Search results for "engineering.material"
showing 10 items of 2352 documents
Multifunctional properties of nanocomposites made by 1D and 2D graphene based fillers
2015
High aspect ratio graphene based fillers with different dimensionalities showed the ability to greatly modify rheological, mechanical, thermal and electrical properties of polymers at very low content. In this work, the effect of filler dimensionality on the multifunctional properties of an epoxy matrix reinforced by both carbon nanotubes (1D) and graphite nanoplatelets (2D) have been investigated across the percolation region. Keywords-- Carbon nanotube, Graphite nanoplatelet, nanocomposites, mechanical properties, ...
Au–NiOx nanocomposite for hot electron-assisted plasmonic photocatalysis
2020
Nanocomposites of metal–oxide semiconductors containing Au nanoparticles are emerging multifunctional materials for sunlight-driven highly efficient photocatalysis. Here we report a solution-processed nanocomposite synthesis of Au–NiOx nanocomposite films by slot-die coating and plotter printing in a straightforward in situ synthesis approach. Our study demonstrated a significantly enhanced photocatalytic decomposition reaction of MO upon exposure of Au–NiOx films to a sunlight simulator. The excellent photocatalytic activity is ascribed to the generation of hot carriers after LSPR excitation in Au NPs. Suitable band alignment between the valence band of NiOx and the Fermi level of Au NPs l…
Dynamics of paramagnetic nanostructured rods under rotating field
2011
International audience; The dynamical rotational behavior of magnetic nanostructured rods based on the auto-association of maghemite nanoparticles and block-copolymers is probed by optical microscopy under rotating fields i n a s imple l iquid. The reorientation of the rods by a field rotated by 90° is first studied. The measured relaxation is characteristic of param-agnetic objects. Under a stationnary rotating field, a synchronous rotational regime is observed at low field frequency. Above a frequency threshold which scales as H^2 , the dynamics becomes asynchronous with back-and-forth rotations. These behaviors are well predicted by the presented model.
Synthesis of Titanate Nanotubes Directly Coated with USPIO in Hydrothermal Conditions: A New Detectable Nanocarrier
2011
International audience; Abstract: For the first time, titanate nanotubes (TiONts) coated with USPIO (ultrasmall superparamagnetic iron oxide) without polymer functionalization and directly obtained during TiONts formation is reported. The coating of these tubes was performed directly during the TiONts hydrothermal synthesis. After this treatment, in strongly basic conditions, USPIO particles kept their structure and magnetic properties while their size distribution slightly increased. By coupling zeta-potential measurements and TEM observations at different pH it appeared that interactions between nanotubes and USPIO were not electrostatic. This study presents the new design of a titanate n…
Exploiting the Colloidal Stability and Solubilization Ability of Clay Nanotubes/Ionic Surfactant Hybrid Nanomaterials
2012
Halloysite clay nanotubes are functionalized by exploiting the different charges between the inner positive and the outer negative surfaces; accordingly, a selective adsorption is pursued by employing anionic and cationic surfactants. The obtained hybrid materials dispersed in aqueous phase are studied from the physicochemical viewpoint to investigate the colloidal stability that is a crucial parameter for applications. It is demonstrated that the adsorption of anionic surfactant into the HNTs lumen increases the net negative charge of the nanotubes enhancing the electrostatic repulsions and consequently the dispersion stability. The solubilization capability of these functionalized nanotub…
Electrochemical behaviour of copper-nickel alloys as immobilisation matrices for the storage of fission products in CO2-enriched synthetic groundwater
2013
International audience; The surface properties of nickel and copper alloys exposed to simulated French Callovo-Oxfordien ground-water (aerated and CO2-saturated solutions) have been evaluated from electrochemical impedance spectroscopy in conjunction with X-ray photoelectron spectroscopy. The kinetic reactions and physical properties of the layers grown on the alloy's surfaces, change versus the Ni content in the alloys and the presence of CO2 in the solution. Nickel alloys retain favourable passive properties in such environments, whereas oxide products on copper alloys are insufficiently protective when formed in the absence of dissolved oxygen in the electrolyte. A maximum addition of 30…
Use of pure vanadium and niobium/copper inserts for laser welding of titanium to stainless steel
2020
Abstract Niobium and vanadium have high metallurgical compatibility with titanium and therefore can be used as inserts to avoid the accumulation of brittle intermetallic phases such as Fe2Ti during the fusion welding of titanium alloys with steels. In the present study, the continuous double pass welding of 1 mm thick Ti-6Al-4V alloy and 316 L stainless steel plates through several mm wide pure vanadium or niobium insert was studied. In case of a vanadium insert, a beam offset on the vanadium was found to produce cold crack formation in vanadium/316 L melted zones containing more than 40 wt.% V despite the absence of σ phase. Whereas a centered beam position and offset on the steel side pro…
Temperature- and Magnetic-Field-Dependent Longitudinal Spin Relaxation in Nitrogen-Vacancy Ensembles in Diamond
2011
We present an experimental study of the longitudinal electron-spin relaxation time (T1) of negatively charged nitrogen-vacancy (NV) ensembles in diamond. T1 was studied as a function of temperature from 5 to 475 K and magnetic field from 0 to 630 G for several samples with various NV and nitrogen concentrations. Our studies reveal three processes responsible for T1 relaxation. Above room temperature, a two-phonon Raman process dominates, and below, we observe an Orbach-type process with an activation energy, 73(4) meV, which closely matches the local vibrational modes of the NV center. At yet lower temperatures, sample dependent cross relaxation processes dominate, resulting in temperature …
One-pot synthesis of ZnO nanoparticles supported on halloysite nanotubes for catalytic applications
2020
Abstract A versatile catalyst based on halloysite and zinc oxide (HNT@ZnO) was prepared, for the first time, starting from ZnO commercial bulk form as Zn precursor source, in a one-pot procedure. This strategy gives the possibility to obtain small ZnO nanoparticles loaded on the HNT surface without the use of inorganic salts which envisage the removal of undesired anions and therefore a calcination process at high temperature. It was found that the presence of halloysite improved the UV–vis spectral absorption ability of ZnO. The hybrid was successful used as photocatalyst for the methylorange and rhodamine B degradation. In addition, after eight consecutive cycles for the methylorange phot…
Phased laser diode array permits selective excitation of ultrasonic guided waves in coated bone-mimicking tubes
2017
This paper validates simulation predictions, which state that specific modes could be enhanced in quantitative ultrasonic bone testing. Tunable selection of ultrasonic guided wave excitation is useful in non-destructive testing since it permits the mediation of energy into diagnostically useful modes while reducing the energy mediated into disturbing contributions. For instance, it is often challenging to distinguish and extract the useful modes from ultrasound signals measured in bone covered by a soft tissue. We show that a laser diode array can selectively excite ultrasound in bone mimicking phantoms. A fiber-coupled diode array (4 elements) illuminated two solid tubes (2-3mm wall thickn…