TIMEleSS

The TIMEleSS project aims at studying interfaces in the Earth’s mantle combining observations from seismology, mineral physics experiments, microstructures, and wave propagation modeling. It is supported through a bilateral grant, from the ANR in France and the DFG in Germany. The project is led by Sébastien Merkel and Nadège Hilairet at the Université de Lille, Christine Thomas and Carmen Sanchez-Valle from the Westfälische Wilhelms-Universität, Münster, and Sergio Speziale from the Deutsche GeoForschungsZentrum, Potsdam.

Project launch: March 2018
Duration: 36 months, extended until December 2022
Total ANR-DFG funding: 700 000 €

Latest news

TIMEleSS Tools for Multigrain X-ray Diffraction

26 June 2022 | Posted in Experiments, TIMEleSS news

TIMEleSS toolsIn addition to contributing the TIMEleSS Multigrain Wiki, TIMEleSS members also released a set of python and matlab utilities to process, analyze, plot, and understand multigrain X-ray diffraction data. All are released under an open-source licence at GitHub on the TIMEleSS-tools and TIMEleSS-Matlab repositories.

TIMEleSS-tools include various utilities to process images, clean up parasite signals on the X-ray diffraction images, manage your peaks and grains, and post-process the output of the various multigrain XRD sofwares.

TIMEleSS-Matlab are MTEX functions one can use to represent grain orientations in pole or inverse pole figures with efficient and intuitive color scales.

Enjoy, and do not hesitate to push any improvement you might make!

TIMEleSS Multigrain Wiki

| Posted in Experiments, Outreach, TIMEleSS news

TIMEleSS Multigrain WikiMultigrain X-ray diffraction (sometimes called 3D-XRD or HEDM depending on communities) allows characterizing hundreds of crystals in a polycrystalline material. It has been adapted to diamond anvil cell experiments for the investigation of materials under high pressure and high temperature. The method lies at the core of the experimental portion of the TIMEleSS project. We use it to characterize transformation and deformation microstructures in mantle minerals.

Multigrain X-ray diffraction can be hard to learn and implement. Hence, along the course of the project, timeless members documented their procedures for processing such data in an online documentation: the TIMEleSS Multigrain Wiki.

We are now finished with our rounds of experiments, data has been processed, and results are being submitted for publication, so it is time to give back to the community! The TIMEleSS Multigrain Wiki has been accessible for years to who knew the URL. Now the link is public and should be easy to find with your best search engines. Please use it, enjoy it, and do not hesitate to contact us if you want to contribute and suggest corrections

This wiki, among with other outputs, was used as a basis for the creation of the Commission on Diffraction Microstructure Imaging of the International Union of Crystallography. This new Commission on Diffraction Microstructure Imaging was established at the Prague General Assembly in August 2021 and TIMEleSS PI S. Merkel is one of the founding members for the application.

New publication in Frontiers in Earth Science

9 May 2022 | Posted in Publications, TIMEleSS news

Deformation of Polycrystalline MgO Up to 8.3 GPa and 1270 K: Microstructures, Dominant Slip-Systems, and Transition to Grain Boundary SlidingWe have a new publication! On May 9th, 2022, former TIMEleSS PhD student Estelle Ledoux published a new paper in Frontiers in Earth Science: Deformation of Polycrystalline MgO Up to 8.3 GPa and 1270 K: Microstructures, Dominant Slip-Systems, and Transition to Grain Boundary Sliding.

The work is a result of a collaboration between the Université de Lille and the University of Utah. We focus on polycrystalline periclase, the pure Mg end-member of the second-most abundant mineral in the Earth lower mantle, ferro-periclase, for which mechanical properties are important to understand flow and the dynamics of the Earth mantle.

we deform polycrystalline periclase at conditions ranging from 1.6 to 8.3 GPa and 875–1,270 K. We analyse the flow laws and microstructures of the recovered samples using electron microscopy and compare our observations with predictions from the literature. We identify a first mechanism for samples deformed at 1,270 K, attributed to a regime controlled by grain boundary sliding accommodated by diffusion, and characterized by a small grain size, an absence of texture, and no intracrystalline deformation. At 1,070 K and below, the deformation regime is controlled by dislocations. The samples show a more homogeneous grain size distribution, significant texture, and intracrystalline strains. In this regime, deformation is controlled by the ⟨110⟩{110} slip system and a combined ⟨110⟩{110} and ⟨110⟩{100} slip, depending on pressure and temperature.

Based on these results, we propose an updated deformation map for polycrystalline MgO at mantle conditions and discuss the implications for ferropericlase and seismic observations in the Earth’s lower mantle.

More details can be found in the open-access full reference of the study: E. E. Ledoux, F. Lin, L. Miyagi, A. Addad,  A. Fadel, D. Jacob, F. Béclin, and S. Merkel. Deformation of Polycrystalline MgO Up to 8.3 GPa and 1270 K: Microstructures, Dominant Slip-Systems, and Transition to Grain Boundary Sliding. Front. Earth Sci. 10, 849777 (2022) [doi: 10.3389/feart.2022.849777]

New publication in Physical Review Materials

4 May 2022 | Posted in Publications, TIMEleSS news

Deformation and slip systems of CaCl2-type MnO2 under high pressureWe have a new paper release ! On May 3rd, 2022, TIMEleSS student Matthias Krug, PI Carmen Sanchez-Valle, and PI Sébastien Merkel published a paper in Physical Review Materials, along with Binbin Yue and Fang Hong from the Center for High Pressure Science & Technology in Beijing, China.

The paper focuses on deformation in MnO2 and particularly its high pressure phase, in the CaCl2 structure. Why do we care about MnO2 ? MnO2 is not a deep Earth material, but it can be used as an analogue for SiO2 stishovite, which crystalizes in a rutile structure at low pressure and transform to a denser CaCl2 structure under high pressure. In SiO2, the stishovite to post-stishovite transformations occurs at ~ 50 GPa and is not always easily reached in deformation experiments. In MnO2, this same structural transition occurs at much lower pressure, around 4 GPa.

Our results show that, after phase transition to a CaCl2 structure above 3.5 GPa, the dominant (010)[100] and secondary {110}[001] and {011}[0-11] slip systems induce a 121 texture in compression. Further compression increases the activity of the {011}011 slip system, with an enhanced 001 texture at 50GPa. Finally, MnO2 transforms back to a rutile structure upon pressure release, with a significant orientation memory, highlighting the martensitic nature of the CaCl2 to rutile structural transformation. Overall, these results help us understanding plasticity and microstructures of CaCl2-structured dioxides, with implications in materials and Earth and planetary science.

The full reference for the study: B Yue, M. Krug, C. Sanchez-Valle, S. Merkel, and F. Hong, Deformation and slip systems of CaCl2-type MnO2 under high pressure, Phys. Rev. Mater., 6, 053603 (2022) [doi: 10.1103/PhysRevMaterials.6.053603]

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Partners

Partner institutions

Université de Lille CNRS   Westfälische Wilhelms-Universität Münster  Deutsche GeoForschungsZentrum

Participating laboratories

Unité Matériaux et Transformations, Université de Lille Institut für Geophysik, Universität Münster
Institut für Mineralogie, Universität Münster Chemistry and Physics of Earth Materials, GFZ

Funding bodies

 

Agence Nationale de la Recherche Deutsche Forschungsgemeinschaft  Projet financé par l'ANR