This paper presents a structural model that provides an accurate description of gas permeability in polymer/2D-nanofiller nanocomposites. We observed a higher efficiency in reducing gas permeability for nanocomposites compared to microcomposites. This effect stems from strong interfacial interactions in nanocomposites, leading to a higher content of impermeable interfacial regions. We also estimated the maximum reduction in gas permeability at a fixed nanofiller content.
The paper presents the results of studies of structural transformations and the state of water in samples of MMK-045 nonworking, water-saturated, and working membranes using the methods of IR spectroscopy NTR and X-ray phase analysis. Three types of hydrogen bonds have been identified: (‒CO…H2O…CO–) (III) type ~30 kJ/mol, H2O…HN (II) type ~16 kJ/mol, and (I) type ~9 kJ/mol. Sorption water in a water-saturated sample, reducing the energy of intermolecular (NH…O=C) bonds, changes the configuration of PA6 macromolecules without changing the trans-conformers. At the same time, FTIR spectrum of the working membrane sample (absence of absorption band at 1478 cm–1) shows breaking of H‑bonds, accompanying changes in the configurations of molecules with increasing gauche conformers. Manifestation of a complex absorption band at ~1723 and 1737 cm–1, attributed to terminal carboxyl groups (COOH), indicates the destruction of PA6 macromolecules. Disappearance of the absorption band at ~3089 cm–1 for the first time experimentally confirms the connection between the Fermi resonance phenomenon in polymer molecules and the destruction of PA6 macromolecules to elementary structural units. X-ray studies indicate structural changes mainly at the supramolecular level in MMK-045 membrane samples. In a water-saturated sample, the density of molecules in the amorphous phase increases (2θ = 26.4°), and in the working one it decreases (2θ = 20.9°). The total crystallinity in the working membrane sample relative to the nonworking one decreased from 36 to 33%, not as a result of recrystallization, but rather as a result of a reduction in crystallites of α-phases, and increased in crystalline formations of γ-phases with imperfect crystalline structure.
Aluminum-intercalated materials were prepared from the native and sodium forms of bentonite clay and aluminum polyoxocomplexes using the method of intercalation and subsequent heat treatment at 500°C. The structure and physicochemical properties of the prepared materials were examined. It was found that the intercalated materials had a microporous structure characterized by a specific surface that was twice as large as that of the bentonite clay. The adsorption properties of the materials towards the anionic dye Acid Yellow 36 were studied. The sorption capacity of the intercalated materials increased by up to seven times compared to the initial clay. The physicochemical factors that affect the adsorption properties were identified. According to the IUPAC classification, the dye adsorption isotherm was categorized as type II. The kinetics of the dye adsorption are consistent with the pseudo-second-order kinetics model with a correlation coefficient of 0.9996. The process of dye adsorption onto the Al-intercalated materials is spontaneous and endothermic. The prepared sorbents can be used to remove anionic contaminants from water.
The PPY–CuO nanocomposite was synthesized by chemically oxidatively polymerizing pyrrole monomer. The FESEM, TEM and XRD examination revealed the structural properties of the CuO, PPY and PPY–CuO nanocomposites. Increased radiative charge carrier recombination was observed in the PPY–CuO nanocomposite. As resistivity dropped, the recombination in radiative form increased for the PPY–CuO nanocomposite. When compared to the original CuO, the PPY–CuO nanocomposite was shown to have an improved current density of 11.36 A/cm2. It was discovered that the PPY–CuO nanocomposite had higher rates of radiative recombination, improved conductivity and electron mobility, and higher luminescence in the visible spectrum, indicating that it could be used as an electron transport layer (ETL) material in organic light emitting diodes (OLEDs).
Micron boron carbide particle (B4Cp) and 2 vol % nano silicon carbide particle (SiCp) reinforced 2000 series aluminum matrix composites (AMCs) with different volume fractions of B4Cp (10, 15, and 20 vol %) were fabricated by powder metallurgy. In this study, the microstructure of B4Cp/SiCp reinforced 2000 series AMCs was analyzed using an optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Additionally, X-ray diffraction (XRD) analysis was adopted to identify inter-metallic phases that were formed during the heat treatment. The hardness, electrical conductivity, and compressive properties of AMCs were systematically investigated. The results indicate that the reinforcements of 10 and 15 vol % B4Cp are uniformly distributed, while the reinforcements of 20 vol % B4Cp present agglomeration in the Al matrix. The hardness of B4Cp/SiCp reinforced 2000 series AMCs decreased after increasing, in which the composite with 15 vol % B4Cp possessed the maximum hardness of 331.9 ± 16.6 HV. In addition, the electrical conductivity of composites decreased with the increase of B4Cp content. The aluminum matrix composites containing 15 vol % B4Cp achieved the maximum compressive strength and fracture strain values of 788 MPa and 6.23%, respectively.
The physicomechanical and physicochemical properties of film-forming styrene-alkyl(meth)acrylic latex copolymers were studied depending on the size of the latex particles and the hydrophobicity of their surface, which are a consequence of the features of emulsion polymerization. Using the method of dynamic mechanical relaxation spectroscopy, an increase in the intensity of relaxation mobility of latex polymer macrochains with a decrease in particle size and the hydrophobicity of their surface was established. This is accompanied by a decrease in the glass transition temperature of the polymer, corresponding to the maximum intensity of α-relaxation. A comparison of the properties of polymer films before and after their modification was carried out. water-soluble phthalocyaninate. When the polymer was modified, an increase was found in glass transition temperatures and the maximum intensity of α-relaxation as a result of disruptions in relaxation of the homogeneity of the polymer material when localizing the modifier on the surface of latex particles in the interparticle regions of the films. The localization of phthalocyaninate on the polymer surface is confirmed by fluorescence data spectroscopy, indicating the appearance of fluorescence in the modified polymer and its absence in the modifier itself.
Novel results about the practical adhesion of the layer/substrate system on borided and borocarburized AISI 8620 steels exposed to a quenching-tempering post-treatment were evaluated. The hardness (H) and Young modulus (E) were obtained by instrumented Vickers microindentation. Consequently, the residual stresses (σr) and elastic strain to failure (H/E) were estimated. The microstructural characterization of the entire experimental set was carried out by scanning electron microscopy (SEM). Finally, the practical adhesion of the experimental set was evaluated with a scratch test, using a progressive load from 1 to 150 N at 10 mm min–1, with a scratch length of 7 mm. The results indicated that the quenching-tempering treatment increased the practical adhesion of the layer/substrate system, due to the dissolution of the outer FeB phase on the boride layer. Furthermore, the borocarburized material showed an increase around 2 times of the critical load during the practical adhesion test, attributed to a greater depth of the compressive residual stresses along the boride layer and the carburized zone. The borocarburizing + quenching-tempering treatment provided a mechanical support to the AISI 8620 steel, reducing the brittleness of the layer, in comparison with the borided and borided plus quenching-tempering material.
This work studies corrosion behavior of the α-pinene (C10H16) and citric acid (1 × 10–3 M CA, H3C6H5O7·2H2O) compounds on commercial purity (cp-Ti) dental material investigated by electrochemical methods in artificial oral solutions (AOS, pH: 5.25, 37 ± 0.1°C) and density functional theory (DFT) study. The methods carried out by using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potential-current (Tafel) and linear polarization resistance (LPR) techniques in the AOS. In the previous study, α-pinene showed significant anti-corrosion capacity in CA medium by increasing the concentration of hydrogen ions. The aim of this research is to reveal the synergistic effect of the α-pinene and CA compounds on the material. Electrochemical results revealed that α-pinene played a role in the synergistic effect and acted as an excellent corrosion inhibitor. This effect shifted the pH of the solution from 5.20 to 5.60 on the basic side, also corrosion potential (Ecorr) shifted by 158 mV from –0.412 to –0.254 V towards the anode. Therefore, corrosion resistance (Rp) significantly increased from 50 to 254 kΩ cm2 (80%). Results indicated that TiO2 layer formation supported by α-pinene in this conditions. ICP-MS analysis also confirmed the formation of this layer. DFT study carried out by using different methods on the Gaussian 09W with 6-311G (d, p) basis set for α-pinene on cp-Ti. The studies showed that PBE method gave the higher maximum wavelength (λmax = 212.41 nm) than the other methods. The experimental results supported ICP-MS analysis by the DFT study.
In this study, two organic molecules namely, [4-(4-aminobenzoyl)-piperazin-1-yl)] furan-2-yl) methanone (4-4-ABPFM) and 4-(4-aminophenylpiperazin-1-yl) furan-2-yl) methanone (4-4-APPFM) were synthesized and characterized using FTIR, UV–visible, thin layer chromatography, C-13 and proton NMR. The corrosion inhibition efficiencies of these molecules were tested using weight loss, polarization and AC impedance methods. Quantum chemical calculations (which included local selectivity, global reactivity and Monte Carlo simulation) were also implemented to complement the experimental data. The results obtained provided information confirmed that the synthesized compound has some inherent corrosion inhibition potentials due to the presence of aromatic rings, pi-electron systems, heteroatoms and corrosion structure parameters. The maximum inhibition efficiencies were 95 and 91% for 4,4-ABPFM and 4,4-APPFM respectively. The ideal fitness of the Langmuir isotherm with slope and R2 values approximating unity was also upheld. Theoretical calculation results showed strong accord to experimental values and supported higher efficiency for 4,4-ABPFM than 4,4-APPFM. Monte Carlo simulation showed that the adsorption energy is negative and also supported evidence drawn from the experiment, which is the spontaneous adsorption of the inhibitors on the metal surface.
Composites of titanium dioxide and NaX zeolite containing 50, 70, and 80% TiO2 by weight relative to the zeolite in their composition are obtained using solutions with a high concentration of polyhydroxo complexes of titanium in a pressurized reactor. The materials are characterized by X-ray diffraction, IR spectroscopy, scanning electron microscopy, energy-dispersive microanalysis, and low-temperature adsorption–desorption of nitrogen. The adsorption and photocatalytic properties of the composites are studied by way of example of a model dye, Rhodamine B. The phase composition of the photoactive coating (the ratio of anatase and rutile); morphology of its surface; and textural, adsorption, and photocatalytic properties of the obtained composites to a significant extent depend on the degree of coverage of the surface of the zeolite. The properties of the microporous zeolite carrier after coating with titanium dioxide are transformed into the properties of a mesoporous material in the composite. The highest photocatalytic activity is found for the 80% TiO2/NaX composite (with a size of TiO2 crystallites of about 13 nm and an anatase/rutile ratio of phases of about 0.97). Complete discoloration of the dye (concentration of 10 mg/L, amount of the photocatalyst composite of 1 g/L) under UV irradiation (lamp power of 250 W) is observed over 90 min.
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