Welcome to the Materials Science Group
The MS Group is interested in determining the atomic structures of technologically relevant materials using diffraction/scattering techniques. Areas of interest include surface and interface diffraction, particularly of complex metal oxides (perovskites); total scattering of nanoscale "real systems"; and high-pressure crystallography of catalytically relevant systems. We also provide a commercial service in collaboration with Excelsus Structural Solutions for studies of crystals of small organic molecules of pharmaceutical interest.
The Materials Science group is broadly divided into two subgroups, corresponding to the two serially serviced end stations. Upstream powder diffraction and pair-distribution-function (PDF) experiments can be carried out under a broad palette of sample conditions, covering a large range of temperatures, pressures, and sample types. Downstream, a large 5-circle surface diffractometer allows experiments to be performed on the detailed sub-Angstrom structure of surfaces and interfaces, also under various sample conditions.
The beamline has recently been upgraded from wiggler- to undulator radiation, with a concomitant increase in brilliance of several orders of magnitude. With this quantum step in improvement, new sorts of experiments are being explored, in particulat time-resolved small- and wide-angle x-ray scattering (SAXS/WAXS) for the study of transient phases and chemical dynamics on the sub-second to millisecond scale; coherent x-ray diffraction imaging (CXDI) for the study of strain fields in micron and nanoscal crystals; and micro-Laue experiments for studies of dynamics in single-crystal samples.
The structural changes of Na3.32Fe2.11Ca0.23(P2O7)2 during several charge discharge cycles is viewed by its powder pattern and selected cell parameter evolution.
The progressive hydrostatic compression of I2 and I3- units in an organic salt lead to a homoatomic polymeric chain. As the I---I distance collapses the covalent character of the interaction becomes more relevant, leading to a pressure-tunable increased conductivity.
Additive manufacturing of high-entropy alloys combines the mechanical properties of this novel family of alloys with the geometrical freedom and complexity required by modern designs. An approach to additive manufacturing of high-entropy alloys has been developed based on 3D extrusion of inks containing a blend of oxide nanopowders (Co3O4 + Cr2O3 + Fe2O3 + NiO), followed by co-reduction to metals, inter-diffusion and sintering to near-full density CoCrFeNi in H2. A complex phase evolution path is observed by in-situ X-ray diffraction in extruded filaments: the oxide phases undergo reduction and the resulting metals inter-diffuse, ultimately forming the desired fcc-CoCrFeNi alloy (see figure). Linked to this phase evolution is a complex micro-structural one, from loosely packed oxide particles to fully-annealed, metallic CoCrFeNi with 99.6 ± 0.1% relative density. CoCrFeNi micro-lattices are created with strut diameters as low as 100 μm and excellent mechanical properties at ambient and cryogenic temperatures.