Gel electrolytes for aluminum-air (Al-air) primary batteries were prepared based on hydroxyethyl cellulose (HEC) and acrylate monomers bearing differently charged functional groups (i.e., ...-COOCH2CH2N+(CH3)3Cl−, -COO- and -COOCH2CF3). The acrylate monomers were grafted from HEC backbone and crosslinked using methylenebisacrylamide (MBA) to obtain hydrogels with tuned mechanical (15–75 kPa), morphological (pore size 35–125 μm) properties and varied swelling degrees at alkaline electrolyte (900–2500%). Electrochemical measurements were performed on Al-air cells assembled from Al anode, gel electrolytes (in 1 M NaOH) and carbon-based air-cathodes containing silver fine particles (Ag-FPs). Hydrogels with quaternary ammonium salt (HEC-AEtMACl) showed very long discharge time (6.5 h) compared to 1.8 h with the fluorinated hydrogels (HEC-TFEMA) and 1.1 h with carboxylated hydrogels (HEC-AA). Also, HEC-AEtMACl showed the highest current peak (3.9 μA at 1.4 V). Polarization curves proved that the anodic polarization behavior is dominant resulting from the anodic parasitic reaction. The Electrochemical Impedance Spectroscopy (EIS) evidenced that HEC-TFEMA has ionic conductivity (34.4 mScm−1) higher than that of HEC-AEtMACl. However, the highest specific capacity was observed to HEC- AEtMACl 0.928 mA h/cm2 compared to 0.26 and 0.15 mA h/cm2 for HEC-TFEMA and HEC-AA respectively.
•Gel electrolytes based on hydroxyethyl cellulose were prepared for Al-air batteries.•Charged-functional groups on hydrogels impact the discharging time significantly.•Positively charged hydrogel prevents the passivation layer on Al-anode.•Fluorinated hydrogels showed the highest ionic conductivity.
Sorption of higher concentrations of Cu(II) solution onto natural sheep wool or wool irradiated by an electron beam was studied. Sorption isotherms were of unexpected character, showing extremes. The ...samples with lower absorbed doses adsorbed less than non-irradiated wool, while higher doses led to increased sorption varying with both concentration and dose. FTIR spectra taken from the fibre surface and bulk were different. It was concluded that there was formation of Cu(II)-complexes of carboxylic and cysteic acids with ligands coming from various keratin macromolecules. Clusters of chains crosslinked through the ligands on the surface limit diffusion of Cu(II) into the bulk of fibre, thus decreasing the sorption. After exhausting the available ligands on the surface the remaining Cu(II) cations diffuse into the keratin bulk. Here, depending on accessibility of suitable ligands, Cu(II) creates simple or complex salts giving rise to the sorption extremes. Suggestion of a mechanism for this phenomenon is presented.
The subject of the article is a physical-mechanical analysis of waterproofing materials exposed to an external environment. Physical and mechanical properties have a direct impact on the life of ...waterproofing materials and their later remediation. In the introduction, the factors influencing the properties of waterproofing materials are presented. The main part of the article covers the basic possibilities of testing the materials testing the materials, normative testing conditions, and critical aspects of their implementation. In this article we deal with the laboratory testing of a waterproofing membrane based on PVC-P in terms of its degradation from UV radiation, humidity, and the temperature.
A microstructural study of bisphenol-A diglycidyl ether (BADGE), prepared
via
both "classical" and novel photo- and thermally-induced cationic frontal polymerization, can help to understand the ...relationships between the microstructure of epoxides and their material properties, as well as the propagation of frontal polymerization waves. Microstructural PALS characteristics, such as the
ortho
-positronium lifetime (
τ
o
-Ps
), lifetime distribution, and void fraction, were investigated in relation to the extension of H bonds obtained from ATR/FTIR and the bulk density. The thermal profiles of differently-induced RICFP revealed that photo-triggered propagation is twice as fast as thermally-induced RICFP, with a comparable maximal reaction temperature (∼283 °C) and heat conductivity. Both RICFP-based samples, induced by UV light and heat, showed a lower
τ
o
-Ps
, narrower lifetime distributions, and a reduced void fraction, in comparison to the "classical" cured anhydride-based epoxy sample. These may be the main factors which result in better material properties. In addition, both their radial and angular profiles of free volume fraction confirmed experimentally the rotational movement of the propagating frontal waves and their influence on the microstructural inhomogeneities, and the final material properties.
Epoxides prepared by cationic frontal polymerization have a greater reduced void fraction than "classically" cured samples revealing free-volume consequences of waves.
We examined the characteristics of an electron beam irradiated wool with an absorbed dose of (21-410) kGy in comparison with natural wool with respect to the determination of the isoelectric point ...(IEP), zero charge point (ZCP), mechanism of Cr(III) sorption from higher concentrated solutions, and the modelling of the wool-Cr(III) interaction. The data of ZPC and IEP differed between natural and irradiated samples. Increasing the dose shifted the pH of ZPC from 6.85 for natural wool to 6.20 for the highest dosed wool, while the natural wool IEP moved very little, from pH = 3.35 to 3.40 for all of the irradiated samples. The sorption experiments were performed in a pH bath set at 3.40, and the determination of the residual Cr(III) in the bath was performed by VIS spectrometry under optimized conditions. The resulting sorptivity showed a monotonically rising trend with increasing Cr(III) concentration in the bath. Lower doses, unlike higher doses, showed better sorptivity than the natural wool. FTIR data indicated the formation of complex chromite salts of carboxylates and cysteinates. Crosslinks via ligands coming from different keratin chains were predicted, preferably on the surface of the fibers, but to a degree that did not yet inhibit the diffusion of Cr(III)-cations into the fiber volume. We also present a concept of a complex octahedral structure.
•Very thin nanostructured carbon films contained C, n and a small amount of o and h.•Film morphology differed depending on the deposition parameters and substrate type.•Thin carbon films contained ...amorphous, graphite and nanocrystalline diamond phases.•Films prepared at 800 °C showed best photo-induced electron emission properties.•Photocathodes on sapphire substrate exhibited better results than on quartz substrate.
Very thin N-doped nanostructured carbon films were deposited on quartz and sapphire substrate by radio-frequency reactive magnetron sputtering using carbon target and gas mixture of Ar and N2 or N2+H2 reactive gasses. Rutherford backscattering spectroscopy and Elastic recoil detection analytical methods determined the concentration of elements in the films. Scanning electron microscopy was used to investigate the surface morphology of nanostructured very thin carbon films. Raman spectroscopy was used for the determination of chemical structural properties of the thin nanostructured carbon films. Pulsed laser induced electron emission method was used for the study of photoelectron emission properties of nanostructured carbon films. Measured bunch charge results of fabricated transmission photocathodes showed better photoelectron emission properties of very thin nanostructured carbon films prepared on sapphire substrates. Effects of substrate and technology of very thin nanostructured carbon films on the properties of photo-induced electron emitters as backside illuminated transmission photocathode are discussed.
Abstract Antibiotic, soothing and healing properties of panthenol are exploited in various pharmaceutical and cosmetic products. Only D-panthenol is biologically active while its L-form might ...counteract the biological effectiveness of the D-enantiomer. Hydrating and moisturizing effects are exhibited by both enantiomers. Therefore, it is necessary to develop a rapid and cheap method for the determination of panthenol enantiomeric excess in pharmaceutical preparations. In this study, b -cyclodextrin was used as a chiral selector for the recognition of panthenol enantiomers. Inclusion complexes formed by b -cyclodextrin and the analyte showed small differences in NIR and UV/VIS spectra compared by chemometric assessment. Based on the figure of merit and model characteristics, PLS calibration model in the selected range of NIR spectra is preferred. UV/VIS spectrometry has the disadvantage of complicated sample preparation compared to NIR spectrometry. Results reached by both proposed methods were in good agreement. Statistical investigation of the results (by Student t -test and Fisher F -test) confirmed that the proposed methods are comparable and applicable to chiral analysis of panthenol pharmaceutical preparations.
The addition of heteroatoms to pristine carbon quantum dots (CQDs) change their structure and optical properties. In this study, fluorine (F)- and chlorine (Cl)-doped CQDs are prepared by the ...one-step green hydrothermal route from sodium fluoride, sodium chloride, urea, and citric acid as the starting precursors. Microscopy analysis reveals that the average size of these quantum dots is 5 ± 2 nm, whereas the chemical study shows the existence of C–F and C–Cl bonds. The produced F- and Cl-doped CQDs have fluorescence quantum yields of 0.151 and 0.284, respectively, at an excitation wavelength of 450 nm. Charge transfer resistance of F- and Cl-doped CQDs films is 2 orders of magnitude higher than in the pristine CQD films. Transport band gap of the doped CQDs is 2 eV bigger than that of pristine CQDs. Radical scavenging activity shows very good antioxidant activity of doped CQDs. Antibacterial testing reveals poor antibacterial activity against Staphylococcus aureus and Escherichia coli. The F- and Cl-doped CQDs are successfully used as fluorescent probes for cell imaging as shown by confocal microscopy.
The depletion of selected substituted phenol stabilizers from systems simulating self‐etching dental adhesives is studied. If the adhesive monomer is an acrylate derivative, the stabilizer disappears ...quickly. Experimental results support the hypothesis that the phenol stabilizers are depleted from the system via a non‐radical reaction with the acrylic double bond in addition to the free‐radical mechanism. The C‐conjugate addition of aryloxide anions to the acrylate double bonds (the Michael reaction) is proposed as the reaction mechanism. The rate of the acid‐catalyzed Michael addition between acrylate monomers and phenolic stabilizers depends on the strength of the acidic catalyst.
The shelf stability of multi‐component systems containing acrylic monomers stabilized with substituted phenols can be considerably reduced if components include acidic groups, as demonstrated on systems simulating one‐bottle self‐etching dental adhesives. The premature exhaustion is considered to be due to Michael addition of nucleophilic hydroxyarenes to acid‐activated acrylic double bonds.
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