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Plasmonic Cu nanoparticles were in-situ grown into a Cu$_2$O semiconductor matrix by using reactive magnetron sputtering and adjusting the amount of oxygen available during the synthesis in order to prevent the oxidation of part of copper atoms landed on the film surface. Varying only the oxygen flowrate (OFR) and using a single Cu target it was possible to observe the evolution in the simultaneous formation of metallic Cu and Cu$_2$O phases for oxygen-poor conditions. Suchformation is accompanied by the development of the surface plasmon band (SPB) corresponding to Cu, as evidenced by UV-Vis spectrophotometry and spectroscopic ellipsometry. The bandgap values of the elaborated composites containing embedded Cu plasmonic nanodomains were lower than the bandgap of single-phased Cu$_2$O films, likely due to the higher defect density associated to the nanocrystalline nature of films, promoted by the presence of metallic Cu. The resistivity of the thin films increased with more oxidative deposition conditions and was associated to an increase in Cu$_2$O/Cu ratio and smaller and more isolated Cu particles, as evidenced by high resolution transmission electron microscopy and X-ray diffraction. Photoconversion devices based on the studied nanocomposites were characterized by I-V and spectral photocurrent measurements, showing an increase in the photocurrent density under light illumination as consequence of the plasmonic particles excitation leading to hot carrier's injection in the nearby ZnO and Cu$_2$O semiconductors., Comment: ACS Applied Electronic Materials, American Chemical Society, 2022

SnSe is semiconductor with various applications in optoelectronic devices, but its synthesis still facing challenges. Here, an original approach to tune the morphology, the optical properties and microstructure of SnSe films is proposed, based on the change of pulse duration during electrodeposition. The syntheses were carried out at a unique applied potential of −0.55 V vs AgCl/Ag with pulse durations (tON) ranging from 50 ms to 500 ms. The microstructure was systematically studied with SEM, TEM, XRD and XPS characterizations. First, the formation of SnSe of compact films without pinholes is demonstrated, with no significant change of composition (Se/Sn ratio close to 1:1). All the films are crystalized according to the Pnma orthorhombic phase with a preferential growth direction perpendicular to the (1 1 1) direction. The increase of pulse duration from 50 to 500 ms reduces the crystallinity of film, but less Se and SnO2 by-products are formed. Finally, the absorption coefficient of the films was extracted from ellipsometric measurements and evaluated in the near-edge region to evaluate the optical bandgaps. The results confirmed a slight change in the optical bandgap, from 1 to 1.1 eV. This work opens new alternative to tune physico-chemical properties of SnSe films.

International audience; Mo-based cluster compounds form a large class of materials with interesting thermoelectric properties primarily due to their very low lattice thermal conductivity. Here, we investigate the influence of the insertion of Cu on the crystal structures and thermoelectric properties of the ternaries In2Mo15Se19 and K2Mo15Se19. Inserting Cu+ cations into the intercluster voids of the rhombohedral lattice enables adjusting the hole concentration, resulting in higher thermopower values with respect to the Cu-free compounds. While Cu+ cations occupy a single crystallographic site in Cu3In2Mo15Se19 as in the Ag-containing analogues, a distinctive crystallographic feature of Cu3K2Mo15Se19 is the different distribution of these cations that reside on split positions. The high degree of structural disorder of these compounds gives rise to very low lattice thermal conductivity kL, which directly depends on the total concentration of inserted cations. The sensitivity of the electronic and thermal properties to the Cu content is evidenced by a Cu-rich sample with nominal composition Cu4In2Mo15Se19 that exhibits enhanced power factor and reduced kL, yielding a peak ZT value of similar to 0.42 at 1145 K. The good thermoelectric performance and high melting point of these compounds make them potential candidates for thermoelectric applications above 1000 K.

Spintronics is showing promising results in the search for new materials and effects to reduce energy consumption in information technology. Among these materials, ferrimagnets are of special interest, since they can produce large spin currents that trigger the magnetization dynamics of adjacent layers or even their own magnetization. Here, we present a study of the generation of spin current by GdFeCo in a GdFeCo/Cu/NiFe trilayer where the FeCo sublattice magnetization is dominant at room temperature. Magnetic properties such as the saturation magnetization are deduced from magnetometry measurements while damping constant is estimated from spin-torque ferromagnetic resonance (ST-FMR). We show that the overall damping-like (DL) and field-like (FL) effective fields as well as the associated spin Hall angles can be reliably obtained by performing the dependence of ST-FMR by an added dc current. The sum of the spin Hall angles for both the spin Hall effect (SHE) and the spin anomalous Hall effect (SAHE) symmetries are: $\theta_{DL}^{SAHE} + \theta_{DL}^{SHE}=-0.15 \pm 0.05$ and $\theta_{FL}^{SAHE} + \theta_{FL}^{SHE}=0.026 \pm 0.005$. From the symmetry of ST-FMR signals we find that $\theta_{DL}^{SHE}$ is positive and dominated by the negative $\theta_{DL}^{SAHE}$. The present study paves the way for tuning the different symmetries in spin conversion in highly efficient ferrimagnetic systems., Comment: 20 pages, 4 figures

A joint experimental and theoretical study is presented to reveal the influence of nitrogen doping on the optical and electrical properties of NiO thin films. Nitrogen addition can significantly enhance the subgap absorption. The molecular state of nitrogen (N

Designing and manufacturing multifunctional nanoparticles (NPs) are of considerable interest for both academic and industrial research. Among NPs used in this field, iron oxide NPs show low toxicity compared to metallic ones and are thus of high interest for biomedical applications. In this work, superparamagnetic Fe3−δO4-based core/shell NPs were successfully prepared and characterized by the combination of different techniques, and their physical properties were investigated. We demonstrate the efficiency of the layer-by-layer process to graft polyelectrolytes on the surface of iron oxide NPs. The influence of the polyelectrolyte chain configuration on the magnetic properties of the Fe3−δO4/polymer core/shell NPs was enlightened. The simple and fast process described in this work is efficient for the grafting of polyelectrolytes from surfaces, and thus, derived Fe3−δO4 NPs display both the physical properties of the core and of the macromolecular shell. Finally, the cytotoxicity toward the human THP-1 monocytic cell line of the core/shell NPs was assessed. The results showed that the polymer-capped Fe3−δO4 NPs exhibited almost no toxicity after 24 h of exposure at concentrations up to 25 μg mL–1. Our results show that these smart superparamagnetic nanocarriers with stealth properties are promising for applications in multimodal cancer therapy, including drug delivery.

7 Figuras, 2 Tablas, Mesoporous carbons containing up to 3.6 at.% N and 4.4 at.% O and exhibiting graphitic character have been prepared from Ni(II) and Fe(II) phthalocyanines by direct pyrolysis or by HTC + pyrolysis, and subsequently applied as supercapacitor materials. No mesoporous templates or doping post-treatments were used, and the catalytic effect of Ni(II) and Fe(II), naturally present in the precursor molecules, allowed obtaining graphitic carbons at temperatures ≤ 900 °C. Metals were encapsulated in the core of onion–like structures with no contact with the electrolyte, so that electrodes were prevented from degradation during device operation. The materials exhibited high rate capabilities up to 1 V s−1, higher interfacial capacitances than a wide variety of materials possessing higher surface areas, and high capacitance retentions up to 99% at 5 A g−1 current density throughout 10 000 charge–discharge cycles. The electrochemical performances of the phthalocyanine-derived carbons are due to their graphitic character and to the pseudocapacitance contribution of the surface groups through Faradaic reactions. This work opens a new way to obtain carbon materials from a great family of metal phthalocyanines, since the central metal and the radicals of the latter can be varied to tune the carbon properties for specific applications., The IJL research team gratefully acknowledges the Dr. Marta Sevilla’s departement for its scientific support, and the financial support of the CPER 2007-2013 “Structuration du Pôle de Compétitivité Fibres Grand’Est” (Competitiveness Fibre Cluster), through local (Conseil Général des Vosges), regional (Région Lorraine), national (DRRT and FNADT) and European (FEDER) funds. Dr. A. Sanchez-Sanchez acknowledges the CNRS for financing her post-Doctoral contract.

The preparation of well-defined organo-mineral assemblies under controlled conditions is required to improve our understanding of the formation and surface reactivity of micrometric aggregates, ubiquitous in soils and continental aquatic media. We aim at investigating the building of organo-mineral assemblies with a specific focus on the assembly mode and its consequence on the final properties of the micrometric aggregates. In this work, the preparation and detailed characterization of clay-size aggregates composed of a clay mineral (illite), organic polymer (Dextran polysaccharide) and iron (hydr)oxide are reported, with a focus on the structural organization of the generated aggregates. A step-by-step strategy was developed, and three sets of clay-size composites were prepared with illite particles as a starting material. In two first steps, two distinct sets of two-component composites were obtained according to different procedures. Illite‑iron (hydr)oxide composites were obtained by alkaline hydrolysis of iron in the presence of illite particles, and illite-Dextran aggregates were obtained through the addition of Dextran polysaccharide to an illite suspension. In a third step, three-component micro-aggregates were obtained by subsequent addition of Dextran to suspensions containing the formed illite‑iron (hydr)oxide composite. The so-prepared 2- and 3- component aggregates were investigated by electrophoresis, electron microscopy, X-ray absorption and FTIR spectroscopies. For materials containing Dextran, electrophoretic mobility measurements evidenced variations of surface charge, combined with an increase of aggregate size highlighted by dynamic light scattering. Electron microscopy and EXAFS at iron K-edge evidenced the precipitation of nanoparticles of iron (hydr)oxide onto clay mineral surfaces. FTIR data in transmission and diffuse reflectance modes supported not only the adsorption of Dextran but also the preferential localization of Dextran at the external surfaces of the aggregates. All in all, data collected on the two- and three-component materials demonstrated that the presence of iron (hydr)oxide nanoparticles on the surface of illite strongly modified the organization of organic and mineral constituents.

A new ternary phase with a composition Al1+xV2Sn2–x (x = 0.19) has been found during investigation of the Al–V–Sn ternary system. Single-crystal X-ray diffraction measurements reveal that this ternary phase crystallizes with an orthorhombic structure with a = 5.5931(1) A, b = 18.8017(5) A, and c = 6.7005(2) A (space group Cmce). This compound is thus isostructural to the GaV2Sn2 structure type, showing a layered structure composed of vanadium cluster bands formed with pentagonal faces intercalated by Sn atom layers. High-resolution transmission electron microscopy measurements confirm the orthorhombic structure. Regarding lattice perfection, no dislocation could be identified within the probed Al1.19V2Sn1.81 single-crystal lamella. Ab initio calculations reveal a reduction of the density of states at the Fermi level, which could be attributed to both a Hume–Rothery effect combined with strong spd hybridization.

A 5 nm thick ferrimagnetic film made of amorphous rare-earth transition-metal alloys Gdx(Fe90Co10)1-x was grown by physical vapor deposition. Its magnetic properties (coercivity, perpendicular magnetic anisotropy, and compensation composition at room temperature) were investigated for various buffer and capping layers in contact with a ferrimagnetic thin film. While Gdx(Fe90Co10)1-x appears to be amorphous for all the samples, it appears that (111) textured Cu is the best material to promote perpendicular magnetization. The large compensation composition change as a function of the magnetic film interface at room temperature is analyzed in terms of polarizability of the surrounding buffer and capping materials.

International audience; Zinc tin nitride (ZnSnN2) is a promising semiconductor candidate for solar cell applications and optoelectronic devices. However, the practical use of this material has been limited by several issues as, among others, oxygen contamination, a very high concentration of free carriers and the difficulty to reach the theoretically predicted band gap. Here, we deposit thin films of ZnSnN2 by reactive DC magnetron co-sputtering at room temperature with a RF bias power (Pb) in the range of 0-50 W. Using first principle calculations, we explore the structural and opto-electronic properties that are favorably compared to experimental results. We demonstrate that the optical band gap energy can be decreased from 1.7 eV to 1.34 eV, close to the predicted value of 1.37 eV. The free electron concentration is decreased down to 10 17 cm-3 which results in the reduction of the absorption by free electrons in the IR range. In addition, in a given range of applied bias powers, we observe a densification of the films and a significant decrease of their oxygen contamination from 6.7 down to 2.0 at. %. The study underlines that a value of 20 W power bias leads to the optimal structural, optical and electrical properties. Our results provide an interesting method to obtain a potential candidate for photovoltaic applications, in an environmental friendly way, for a low-cost industrialization.

MgSnN2 thin films were deposited by reactive magnetron co-sputtering on fused silica and silicon substrates. The properties of the films were determined as a function of the deposition temperature. Although the films exhibited a strong preferred orientation along the [002] direction, cumulative X-ray diffractograms at various χ angles evidenced that the deposited films crystallized in a wurtzite-like structure. Regardless of the substrate temperature during deposition, MgSnN2 films had a columnar microstructure. Mössbauer spectrometry and X-ray photoemission spectroscopy were used to extract the chemical environment of magnesium and tin atoms and to identify their oxidation states. Electrical properties were deduced from Hall effect measurements. An increase of the electron mobility was noticed at high deposition temperature. The optical band gap of MgSnN2 films increased from approx. 2.28 to 2.43 eV in the 300–500 °C range. The experimental optical properties of MgSnN2 films were compared to those obtained by ab initio calculations.

Present study focuses on crystal violet adsorption by mineral halloysite and synthetic pecoraite nanoscrolls. Being scrolled in opposite directions, these two materials serve both as good adsorbents and model objects to understand the dye adsorption mechanism. Heat treatment of the nanoscrolls allowed us to track the adsorption process features by changing the structure and surface state of the particles. Structural transitions were observed by complementary techniques including X-ray diffraction, thermal analysis, electron microscopy, N2 adsorption and ς-potential measurements. By a fast UV/VIS study of adsorption kinetics, it became possible to take a closer look at the very initial steps of the process. Intraparticle diffusion governs the overall adsorption kinetics of the dye by halloysite and pecoraite nanoscrolls. The presence of OH-groups on the nanoscrolls' surface strongly facilitates the initial stage of adsorption. Structural transition at around 600 °C increases adsorption rate and performance of synthetic pecoraite due to ς-potential sign change.

Nanosecond-pulsed spark discharge between two lead electrodes in liquid nitrogen has been used to synthesize hexagonal lead nanosheets. These original nanostructures are collected on a substrate located under the electrodes. After the full evaporation of the liquid nitrogen, the nanosheets are oxidized in air and transform into a lead dioxide. The resulting hexagonal sheets have typical widths of around 1 µm and typical thicknesses of around 10 nm. Investigations by energy dispersive spectroscopy microanalysis, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy and electron microdiffraction were performed in order to identify the crystal structure in which these hexagonal nanosheets crystallize. An analysis of the chemical composition pointed to a stoichiometric lead dioxide, PbO2. This PbO2lead dioxide crystallizes in the hexagonal system (a= 0.912 nm andc= 1.265 nm) and belongs to the space groupP6/m2/m2/m. On the basis of group theory (symmetry analysis), the nanosheets develop a hexagonal-prismatic shape in liquid nitrogen, assumed to be an isotropic medium. From the energetic point of view, this shape, dictated by the 6/m2/m2/mpoint group, corresponds to an absolute extremum, an indicator of the stability of this lead dioxide. A mechanism similar to that of the ledge mechanism explaining the formation of thin plates in a metallic matrix has been adapted and proposed for the formation of the lead nanosheets in the liquid nitrogen. When the liquid nitrogen is removed, the lead nanosheet is oxidized, leading to a lead dioxide, inheriting the nanosheet morphology. As far as the authors are aware, this is the first time that such a lead dioxide has been synthesized by spark discharge in liquid nitrogen followed by oxidation in air. The crystallographic structure is determined and the morphology is explained. A mechanism for the development of the lead nanosheets and their oxidation is proposed. This hexagonal phase, designated γ-PbO2, is thought to be the third polymorph after the α-PbO2and β-PbO2phases of lead dioxide, the former being orthorhombic and the latter being tetragonal.

The epitaxy of MoO2 on c-plane sapphire substrates is examined. A theoretical approach, based on density functional theory calculations of the strain energy, allowed to predict the preferred layer/substrate epitaxial relationships. To test the results of these calculations, MoO2/(0 0 1) Al2O3 heterostructures were grown using the chemically-driven isothermal close space vapour transport technique. At the early stages of the growth, two kinds of morphologies were obtained, using the same growth parameters: lying and standing flakes. The composition and morphology, as well as the layer/substrate epitaxial relationships were determined for both kind of morphologies. Experimental epitaxial relationships coincide with those predicted by DFT calculation as the most favourable ones in terms of strain energy. For thicker films, the standing flakes evolve to form an epitaxial porous layer composed by coalesced epitaxial flakes. The interfacial strain between the sapphire substrate and MoO2 enables a self-organization from nanometer to micron scales between separated or coalesced flakes, depending on deposition condition, OdM, OC, DH and YG gratefully acknowledge the support from the program ‘‘Cátedras de Excelencia de la Comunidad de Madrid (2016- T3/IND-1428)”

The (110) and (320) surfaces of the single-phase FeCrMnNiCo solid solution have been studied on two adjacent millimeter size grains using surface science and transmission electron microscopy (TEM) techniques. The structural and chemical evolutions of the high entropy alloy (HEA) surfaces have been determined for various sputtering conditions, annealing temperatures and durations. Up to 873 K, angle-resolved X-ray photoelectron spectroscopy measurements indicate a clear Mn and Ni surface co-segregation. We propose that the surface segregation of Mn is driven by its low surface energy. The attractive interaction between Mn and Ni promotes Ni segregation which accompanied the Mn diffusion to the surface. Regarding the structures investigated by low energy electron diffraction and scanning tunneling microscopy, the (320) surface presents a terraced morphology with an ordered structure consistent with a ( 1 × 1 ) termination. On the contrary, the (110) surface reveals an important degree of structural disorder and local reconstructions. Its highly anisotropic morphology resembles rows propagating along the [001] direction. Above 873 K, Mn desorption occurs while the Ni content keeps increasing linearly with the temperature. TEM analysis show no evidence for HEA decomposition into metallic or intermetallic phases even after repeated annealing and sputtering cycles. The above results set the upper temperature limit above which the surface stoichiometry departs from the quinary HEA concept. It also defines the temperature range for the use of FeCrMnNiCo based coating under high vacuum conditions and for aerospace applications.

Forest soils are a major contributor to soil organic carbon (C) storage in terrestrial ecosystems and play a key-role in climate change mitigation. Mineral weathering in soils is expected to promote chemical and physical interactions between soil organic matter and mineral phases. These interactions are known to enhance the protection of organic matter from decomposition. The investigation of the mineral-organic associations (MOA) formation mechanisms during weathering is therefore crucial to understand carbon storage processes in soils. Until now studies have been mainly conducted through laboratory experiments in simplified and controlled conditions or over very long-term time scales using pedosequences. But knowledge about MOA formation processes occurring in situ is lacking, notably during the first stage of mineral weathering.To fill this gap, we performed a mesh bag incubation of large Na-saturated vermiculite particles (100-200 µm in size) in a Typic Dystrochrept soil of a Douglas-fir forest, in the Beaujolais area (France). The incubated particles were deposited at the interface under the forest floor. After 20 years, the weathered vermiculite particles were collected and characterized at the macro-scale (XRD and physico-chemical analysis), at the micro-scale (Scanning Electron Microscopy – SEM, imaging and element mapping) and at the nano-scale (Transmission Electron Microscopy - TEM imaging, element mapping and speciation).Cation exchange capacity, exchangeable cations and elemental analysis showed significant differences between the mineral structures of the initial (V0) and 20 year incubated (V20) vermiculite particles. The exchangeable Na was completely depleted. Cation exchange capacity strongly decreased in V20 (49.2 cmolc kg-1) compared to V0 (173.6 cmolc kg-1). The V20 lost its specific interlayer collapsing property (≈1.4 -> ≈1.0 nm) with K saturation. V20 interlayer collapsing was only observed with a 330°C heating treatment, suggesting the interlayer hydroxylation of vermiculite. High sheet dissolution, around 10%, was also observed. All these changes were attributed to chemical weathering, during which total C analysis showed significant enrichment in V20 (5.7 mg g-1) compared to V0 (0.8 mg g-1).Macro, micro and nano-scale images and elemental mapping of V0 particles showed a highly flat, smooth surface morphology with no detected C. In contrast, V20 particles showed irregular outer and inner surfaces marked by multiple cracks of chemical dissolution. We also observed internal nano-sized exfoliation spaces filled with C and enriched in Ca, and micro-sized exfoliation spaces filled with C entrapped in nano-crystalline Mn oxides or K-rich aluminosilicates precipitates. The nature of the organic matter found strongly differed between small and large exfoliation spaces. It was characterized by alcohol, carboxyl functional groups and C=C bonds in small exfoliation spaces, while the obtained EELS spectra were more difficult to interpret in large exfoliations spaces. These results provide new evidence that over 20 years in situ weathering induces a significant dissolution, among other physical and chemical changes in large vermiculite particles. They reveal that the mineral weathering processes are responsible for the organic matter entrapment (i) in the newly formed mineral nano-sized spaces, possibly mediated by Ca, and (ii) in association with secondary minerals deposits in micro-sized spaces.

International audience; The control of complex nanostructures is one of the most promising strategy to design tailored properties materials. Composites are often good candidates, especially with complex phases. MAX phases have remarkable properties such as low density, high modulus, good metallic conductivity, self-lubrication properties and unique mechanical behaviors both at room and high temperatures.Copper is one of the most used metals essentially because of its very high electrical conductivity. However, its low strength and its low wear resistance properties result in premature failure of components, thus restricting its wide range of applications, particularly in homopolar machines and in overhead current lines for railway. One possible route for overtaking these obstacles is to introduce into a Cu matrix, layered ternary MAX phases, such as Ti2AlC.Here we report the comprehensive description of the diffusion mechanisms of Cu-matrix elements in Ti2AlC-MAX phase interlayers by means of high-resolution electron microscopy and atomic-scale simulations. In particular, we demonstrate the formation of Ti2C platelets and evidenced Frank partial dislocations that are not expected to be found in such material. These defects have an extensive impact on the properties of the composite as they can largely improve mechanical responses and molecule segregation.

Batteryless, wireless, and packageless acoustic wave sensors are particularly desirable for harsh high-temperature environments. In this letter, an acoustic wave sensor based on a lithium niobate (Y + 128° cut, abbreviated LN-Y128) substrate with a buried platinum interdigital transducer (IDT) in an aluminum nitride (AlN) overlayer is investigated. Previously, it was demonstrated theoretically that due to the specific properties of LN-Y128, Rayleigh-type guided waves can propagate at the AlN/IDT(Pt)/LN-Y128 interface. Here, this structure is, for the first time, studied experimentally, including the growth and properties of the AlN layer onto irregular platinum IDTs. Both Shear Horizontal and Rayleigh-type waves have been identified after the AlN deposition and the velocities are consistent with the fitted SDA-FEM-SDA (a combination of finite element modeling with spectral domain analysis) simulations. Electrical measurements with a surface perturbation and temperature measurements show that the AlN/IDT(Pt)/LN-Y128 bilayer structure is promising as a packageless high-temperature sensor.

In Agadir, a water-scarce Moroccan region, municipal and industrial wastewater is tertiary-treated to be reused in golf courses. Wastewater reuse has been constrained by severe clogging of emitters, which caused technical and financial problems. This study aimed to perform an in-depth characterization of the treated wastewater (TWW) in relation to its susceptibility to cause clogging, and to assess the capacity of an aeration post-treatment to reduce the clogging potential. The post-treatment consisted of injecting different airflows (0–33 L/(h Lreactor) into the TWW. The structural, morphological and elemental composition of the clogging matter collected in the irrigation pipeline was characterized using scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction and X-ray energy dispersive spectroscopy. The 15-day aeration post-treatment at 16.5 L/(h Lreactor) presented the best cost–benefit ratio. Organic matter was totally degraded. Calcium was reduced by 9%, bicarbonates by 54%. The analysis of the deposits induced by the aeration post-treatment revealed a relevant decrease of the major constituents of the clogging deposits found in the irrigation pipeline. The results show the effectiveness of post-aeration in biodegrading residual organic matter and precipitating several salts, thus reducing the clogging potential.

Spintronics exploits spin-orbit coupling (SOC) to generate spin currents, spin torques, and, in the absence of inversion symmetry, Rashba, and Dzyaloshinskii-Moriya interactions (DMI). The widely used magnetic materials, based on 3d metals such as Fe and Co, possess a small SOC. To circumvent this shortcoming, the common practice has been to utilize the large SOC of nonmagnetic layers of 5d heavy metals (HMs), such as Pt, to generate spin currents by Spin Hall Effect (SHE) and, in turn, exert spin torques on the magnetic layers. Here, we introduce a new class of material architectures, excluding nonmagnetic 5d HMs, for high-performance spintronics operations. We demonstrate very strong current-induced torques exerted on single GdFeCo layers due to the combination of large SOC of the Gd 5d states, and inversion symmetry breaking mainly engineered by interfaces. These "self-torques" are enhanced around the magnetization compensation temperature (close to room temperature) and can be tuned by adjusting the spin absorption outside the GdFeCo layer. In other measurements, we determine the very large emission of spin current from GdFeCo. This material platform opens new perspectives to exert "self-torques" on single magnetic layers as well as to generate spin currents from a magnetic layer., Comment: 26 pages, 4 figures plus 5 pages of sup. information

International audience; We report on the crystal structure and physical properties of Tl0.6Mo3S5, which belongs to a novel family of materials with large tunnels, reminiscent of those observed in the romanechite structure type. Tl cations are partially filling these tunnels delimited by the Mo-S cluster framework in which the Mo atoms form infinite zigzag chains. Single-crystal X-ray diffraction data indicate that this compound crystallizes in the monoclinic, non-centrosymmetric space group P21 (no. 4; a = 9.344(2) angstrom, b = 3.234(2) A, c = 11.669(2) A and beta = 113.09(2)° at 293 K). While electron diffraction performed on single crystals further evidences a commensurate modulation running solely along the b axis with a modulation wave vector further experiments carried out on a polycrystalline sample suggest a compositional dependence of q on the Tl content. Low-temperature transport properties measurements (5-300 K) reveal that Tl0.6Mo3S5 behaves as a narrow-band-gap n-type semiconductor. The strongly non-linear temperature dependence of the thermopower further suggests the presence of several electronic bands contributing to the electrical transport. Consistent with the extended electronic distribution in the tunnels that requires a description using two adjacent Tl sites, specific heat data measured down to 0.35 K evidence the presence of a Schottky-type anomaly that may be associated with the tunneling of the Tl cations between several equivalent, off-centered equilibrium sites. This inherent disorder contributes to suppression of the low-temperature Umklapp peak in the lattice thermal conductivity kL, the temperature dependence of which mimics that observed in strongly-disordered compounds. In spite of this characteristic, high kL values of up to 3.8 W m-1K-1 are reached at 300 K, due to the covalent Mo-S network that contributes to maintaining high sound velocities.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 05/11/2021 Here we report on the thermal properties of Mg−Ni‐phyllosilicate nanoscrolls as a promising precursor for production of Ni/silicate composite catalysts. Spontaneous scrolling of the phyllosilicate layer originating from size difference between metal‐oxygen and silica sheets provides high surface area of the catalyst. Metal nanoparticles can be obtained directly from the matrix by H2 reduction. The phyllosilicate structure passed through a number of transformations including partial dehydroxylation with formation of sepiolite‐like phase followed by silicate or oxide crystallization. Temperature ranges of these transitions overlapped with the reduction process sophisticating the H2 consumption profiles. In particular, some amount of Ni2+ got sealed up by the sepiolite structural features, that opened a path for the tuning of Ni0 : Ni2+ ratio of the catalyst. An increase of Ni content in the system yielded a decrease in the metal nanoparticles sizes due to both high intensity of nucleation and type of residual matrix. Ni nanoparticles size distribution and specific surface area of the composite catalysts governed conversion rate of hexene‐1 and acetone hydrogenation. In the view of the turnover frequency MgNi2Si2O5(OH)4 precursors were slightly more preferable than pure Ni3Si2O5(OH)4.

We report the adsorption of Fe for several dosing conditions on Al(1 0 0) surface held at different temperatures. For 2 monolayer equivalent of Fe deposited on the substrate held at 593 K, we observe two rotational domains of a ( 5 × 5 )R26.6° structure by low energy electron diffraction and scanning tunneling microscopy. We identify this structure as the formation of the metastable Al9Fe2 intermetallic phase. The segregation energy and the structural stability of this intermetallic has been analysed using density functional theory based calculations. We propose that the formation of the Al9Fe2(0 0 1) metastable phase at the expense of other thermodynamically stable Al-Fe compounds, relies on a specific structural similarity between pure Al (0 0 1) planes of the intermetallic and Al(1 0 0) layers. These ‘common’ planes lead to the epitaxial relationship (1 0 0)Al [0 0 1]Al ∥ ( 0 0 1 ) Al 9 Fe 2 [ 1 3 ¯ 0 ] Al 9 Fe 2 . The Al9Fe2-Al matrix interface is sharp as revealed by transmission electron microscopy measurements.

International audience; An Al-Zr (4 at.% Zr) film is deposited on High Speed Steel substrates by pulsed Direct Current magnetron sputtering in order to provide sacrificial corrosion resistance of steel. A TiO2 layer is synthesized on the top by aerosol-assisted metal-organic chemical Vapour Deposition (AA-MOCVD) in order to insure anti-biofouling behaviour. TiO2 coating has a typical CVD microstructure and the film is anatase single phased. The as-deposited Al-Zr film is an extended supersaturated solid solution Al(Zr) of Zr in Al. The AA-MOCVD process is performed at 773 K for 40 min. This annealing leads to a fine precipitation of highly coherent metastable Al3Zr(L12) phase in the Al(Zr) matrix. Larger precipitates with a needle like morphology, which crystallize in the equilibrium tetragonal Al3Zr(D023) phase are also observed. Transmission electron microscopy analysis clearly shows the cube on cube orientation between Al3Zr(L12) phase and Al(Zr) matrix. As the cubic Al3Zr(L12) metastable phase is beneficial for the mechanical properties of bulk aluminium based alloys, this result opens the investigation field on Al-Zr coatings, which can provide sacrificial protection of steels.

We report on the epitaxial growth of ${\mathrm{PrVO}}_{3}$ and ${\mathrm{LaVO}}_{3}$ by molecular beam epitaxy on (001)-oriented ${\mathrm{SrTiO}}_{3}$ substrates. We show that a high control of the deposition is achieved and leads to a highly reproducible layer-by-layer growth mode. We evidence also the effect of epitaxial strain on the magnetic properties of the epitaxial films. High-resolution transmission electron microscopy and scanning transmission electron microscopy observations reveal that an antipolar motion of the rare-earth atoms exists in both ${\mathrm{LaVO}}_{3}$ and ${\mathrm{PrVO}}_{3}$ thin films. The investigation of the structural distortions and atomic displacements in the vanadate thin films may be generalized to other orthorhombic perovskite oxides and contributes to the search of ferroelectricity by design in symmetry-breaking magnetic oxide superlattices.

High-quality graphene is an especially promising carbon nanomaterial for developing nanofluids for enhancing heat transfer in fluid circulation systems. We report a complete study on few layer graphene (FLG) based nanofluids, including FLG synthesis, FLG-based nanofluid preparation, and their thermal conductivity. The FLG sample is synthesized by an original mechanical exfoliation method. The morphological and structural characterization are investigated by both scanning and transmission electron microscopy and Raman spectroscopy. The chosen two-step method involves the use of thee nonionic surfactants (Triton X-100, Pluronic&reg, P123, and Gum Arabic), a commercial mixture of water and propylene glycol and a mass content in FLG from 0.05 to 0.5%. The thermal conductivity measurements of the three FLG-based nanofluid series are carried out in the temperature range 283.15&ndash, 323.15 K by the transient hot-wire method. From a modeling analysis of the nanofluid thermal conductivity behavior, it is finally shown that synergetic effects of FLG nanosheet size and thermal resistance at the FLG interface both have significant impact on the evidenced thermal conductivity enhancement.

The competition between charge density wave (CDW) and superconductivity is a central theme in condensed-matter physics with ramifications to correlated electron systems and high-temperature superconductivity. While the emergence of superconductivity is often observed upon suppressing the CDW transition by tuning the chemical composition or the external pressure, their coexistence has been reported in only a handful of materials, with the cuprates being the most prominent example. Here, we demonstrate that both cooperative electronic phenomena coexist in the cluster compound ${\mathrm{K}}_{2}\mathrm{M}{\mathrm{o}}_{15}\mathrm{S}{\mathrm{e}}_{19}$. The CDW transition sets in at ${T}_{\mathrm{CDW}}=\phantom{\rule{0.16em}{0ex}}114\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, accompanied by a commensurate periodic modulation of the crystal lattice along the $c$ axis evidenced by electron diffraction. Bulk type-II superconductivity develops upon further cooling below ${T}_{c}=\phantom{\rule{0.16em}{0ex}}2.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The presence of similar signatures of CDW ordering in other ${\mathrm{A}}_{2}\mathrm{M}{\mathrm{o}}_{15}\mathrm{S}{\mathrm{e}}_{19}$ compounds shows that this electronic instability may be ubiquitous in these compounds, providing a novel family where the interplay between CDW and superconductivity may be systematically investigated.