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SIMaP laboratory publishes scientific results in various peer-reviewed international journals. List of those papers and more can be found on the open archive HAL.

Scientific Reports:Nanostructured TiO2 anatase-rutile-carbon solid coating with visible light antimicrobial activity

TiO2 anatase-rutile-carbon - Scientific ReportsThe SIMaP laboratory established a partnership with Susan Krumdieck's team at the University of Canterbury (NZ) since 2015 when she was a Visiting Professor at the Phelma Engineering School . On this occasion, we began to explore the structural properties of a surprising TiO2-based black photocatalyst developed by pulsed CVD with photocatalytic properties in visible light and even an antimicrobial effect in the dark! Thanks to the equipment of the CMTC platform and the SIMaP searchers and staffs involved in this research, we were able to show that this material is an anatase-rutile-black amorphous carbon nanocomposite and to propose a growth mechanism by selective poisoning of crystalline surfaces. This material has all the benefits of TiO2 nanoparticles without the drawbacks: it is extremely adherent to surfaces, stable over time and non-friable, and is a pretty deep black. This material is considered as a coating in hospitals or as a fixed catalyst in pollution control applications.

Nanostructured TiO2 anatase-rutile-carbon solid coating with visible light antimicrobial activity.
S. P. Krumdieck, R. Boichot, R. Gorthy, J. G. Land, S. Lay, A. J. Gardecka, G. Renou, G. Berthomé, F. Charlot, T. Encinas, M. Braccini, M. I. J. Polson, A. Wasa, J. E. Aitken, J. A. Heinemann, J. V. Kennedy, C. M. Bishop.
Scientific Reports (SREP-18-32680) (2019) 9:1883. (https://www.nature.com/articles/s41598-018-38291-y)

Nature Communications:Frequency-tunable toughening in a polymer-metal-ceramic stack using an interfacial molecular nanolayer

Tunable toughness _ Nature CommunicationsComposites engineered at the nanometer-scale are of interest in a variety of applications including energy, electronics and biomedicine. The performance and reliability of such composites are often governed by the integrity of interfaces between dissimilar materials during loading fluctuations triggered by thermal, electrical and mechanical stimuli. Thus, unearthing and understanding nanoscale phenomena at interfaces during dynamic stimuli, and manipulating them, is a key to designing new materials with novel responses for applications. The work published in Nature Communications shows that the use of a layer of molecules called "nanoglue" can facilitate unexpected mechanical hardening depending on the frequency. These results obtained at the Rensselaer Polytechnic Institute are the result of a collaboration of researchers from different fields of materials science, to which Mr. Braccini, CNRS research fellow at the SIMaP laboratory, participated as part of a stay with Professor Ramanath's team.


Frequency-tunable toughening in a polymer-metal-ceramic stack using an interfacial molecular nanolayer
M. Kwan, M. Braccini, M. W. Lane, G. Ramanath
Nature Communications, 9(1), 5249. https://doi.org/10.1038/s41467-018-07614-y

Nature Materials: Surface distortion as a unifying concept and descriptor in oxygen reduction reaction electrocatalysis

Surface distorsion _ Nature MaterialsTuning the surface structure at the atomic level is of primary importance to simultaneously meet the electrocatalytic performance and stability criteria required for the development of low-temperature proton-exchange membrane fuel cells (PEMFCs). However, transposing the knowledge acquired on extended, model surfaces to practical nanomaterials remains highly challenging. Here, we propose ‘surface distortion’ as a novel structural descriptor, which is able to reconciliate and unify seemingly opposing notions and contradictory experimental observations in regards to the electrocatalytic oxygen reduction reaction (ORR) reactivity. Beyond its unifying character, we show that surface distortion is pivotal to rationalize the electrocatalytic properties of state-of-the-art of PtNi/C nanocatalysts with distinct atomic composition, size, shape and degree of surface defectiveness under a simulated PEMFC cathode environment. Our combined theoretical and experimental study brings fundamental and practical insights into the role of surface defects in electrocatalysis and highlights strategies to design more durable ORR nanocatalysts. This study has been selected to illustrated the front cover of Nature Materials volume published in July 2018.

Surface distortion as a unifying concept and descriptor in oxygen reduction reaction electrocatalysis
R. Chattot, O. Le Bacq, V. Beermann, S. Kühl, J. Herranz, S. Henning, L. Kühn, T. Asset, L. Guétaz, G. Renou, J. Drnec, P. Bordet, A. Pasturel, A. Eychmüller, T.J. Schmidt, P. Strasser, L. Dubau and F. Maillard
Nature Materials 17(2018) 827-833; doi: 10.1038/s41563-018-0133-2

Nature Communications: Direct measurement of individual phonon lifetimes in the clathrate compound Ba7.81Ge40.67Au5.33

A multi-partner study within the European C-MAC network has measured experimentally, for the first time, the phonon lifetime in a thermoelectric material clathrate renown for its very low ‘glass-like’ thermal conductivity, i.e., where phonons are expected experiencing a large amount of random collisions. This material contains Ge, Ba and Au atoms arranged periodically with a unit cell containing 54 atoms. The Ge and Au network form cages that enclose the Ba atoms. The team found surprisingly long mean-free-paths ranging from tens to hundreds of nanometers (1 nm=10-9 m). This is much larger than the short phonon mean free path of the order 0.5 nm that is commonly associated with such glass-like thermal conductivity. The study also demonstrates a large reduction of the number of phonon effectively carrying heat. Those results challenge current theoretical calculation and open the way for a new understanding of heat transport in complex materials.

Phonon distribution in clathermoelectric material clathrate
The background illustrates the periodic structure of the clathrate, with a unit cell (shown as a white square in the left with a parameter 1 nm. The Ba atoms in red are enclosed in the cages. The coloured curved are the inelastic neutron scattering measurements from which the dispersion reaction and the phonon lifetime has been extracted.
The decaying sinusoidal curve, illustrate the phonon propagation and its time decay (or lifetime) for a phonon wavelength equal to 2 nm.
 

Direct measurement of individual phonon lifetimes in the clathrate compound Ba7.81Ge40.67Au5.33,
P.-F. Lory, S. Pailhès et al., Nature Communications, 8: 491, 2017, DOI: 10.1038/s41467-017-00584-7
https://www.nature.com/articles/s41467-017-00584-7

Surprenante contradiction entre faible conductivité thermique des cristaux et longs temps de vie des phonons
published on the Institut National de Physique du CNRS website

Physical Review Letters: Band Filling Control of the Dzyaloshinskii-Moriya Interaction in Weakly Ferromagnetic Insulators

PhysRevLet_carbonatesAn international team of scientists have uncovered a surprisingly simple trend in the behaviour of 'twisted' magnets, which is precisely mirrored by first-principles calculations and explained by a simple microscopic model.

While the twisting of individual atomic-scale magnets is set to play a prominent role in future 'spintronics' technologies, the phenomenon was first discussed in detail in the context of 'weak ferromagnets' over half a century ago. It is precisely these materials that now offer a unique opportunity to investigate the effects of changing the magnetic atom type, since this causes almost no change in their structure.
Unfortunately, the direction of the magnetic twists cannot be observed by conventional techniques, since the two twist directions look the same. The researchers overcame this limitation by borrowing ideas from holography and applying them to x-ray 'diffraction', carried out at two of Europe's most powerful x-ray sources: Diamond Light Source in the UK and the European Synchrotron Radiation Source in France. The new technique gave a clear fingerprint of the twist direction, as the magnetic atoms gradually progressed along a row of the periodic table of elements. The results showed a sudden reversal of the twist, between manganese and iron, to the heavier cobalt and nickel atoms. Moreover, the jump is exactly as predicted by theory.
The team are hopeful that their results will bring new insights into an important class of material, and that their technique can be extended to other problems in solid state physics. The success of the computer simulations brings us a small step closer to goal of predicting the properties of technologically-important materials.

Band Filling Control of the Dzyaloshinskii-Moriya Interaction in Weakly Ferromagnetic Insulators, G. Beutier, S. P. Collins, O. V. Dimitrova, V. E. Dmitrienko, M. I. Katsnelson, Y. O. Kvashnin, A. I. Lichtenstein, V. V. Mazurenko, A. G. A. Nisbet, E. N. Ovchinnikova, and D. Pincini, Phys. Rev. Lett. 119, 167201, https://doi.org/10.1103/PhysRevLett.119.167201

Coatings journal front cover: Design of Experiments method: a fountain of Youth for CVD process.

CVD SIMaP (credit F. Mercier)We propose here to revisit a classical CVD process with a design of experiment approach to reveal that main parameters influencing the desired properties of an epitaxial layer, here AlN on sapphire, are not necessarily the one you expect. Simple DOE method can bring new insight into a well-established research and can make you go out of your intuition without any increase in experimental cost !
This work is published in Coatings and is enlighten in the front cover of 2017 September issue

Epitaxial Growth of AlN on (0001) Sapphire: Assessment of HVPE Process by a Design of Experiments Approach,
Raphaël Boichot, Danying Chen, Frédéric Mercier, Francis Baillet, Gaël Giusti, Thomas Coughlan, Mikhail Chubarov and Michel Pons, Coatings 2017, 7(9), 136; doi: Coatings 2017, 7(9), 136; doi:10.3390/coatings7090136

ESRF Spotlight: Fast in-situ nanoimaging of particle sintering

ESRF Spotlight Fast in situ imaging

Neck curvature, a parameter critical to the understanding of sintering, was determined precisely for the first time for the sintering of a glass powder. This was achieved by studying the microstructure evolution during sintering by high-temperature in-situ nanotomography using an unprecedented combination of fast scan time and high resolution. Those results are gathered in a paper in Materials Today journal and are also the subject of a ESRF' SPOTLIGHT ON SCIENCE.


Fast in situ 3D nanoimaging: a new tool for dynamic characterization in materials science, J. Villanova, R. Daudin, P. Lhuissier, D. Jauffrès, S. Lou, C.L. Martin, S. Labouré, R. Tucoulou, G. Martínez-Criado, L. Salvo, Materials Today (2017); doi: 10.1016/j.mattod.2017.06.0

Scientific Reports: From powders to bulk metallic glass composites.

Metallic glass composites

One way to adjust the properties of a material is by changing its microstructure. This concept is not easily applicable on bulk metallic glasses (BMGs), because they do not consist of grains or different phases and so their microstructure is very homogeneous. One obvious way to integrate inhomogeneities is to produce bulk metallic glass composites (BMGCs). Here we show how to generate BMGCs via high-pressure torsion (HPT) starting from powders (amorphous Zr-MG and crystalline Cu). This approach has been developed in partnership with the Erich Schmid Institute of Materials Science in Leoben, Austria, and demonstrated that by changing the applied shear strains, the refinement of the microstructure is adjustable. The refinement of microstructure increases the hardness and a hardness higher than the initial BMG can be obtained.

From powders to bulk metallic glass composites
Lisa Krämer, Yannick Champion, Rienhard Pipan, Scientific Reports (2017)
DOI:10.1038/s41598-017-06424-4

Date of update March 5, 2019

Univ. Grenoble Alpes