In the week of April 1-5 PSI welcomes 20 PhD students and postdocs taking part in the European HERCULES 2019 school on Neutron and Synchrotron Radiation. They will attend lectures and perform two days of practical courses at several beam lines of the Swiss Light Source.
To date the electrochemical activity of battery materials was always relying in the oxidation/reduction of cationic redox (change of oxidation state of transition metals generally). However, recently, it was established in new cathode materials (so call Li-rich cathode) that the oxygen from the crystal lattice might also play the role of anionic redox center leading to enhance then the specific charge of battery materials.
A new compact von Hamos spectrometer for tender x-rays (current energy range 2.25-4.5 keV), is now available for emission spectroscopy. This spectrometer allows analyzing the energetic composition of fluorescent light from the sample. It provides research opportunities for emission spectroscopy, and RIXS on the K (P-Sc), L (Zr-Cs) and M (Ir-Fr) absorption edges.
Carbonate minerals serve as reservoir for CO2 in the global CO2 cycle, as biomineral in animal skeletons and shells of marine animals, and are used in carbon capturing techniques. Moreover, they serve as an important model system in crystallization studies, and have important commercial applications, for example as fillers. Researchers from EPFL and PSI developed a new methodology to study the crystallization of CaCO3 that offers both high temporal and spatial resolution, which is the key challenge in elucidating early stages of crystallization. Using X-ray absorption spectroscopy and other techniques it could be demonstrated that the degree of hydration of amorphous CaCO3 increases during its growth. As a result of the increasing degree of hydration, the stability of the resulting amorphous particles against solid-state crystallization decreases.
Single atomic layers of aluminum oxide embedded in SiO2 thin films, play an important role for the design of carrier-selective passivating contacts for high efficiency silicon based photovoltaic applications. Researchers from the Australian National University (ANU, Canberra, Australia), the Karlsruhe Institute of Technology (IT, Karlsruhe, Germany) and PSI have used synchrotron radiation to reveal the bonding configuration and local atomic surrounding of the Al-atoms in such surface oxide layers. The results corroborates theoretical calculations and contribute to a new model to explain the origin of the negative fixed charge in the Al-O/SiO2 stack, which has promising properties for a carrier-selective passivating contact for future silicon solar cells.
When man-made stones meet natural rocks – Shedding light on Mg-rich phases appearing at the interface between concrete and clay
Claystones and cement-based materials are key materials for safe disposal of radioactive waste in deep geological repositories. In Switzerland, Opalinus Clay, was selected as geological host material. At the Mont Terri rock laboratory the alteration of cement in contact with the natural clay is studied in a several years lasting experiment. The formation of different magnesium containing phases at the interface was studied using X-ray absorption micro-spectroscopy at the PHOENIX beamline of the Swiss Light Source (SLS).
In the week of March 18-23 PSI welcomes 20 PhD students and postdocs taking part in the HERCULES 2018 school on Neutron and Synchrotron Radiation. They will attend lectures and perform two days of practical courses at several beam lines of the Swiss Light Source.
Classical theory predicts that supersaturated carbonate solutions consist mostly of ions and ion pairs, with a small number of larger clusters present in the solution. The population of the different sized clusters in a solution is solely defined by the cluster’s size dependent Free Energy. If clusters are large enough they serve as nucleation germs for a new solid phase. The nucleation occurs once the surface free energy barrier posed by the new solid-liquid interface is overcome by the free energy win from bulk phase growth.
How is sulfur incorporated in biogenic carbonates and how is it affected by hydrothermal alteration?
Sulfate in biogenic carbonates is an important proxy for reconstructing the marine sulfur cycle. To investigate the exact location of carbonate associated sulfate (CAS) in biogenic carbonates and the effects of diagenetic alteration on sulfur in carbonates, shells of the marine bivalve Arctica islandica were artificially altered in modified seawater. Sulfur XANES analyses showed that CAS in A. islandica is indeed incorporated into the mineral part of the pristine shell, most likely as a hydrated or partly hydrated sulfate phase. The multi-analytical approach of XANES and µ-XRF analyses, sulfur isotope measurements, NanoSIMS analyses, and microstructural analysis on thin-sections of the shell samples further revealed that the different sulfur in a bivalve shell sensitively reacts to artificially induced hydrothermal alteration.