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We report the electronic structure of two metal-organic frameworks (MOFs) with copper paddle wheel nodes connected by a N2(C2H4)3 (DABCO) ligand with accessible nitrogen lone pairs. The coordination is predicted, from first-principles density functional theory, to enable electronic pathways that could facilitate charge carrier mobility. Calculated frontier crystal orbitals indicate extended electronic communication in DMOF-1, but not in MOF-649. This feature is confirmed by bandstructure calculations and effective masses of the valence band egde. We explain the origin of the frontier orbitals of both MOFs based on the energy and symmetry alignment of the underlying building blocks. The effects of doping on the bandstructure of MOF-649 are considered. Our findings highlight DMOF-1 as a potential semiconductor with 1D charge carrier mobility along the framework

Graphene/polymer composites can be spun into fibers with remarkable mechanical, thermal and electrical properties, but few studies have considered requirements for the pilot-scale production of such fibers using commercially available graphene nanoplatelets (GnP). To address this limitation, we fabricated melt-spun polyamide 6 (PA6) multifilament yarns in which 3% or 5% (w/w) GnP was incorporated into the PA6 matrix by melt compounding during the initial process step. We tested a range of melt-spinning process parameters and analyzed the properties of the resulting fibers in detail. We were able to fabricate yarns containing 24 single filaments at a maximum winding speed of 1800 m/min while applying a draw ratio of 2.5. The electrical conductivity of the as-spun yarns was in the 10 mS/m range, which is suitable for the production of anti-static textiles. Furthermore, the degree of crystallization declined as the GnP content increased, reducing the tenacity of the yarn but improving its elastic modulus, allowing the production of composite textiles. In conclusion, we confirmed that large amounts of graphene can be incorporated into PA6 polymers by melt spinning and that the resulting composite fibers are suitable for multiple downstream applications in the textile industry. (C) 2018 The Authors. Published by Elsevier Ltd.

Sub-microfibers and nanofibers produce more breathable fabrics than coarse fibers and are therefore widely used in the textiles industry. They are prepared by electrospinning using a polymer solution or melt. Solution electrospinning produces finer fibers but requires toxic solvents. Melt electrospinning is more environmentally friendly, but is also technically challenging due to the low electrical conductivity and high viscosity of the polymer melt. Here we describe the use of colorants as additives to improve the electrical conductivity of polylactic acid (PLA). The addition of colorants increased the viscosity of the melt by &gt, 100%, but reduced the electrical resistance by &gt, 80% compared to pure PLA (5 G&Omega, ). The lowest electrical resistance of 50 M&Omega, was achieved using a composite containing 3% (w/w) indigo. However, the thinnest fibers (52.5 &micro, m, 53% thinner than pure PLA fibers) were obtained by adding 1% (w/w) alizarin. Scanning electron microscopy revealed that fibers containing indigo featured polymer aggregates that inhibited electrical conductivity, and thus increased the fiber diameter. With further improvements to avoid aggregation, the proposed melt electrospinning process could complement or even replace industrial solution electrospinning and dyeing.

Polymer-derived ceramics (PDC) have recently gained increased interest in the field of bioceramics. Among PDC's, carbon-rich silicon oxycarbide ceramics (SiOC) possess good combined electrical and mechanical properties. Their durability in aggressive environments and proposed cytocompatibility makes them an attractive material for fabrication of bio-MEMS devices such as pacemaker electrodes. The aim of the present study is to demonstrate the remarkable mechanical and electrical properties, biological response of PDCs modified with titanium (Ti) and their potential for application as pacemaker electrodes. Therefore, a new type of SiOC modified with Ti fillers was synthesized via PDC route using a Pt-catalyzed hydrosilylation reaction. Preceramic green bodies were pyrolyzed at 1000 degrees C under an argon atmosphere to achieve amorphous ceramics. Electrical and mechanical characterization of SiCxO2(1-x)/TiOxCy ceramics revealed a maximum electrical conductivity of 10 S cm(-1) and a flexural strength of maximal 1 GPa, which is acceptable for pacemaker applications. Ti incorporation is found to be beneficial for enhancing the electrical conductivity of SiOC ceramics and the conductivity values were increased with Ti doping and reached a maximum for the composition with 30 wt % Ti precursor. Cytocompatibility was demonstrated for the PDC SiOC ceramics as well as SiOC ceramics modified with Ti fillers. Cytocompatibility was also demonstrated for SiTiOC20 electrodes under pacing conditions by monitoring of cells in an in vitro 3D environment. Collectively, these data demonstrate the great potential of polymer-derived SiOC ceramics to be used as pacemaker electrodes.

An approach to induce conductivity in immiscible polystyrene/polypropylene (PS/PP) blends is described using a percolated conducting polyaniline/polyamide (PANI/PA) filler combined with a polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene‐graft‐maleic anhydride compatibilizer. The approach is based on the ability of the compatibilizer to concomitantly stabilize the cocontinuous morphology and to improve the state of dispersion of the PANI/PA filler. Selective localization of PANI/PA in the PS phase with improved filler dispersion is achieved with the optimal master batch (MB) preparation technique followed by its optimized sequence addition to the blend components. This results in an increase in the dc conductivity by six decades as compared with that of the neat compatibilized blend at an effective 4.8‐wt % PANI concentration. An investigation of the effect of functionality and concentration of the filler and the compatibilizer on the filler connectivity in the blend is performed. The prevailing specific interactions are analyzed by Fourier transform infrared spectroscopy and thermogravimetric analysis of the MBs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48433.

Polymer derived SiOC and SiCN ceramics (PDCs) are interesting candidates for additive manufacturing techniques to develop micro sized ceramics with the highest precision. PDCs are obtained by the pyrolysis of crosslinked polymer precursors at elevated temperatures. Within this work, we are investigating PDC SiOC ceramic monoliths synthesized from liquid polysiloxane precursor crosslinked with divinylbenzene for fabrication of conductive electromechanical devices. Microstructure of the final ceramics was found to be greatly influenced by the pyrolysis temperature. Crystallization in SiOC ceramics starts above 1200 degrees C due to the onset of carbothermal reduction leading to the formation of SiC and SiO2 rich phases. Microstructural characterisation using ex-situ X-ray diffraction, FTIR, Raman spectra and microscopy imaging confirms the formation of nano crystalline SiC ceramics at 1400 degrees C. The electrical and mechanical properties of the ceramics are found to be significantly influenced by the phase separation with samples becoming more electrically conducting but with reduced strength at 1400 degrees C. A maximum electrical conductivity of 10(1) S cm(-1) is observed for the 1400 degrees C samples due to enhancement in the ordering of the free carbon network. Mechanical testing using the ball on 3 balls (B3B) method revealed a characteristic flexural strength of 922 MPa for 1000 degrees C amorphous samples and at a higher pyrolysis temperature, materials become weaker with reduced strength.

Conductive metal-organic frameworks are opening new perspectives for the use of these porous materials for applications traditionally limited to more classical inorganic materials, such as their integration into electronic devices. This has enabled the development of chemiresistive sensors capable of transducing the presence of specific guests into an electrical response with good selectivity and sensitivity. By combining experimental data with computational modelling, a possible origin for the underlying mechanism of this phenomenon in ultrathin films (ca. 30 nm) of Cu-CAT-1 is described. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:57 issue:46 pages:15086-15090 ispartof: location:Germany status: published

The mechanical properties of traditional dispersion-strengthened composites are greatly limited because of the weak interfacial bonding between the metal matrix and ex situ reinforcement. Here we report a copper matrix composite with high hardness strengthened by high-density dispersed nanoscale in situ boron, having great potential in structural and functional materials, such as wear-resistant bearings. The hardness of the composite can reach 3.04 GPa by a nanoindentation test. The composite was fabricated by a powder metallurgical process, in which the boron was produced in a copper melt directly. Nanotwins and lattice distortion zones observed in the phase boundaries may contribute to the ultrahigh hardness.

Thermotropic liquid crystalline polymer (LCP) was melt-mixed with multi-walled carbon nanotubes (MWCNTs) in a conical micro-compounder. The state of dispersion of MWCNTs in the LCP matrix was characterized using transmission electron microscopy. FIR spectroscopic analysis revealed the nature of interaction between the LCP phase and the MWCNTs. The rheological properties of the nanocomposites showed a significant dependence on the MWCNTs content. The 'network-like' structures could be assigned to 'nanotube-nanotube' and 'polymer-nanotube' interactions. Nanoindentation studies indicated an increase in Young's modulus and hardness of LCP/MWCNTs composites. DMTA studies showed an increase in the storage modulus in the composites as a function of nanotube content. (C) 2017 Elsevier Ltd. All rights reserved.

Herein, we describe a phytosynthetic, additive-free, economically viable, environmentally sustainable and rapid methodology for the formation of sphere-shaped Ag-SnO2 nanocomposites of 9 nm average particle size employing the stem extracts of Saccharum officinarum. Employing various spectroscopic techniques, the morphology, size, crystallinity, elemental conformation, and functional groups liable for surface stabilization as well as capping were depicted. Considerably, the Ag-SnO2 nanocomposite in aqueous phase revealed excellent removal efficiency for the abatement of four industrially emerging pollutants (Methylene Blue, Rose Bengal, Methyl Violet 6B, and 4-nitrophenol) and probable mechanisms were also suggested. Nearly, 99.1, 99.6, 99.5, and 98.4% of Methylene Blue, Rose Bengal, Methyl Violet 6B, and 4-nitrophenol were eradicated respectively, within 60, 75, 75, and 58.3 min using the synthesized nanocomposite. Moreover, the spent nanocomposites were renewed and their photocatalytic proficiencies were assessed for three consecutive cycles. The spent nanocomposite and the degraded products were respectively analyzed using X-ray diffraction and liquid chromatography-mass spectrometry spectroscopic methods. Additionally, the nanocomposite displayed comparative antimicrobial action against Pseudomonas aeruginosa, Escherichia coli, and Bacillus subtilis and indicated fair activity on 2,2-diphenyl-1-picrylhydrazyl scavenging with IC50 values 0.73 mM depicting its efficient antimicrobial and antioxidant activity. Thus, the present article has disclosed a revolutionary way for fabricating Ag-SnO2 nanocomposites and depicted their multifunctional efficacy as photocatalysts and reducing and prospective antibacterial and antioxidant agents.

Metal-Organic Frameworks (MOFs) have gained much interest due to their intrinsic tunable nature. In this work, we study how linker functionalization modifies the electronic structure of the host MOF, more specifically the MIL-47(V)-R (R=-F, -Cl, -Br, -OH, -CH$_3$, -CF$_3$, and -OCH$_3$). It is shown that the presence of a functional group leads to a splitting of the $\pi$-orbital on the linker. Moreover, the upward shift of the split-off $\pi$-band correlates well with the electron withdrawing/donating nature of the functional groups. For halide functional groups the presence of lone-pair back donation is corroborated by calculated Hirshfeld-I charges. In case of the ferromagnetic configuration of the host MIL-47(V$^{\mathrm{+IV}}$) material a half-metal to insulator transition is noted for the -Br, -OCH$_3$, and -OH functional groups, while for the anti-ferromagnetic configuration only the hydroxy-group results in an effective reduction of the band gap., Comment: 11 pages, 4 figures, 3 Tables

The archetypal silica- and aluminosilicate-based zeolite-type materials are renowned for wide-ranging applications in heterogeneous catalysis, gas-separation and ion-exchange. Their compositional space can be expanded to include nanoporous metal chalcogenides, exemplified by germanium and tin sulfides and selenides. By comparison with the properties of bulk metal dichalcogenides and their 2D derivatives, these open-framework analogues may be viewed as three-dimensional semiconductors filled with nanometer voids. Applications exist in a range of molecule size and shape discriminating devices. However, what is the electronic structure of nanoporous metal chalcogenides? Herein, materials modeling is used to describe the properties of a homologous series of nanoporous metal chalcogenides denoted np-MX2, where M = Si, Ge, Sn, Pb, and X = O, S, Se, Te, with Sodalite, LTA and aluminum chromium phosphate-1 structure types. Depending on the choice of metal and anion their properties can be tuned from insulators to semiconductors to metals with additional modification achieved through doping, solid solutions, and inclusion (with fullerene, quantum dots, and hole transport materials). These systems form the basis of a new branch of semiconductor nanochemistry in three dimensions.

The impact of the inner structure and thermal history of planets on their observable features, such as luminosity or magnetic field, crucially depends on the poorly known heat and charge transport properties of their internal layers. The thermal and electric conductivities of different phases of water (liquid, solid, and super-ionic) occurring in the interior of ice giant planets, such as Uranus or Neptune, are evaluated from equilibrium ab initio molecular dynamics, leveraging recent progresses in the theory and data analysis of transport in extended systems. The implications of our findings on the evolution models of the ice giants are briefly discussed., The authors here perform ab initio calculations to investigate in the heat transport properties of water at extreme pressure and temperature conditions, typically found in the interior of ice giants such as Uranus and Neptune.

The conductive polymer complex poly (3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) is the most explored conductive polymer for conductive textiles applications. Since PEDOT:PSS is readily available in water dispersion form, it is convenient for roll-to-roll processing which is compatible with the current textile processing applications. In this work, we have made a comprehensive review on the PEDOT:PSS-based conductive textiles, methods of application onto textiles and their applications. The conductivity of PEDOT:PSS can be enhanced by several orders of magnitude using processing agents. However, neat PEDOT:PSS lacks flexibility and strechability for wearable electronics applications. One way to improve the mechanical flexibility of conductive polymers is making a composite with commodity polymers such as polyurethane which have high flexibility and stretchability. The conductive polymer composites also increase attachment of the conductive polymer to the textile, thereby increasing durability to washing and mechanical actions. Pure PEDOT:PSS conductive fibers have been produced by solution spinning or electrospinning methods. Application of PEDOT:PSS can be carried out by polymerization of the monomer on the fabric, coating/dyeing and printing methods. PEDOT:PSS-based conductive textiles have been used for the development of sensors, actuators, antenna, interconnections, energy harvesting, and storage devices. In this review, the application methods of PEDOT:SS-based conductive polymers in/on to a textile substrate structure and their application thereof are discussed.

Li-ion conductivity increases with introduction of an interfacial ice layer in nano-SCE., The transition to solid-state Li-ion batteries will enable progress toward energy densities of 1000 W·hour/liter and beyond. Composites of a mesoporous oxide matrix filled with nonvolatile ionic liquid electrolyte fillers have been explored as a solid electrolyte option. However, the simple confinement of electrolyte solutions inside nanometer-sized pores leads to lower ion conductivity as viscosity increases. Here, we demonstrate that the Li-ion conductivity of nanocomposites consisting of a mesoporous silica monolith with an ionic liquid electrolyte filler can be several times higher than that of the pure ionic liquid electrolyte through the introduction of an interfacial ice layer. Strong adsorption and ordering of the ionic liquid molecules render them immobile and solid-like as for the interfacial ice layer itself. The dipole over the adsorbate mesophase layer results in solvation of the Li+ ions for enhanced conduction. The demonstrated principle of ion conduction enhancement can be applied to different ion systems.

Conductive inks consisting of graphene and carbon black conductive fillers into a polydimethylsiloxane (PDMS) matrix, which can be processed into thin films by screen printing are developed. The influence of filler composition and content on mechanical and electrical properties of the conductive composites is investigated. The best composites were evaluated as electrode material for dielectric elastomer actuators and for piezoelectric sensors. With increasing filler content, the electrical properties of the resulting composites of graphite nanoplates (GNPs) or a binary mixture of GNPs and carbon black (CB) with PDMS (Mw = 139 kg/mol) are enhanced. Hence, PDMS composites filled with GNPs (42 wt.%) or a binary mixture of GNPs/CB (300/150 ratio, 30 wt.% of total filler loading) exhibited constant contact resistance values of 0.5 and 5 Ω determined in life-cycle test, respectively, thus rendering them suitable as electrode materials for piezosensors. On the other hand, dielectric elastomer actuators require more flexible electrode materials, which could be tuned by varying the polymer molecular weight and by reducing the filler content. Therefore, a composite consisting of PDMS (Mw = 692 kg/mol) and a binary filler mixture of GNPs/CB (150/75 ratio, 18 wt.% of total filler loading) was used for producing the electrodes of dielectric elastomer transducers (DETs). The produced DETs with different electrode thicknesses were characterized in terms of their performance. The negligible hysteresis of the electrode materials is favorable for sensor and actuator applications.

Increasing numbers of electrically active porous framework materials are being reported, with conductivities that make them attractive for technological applications. As design strategies for efficient carrier transport emerge, the next challenge is to incorporate the materials into a functioning device. In thin-film devices interface effects are of critical importance to overall function. In this article we present a method to identify compatible materials combinations to achieve mechanically robust, electronically optimal pairings. The computational screening is based on a two-step procedure: (i) matching of lattice constants to ensure interfaces with minimal epitaxial strain and therefore maximal mechanical and chemical stability; (ii) matching of absolute electron energies to construct energy-band-alignment diagrams, which can be used to screen for particular electronic applications. We apply the methodology to search for zeolitic imidazolate framework (ZIF) type materials that are compatible with native metal electrodes. The procedure allows us to predict simple routes for electrochemical deposition of ZIFs for application as conductive porous electrodes.

Epoxy Gel Casting (EGC) was recently coined to designate a setting mechanism based on the in situ polymerization of epoxy resins dissolved in the aqueous dispersion media of ceramic powder suspensions upon adding suitable amine-based crosslinking agents. The specific interactions between the surface of the powder particles and the processing additives are likely to determine different partitions of the crosslinking species, dissolved in the bulk solution, or adsorbed at the surface of the particles, and affect the EGC process. The present work aims at evaluating the influence of surface chemistry on the extent of the specific interactions at the solid/liquid interface and how it affects the polymerization kinetics and the properties of ceramic green bodies consolidated by EGC. Three different ceramic oxides (alumina, zirconia and fused silica) having similar particle size distributions were used. Stable colloidal suspensions with 45 vol.% solids were prepared by dispersing the powders in aqueous solutions containing a fixed amount of a common dispersant and various dissolved amounts of an epoxy resin. Zeta potential, theological measurements and calorimetry were used to assess the specific interactions and their effects on the consolidation kinetics upon adding a polyamine hardener, and on the final properties of consolidated parts. With the isoelectric point of the naked particle surface decreasing, there were noticeable decreases in gelation time, shrinkage, green density, and flexural strength of the green ceramic body's properties. An interaction model is proposed to explain the observed differences. The potential of EGC to consolidate ceramic microneedles cast in soft rubber moulds was demonstrated. (C) 2016 Elsevier Ltd. All rights reserved.

Composites of polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs) were prepared via melt-mixing utilizing Li-salt of 6-amino heaxanoic acid (Li-AHA) modified MWCNTs in the presence of a compatibilizer (polypropylene-g-maleic anhydride; PP-g-MA). Improved interaction between the anhydride group of PP-g-MA and the amine functionality of Li-AHA was confirmed via FTIR and Raman spectroscopic analysis. A higher glass transition temperature (Tg) of the PP phase has been observed in these composites as compared to pristine MWCNTs based composites. The crystallization temperature (Tc) of the PP phase was increased as a function of pristine MWCNTs concentration in PP/MWCNTs composites indicating hetero-nucleating action of MWCNTs. However, Tc value was decreased in the presence of Li-AHA modified MWCNTs indicating the adsorbed Li-AHA on the MWCNTs surface. Moreover, Tc value was higher in the presence of Li-AHA modified MWCNTs with PP-g-MA as compared to that of without PP-g-MA, suggesting the desorbed Li-AHA from the MWCNTs surface due to melt-interfacial reaction. Further, MWCNTs were extracted by hot vacuum filtration technique from PP/MWCNTs composites containing Li-AHA and PP-g-MA. The isothermal crystallization kinetics showed a variation in crystallization behavior of the PP phase in the corresponding composites as compared to the “extracted MWCNTs.” POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

The different oxidation states of chromium allow its bulk oxide form to be reducible, facilitating the oxygen vacancy formation process, which is a key property in applications such as catalysis. Similar to other useful oxides such as TiO2, and CeO2, the effect of substitutional metal dopants in bulk Cr2O3 and its effect on the electronic structure and oxygen vacancy formation are of interest, particularly in enhancing the latter. In this paper, density functional theory (DFT) calculations with a Hubbard + U correction (DFT+U) applied to the Cr 3d and O 2p states, are carried out on pure and metal-doped bulk Cr2O3 to examine the effect of doping on the electronic and geometric structure. The role of dopants in enhancing the reducibility of Cr2O3 is examined to promote oxygen vacancy formation. The dopants are Mg, Cu, Ni, and Zn, which have a formal +2 oxidation state in their bulk oxides. Given this difference in host and, dopant oxidation states, we show that to predict the correct ground state two metal dopants charge compensated with an oxygen vacancy are required. The second oxygen atom removed is termed "the active" oxygen vacancy and it is the energy required to remove this atom that is related to the reduction process. In all cases, we find that substitutional doping improves the oxygen vacancy formation of bulk Cr2O3 by lowering the energy cost.

We present a new route of tethering graphene nanoplatelets (GNPs) with Fe3O4 nanoparticles to enable their alignment in an epoxy using a weak magnetic field. The GNPs are first stabilized in water using polyvinylpyrrolidone (PVP) and Fe3O4 nanoparticles are then attached via co-precipitation. The resultant Fe3O4/PVP-GNPs nanohybrids are superparamagnetic and can be aligned in an epoxy resin, before gelation, by applying a weak magnetic field as low as 0.009 T. A theoretical model describing the alignment process is presented and used to quantify the effects of key parameters on the time needed for the alignment process. Compared to the unmodified epoxy, the resulting epoxy polymer nanocomposites containing randomly-oriented Fe3O4/PVP-GNPs nanohybrids exhibit significantly improved electrical conductivities by up to three orders of magnitude and fracture energies by up to 300%. The alignment of the Fe3O4/PVP-GNPs nanohybrids in the epoxy polymer nanocomposites transverse to the direction of crack propagation further increased the fracture energy by 50%, and the electrical conductivity by seven fold in the alignment direction, compared to the nanocomposites containing randomly-oriented nanohybrids.

A simple model on the performance of composite CO2 separation membranes (ceramic oxide-ion conductor and molten alkaline carbonates) is derived from an equivalent circuit comprising two interlinked cells, using the main electrical circuit component analogs of the electrochemical characteristics of each composite phase (thermodynamic voltages and ionic resistances) and surrounding gas phase activities of species involved in the surface reactions. A newly introduced graphical solution inspired in conventional corrosion diagrams is used to benchmark, map and discuss membrane performance, including the roles of cell inner ionic transport and surface/interface reaction processes. The impact of oxide phase composition (ZrO2, CeO2 and Bi2O3- based oxides), content (4090 vol%) and working temperature (873-973K) on membrane performance are assessed in detail, highlighting the limits of materials currently available. Selected examples of published data on membrane performance are used to demonstrate the efficacy of the suggested diagram and to comment on permeation kinetic constraints, namely phase tortuosity. (C) 2016 Elsevier Ltd. All rights reserved.

Biobased polyamide 410 (PA410)/multiwall carbon nanotube (CNT) nanocomposites (NCs) were obtained by melt-mixing in a twin screw extruder a Polyamide 6 (PA6)-based masterbatch (with 15 wt % CNT content) with neat PA410. Directly mixed PA410/CNT NCs were also obtained for comparison purposes. Transmision Electronic Microscopy (TEM) observation and conductivity measurements demonstrated that a good dispersion of CNTs was obtained, which was probably induced by the full miscibility between PA410 and PA6 (in the concentration range employed here), as ascertained by Differential Scanning Calorimetry (DSC) tests. As a result, the PA410/PA6/CNT NCs showed superior mechanical behaviour (&asymp, 10% Young&rsquo, s modulus increase with a 4 wt % CNT content) than the binary PA410/CNT NCs (&asymp, 5% Young&rsquo, s modulus increase with a 6 wt % CNT content), as well as superior electrical behaviour, with maximum conductivity values of approximately three orders of magnitude higher than in the binary PA410/CNT system, and lower percolation threshold values (0.65 wt % CNT content vs. 3.98 wt % CNT). The good dispersion and enhanced mechanical and electrical properties of these novel biobased nanocomposites, broadens their potential applications, such as electrical and electronics (E&amp, E) or automotive industries.

Carbon nanotube grafted carbon fibers (CNT-g-CFs) were prepared continuously, spool to spool, via thermal CVD. The application of an in-situ potential difference (300 V), between the fibers and a cylindrical graphite foil counter electrode, enhanced the growth, producing a uniform coverage of carbon nanotubes with diameter ca. 10 nm and length ca. 125 nm. Single fiber tensile tests show that this approach avoids the significant reduction of the underlying carbon fiber strengths, which is usually associated with CVD grafting processes. Single fiber fragmentation tests in epoxy, with in-situ video fragment detection, demonstrated that the CNT-g-CFs have the highest interfacial shear strength reported for such systems (101 ± 5 MPa), comparable to state-of-the-art sizing controls (103 ± 8 MPa). Single fiber pull-out data show similar trends. The short length of the grafted CNTs is particularly attractive for retaining the volume fraction of the primary fibers in composite applications. The results are compared with a short review of the interfacial data available for related systems.

The present paper describes improvements in the fracture resistance of epoxy polymers due to the addition of either (a) one-dimensional (1-D) carbon nanofibres (CNFs), or (b) two-dimensional (2-D) graphene nanoplatelets (GNPs), or (c) hybrid combinations of these carbon nanofillers (i.e. using both CNFs and GNPs). The effects of the dimensional shape and concentration (i.e. 0.0, 0.5, 1.0, 1.5 and 2.0 wt%) of the nanoscale carbon fillers are considered. The addition of CNFs, GNPs or hybrid combinations of CNFs and GNPs increases greatly the quasi-static fracture energy, GIc, of the epoxy due to these nanofillers inducing multiple intrinsic (e.g. interfacial debonding and void growth) and extrinsic (e.g. pull-out and bridging) toughening mechanisms. A mechanistic model is presented to quantify the contributions from the different toughening mechanisms induced by the CNF and the GNP fillers which result in the improvements observed in the fracture energy. The resistance of the epoxy, modified with either the GNPs or the CNFs, to cyclic-fatigue loading is also increased by the presence of the carbon nanofillers.

Exceptional properties such as dielectric, ferroelectric, piezoelectric, magnetic, catalytic, and photovoltaic of perovskite materials open new doors to many groundbreaking discoveries for unique device ideas. These materials properties are inherited from their crystal structures; therefore, the features can be tuned via varying details of the crystal structures. In the literature, LaCrO3 (LCO) is one those mostly examined perovskites for various purposes such as solid oxide fuel cells, catalytic converters, and sensors. In the present study, the band gap tuning of LCO was investigated via doping a transition element such as cobalt (Co), palladium (Pd), and iridium (Ir) into Cr atom. The synthesized doped and un-doped LCO powders were characterized by infrared spectra (IR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) was employed to study the surface topography of LCO and doped LCO thin films on silicon substrates. The band gaps of the LCO and doped LCO films were scrutinized using a UV-Vis spectrometer. Our study has shown that the band gap of LCO was successfully lowered from 3.4 eV to 2.66 eV and can be engineered via substitution at various mol% of transition elements (Co, Pd, Ir) onto B-site Cr atom in the LCO perovskite structure. Türkiye Bilimsel Ve Teknolojik Araştırma Kurumu ( Tübitak )

The topochemical conversion of a dense, insulating metal–organic framework (MOF) into a semiconducting amorphous MOF is described. Treatment of single crystals of copper(I) chloride trithiocyanurate, CuICl(ttcH3) (ttcH3 = trithiocyanuric acid), 1, in aqueous ammonia solution yields monoliths of amorphous CuI1.8(ttc)0.6(ttcH3)0.4, 3. The treatment changes the transparent orange crystals of 1 into shiny black monoliths of 3 with retention of morphology, and moreover increases the electrical conductivity from insulating to semiconducting (conductivity of 3 ranges from 4.2 × 10−11 S cm−1 at 20 °C to 7.6 × 10−9 S cm−1 at 140 °C; activation energy = 0.59 eV; optical band gap = 0.6 eV). The structure and properties of the amorphous conductor are fully characterized by AC impedance spectroscopy, X-ray photoelectron spectroscopy, X-ray pair distribution function analysis, infrared spectroscopy, diffuse reflectance spectroscopy, electron spin resonance spectroscopy, elemental analysis, thermogravimetric analysis, and theoretical calculations.

Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (conductivity, stability, transparency and biocompatibility). The gold standard material is the commercially available poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect the two fields of biology and electronics, PEDOT: PSS presents some limitations associated with its low (bio) functionality. In this review, we provide an insight into the synthesis and applications of innovative poly(ethylenedioxythiophene)-type materials for bioelectronics. First, we present a detailed analysis of the different synthetic routes to (bio) functional dioxythiophene monomer/polymer derivatives. Second, we focus on the preparation of PEDOT dispersions using different biopolymers and biomolecules as dopants and stabilizers. To finish, we review the applications of innovative PEDOT-type materials such as biocompatible conducting polymer layers, conducting hydrogels, biosensors, selective detachment of cells, scaffolds for tissue engineering, electrodes for electrophysiology, implantable electrodes, stimulation of neuronal cells or pan-bio electronics. The work was supported by EU through the projects FP7-PEOPLE-2012-ITN 316832-OLIMPIA and FP7-PEOPLE-2013-ITN 607896-OrgBio. Ana Sanchez-Sanchez is thankful for the Postdoctoral Funding for Doctoral Research Staff Improvement Grant from the Basque Government. David Mecerreyes thanks Becas de Practicas en el Extranjero "Global Training".

The use of graphene materials as conductive inks for flexible and transparent electronics is promising, but challenged by the need for stabilizers, specialized organic solvents, and/or high temperature annealing, severely limiting performance or compatibility with substrates and printing techniques. Here, the development of a scalable water-based graphene oxide ink is reported that can be screen-printed on flexible plastic substrates and subsequently reduced using a 1: 1 mixture of trifluoroacetic acid and hydroiodic acid, thereby creating an electric circuit. The reduced prints exhibit low sheet resistance of 327 Omega sq(-1) for thin semitransparent layers with 37% transmittance. This methodology with postprinting chemical reduction outperforms high temperature annealing, thereby eliminating the need for such a step, which is incompatible with flexible plastic substrates. The strategy relies on low cost, industrially compatible chemicals and can be scaled up for low cost manufacture of roll-to-roll printed electronics.

Scandia-stabilized-zirconia is a potential zirconia-based electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, the properties of zirconia co-doped with 10 mol% Sc and 1 mol% Ce (scandia-ceria-stabilized-zirconia, 10Sc1CeSZ) electrolyte synthesized by the microwave-assisted glycine nitrate process (MW-GNP) were determined. The effects of microwave heating on the sintering temperature, microstructure, densification and ionic conductivity of the 10Sc1CeSZ electrolyte were evaluated. The phase identification, microstructure and specific surface area of the prepared powder were investigated using X-ray diffraction, transmission electron microscopy and the Brunauer-Emmett-Teller technique, respectively. Using microwave heating, a single cubic-phase powder was produced with nanosized crystallites (19.2 nm) and a high specific surface area (16 m2/g). It was found that the relative density, porosity and total ionic conductivity of the 10Sc1CeSZ electrolyte are remarkably influenced by the powder processing method and the sintering temperature. The pellet sintered at 1400 °C exhibited a maximum ionic conductivity of 0.184 S/cm at 800 °C. This is the highest conductivity value of a scandia-stabilized-zirconia based electrolyte reported in the literature for this electrolyte type. The corresponding value of the activation energy of electrical conductivity was found to be 0.94 eV in the temperature range of 500–800 °C. Overall, the use of microwave heating has successfully improved the properties of the 10Sc1CeSZ electrolyte for application in an IT-SOFC.

Transformer oil-based nanofluids are known to have higher thermal conductivity and heat transfer performance compared to conventional transformer oils. In this study, four different types of transformer oil-based nanofluids are synthesized using the well-known two-step method. The first nanofluid contains pure multi-walled carbon nanotubes (MWCNTs), while other samples consist of 20 Vol% of MWCNTs and 80 Vol% of different oxide nanoparticles (i.e., Al2O3, TiO2, and SiO2). The dynamic viscosity and thermal conductivity of prepared samples are investigated in seven different volume fractions of 0.001, 0.0025, 0.005, 0.01, 0.025, 0.05, and 0.1%. Besides, the breakdown voltage of the pure transformer oil and nanofluids containing 0.05 and 0.1 Vol% of nanoparticles is investigated. The outcomes show that dielectric properties of hybrid carbon-based nanofluids are far better compared to those properties of the pure MWCNTs nanofluids. Finally, eight different soft computing approaches, including group method of data handling (GMDH), support vector machine (SVM), radial basis function (RBF) neural network, multilayer perceptron (MLP), and MLP and RBF models optimized with bat and grasshopper optimization algorithm (GOA), are used to model the viscosity and thermal conductivity of synthesized nanofluids. The outcomes show that the GMDH approach significantly outperforms all other models in terms of predicting the thermal conductivity and dynamic viscosity of transformer oil-based nanofluids. (C) 2019 Elsevier B.V. All rights reserved.

Molecular dynamics were used to simulate the dispersion of graphene in aqueous medium in the presence of a novel organic modifier, sodium salt of 6-amino hexanoic acid (Na-AHA), which non-covalently modifies the graphene surfaces. The modifier molecule contains an ionizable carboxylate head group and an aliphatic tail. The extent of dispersion was estimated by calculating the potential of mean force (PMF) as a function of increasing concentration of the modifier using the thermodynamic perturbation method in conjunction with molecular dynamics simulations. With increasing concentration of the modifier, the PMF changed from a short-range strong attraction to a long-range repulsion at higher modifier concentrations. The simulation results clearly show the adsorption of modifier molecules at the graphene–water interface, which in turn causes the graphene surfaces to acquire a negative charge. Further, the development of a negative electric potential at the graphene surfaces induces a long-range electrostatic repulsion between the graphene sheets, clearly pointing to an electrostatic stabilization of Na-AHA modified-graphene in aqueous medium.

Short-circuit prevention and repair strategies are essential to allow for upscaled production of organic electronic devices based on thin-film production technology. Occurrence of short circuits is a consequence of manufacturing imperfections and particle contamination. After giving a concise review of short-circuit prevention methods for organic thin-film devices in the open literature of the past decade, this overview article summarizes our recent work on short-circuit prevention in organic light-emitting diodes and organic solar cells by chemical oxidation methods. Our main strategy is based on self-aligned disruption of the conductivity of exposed areas of the typically applied hole transport material poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) by aqueous sodium hypochlorite, prior to cathode deposition. The ten orders of magnitude decrease in local conductivity obtained proves sufficient to let deliberately flawed devices operate at pristine performance levels. We next show that in the case of organic solar cells based on a lithium fluoride/aluminium cathode the shunting junctions can be made sufficiently resistive to allow for near unflawed operation, without applying wet treatment.

The CNTs aggregation in a low-viscosity PDMS matrix was studied from simultaneous time-resolved measurements of electrical conductivity and dynamic shear modulus. The concentration of nanotubes (phi = 0.2%) was chosen in order to be in the semidilute regime of the suspensions. After a nonlinear compressive deformation, it was shown that the kinetics of CNTs aggregation develops rapidly by increasing the deformation. However, above a critical deformation (gamma, = 60% corresponding to a critical Peelet number Pc-c approximate to 1 x 10), the equilibrium value of the storage modulus and electrical conductivity decreases with increasing the deformation. It was then concluded that low shear deformations induced an aggregation mechanism, but these aggregates broke down at high shear, forming small aggregates with less entanglements. Furthermore, this phenomenon of CNTs cluster aggregation was also highlighted by optical microscopy as the clustering mechanism of the CNTs was clearly observable after few hours.

For materials based on ferrites and manganites with DD degrees(2+) and D'D degrees(2+) cations substituted into D sublattice, the functional properties are studied and the prospects as electrode materials for solid-oxide fuel cells are assessed. The electronic conductivity of materials based on La(0.5)A(0.5)Mn(0.5)Ti(0.5)O(3-delta) is shown to decrease with the increase in the ionic radius of alkali-earth substituent; however, for La0.5D'D degrees 0.5Mn0.5Ti0.5O3-delta and La0.5D'D degrees 0.5Fe0.5Ti0.5O3-delta, the appearance of n-conduction is observed during reduction, which may provide adequate conductivity under anodic conditions. Under the conditions of fuel cell operation, the thermal expansion coefficients of these materials are (13.0-13.5) x 10(-6) K-1. The thermal and chemical expansion increases with the increase in the radius of alkali-earth cation; the latter value does not exceed 0.2%, which is acceptable for preparation of electronic layers. The transition of oxygen through membranes based on materials studied is determined to the large extent by the kinetics of surface exchange which depends on the rate of delivery of oxygen vacancies to the surface. Doping of ferrites with chromium or titanium decreases the electronic and ionic conductivity; however, the presence of substituents in D' sublattice makes it possible to stabilize the perovskite phase in a wide range of NEuro(D-2), decrease the thermal and chemical expansion, and prevent to the large extent the ordering of oxygen vacancies, which allows one to consider these materials as the candidates for electrodes in symmetrical solid-oxide fuel cells.

International audience; Poly(3,4-ethylenedioxythiophene) (PEDOT) is certainly the most known and most used conductive polymer because it is commercially available and shows great potential for organic electronic, photovoltaic, and thermoelectric applications. Studies dedicated to PEDOT films have led to high conductivity enhancements. However, an exhaustive understanding of the mechanisms governing such enhancement is still lacking, hindered by the semicrystalline nature of the material itself. In this article, we report the development of highly conductive PEDOT films by controlling the crystallization of the PEDOT chains and by a subsequent dopant engineering approach using iron(III) trifluoromethanesulfonate as oxidant, N-methyl pyrrolidone as polymerization rate controller and sulfuric as dopant. XRD, HRTEM, Synchrotron GIWAXS analyses and conductivity measurements down to 3 K allowed us to unravel the organization, doping, and transport mechanism of these highly conductive PEDOT materials. N-methyl pyrrolidone promotes bigger crystallites and structure enhancement during polymerization, whereas sulfuric acid treatment allows the replacement of triflate anions by hydrogenosulfate and increases the charge carrier concentration. We finally propose a charge transport model that fully corroborates our experimental observations. These polymers exhibit conductivities up to 5400 S cm(-1) and thus show great promise for room temperature thermoelectric applications or ITO alternative for transparent electrodes.

Several composite materials were produced using ceria nanoparticles (1 mu m). The oxides were combined with a mixture of Na2CO3 and Li2CO3 (eutectic composition), and fired at temperatures in the 600-700 degrees C range (vacuum assisted in a few cases). The composites were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy, in air, in the 300-600 degrees C range. Irrespective of composition or grain size all samples exhibited the same type of conductivity dependence on temperature, with a steep change close to the carbonates eutectic temperature. At T > 500 degrees C all materials have identical conductivity, indicating that molten carbonates dominate the electrical performance. However, at low temperature (300-450 degrees C) significant differences can be noticed in all composites, with the best performance observed for ceria based composites with larger grain size (close to 135 nm). Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

This work explores the possibilities to design magnetite-based spinels through multiple simultaneous co-substitutions with transition metal cations, with emphasis on redox behavior and electronic transport. For the first time this approach was assessed for high-temperature applications, which is of particular interest for the development of consumable anodes for pyroelectrolysis, an alternative carbon-lean steelmaking process. A Taguchi plan was used to assess the impact of the concentration of substituting chromium, titanium, manganese and nickel cations on the lattice parameter and electrical conductivity of the multicomponent ferrospinels. The results revealed a comparable decrease in the electrical conductivity, provided by Cr3+, Mn3+/2+ and Ni2+ cations. The impact of Ti4+ was found to be less negative, contributed by the formation of Fe2+ cations and increased hopping probability. The strongest structural impacts, exerted by manganese cations, are likely to affect the mobility of polarons, as revealed by the analysis of the correlation factors for combined effects. Ferrospinels, containing various transition metal cations, are more susceptible to oxidation and phase decomposition, which often result in a sudden conductivity drop and significant dimensional changes in the ceramics. The observed trends for redox behavior suggest that the potential applications of multicomponent ferrospinels in oxidizing conditions are limited to 1000-1400 K due to insufficient stability, while higher temperature applications, requiring significant electronic conductivity, are rather suitable.

Strontium vanadate-based perovskites are considered as promising anode materials for hydrocarbon-fueled solid oxide fuel cells due to high electronic conductivity, sulfur tolerance and resistance to coking, but possess a narrow phase stability domain precluding their use in practice. This study aimed at expanding the perovskite phase stability domain by donor-type substitutions focusing on Sr(0.8)Ln(0.2)V(1-y)Nb(y)O(3-delta) (Ln = La or Y, y = 0-0.10) solid solutions. The upper-p(O-2) stability boundary at 900 degrees C was found to shift from similar to 10(-15) atm for the parent strontium vanadate to similar to 6 x 10(-13) atm for Sr0.8Y0.2VO3-delta, whereas oxidative decomposition of Sr0.8La0.2VO3-delta occurs in the p(O-2) range between 10(-10) and 10(-5) atm. Co-substitution by niobium in the vanadium sublattice has rather minor (Y-containing series) or even negative (La-containing series) effects on the perovskite phase stability boundary, but results in a slower kinetics of oxidative decomposition in an inert atmosphere. Sluggish oxidation kinetics in inert gas environments, demonstrated by electrical, thermogravimetric, dilatometric and structural studies, results in a nearly reversible behavior of Sr(0.8)Ln(0.2)V(1-y)Nb(y)O(3-delta) after exposure to inert atmosphere, thus enabling the fabrication of solid-electrolyte cells with SrVO3-delta-based anodes under these conditions. Donor-type substitution is demonstrated also to decrease the electronic conductivity, which still remains sufficiently high for electrode application (>100 S cm(-1) at temperatures

Structural and defect chemistry guidelines were used for Nb-substituted SrVO3-delta materials, designed to meet SOFC anode requirements, with emphasis on redox tolerance, thermochemical compatibility with other SOFC materials, electrical conductivity and adjustable changes in oxygen stoichiometry for their prospective impact on electrocatalytic performance. SrV1-xNbxO3-delta (x = 0-0.30) ceramics were prepared by solid-state synthesis and sintered at 1773 K in a reducing atmosphere. XRD and SEM/EDS showed that under these conditions a single-phase cubic perovskite structure appears up to x approximate to 0.25. Electrical conductivity is metallic-like and nearly p(O-2)-independent. Although substitution by niobium decreases the conductivity, which still exceeds 100 S cm(-1) for x

Atmospherically stable porous frameworks and materials are interesting for heterogeneous solid-gas applications. One motivation is the direct and selective uptake of pollutant/hazardous gases, where the material produces a measurable response in the presence of the analyte. In this report, we present a combined experimental and theoretical rationalization for the piezochromic response of a robust and porous molecular crystal built from an extensively fluorinated trispyrazole. The electronic response of the material is directly determined by analyte uptake, which provokes a subtle lattice contraction and an observable bathochromic shift in the optical absorption onset. Selectivity for fluorinated absorbates is demonstrated, and toluene is also found to crystallize within the pore. Furthermore, we demonstrate the application of electronic structure calculations to predict a physicochemical response, providing the foundations for the design of electronically tunable porous solids with the chemical properties required for development of novel gas-uptake media.

The structural and low-frequency dielectric properties of Y-doped strontium titanate ceramics prepared by the conventional mixed oxide method are investigated. The lattice parameter is found to decrease linearly in the Sr1 − 1.5xYxTiO3 system, confirming the incorporation of Y onto the Sr site of perovskite lattice of strontium titanate up to the solid solubility limit below x = 0.05. The real and imaginary parts of the dielectric permittivity of Sr1 − 1.5xYxTiO3 ceramics exhibit a relaxation between 100 Hz and 1 MHz in the temperature range 10–40 K, slightly shifting to higher temperatures with increasing Y content. Such dielectric behavior, yielding real part of the dielectric permittivity up to 35 000, is attributed to the relaxation of individual dipoles formed by off-center displacement of Y3+ ions on Sr sites in a highly polarizable lattice of strontium titanate. The other dielectric relaxation observed in Sr1 − 1.5xYxTiO3 from 125 to 300 K is attributed to the oxygen vacancy related mechanisms.

International audience; This review article describes recent advances in the elaboration of graphene-based colloidal nanocomposites by the use of graphene or graphene oxide in heterophase polymerization systems. Two main routes are reviewed: latex blending and in situ polymerization. In the first strategy, a segregated network is formed by confining the graphenic fillers in the interstices between the latex particles during the drying process. The morphology of the network depends on the relative dimensions of the fillers and the latex particles and on the interfacial interactions. The various approaches used to promote latex/graphene interactions via charge attractions or pi stacking are reviewed. The second method relies on the in situ formation of polymer latexes in the presence of graphenic fillers using emulsion, miniemulsion or suspension polymerization processes in the presence or absence of a stabilizer. The use of graphene oxide as a Pickering stabilizer and the effect of the dimensional characteristics of the graphene sheets on particle morphology are also discussed. Finally, a brief discussion of the mechanical and electrical properties of graphene-latex nanocomposites with regard to the characteristics of the filler and the latex-graphene relative dimensions is given to provide insight into the main requirements of graphenic fillers with respects to various applications.

Additive manufacturing (AM), or 3D printing as it is more commonly known, is the process of creating 3D objects from digital models through the sequential deposition of material in layers. Electrochemical 3D printing is a relatively new form of AM that creates metallic structures through electrochemical reduction of metal ions from solutions onto conductive substrates. The advantage of this process is that a wide range of materials and alloys can be deposited under ambient conditions without thermal damage and more importantly at low cost, as this does not require expensive laser optics or inert gas environments. Other advantages include the fact that this process can be both additive and subtractive through reversal of potential allowing for recycling of components through electrochemical dissolution. However, one main limitation of this technology is speed. Here, a novel electrochemical 3D printer design is proposed using a meniscus confinement approach which demonstrates deposition rates three orders of magnitude higher than equivalent systems due to improved mass transport characteristics afforded through a mechanical electrolyte entrainment mechanism. Printed copper structures exhibit a polycrystalline nature, with decreasing the grain size as the potential is increased resulting in a higher Vickers hardness and electronic resistivity.

International audience; Electrical measurements of conducting and dielectric materials under high pressures (in the order of GPa) reveal important information regarding orbital overlaps, electronic states, changes in transition temperatures, and activation volumes (Delta V). In this study, we demonstrate a new method for high-pressure impedance measurements, up to 4 GPa, utilizing an indentation-induced local stress field. The current system does not require any pressure mediums or pressure calibrations. The Delta V for O2- ion conduction in 10 mol\% Y2O3-doped zirconia at 500 degrees C was estimated to be 3.0 cm(3) mol(-1). Delta V increased with increasing temperatures from 500 to 600 degrees C. The technique also allows the concurrent determination of the effective elastic modulus by fitting the experimental data obtained from the indentation load-depth profile curve with the Hertzian elastic model. The experimental values were consistent with the theoretical values. (C) 2013 Elsevier B.V. All rights reserved.

An investigation of the chemical compatibility and electrochemical performance of composite electrodes based on LaCoO3 (LC) and La0.8Sr0.2Co0.2Fe0.8O3-delta (LSCF) for ceria/carbonate composite electrolytes is presented. The tests are based on symmetric cells (electrode/electrolyte/electrode) prepared using Li2CO3 and Na2CO3 mixed with LC or LSCF as composite electrodes, and Gd-doped ceria mixed with the same carbonates as composite electrolyte. Reactivity tests performed at 550 degrees C for 5 h identified LSCF as the most stable perovskite in pure CO2, with only minor loss of Sr, while LC shows partial decomposition. The chemical stability of both materials exposed to lower CO2 activity is confirmed by X-ray diffraction. Cell assemblies tested by impedance spectroscopy in the temperature range 520-600 degrees C, in air and pure CO2, confirm the potential of these composite electrodes for intermediate temperature applications such as fuel cells and carbon dioxide permeation membranes. (C) 2014 Elsevier Ltd. All rights reserved.

International audience; We report experimental results on the propagation of ultrasonic waves (at frequencies in the range of 40 kHz) in aqueous foams. Monitoring the acoustics of the foams as they age, i.e. as the mean bubble radius increases by coarsening, we recover at short times some trends that are already known: decrease of the speed of sound and increase of attenuation. At long times, we have identified, for the first time, robust non-monotonic behaviors of the speed of sound and attenuation, associated with a critical bubble size, which decreases at increasing frequency. The experimental features appear to be surprisingly reminiscent of the Minnaert resonance known for a single isolated bubble in a fluid. Transposing the Minnaert theoretical framework to the limit of a dense packing of bubbles gives some qualitative agreement with the data, but still cannot explain quantitatively the measured properties.

ISI Document Delivery No.: 109TF Times Cited: 0 Cited Reference Count: 173 Lacroix, Pascal G. Malfant, Isabelle Real, Jose-Antonio Rodriguez, Vincent Wiley-v c h verlag gmbh Weinheim Si; Various attempts to combine magnetic and nonlinear optical (NLO) properties in a molecule are reviewed, with a special focus on the possibility of interplay between the magnetic component and the quadratic (proportional to E-2) NLO response. This multidisciplinary research leads to the idea of spin-crossover-induced (SCO-induced) NLO switching and is evaluated at the synthetic level, with insights provided by computational chemistry. The need for nontraditional experimental setups to record NLO properties in the solid state is discussed.

International audience; For economic and ecological reasons, hydrogen is considered as a major energetic vector for the future. Hydrogen production via high temperature water vapour electrolysis (HTE) is a promising technology. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800 degrees C enables the use of metallic materials as interconnects. High temperature corrosion behaviour and electrical conductivity of a new Cr-free Fe-Ni-Co alloy were tested in cathode atmosphere (H-2/H2O) at 800 degrees C. The alloy exhibits a poor oxidation resistance but an excellent ASR parameter, as a result of the formation of a highly-conductive Cr-free surface spinel layer. Moreover, the role of water vapour and hydrogen was discussed and a diffusion mechanism in cathode atmosphere could be suggested.

For economical and environmental reasons, hydrogen is considered as a major energetic vector for the future. Hydrogen production via high temperature water vapour electrolysis (HTE) is a promising technology. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800°C enables the use of metallic materials as interconnects. Chromia forming alloys are among the best candidates. The interconnect material chosen in the present study is a ferritic stainless steel with 18% chromium content. High temperature corrosion resistance and electrical conductivity of the alloy was tested in both cathode (H2/H2O) and anode (O2/H2O) atmospheres. Corrosion products were then characterized by SEM-EDX and XRD. Moreover chromium evaporation measurements were carried out under anode atmosphere.