National Institute Of Materials Physics - Romania

This article reports the synthesis and characterization of several types of organic-inorganic nanocomposites based on epoxy resin/monoglycidylether-terminated poly(dimethylsiloxane) reinforced with 2, 5, or 10 wt% polyhedral oligomeric silsesquioxanes (POSS) bearing one glycidyl (1GE-POSS) or eight glycidyl(8GE-POSS) groups. The morphological features of the studied samples were established through atomic force microscopy, contact angle measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy, and it was demonstrated that 8GE-POSS is well dispersed within the polymer matrix, while 1GE-POSS exhibits a high tendency to form aggregates. Differential scanning calorimetry (DSC) and Fourier transform infrared resonance (FTIR) measurements are used to follow the curing behavior and to study the polymerization kinetics of epoxy groups. As evidenced by DSC and FTIR results, the inclusion of 8GE-POSS within the polymer matrix leads to a lower epoxy polymerization rate of the resulted nanocomposites than those reinforced with 1GE-POSS. The dynamic mechanical analysis results revealed that the thermomechanical properties are gradually improved with increasing of 8GE-POSS content due to the higher cross-linking density.

Superparamagnetic iron oxide nanoparticles (SPION) have attracted a lot of interest due to their widespread biomedical and diagnostic applications. Coating the SPIONs with various surface layers can provide an interface between the core and the surrounding environment. The aim of this study was to examine the in vivo behaviour of dextran-coated iron oxide nanoparticles (D-IONPs) in aqueous suspensions. The SPIONs stabilized with dextran (D-IONPs) were synthesized in aqueous solutions by co-precipitation method. The average grain size deduced from transmission electron microscopy is 7.5 nm. The hematological parameters registered for the rats exposed to D-IONPs at 1 ml/kg have had values approximately equal to those examined for the control specimen. The architecture of liver and kidneys was not affected after one day of intraperitoneal injection of D-IONPs compared to the reference group. After 21 and 28 days respectively from the administration of the D-IONPs solution, the liver and kidneys from the injected rats showed a normal aspect without abnormalities compared to the rats uninjected. Our findings suggest that the administration of 1 ml/kg D-IONPs did not cause any toxicological effect since the parameters of renal and liver function were in the normal range as reported to the control group.

Heterostructures based on zinc phthalocyanine (ZnPc), magnesium phthalocyanine (MgPc) and 5,10,15,20-tetra(4-pyrydil)21H,23H-porphine (TPyP) were deposited on ITO flexible substrates by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Organic heterostructures containing (TPyP/ZnPc(MgPc)) stacked or (ZnPc(MgPc):TPyP) mixed layers were characterized by X-ray diffraction-XRD, photoluminescence-PL, UV-vis and FTIR spectroscopy. No chemical decomposition of the initial materials was observed. The investigated structures present a large spectral absorption in the visible range making them suitable for organic photovoltaics applications (OPV). Scanning electron microscopy-SEM and atomic force microscopy-AFM revealed morphologies typical for the films prepared by MAPLE. The current-voltage characteristics of the investigated structures, measured in dark and under light, present an improvement in the current value (similar to 3 order of magnitude larger) for the structure based on the mixed layer (Al/MgPc:TPyP/ITO) in comparison with the stacked layer (Al/MgPc//TPyP/ITO). A photogeneration process was evidenced in the case of structures Al/ZnPc:TPyP/ITO with mixed layers. (C) 2015 Elsevier B.V. All rights reserved.

Thin amorphous films based on gallium-chalcogen (Ga-Ch), namely Ga2S3, Ga2Se3, Ga2Te3, and GaTe have been prepared by pulsed laser deposition (PLD). The films were characterized by X-ray diffraction, extended X-ray absorption fine structure (EXAFS), energy-dispersive X-ray spectroscopy (EDX), optical transmission spectroscopy, ellipsometry, and electrical measurements. Structural measurements showed that Ga is threefold coordinated, except the Te-based alloys were, it seems, only twofold coordinated, while the chalcogen is usually twofold coordinated. In all the compositions, layered and chain-like structures are assumed. The bandgaps range between 1.09 eV for Ga2Te3 and 2.21 eV for Ga2Se3. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Ex-situ spark plasma sintering (SPS) was used to obtain dense MgB2-based tapes in a Fe sheath with the starting composition (MgB2)(0.975) + (SiC)(0.025) + Te-0.01. Prior to the SPS procedure of tape formation, the samples were submitted to a series of cold working processes typical for the powder-in-tube technique. The tapes were compared with optimal doped bulk samples (having the same starting composition) and a pristine MgB2 tape. The morphology of the composite samples, the phase structure of both the core and the inner face of the metallic sheath shows the formation of a plethora of traces as a result of interaction between MgB2, additives, and the Fe sheath. Important critical parameters, like critical current density and the irreversibility field, show that there is a field and temperature range where the SiC and Te-added tapes display better critical parameters comparative to either pristine MgB2 tapes in the Fe sheath or SiC and Te doped MgB2 bulk samples.

Within this study a matrix assisted pulsed laser evaporation technique was employed for deposition of CdS quantum dots onto TiO2 nanotubes. The number of laser pulses and laser fluence were varied to control the amount of CdS deposit. TiO2 nanotubes were obtained via anodization technique of sputtered Ti film on FTO glass. For CdS synthesis, dimethyl sulfoxide (DMSO) was used as a matrix of the target which absorbs radiation of KrF* laser (lambda=248 nm), then evaporates enabling the deposition of CdS quantum dots dispersed into DMSO. This study showed that the size of the CdS nanoparticles synthetized in DMSO can be controlled with microwave treatment that causes the release of S2- ions from DMSO for creation of CdS nuclei and/or their further growth. The optimization of CdS synthesis is achieved by varying the duration of the microwave treatment and the microwave power. The obtained TiO2 photo anodes with different amounts of CdS were assembled with PbS cathodes and the polysulfide electrolyte was injected between. The influence of amount of CdS deposit and the microwave treatment of CdS on photovoltaic performance of the fabricated solar cells were analyzed under AM1.5. The results showed that microwave treatment produced a Cd(S)-DMSO complex onto CdS nanoparticles which led to a higher current density of the solar cells obtained using microwave treated CdS target. Also, the increase of CdS content by increasing the number of laser pulses provided the enhance of I-V characteristics of the solar cells. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Large scale ZnO nanowire arrays were grown directly on zinc foils using the thermal oxidation in air method. The X-ray diffraction and reflectance investigations confirm that the as-grown nanowires properties are typical for ZnO having a hexagonal wurtzite crystalline structure and band-gap values between 3.2 and 3.3 eV. The scanning electron microscopy images prove that the density and the dimensions (diameter and length) of the ZnO nanowires can be tuned by controlling the oxidation temperature. Wettability studies reveal in the case of Zn foils a hydrophilic behavior with high water droplet adhesion which is transformed into a superhydrophobic one with low water droplet adhesion after the foils' surfaces are covered with ZnO nanowires. Obtaining functional surfaces with such interesting wetting properties using a simple, inexpensive and highly reproducible thermal oxidation in air technique is very attractive for anticorrosion coatings and self-cleaning applications. (C) 2016 Elsevier B.V. All rights reserved.

The electrochemical deposition of ZnxTey thin films was studied in an ionic liquid consisted in choline chloride - ethylene glycol eutectic mixture (Ethaline). ZnCl2 and TeO2 precursors were dissolved in 5-24 millimolar concentrations and the temperature was maintained constant at 60 degrees C. Cyclic voltammograms on Pt from electrolytes with both Te4+ and Zn2+ ions displayed three cathodic processes as limiting currents or peaks: Te underpotential deposition, codeposition of ZnTe compound, and deposition of Zn-rich binary telluride. The corresponding anodic waves or peaks were also identified. The shape of Nyquist electrochemical impedance plots recorded on various applied polarization showed that the electrode first covers with a Te film, and then the more cathodic polarization produces a co-reduction of Te4+ with Zn2+ as ZnTe compound. The formation of Zn metal-rich ZnxTey film at excessive negative polarization is indicated by the lowest value of maximum phase angle in Bode plots. The Zn/Te ratio (apparent stoichiometry) in the films deposited on Cu substrate is controlled by carrying out constant potential electrolyses with different ionic ratios in Ethaline bath. Film morphology, elemental analysis, and crystalline structure were evidenced by SEM microscopy, EDX analysis and X-ray diffraction, respectively.

This study investigated the mechanism of iron monosulfide (FeS) oxidation by dissolved oxygen (O-2(aq)). Synthetic FeS was reacted with O-2(aq) for 6 days and at 25 degrees C. We have characterized the initial and reacted FeS surface using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). It was found that during the aqueous oxidation of FeS new solid phases (disulfide, polysulfide, elemental sulfur, ferric oxyhydroxides and Fe3O4) develop on the mineral surface. The results of potentiodynamic polarization experiments show that after 2 days of FeS electrode immersion in oxygen bearing solution (OBS) at initial pH 5.1 and 25 degrees C the modulus of cathodic Tafel slopes dramatically decreases, from 393 mV/dec to 86 mV/dec. This decrease is ascribed to the change of the mechanism of electron transfer from cathodic sites to O-2 (mechanism of cathodic process). The oxidation current densities (j(ox)) indicate that mineral oxidative dissolution is not inhibited by pH increase up to 6.7. Another conclusion, which emerges from the analysis of j(ox), is that the dissolved Fe3+ does not intermediate the aqueous oxidation of FeS. The results of electrochemical impedance spectroscopy (EIS) show that after 2 days of contact between electrode and OBS the properties of FeS/water interface change. From the analysis of the EIS, FTIR spectroscopy, Raman spectroscopy and SEM/EDX data we can conclude that the change of FeS/water interface properties accompanies the formation of new solid phases on the mineral surface. The new characteristics of the surface layer and FeS/water interface do not cause the inhibition of mineral oxidation. (C) 2016 Elsevier Inc. All rights reserved.

In melt-spun FePtB-based ribbons, the addition of Ag has been proven to decrease the temperature of phase transformation from the A1 fcc FePt phase to the hard magnetic tetragonal L1(0) phase. Alloys with 6 and 9 at.% Ag added to the initial FePtB have been synthesized by rapid solidification from the melt. The samples have been laser irradiated and submitted to nitriding procedure. This procedure has been proven beneficial for inducing complete transformation of A1 to L1(0) phase and a strong (001) texturing. Ag segregation combined to mechanisms of creation of vacancies and diffusion of N give rise to the formation of an intergranular disordered region and due to an improved interfacial coupling between FePt grains, enhanced coercivity and two-phase magnetic behavior is obtained.