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Metal additive manufacturing is a rapidly growing field based on the fabrication of complex parts with improved performance. The advantages of using this technology include the production of shapes that cannot be produced by traditional machining technologies, the possibility of using trabecular reinforcing structures, and the ability to make parts with topological optimization that allow for increased performance and decreased mass of the parts produced. Metal parts produced by selective laser melting technology exhibit high surface roughness, which limits their direct implementation. Corrosion protection of these surfaces is difficult, especially for galvanic processes. This paper analyzes the possibility of using sol–gel silica (silicon oxide) coatings to effectively protect various surfaces of aluminum alloys produced by selective laser melting technology. Silicon oxide sol–gel protective coatings have demonstrated excellent chemical stability and corrosion resistance, being able to be applied in very thin layers. These properties make them excellent candidates for protecting additive-manufactured metal parts, especially as-built surfaces with a high surface roughness. Nanostructured silica sol–gel protective coatings have demonstrated excellent corrosion resistance and have the potential to replace the highly toxic chromium-based galvanic treatments. Using nanostructured silica sol–gel coatings, aluminum parts can be seamlessly integrated into circular-economy cycles.

In the last few years, there has been increasing interest in the processing of aluminum alloys using additive manufacturing (AM) processes. Thanks to their properties, aluminium alloys are extensively used in aerospace, rail, and automotive industries. Laser metal deposition (LMD), among the AM processes, can manufacture complex features as well as reinforcement structures on pre-existing complex parts. The work performed within the SAMOA project aims to expand the knowledge of the material properties of aluminum alloys when the LMD process is performed under atmospheric conditions. Both common alloys (AlSi10Mg, AlSi1Mg) and AM-specific alloys (AM205 and AlSi1Mg + 1 wt. %Zr) were analyzed and compared. Results show significantly lower amounts of internal defects and higher mechanical properties in AM-specific alloys. This database of mechanical properties will be used to design, simulate, and fabricate reinforcement structures on car frames to enhance their crash resistance and increase vehicle security. Moreover, to reduce material waste, the SAMOA project focuses also on the effects of powder recycling by analyzing both chemical and physical changes in the powder. The higher concentration of oxygen and hydrogen was separately analyzed by artificially increasing their concentration by heat treating AlSi10Mg powder. Results showed similar processability with a reduction in UTS of −31.4% and an increased elongation at fracture of +112.5%. Recycled powder, on the other hand, could not be easily collected, sieved, and reused since the identified physical and chemical changes of the powder lower its processability.

The research centres on the evaluation of surface integrity of AlSi10Mg parts produced via laser-based powder bed fusion (LPBF) process, followed by vibratory surface finishing. The alloy is chosen for its applications in lightweight components used in electronic packaging, automotive and aerospace sectors. Initial experiments involve optimisation of key LPBF process parameters by analysing the surface roughness and density data of the built parts. A Taguchi L18 orthogonal array is used for the optmisation trials with variations in the laser power (P), beam scanning speed (v), hatch spacing (H) and island size (I). Latter experimental phase deals with microhardness and microstructure assessment of heat treated LPBF specimens that are produced using the optimised LPBF parameters, i.e. P: 250 W, v: 1500 mm/s, H: 75 µm and I: 2 mm. Microhardnesses of the annealed samples reduce by ~12% with respect to the as-built parts and the values remain almost unchanged from the annealed state following solution treatment and ageing. The fish-scale like melt-pools observed on the unheat treated samples begin to fade off in the annealed specimens and completely disappear after solution treatment and ageing, with silicon particles dispersed all over the aluminium matrix. The final experimental phase involves vibratory surface finishing of the as-built LPBF parts using a vibrating ceramic media mixed with different acid and amine based liquid compounds for 1-6 hours, followed by vibrating in a maize based media for another 1-6 hours. The process aids in reducing the parts’ roughness, Sa by ~35-70%, however the effect is more prominent when using the ceramic media.

In this paper, ZnO electrodeposition was studied with the presence of graphene oxide (GO) exploited as a possible structure-directing agent. The effect of deposition potential and duration on the morphology and structure of ZnO was analyzed. The morphology and structure of the hybrids was analyzed by Raman spectroscopy, X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The Raman results indicate a successful modification of ZnO with GO sheets and a hybridization threshold of 10 mg L&minus, 1 by the evolution of the defect related band of ZnO at 580 cm&minus, 1. The morphology results show that a low GO content only slightly influences the morphology and orientation of ZnO nanostructures while a high content as 10 mg L&minus, 1 changes the morphology in nanoplates and growth orientation to lateral. The results show that while GO participated in the deposition reaction, it has a two-fold role, also by structure-controlling ZnO, indicating that the approach is valid for the use of GO as a structure-directing agent for the fabrication of ZnO nanostructures by electrodeposition with varying morphologies and orientations.

Novel hybrid core-shell nanoarchitectures were fabricated by a simple two-step electrochemical approach: first ZnO nanorod core was electrodeposited from Zn(NO3)2 solution; further, the core nanoarray was coated with a shell based on polypyrrole hybridized with graphene oxide by electropolymerization. The properties of the core/shell nanoarchitectures were studied as a function of the core properties induced by electrodeposition parameters. The ZnO nanostructures showed improved crystallinity and c-axis preferred orientation with increasing cathodic deposition potential while the increased deposition duration resulted in a morphology transition from nanorod to pyramidal shape. The electrochemical activity of the core/shell arrays was found to increase with the deposition potential of ZnO core but decreased when morphology changed from nanorod to pyramid shape. The photocatalytic results showed improved activity for the core/hybrid shell nanoarrays with respect to ZnO and ZnO/PPy ones. The degradation rate for methylene blue decreased with prolonged deposition duration of the core. The obtained results highlight the importance of electrochemical tuning of ZnO-based core/shell nanoarrays for improved performance in electrochemical and photocatalytic applications.

ZnO thin film and nanowire morphologies were employed to fabricate CO gas sensors by using radio frequency magnetron sputtering and chemical vapour deposition growth. The sensing properties were measured at CO gas concentration ranging from 10 to 50ppm at varying operating temperature. The results showed a 5-folded sensitivity and half-reduced response time for the hybrid material based on both thin film and nanowires with respect to thin film only, thus indicating the high potential of morphology tailoring, namely, the surface-to-volume ratio and depletion layer, for the enhancement of ZnO sensing performance. Display Omitted ZnO film/nanowire architecture was grown by sputtering and CVD techniques.CO gas sensing properties were studied in 10-50ppm concentration range.Higher surface-to-volume resulted in improved sensitivity at 400?C and faster response.Non-linear increase in sensitivity due to interconnection points and chemisorption processes

In this work, ZnO thin films were investigated to sense NO2, a gas exhausted by the most common combustion systems polluting the environment. To this end, ZnO thin films were grown by RF sputtering on properly designed and patterned substrates to allow the measurement of the electrical response of the material when exposed to different concentrations of the gas. X-ray diffraction was carried out to correlate the material's electrical response to the morphological and microstructural features of the sensing materials. Electrical conductivity measurements showed that the transducer fabricated in this work exhibits the optimal performance when heated at 200 degrees C, and the detection of 0.1 ppm concentration of NO2 was possible. Ab initio modeling allowed the understanding of the sensing mechanism driven by the competitive adsorption of NO2 and atmospheric oxygen mediated by heat. The combined theoretical and experimental study here reported provides insights into the sensing mechanism which will aid the optimization of ZnO transducer design for the quantitative measurement of NO2 exhausted by combustion systems which will be used, ultimately, for the optimized adjustment of combustion resulting into a reduced pollutants and greenhouse gases emission.

High-performance permanent magnets (PM) are compounds with outstanding intrinsic magnetic properties. Most PMs are obtained from a favorable combination of rare earth metals (RE = Nd, Pr, Ce) with transition metals (TM = Fe, Co). Amongst them, CeFe11Ti claims considerable attention due to its large Curie temperature, saturation magnetization, and significant magnetocrystalline anisotropic energy. CeFe11Ti has several potential applications, in particular, in the development of electric motors for future automatic electrification. In this work, we shed some light on the mictrostructure of this compound by performing periodic hybrid-exchange density functional theory (DFT) calculations. We use a combined approach of atom-centered local orbitals, plane waves and full-potential linear muffin-tin orbital (LMTO) for our computations. The electronic configuration of the atoms involved in different steps of formation of the crystal structure of CeFe11Ti gives an explanation on the effect of Ce and Ti on its magnetic properties. While Ti stabilizes the structure, atomic orbitals of Ce hybridizes with Fe atomic orbitals to a significant extent and alters the electronic bands. Our calculations confirm a valence of 3+ for Ce, which has been deemed crucial to obtain a large magnetocrystalline anisotropy. In addition, we analyze several spin configurations, with the ferromagnetic configuration being most stable. We compare and contrast our data to those available and provide an insight for further development of optimized high-performance PMs. Moreover, we compute the Magnetocrystalline Anisotropy of this compound by means of two approaches: the Force Theorem and a full-potential LMTO method.

A disadvantage of selective laser melting (SLM) processes for the manufacture of large parts is their slow build time per unit volume. A hybrid route is to generate core simple shapes traditionally, for example by machining, followed by adding final features by SLM. Here the mechanical integrity of such hybrid parts is studied, choosing the building of AlSi10Mg by SLM on a machined AA6082 base, in the shape of a tensile test piece, as a simple example. These materials are chosen for their relevance to lightweight parts. As-built parts fail at the SLM/machined interface but standard heat treatments transfer failures to the machined material. Optimised SLM processing conditions and microstructures of the SLM and interfacial regions are reported.

Despite the ground-breaking potential of nanomaterials, their safe and sustainable incorporation into an array of industrial markets prompts a deep and clear understanding of their potential toxicity for both humans and the environment. Among the many materials with great potential, graphene has shown promise in a variety of applications; however, the impact of graphene based products on living systems remains poorly understood. In this paper, we illustrate that via exploiting the tribological properties of graphene nanosheets, we can successfully improve both the frictional behaviour and the anti-wear capacity of lubricant oil for mechanical transmission. By virtue of reducing friction and enhancing lubricant lifetimes, we can forecast a reduction in friction based energy loss, in addition to a decrease in the carbon footprint of vehicles. The aforementioned positive environmental impact is further strengthened considering the lack of acute toxicity found in our extensive in vitro investigation, in which both eukaryotic and prokaryotic cells were tested. Collectively, our body of work suggests that by the use of safe nanoadditives we could contribute to reducing the environmental impact of transportation and therein take a positive step towards a more sustainable automotive sector. The workflow proposed here for the evaluation of human and environmental toxicity will allow for the study of nanosized bare graphene material and can be broadly applied to the translation of graphene-based nanomaterials into the market.

The fabrication of whole Al-doped ZnO nanostructured electrodes is reported by a two-step technology. Magnetron sputtered Al-doped ZnO (AZO) films were investigated as seeding substrates for the electrodeposition of Al-doped ZnO nanorod arrays. The nucleation, density, morphological and structural properties of Al-doped ZnO NRAs were analyzed as a function of precursor concentration and substrate and compared to undoped ZnO NRAs. High density and good crystal quality are reported for the Al-doped ZnO NRAs grown on AZO films from low precursor concentration.

In this work, we evaluated the piezoelectric properties of the ZnO nanorods (NRs), subsequently grown by a template-free electrochemical deposition (ECD) approach. The one-step preparation method yielded in a relatively short-time synthesis large arrays of high aspect-ratio ZnO NRs, vertically aligned to the substrate and exhibiting a well-defined hexagonal symmetry coupled with an excellent crystallinity. Piezoresponse force microscopy (PFM) was employed to extract the effective piezoelectric coefficient ( d 33 ) of the ZnO [0 0 0 1]-oriented NRs. A mean effective d 33 coefficient of 11.8 pm/V was measured over several individual NRs. The results have shown an increased piezoelectric response of the ZnO NRs, with ∼18% in respect to the ZnO bulk material, and with a factor ranging from 28% to 167% compared to similar ZnO nanostructures prepared by other counterpart techniques. Both morphology and crystalline quality of the obtained ZnO NRs, as well as the piezoelectric investigations, ranked the ECD as a promising low-cost pathway for possibly producing high quality nanostructured ZnO-based piezoelectric devices with enhanced performance.

Green reduction of graphene oxide (GO) functionalized with 3-aminopropyltriethoxysilane and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide was performed by using ascorbic acid and sodium bisulfite. The obtained materials were characterized by thermo-gravimetric analysis, transmission electron microscopy, X-ray diffraction, UV‒Vis, Fourier transform infrared and Raman spectroscopy techniques. The results indicated a strong dependence of the materials properties such as deoxygenation degree, absorption peak shift, crystallite size and functionalization degree on the functionalization approach and reducing agent.

The potential application of graphene nanoplatelets as electrode material in supercapacitors with high energy density was investigated. The electrode were prepared with commercially available graphene nanoplatelets before and after being functionalized with MnO2 particles, and with those electrochemically exfoliated from graphite. The morphology, structure and the specific surface area properties of each material were analyzed prior to test the electrochemical performance of the corresponding electrodes under the design constraints of real devices by cyclic-voltammetry (CV) and charge/discharge (CD) measurements. The results indicated that graphene nanoplatelets show potential in replacing activated carbon for the fabrication of supercapacitors with high energy density, while the efficient usage of active surfaces available of the electrode material should be considered.

[EN] Large areas of reduced graphene oxide (rGO) films were obtained by electrophoretic deposition onto insulating glass substrate. ZnO nanostructures were directly grown on the rGO films by single-step electrodeposition method. The properties of ZnO nanostructures were evaluated as a function of deposition mode onto rGO electrodes with different stoichiometry. Atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetrical analysis (TGA), transmission measurements, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to characterize the obtained materials. Bi-pod morphology was observed for ZnO electrodeposited on rGO films by pulsed current elelctrodeposition. The obtained ZnO/rGO hybrid structures show high potential for highly transparent optoelectronic nanodevices., Financial support from Romanian Authority for Scientific Research-UEFISCDI (project no. PN-II-RU-PD-2012-3-0124) and European Commission (project no. NMP3-SL-2010-246073) is gratefully acknowledged. The authors also thank for the support given by the Microscopy Service and Institute of Chemical Technology (ITQ)-Universidad Politecnica de Valencia.

Surface studies are reported for the deposition of ZnO nanostructures by one-step electrodeposition method. The electrosynthesis was perfomed at the surface of tin doped indium oxide coated glass substrates in the absence of any buffer layer. The growth of ZnO nanostructures was investigated with the morphology of substrate and the deposition mode. Combined nucleation mode was observed for the ZnO independently of substrate. The results indicated the growth, morphology and density of the ZnO nanostructures are markedly influenced by both the substrate and the deposition conditions. It was observed the ZnO formation is defect site driven in case of galvanostatic deposition mode, while in case of potentiostatic deposition mode, it is dependent on the roughness of the substrate.

ZnO-nanostructured films were obtained by electrodeposition in the presence of varying content of graphene oxide (GO) in reduced (rGO) and non-reduced state. The hybridized ZnO nanostructures were studied by X-ray diffraction measurements, scanning electron microscopy, atomic force microscopy and Raman spectroscopy and transmittance measurements. The results showed the ZnO structure and morphology are markedly influenced by graphene state (GO/rGO) and content. The photocatalytic tests indicated the ability of electrodeposited ZnO-nanostructured films to photodegrade methylene blue depends on the morphology and structure characteristics induced by both on oxygen content and sp2 recovery of carbon network in the rGO, upon a fine tuning of the rGO content in the deposited films. The obtained results demonstrate the electrodeposition as a viable approach for tuning the properties of ZnO complex structures for improved performance in various fields of application such as photocatalysis or optoelectronics.

Noble metallic nano-catalysts supported on carbon based substrates are extensively used as electrodes for direct methanol fuel cells (DMFCs). Pd is a promising alternative to the more expensive Pt whether its catalytic properties should be improved. To this aim, reduced graphene oxide (rGO) was employed in this study as an alternative to conventional carbon black (C) substrates to improve the catalytic properties of Pd. Pd nanobars and Pt nanoparticles were synthesized, by the polyol method, and deposited for comparison both on commercial carbon and rGO. The oxygen reduction reactions (ORRs) at the fabricated electrodes were tested by the Rotating Disk Electrode (RDE) technique in acidic media. To correlate the activity to other physico-chemical properties, the nano-catalysts were characterized by Thermo Gravimetric Analysis (TGA), X-Ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The electro-catalytic activity of the electrode is importantly affected by the support chosen. Specifically, the Pd nano-catalyst proved an enhanced performance when on rGO, while the Pt counterpart was found being more active when placed on C. This result can be explained with a strong dependence of the ORR on the interaction between the metal nano-catalyst and the carbon based support. (C) 2013 Elsevier B.V. All rights reserved.

Layered oxide heterostructures show interesting properties that encompass those of the standalone moieties; hence, a detailed understanding of the interface is key to the development and use of such materials. In this work, we have performed quantum-chemical ab initio calculations to give a complex description of structural and electronic properties of epitaxial growth ZnO/LaMnO3 (ZnO/LMO) interfaces. The Crystal code, which uses a local (Gaussian) basis set, is used to design and characterize ZnO/LMO heterostructures including (1120) and (1010) nonpolar overlayers of ZnO on LMO(001), supported from simpler formulation to hybrid functionals of density functional theory. The applied structural models and coincidence cells are described and illustrated in detail. We discuss the impact of different termination of LMO through stability (computed strain and adhesion energies) and structural and electronic properties (density of states and 3D charge density differences). The ZnO(1120) overlayer shows the les...

Heterostructures formed by La0.7Sr0.3MnO3/ZnO (LSMO/ZnO) interfaces exhibit extremely interesting electronic properties making them promising candidates for novel oxide pn junctions, with multifunctional features. In this work, the structure of the interface is studied through a combined experimental/theoretical approach. Heterostructures were grown epitaxially and homogeneously on 4″ silicon wafers, characterized by advanced electron microscopy imaging and spectroscopy and simulated by ab initio density functional theory calculations. The simulation results suggest that the most stable interface configuration is composed of the (001) face of LSMO, with the LaO planes exposed, in contact with the (112̅0) face of ZnO. The ab initio predictions agree well with experimental high-angle annular dark field scanning transmission electron microscopy images and confirm the validity of the suggested structural model. Electron energy loss spectroscopy confirms the atomic sharpness of the interface. From statistical parameter estimation theory, it has been found that the distances between the interfacial planes are displaced from the respective ones of the bulk material. This can be ascribed to the strain induced by the mismatch between the lattices of the two materials employed.

Among the most promising nanomaterials, an extensive emphasis was drawn onto graphene-based ones for biomedical applicability, being triggered by its exotic properties such as biocompatibility, electric conductivity, and transparency, excellent aqueous processability, amphiphilicity and surface functionalisation degree. The tuneable chemistry and the excellent mechanical, tribological, as well as corrosion properties of graphene-based materials have indicated their potential applications in implant material. Given the growing demand for designing advanced new implant surfaces to control the interactions with the surrounding biological environment in order to improve their biocompatibility and bioactivity and enhance their corrosion resistance, this chapter highlights the approaches for surface modification of dental implants with graphene nanomaterials as surface coatings.

Boron nitride-substituted graphene (BNsG) two-dimensional structures are new materials of wide technological interest due to the rich variety of electronic structures and properties they can exploit. The ability to accurately characterize them is key to their future success. Here we show, by means of ab initio simulations, that the vibrational Raman spectra of such compounds are extremely sensitive to substitution motifs and concentration, and that each structure has unique and distinct features. This result can be useful as a guide for the optimization of production processes.

Single-crystal ZnO nanowires long up to several microns were fabricated by one-step electrochemical deposition. A template-based process employing track-etched polycarbonate (TE-PC) membranes was used for this purpose. The morphology and the structure characteristics of the ZnO nanowires were analyzed by means of Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB), Transmission Electron Microscopy (TEM), and Selected Area Electron Diffraction (SAED). The growth process conditions turned out to have a marked influence on the crystal nature and morphology of the nanowires. Deposition rates ranging from 0.4 nm s -1 and up to 0.6 nm s -1 were recorded for the growth of ZnO nanowires. The obtained results showed that by using carefully controlled deposition conditions single crystalline nanowires and fine-grained structures can be routinely obtained. © 2012 The Electrochemical Society., This work was supported by the European Commission through the program PEOPLE, by the project no. MRTN-CT-2006-035884.

Co/Cu-multilayer nanowires can be exploited to develop magnetoresistive sensors. One of the easiest methods for their production is filling nanoporous templates by pulsed-electrodeposition (PED) from a single bath. Multiple parameters effecting the growth of these nano-objects must be controlled to tailor their properties. In this study, the deposition efficiency of Co/Cu-multilayer nanowires produced in nanoporous-polymeric membranes is assessed, and the influence of the space confinement produced by the nanopores themselves on the continuous and pulsed-electrodeposition is evaluated. The growth dependence on some of the most significant process parameters has been investigated. It is shown here that, for each species, when depositing Co and Cu separately, a decrease of current efficiency is observed when the charge density is increased and the pore diameter is reduced; on the contrary, in the Co/Cu-PED, changing the degree of polarization for each deposition step of the different metals results in a sensible reduction of this effect.

Funded by the EC FP7 Program, EVolution project is using the Pininfarina Nido concept car as a baseline for its activities, with the goal to demonstrate the sustainable production of a full electric 600 kg vehicle (FEV). The project has to be finalized by the end of 2016. The existing Body in White (BiW) has been completely reviewed through a design strategy aiming to reduce the number of parts and using innovative lightweight materials and technologies. The considered Al technologies applied on high performances Al alloys provide the opportunities to obtain components with complex geometries and low thickness, merging different parts into one unique element. Besides, it is possible to process a variable thickness element with a single operation. A “green sand mold” technique allows co-casted joints among elements produced with different Al manufacturing processes. The potential cost reduction and process simplification in terms of time and assembly are promising: current state-of-the-art, based on traditional moulds, does not allow these opportunities. The BiW has been hybridized in certain areas of the underbody with a composite material of the PA family, reinforced with GF. This material has been obtained improving existing ones and developing a production process suitable for scaling to commercial requirements, throughout an advanced sheet thermoforming and 3D-injection method (CaproCAST process). Novel polypropylene nanocomposites (PNC) based on silicate and glass fiber layers demonstrate improved toughness and stiffness and have been selected for crash cross beam and side door. Polyurethane foams based on recycled polymers are explored as sustainable energy-absorbing filling in cross beam sections. Structural epoxy adhesives have been considered to join the BiW parts and welding points are reduced in number: in certain areas spot-welds have been used only to tack the parts during polymerization. In addition to the previous results, current weight of the BiW is 115 kg versus 160 kg of the baseline car. An FE-analysis on the virtual full vehicle indicates a good structural behavior, considering EU standards of crash homologation and global static and dynamic performances. The developed architecture and the integration of lightweight materials will ensure that the EU maintains its competitiveness against the Asian and United States automobile industries. This topic is focused on the results obtained on the BiW in terms of design strategies, Al and composite materials innovative technologies and joining methods. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 314744.

The critical Josephson current (IC) in superconducting/ferromagnetic (S/F) multilayer-based junctions can be controlled by changing the relative directions of the magnetization in the F-layers. Recent experimental works [1, 2] show that an enhancement of IC is achieved in S/F weak links when the alternating F-layers are antiparallel aligned. We present preliminary experimental results concerning the dependence of IC on the relative orientation of the ferromagnetic layers in S/F1/I/F2/S tunnel junctions where the F-layers are obtained by changing the relative composition of NiCu alloys. The multilayers were grown by electron beam deposition, and processed by Focused Ion Beam lithography. The magnetic state of the devices was directly determined by measuring the current perpendicular to plane (CPP) magnetoresistance (MR) at high bias. IC was found to be larger when the F-layers are antiparallel aligned. The maximum change of IC corresponds to the maximum change of MR. The application of a magnetic field induces a transition in the shape of the currentvoltage curve that seems to suggest Coulomb blockade effect.

Monodispersed spheres of ferromagnetic metals like iron, cobalt, and nickel can be synthesized on a micrometric and sub-micrometric scale by simply reducing their salts with boiling polyols. These magnetic particles embedded into a polymeric matrix can be exploited for a number of technological applications (e.g., barcodes for magnetic encoders, magnetic storage media, electromagnetic shielding). The spherical shape of particles allows to prepare composites with high filling factors and very uniform filler distribution. In addition, because ferromagnetic particles show size-dependent magnetic properties (e.g., coercivity), the possibility to control the particle size is of primary importance. Here, we have found that monodispersed cobalt spheres of different sizes can be obtained by reduction of cobalt hydroxide with diethylene glycol. The average particle size was related to the precursor amount and it was widely varied by simply controlling this parameter. Disproportion in ethylene glycol mediu...

A fast approach based on microwave technology was employed for the sintering of novel composites of alumina and using graphene oxide (GO) as susceptor. The thermal stability and structure of GO materials produced by chemical oxidation of graphite were characterized. The morphology, structure and mechanical properties of the composites sintered by microwave approach were reported to the counterparts sintered by conventional method. The results indicated the formation of an interconnecting graphene network promoted the electrical conductivity in the composite having only 2 wt.% GO. Hardness and elastic modulus decreased significantly in samples sintered by conventional method due to lower values of density while microwave technology allowed to achieve a positive effect on the densification and showed a smaller grain size when compared to the one achieved by conventional heating. (C) 2014 Elsevier Ltd. All rights reserved., Financial support from European Commission (project no. NMP3-SL-2010-246073), Universidad Politecnica de Valencia (project SP20120677) and Ministerio de Economia y Competitividad - MINECO (project TEC2012-37532-C02-01, co-funded by ERDF (European Regional Development Funds) is gratefully acknowledged. A.B. acknowledges the Spanish Ministry of Science and Innovation (contract JCI-2011-10498). A.P. acknowledges support from Romanian Authority for Scientific Research - UEFISCDI (project no. PN-II-RU-PD-2012-3-0124).

We have investigated the gas sensing properties of ZnO thin films (100 to 200 nm thickness) deposited by room-temperature radio frequency magnetron sputtering. The sensitivity of the films to ethanol vapor was measured in the 10 to 50 ppm concentration range at operating temperatures between 200 and 400 °C. A synergetic effect of decreasing grain size and increasing operating temperature was observed towards the improvement of the sensitivity, reaching a value of 54 and a limit of detection as low as 0.61 ppm. The decrease in the grain size resulted in prolonged response time but faster recovery. In any case, both response time and recovery time are < 400 s. The results demonstrate that room-temperature magnetron sputtering is a viable approach to enhance the performances of ZnO films in sensors for ethanol vapor.

A simple chemical approach was employed to reduce graphene oxide in order to fabricate electrode coatings in close correlation with industrial production standards for supercapacitors. The morphology, structure, thermal stability and the residual oxygen functional groups in chemically reduced graphene oxide were analyzed. Cyclic voltammetry and charge/discharge measurements were employed to study the electrochemical performance of the coatings as a function of active material loading. The results showed an increase in the specific capacitance for chemically reduced graphene oxide-based coatings in comparison to commercial activated carbon, while the desired value needs to be optimized with respect to the conductivity of such materials.

The process of magnetization reversal in ultrathin magnetic trilayer is analyzed. It is shown that the shape of magnetization hysteresis loops and the giant magnetoresistance essentially depend on the relative magnitudes of magnetic parameters of the top and the bottom layers. New types of hysteresis loops are found for characteristic relative magnitudes of the parameters. Analysis of the dependence of the shape of hysteresis loops on the magnitude of interlayer exchange is performed. The phase diagram which determines the regions of existence of characteristic hysteresis loops for different relative magnitudes of the uniaxial anisotropy constant and exchange constant J 1 is constructed.

[EN] We propose a model for the consistent interpretation of the transport behavior of manganese perovskites in both the metallic and insulating regimes. The concept of polarons as charge carriers in the metallic ferromagnetic phase of manganites also solves the conflict between transport models, which usually neglects polaron effects in the metallic phase, and, on the other hand, optical conductivity, angle-resolved spectroscopy, and neutron scattering measurements, which identify polarons in the metallic phase of manganites down to 6 K. Transport characterizations of epitaxial La0.7Sr0.3MnO3 thin films in the thickness range of 5-40 nm and temperature interval of 25-410 K have been accurately collected. We show that taking into account polaron effects allows us to achieve an excellent fit of the transport curves in the whole temperature range. The current carriers density collapse picture accurately accounts for the properties variation across the metal-insulator transitions. The electron-phonon coupling parameter gamma estimations are in a good agreement with theoretical predictions. The results promote a clear and straightforward quantitative description of the manganite films involved in charge transport device applications and promises to describe other oxide systems involving a metal-insulator transition., The authors P.G., A.G., M.P., A.R., and I.B. thank F. Bona for technical help and A. Dediu and V. Kabanov for fruitful discussions. Financial support from the FP7 Projects No. NMP3-LA-2010-246102 (Interfacing oxides, IFOX), No. NMP-2010-SMALL-4-263104 (Next generation hybrid interfaces for spintronic applications, HINTS), No. NMP3-SL-2010-246073 (Graphene for nanoscaled applications, GRENADA), and the Italian government FIRB (Molecular nanomagnets on metallic and magnetic surfaces for applications in molecular spintronics) Project No. RBAP117RWN is acknowledged.

We present novel low-field magnetoresistive devices based on the ferromagnetic manganite La0.7Sr0.3MnO3 operating in the current in plane (CIP) configuration. In these planar spin-valve devices, a focused Ga+ beam is used to create pinning centers for magnetic domain walls. The spin-dependent scattering of polarized electrons at the domain walls (DW) is responsible for the magnetoresistance observed in the patterned tracks. The magneto-transport properties of these devices are interpreted within a model for DW magnetoresistance. Applications such as magnetic data storage can be envisaged for the structures we investigated. (C) 2006 Elsevier B.V. All rights reserved.

This article describes for the first time the preparation of conducting track-etched PBI membranes 25 mm thick with pore diameter values varying from 15 nm to 50 nm and overall porosity up to 10%. The TGA, DSC and FTIR characterization results for the so obtained nanoporous membranes reveal the chemical modification of PBI upon irradiation along the track walls. A clear conduction outperforming is shown by phosphoric acid doped track-etched PBI in comparison with dense PBI counterparts. This behavior could be explained by the effective contribution of additional pathways for proton transport involving shorter benzimidazole fragments, cross-linked PBI nanodomains and free amphoteric phosphoric acid molecules settled on the pore walls.

This study reports a novel method of tailoring the properties of ZnO nanostructures by electrodeposition in presence of chemically-reduced graphene oxide (rGO). The coupled electrochemical and chemical reduction of graphene oxide resulted in few-layer graphene-based material. The presence of rGO in the electrolytic bath showed a marked influence on the morphology and structure of the hybrid nanostructures. The results indicated the presence of 5 mg L 1 rGO results in a 42.9% decrease in resistivity of the hybrid material with respect to the pure ZnO. The proposed approach shows very promising for the fabrication of transparent conductive oxide electrodes., Financial support is gratefully acknowledged from the European Commission (Project no. NMP3-SL-2010-246073) and Romanian Authority for Scientific Research - UEFISCDI (Project no. PN-II-RU-PD-2012-3-0124). The authors would like to thank the support given by the Microscopy Service and Institute of Chemical Technology (ITQ) from the Universidad Politecnica de Valencia (Spain).

[EN] Cation-exchange membranes made exclusively from ceramic materials have been synthesized by means of the impregnation of microporous ceramic supports with zirconium phosphate. Changes in the pore size distribution and total pore volume of the supports were provoked by the addition of starch as pore former in the fabrication procedure. This allowed the production of supports with increased effective electrical conductivities and with larger pores available for the zirconium phosphate deposition. An improved functionality for the exchange of cations was given to the ceramic membranes by means of their impregnation with the active particles of zirconium phosphate. The ion-exchange properties of the membranes were increased with further impregnation cycles and the resulting current–voltage curves showed a similar shape to that typical of commercial polymeric ion-exchange membranes. The production of ionexchange membranes with increased chemical and radiation stability will broaden their applicability for the treatment of specific industrial waste waters, which are very aggressive for the current commercial ion-exchange membranes., The authors acknowledge the technical help from Federico Bona at CNR-ISMN in Bologna and the extensive use of the scanning probe microscopes at "Centro Interfacolta Misure" of the University of Parma. Financial support from the FP7 Projects NMP-2010-SMALL-4-263104 (HINTS), NMP3-SL-2010-246073 (GRENADA), and NMP3-LA-2010-246102 (IFOX) is acknowledged.

[EN] Green reduction of graphene oxide (GO) was performed using ascorbic acid (AA) in the presence of poly(sodium 4-styrenesulfonate), which resulted in reduced graphene oxide (PSS-rGO) with excellent solubility and stability in water. Large rGO sheets of 4 mu m(2) area and 1.1-nm thickness were obtained. The measurements showed that noncovalent functionalization with PSS molecules prevented rGO from aggregation. The parameters of graphite oxidation process and AA: GO w/w ratio were evaluated, and the obtained results showed that the properties of the reduced material (PSS-rGO) can be tailored by proper selection and adjustment of these parameters., The authors thank the European Commission for their financial support through the project no. NMP3-SL-2010-246073.

No abstract available.

In the present work an effective technique to synthesize large-scale c-axis oriented ZnO nanorod (NR) arrays is presented. The manuscript reports a single-step cathodic electrodeposition, either in aqueous and organic electrolytes, to fill up ultra-thin anodic nanoporous alumina templates. Prior to growing, self-ordered hexagonal array of cylindrical nanopores have been fabricated by anodizing Al thin films previously deposited onto ITOglass substrates. The diameter and the aspect ratio of the vertically aligned nanopores are about 60 nm and 8:1, respectively. The results of this work demonstrate that using dimethyl sulfoxide (DMSO) as an electrolyte leads to a growth more homogeneous in shape and crystallinity, and with 60 deposition efficiency - the highest by now in literature. This fact is most probably due to a better infiltration of the alumina nanopores by this electrolyte. SEM and XRD analysis were employed for the study of morphology and crystalline structure of the obtained ZnO NR. These measurements showed furthermore that ZnO nanorod arrays are uniformly embedded into the hexagonally ordered nanopores of the anodic alumina membrane. DMSO proved to be an optimal electrolyte to obtain single-crystalline ZnO NR arrays, highly transparent in visible light range (80 transmittance). © 2011 The Electrochemical Society., The authors thank for the financial support by the European Commission, DG Research through the program PEOPLE, by the project no. MRTN-CT-2006-035884.

The mechanical properties of GNP/LDPE nanocomposites (graphite nanoplatelets/low density polyethylene) have been investigated, in order to establish the effect of nanoscale reinforcement within the polymer matrix. Results show that the presence of the filler does not involve a change in the microscopic structure of the polymer. However, on a macroscopic scale, GNPs limit the mobility of the polymer chains, resulting in an increase in stiffness for the final composite. Orientation of GNPs within the LDPE matrix is also an important issue that affects mechanical properties and it has been evaluated by testing nanocomposites made by different manufacturing techniques (compression moulding and blown extrusion). The comparison between the experimental data and the Halpin?Tsai model shows that the orientation of GNPs due to the extrusion process leads to values of tensile modulus higher than that obtained with the randomly oriented disposition resulting from the compression moulding technique.

Since the discovery of giant magnetoresistance (GMR) in 1988 by Albert Fert and Peter Grunberg many companies have sought to develop practical applications for this intriguing effect of magnetic multilayer stacks. The applications of magnetic multilayer stacks are diverse, but in general they can serve as: magnetic field sensors (Simonds, 1995; Grunberg et al., 1986; Saurenbach et al., 1988; Baibich et al., 1988), non-volatile memories (Manalis et al., 1995; Chou et al., 1994), or variable resistors when small magnetic fields have to be measured. The first GMR sensor commercially available was introduced in 1995 by NVE Corporation. Since then, users can rely on a large variety of devices exploiting GMR: analogue and digital sensors, switches, gradient transducers for contactless positioning systems, e.g. gear tooth and encoder applications. Today, it is generally acknowledged that GMR sensors outperform the competing technologies such as AMR and Hall virtually in every application, and often at a significantly lower cost. The conventional GMR stacks are produced by vacuum deposition technology; more specifically, by this technique, a large variety of thin film materials are serially deposited, within a single vacuum chamber, one on top of another, to form multilayer stacks of tailored magnetic properties. The need to accurately control the nanometric thickness of each film, their extremely low roughness, and their purity do majorly contribute to the final cost of this type of systems. For this reason, the use of these devices, especially in low-margin markets such as the automotive, is still prohibitive for a number of potential field applications. In this context, alternative processes are envisaged to lower the final cost of GMR sensors. To this end, the pulsed electrodeposition into nanoporous templates (hereinafter template pulsed electrodepostion, TPED) is presented here as a competitive alternative to mass produce GMR sensors in the form of arrays of multilayer nanowires. As being a promising candidate for a low-cost production of sensors tailored for the aforementioned field uses (Pullini et al., 2007a), Co/Cu multilayer nanowire arrays fabricated by TPED (Fert & Piraux, 1999; Piraux et al., 1994) are discussed in this chapter. Specifically, the present chapter aims at presenting the criteria to model, design, develop Co/Cu-multilayer nanowire arrays, and discuss their potential exploitation perspectives to be used as magnetic field sensors. In a first part of this chapter a quasi-analytical analysis (QAD) of cylindrical Co/Cu/Co trilayer systems is detailed, and the equations drew to calculate the critical fields, the linearity

The authors have performed experiments on current-induced domain wall (DW) displacement in La0.7Sr0.3MnO3 nanostructures patterned by gallium (Ga) focused-ion-beam milling. A dc current is found to assist or hinder, according to polarity, an external magnetic field in the depinning of a DW trapped in a nanoconstriction. For large enough currents, the DW depinning occurs in the absence of external magnetic field. The depinning current depends on the transverse anisotropy constant of the region toward which the DW is displaced.

Monodispersed spheres of ferromagnetic metals like iron, cobalt and nickel, can be synthesized on a micrometric and sub-micrometric scale by simply reducing their salts with boiling polyols. These magnetic particles embedded into a polymeric matrix can be exploited for a number of technological applications (e.g., barcodes for magnetic encoders, magnetic storage media, electromagnetic shielding, etc.). The spherical shape of particles allows to prepare composites with high-filling factors and very uniform filler distribution. In addition, since ferromagnetic particles show size-dependent magnetic properties (e.g., coercivity), the possibility to control the particle size is of primary importance. Here, we have found that monodispersed cobalt spheres of different sizes can be obtained by reduction of cobalt hydroxide with diethylene glycol in presence of oleic acid. This organic compound absorbs on the metal surface, increasing compatibility with polymer in the resulting composite. The average particle size was related to the precursor amount and it was widely varied by simply controlling this parameter. Disproportion in ethylene glycol medium of in situ generated iron hydroxide (at 140 °C) has been used to produce monodispersed iron nanoparticles.