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The thermal stability of Cu/W nano-multilayers deposited on a Si substrate using ion beam deposition was analyzed in situ by GISAXS and transmission EDX—a combination of methods permitting the observation of diffusion processes within buried layers. Further supporting techniques such as XRR, TEM, WAXS, and AFM were employed to develop an extensive microstructural understanding of the multilayer before and during heating. It was found that the pronounced in-plane compressive residual stress and defect population induced by ion beam deposition result in low thermal stability driven by thermally activated self-interstitial and vacancy diffusion, ultimately leading to complete degradation of the layered structure at moderate temperatures. The formation of Cu protrusions was observed, and a model was formulated for stress-assisted Cu diffusion driven by Coble creep along W grain boundaries, along with the interaction with Si substrate, which showed excellent agreement with the observed experimental data. The model provided the explanation for the experimentally observed strong correlation between thin film deposition conditions, microstructural properties, and low thermal stability that can be applied to other multilayer systems.

International audience; This topical review covers the mechanical properties of natural fiber composites (NFCs) that allow applications in many application fields ranging from infrastructure to transportation. Climate change alerts on the importance of sustainability and NFCs offer opportunities when compared to conventional glass-fiber composites. Advantages and drawbacks of NFC versus synthetic composites are considered and discussed. Mechanical properties are assessed both statically and dynamically. The hydrophilicity and its consequences on damage and deformation mechanisms are also addressed. The key to making well-reinforced composites is by ensuring that there is a strong interface between the reinforcing phase and the matrix phase. The interfacial bonding quality is thus discussed through various testing methods and the effects of surface treatments are presented.

When thin metallic multilayers deposited on a compliant polymer substrate are subjected to stretching, a “brick wall” fracture pattern arises that is associated with a non-uniform two-dimensional stress-strain state evolving as a function of the underlying substrate stretch. The present study is devoted to in situ mechanical microscopy of strain states in a copper/tungsten 18/6 nm multilayer using the combination of synchrotron Scanning X-Ray Diffraction Microscopy (SXDM) and Scanning Electron Microscopy (SEM), coupled with Digital Image Correlation (DIC). We demonstrate that these methods allow spatial variation of the coating strain to be mapped and compared with theoretical predictions based on shear lag theory, allowing the fracture properties of the multilayer to be extracted.

A novel experimental approach to study the cyclic plastic deformation of thin metallic films is presented. 300 nm thick Ni films are deposited on both sides of a pre-tensile soft substrate which allows to deform the films alternately in tension and compression (approximately from +2.7 GPa down to −2 GPa) relative to the as-deposited residual stress state. Nanocrystalline thin films' intrinsic elastic strains (or stresses) and true strains have been measured step by step during two loading/unloading cycles thanks to the X-ray diffraction (XRD) and digital image correlation (DIC) techniques respectively. From the first cyclic deformation, a significant Bauschinger effect is evidenced in the films, however, little or no cyclic hardening is observed during the two cyclic tests.

Instrumented Indentation Testing is applied on a fluoroelastomer so as to get information about the local mechanical response of such a rubbery material. Due to their viscoelasticity, elastomers exhibit a time-dependence, responsible for a variation in their behavior as a function of the stress or strain rate. A few studies highlight modifications of the indentation hardness H and modulus E r when the load function varies. However, these works concern polymers and, to our knowledge, such an investigation has not yet been carried out on elastomeric materials. Results about the influence of the loading-unloading procedure on E r are presented here. They show elastic modulus' variations depending on the chosen protocol's time scale and reported evolutions are consistent with the expected behavior of viscoelastic materials. Furthermore, in preparation of this main study, preliminary verifications were necessary since sources of error are known to distort indentation results. A focus on the microstructure and roughness is presented in this paper and reveals, in particular, a non-negligible improvement of indentation curves (load-displacement hystereses) with an appropriate sample preparation and surface finish. These results have finally been used as a basis for the study of local gradients within a rubber sample. This study revealed a gradient (i.e. an increasing modulus) from the outer part of the sample to the inner one, attributed to thermal effects during the molding.

Residual stresses in thin films and multi-layered coatings fabricated by physical vapour deposition largely affect their mechanical and thermal reliability during operation in numerous fields of applications. By changing the argon working pressure in between each multilayer planar DC magnetron sputter deposition step, it is possible to control the residual stress distribution within coatings. A combination of FIB-DIC ring-core strain analysis, synchrotron XRD analysis based on the sin2(Ψ) method and micro-cantilever deflection analysis is used to reconstruct the in-plane stress state of multilayer coatings at different deposition pressures, with a residual stress depth profile resolution of 50 nm. A clear transition from compressive to tensile residual stresses is observed with an increase of working pressure, with pronounced stress peaks near the substrate-coating interface. These peak stresses resolved by FIB-DIC ring-core analysis exceed the average XRD stress measurements significantly, thus providing a reasonable explanation for multilayer failure. Experimental results are presented and comprehensively discussed in the context of deposition conditions for different thin film applications.

In this paper, a method is proposed to determine the in-plane elastic modulus of thin films. Thanks to our custom-designed dual digital image correlation (DIC) system, it is possible to measure the time-resolved strain of film and substrate simultaneously during the microtensile testing. The macroscopic strain difference between coated and uncoated section allows extracting the elastic constants of thin films with high precision. In the case of 400 nm tungsten films coated on each side of one substrate over half of the gauge length, the value obtained agrees well with the bulk one. Furthermore, finite element method (FEM) has been performed to simulate the mechanical behavior of the specimen. High consistency with theoretical and experimental results is verified.

InP membranes have been bonded oxide mediated onto a patterned and unpatterned Si substrate. Indentation is shown to allow local testing on patterned areas. Both responses on patterned and unpatterned are compared and placed in reference to oxide free bonded membranes. Delamination of the membrane was observed to depend on the presence of patterns in the Silicon substrate. It occurs when the indenting load reached 55 mN for an oxide mediated bonded unpatterned structure and 42 mN for an oxide mediated bonded patterned one. This is in both cases below the value of 80 mN obtained for an oxide free bonded membrane (unpatterned). Weibull analysis of these events yielded a modulus m of magnitude 6 to 10, indicating that delamination fracture is relatively predictable with a weaker resistance obtained in patterned oxide mediated bonding. Delamination of the membrane is the result of constraint of plastic flow by the InP/Si interface. Membrane rotation is induced and increases with the indentation load, until it is sufficient to initiate and propagate an interfacial crack.

Nanostructured metallic multilayers with carefully designed mechanical and functional properties are omnipresent in cutting edge technological applications. To ensure the mechanical integrity of such coatings, the Mode I critical Stress Intensity Factor KIC is used to quantify their fracture toughness in order to avoid material failure by appropriate design. In this article, we present a novel approach for the KIC determination of thin and ultrathin films on compliant substrate, based on micro-displacement field analysis using Digital Image Correlation within SEM. Using this method, KIC of a Cu/W nano-multilayer with a total coating thickness of 240 nm was determined as K IC = 4.8 ± 0.05 MPa m , showing excellent agreement with the values published for comparable systems in the literature. To verify the validity of the chosen approach, two independent finite element simulations were employed, thus revealing the role and effect of the compliant substrate on the stress and displacement fields arising around the crack tip in thin films.

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International audience; No abstract available

The trapping of nanoparticles inside a hybrid matrix is of great importance for the design of flexible devices with good mechanical properties and for the manipulation of nanoparticles whilst avoiding the use of nanopowders. In this work, transparent coloured coatings on glass were prepared by incorporating Goethite nanorods in a silica:PHEMA [poly(hydroxyethyl methacrylate)] hybrid matrix. Results show that incorporation of Goethite with a volume content higher than 27 % leads to the formation of a porous structure through a phase separation mechanism which induces a dramatic collapse of the mechanical properties. When the Goethite volume content is below 16 %, the mechanical properties of the coating are governed by the interactions between organic and inorganic domains. Goethite interacts preferentially with the silica network through the formation of hydrogen bonds and no direct interactions with PHEMA were observed. In the absence of strong covalent bonds between the silica:PHEMA hybrid and the nanoparticles, Goethite nanorods do not provide any mechanical strengthening. As a result, interpenetration between silica and PHEMA networks enables fine tuning of the final mechanical properties with the coating silica content.

In situbiaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate using a biaxial testing machine developed on the DiffAbs beamline at the Synchrotron SOLEIL. The mechanical behaviour of the nanocomposite was characterized at the micro- and macroscales using synchrotron X-ray diffraction and digital image-correlation techniques simultaneously. Strain analyses for equibiaxial and non-equibiaxial loading paths were carried out. The results show that the two strain measurements match to within 1 × 10−4in the elastic domain for strain levels less than 0.3% and for both loading paths.

The main purpose of this work was to prepare of single layered TiCxOy thin films. The depositions were carried out from a TiC target by DC reactive magnetron sputtering, varying the oxygen flow. The presence of oxygen changes the film properties between those of titanium carbide and those of the corresponding titanium oxide. X-Ray diffraction (XRD) results revealed the occurrence of a face-centered cubic (TiC-type) phase, with a clear tendency toward amorphization at the highest oxygen contents. Chemical and structural features strongly influence the film properties, which were analyzed in detail as a function of the preparation conditions. Results indicate a systematic increase in resistivity and a decrease in hardness with the increase in the film's oxygen content.

National audience; The local mechanical response of a fluoroelastomer is presented through nanoindentation results. It is well known that elastomers properties aretime-dependent and thus are influenced by the experimental protocol parameters such as the maximum applied load or loading rates. One should consider with great care this time-dependence in the case of nanoindentation tests as it can be in the case of global characterizations. The aim of this study is to determine the influence of the time-dependence during nanoindentation characterization of elastomers. In fine, these investigations should lead to a robust methodology, capable of giving quantitative measurements of the local mechanical properties of industrial products made of elastomers. Thus, this paper draws up a description of the nanoindentation technique applied on elastomers materials and discusses the results which are clearly dependent on the way they are driven. Finally, information provided by this study allowed the technique to be applied on a multilayered composite rubber/polymer, which proved the relevance of the technique by detecting properties gradients within the composite.; La réponse mécanique locale d’un fluoroélastomère est présentée au travers de résultats denanoindentation. Les propriétés des élastomères présentent notamment une dépendance à la vitesse desollicitation et sont ainsi impactées par les variables du protocole expérimental choisies, telles que laforce maximale appliquée ou les vitesses de chargement. Cette caractéristique, intrinsèque à ce type de matériaux, est considérée avec soin dans le cadre d’essais à échelle globale et doit, au même titre, faire l’objet d’une attention particulière lors d’essais de nanoindentation. L’objectif de cette étude est d’appréhender l’impact de la dépendance au temps des élastomères lors de leur caractérisation en nanoindentation. Infine, les investigations doivent pouvoir mener à une méthodologie robuste capable de donner des mesures quantitatives des propriétés mécaniques locales d’élastomères de pièces réelles industrielles. Ce papier dresse donc une description de la technique de nanoindentation appliquée aux élastomères et discute les résultats qui apparaissent clairement dépendants de la manière dont les essais sont conduits. Enfin, les éléments apportés par cette prospection ont été appliqués à la caractérisation d’un composite multicouche caoutchouc/polymère. Cette étude applicative a prouvé l’aptitude de la nanoindentation à détecter desgradients de propriétés au sein du composite.

Laser sources with a controllable flexible wavelength have found widespread applications in optical fiber communication, optical sensing, and microscopy. Here, we report a tunable mode-locked fiber laser using a graphene-based saturable absorber and a tapered mirror as an end mirror in the cavity. The phase layer in the mirror is precisely etched by focused ion beam (FIB) milling technology, and the resonant wavelength of the mirror shifts correspond to the different etch depths. By scanning the tapered mirror mechanically, the center wavelength of a mode-locked fiber laser can be continuously tuned from 1562 to 1532 nm, with a pulse width in the sub-ps level and repetition rate of 27 MHz.

International audience; The development of new devices has created needs of precision, conformal at the atomic level deposition of high quality thin film materials. In the last years, Atomic Layer Deposition (ALD) has received much interest as a potential deposition method for advanced thin film structures. ALD presents several advantages: the film is excellently conformal and reproducible; the film thickness depends only on the number of reaction cycles, which makes the thickness control accurate and simple; the film can be deposited onto all kind of substrates. Because of the process slowness, layer thickness is generally less than 100 nm. This makes more difficult to study all characteristics of the coating. Thin layers deposited onto bulk substrates are generally in tensile or compressive stress state, which may significantly affect physical properties and possibly compromise their lifetime. To determine the residual stress it is mandatory to know the elastic constants that may also depend on the microstructure of the layers and thus the deposition process.In this work, 2D X-ray diffraction (XRD2) in combination with in situ tensile testing has been applied for the first time to measure elastic properties of TiO2 anatase films obtained by ALD. Experimental conditions, the tensile stage being installed in a laboratory micro-diffractometer equipped with a 2D image-plate detector, and the information that can be extracted from 2D diffraction patterns will be discussed. Based on these preliminary results, synchrotron radiation beam time has been allocated to study elastic properties of these thin films. The advantages and disadvantages of the proposed laboratory equipment, with respect to the synchrotron beam lines, are discussed.

Zirconium oxynitride thin films were deposited by dc reactive magnetron sputtering. A zirconium metallic target was sputtered in an Ar + N2 + O2 atmosphere. Argon and nitrogen flow rates were maintained constant whereas oxygen was pulsed during the deposition, implementing the reactive gas pulsing process (RGPP). A constant pulsing period T = 3 s was used following an exponential periodic signal versus time. The introduction time of oxygen was systematically changed from 17% to 83% of the period. The RGPP allowed the synthesis of ZrOxNy films with tuneable metalloid concentrations adjusting the introduction time of the oxygen. Composition and structural variations associated with mechanical, optical and electrical properties exhibited a smooth transition, from metallic-like characteristics, typical of the fcc-ZrN phase, to semi-conducting behaviour corresponding to a mixture of orthorhombic-Zr3N4(O) and γ -Zr2ON2 crystalline phases., Fundação para a Ciência e Tecnologia (FCT) - PTDC/CTM/69362/2006.

Colored hybrid coatings with efficient mechanical properties have been elaborated by introducing goethite (α-FeOOH) nanorods and maghemite (γ-Fe2O3) nanospheres in a poly(hydroxyethyl methacrylate) (PHEMA) matrix. The resulting hybrid coatings have been characterized with regard to the dispersion state of the particles, the swelling behavior of the PHEMA matrix, and the mechanical properties of the coatings. From a mechanical point of view, both goethite nanorods and maghemite nanospheres lead to a strong reinforcement effect of PHEMA, even at low volume fraction. The origin of such reinforcement is attributed to the existence of strong interactions at the iron oxide–PHEMA interface combined with a homogeneous dispersion of the particles. The nature and the strength of these interactions and evidence of their influence on the mechanical behavior of the nanohybrid coatings are reported. Moreover, the goethite-based hybrid coatings exhibit interesting birefringent properties associated with the stabilizatio...

The mechanical behavior of nanostructured stratified W/Cu composites prepared by ion beam sputtering has been investigated using a method combining X-ray diffraction and tensile testing. Tests were performed on a synchrotron light source to analyze the elastic response of the tungsten phase. Three different microstructures have been analyzed: the specimen composed of the thinner tungsten layers reveals an elastic behavior different from the one expected assuming bulk elastic constants. However, Transmission Electron Microscopy (TEM) and Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) measurements reveal discontinuities in the copper layers. As the strain in the related copper clusters as well grains boundary contributions are not experimentally accessible, atomistic calculation are of utmost importance. Polycrystalline materials have already been constructed through the Voronoï method and thanks to TEM observations. Atomistic simulation and calculation are underway to validation.

Understanding the mechanical behaviour of nano-structured thin films in relation to their structure, in particular to the grain size, is of high importance for the development of technological applications. Model nanometric multilayer W/Au systems exhibiting different structures are elaborated. These films are supported by a (thin) polyimide substrate. Films mechanical response is characterized experimentally by tensile tests carried out in-situ in a X-ray diffractometer installed on a synchrotron source. X-ray diffraction in transmission geometry has been used to study the deformations of both phases as a function of applied load. This geometry has been developed in the aim of optimizing the experiment time.

The mechanical behavior of W/Cu multilayers with a period of 24 nm and a 1/3 W/Cu thickness ratio prepared by magnetron sputtering was analyzed using a method combining X-ray diffraction and tensile testing. Tests were performed both with a conventional and a synchrotron light source to analyze the elastic response of the system. Comparison between the strain-load curves obtained in both experimental conditions and estimated curves clearly shows that high quality synchrotron measurements are a preliminary condition for size-effect studies. Moreover, cyclic tests were used to determine the elastic domain of each material and compare their mechanical responses. Plastic strain was observed in copper while tungsten layers were still elastically strained until cracks appeared.

Instrumented nanoindentation is used in conjunction with scanning transmission electron microscopy to evaluate the mechanical resistance at the bonding interface of a 450 nm thick InP membrane bonded oxide-free to Si. Indentation using a Berkovich tip is shown to cause the planes in InP to rotate by as much as 16°. The shear stress resulting from this rotation causes the InP membrane to buckle, forming a debonded blister around the indented zone. The geometry of this blister is used to compute the surface bond energy of InP bonded oxide-free to Si. An average surface bonding energy of 585 mJ m−2 is reported.

We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine with synchrotron standard for in-situ diffraction characterization of thin polycrystalline metallic film mechanical response. The machine has been designed to test cruciform substrates coated by the studied film under controlled applied strain field. Technological challenges comprise the fixation of the substrate, the generation of a uniform strain field in the studied (central) volume, the operations from the beamline pilot. Tests on W and W/Cu multilayers films deposited on polyimide substrates are presented.

International audience; L’article esquisse le portrait collectif d’environ 2 000 réfugiés juifs, originaires de grandes villes allemandes ou annexées au Reich, arrivés à Riga en 1938-1939. Grâce à une politique d’accueil fragile et aux efforts de la communauté juive de la ville, ces familles séjournent en toute légalité dans la capitale lettone, maintenue hors de la guerre jusqu’à l’été 1941. Grâce au croisement entre les archives locales et plusieurs témoignages et Mémoires, l’article apporte des éclairages sur les origines sociales de ces familles, leur séjour à Riga et leurs inquiétudes dans les circonstances du pacte et de ses conséquences locales.