A novel polyaniline-modified CNT and graphene-based nanocomposite (2.32–7.34 nm) was prepared and characterized by spectroscopic methods. The specific surface area was 176 m2/g with 0.232 cm3/g as ...the specific pore volume. The nanocomposite was used to remove zinc and lead metal ions from water; showing a high removal capacity of 346 and 581 mg/g at pH 6.5. The data followed pseudo-second-order, intraparticle diffusion and Elovich models. Besides this, the experimental values obeyed Langmuir and Temkin isotherms. The results confirmed that the removal of lead and zinc ions occurred in a mixed mode, that is, diffusion absorption and ion exchange between the heterogeneous surface of the sorbent containing active adsorption centers and the solution containing metal ions. The enthalpy values were 149.9 and 158.6 J.mol−1K−1 for zinc and lead metal ions. The negative values of free energies were in the range of −4.97 to −26.3 kJ/mol. These values indicated an endothermic spontaneous removal of metal ions from water. The reported method is useful to remove the zinc and lead metal ions in any water body due to the high removal capacity of nanocomposite at natural pH of 6.5. Moreover, a low dose of 0.005 g per 30 mL made this method economical. Furthermore, a low contact time of 15 min made this method applicable to the removal of the reported metal ions from water in a short time. Briefly, the reported method is highly economical, nature-friendly and fast and can be used to remove the reported metal ions from any water resource.
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We studied the static and dynamic mechanical properties of crosslinked polymer matrices using multiscale simulations and experiments. We continued to develop the multiscale methodology for generating ...atomistic polymer networks, and applied it to the case of phthalonitrile resin. The mechanical properties of the resulting networks were analyzed using atomistic molecular dynamics (MD) and dissipative particle dynamics (DPD). The Young's and storage moduli increased with conversion, due both to the appearance of a network of covalent bonds, and to freezing of degrees of freedom and lowering of the glass transition temperature during crosslinking. The simulations' data showed good quantitative agreement with experimental dynamic mechanical analysis measurements at temperatures below the glass transition. The data obtained in MD and DPD simulations at elevated temperatures were conformable. This makes it possible to use the suggested approach for the prediction of mechanical properties of a broad range of polymer matrices, including ones with high structural heterogeneity.
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“Green” thermally stable hardener was synthesized from a PET waste. The rigid molecular linear structure of the new hardener suggests that it will provide the polymer matrix with the necessary ...physical and mechanical characteristics. It also allows the expectation that cured matrix based on this hardener can provide increased toughness. New hardener was used as a curing agent for three epoxy resins—tetraglycidyl methylenedianiline (TGDMA, 111–117 EEW), diglycidylether of bisphenol A (DGEBA, 170-192 EEW) and solid epoxy resin (SER)—with a medium molecular weight (860–930 EEW) based on DGEBA. The mixtures were found to have the highest Tg for the DGEBA resin, and high of that for TGDMA and SER. According to the DMA analysis for two cured matrices, the hardener proved to be no worse than the standard ones, and made it possible to obtain cured matrices with excellent mechanical properties, which allows us to hope for further application of new hardener cured epoxy matrices in appropriate composite materials at high temperatures.
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•New low melting stable siloxane-bridged phthalonitrile monomers are reported.•Obtained monomers possess Tg lower than any previously reported data.•Thermal and thermooxidative ...properties remained at the level for phthalonitriles.
New low-melting phthalonitrile monomers were obtained by introduction of different flexible siloxane bridges such as –O–SiPh2–O– and –O–SiPhMe–O–. In spite of the presence of the siloxane groups the considered monomers were separated as single compounds by column chromatography with good yields (up to 90%). The synthesized monomers possessed Tg=12–27°C which were by a decade lower than it had been reported for phthalonitrile monomers before and even lower than the lowest Tg=41°C detected for phtalonitrilic oligomers. The cured monomers demonstrated high thermal and thermooxidative stabilities at the same level as described earlier for that type of polymer matrices. Thus a significant decrease of the Tg of the suggested monomers dramatically expands the processing window for the whole class of phthalonitrile matrices for reinforced plastics.
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Two types of poly(5-phenyl-2-norbornene) were synthesized via ring opening metathesis and addition polymerization. The polymers sulfonation reaction under homogeneous conditions resulted in ionomer ...with high sulfonation degree up to 79% (IEC 3.36 meq/g). The prepared ionomer was characterized by DSC, GPC,
H NMR and FT-IR. Polymers for electromechanical applications soluble in common polar organic solvents were obtained by replacing proton of sulfonic group with imidazolium and 1-methylimidazlium. Membranes were prepared using the above-mentioned polymers and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), as well as mixtures with polyvinylidene fluoride (PVDF). Mechanical, morphological, and conductive properties of the membranes were examined by tensile testing, SEM, and impedance spectroscopy, respectively. Dry and air-stable actuators with electrodes based on SWCNT were fabricated via hot-pressing. Actuators with membranes based on methylimidazolium containing ionomers outperformed classical bucky gel actuator and demonstrated high strain (up to 1.14%) and generated stress (up to 1.21 MPa) under low voltage of 2 V.
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Based on the selected key indicators in the innovation sphere, an integral rating assessment of the level of innovative development (IRR) of the Arctic Zone of the Russian Federation for the period ...2015–2019 was carried out and their innovative profiles were constructed, allowing to identify the strengths and weaknesses of the innovative potential of the subjects. On the basis of comparative ratings, the sufficiency of using the number of indicators for calculations and analysis of the obtained research results is justified. The rating assessment showed the leading position of the Krasnoyarsk Territory, the outsiders of the ranking include the Chukotka and Nenets Autonomous Okrugs. The authors propose a method for determining the level of sustainability of the IRR, which is calculated according to the consolidated integral index of innovative development of the region. The proposed methodological approach is based on the use of the coefficient of variation, well-known in the field of probability theory and statistics, and can be used to assess the innovation sustainability not only of regions, but also for other sectors of the economy and social sphere with corresponding changes in the system of indicators reflecting their production and economic activities. On the basis of input and output parameters, a rating of the effectiveness of innovative activity of the regions is compiled and the possibility of predictive assessments of its level for the future is shown. It is noted that in addition to the regional authorities, the results of the study can be used by various economic and social actors to monitor and forecast innovative development, as well as to adjust the existing regulatory documents in the field of innovation policy.
Improving the energy density of Li-ion batteries is critical to meet the requirements of electric vehicles and energy storage systems. In this work, LiFePO4 active material was combined with ...single-walled carbon nanotubes as the conductive additive to develop high-energy-density cathodes for rechargeable Li-ion batteries. The effect of the morphology of the active material particles on the cathodes’ electrochemical characteristics was investigated. Although providing higher packing density of electrodes, spherical LiFePO4 microparticles had poorer contact with an aluminum current collector and showed lower rate capability than plate-shaped LiFePO4 nanoparticles. A carbon-coated current collector helped enhance the interfacial contact with spherical LiFePO4 particles and was instrumental in combining high electrode packing density (1.8 g cm−3) with excellent rate capability (100 mAh g−1 at 10C). The weight percentages of carbon nanotubes and polyvinylidene fluoride binder in the electrodes were optimized for electrical conductivity, rate capability, adhesion strength, and cyclic stability. The electrodes that were formulated with 0.25 wt.% of carbon nanotubes and 1.75 wt.% of the binder demonstrated the best overall performance. The optimized electrode composition was used to formulate thick free-standing electrodes with high energy and power densities, achieving the areal capacity of 5.9 mAh cm−2 at 1C rate.
The prospect of using nanostructured materials in sorption-desorption cycles is substantiated by their unique physical-chemical characteristics determining the performance properties of modern ...sorbents. Functional polymer compounds are increasingly being used as modifying additives to carbon matrices. The authors have developed a method for synthesizing an innovative nanocomposite based on 1,4-benzoquinone-modified graphene oxide. The product obtained is technically called "polyhydroquinone/graphene oxide" (PHQ/GO). Technological parameters of the nanocomposite production were comprehensively studied. Quantitative dependences of the effect of the ratio of the initial components participating in the synthesis on the degree of GO surface modification were revealed. It was established that the amount of the modifier grafted nonlinearly depends on the weight of the initial monomer. This is presumably due to concurrent occurrence of several chemical reactions during the 1,4-benzoquinone polymerization. The physical-chemical characteristics of the material synthesized were investigated implementing the following techniques: scanning electron microscopy/energy dispersive X-ray spectroscopy, Raman spectroscopy, and thermogravimetry. The results of studying the structural, physical-chemical and operational properties of the nanostructured composite developed suggest that this material can be used as an efficient universal sorbent for the purification of aqueous media from different contaminants.
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Carbon fiber reinforced phthalonitriles obtained by resin transfer molding have been reported for the first time. Special formulation based on silicon-and phosphorus-containing ...phthalonitrile monomers has been developed to yield a composite with retention of mechanical properties at 300 °C and remarkable flame-retardant properties (LOI > 80%).
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