I22 (Gi)SAXS/WAXS

This technique allows the user to investigate the long range order associated with samples in thin film geometry. There is a community Wiki held at gisaxs.com with useful links to further information including an excellent introduction to the technique on the Cornell Website.

We have recently developed a Grazing incidence capability for I22 to compliment that on I07 for longer length scale measurement. It shoud be noted that liquid interfaces need to be measured on I07 as I22 does not have a DCD to manipulate the incident gazing angle of the beam without titling the sample itself.

The upgrade comprises a set of 3 beamstops to protect the SAXS detector from a) direct beam, b) reflected beam and c) specular reflection. In Grazing Incidence mode both of these beams and the specular scatter are strong enough to damage the detector if they are allowed to fall on its surface. An additional function of a) and b) was to measure the intensity of the beam at these points. Diodes in the direct beam and reflected beam can also be saved with scattering patterns for normalisation of the data in I22’s Nexus files. In delivering the upgrade independent motion of beamstops and detectors was also achieved making beamline set up more efficient.

The GiSAXS upgrade also includes an improved sample platform giving more precise control over height, pitch, yaw and roll of samples for data collection. This has been delivered in the form of a Symétrie hexapod and sample platform which includes an annealing stage and doctor blade sample preparation system. Some work is required to improve the thermal performance of the sample stage but this will be carried out during operations.

Fatty acid surfactant films, such as oleic acid-sodium oleate, form mixed lamellar and amorphous structures that persist even after simulated atmospheric ageing. Oxidation increases the films’ ability to absorb water, which may prolong their atmospheric lifetime and impact air quality and climate.

The evolution of surface structure during simulated atmospheric ageing of nano-scale coatings of an organic surfactant aerosol proxy

A. Milsom, A. M. Squires, M. W. A. Skoda, P. Gutfreund, E. Mason, N. J. Terrill, et al.

Environmental Science-Atmospheres 2022 Vol. 2 Issue 5 Pages 964-977

DOI: 10.1039/d2ea00011c