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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]

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]

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]

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]

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]

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]

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]

Carbon materials including carbon nanoparticles, such as nanographite, graphene and graphenic materials, and carbon nanotubes are known to be highly hydrophobic. Oxidation treatments are widely used as the best methods to improve their affinity in a liquid medium or a polymer matrix so that they can be dispersed, handled and processed. Here, we have applied eight different oxidation treatments in order to graft oxygen-containing functional groups at the surface of polyhedral graphitic particles synthesized by arc discharge from graphite, also called astralenes. The used functionalization approaches include both standard chemical attack by strong oxidants and radical functionalization of the sp2 network by direct C=C bond opening. Commonly efficient functionalization methods were unsuccessful to functionalize astralenes while radicals generated from arylhydrazine could lead to functionalization of the outer surface of astralenes. The occurrence of functionalization could be shown by TGA coupled with MS and XPS. The reported method represents the first example of functionalization of astralenes. The efficiency of the applied functionalization methods is discussed considering the chemical reactivity of different carbon nanomaterials including graphene and carbon nanotubes. [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]

The valorization of precipitated carbonates is envisaged for industrial gases treatment in order to avoid waste disposal in landfills. In this paper, the valorization focuses on the desulfurization of fumes by carbonate materials through the semi-wet way. Three carbonated materials are tested: two industrial residues and a limestone of reference. Their composition and size distribution are comparable. Infrared spectroscopy and electron microscopy are used to identify the evolution of mineral and surface composition. Multi-scale study highlights different behaviors between carbonate samples. Laboratory dissolution tests reveal that two industrial residues were clearly more soluble and have a final dissolution degree ≥90 %. The same carbonate materials were then tested at pilot scale. The unit can treat around 1,000–2,000 m 3/h of industrial fumes enriched in SO 2 in semi-wet desulfurization process. Injection of H 2O was tested at constant temperature and Ca/S ratios to optimize the process. Origin of CaCO 3 particles and hydration properties appear as the main factors controlling desulfurization efficiency. Calcium carbonates precipitated in brines show higher efficiency in SO 2 conversion rate (40–70 %) in comparison with other carbonate materials in semi-wet way, i.e. limestone or leached wastes (25–35 %). The combination of high dissolution rate of CaCO 3 particles with surface hydration appears as responsible for this performance. [ABSTRACT FROM AUTHOR]

To assess the effect of polymeric substances on the biomineralization and stabilization of green rust (GR), the effect of two organic polymers on the transformation of lepidocrocite (γ-FeOOH) to GR vs. magnetite in presence ofShewanella putrefacienswas investigated. These two polymers, generally used as flocculants, are polyacrylic acid (PAA), which bears negatively charged carboxylic groups at neutral pH and is expected to react with cationic hydrolyzed iron species, and polyacrylamide (PAM), which is a neutral polymer that may develop hydrogen bonds with iron nanocolloids. The bioreduction of lepidocrocite byS. putrefacienswas performed under conditions known to yield either magnetite or GR. Each operational condition of interest was investigated with various polymer concentrations from 0.6 to 60 mg g−1Fe (10 to 1000 mg l−1). The final product was characterized using X-ray diffraction and electronic microscopy. The results showed that the formation of GR is favored, with respect to magnetite, to a lesser extent with PAM than with PAA. These results indicated that polymers influence the chemical stability of GR and/or guide the route of biomineralization. Polymer properties, in addition to silica and phosphate concentrations, are then critical parameters that control the secondary iron mineral biomineralization from iron-reducing bacteria. Supplemental materials are available for this article. Go to the publisher's online edition ofGeomicrobiology Journalto view the supplemental file. [ABSTRACT FROM AUTHOR]

The nature of the interaction between iron oxyhydroxide compounds and natural organic matter (NOM) may take various forms and is still a matter of debate. It is an important field to understand, especially for water treatment applications and for the knowledge of iron transport in the environment. The nature of association reached between iron oligomeric species and NOM is here investigated using Mössbauer spectroscopy and electron energy-loss spectroscopy (EELS) at the Fe-L3 edge. Raw water NOM taken from Moselle River (France), natural humic substances extracted from the riverine suspended matter, and a synthesized humic-like substance, are coagulated with iron nitrate according to a jar-test procedure. The results from Mössbauer spectroscopy indicate that Fe is present in an octahedral coordination environment, which is consistent with prior X-ray absorption spectroscopy reported in the literature. The areas beneath the peaks (Fe L3 edge) and the peak shapes of EELS spectra differ according to the origin of the organic matter, suggesting that various types of Fe populations can be distinguished using the EELS technique. Combining the selectivity of both Mössbauer spectroscopy for identifying trace, poorly crystalline Fe solids, oxidation state and of EELS for being able to characterize the population of Fe based on L-edge spectra, appears promising for characterizing Fe in systems containing NOM. [ABSTRACT FROM AUTHOR]

Analytical scanning and transmission electron microscopy, sequential chemical extraction, and pyrolysis-gas chromatography on solvent-extractable organic matter are used to provide both direct and indirect speciation of heavy metals and organic matter in sewage-suspended solids and in biofilms taken from an urban sewer in an emerging country. Compared to developed countries where the domestic activities represent the main source of heavy metal pollution in wastewater, the combined sewer system of an emerging country also integrates significant contributions originating from the private drinking water supply system (Zn, Cu, Cr, and Ni), industrial discharges (Cu, Mn), and road dust transported by street washing (Pb). The relative importance of those sources changes drastically over time as evidenced by the difference in metal levels recorded between weekday and weekend effluents. Nevertheless, sewer biofilms are found to provide a good averaging of contaminant loads and they can be used as environmental archives. The speciation study reveals the predominance of neoformed minerals such as sulfides and phosphates and highlights the strong biogeochemical dynamics that takes place within the sewer system. Electron microscope observations of heavy metal-bearing phases proved to be necessary to provide a consistent interpretation of chemical extraction results. The molecular characterization of the solvent-extractable organic matter from biofilms reveals the presence of classical fingerprints of domestic activity such as fecal sterols and detergents but also confirms a major contribution of petroleum by-products consistent with a traffic-related pollution. [ABSTRACT FROM AUTHOR]

To investigate the consequences of acidification and metal accumulation on the biology of aquatic bryophytes, the acid-tolerant liverwort Scapania undulata (L.) Dum. and the acid-sensitive moss Rhynchostegium riparioides (Hedw.) Cardot were transplanted from one stream to two other streams of differing acidity (pH 5.20 and 6.38). The bryophytes were collected in a circumneutral (pH 6.57) stream in the Vosges Mountains. Metal accumulation was semi-quantitatively measured in shoots by energy dispersive TEM X-ray spectroscopy (EDXS). After 1 month, the two species remained green without alteration signs. Although no marked ultrastructural damage was observed in either species, some cells seemed to be necrotic, with flattened chloroplasts, in R. riparioides. Lipid droplet accumulation was observed in some leaf cells of S.undulata when transplanted to the most acidic stream. Metal was mostly localised in the cell wall, and was only sometimes detected in small vacuoles. Under acidic conditions, R. riparioides showed the highest relative amount of Al and the lowest amount of Fe, whereas the acid-tolerant bryophyte species S. undulata contained more Fe and less Al. The capability to limit the uptake of metals into the cytoplasm varies according to the bryophyte species. This could be an explanation of the tolerance of S. undulata to acidification. [ABSTRACT FROM AUTHOR]

Supported mesostructured thin films are of major importance for applications in optical, electrochemical and sensing devices. However, good performance is restricted to mesostructured phases ensuring good accessibility from the film surface, which would be straightforward with cylindrical pores oriented normal to the underlying support, but this remains challenging. Here, we demonstrate that electrochemistry is likely to induce self-assembly of surfactant-templated (organo)silica thin films on various conducting supports, homogeneously over wide areas. The method involves the application of a suitable cathodic potential to an electrode immersed in a surfactant-containing hydrolysed sol solution to generate the hydroxyl ions that are necessary to catalyse polycondensation of the precursors and self-assembly of hexagonally packed one-dimensional channels that grow perpendicularly to the electrode surface. The method is compatible with controlled and localized deposition on heterogeneous supports, opening the way to electrochemically driven nanolithography for designing complex patterns of widely accessible mesostructured materials. [ABSTRACT FROM AUTHOR]

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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]

Hydroxysulphate green rust $$ {\left\{ {{\text{GR}}{\left( {{\text{SO}}^{{2 - }}_{4} } \right)}} \right\}} $$ species were precipitated in the presence of various anions. $$ {\text{GR}}{\left( {{\text{SO}}^{{2 - }}_{4} } \right)} $$ is stable at ∼pH 7 and is transformed into a mixture of magnetite and ferrous hydroxide when the pH raised at ∼12. In the presence of carbonate species, $$ {\text{GR}}{\left( {{\text{SO}}^{{2 - }}_{4} } \right)} $$ is partially transformed into a mixture of magnetite and siderite at ∼pH 8.5. This transformation is stopped when silicate anions are present in the solution. As already observed for phosphate anions, the adsorption of silicate anions on the lateral faces of the $$ {\text{GR}}{\left( {{\text{SO}}^{{2 - }}_{4} } \right)} $$ crystals may explain this stabilization effect. Sulphate anions are easily exchanged by carbonate species at ∼pH 10.5. In contrast, anionic exchange between sulphate and phosphate anions was not observed. [ABSTRACT FROM AUTHOR]

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]

This paper reports the preparation conditions and structure characteristics of Al-Cr-Fe very thin films (10-30 nm) obtained by the flash evaporation technique. The films are either amorphous or crystallized, depending on the thickness of the sample and temperature of the substrate. Annealing of amorphous films leads to crystallization of intermetallic phases that are all linked with quasicrystals. In particular, we have identified by transmission electron microscopy the following structures: body-centered-cubic (bcc) γ-brass phase, monoclinic λ-Al13(Cr,Fe)4 phase, and orthorhombic O1-phase, all of them already observed in this system, together with four new structures, i.e., a face-centered-cubic (fcc) γ-brass phase (superstructure of the bcc phase), monoclinic λ′-phase (related to the λ-phase) and two orthorhombic phases (1/1/; 1/1) and (1/0; 2/1) approximants of the decagonal phase). In this study, we point out the occurrence of twin defects of the λ-Al13(Cr,Fe)4 phase. Films prepared directly in the crystalline state comprise the O1 approximant. Electron energy loss spectroscopy measurements show that all films are not oxidized except for the presence of a native oxide layer that forms in ambient atmosphere with a thickness that cannot exceed 0.3 nm. Optical properties were investigated and show that films need to be large enough (>30 nm) to reproduce the properties of bulk alloys. Finally, contact angle wetting measurements reveal that the presence of such films on a substrate, even at very low thickness, considerably decreases the wetting behavior by water. [ABSTRACT FROM AUTHOR]

We introduce a new method for the synthesis of Al-Ni nanosized particles. After partial oxidation, this technique is able to produce ultrafine sub-nanometric nickel clusters dispersed with an amorphous aluminium oxide. Such clusters consist of about 15 nickel atoms which exhibit discrete electronic energy levels and superparamagnetism. A very significant enhancement of the catalytic properties is observed. We expect that division of metals down to such a reduced scale will lead us to new properties and to a technological breakthrough since upscaling this method to industrial production rate is straightforward. [ABSTRACT FROM AUTHOR]

Finely dispersed Ni powders were obtained after chemical reduction of Ni(II) salts by activated sodium hydride in organic solvents. This process allows one to prepare particles in the nanometre range. The particles with sizes smaller than 4 nm were found to be hcp whereas larger particles were fcc. To the best of our knowledge, this is the first observation that unsupported Ni powder may crystallize in the hcp system and that the phase stability of this metallic element is particle size dependent. [ABSTRACT FROM AUTHOR]

Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011Si//0001Al2Si2Eu, 111Si//6 7 ¯ 10Al2Si2Eu and 011Si//6 7 ¯ 10Al2Si2Eu. No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure. [ABSTRACT FROM AUTHOR]