IN-SITU NANOSCALE IMAGING OF STRAIN AND PHASE SEPARATION UNDER HIGH PRESSURE

Over last decades, both synchrotron radiation techniques and high pressure research have made great progress. Advanced synchrotron capabilities with high spatial resolution, high flux, high energy resolution and high coherence provides us many new avenues to conduct advanced high pressure researches. In this talk, we will mainly focus on the new developments of the nanoscale imaging techniques on the internal strain distribution and pressure induced phase separation in three dimensions. Coherence of the synchrotron beam for high pressure community has been largely ignored due to the complicated sample environment for data interpolation. We have developed a practical “Mutual Coherence Function” to overcome the influence from the sample condition and extrapolated the full coherent diffraction imaging results from a single crystal nanoparticle. The 3d internal strain evolution as a function of applied pressure shows clearly the nanoscale plastic flow cross the nanograin and provides us fundamental deformation mechanism of individual nanocrystal under pressure. The advanced synchrotron optics also provides us tens of nanometer scale 3d tomography resolution, which in return provides detail structural characterization of materials at extreme conditions. By choosing incident x-ray energy near absorption edge, the pressure induced valence transition can be mapped at tens of nanometer scale in 3d, which provides crucial information on the HP-LP phase boundary. Several new experimental results will be presented and outlook will be discussed.