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This article focused on the effects of the presence of liquid on tribological performances of graphite and hexagonal boron nitride (hBN) particles at ambient atmosphere. Two tribological tests conditions have been evaluated with AISI 52100 steel materials. In dry conditions for lubrication tests with pure particles and liquid conditions a drop of liquid is added before or during the friction tests. In dry conditions, graphite and hBN have two different tribological performances, while whatever was the type of liquid in liquid conditions, they are similar: μpure graphite ≈ 0.09 and μpure hBN ≈ 0.42, while μgraphite+liquid ≈ μhBN+liquid ≈ 0.06. Raman spectroscopy and scanning electron microscopy (SEM) investigations bring out weak influence of sliding mechanical constraints for tribofilms built in the presence of the liquid. Different hypotheses have been investigated; tribo-intercalation, influence of adsorption, lubrication by hydrogen, and action of the liquid. The simultaneous presence of liquid and particles induces friction mechanism inside the tribofilm reducing friction due to its nanostructuration.

The aim of this study is to compare the mechanical properties of aged polymers measured at nano and macro scales in order to develop a fast characterization tools to predict polymer durability. Commercial thick PP/PE copolymer samples were aged under artificial aging conditions. The evolution of the mechanical properties with aging time was studied either at nano scale using a nanoindenter and at macro scale using a Dynamic Mechanical Analysis aparatus, nano and macro scale results were compared. Chemical degradation was monitored by infrared spectrometry and the surface topography was studied by Scanning Electron Microcopy. A Voigt model was used to calculate the Young's modulus of the bulk sample using the nano mechanical data and the results were compared to the measured macro Young's modulus. A good correlation was found between macro and nano scales as long as macroscopic defects such as cracks does not appeared. This work shows that nano indentation is a suitable technique to detect early stage degradation of polymers and therefore a powerful tool to predict durability of materials.

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International audience; This study is part of a project initiated by the French Agency, ARS (Agence Regional de la Santé) in Guadeloupe to fight against the spread of the mosquito Aedes aegypti in the past years. These mosquitoes are responsible for several major tropical diseases outbreaks such as the dengue fever, Chikungkunya and more recently Zika. The finality of this project is to design and manufacture a mosquito-proof shield product to prevent larvaes of mosquitos to develop in rain recuperation reservoir and thus to reduce the mosquito population and the infection risk.

International audience; Low Density Polyethylene (LDPE) films were treated by direct fluorination at different conditions, i.e. static and dynamic ones. Modification of the treated films chemical composition was studied by spectroscopic methods (solid state NMR, XPS and infrared spectroscopy). Surface morphology was investigated by SEM and AFM. Also surface energy measurements and electron paramagnetic resonance (EPR) were carried out. Direct fluorination resulted in printability, barrier properties towards O2 and tribological properties enhancement. On the contrary, the barrier properties towards water, initially good, were not improved but maintained.

It has been shown that friction coefficient of powdered lamellar compounds measured at macroscale undergoes a drastic decrease when the experiments are performed in the presence of a low-viscosity liquid. The effect was attributed to the simultaneous presence of the solid particles and the liquid in the area of contact. However, the friction reduction mechanisms are still not yet fully understood. Recently, it was found by Atomic Force Microscopy that the presence of liquid during graphite tribofilm built-up induced a nanostructuration of the film surface and it has been demonstrated that such structuration has no influence on the tribological properties measured at macroscale. In this work, we report structural and friction analyses of MoS2 tribofilms performed at nano- and macroscales, in comparison with graphite tribofilms. In addition, MoS2 and graphite tribofilm structure are investigated by means of transmission electron microscopy. The results clearly indicate that, at macroscale, friction does not always take place at the surface but could occur inside of the tribofilm depending on its nanostructuration.

Macrotribological studies of microcrystalline graphite powder reveal a drastic decrease in the friction coefficient when the experiments are carried out in the presence of low-viscosity liquids. The friction reduction is attributed to the simultaneous presence of particles and liquid in the sliding contact, but the mechanisms involved remain unclear. In order to contribute to the understanding of liquid action in friction reduction mechanisms, nanoscale investigations of the tribofilms have been performed using lateral force microscopy. Attention is devoted to the nanostructure of the film surfaces and their nanofriction behavior using an atomic force microscope. The influence of the tip/sample interfaces on friction properties is investigated by using AFM tips constituted of different compounds (silicon, gold/chromium alloy, silicon nitride or carbon-covered AFM tip) and by performing the nanofriction tests in air or liquid environments. The results indicate that the friction reduction observed at macroscale is attributed neither to the lowering of the shear strength of the carbon/carbon interface in the presence of liquid nor to the nanostructure of the film surface. Collective liquid/particles effects inside the contact during sliding are probably involved.

In order to study the amorphization of sapphire during room temperature ion implantation and the recrystallization of ion-implantation-induced amorphization, sapphire single crystals were implanted with tin (180 keV) at room temperature to fluences from 5×1015 to 1×1017 Sn/cm2. The calculated damage energy at the amorphous/crystalline interface varied from 85 eV/atom (1016 Sn/cm2) to 1.4 eV/atom (4×1016 Sn/cm2). The concentration of Sn at the interface was less than 2 at%. Samples implanted with 4×1016 Sn/cm2 were annealed for 1 hour in oxidizing or reducing atmospheres at a temperature of 700°C, 900°C, 960°C or 1100°C. Regrowth at temperatures below 960°C followed the sequence: amorphous → γ-Al2O3; γ-Al2O3 → α-Al2O3. Essentially all (97%) implanted tin was lost during the 1100°C anneal in Ar–4% H2, whereas all Sn was retained in the sample annealed in the oxidizing atmosphere.

In this work the nanochemical properties of the composite organomineral biomaterial constituting Strombus gigas conch shell are studied by means of dynamic mechanical analyses associated to nanoidentation technique. The measurements are performed on shell samples presenting different surface orientations relative to the growth axis of the conch shell. The influence of the organic component of the biomaterial on its nanomechanical properties is also investigated by studying fresh and dried S. gigas conch shells. Monocrystalline aragonite is used as a reference. For the understanding of nanochemical behaviour, special attention is paid to the pop in events observed on the load/displacement curves which results from nanofractures' initiation and propagation occuring during the load process. In order to better understand the mechanical properties systematic studies of the structure and morphology are performed using scanning electron microscopy, atomic force microscopy and X-ray diffractometry. The hardness and Young's modulus values measured on bio aragonite samples are close to those of the aragonite mineral standard. This surprising result shows that, H and E values are not related to the bio composition and lamellar structure of the bio aragonite. However, it was found that the organic layer and the micro architecture strongly influence the nanofracture initiation and propagation processes in the samples. Statistic study of the pop-in events can help to predict the macroscopic mechanical behaviour of the material.

International audience; The structural parameters of fluorinated nanocarbons presenting different shapes, i.e. spherical, tubular and discotic are investigated and correlated to their tribological properties. Different fluorination rates of graphitized carbon blacks (0D), carbon nanofibres (1D) and a mixture of carbon nanodiscs and nanocones (2D) were achieved under pure molecular fluorine gas flow (direct fluorination). Raman spectrometry, X-ray diffraction and 19F solid state nuclear magnetic resonance underline similar structure and nature of the C-F bonds (covalent) for equivalent fluorine contents. In spite of the similarities of physical-chemical properties at equivalent fluorine contents, the tribological properties of the fluorinated nanocarbons differ. Those properties are discussed taking into account the role of the fluorine content and location of the fluorine atoms in the decrease of the interparticle interactions and in the cleavage of the external fluorocarbon layers to form the tribofilm. Finally, the effect of the shape is discussed.

Niobium implantations were performed in α-Al2O3 single crystals to study the chemical interactions between the implanted species and the oxide and to study the microstructural evolution of the implanted layer. The investigation focused on both as-implanted and the oxide and to study the microstructural evolution of the implanted layer. The investigation focused on both as-implanted specimens and specimens that underwent post-implantation anneals in a reducing atmosphere. Ion implantations were performed at 300 K with 150 keV particle energies and fluences ranging from 1016 to 2 × 1017 ions cm-2. Rutherford backscattering spectroscopy (RBS) and X-ray photoemission spectroscopy (XPS) allowed the characterization of the implanted profiles and determination of the chemical state of the implanted ions. X-ray diffraction at glancing incidence and RBS analysis in a channeling geometry were performed to follow the microstructural evolution of the implanted layer. The oxidation state of niobium and the microstructure of the implanted layer were dependent on the atomic concentration of niobium in α-Al2O3. An amorphous phase was observed after a threshold fluence of 5 × 1016 ions cm-2. The amorphous phase contained small metallic precipitates of niobium with a mean diameter of 1 nm. The physical properties of such niobium clusters embedded in an amorphous oxide layer were studied in detail. Electrical conductivity measurements showed that a hopping process between the metallic precipitates was the likely mechanism operating for this system.

International audience; Nanotribological properties of NbSe2 are studied using an atomic friction force microscope. The friction force is measured as a function of normal load and scan speeds ranging from 10 nm s−1 to 40 μm s−1 under two atmospheres (air and argon). At low speed, no effect of atmosphere is noticed and a linear relationship between the friction and normal forces is observed leading to a friction coefficient close to 0.02 for both atmospheres. At high speed, the tip/surface contact obeys the JKR theory and the tribological properties are atmosphere dependent: the shear stress measured in air environment is three times lower than the one measured under argon atmosphere. A special attention is paid to interpret these results through numerical data obtained from a simple athermal model based on Tomlinson approach.

Thin polycrystalline niobium films were electron beam deposited at 773 K onto α-Al 2 O 3 single crystal with (0001) surface orientation. The samples were subsequently irradiated at room temperature with 1.5 MeV xenon ions to a fluence of 5 × 10 15 ions cm −2 . Niobium-sapphire interface modifications were investigated by Rutherford backscattering spectroscopy and X-ray diffraction at glancing incidence. The specimens were characterized by high resolution transmission electron microscopy performed on cross-sectional specimens. An intermediate layer of 5 nm thickness with an amorphous structure near the interface was observed after irradiation. The thickness of this layer suggests that the mixing is mainly governed by ballistic processes.

We have investigated the influence of chemical bonding and structure of different oxides on niobium implantation effects. For this purpose, single crystals of α-Al 2 O 3 , TiO 2 , MgO and amorphous SiO 2 have been implanted with 150 keV Nb + ions and fluences ranging from 10 16 up to 10 17 ionscm −2 . Two different behaviours have been observed depending on ionicity of the studied materials. For more covalent oxides such as α-Al 2 O 3 , TiO 2 and SiO 2 implanted with low fluences, the implantation profiles are in good agreement with theoretical predictions (TRIM). For high doses (> 5 × 10 16 ions/cm −2 ) the formation of an amorphous layer has been observed in sapphire and rutile. For a typical ionic oxide such as MgO an anomalous depth distribution profile of implanted particles is observed and the major part of implanted niobium is in substitutional sites. The amorphization is not observed even for the highest implantation doses. These results suggest that different chemical effects occur and they could be correlated with the ability to deform octahedral sites in these oxides and space charge effects.

Blisters have been observed in evaporated alumina thin films after xenon irradiation. The aim of this study is to further understand the mechanisms responsible of such process. Surface blistering dependence on thickness of the alumina films as well as irradiation fluence, temperature and post-irradiation thermal annealing have been investigated. From our experimental results, it has been proved that the substrate-alumina interface is not responsible for blistering. Also, according to the gas pressure model and the lateral compressive stress model the latter seems to be more adequate to explain blister formation.

The morphology, the structure and chemical nature of colloidal strontium dimethyl-3,5-hexanoate (SDMH) reverse micelles are investigated by atomic force microscopy (AFM) and analytical transmission electron microscopy (ATEM). Their anti-wear properties first measured through a classical tribology experiment are then investigated via the characterization of the structural and physicochemical properties of the surface film generated during friction tests between the two ferrous surfaces in the presence of the lubricant containing SDMH as additive. AFM studies demonstrate that the film is constituted of platelets of 40 nm thickness with a surface roughness smaller than 1 nm. The ATEM investigations on anti-wear film fragments show that the film is mainly composed of strontianite crystallites formed from the amorphous mineral cores of the micelles. These crystallites, which sizes are significantly larger than the mineral cores of the micelles, are linked to each other by an amorphous intergranular phase. Electron energy loss spectroscopy shows that during friction the colloidal particles loss their organic shell in the contact and that carbon under the carbonate form only remains in the anti-wear film. The good anti-wear properties of this additive are explained by the microgranular structure and the adherence of the anti-wear film on the surfaces.

Absolute quantitative data from atomic force microscopy (AFM)/lateral force microscopy experiments are always difficult to obtain mainly due to the need of the normal force FN and the friction force FF calibration. In this article, we developed an experimental method which allows us to extract absolute quantitative friction data without calibrating any force when the relation between FN and FF is linear or only calibrating the normal force when the relationship is nonlinear. The technique reported here, is suitable for an atomic force microscope that has the cantilever attached to the piezotube translator and an unguided incident laser beam on the cantilever. We take advantage of the piezotube bending during a large scan (5 μm×5 μm), generally considered as an undesirable effect, to calculate a detection factor that allows the determination of quantitative tribological data. The validity of our experimental method is checked on the extensively AFM studied materials, such as muscovite, silicon, and highly ...

The microscopic morphology of alternate thin films of tin and silicon in a multilayered structure was investigated by means of Rutherford backscattering spectroscopy, scanning electron microscopy and cross-sectional transmission electron microscopy. Layers deposited at liquid-nitrogen temperature undergo a slow evolution from continuous layers up to a segregation of the tin atoms to form metallic precipitates between the amorphous silicon layers. The possible mechanisms responsible for this behaviour are discussed.

A comparison of the structural and surface mechanical properties of α - Al 2 O 3 implanted with titanium and niobium ions were carried out. For this purpose, single crystal samples were implanted with Ti + and Nb + ions at 150 keV with fluences ranging from 10 16 to 10 17 ions cm −2 . For fluences above 10 16 ions cm −2 , the substitutional fraction of titanium is two times that of niobium. For high fluences (10 17 ions cm −2 ) the formation of an amorphous layer is evidenced. The different chemical states of atoms in the implanted layers were determined by X-ray photoelectron spectroscopy (XPS). Nanoindentation experiments showed that low fluence implantations of titanium and niobium resulted in the increase of elastic modulus. For high fluences the amorphous transformation softens the implanted material and significant decreases of the hardness and Young's modulus were observed.

Niobium ion.s of 150 keV energy have been implanted at temperatures of 77 or 300 K in α-Al 2 O 3 with doses ranging from 5 × 10 15 to 3 × 10 17 ions/cm 2 and subsequently thermal annealed up to 1273 K in H 2 gas or in air. The structure of the implanted layer has been characterized by X-ray diffraction at glancing incidence and its physical properties have been investigated by means of optical absorption spectroscopy and electrical conductivity measurements. For implantation performed at 77 K, the sapphire reaches an amorphous state at a fluence of 5 × 10 15 ions/cm 2 whereas an implantation dose of 5 × 10 16 Nb/cm 2 is required at 300 K. For heavily implanted samples the amorphous layer has an electrical resistivity typical of poor metal. Annealing treatment performed in Hi gas leads to the formation of an Nb 2 O 5 oxide plus clusters of niobium, whereas a NbA10 4 compound is observed after annealing in air.

The effects of 150 keV Nb ion implantation on α-Al 2 O 3 single crystals have been investigated using Rutherford backscattering channeling technique and optical absorption measurements. Analysis of the implantation and damage profiles have been performed on samples implanted with doses ranging from 5 × 10 14 to 10 17 Nb + cm −2 . The experimental implantation and damage distributions have been compared with TRIM code calculations. For the lowest implantation doses ( 15 ions cm −2 ) the damage distribution and the implantation profile are in good agreement with TRIM predictions assuming a displacement energy for oxygen and aluminium atoms of 75 eV and 16 eV respectively. For doses higher than 10 15 ions cm −2 a concomittant inward shift and broadening of the defect profile is observed probably due to a defect migration which occurs during the ion implantation process. For doses higher than 5 × 10 16 ions cm −2 the defect concentration increases leading to the formation of an amorphous layer. A comparison between RBS channeling analysis and optical absorption measurements has been made in order to make clear the nature of the ion implantation damages and to ascertain the amorphization mechanisms.

As part of extensive fundamental studies of ion-implanted ceramics, analytical electron microscopy (AEM) has been used to characterize [0001] single crystal 6H α-silicon carbide implanted at room temperature with 160 keV 57Fe ions to fluences of 1,3, and 6 x 1016 ions/cm2. AEM was performed at 100 kV with a Philips EM400T equipped with a field emission gun, a 6585 STEM unit, an EDAX 9100/70 energy dispersive X-ray spectrometer (EDS), and a Gatan 666 parallel-detection electron energy loss spectrometer (PEELS).A micrograph of a cross-sectioned specimen implanted with 6 × 1016 ions/cm2 is shown in Fig. 1. The implanted region extending to 195 nm from the surface is amorphous, as confirmed by convergent beam electron diffraction (CBED) patterns (insets), and contains iron at levels easily detectable by EDS (Fig. 2). The 15 nm lattice fringes of the edge-on 6H basal planes in the substrate provide an unambiguous depth calibration scale. The transition layer at the end of the ion range exhibits the expected strain contrast. The depth profile of the implanted iron was measured by EDS line scans perpendicular to the implant surface; the mean of three of these scans is shown by the filled symbols in Fig. 3. The integrated iron profile agrees with the expected 6.0 × 1016 ions/cm2 only if the density of the amorphous SiC is equal to that of its crystalline forms, rather than the 20% lower density reported earlier.

We, the International Community of IRaP'94, thoroughly investigated the anti-oxygen effects on the surface properties of hydrogel bodies immersed in aqueous solution of high salt concentration.

Thin films of Au, Ag have been evaporated on (0001) surface of sapphire and then the interfaces were irradiated with xenon ions. Ion energy of 1.5 MeV, fluences of 3 × 1015 to 2.2 × 1016 ions cm−2 and irradiation temperatures at 77 and 300 K were used. The evolutions of the interfaces were studied by different techniques such as Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), optical absorption. X-ray diffraction at glancing incidence and electrical resistivity measurements. Blistering is observed for all specimens bombarded with fluences as low as 3 × 1015 ions cm−2. The RBS analysis seems to show a ballistic mixing at Ag or AuAl2O3 interfaces but X-ray diffraction at glancing incidence does not reveal any new compound formation at the interfaces. Nevertheless optical absorption shows the formation of silver or gold metallic precipitates embedded into Al2O3.

Sn layers 64 nm thick deposited onto crystalline Si were irradiated at room temperature using 100 keV Si+ ions, with fluences φ ranging from 1 × 1015 to 9 × 1016 ions cm−2. RBS analyses show that Si atoms move from the bulk towards the surface as the fluence increases, and are found at the very surface for φ = 4 × 1016 Si+ cm−2. Then a saturation is reached. Sn and Si profiles determined using a Fortran programme, and the calibration of depth scale is obtained from cross-sectional TEM observations. The average composition of the intermixed layer is given as a function of φ. Different layers of various crystallinity are found below the surface and their nature is discussed.

The evolution of 100 keV Si+ beam irradiated tin layers on silicon wafers was monitored by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and conversion electron Mossbauer spectroscopy (CEMS). The irradiation fluence varied from 1 × 1015 to 2 × 1017 cm-2. After a 4 × 1016 cm-2 fluence, silicon atoms reach the surface, a nd the unsputtered tin atoms are found either in precipitates embedded in an amorphous surface layer, the thickness of which increases with increasing irradiation fluence, or incorporated in substitutional sites in amorphous silicon. Indeed, CEMS results yield Mossbauer average parameters of substitutional tin in silicon and give an estimation of the lower limit of substitutional atomic tin fraction.

Multilayers of iron and titanium of total thickness 2000 A have been deposited on beryllium and silicon substrates, using an electron gun under ultrahigh vacuum conditions (10 −9 Torr). The respective thicknesses of the iron and titanium films have been chosen with a view to predetermining the following global compositions: Fe 29 Ti 71 (eutectic), Fe 33 T1 66 , Fe 50 Ti 50 , Fe 58 Ti 42 , and Fe 67 Ti 33 . The as-deposited multilayers have been characterized in situ by Rutherford backscattering spectrometry of alpha particles (RBS). The ion beam mixing has been performed using Xe + ions of 800 keV energy up to a dose of 2.4 × 10 16 Xe + CM −2 . The magnetic properties of the mixed samples have been measured by conversion electrons Mbssbauer spectroscopy (CEMS). Characterization by RBS and X-ray diffraction at glancing incidence have been performed. The formation of amorphous iron-titanium alloys is shown.

Metal films on insulator substrates such as Al203or Si02have applications in industrial fields such as electronics, connectics, biotechnology, etc. One of the most important problems arises from the poor adhesion of the metallic layer to the insulator. This poor adhesion is generally attributed to a lack of chemical affinity, Van der Waals or electrostatic forces between the two materials (1,2). Metals having a large negative value of free energy for oxide formation show a strong adhesion to the oxide substrate (3,4), whereas metals with low oxygen affinity are weakly bonded (5–7).

Silicon and tin multilayers of total thickness 200 nm have been deposited at room temperature on beryllium and glass plate substrates under high vacuum (

Summary Electron energy-loss spectroscopy (EELS) in the analytical electron microscope has been used to characterize nanometre-scale phases of overbased strontium 3,5-dimethylhexanoate reverse micelles and the tribological film obtained during a friction test when the phases are used as lubricant additives. Accurate chemical, molecular and structural information on these materials are deduced by interpreting the EELS near-edge structure. This approach allows confirmation of the composite structure of the micelles, which contain a mineral core and amorphous strontium carbonate surrounded by an organic shell. It also allows identification of the chemical composition and physical structure of the tribological film as an assembly of pure strontium carbonate microcrystals, i.e. strontianite, distributed in an amorphous intergranular phase.