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Degradation of roots from beech trees was investigated by a novel approach: localization and elemental characterization of predominant brown substances were performed at ultrastructural scale using electron energy loss spectroscopy (EELS). This technique allowed us to detect light elements such as C and N, main constituents concerned in the degradation of plant tissues, within cellular constituents observed with a transmission electronic microscope, after having localized them by light microscopy. The results showed that there was no relationship between the brown pigmentation of the cellular substances and the presence of N, a relationship previously found in studies of degrading leaves. Other elements such as Si and Ca were also found to be involved in these root degradation processes. This approach seem powerful for detailed descriptions of the process of root degradation in soil.

The interaction of MoS 2 single-layer dispersion with 1,10-phenanthroline has been studied over the pH range 0–11. Only protonated phenanthroline initiates flocculation of dispersion and formation of intercalation compounds. Two intercalated phases containing respectively 0.31–0.35 and 0.1 mol of phenanthroline per mol MoS 2 have been isolated. In the first one (interlayer spacing c = 14.92–15.56 A) the planar organic species are inclinated with respect to MoS 2 layers. In the second one ( c = 9.7 A) these moieties are oriented parallel to the layers.

We have studied the interface formed on a poly(p-phenylene vinylene) (PPV) thin film by deposition of a thermally evaporated aluminum layer. The cross-section of Al-coated PPV films was analysed by analytical transmission electron microscopy and complemented by X-ray photoelectron spectroscopy. The subsequent presence of oxygen was detected at the polymer-metal boundary accompanied by modified aluminum and carbon bonding states indicating chemical interaction between the metal and the polymer has occurred. The PPV structure was also affected by the evaporation process by the formation of a sublayer in the polymer bulk beneath the interface which reveals the presence of carbonyl groups and possible reticulation of carbon. It was suggested that the interaction between aluminum and carbon was initiated from the binding of the metal atoms to the oxygen of the observed sublayer.

This paper presents morphological and local structure studies, carried out by means of transmission electron microscopy and X-ray absorption spectroscopy techniques, of the mineral core of organometallic reverse micelles in a dispersion in hydrocarbons. The results obtained for the micelles and their aggregates allowed us to propose a layered structure for the mineral core and the molecular stacking.

MoS[sub 2] intercalation compounds with transition metals could be of great interest for catalysis of petrochemical processes, and also from the magnetic point of view since, for two-dimensional metallic layers included into a diamagnetic matrix, unusual magnetic properties can be expected. Iron-intercalated molybdenum disulfide, obtained by flocculation of a MoS[sub 2] single-layer dispersion in the presence of ferrous sulfate, was studied by electron microscopy and Moessbauer spectroscopy. Iron was found to occur at both II and III oxidation states between the MoS[sub 2] layers. The formation mechanism of this intercalated compound and its composition are discussed.

Electron Energy Loss Spectroscopy, at Mn M2,3 and L2,3 edges is used in order to investigate the ionization state of manganese in a new oxybromide compound. The experimental procedure and the various approaches used to determine Mn oxidation state (edge energy shifts and L3/L2 ratios) are tested on a wellknown manganese oxychloride containing Mn2+ and Mn3+ cations. The comparison of the respective confidence limits of each approach shows that the best precision is obtained with the method based on the energy shifts of the Mn L2,3 edges. That experimental approach applied to the manganese oxybromide allows us to confirm that Mn4+ is present in this new compound and a reconstruction of the L2,3 white lines, using normalized standard spectra, seems to show the presence of three Mn oxidation states in the material. Microsc. MicroanaL Microst1Uct.

The room temperature synthesis of NiPS3 by mixing a nickel salt and [Li4+(P2S6)4−] in water from which oxygen has not been removed leads to an oxygenated phase. Nickel K edge X-ray absorption data and nickel L2,3, phosphorus and sulfur K edges electron energy loss spectroscopy experiments show that a pure oxythiophosphate phase with a formulation close to NiPS2O is obtained. This composition is explained by a partial oxidation of the pristine (P2S6)4− anion, before reaction to form (P2S4O2)4−. The higher oxidized anions are destroyed by the breaking of the phosphorus-phosphorus bond.

The antiwear action of overbased calcium sulfonate detergents in engine oils is studied here by analysis of the wear particles generated during friction tests between two ferrous surfaces. These particles arise from the delamination of the reaction film formed on the rubbing surfaces. This paper deals with the structural and physiochemical changes that the colloidal particles in the contact region have undergone, and which lead to the build-up of the interfacial film. Transmission electron microscopy on the particles shows that the film is composed of calcite crystallites coming from the carbonate cores of the crystallized colloidal particles. Amorphous intergranular zones are responsible for the film “cohesion”. Electron energy loss spectroscopy shows that the colloidal particles lose some fraction of their organic shell in the contact. The good antiwear properties of these additives is explained by the microgranular structure and the adherence of the surface film.

The misfit-layer compounds, PbNb 2 S 5 and SmNb 2 S 5 , possess a composite lamellar structure consisting of alternating NbS 2 /MS/NbS 2 layers, where M = Pb or Sm. The juxtaposition of slabs gives rise to a Van der Waals gap between the sheets. Consequently, these compounds can be mechanically and/or chemically exfoliated. Mechanical exfoliation is effected by exposure to high-intensity ultrasound waves in a solvent capable of hydrogen bonding with the sulfide surfaces of the monolayers. Chemical exfoliation, in the case of PbNb 2 S 5 , is carried out by first intercalating the layered material with sodium and by subsequently exposing the intercalated compound to a polar, protonic solvent. Exfoliation via both techniques is described and the exfoliated products are compared. Monolayers and restacked monolayers are characterized by transmission and scanning electron microscopy, platinum-shadowed replicas, and electron microprobe analysis.

The metathesis reaction in aqueous media between Ni 2+ and (P 2 S 6 ) 4− ions, leading after drying to the Ni 2 P 2 S 6 phase, was followed by in situ X-ray absorption. This reaction proceeds regularly to the final sulfide phase. The complexes formed in water during the reaction as deduced from the EXAFS study correspond to single sheet crystallites with a diameter of ∼0.5 nm and a composition close to (H or Li) 1.6 Ni 2 (P 2 S 6 ) 1.4 . After drying, this phase does present a local structure corresponding to crystallized Ni 2 P 2 S 6 and a transmission electron microscopy study confirms the occurrence of these crystallites, scattered within an amorphous matrix. The temperature dependence of the magnetic susceptibility has been measured from 5 to 310 K. The magnetic behavior, which shows magnetic ordering of only the crystalline portion of the phase, is well explained by the structure of the end-product a-NiPS 3 .

This paper presents some results on the morphology, chemical nature and physical structure of overbased calcium alkylbenzene sulfonate reverse micelles in dispersion in hydrocarbons obtained using conventional (CTEM) and energy-filtered transmission electron microscopy (EFTEM) and extended X-ray absorption fine structure spectroscopy (EXAFS). It was demonstrated that such colloidal particles are stable when they are brought out of their original medium and that they can be accurately modeled by a mineral core made up of amorphous calcium carbonate surrounded by an organic shell of alkylbenzene sulfonyl radicals.

Une etude des degâts d'irradiation subis par des particules colloidales d'isooctanoate de plomb est realisee au moyen de la diffraction electronique et de la spectroscopie de pertes d'energie d'electrons transmis resolues dans le temps. L'etude porte a la fois sur les transformations structurales et chimiques provoquees par le faisceau d'electrons. Les resultats sont interpretes en utilisant une approche de type cinetique chimique qui nous permet de deduire les ordres partiels de reaction relatifs a la concentration d'isooctanoate de plomb et au taux d'irradiation

The basic structures of three superconducting phases of the Bi family are determined by means of electron microdiffraction. For each phase and for each possible structure (Fmmm, A2aa, Amaa), whole diffraction patterns, including zero-and first-order Laue zones, are simulated. The comparison of experimental and simulated diffraction patterns allows one to propose a basic structure for each compound. The 2201 phase, whose Tc=10 K, has the Amaa symmetry, whereas the 2212 and 2223 phases (Tc=85 K and 110 K, respectively) have the A2aa symmetry.

MnBr2 reacts with MnO2 in a temperature range of 300 – 500°C to produce a new manganese oxybromide. Chemical analysis and structural determination indicate that the oxybromide possesses a chemical formula, Mn7.5O10Br3, which is different from the manganese oxychloride. The symmetry is tetragonal with a = 9.327(5) Ȧ. and c = 13.104 (3) A . The structure has been solved in the space group 14/mmm with Z = 4, R = 0.046. The oxybromide appears as a lacunar equivalent of Mn8O10Cl3 with empty Br6 octahedra.

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We have inserted iodine and chlorine in BiSrCaCuO (BSCCO) and YBaCuO (YBCO) granular compounds. The halogenated materials were investigated using Raman spectroscopy, susceptibility, x-ray diffraction, x-ray photoelectron spectroscopy. Cl- and I 3- anions were found. We briefly discuss the insertion mechanism of these species.

Many experimental works are concerned with the microinvestigation of interface bodies created during the wear process (especially wear particles). Previous works wing STEM have shown that ZDDP wear protection is associated with the structureless nature of wear debris, so that friction-induced amorphization was a key factor to obtain the antiwear conditions. In this paper, the synchrotron radiation, EXAFS (Extended X-ray Absorption Fine Structure) is used to probe the local environment of atoms (Fe and Zn) in interface ZDDP films. Results clearly show the fully amorphous character of these materials. Consequences on wear models are then discussed. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Tribology Conference in Atlanta, Georgia, October 8–10, 1985

The structures of the gels and lubricating greases formed by lithium 12-hydroxyoctadecanoate have been investigated by differential enthalpic analysis and optical and transmission electron microscopy. We have attempted to correlate the structures of gels and their rheological properties. It is shown that the mechanical behavior of the gels is related to the existence of a large scale tridimensional network of soap fibers. The importance of a critical temperature for the growth of the gel network is pointed out.

Wear debris from ZDDP lubricated tests run under mild wear conditions have been investigated by X-ray Absorption Fine Structure Spectroscopy (EXAFS). Special attention has been paid to the state of iron in the amorphous wear fragments. Results indicate the presence of Fe3+ species as a modifier of the phosphate network formed during tribo-reaction. As the anti-wear regime of ZDDP is characterized by a decrease of the abrasive wear, it is suggested that the anti-wear action of ZDDP is reliable to the diffusion of iron oxides in the phosphate, this latter being gently delaminated. Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

The microstructure of wear particles formed under boundary lubrication with a zinc dialkyldithiophosphate (ZDDP) is investigated in the analytical scanning transmission electron microscope. This is made possible by the generation of wear particles in foil form. Physical and chemical data are reported and correlated with surface analysis data obtained on reaction films. The measurements show that the thin foil particles consist mainly of an amorphous material containing iron, phosphorus, sulphur, zinc and oxygen (carbon was not detected). These particles are the result of a reaction of the ZDDP with metals under friction.

Solutions of a complex polyoxypropylene glycol ester in a paraffinic solvent have been investigated by means of elastic light scattering, quasi-elastic light scattering and transmission electron microscopy. Above a concentration of 0.01 g/cm 3 the dispersed particles consist of micelle-like aggregates containing an average two or three ester molecules. The variation of the scattered intensity as a function of concentration in the concentration range of 0.01 to 0.22 g/cm 3 is analysed in the framework of a recent hard-sphere theory.

The effect of a small proportion of a polar additive in paraffinic base oils has been studied. The experimental test device is a disk machine. The traction is measured in different lubrication regimes. First of all, as a reference, it was found that in the real EHD regime (Λ > 2), no friction-reduction effect occurs. In contrast, where a thin-film situation exists (Λ < 2), an important friction modification appears. Evidence is given that this effect is related to the presence of an absorbed layer on metal surfaces. These results are also discussed in terms of structural properties of the solution. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983

It is well known that in many tribological situations antiwear additives act by reaction film formation on contacting surfaces. In the present paper we describe our observations on the reaction film formed with a zinc dialkyl dithiophosphate and the wear particles. Detailed structural and chemical information has been obtained by using optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray energy spectrometry. The results show a clear connection between the reaction film material and the nature of the wear particles present in the lubricant; both a highly dispersed phase system and a layered structure are present. The origin of the wear particles is discussed in terms of crack initiation mechanisms.

A new technique of freeze fracturing was used in conjunction with electron microscopy to study debris formed by polymeric materials sliding against a steel surface. The correlation between characteristic features of the debris and the frictional performance of the polymers as well as the mechanism of debris formation are discussed.

This paper presents some new results concerning the evolution of the local order in the mineral core of reverse micelles during their synthesis. It is shown that no drastic structural change occurs during the reaction, the mineral core remaining amorphous with a local order close to calcite one.

The pressure distribution in the static and elastic sphere/plane contact containing a thin layer having a Young's modulus different from the substrate is studied by means of a foundation model taking into account the elastic deformations of the substrates and the pressure dependance of the Young's modulus of the material of the layer.

Local analysis is the study of the immediate environment of selected atoms in materials. Analytical data have been collected on wear particles by EXAFS (Extended X-Ray Absorption Fine Structure). Different cases are here investigated to establish the correlation between tribological data (wear rate) and structural data on wear debris (local environment, nature of atomic bonds, etc…), with an anti-wear additive (zinc dithiophosphate), a detergent (neutral calcium sulfonate) and the combination of both two. It has been found that whatever the combination of additives used, high wear rates are associated with micro-crystalline wear particles. Conversely, low wear rates are associated with highly amorphous debris.

Until now, the problem of friction reduction under boundary lubrication has been interpretated in term of shearing properties of monolayers mainly because there is a lack of knowledge on the thickness of the interface when sliding occurs. Tunneling conductivity (TC) is perhaps unique in that it permits to get “in situ” information on thickness variations at the picometer level (as in the dedicated tunnel microscope). We have applied this technique to a friction test. Main results show that there is a connection between the friction force and interactions between solid surfaces, suggesting that boundary lubrication is not only a rheological problem.