This November I had a great opportunity to visit DESY (Deutsches Elektronen-Synchrotron DESY) in Hamburg. Among 18 larger synchrotron facilities in Europe, Petra III in DESY is equipped with the biggest and most brilliant storage ring for X-ray emission.
Such a powerful X-ray beam can be produced by generating and manipulating accelerated electrons: Electrons travel inside a synchrotron’s storage ring only a little bit slower than the speed of light. The high-speed and high-energy electrons, when forced to change their trajectory by a set of specialized magnets, emit radiation at X-ray wavelengths (0.01 to 10 nm). This wavelength range is suitable to study interatomic distances within solids, and thus to reveal their structural properties. X-rays produced synchrotron are orders of magnitude more brilliant than those produced by commonly used X-ray tubes: this means that photons at X-ray wavelengths in the synchrotron X-ray beam are highly directed and have a very high concentration per unit area.
High-energy synchrotron X-ray sources open up possibilities to study complex samples with the best spatial precision and resolution. One of our goals was to get more insight into mineral transformations in confinement: the Surface Forces Sensor setup (SFS) designed at the Vienna University of Technology in Applied Interface Physics group combined with the X-ray beam allowed us to get more complete information about the confined region between reactive mineral surfaces. SFS was used to create and control spatial confinement and to measure normal and shear surface forces acting between two mineral surfaces. Information about mineral phases and changes in their crystallinity were obtained from X-ray scattering.
In the X-SFS setup, a micrometer-sized X-ray beam can be directed very precisely through the most confined region between two probed surfaces. This is also the same region where the surface forces are measured by SFS. Any major changes in surface forces related to the reactivity of solid surfaces can be directly correlated with changes in phase or crystallinity of these solids, as interpreted from the scattered X-rays. Our preliminary findings from these experiments show that mineral transformations can be enhanced by shearing two surfaces against each other, which is relevant to fault zones and other geological environments where friction occurs. Stay tuned for more!
JD 