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This work deals with the effects of ultraviolet (UV) aging on polycarbonate (PC) properties. Thus, a PC was subjected to accelerated UV radiation with a wavelength range from 200 to 280 nm, at different times. Induced changes in the material were studied by UV–visible spectrophotometry, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. The material surface was analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). Microhardness and uniaxial tension tests were performed on the aged and no-aged materials. It appeared that the studied PC turns yellow with UV aging time, in agreement with UV–visible spectrophotometry results that highlighted a loss in transparency of the aged material. The microhardness measurements showed that PC samples were entirely affected by UV radiations. In addition, the material performances in uniaxial tension dropped with UV aging. The decrease in PC mechanical properties was related to the rupture of the most vulnerable bonds, revealed by FTIR analyses, and to superficial cracks showed by OM and SEM micrographics.

The elimination of rubber wastes without affecting the environment is one of the most important challenges of the 21st century waste management. Accordingly, the present work is focused on the recycling of natural rubber (NR) industry waste by means of devulcanization in supercritical carbon dioxide (scCO2) atmosphere. With that aim, a novel device allowing to perform rubber devulcanization was developed. It consists of a triaxial compression reactor integrated into a dynamic hydraulic universal testing machine with a heating chamber. NR industry waste was devulcanized in the mentioned device at different temperatures, in scCO2 by using diphenyl disulfide (DD) as devulcanizing reagent. The devulcanization degree and quality of the treated materials were evaluated by the swelling test combined with the Horikx theory. It was appeared that a successful devulcanization, with almost no degradation, was obtained, and the devulcanization degree reached maximum value of ~90%. Thermogravimetric tests and scanning electron microscopy (SEM) images strengthened these results. Finally, it was concluded that the developed device is appropriate to perform rubber recycling, which contributes to the progress in the environmental protection.

While it is known that strongly correlated transition metal oxides described by multi-band Hubbard model show microscopic multiscale phase separation little is known on the possibility to manipulate them with vacuum ultraviolet (VUV) 27 eV lighting. We have investigated the photo-induced effects of VUV illumination of a super-oxygenated La2NiO4+y single crystal by means of scanning photoelectron microscopy. VUV light exposure induces the increase of the density of states (DOS) in the binding energy range around Eb =1.4 eV below EF. The photo-induced states in this energy region have been predicted as due to clustering of oxygen interstitials by band structure calculations for large supercell of La2CuO4.125. We finally show that it possible to generate and manipulate oxygen rich domains by VUV illumination as it was reported for X-ray illumination of La2CuO4+y. This phenomenology is assigned to oxygen-interstitials ordering and clustering by photo-illumination forming segregated domains in the La2NiO4+y surface, Comment: 10 pages, 3 figures

Since the last decade, graphene nanoplatelets with their exceptional physical properties are used as fillers in thermoplastic blends. In this work, the influence of commercial graphene nanoplatelets on properties of a high density polyethylene, in solid and melt states, was investigated, in comparison with the one of organically modified montmorillonite fillers. The use of a compatibilizer, a maleic anhydride grafted polyethylene, led to a clay based nanocomposite, with some improved mechanical and rheological properties, but with disappointing mechanical properties at break. On the other hand, by reducing the viscosity during mixing, the added compatibilizer slightly lowered the degree of dispersion of high aspect ratio graphene particles, weakening the material. More interestingly, the nanocomposite constituted with both clay nanoplatelets and lamellar graphene particles exhibited better reinforcing characteristics, in melt and solid states. This result can be partially explained by the high viscosity of the clay based nanocomposite which helps in the separation of graphene particles during mixing.

The present study describes a novel strategy for preparing thin Silicon 2D and 3D electrodes for lithium ion batteries by a spin coating method. A homogeneous and stable suspension of Si nanoparticles (SiNPs) was prepared by dispersing the nanoparticles in 1-methyl-2-pyrrolidone (NMP) or in the room temperature ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI). This proposed methodology was successfully employed to prepare 2D and 3D with different aspect ratios electrodes. Both 2D and 3D materials were then used as anode materials. The 2D SiNPs anodes exhibit a high reversible capacity, which is close to 3500 mAh·g−1 at C/10. For a higher discharge rate, the capacity of the 2D anode is considerably improved by dispersing the nanoparticles in Pyr14TFSI instead of NMP solvent. In order to further improve the anode performances, graphene particles were added to the SiNPs suspension. The anodes prepared using this suspension method exhibit relatively low columbic efficiency during the first few cycles (less than 30%) and low reversible capacity (2800 mAh·g−1 at C/10). The 3D SiNPs (NMP) electrode shows a higher intensity during cyclic voltammograms and a better stability under galvanostatic cycling than the 2D SiNPs (NMP) electrode.

The preservation of heritage is an interdisciplinary challenge which needs the expertise of many scientific disciplines as well as chemistry, physic, historical, etc. In the French Centre-Val de Loire region, most castles were built with both Tuffeau and Richemont stones. In this paper, we analyze some stones samples using both the Nonlinear Time Reversal imaging technique that is able to extract ultrasonic signatures in the the complex weathered Tuffeau stone at 5 MHz, and terahertz/infrared signature (FTIR) of the same sample with the same aging properties. Research has been undertaken to determine the potential of Nonlinear Time Reversal non destructive techniques in symbiosis with classical FTIR and X-ray chemical analysis for revealing the aging and chemical composition of historic stones. Nonlinear Time Reversal techniques are non invasive and non destructive making them suitable for in situ analysis of old stones and old concrete, as it is already made for modern concrete. It is shown that the symbiosis of ultrasound-based multimodal imaging and terahertz methods can provide an important diagnostic tool for cultural heritage applications. Chemical analysis is also necessary, for example, to identify the nature of the weathering and the aging.

The preservation of patrimonial is an interdisciplinary challenge which needing the expertise of many scientific disciplines as well as chemistry, physic, historical, etc. In order to generalize the idea of protection, Non Destructive Testing (NDT) is necessary for cultural heritage protection. The Loire Valley in France has a diversified cultural heritage, including monuments where the mainly construction units is stone. Research has been undertaken to determine the potential of Nonlinear Time Reversal (TR) non destructive techniques in symbiosis with classical FTIR and X-ray chemical analysis for revealing the aging and chemical composition of historic stones. It is shown that the sensitivity of TR based nonlinear ultrasonic methods in symbiosis with high frequency FTIR methods reaches the level of sensitivity for future non-invasive ultrasonic methods applied to cultural heritage.

International audience; This work focuses on the effect of nanoclay mass fraction on the properties of polyamide 12 matrix. Relationships between mechanical, thermal, and structural properties of polyamide 12/Cloisite® 30B nanocomposites were studied. The material structure, previously described from XRD and TEM experiments, was more thoroughly characterized in the present work using SEM and FTIR techniques. The FTIR results clearly showed that clay galleries are intercalated by PA chains, which leads to a partially exfoliated nanostructure, confirming the TEM observations and the XRD analysis. However, a few micrometric aggregates are evidenced by SEM analysis, particularly at high clay fractions. TGA and DTA measurements showed that the thermal stability of PA12 matrix is slightly modified by the Cloisite\textregistered 30B content. Viscoelastic properties of the nanocomposites in solid-state were analyzed as functions of strain, frequency, and temperature. The extent of the linear response regime of the material is shown to be sensitive to the amount of clay: nonlinearities appear at lower strain values as the clay mass fraction increases. Both relative dynamical moduli also increase with increasing clay mass fraction, with frequency dependence for the viscous modulus and without frequency dependence for the elastic modulus. Finally, similarities have been pointed out between viscoelastic properties of the nanocomposites in solid and melt states. For example, the percolation threshold is highlighted at the same clay mass fraction, ∼2%, in both states. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41938.

International audience; Sol-gel route was used to synthesize scandium oxides nanopowders. Oxohydroxide nanoparticles were first prepared in solution using ScCl3 . xH(2)O as precursor. The influence of pH and reflux time on particle size and shape was studied. Sc2O3 nanoparticles were then obtained after water dialysis and ScOOH sol drying. Depending on pH, 40-1000 nm size ScOOH particles can be obtained. At a given pH, reflux time also influences the ScOOH particles size, which can vary from a few nanometers to 1 mu m. The ScOOH sol can be used to prepare very pure Sc2O3 nanopowders. Results indicate a strong relation between nanoparticle size and the transformation temperature of gamma-ScOOH to Sc2O3. A direct correlation between the Sc2O3 powder and the original ScOOH nanoparticle shapes has also been observed. From the TEM studies, it is likely that the crystallization from the phase ScOOH into Sc2O3 one is isomorphic. Spark plasma sintering test highlights a very good sinterability of the Sc2O3 powder. Nearly fully dense ceramics can be obtained at 1400 degrees C. Microstructure is very homogeneous with ultrafine grains, with size in the range of 25-225 nm. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

International audience; In this study, styrene butadiene rubber (SBR) was devulcanized using microwave irradiation. In particular, effectof ionic liquid (IL), pyrrolidinium hydrogen sulfate [Pyrr][HSO4], on the devulcanization performance was studied. It wasobserved that the evolution of the temperature reached by rubber powder exposed to microwave irradiation for differentenergy values was favored by the presence of ionic liquid [Pyrr][HSO4] significantly over the whole range of themicrowave energy values. Beyond the threshold point of 220 Wh/kg, the soluble fraction after devulcanization sharplyincreased with increasing devulcanization microwave energy. For the powder mixed with [Pyrr][HSO4], the increase wasmore significant. Furthermore, the crosslink density was observed to decrease slowly with the microwave energy up to220 Wh/kg, beyond which the crosslink density decreased significantly for the rubber impregnated with IL. For the rubberwith IL, significant and continuous increase in Tg with microwave energy values was observed in comparison with the SBRwhere no change in transition temperature was observed. Mechanical shearing of rubber gums in the two-roll mill favoredthe devulcanization process, which indicated that the combination of mechanical loading with microwave energy and IL isan efficient procedure allowing an optimal devulcanization of rubbers.

The interaction between an acoustic wave and a complex media has an increase interest for both nondestructive testing (NDT) applications and for biomedical ultrasound. Today, new optimized excitations are generated thanks to the analysis of symmetry properties of the system such as reciprocity, nonlinear time reversal (TR) and other pulse-inverted (PI) techniques. Generalized TR based NEWS (Nonlinear Elastic Wave Spectroscopy) methods and their associate symmetry skeleton will be taken as an example. Among these family of “pulse coded excitation,” solitonic coding constitutes a new scheme in the sense that solitary waves are the best candidates for pulse propagation in nonlinear and layered media, such as tooth or skin. As another application of mixing properties in a wide frequency range, new broadband techniques are needed in the domain of the preservation of cultural heritage. The analysis of the composition of the stones is one of the key parameters in the study of aging historic buildings. The use of TR-NEWS based analysis combined with a FTIR-based system has shown a specific property of the tuffeau limestone where damaged sample contains calcite. In both domains, aging properties of complex medium are extracted thanks to the use of enhanced nonlinear signal processing tools.