Magnetoelectric coupling in multiferroic CFO/BCTSn core shell nanofibers elaborated by co-axial electrospinning method

Multiferroic CoFe2O4-Ba0.95Ca0.05Ti0.89Sn0.11O3 core-shell nanofibers (CFO@BCTSn NFs) were synthesized by a sol-gel co-axial electrospinning technique. The scanning electron microscope and transmission electron microscope were used to check nanofibers' core-shell structure/configuration. X-ray diffraction and a high-resolution transmission electron microscope were used to confirm the spinel structure of CFO and the perovskite structure of BCTSn. The magnetic character of the resultant CFO@BCTSn NFs was determined by SQUID magnetometry. The piezoelectricity was verified using piezo-response force microscopy, which revealed an entirely covered ferroelectric shell outline, in accordance with SEM and TEM observations. The magnetoelectric (ME) coefficient was measured as a function of the applied external DC magnetic field. The maximum ME coefficient obtained for the CFO@BCTSn NFs was 346 mV cm-1 Oe-1. The high magnetoelectric coupling suggests that CFO@BCTSn NFs could be a promising candidate for magnetic field sensor and magnetoelectric device applications

Dielectric properties of copolymers based on cyano monomers and methyl α-acetoxyacrylate

International audienceWith the aim of developing dielectric polymers containing CN groups with strong dipole moment, alternating and statistical copolymers of the cyano monomers vinylidene cyanide (VCN), acrylonitrile and methacrylonitrile with methyl α-acetoxyacrylate (MAA) were synthesized and characterized. The copolymer's composition and microstructure were analysed by NMR spectroscopy, SEC and elemental analysis. The reactivity ratios calculated from the Q-e Alfrey-Price parameters for these copolymers indicated the alternating and statistical structures confirmed by NMR analysis. The copolymers have glass transition temperatures Tg in the range 83-146 °C and are stable up to 230 °C. The thermal stability of the copolymers depends on the nature of the cyano monomers. Their molecular dynamics were investigated by dielectric relaxation spectroscopy. We revealed a weak relaxation β at sub-Tg temperature for poly(VCN-co-MAA) usually originating from molecular motions that are restricted to the scale of a few bond lengths. Strong α-relaxation processes occurred above Tg for these copolymers. This primary relaxation was associated with cooperative movements of the polar groups (CN) at the time of mobility of the principal chains. The activation energy of the α-relaxation process was also calculated. The values of the dielectric increment Δε for these copolymers were determined by Cole-Cole plots and indicated that the copolymers exhibit interesting dielectric properties compared with similar cyano materials. The polarity-permittivity relationship was also established

Tuning Charge Storage Properties of Supercapacitive Electrodes Evidenced by In Situ Gravimetric and Viscoelastic Explorations

International audienceRevealed by an integrated electrogravimetric and viscoelastic method, slightly electrochemically reduced graphene oxide (ERGO) presents an anion preference for charge storage and delivery, while with the progressive removal of oxygen functionalities on its basal planes, cations begin to predominate in charge compensation. This “anion-to-cation” evolution in neutral aqueous media can not only affect the electrochemical charge storage, but also play an important role in electrode’s viscoelasticity. It was demonstrated that oxygen functionalities could modify the interactions between graphene layers and even contribute to pseudocapacitances. However, the role of oxygen functionalities in species transfer and viscoelastic variations still remains poorly understood. Herein, a combined methodology of electrochemical quartz crystal microbalance (EQCM), ac-electrogravimetry and electroacoustic impedance measurements was proposed for characterizing the electrochemical and viscoelastic responses of graphene oxides with various degree of electrochemical reduction. With the removal of oxygen containing functional groups, ERGO electrode exhibits (i) a gradually enhanced specific capacitance (Cs) with increased flexibility (decreased storage moduli, G′); (ii) a dehydration process of cations (i.e., from Na+·2H2O to Na+·H2O); and (iii) a potential-dependent “stiffened-softened” behavior. These results open the door for a suitable design of GO-based materials for electrochemical energy storage and shed light on electronic devices where ion-selective behavior plays a key role

New route to monoorganotin oxides and alkoxides from trialkynylorganotins

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Radical Copolymerization of Acrylonitrile with 2,2,2-Trifluoroethyl Acrylate for Dielectric Materials: Structure and Characterization

International audienceRadical copolymerization based on acrylonitrile (AN) and 2,2,2-Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN-co-ATRIF) copolymers were characterized by 1H, 13C, and 19F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by 1H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 C from initial [AN]0/[ATRIF]0 molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer--polymer copolymerization curve, the Fineman-Ross and Kelen-T€udos laws enabled to assess the reactivity ratios (rAN5 r1 5 1.25 6 0.04 and rATRIF 5 r2 5 0.93 6 0.05 at 70 C) while the revised patterns scheme led to r12 5 rAN 5 1.03, and r21 5 rATRIF 5 0.78 at 70 C. In all cases, rAN x rATRIF product was close to unity, which indicates that poly(AN-co-ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN-ATRIF, AN-AN, and ATRIF-ATRIF dyads. The Q and e values for ATRIF were also assessed (Q2 5 0.62 and e2 5 0.93). The glass transition temperature values, Tg, of these copolymers increased from 17 to 61 C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN-co-ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer

Corrosion of iron and nickel based alloys in sulphuric acid: Challenges and prevention strategies

Sulphuric acid (H2SO4) is widely used in various industrial processes, including fertilizer production. However, its highly corrosive nature poses a significant challenge to the materials used for transport and storage, particularly metals and alloys. This review provides an overview of corrosion types in iron and nickel-based alloys, commonly employed for handling sulphuric acid. The paper discusses alloy selection based on their corrosion behavior in different H2SO4 concentrations, temperatures, and harsh conditions such as erosion-corrosion and presence of contaminants. Additionally, it highlights the use of inhibitors and polymeric coatings for corrosion protection. Finally, the paper outlines future research directions for corrosion protection of alloys in sulphuric acid environments

Gas-phase infrared spectra of three compounds of astrochemical interest: vinyl, allenyl, and propargyl isocyanides.

International audienceIsocyanides, isomers of the cyanides detected in the interstellar medium, are also possible components of this medium. The infrared spectra (5000-500 cm(-1) ) of gaseous vinyl isocyanide, allenyl isocyanide, and propargyl isocyanide have been recorded at 0.1 cm(-1) resolution. When prepared on a gram scale to produce a partial pressure of 10 mbar after evaporation in the cell, these three isocyanides, which have previously been reported to be kinetically unstable, do not display any sign of decomposition when recording the spectra. Geometry optimizations and harmonic and anharmonic vibrational frequencies were calculated using the LCCSD(T) method with the cc-pVTZ basis set. Anharmonic frequencies of fundamental, overtone, and combination transitions were calculated using a variational approach implemented in the P Anhar.v2.0 code, to assign the experimental data for each compound. These results improve our knowledge of these under-investigated compounds and pave the way for other physicochemical studies on functionalized isocyanides

General Routes to Functional Organotin Trichlorides and Trialkoxides Involving the Tricyclohexylstannyl Group

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Diversity of Halophyte Desert Vegetation of the Different Saline Habitats in the Valley of Oued Righ, Low Sahara Basin, Algeria

Abstract: The aim of the present study was to investigate the floristic composition and diversity of the different habitat types in the saline areas of the valley of Oued Righ, locating in the low Sahara basin of Algeria. Three distinct saline habitats were examined: saline soil habitats, subsaline soil habitats, and waterlogged habitats. A total of 67 stands along the study area were investigated using the quadrat method, and different vegetation parameters, such as cover, frequency, density, and Importance Value Index (IVI), were recorded. Differences of species diversity and richness between saline habitats were also compared. A total of 38 plant species belonging to 29 genera and 13 families were identified from the three studied habitats. Chenopodiaceae was the predominant family. The majority of the species were of Saharo-Arabian distribution. Chemaephytes had the highest contribution to the life forms spectra. Species composition in the different habitat types showed differences in species richness. Subsaline soil habitats were the most diverse, followed by saline soil habitats. Waterlogged habitats had the lowest diversity. The floristic composition and the dominant species of each habitat were presented. The potential role of the halophyte species was discussed. These findings may lead to a better understanding of the functions, requirements, and sensitivities of these ecosystems

An optimized sono-heterogeneous Fenton degradation of olive-oil mill wastewater organic matter by new magnetic glutarlaldehyde-crosslinked developed cellulose

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