Engendering High Energy Density LiFePO4 Electrodes with Morphological and Compositional Tuning

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 Physicochemical Characterization of New "Green" Epoxy-Resin Hardener Made from PET Waste

"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 T_g 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.

Ionomers Based on Addition and Ring Opening Metathesis Polymerized 5-Phenyl-2-norbornene as a Membrane Material for Ionic Actuators

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, ¹H 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.

Hydrolysis data for bis(4-cyanophenyl) phenyl phosphate including rate constants and activation parameters

Hydrolysis data for Bis(4-cyanophenyl) phenyl phosphate (CPP), introduced as a reactive diluent for phthalonitrile monomers, under pH 4, 7 and 10 are presented. Conversion/time plots collected by HPLC analysis, typical chromatograms and NMR spectra of the substrate and the reaction products are given. Pseudo-first order rate constants are determined for CPP at 25, 50 and 80 °C. Activation parameters were calculated from Arrhenius equation.

Dynamic and Static Mechanical Properties of Crosslinked Polymer Matrices: Multiscale Simulations and Experiments

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.

[The use of a silver staining method in the diagnosis of the late skin lesions in ixodid tick-borne borreliosis in man]

The borreliosis etiology was verified in 60% cases of the morphea, 100% cases of the atrophoderma of Pasini-Pierini and 100% cases of anetoderma by means of IFA with Ip-21 antigen (B. afzelii) and silver staining after Levadity. Borreliae were located near the capillaries, muscular and areolar tissue fibers of the derm and near the granulated cells of epidermis.

Experimental and mathematical models for small aqueous closed ecosystems with spatially separated components

Experimental and theoretical models of closed "autotroph-heterotroph" (chlorella-yeast, chlorella-protozoa) ecosystems with spatially separated components have been created and studied. The chart of flows and interaction of components of gas-closed "chlorella-yeast" system have formed the basis describe mathematically the functioning of the given system, experimental results have been found to agree with computer solution of the problem in terms of quality. Investigation of the experimental model of the "producer-consumer" trophic chain demonstrated the role of protozoa in nitrogen turnover. "Production-decomposition" and "production-grazing-decomposition" cycle models has been theoretically analyzed and compared. The predator has been shown to be a more intensive mineralizer than the reducer component.