condensed matter – Lightsources.org

Using uranium to create order from disorder

2018/08/302018/08/30

The first demonstration of reversible symmetry lowering phase transformation with heating.

ANSTO’s unique landmark infrastructure has been used to study uranium, the keystone to the nuclear fuel cycle. The advanced instruments at the Australian Synchrotron and the Australian Centre for Neutron Scattering have not only provided high resolution and precision, but also allowed in situ experiments to be carried out under extreme sample environments such as high temperature, high pressure and controlled gas atmosphere.

As part of his joint PhD studies at the University of Sydney and ANSTO, Gabriel Murphy has been investigating the condensed matter chemistry of a crystalline material, oxygen-deficient strontium uranium oxide, SrUO_4-x, which exhibits the unusual property of having ordered defects at high temperatures.

“Strontium uranium oxide is potentially relevant to spent nuclear fuel partitioning and reprocessing,” said Dr Zhaoming Zhang, Gabriel’s ANSTO supervisor and a co-author on the paper with Prof Brendan Kennedy of the University of Sydney that was published recently in Inorganic Chemistry.
Uranium oxides can access several valence states, from tetravalent— encountered commonly in UO₂ nuclear fuels, to pentavalent and hexavalent—encountered in both fuel precursor preparation and fuel reprocessing conditions.
Pertinent to the latter scenario, the common fission daughter Sr-90 may react with oxidised uranium to form ternary phases such as SrUO₄.

Image: Dr Zhaoming Zhang and Gabriel Murphy.

The Molecular Scale Structure of Electrolyte-Metal Oxide Interface

2018/02/282018/03/08

Li-ion batteries (LIBs) are key components of portable electronic devices, as well as in electric vehicles, military and medical equipment, backup power supplies, and even grid storage. However, the energy storage capacity and rate capability of current LIBs is still too low to meet the increasing demand of key markets. For the latter, the properties of the electrolyte-electrode interface play a decisive role.

From a more general point of view, interfaces, or surfaces, are the outer boundary of any condensed matter. Due to the resulting symmetry breaking, the arrangement of atoms or molecules at the interface often varies significantly from that in the bulk. Studies of the molecular scale structural properties of liquids at interfaces are intriguing, as these give insights into the fundamental molecule–molecule and molecule–substrate interactions. Investigations have included layering of ionic liquids [1], layering of metallic [2] and non-metallic liquids [3], and the (potential-dependent) structure of water adsorbed on solid surfaces [4]. However, basic insights into how a non-aqueous electrolyte–salt solution organizes at a solid interface, in particular from experiments, is still missing [5]. In many technological applications, the atomic scale properties of interfaces govern the functionality of the system. A prominent example is the importance of the structure and molecular arrangement of the liquid at the functional solid–liquid interface in batteries. More specifically, in LIBs, the arrangement of the electrolyte molecules directly at the electrode interface, and the electric double layer (EDL) formation are expected to govern the interfacial ion transport during charge/discharge, as well as affect the origin and properties of the solid electrolyte interphase (SEI).

Image: (a) Fresnel-normalized XRR (symbols) of the sapphire/LiPF₆:EC:DMC and corresponding model fits (lines). (b) Fit-derived electron density profiles. (c) Comparison of the XRR- and MD-derived (blue) density profiles. The MD-derived profile is smeared by the XRR-derived roughness. All curves are spaced vertically for clarity. (d) Periodicity at the solid/liquid interface vs. LiPF₆ concentration. (e) Normalized correlation lengths. (f) Schematic illustration of the proposed origin induced increased layer spacing with increasing salt-concentration.

G. Ghiringhelli and L. Braicovich win 2018 Europhysics Prize of Condensed Matter

2018/01/222018/01/24

Giacomo Ghiringhelli and Lucio Braicovich were awarded the 2018 Europhysics Prize of the Condensed Matter Division of the European Physical Society (EPS), for their groundbreaking work « for the development and scientific exploration of high-resolution resonant inelastic x-ray scattering (RIXS) ».

Awarded once every 2 years, the EPS Condensed Matter Europhysics Prize is one of Europe’s most prestigious prizes in the field of condensed matter physics. The Prize will be presented on Tuesday March 13th, 2018, at the Awards Session of the 27th General Conference of the EPS Condensed Matter Division, to be held in Berlin.

>Read more on the ESRF website