Transition énergétique

Magnesium rich calcites are important functional biominerals. For example, they can be found in protective shells or eye lenses. Natural organism provide a surprisingly high degree of control on the amount of magnesium incorporation into calcites by yet not well understood mechanisms. Understanding such control mechanism is important when designing bio inspired functional materials. Here we systematically explore the impact of thermodynamic parameters on the degree of magnesium incorporation into calcite. In particular, we identify the thermodynamic conditions, where very high magnesium rich calcites (50% Mg/50% Ca) forms under ambient conditions of temperature and pressure. This is an important finding for geochemistry: Very high magnesium rich calcite is believed to be the precursor for dolomite. Despite its frequent occurrence in nature, its unknown formation pathway remains one of the big mysteries in geochemistry.

Calcium carbonates are key materials to biomineralization, they are frequently used in industrial applications and also for carbon capture technologies. Finally, they serve as an important model system to test novel nucleation theories.  Calcium carbonate crystalizes in a multi-step process, where amorphous calcium carbonate (ACC) is the most important precursor in the crystallization process. Existing synthesis protocols generate ACC of different stability and purity.  To improve our mechanistic understanding of carbonate crystallization, reactivity and polymorph formation, the reproducible synthesis of clean and stable ACC is an important, and yet unresolved step. Here we use the fast reaction of CO2 with calcium hydroxide in airborne aerosols to reproducibly create pure and stable ACC, which may serve as a well-defined starting material for further chemical processing.

Magnesium rich calcites are important functional biominerals. For example, they can be found in protective shells or eye lenses. Natural organism provide a surprisingly high degree of control on the amount of magnesium incorporation into calcites by yet not well understood mechanisms. Understanding such control mechanism is important when designing bio inspired functional materials. Here we systematically explore the impact of thermodynamic parameters on the degree of magnesium incorporation into calcite. In particular, we identify the thermodynamic conditions, where very high magnesium rich calcites (50% Mg/50% Ca) forms under ambient conditions of temperature and pressure. This is an important finding for geochemistry: Very high magnesium rich calcite is believed to be the precursor for dolomite. Despite its frequent occurrence in nature, its unknown formation pathway remains one of the big mysteries in geochemistry.

Calcium carbonates are key materials to biomineralization, they are frequently used in industrial applications and also for carbon capture technologies. Finally, they serve as an important model system to test novel nucleation theories.  Calcium carbonate crystalizes in a multi-step process, where amorphous calcium carbonate (ACC) is the most important precursor in the crystallization process. Existing synthesis protocols generate ACC of different stability and purity.  To improve our mechanistic understanding of carbonate crystallization, reactivity and polymorph formation, the reproducible synthesis of clean and stable ACC is an important, and yet unresolved step. Here we use the fast reaction of CO2 with calcium hydroxide in airborne aerosols to reproducibly create pure and stable ACC, which may serve as a well-defined starting material for further chemical processing.

We study the gas diffusion in still liquids under gas high pressures. We demonstrate that the pressure-induced gas diffusion, liquid swelling and the liquid surface tension can be measured simultaneously in a one-pot experiment. The measurements are performed using the high-resolution neutron imaging in a non-tactile way. A major advantage of this new method is that the determination of surface tension necessitate no assumptions imposed on the properties of the liquid.

Long-wavelength pulses from the Swiss X-ray free-electron laser (XFEL) have been used for de novo protein structure determination by native single-wavelength anomalous diffraction (native-SAD) phasing of serial femtosecond crystallography (SFX) data.

We present a combination of thermodynamic and dynamic experimental signatures of a disorder driven dynamic cooperative paramagnet in a 50% site diluted triangular lattice spin-1/2 system: Y₂CuTiO₆. Magnetic ordering and spin freezing are absent down to 50 mK, far below the Curie-Weiss scale (-θ_CW) of ∼134 K. 

We generate frequency-tunable narrow-band intense fields in the terahertz (THz) range by optical rectification of a temporally modulated near-infrared laser pumping a nonlinear organic crystal.

A fundamental understanding of the active sites in technical CoMo/ Al₂O₃ catalysts is crucial to improve the production of clean transportation fuels by hydrodesulfurization (HDS), which removes sulfur from fossil fuels. Sulfur dioxide, resulting from fossil fuel combustion, is one of the main causes for acid rain. In situ X-ray spectroscopic experiments at the SuperXAS beamline of the SLS provided insight in the structure and number of active sites (“Co−Mo−S”) in sulfided CoMo/ Al₂O₃ catalysts. When the Co to Mo ratio is less than 0.1, cobalt forms isolated sites on the MoS₂ phase, where the cobalt promoter atoms are in centrosymmetric octahedral coordination with six-sulfur ligands.

We report muon spin rotation and magnetic susceptibility experiments on in-plane stress effects on the static spin-stripe order and superconductivity in the cuprate system La_2−xBa_xCuO₄ with x = 0.115. An extremely low uniaxial stress of ∼0.1 GPa induces a substantial decrease in the magnetic volume fraction and a dramatic rise in the onset of 3D superconductivity, from ∼10 to 32 K.

A safe, economical and environmental friendly disposal of used nuclear fuel represents an essential objective of relevance for all. This guides the approach under development at the laboratory for reactor physics and thermal-hydraulics. Establish higher resolution simulation methods to gain more detailed knowledge on the content of each single nuclear fuel rod ever irradiated in a reactor. Thereafter, use this knowledge to explore optimization approaches that could potentially enlarge the range of disposal options allowing to fulfill the highest level of safety standards while reducing economical costs and geological footprints at the same time.

A group of EMPA and ETH Zürich researchers have developed a new method to directly write ink made of silica aerogels in 3D. Thanks to X-ray phase contrast tomography at the TOMCAT beamline they characterized the resulting printed material with different compositions. Their results were published in Nature on August 18, 2020.

A group of EMPA and ETH Zürich researchers have developed a new method to directly write ink made of silica aerogels in 3D. Thanks to X-ray phase contrast tomography at the TOMCAT beamline they characterized the resulting printed material with different compositions. Their results were published in Nature on August 18, 2020.

A cyan light (492 nm) emitting colloidal suspension of CsPbBr₃ nanoplatelets in a flask, together with the high-quality XRPD Total Scattering pattern of the suspension measured at the X04SA-MS beamline and the full-nanoparticle structure thereby inferred.