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A comprehensive analysis of Bi2O2CO3 nanosheets, which were synthesized using nanosecond‐pulsed discharges in water between bismuth electrodes, was conducted in order to investigate the crystallographic features of this material. Electron diffraction, X‐ray diffraction and electron energy‐loss spectrometry techniques revealed the presence of a stoichiometric tetragonal Bi2O2CO3 structure, labelled BOC in this study. It crystallizes in the body‐centred tetragonal Bravais lattice and belongs to the I4/mmm space group (No. 139), with the following lattice parameters: a = 3.91, c = 13.77 Å. The nanosheets adopt square shapes. This shape is dictated by the symmetry elements of its point group (4/mmm) under the prevailing local conditions. From the energetic point of view, this shape, dictated by the 4/m2/m2/m point group and therefore a pinacoid, corresponds to an absolute extremum, an indicator of the stability of these BOC nanosheets. Most nanosheets are crossed by equal‐inclination fringes or bend contours. These bend contours reflect the fact that the BOC nanosheets contain crystal defects and/or are so thin that they bend elastically, leading to rotation of the lattice planes towards the diffracting Bragg position. The diffraction patterns corresponding to bend contours intersecting along the [001] zone axis have been studied in detail. Extra reflections are superimposed on the diffraction pattern of the BOC crystallographic structure. These extra reflections are essentially attributed to two phenomena: multiple diffraction and local disorder–order transformations of the BOC crystal structure, passing from a body‐centred tetragonal to a primitive Bravais lattice. A mechanism related to the ledge mechanism (kinks and jogs), explaining the formation of nanosheets in a metallic matrix, has been adapted and proposed for the formation of BOC nanosheets in water. When the nanosheets are removed from the water, they become carbonated once in the air, leading to the formation of BOC that inherits the nanosheet morphology. [ABSTRACT FROM AUTHOR]

To clarify the influence of manganese on the oxidation behavior of Ni–Cr alloys, high resolution transmission electron microscopy was used to examine the microstructure and chemistry of oxide scales forming at 1050 °C on Ni–25Cr–xMn (x = 0.5, 1 and 1.5% wt) in 200 Pa O 2. The scales consisted of two layers of chromia and one layer of spinel Mn 1+x Cr 2-x O 4. The internal layer exhibited an equiaxed grain structure, whereas columnar grains developed in the outer layer. The results demonstrated that the spinel composition at the chromia-spinel interface was similar regardless of the manganese concentration. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract NiO thin films with random, fiber and in-plane textures have been successfully deposited at near room temperature by reactive magnetron sputtering on glass, silicon and Al 2 O 3 (0001) substrates. Self-texture related with the deposition conditions and crystallographic characters competes with the driving force from the matched substrate. Such a competition can be used to control the texture of thin films on matched substrates, especially when the promoting orientations from self-texture and substrate are different. Enhancing this competition tends to suppress the self-texture of NiO thin films on Al 2 O 3 (0001) substrates, whereas restricting the competition is beneficial to produce the in-plane textured NiO thin films. In addition, it is found that the optical transmittance of NiO thin films on Al 2 O 3 (0001) substrates can also be tuned by such competition. Interfacial microstructure analyses of NiO thin films on amorphous substrates clearly evidence the existence a nanocomposite layer at the initial growth, which is composed of NiO nanocrystals surrounded by amorphous matrix. In contrast, in-plane textured NiO thin films on Al 2 O 3 (0001) substrates exhibit sharp interface without nanocrystals or amorphous matrix. We believe these results provide a general framework of tuning the textures and properties of thin films on matched substrates. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Discharges in liquid nitrogen between 2 electrodes made of either Cu, Ag or Cu 28 Ag 72 enable the production of several types of comparable nano-objects. First, Cu nanoparticles (NPs) with sizes close to 5 ± 4 nm nm and 40 ± 10 nm are obtained with Cu electrodes and get oxidized in the air to form CuO after liquid evaporation. With Cu 28 Ag 72 electrodes, copper contains a small amount of silver that inhibits oxidation. Next, silver nanoparticles are spherical but when doped with copper, they are facetted. Silver-containing nanowires have very similar features whether they are synthesized with silver or CuAg electrodes. They are made by assembly of NPs. Ag nanosheets are either single crystals in the case of CuAg electrodes or assembly of NPs in the case of silver electrodes. Finally, silver nanorods with traces of copper are only found with CuAg electrodes. Time-resolved optical emission spectroscopy indicates that the optical thickness decreases when copper is added to silver, lines appearing immediately after breakdown and not only after emission of a broad continuum. Emission of lines belonging to the N II system is then observed. The energy deposited being nearly constant, the structure of the discharge is assumed to be changed. [ABSTRACT FROM AUTHOR]

The peculiar behaviour of zinc depending on whether it is used pure or alloyed in Cu 63 Zn 37 wire electrodes leads either to nanosheets or to nanoparticles when it is processed by nanosecond pulsed discharges in liquid nitrogen. Using one electrode of copper and one electrode of zinc gives core-shell Cu@Zn nanoparticles but no alloy for the smallest nanoparticles (typically below 20 nm). Once nitrogen is evaporated, their oxidization in air produces Cu 2 O@ZnO nanoparticles. If both electrodes are made of Cu 63 Zn 37 , then the smallest nanoparticles are made of Cu and Zn and oxidized next in air to give Cu 2 O and ZnO nanoparticles. No alloy is formed either. Time-resolved optical emission spectroscopy gives clues on the origin of such behaviours, explaining why no alloy is formed when electrodes are made of different materials. [ABSTRACT FROM AUTHOR]

Nitrogen-doped Cu2O thin films have been deposited at room temperature by reactive magnetron sputtering. It is demonstrated that nitrogen doping in Cu2O can significantly improve the electrical properties by increasing the carrier concentration. The nitrogen chemical state in doped thin films has been investigated by electron energy loss spectroscopy, which reveals that nitrogen is in the form of molecular N2 in Cu2O thin films rather than the N-anion. Such experimental results are well consistent with the recently reported calculation, suggesting that in N-doped Cu2O, nitrogen mainly substitutes Cu in the molecular form, (N2)Cu, rather than in the atomic form at the oxygen site (Nq). [ABSTRACT FROM AUTHOR]

The room temperature growth of highly ＜111＞ oriented sputtered NiO thin films on glass and silicon substrates previously covered with a ＜111＞ oriented Cu2O film is reported. The results are compared to those obtained from single layer NiO thin films using the same deposition conditions. Electron microdiffraction analyses indicate that NiO columns are heteroepitaxially grown on the columns of a Cu2O seed layer. The well-matched atomic configurations between the Cu atoms in the {111} planes of Cu2O and the O atoms in the {111} planes of NiO may provide a strong driving force to promote this local heteroepitaxial growth. Such heteroepitaxial growth behavior in the columns can significantly improve crystallization. Moreover, valence electron energy loss spectroscopy has been employed to investigate the interband transition properties of the NiO films, which shows that the interband transition intensity can be tuned by this local heteroepitaxial growth. [ABSTRACT FROM AUTHOR]

Binary copper oxide (Cu 2 O, Cu 4 O 3 and CuO) thin films have been selectively deposited on glass and silicon substrates by magnetron sputtering at room temperature from a metallic copper target in various Ar–O 2 reactive mixtures. The influence of oxygen flow rate and total pressure on the film structure and its preferred orientation has been studied. A schematic deposition diagram, which describes the film structure as a function of O 2 flow rate and total pressure, is depicted by combining X-ray diffraction and Raman spectrometry. The oxygen flow rate process windows for Cu 2 O or Cu 4 O 3 single phase synthesis are narrow, while that for CuO is wider. Between two single phase domains, biphase films are systematically deposited. It is found that the deposition total pressure is a relevant parameter to control the texture and the morphology of pure Cu 2 O and Cu 4 O 3 films. Low total pressure favors the growth of planes with high surface energy ((1 0 0) for Cu 2 O and (1 0 1) for Cu 4 O 3 ) parallel to the substrate. On the other hand, high total pressure facilitates the growth of planes with low surface energy ((1 1 1) for Cu 2 O and (1 0 0) for Cu 4 O 3 ). The oxygen flow rate is effective to control the preferred orientation of CuO thin films that evolves from 〈1 1 1〉 to 1 ¯   1   1 with the increase of oxygen flow rate. These results are supported by transmission electron microscopy observation in cross section. [ABSTRACT FROM AUTHOR]

Aluminum-doped zinc oxide (AZO) films have been synthesized using reactive high power impulse magnetron sputtering (HiPIMS) in a wide range of Al contents, 0.6–14.7 at.%. The film structure and microstructure investigated by X-ray diffraction and transmission electron microscopy evolves from nanocrystalline columnar film towards ultrafine nanocrystalline films of wurtzite ZnO structure upon increasing the Al content. Electrical properties measured by 4-point probe and Hall effect setups revealed that effective doping maybe achieved up to 3 at.% Al by using HiPIMS. Most importantly, optical transmittance and electronic structure measurements at the Al L 2,3 of electron energy loss near edge structure (ELNES) contain signatures of dopant activation, and dopant segregation that may serve to investigate on the origin of electrical properties degradation and to optimize the electrical properties of AZO films. • Al-doped ZnO films synthesized by reactive HiPIMS of preserved wurtzite structure up to 14.7 at.% Al • Increasing the dopant content above 1 at.% Al decreases the crystallinity. • High density of charge carriers is induced by Al doping up to 3 at.% Al. • Al contents above 3 at.% inactivate a significant fraction of Al dopant. • Electronic structure at the Al L 2,3 edge can be used to extract the fractions of active/inactive Al dopant. [ABSTRACT FROM AUTHOR]

We report the homoepitaxial growth of Cu2O thin films with tunable growth orientations on glass and silicon substrates using reactive sputtering. The importance of the initial growth stage on the subsequent development of specific orientations is detailed. Among the various deposition conditions, the total pressure is found to have a strong effect on the preferred orientation of Cu2O films: 〈100〉 at low pressure and 〈111〉 at high pressure. Furthermore, the texture of the deposited films is also influenced by that of a first Cu2O layer acting as a continuous seed layer. Effectively, using a two-step deposition procedure, a highly textured Cu2O thin film with controlled orientation can be formed independently of the deposition conditions. Provided that it has a sufficient thickness, this layer acts as a seed layer that determines the crystal orientation of a second layer grown even after air exposure and/or without specific cleaning of the surface prior to deposition. High-resolution transmission electron microscopy analyses evidence that the top layer grows in homoepitaxy with the seed layer with a microstructure consisting of single crystal columns crossing the interface between the layers. [ABSTRACT FROM AUTHOR]

We have characterized by transmission electron microscopy several new phases that we have discovered in bulk alloys of the Al–Cr–Fe system. These structures are an icosahedral compound and several approximants of the decagonal phase. According to the indexation of the electron diffraction patterns (EDPs), some of the approximants are not of Fibonacci type. These EDPs correspond to nanodomains, which are due to disorder introduced by quenching the alloys after melting the pure constituent metals. For these new types of approximant, we propose a crystallographic description related to the usual Fibonacci description. In addition, we suggest a construction of the corresponding tilings. The orientation relationships between these structures are described. [ABSTRACT FROM AUTHOR]

Abstract: For the purpose of obtaining an improved performance of the graphite negative electrode of Li-ion batteries, a novel graphite–tin composite has been synthesized by reduction of tin chloride (SnCl2) with KC8 in THF medium. This composite contains nano-sized tin particles dispersed on the graphite surface and free tin aggregates. Lithium electrochemical insertion occurs both in graphite and in tin. An experimental reversible specific charge of 489mAhg−1 is found stable upon cycling. Such a value is lower than the maximum theoretical one of 609mAhg−1 suggesting that only a part of tin is involved in the lithium insertion/extraction process. This part of active tin responsible for the stable capacity could be that bound to graphite. To the contrary, free tin aggregates could contribute to an extra capacity that decreases upon cycling in relation with the volume changes that occurs during alloying/dealloying. [Copyright &y& Elsevier]

We have identified two ?-brass phases in the Al–Cr–Fe system by X-ray diffraction and transmission electron microscopy. These structures (rhombohedral and cubic) are closely related to each other and can co-exist in the same alloy together with approximants of quasicrystals. In particular, a long-period superlattice, typical of ?-brass phases, was characterized in the cubic structure. This superstructure is constituted of inversion domains separated by boundaries lying at (10) planes. The displacement vector between like domains was determined from high resolution microscopy data. This study deals also with a description of some structural links between ?-brass phases and approximants of decagonal and icosahedral quasicrystals. [ABSTRACT FROM AUTHOR]

Metal-based composites are currently under investigation as possible negative-electrode materials in lithium-ion batteries. We present here a new composite material composed of zinc particles deposited mainly onto graphite surfaces. This Zn/graphite composite was prepared by reduction of zinc chloride ZnCl2 by a KC8 graphite intercalation compound in tetrahydrofuran. Electrochemical insertion of lithium occurs both in graphite and in zinc. A stable specific charge of 355 mAh g-1 is obtained starting from the third charge/discharge cycle. As in Sb/graphite composites prepared by the same technique, the stabilizing role of graphite against metal fragmentation and pulverization is demonstrated. [ABSTRACT FROM AUTHOR]

Preparation of antimony-based graphite composite using a graphite intercalation compound as precursor was described. A C12SbCl5 graphite intercalation compound was reduced by caesium in the vapor phase at 70 °C. The resulting compound was composed of antimony particles deposited on a graphite matrix. Used as negative-electrode material for lithium-ion rechargeable cells, this composite presented not only an improved storage capacity (490 mAh g-1 between 0 and 2 V versus Li+/Li) by comparison with free graphite but also enhanced dimensional stability of lithium–antimony alloys. [Copyright &y& Elsevier]

Metal-based composites are under investigation as possible negative-electrode materials in lithium-ion batteries. In this paper, we present a new composite material constituted of antimony particles dispersed on graphite. The antimony–graphite compound is prepared by antimony pentachloride reduction with KC8 in tetrahydrofuran. The high reversible capacity of 420 mAh g−1 and the good stability suggest that the association of antimony with graphite allows not only to improve reversible capacity but also to prevent the metal from particle pulverisation generally occurring during lithium alloying. [Copyright &y& Elsevier]

There is a growing interest in mixing spintronics and superconductivity to develop original energy-efficient nonvolatile memory and logic devices. Research works conducted so far have mostly focused on superconductor with critical temperature Tc lower than 10 K. Here, we report on the growth and characterization of MgB2/Ni80Fe20 and MgB2/Co bilayers, where Tc of the MgB2 layer is of the order of 30 K. Ferromagnetic resonance was undertaken to analyze the spin pumping into MgB2. The larger magnetization at saturation in Co, as compared to Ni80Fe20, induces a smaller spin pumping contribution to the damping when MgB2 is normal. A spin pumping reduction was observed for both bilayers when MgB2 becomes superconductor and is attributed to the opening of the superconducting gap. The present results show that MgB2 thin films could be suitable to implement superconducting spintronic at 30 K, which is not only relevant for future technological development but also relaxes experimental constraints related to low-temperature investigations. [ABSTRACT FROM AUTHOR]

Single crystalline Cu 7 Te 4 nanorods were obtained from a two-step synthesis route. The first step is the electrochemical deposition of self-standing tellurium nanorods on Pt-coated glass electrode in an ionic liquid electrolyte acting as a structuring solvent. Afterwards, soft chemical transformation in Cu 7 Te 4 is performed by immersing the Te-covered electrode in a Cu(II) solution in presence of ascorbic acid acting as reducer at room temperature and atmospheric pressure. Tellurium seems to undergo a reaction of disproportionation induced by the simultaneous presence of Cu(II) and Cu(I) into Te(IV) and Cu 7 Te 4 , which is supported by thermodynamic considerations. The copper telluride nanorods were analyzed by XRD, SEM-EDX, HRTEM-FFT/SAED, EELS and XPS that allowed to set the required parameters in terms of molar ratio of precursors in the bath to induce the targeted chemical reaction. The analyses highlight the obtention of single crystalline Cu 7 Te 4 with a homogeneous chemical composition along the nanorods. A detailed analysis of the microstructure shows the presence of stacking local defects, leading to curved nanostructures. [Display omitted] • Synthesis of single crystalline Cu 7 Te 4 nanorods with a homogeneous chemical composition along the nanorods. • Final step with a soft chemical transformation at room temperature and atmospheric pressure. • Reaction of disproportionation of Tellurium leading to Cu 7 Te 4 proven by thermodynamic calculations. • Detailed analysis of the microstructure highlighting the presence of stacking local defects. [ABSTRACT FROM AUTHOR]

Zinc tin nitride (ZnSnN 2 ) thin films have been deposited on glass and silicon substrates using a reactive co-sputtering process. Although the deposition temperature was limited to the room temperature, the films show a highly crystallization level and a strong preferred orientation in the [001] direction. The film composition, measured using energy dispersive X-ray spectroscopy and electron probe microanalysis, indicates a possible tin understoichiometry (or a zinc and a nitrogen overstoichiometry). As confirmed by transmission electron microscopy, the main oxygen contamination of the films results from oxidation of the grains boundaries after air exposure of the samples. X-ray photoelectron spectroscopy and Mössbauer spectrometry have been used to determine the chemical environment of atoms in the ZnSnN 2 crystals. Both methods confirm that Sn 4+ ions are bonded to nitrogen atoms and that the oxygen contamination results in the formation of Sn 2+ ions. Zinc tin nitride exhibit an electron mobility at room temperature close to 3.8 cm 2 V −1 s −1 and an optical band gap of 1.8 eV as measured independently from UV–visible spectrometry and ellipsometry. The results obtained in the present study confirm the suitability of ZnSnN 2 thin films as an Earth abundant material for absorber layer in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Heusler magnetic alloys offer a wide variety of electronic properties very promising for spintronics and magnonics. Some alloys exhibit a spin gap in their band structure at the Fermi energy, the so-called half-metal magnetic (HMM) behavior. This particular property leads to two very interesting properties for spintronics, i.e., fully polarized current together with ultra-low magnetic damping, two key points for spin-transfer-torque based devices. This Tutorial gives experimental details to grow and characterize Heusler Co2MnZ compounds in thin films (Z = Al, Si, Ga, Ge, Sn, Sb) by using molecular beam epitaxy in order to get the proper predicted electronic properties. A first part of this Tutorial is dedicated to control the stoichiometry as best as possible with some methods to test it. The chemical ordering within the lattice was examined by using electron diffraction during growth, regular x-ray diffraction, and scanning transmission electron microscopy. In particular, standard x-ray diffraction is carefully analyzed depending on the chemical ordering in the cubic cell and shown to be inefficient to distinguish several possible phases, on the contrary to electron microscopy. The electronic properties, i.e., magnetic moment, spin polarization, and magnetic damping were reviewed and discussed according to the stoichiometry of the films and also theoretical predictions. Polycrystalline films were also analyzed, and we show that the peculiar HMM properties are not destroyed, a good news for applications. A clear correlation between the spin polarization and the magnetic damping is experimentally demonstrated. At least, our study highlights the major role of stoichiometry on the expected properties. [ABSTRACT FROM AUTHOR]

Metallurgical and mechanical responses of alloys 16NiCrMo13 and 23MnCrMo5 to the addition of carbon and/or nitrogen were investigated. Diffusion profiles of these interstitial elements were established by atmospheric pressure carburizing, austenitic nitriding, and a sequence of carburizing and nitriding – the carbonitriding. All treatments were performed at 1173 K under CO-H 2 and/or NH 3 based atmospheres. After enrichment, each sample was (i) room-temperature oil-quenched and (ii) immersed in boiling nitrogen prior to (iii) the stress relief treatment. Cross-section hardness profiles were evaluated after each of these steps. Electron probe microanalysis (EPMA) allowed for the determination of both carbon and nitrogen diffusion profiles after quenching. In order to estimate the fraction of nitrides formed during the enrichment of the alloys, these measured profiles were employed in the simulation of local equilibrium at each evaluated position. This allowed for the computation of total solid solution interstitial content, which was expressed in atomic fraction. Plots of as-quenched hardness against the square root of the computed interstitial content, i.e. the sum of solution carbon and the remaining nitrogen, show the complementary character of these elements in determining the mechanical properties of the materials prior to stress relief treatment. Tempering of carbon-nitrogen martensite resulted in hardness drop to a lesser degree than the one measured on carbon martensite with equivalent interstitial content. In order to investigate this behavior, transmission electron microscopy (TEM) analyses were performed. Results showed the precipitation of two morphologies of Fe 16 N 2 in the nitrogen-rich case and image analysis confirmed the simulated fraction of nitrides. [ABSTRACT FROM AUTHOR]

[Display omitted] • Large 2D nanosheets of Bi 2 O 2 CO 3 are synthesized by discharges in liquids. • The growth is driven by the ledge mechanism assisted by ions at the cathode. • The liquid has no influence on the because of the formation of a metallic plasma. • The process is highly reproducible thanks to a chemical etching pretreatment. The growth of Bi 2 O 2 CO 3 nanosheets through nanosecond-pulsed discharges in liquid environments has been achieved by applying voltages slightly above the breakdown voltage. This growth process involves surface modification of the cathode electrode following pretreatment with chemical etching. Remarkably, the choice of liquid medium, whether water or liquid nitrogen, does not significantly affect the interaction between the electrodes and the metallic discharge that forms during the initial stages of synthesis. This process is template-free. The anisotropic growth of these two-dimensional objects is attributed to ion-assisted deposition via the ledge mechanism, supplemented by the presence of surface defects. Prior to the growth treatments, chemical etching is essential to enhance the probability of nanosheet formation from virtually zero to almost a hundred percent. This step is crucial in eliminating native oxide layers and exposing surface defects, which are present as parallel planes forming combs within polishing scratches. The detachment of nanosheets from the cathode and their release into the liquid is facilitated by the sweeping of the liquid-bubble interface, which breaks the nanosheets away from their substrate. As the electrodes undergo aging, nanosheets are formed by outward diffusion of bismuth and reaction with water and CO 2 in the air. By gaining a better understanding of this growth mechanism, exciting opportunities arise for the design and large-scale production of 2D nanostructures. [ABSTRACT FROM AUTHOR]

The characterization of the Grade 91 steel welded joints during creep is an important topic in the energy field. The microstructure in the Heat Affected Zone (HAZ) is complex and leads to premature creep failure in the InterCritical Heat Affected Zone (ICHAZ). For this purpose, interrupted creep tests are performed with industrial creep parameters (600 °C and 100 MPa) in order to follow the evolution of the ICHAZ microstructure. Employed characterization techniques include hardness mapping, electron microscopy (SEM and TEM), electron diffraction (EBSD) and spectroscopy (EDS) analyses. The results provide quantitative evolution of the different microstructure factors during the creep test until the fracture: the disappearance of fine precipitates, substructure and solid solution elements. This change accelerates the plastic deformation, favouring the recovery/recrystallization of the ICHAZ leading to equiaxed fine grains microstructure. [ABSTRACT FROM AUTHOR]

An electrochemical catalyst based on Au nanoparticles dispersed in an yttria-stabilized zirconia (YSZ) matrix was prepared by reactive cosputtering of zirconium-yttrium and Au targets on a K-βAl2O3 solid electrolyte. The Au/YSZ catalyst film deposited on K-βAl2O3 was found to be active in the partial oxidation of methanol with a high selectivity toward methyl formate. This configuration allowed to electrochemically promote a highly dispersed Au catalyst by K+ ions and allowed to decrease the amount of metal used in the solid electrolyte cell. The back-spillover of K+ ions sharply increased the H2 and HCOOCH3 production rates up to more than 9 and 5 times, respectively. A number of experiments confirmed that the observed electro-promotional effect did not depend on the rate of K+ supply nor on the operation mode (galvanostatic or potentiostatic) and only depended on the promoter coverage (total applied charge). The stability of the Au-YSZ catalyst film under the explored conditions was also verified. [ABSTRACT FROM AUTHOR]

Aspects on the phase stability and mechanical properties of nitrogen deficient (Ti0.54Al0.46)Ny alloys were investigated. Solid solution alloys of (Ti,Al)N were grown by cathodic arc deposition. The kinetic energy of the impinging ions was altered by varying the substrate bias voltage from –30V to –80 V. Films deposited with a high bias value of –80V showed larger lattice parameter, finer columnar structure, and higher compressive residual stress resulting in higher hardness than films biased at –30V when comparing their as-deposited states. At elevated temperatures, the presence of nitrogen vacancies and point defects (anti-sites and self-interstitials generated by the ion bombardment during coating deposition) in (Ti0.54Al0.46)N0.87 influence the driving force for phase separation. Highly biased nitrogen deficient films have point defects with higher stability during annealing, which cause a delay of the release of the stored lattice strain energy and then accelerates the decomposition tendencies to thermodynamically stable c-TiN and w-AlN. Low biased nitrogen deficient films have retarded phase transformation to w-AlN, which results in the prolongment of age hardening effect up to 1100 °C, i.e., the highest reported temperature for Ti-Al-N material system. Our study points out the role of vacancies and point defects in engineering thin films with enhanced thermal stability and mechanical properties for high temperature hard coating applications. [ABSTRACT FROM AUTHOR]

Abstract: Micro-gap discharges created in heptane between two platinum pin-electrodes produce platinum particles embedded in an amorphous carbon matrix which exhibits a short-range order. The platinum particles can be sorted by size. The largest ones (>100 nm in diameter) are created by emission of droplets from the liquid pool formed when the discharge hits the electrode surface. They are submitted to high stress levels by fast thermal quenching. The smallest ones (<5 nm) are synthesized in the plasma. Nanoparticles with diameters ranging from 10 to 20 nm have structure defects and are synthesized in post-discharge where huge temperature gradients exist. The short-range order observed in carbon extends typically over 3 nm, and it is observed by high-resolution transmission electron microscopy. This ordered structure of carbon (and a fortiori sp 3 bonds which are identified by FTIR analyses) is clearly visible around the smallest nanoparticles and it is likely formed at the same location, i.e. in the plasma. [Copyright &y& Elsevier]

Abstract: In the Sinnamary Estuary (French Guiana), a dense red biofilm grows on flooded surfaces. In order to characterize the iron oxides in this biofilm and to establish the nature of secondary minerals formed after anaerobic incubation, we conducted solid analysis and performed batch incubations. Elemental analysis indicated a major amount of iron as inorganic compartment along with organic matter. Solid analysis showed the presence of two ferric oxides ferrihydrite and lepidocrocite. Bacteria were abundant and represented more than 1011 cellsg−1 of dry weight among which iron reducers were revealed. Optical and electronic microscopy analysis revealed than the bacteria were in close vicinity of the iron oxides. After anaerobic incubations with exogenous electron donors, the biofilm''s ferric material was reduced into green rust, a FeII–FeIII layered double hydroxide. This green rust remained stable for several years. From this study and previous reports, we suggest that ferruginous biofilms should be considered as a favorable location for GR biomineralization when redox conditions and electron donors availability are gathered. [Copyright &y& Elsevier]

Abstract: We have studied bimetallic Ni–Ag (Ni + Ag = 1 wt%) catalysts supported on crystallized silica and prepared by aqueous chemical reduction with hydrazine at 353 K. Two protocols of reduction were used. Prepared catalysts were characterized by means of XRD, TEM, STEM, H2 chemisorption and H2-TPD. Their catalytic activity was studied in the gas-phase hydrogenation of benzene. The most important feature of the results obtained is the synergistic effect between Ni and Ag which led to improvement of dispersion and reactivity of nickel in the presence silver for precipitated catalysts. Silver is inactive in the test-reaction. Precipitated bimetallic catalysts give rise to total conversion from 373 K, a temperature at which conversion hardly reaches 30% for the impregnated catalysts. Dispersion and activity pass through a maximum of monotonically decrease with precipitated and impregnated catalysts, respectively. Deactivation was observed for bimetallic catalysts, particularly with precipitated samples. These results could be explained by the mechanism of metal reduction in the hydrazine media. As a result, various Ni–Ag species formed where Ni and Ag phases were separated clusters or interacted as heteroatomic groupings on the carrier surface. These grouping would be responsible of the high performances of the precipitated catalysts. [Copyright &y& Elsevier]

Abstract: In this paper, we report the use of oil/water (O/W) fluorinated emulsions to design macroporous–mesoporous silica with a well-ordered array of mesopores. The emulsion is constituted of fluorocarbon droplets stabilized by the fluorinated surfactant molecules and dispersed in an O/W fluorinated microemulsion. A macroporous texture is clearly evidenced by SEM. The size of the macropores varies from 1.0 to 3.0μm. SAXS patterns of the materials and TEM experiments show that the mesoporous network adopts a hexagonal arrangement. A type IV isotherm is obtained by nitrogen adsorption–desorption analysis. The mesopore size distribution is narrow and centered on about 7.5nm. We also proposed a mechanism to explain the formation of these hierarchically structured macroporous–mesoporous silicas. [Copyright &y& Elsevier]

Abstract: SnCl2 was reduced in the presence of graphite by t-BuONa-activated NaH. The resulting (tin/graphite)-based system was composed of nanosized tin particles deposited on the graphite surface and of free tin aggregates. Lithium electrochemical insertion occurs in graphite and in tin. A reversible specific charge of 500mAh/g is found stable upon cycling. This value is lower than the maximum theoretical one (650mAh/g) assuming a Sn/12C molar composition and the formation of the highest lithium content alloy Li22Sn5. It is suggested that the part of tin responsible for the stable reversible capacity is the one bound to graphite. To the contrary, free tin aggregates could contribute to a capacity which decreases upon cycling in connection with the volume changes accompanying lithium insertion/extraction in/out of these aggregates. [Copyright &y& Elsevier]

Abstract: Transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS) was used to investigate the coagulation of natural organic matter with a ferric salt. Jar-test experiments were first conducted with a reconstituted water containing either synthetic or natural extracts of humic substances, and then with a raw water from Moselle River (France). The characterization of the freeze-dried coagulated sediment by EELS in the 250–450eV range, showed that Fe-coagulant species predominantly associate with the carboxylic groups of organic matter, and that this interaction is accompanied by a release of previously complexed calcium ions. The variation of Fe/C elemental ratio with iron concentration provides insightful information into the coagulation mechanism of humic substances. At acid pH, Fe/C remains close to 3 over the whole range of iron concentrations investigated, while a much lower atomic ratio is expected from the value of optimal coagulant dosage. This suggests that a charge neutralization/complexation mechanism is responsible for the removal of humic colloids, the aggregates being formed with both iron-coagulated and proton-neutralized organic compounds. At pH 8, the decrease in Fe/C around optimal coagulant concentration is interpreted as a bridging of stretched humic macromolecules by Fe-hydrolyzed species. Aggregation would then result from a competition between reconformation of humic chains around coagulant species and collision of destabilized humic material. EELS also enabled a fingerpriting of natural organic substances contained in the iron-coagulated surface water, N/C elemental analyses revealing that humic colloids are removed prior to proteinic compounds. [Copyright &y& Elsevier]

Abstract: Group 15 element–graphite M/C composites were prepared by reduction of MCl x chlorides (AsCl3, SbCl5, BiCl3) by KC8 in THF. Arsenic and antimony were both amorphous: antimony appeared as a film-like material, formed of aggregated nano-sized particles covering parts of the graphite surface; arsenic was present as large graphite supported particles. On the contrary, bismuth was present as crystalline metal nanoparticles distributed on the graphite surface. Amorphous As and Sb–graphite composites displayed stable reversible capacities of 310 and 420mAh/g, respectively while that of crystalline Bi–graphite materials decreased regularly upon cycling. Although these practical capacities were lower than the expected theoretical ones corresponding to the formation of Li3M compounds, it appeared that, in the presence of graphite, amorphous solids exhibiting a (partly) covalent character like As and Sb gave better long life cycling properties than the crystalline and metallic bismuth. It was very likely that our one step synthesis could generate bonds between graphite and (partly) covalent solids reducing consequently the volume expansion effects occurring during cycling. On the contrary, metallic solids like bismuth that were not inclined to bond with graphite behave, upon cycling, as corresponding massive metals. [Copyright &y& Elsevier]

The nature of trace element carriers contained in sewage and combined sewer overflow (CSO) was investigated by TEM-EDX-Electron diffraction and SEM-EDX. During dry weather, chalcophile elements were found to accumulate in sewer sediments as early diagenetic sulfide phases. The sulfurization of some metal alloys was also evidenced. Other heavy metal carriers detected in sewage include metal alloys, some iron oxihydroxide phases and neoformed phosphate minerals such as anapaite. During rain events, the detailed characterization of individual mineral species allowed to differentiate the contributions from various specific sources. Metal plating particles, barite from automobile brake, or rare earth oxides from catalytic exhaust pipes, originate from road runoff, whereas PbSn alloys and lead carbonates are attributed to zinc-works from roofs and paint from building siding. Soil contribution can be traced by the presence of clay minerals, iron oxihydroxides, zircons and rare earth phosphates. However, the most abundant heavy metal carriers in CSO samples were the sulfide particles eroded from sewer sediments. The evolution of relative abundances of trace element carriers during a single storm event, suggests that the pollution due to the “first flush” effect principally results from the sewer stock of sulfides and previously deposited metal alloys, rather than from urban surface runoff. [Copyright &y& Elsevier]

Compressing together divided barium and poly(para-phenylene) results in the intercalation of the metal into the polymer. Electron energy loss spectroscopy (EELS) analysis indicates that an intercalation level of 0.24 barium ions per phenyl unit can be achieved and that the oxidation state of the intercalated barium is rather +2 (Ba2+). Both transmission electron microscopy and electron spin resonance studies show that the distribution of the intercalant in the polymer is very inhomogeneous. [Copyright &y& Elsevier]

Krypton adsorption isotherms on multiwalled carbon nanotubes have been measured at 77 K and compared to those obtained under the same conditions on exfoliated graphite. The results are discussed in the light of the nanotube morphology, as determined by transmission electron microscopy and electron energy loss spectroscopy. The isotherms exhibit two steps representative of successive monomolecular layer condensations on the external walls of nanotubes, instead of five steps on graphite. The monolayer condensation pressures are higher than those observed with graphite, which probably limits their number at krypton bulk condensation pressure. Near the completion of the first condensed layer, a second transition towards a phase of higher density occurs, the nature of which is discussed. [Copyright &y& Elsevier]

Strain modulation during a two-way shape memory effect (TWSME) in a sputtered nitinol NiTi is used to reliably induce and switch by 90° a uniaxial magnetic anisotropy of a 20 nm thick Ni film during the thermal cycle from 300 K to 400 K. NiTi strain and its distribution are carefully measured by digital image correlation during tensile prestrain and subsequent temperature cycles in order to compare with Ni strain extracted from the magnetometry measurement and from transmission electron microscopy. In a NiTi/Ni bilayer, a variation of 2.7% strain in NiTi during the TWSME generates 1.3% strain in Ni, which results in a transition from −2 × 104 J/m3 in-plane magnetic anisotropy to +1 × 105 J/m3. Such a composite system offers a way to timely ease writability while maintaining high thermal stability at rest in magnetic media. [ABSTRACT FROM AUTHOR]

Spin-polarization and magnetic damping are measured for several polycrystalline films with each of them being made of a different single Co2Mn-based Heusler compound. As several epitaxial Co2Mn-based Heusler compounds are shown to be half-metal magnetic materials with full spin-polarization and ultralow magnetic damping, we explore here these properties but in polycrystalline films. Co2MnSi, Co2MnGe, and Co2MnGa thin films were grown on glass substrates and analyzed in situ by electron diffraction and spin-resolved photoemission and ex situ by transmission electron microscopy and ferromagnetic resonance. Despite the polycrystalline state of the films, they still exhibit high spin polarizations and very low magnetic damping coefficients. The latter are at least of the same order as the best epitaxial films using regular ferromagnetic materials. The key point to achieve such properties is to control the Heusler stoichiometry as best as possible. [ABSTRACT FROM AUTHOR]

We report the formation of large and highly twinned dendrites of the Al 13 Fe 4 approximant phase embedded in an fcc Al-rich matrix. Using a rapid cooling technique, the approximant appears as a 10-fold dendrite. Within each arm, all grains share a common [010] direction. The grain distributions within the arm are quite complex and a single dendrite arm can contain up to four different orientations. Using several techniques, including Electron Back-Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM), it has been possible to identify three types of twins, namely {100}, {001} and {20 1 ̄ } twins. From these observations and previous reports, we propose a growth mechanism to explain the formation of such specific 10-fold motifs. It corresponds to the heteroepitaxial growth of the Al 13 Fe 4 approximant from a well-facetted decagonal Al–Fe quasicrystalline seed. [Display omitted] • Growth of Al 13 Fe 4 approximant precipitates in an Al fcc matrix with 10-fold dendritic structure. • Repetitive occurrence of three types of twins to maintain rapid dendrite growth. • Evidence for grain orientation relationships among symmetrically opposite dendrite. • Heteroepitaxial growth of a decagonal approximant on a quasicrystalline template. [ABSTRACT FROM AUTHOR]

The influence of Si concentrations on AlTiN and AlTiCrN coatings deposited by PVD has been investigated by using high-resolution characterization techniques: TEM, Dynamic SIMS, Atom Probe Tomography (APT) analyses and nano hardness measurements. First, investigations focus on crystallographic phase stability, microstructural observations and micromechanical studies to understand the effect of the Si addition on these two nitride coatings. Second, the oxidation mechanisms and the kinetics of oxide growth at 950 °C for various durations are examined. Results indicate that the addition of Si introduces high compressive stresses in both coating groups, reaching values in the range of − 6 GPa. However, the behavior of Si content differs for AlTiN coatings with and without chromium. In AlTiSiN coatings, increasing Si addition leads to reduce residual stresses, while no significant change is observed for AlTiCrSiN coatings. This stress evolution is associated with a decrease in crystallinity density of the TiAlN coatings due to Si addition, but this structural phenomenon is not observed when Si is added to the quaternary metallic coatings TiAlCrN. Si content also influences the nanohardness, but the variation among coating is not substantial, with values around 34 + /− 2 GPa, and an elastic-modulus around 443 + /− 40 GPa. Regarding oxidation resistance at 950 °C, the addition of Si in AlTiN coating results in the formation of an external alumina oxide layer and beneath it, a nanometer sized TiO 2 anatase crystallites layer. After the growth of this bi-layer oxide scale, the inward cationic diffusion of the oxygen is very significantly reduced, and it can explain its high oxidation resistance. In contrast, for AlTiCrSiN coatings, the oxide scale morphology is different, consisting of a pure TiO 2 rutile outer layer, followed by an Al-rich oxide and a mixed oxide region of (AlCr) 2 O 3 with small islands of TiO 2. The growth of this last oxide scale shows a regular increase over time, primarily driven by inward oxygen diffusion at the nitride coating interface. [Display omitted] • Cr allows better stability of the crystallinity structure when the addition of Si is done. • AlTiN coating can only be resistant against oxidation at 950 °C if it contains an addition of Si between 1 and 5 at%. • AlTiSiN oxide layer comprises an outer Al 2 O 3 layer and an inner TiO 2 layer containing SiN/O at the grain boundaries. • AlTiCrSiN oxide layer at 950 °C consists of TiO 2 / Al(Cr) 2 O 3 / (Cr,Al) 2 O 3 -TiO 2 -Si from the surface to the nitride interface. • Growth of oxide scale on AlTiCrSiN coatings is controlled by the inward oxygen diffusion until the nitride interface. [ABSTRACT FROM AUTHOR]

A direct band gap of 1.6 eV has been identified in wurtzite CoO thin films, which matches the required value to achieve a theoretically high conversion efficiency solar cell. Its p-type conduction has been determined and an intense sub-gap absorption between 0.7 and 1.1 eV has been observed. [ABSTRACT FROM AUTHOR]

In the present work, ultrafine-grained Al-Zn-Mg alloy produced by high energy ball milling and Spark Plasma Sintering was synthesized. The Hall-Petch strengthening due to grain refinement (about 150 nm) is preserved and the Orowan's effect attributed to the presence of the hardening phase η ’ is obtained in a single-step during the sintering. Maximum compression stresses as high as 736 MPa and 830 MPa were reached in quasistatic and dynamic conditions respectively. Hardness was increased from 124 HV5 for a consolidated coarse grained material to 196 HV for a consolidated ultrafine-grained (UFG) material. The mechanical properties obtained in this study were all superior to the ones of the reference AA7020-T651. [ABSTRACT FROM AUTHOR]

Previous study by Queudet et al. [1] showed that powder metallurgy allows to produce high strength ultrafine-grained (UFG) Al-Zn-Mg alloys which contains both η ' and η phases. This present work investigates the effects of solid solution treatment followed by quenching (W temper) and subsequent ageing to obtain theoretical T6 tempered UFG material. TEM analyses revealed the presence of GP zones and metastable η ' phase in W tempered UFG material. Compared to as-fabricated material, quenching conferred to the alloy higher maximum stress of 785 MPa and stabilized plastic flow. Further ageing resulted in over-aged alloy containing the η phase, inducing lower hardness and compressive stress. TEM observations showed that variant η 2 which grows from η ' is delimited by previous GP-II zones. [ABSTRACT FROM AUTHOR]

A joint experimental and theoretical study is presented for the electronic structures of copper oxides including Cu2O, CuO, and the metastable mixed-valence oxide Cu4O3. The optical band gap is determined by experimental optical absorption coefficient, and the electronic structure in valence and conduction bands is probed by photoemission and electron energy loss spectroscopies, respectively. The experimental results are compared with many-body G W calculations utilizing an additional on-site potential for d -orbital energies that facilitates tractable and predictive computations. The side-by-side comparison between the three oxides, including a band insulator (Cu2O) and two Mott/charge-transfer insulators (CuO, Cu4O3) leads to a consistent picture for the optical and band-structure properties of the Cu oxides, strongly supporting indirect band gaps of about 1.2 and 0.8 eV in CuO and Cu4O3, respectively. This comparison also points towards surface oxidation and reduction effects that can complicate the interpretation of the photoemission spectra. [ABSTRACT FROM AUTHOR]

Oxidation by a micro-post-discharge at atmospheric pressure of thin films of ruthenium deposited on fused silica by pressure-modulated magnetron sputtering is studied. Single-crystalline RuO 2 nanowires are obtained for the first time with a diffusion process over large areas. Nanowires grow typically at temperatures below 550–600 K, provided the level of stress is high enough to fragment grains in sub-grains with sizes between 30 and 50 nm. Because of the alternation of dense and porous layers forming the coating, inward diffusion of vacancies leads to no patent Kirkendall's effect, pores being distributed over the whole coating thickness and not mainly at the interface with the substrate. The centre of the treatment being heated at temperatures higher than 900 K, gaseous RuO 4 is formed, leading to an evaporated area. At its edge, a ring of microcrystals is formed, likely by a CVD mechanism. [ABSTRACT FROM AUTHOR]

Oxidizing thin films made of Fe–Cu alloy with an Ar–O 2 micro-afterglow operated at atmospheric pressure shows remarkable growth processes. The presence of iron in copper up to about 50% leads to the synthesis of CuO nanostructures (nanowalls, nanotowers and nanowires). Nanotowers show the presence of an amorphous phase trapped between crystalline domains. Beyond 50%, Fe 2 O 3 iron nanoblades are also found. CuO nanowires as small as 5 nm in diameter can be synthesized. Thanks to the presence of patterned domains induced by buckling, it was possible to show that the stress level decreases when the iron content in the alloy increases. Iron blades grow from the inner Fe 2 O 3 layer through the overlying CuO if it is thin enough. [ABSTRACT FROM AUTHOR]

Synthesized Fe@FeOx nanoparticles (NPs) were fully characterized by spectroscopic techniques and (scanning) transmission electron microscopy to resolve the presence of a Fe(OH) 2 -like phase. The different phases detected in the core–shell nanostructure of these NPs were corroborated by Mössbauer and X-ray photoelectron spectroscopies. Metallic iron (Fe0), ferrous (FeII) hydroxide, magnetite (FeIII 2 FeIIO 4), and a top layer of ferric (FeIII) oxide were identified. Interestingly, ferrous hydroxide reacted with Pd2+ aq upon coating of the supporting core–shell material when Pd was added to produce Fe@FeOx/Pd NPs. [Display omitted] • The core-shell structure of nano-zerovalent Fe was characterized by TEM, XPS and TMS. • Fe(OH) 2 was identified by Mössbauer spectrometry in the shell of nano-zerovalent iron. • Fe0 proportion and Pd0 thickness were respectively estimated by TMS and XPS. • Nanoparticle modelization was consistent with interpretation of the XPS and TMS data. [ABSTRACT FROM AUTHOR]

In this work, a novel system for the hot wall evaporation of MoO 3 in a horizontal furnace and at low vacuum atmosphere was settled. Pure MoO 3 material was obtained without the presence of other phases and with a strong preferential orientation, as revealed by electron microscopy, micro-Raman spectroscopy and x-ray diffraction. Photoluminescence and Raman spectra were measured as a function of temperature. As a result, the first-order temperature coefficient of the fifteen measured vibrational modes is reported and compared with the scarce literature data available. The relation of these coefficients with the thermal expansion coefficient is discussed in the framework of the Grüneisen model. Moreover, for the first time, the temperature dependence of the different contributions of photoluminescence spectra for MoO 3 is reported, and an anomalous increase in PL intensity of all transitions is observed in the range of 40–140 K, followed by a normal quenching at high temperatures. The Shibata model was used to interpret the origin of this anomalous effect. • A horizontal hot wall evaporation system for MoO 3 at low vacuum was settled up. • First-order temperature coefficients of MoO 3 vibrational modes were reported. • MoO 3 photoluminescence spectra from 12 to 300 K was measured and studied. • Near band emission temperature dependence is quantified for MoO 3. • Negative thermal quenching of the luminescence was observed and modeled. [ABSTRACT FROM AUTHOR]

Amorphous layer up to 20 μ m thick were obtained from bulk diffusion couples between pure copper and Zircaloy 4 after isothermal treatment at 900 ∘ C and slow cooling to room temperature. It has been shown that the Cu-rich liquid exhibit a low mobility and high viscosity, and that the asymetrical diffusion behavior of Zr and Cu together with the interfacial reaction rate constrain the liquid layer and allows to avoid nucleation of intermetallic compounds up to 45 minutes holding time. The Cu-rich liquid layer forming at the holding temperature is stable and grows until another liquid, richer in Zr, appears. [ABSTRACT FROM AUTHOR]

Abstract: We report on the synthesis and natural occurrence of hexagonal-pyramidal graphite hillocks on graphite crystal substrates. Synthetic hillocks were obtained from flexible graphite sheets and highly oriented pyrolytic graphite via argon plasma etching in a standard helicon configuration reactor. High-resolution transmission electron microscopy and electron diffraction suggest these hillocks have a high degree of perfection. Their size distribution ranges from 50 to 800nm across and up to 1μm along the c-axis. As a reference, natural crystals from Tanzania exhibiting the same morphology are presented. Also, a formation mechanism of the plasma-synthesized structures by an etching process is detailed. This new type of vertically aligned carbon nano- and microstructures presents a peculiar geometry including nano-arches at the graphite edge planes which induce a strong resistance to the plasma etching. [Copyright &y& Elsevier]