they travel along the extruder, resulting in C 60 dispersion and distribution at both molecular and micrometric levels. The picture is more complex when smaller feed rates are used, as the evolution of C 60 dispersion depends on the C 60 loading. For larger C 60 contents, agglomeration develops along the extruder, whereas dispersion is improved for smaller C 60 contents. Overall, it is concluded that an over-high feed rate in extrusion does not necessarily result in a bigger size of the nanoparticle agglomerates because of the complex interplay between stresses and residence time. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Technici PoolTechnici PoolRST/Neutron and Positron Methods in MaterialsRST/Fundamental Aspects of Materials and Energ