Vol 55, No 6 (2019)

For the case of nonanalytical chromatography, elution curves have been simulated for the adsorbent layers different in relative lengths. By adjusting integration interval, the calculation errors are obtained for the center of gravity of an elution curve depending on the value of this interval, normalized with respect to its ratio to the time of the elution curve maximum. The obtained dependences make it possible to control the minimization of the integration interval and thereby to exclude from the calculated values the parts of the experimental curve that lead to additional errors in the calculation of moments owing to the drift and fluctuations of the baseline signal.

A method for introducing small amounts of betulin (up to 1 wt %) into a mesoporous carbon material with a preset specific surface area of 300–310 m²/g, total specific pore volume of 0.35–0.40 cm³/g, and average pore diameter of 5.2–5.5 nm has been proposed and studied. The betulin content in the solid carbon matrix and in the used organic solvents has been determined by means of a gas chromatography–mass spectrometry technique. By means of scanning electron microscopy together with X-ray microanalysis and IR Fourier spectroscopy, the state of betulin on the outer and inner surfaces of carbon granules of different fractional composition, as well as in thin carbon layers, has been studied. It has been found that the main fraction of betulin is predominantly deposited on the outer surface of the globular particles of a porous carbon material. The properties of betulin impregnated into a carbon sorbent and the process of its dynamic desorption under the conditions simulating the biological environment of the gastrointestinal tract are studied.

With the aim of creating new adsorbing materials with biospecific properties for applications in medicine (obstetrics and gynecology), a technique for the chemical modification of a molded carbon sorbent with lactic acid by polycondensation of the latter on the surface of the former without catalysts is proposed. The completeness of the process of polycondensation of lactic acid on a molded carbon sorbent was controlled by physicochemical methods (low-temperature nitrogen absorption and thermal analysis). The amount of the deposited modifier (lactic acid oligomer) is a determining factor of the completeness of the modification process, which is determined from the results of thermogravimetric analysis of samples. The optimal conditions of the impregnation and thermal processing of a molded carbon sorbent, under which the amount of the deposited modifier reaches the maximum value and equals 7.2–10.5 wt %, have been chosen on the basis of the results of studies. The elemental composition and the content of surface functional groups of the two most promising samples of modified molded carbon sorbents are analyzed. These modified samples are of interest for further analyses and a study of their adsorption properties.

An exponential equation of diffusion kinetics for the adsorption, extraction, and drying of plant products with parameter γ, which considers particle interactions in the capillary-porous anisotropic structure of the solid phase, is suggested. Algorithms for calculation are considered and the molecular diffusion coefficients of elm extraction and drying birch sawdust assuming particle interaction in the system are compared.

In the present work, a method for producing new shaped composite materials by introducing a metal-organic framework structure Cu-BTC110 into a matrix of carbon material has been suggested. Powdered microporous activated carbons prepared from vegetable, polymer, and peat raw materials were used as carbon matrices. Physicochemical properties and structure-energy characteristics of the initial materials and shaped composites based on them were determined. It was demonstrated that the Cu-BTC110 composite with active carbon prepared from peat enabled one to achieve a balance between structure-energy characteristics, mechanical characteristics, and methane adsorption capacity. Depending on the temperature, the amount of accumulated methane can achieve 160–200 m³ (NTP)/m³ within a pressure range from 3.5 to 10.5 MPa.

Three-dimensional molecular dynamics (MD) simulation is conducted to understanding the dynamics processes of atomic-scale friction, which takes place in the columnar approach-separation model. A cylinder-cylinder sliding simulation model with tangential stress for Cu/Cu is built. Embedded atom potential (EAM) is employed for simulation. Based on the simulation result and the adhesion theory, the temperature change, friction force evolution and microstructures are systematically analyzed. The simulation results show that the temperature is related to the friction force, both increased during the transient sliding period. The friction force curve is analyzed by real contact area with tangential stress. Fluid mechanics is implanted to explain the decrease of friction force. An epitaxial bcc (body center cubic) copper layer is formed inducing adhesion during sliding. The rough peaks break causing the atoms leaving from interface.

Indium sulfide thin films were prepared by chemical bath deposition (CBD) method on a glass substrate at a sedimentation time of about 45 min. The films were grown at different bath temperature as 30, 55, 70 and 85°C. The crystallinity, nanostructures and morphology of the prepared films have been investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses. Optical reflectance of layers was measured in the energy range of 1.5–5.5 eV by spectrophotometer instrument. Kramers–Kronig relations were used to calculate the optical constants. The X-ray diffraction spectrum showed that by increasing in growth temperature, crystalline structure was changed. According to the atomic force microscope images, with increasing growth temperature, roughness increases consistently. Optical results revealed that the highest optical band gap of 3.4 eV and the highest transmittance of ~90% were achieved at higher deposition temperature (85°C).

In the interaction of tetra-15-crown-5-porphyrin (H2TCP) with rhodium(III) chloride in benzonitrile, the corresponding rhodium(III) porphyrinate (RhCl-TCP) containing a chloride ion as an axial anion in the Rh³⁺ cation coordination sphere was obtained and isolated. The structure of the obtained compound was determined based on the data of ¹H NMR spectroscopy, electronic absorption spectroscopy, and mass spectrometry. The luminescent characteristics of RhCl-TCP in a polymer matrix (polystyrene) were analyzed at temperatures of 298 and 77 K. It was found that the resulting complex can be considered as a luminescent sensor for temperature determination based on a change in the ratio of the phosphorescence and fluorescence intensities, as well as a change in the phosphorescence lifetime with temperature changing.

The paper presents mechanical properties of the porous Ti scaffold made with saccharose as a space holder. The Ti scaffolds had the porosity of 50, 60 and 70% and were made using 100 and 325 mesh Ti as a scaffold material. The pores were established using saccharose spherical space holder particles of 0.7–0.9 mm in diameter. The local mechanical properties of the Ti scaffold have been measured using nanoindenter. Several loading-unloading characteristics of the thin scaffold walls in the microscale have been measured. It has been observed that Ti scaffolds have very high mechanical properties measured in the microscale that are correlated with partial scaffold oxidation and a formation of TiO₂, which took place during the production stages. The scaffold is composed mainly of Ti oxide and the structure has been identified by XRD as well as XPS. The highest mechanical properties have scaffolds composed of 100 mesh Ti particles, compared to 325 mesh Ti. The microscale tests measurements are rather slightly affected by the pore presence and are under influence of Ti particles. The MTT test shows slightly higher proliferation of NHost cells on porous Ti scaffold in comparison to the reference Ti sample.

Cr–P–W protective coatings are obtained by electrodeposition from water–dimethylformamide solutions based on chromium(III) chloride, with the addition of sodium phosphinate and sodium tungstate. The resulting alloys contained up to 8 wt % of phosphorus and 1.5 wt % of tungsten, as well as some carbon. The resulting coatings are characterized by satisfactory corrosion resistance in corrosive environments containing chloride ions. The number of through pores in the coatings became negligible with a coating thickness more than 15 μm, providing sufficient protective ability of the developed coatings.

AISI 316 L austenitic stainless steel is widely used in various sectors of the industry (chemical, petro-chemical industry, paper industry, nuclear engineering, dairy equipment and medical field) because of its good corrosion resistance and biocompatibility. In contrast to these superior properties, it has a low hardness and poor wear performance, thus, limiting its use in some areas of industry. As a result of progress in science and technology, the expectation of superior properties from materials has increased and the surface modification has become an important part of this development. Amongst many coating processes, Electro-spark Deposition (ESD) is a micro-bonding process that is used to deposit a stronger, more robust and durable coating layer on a metallic substrate. This method can also be used to repair damaged parts, tools or equipment or to extend the tool and equipment life. In this study, the surface of AISI 316 L stainless steel was coated with WC and Ti6Al4V by ESD method. Morphology and microstructure of the deposited layers were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Surface hardness distributions were determined with a micro hardness tester. XRD analysis revealed that Fe–α, Fe–γ, W₂C, Cr–Ti, Al–Fe–Ti phases exist on the deposited layers. The wear behavior of the coated surfaces was carried out by ball-on-disc wear method using WC-Co ball bearing with a diameter of 8 mm for a sliding distance of 250 meters at a sliding rate of 0.3 m/s under a dry condition using a load of 5 N. Corrosion behavior of coated surfaces i.e. Tafel extrapolation and linear polarization methods were investigated for the duration of 1 h in the SBF (Simule Body Fluid) solution. Morphology of layers formed on steel surface was examined by SEM microscope. Wear tests showed that AISI 316 L stainless steel has a low surface hardness but wear resistant coatings improved this property. The wear rate of coated AISI 316 L stainless steel decreased by 3–10 times with respect to the type of coating. The electrochemical experiments showed that the expected improvement was not achieved due to the high corrosion resistance of AISI 316 L stainless steel. However, the weakness of the surface hardness was partly replaced by an acceptable compromise from corrosion resistance.

In this research, poly(methyl methacrylate-maleic anhydride)P(MMA-MAH)s with different percentages methyl methacrylate and maleic anhydride were synthesized and studied. Then the inhibitory potential of these copolymers on simple carbon steel in a 0.5 M HCl environment was investigated. Electrochemistry techniques have investigated the inhibitory potential of P(MMA-MAH)s in different concentrations at 25°C. Electrochemical investigations show that these copolymers with different percentages of mixed inhibitors has the inhibitory superiority of anodes over cathodes. Also, the adsorption of these polymers onto plain carbon steel follows the Langmuir adsorption isotherm. Field emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDX) were employed to confirm the results of the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of this study showed that P(MMA 30 mol %-MAH 70 mol %) had the highest corrosion resistance, followed by P(MMA 50 mol %-MAH 50 mol %) and P(MMA 70 mol %-MAH 30 mol %).

In this study, the inhibition effect of Tamarix Boveana (TB) extract on Cu corrosion in 1 mol L^–1 (HNO₃ + H₃PO₄) mixture was studied. Electrochemical techniques such as (potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM)) and non-electrochemical technique such as mass loss were used. Results showed that TB extract has good inhibition efficiency (IE), follows Langmuir adsorption isotherm and all of the methods are in good agreement. The IE increased by increasing the concentration of the extract and decreased by increasing the temperature so, the extract adsorbed on Cu surface physically. The IE depends on the concentration of the extract and reaches 73.5% at 300 ppm of the extract. PP results revealed that the (TB) extract doings as mixed type one. Surface analysis revealed that the extract components are adsorbed on Cu surface forming a film.

The aim of this study is first to investigate piperazine behavior as an inorganic corrosion inhibitor for a ST-14 steel and then to explore synergistical effect of organic (sodium silicate) and inorganic (piperazine) corrosion inhibitors. Due to different corrosion inhibition behavior of these two chemicals, positive results are expected. The corrosion inhibition characteristics of sodium silicate (Na₂SiO₃) and nitrogen contained organic compound, piperazine (C₄H₁₀N₂) as corrosion inhibitor for carbon steel was studied using weight loss, Tafel polarization, impedance and some spectrophotometric techniques. Also Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis) and scanning electron microscope (SEM) tests were conducted in order to indicate the formation of a protective film on the surface of steel coupons. The obtained results indicated that the combination of these two inhibitors improve the corrosion behavior about 87 and 76% in accordance with potentiodynamic polarization tests and electrochemical impedance spectrometry, respectively. The corrosion inhibition efficiency has been increased using an optimum combination including 2 ppm piperazine (PIP) and 10–15 ppm sodium silicate. It should be noted that the corrosion inhibition action has been employed using remarkably low concentration of corrosion inhibitors. From the interaction between corrosion inhibitors molecules and iron oxide layer, it can be concluded that the physical adsorption has more effect compared to chemical adsorption in the film formation process for both sodium silicate and PIP inhibitors. It is proposed at least two mechanisms for synergism.

Seven groups of the cast 304 stainless steels with boron addition as 0, 10, 20, 30, 40, 50, and 60 ppm were used to investigate their corrosion behavior by electrochemical potentiodynamic polarisation capacities in 10% HNO₃ solutions at laboratory environment. The effect of solution heat treatment at 800°C, 900°C and 1000°C for 1h on corrosive resistance of cast 304 stainless steel was also investigated. Microstructures and corrosion morphologies were examined by optical microscopy, X-ray diffraction analyses and scanning electron microscopy. Because of experiments, improvement of corrosion resistances depending on the amount of added B and heat treatment conditions were observed. Adding B to the cast 304 stainless steels improved its resistance to corrosion, but its resistance to intergranular corrosion reduced, which can be seen by the corrosion morphology. The improved corrosion resistance of cast 304 stainless steel was attributed not only to the added boron, but also solution-annealing treatment compared with non-borided cast 304 stainless steel.

Epoxy, Fusion bonded epoxy and conducting polyaniline based paints were applied on low carbon steel sample. Conducting polyaniline and conducting polyaniline based paint was characterized by UV-visible absorption spectroscopy and scanning electron microscopy respectively. Cathodic polarisation was used to determine cathodic protection potential range of the uncoated and painted low carbon steel samples dipped in 3.5% NaCl. Cathodic impressed current range was found out using galvanostatic technique and used to impart cathodic protection to non coated and painted samples. Iron loss of uncoated and painted samples without cathodic protection and under cathodic protection was measured using spectrophotometry. It was found that conducting polyaniline based paint exhibits negligible iron loss ~0.06 ppm in 3.5% NaCl solution under impressed current cathodic protection. Conducting polyaniline based paint can be used in association with impressed current technique to protect low carbon steel cathodically in neutral medium. However, conducting polyaniline, as a pigment, becomes less effective in presence of coating defects due to exposure of the metallic surface to the electrolyte.

The identification features of symmetric and nonsymmetric diaryl telluroxides via chromatography/mass spectrometry with electrospray ionization (HPLC/MS-ESI) are studied in the present work. Diaryl telluroxides exposed to ESI are shown to give rise to the formation of dimer ions and associate ions with the mobile phase components. Moreover, the influence of analyte concentration in the solution and the injection volume is found to impact the chromatography/mass spectrometry data.

A complex analysis of the crumbed rubber produced by the explosive circulation method has been performed by the methods of AFM, X-ray diffraction, gas chromatography, mass spectrometry, and gel-permeation chromatography (GPC). The results of the small- and wide-angle X-ray diffraction study have revealed an amorphous structure of the samples without supramolecular ordering at a distance scale of ~1–40 nm. Globular formations of a size of 5–20 nm on the crumb surface combined into clusters of various shapes and sizes in the range 100–1000 nm have been found by means of the AFM method. Individual nanoglobules and small and large clusters of these nanoglobules appeared to be randomly covering the surface of the examined samples. It has been established that the nanoglobules partially consist of saturated and unsaturated hydrocarbons of low-molecular weight, which belonging to classes of linear, cyclic, and aromatic compounds. Most of the nanoglobules are represented by oligomeric products having 3–5 units, as well as compounds of higher molecular weight. All of the above compounds provide better adhesion of the regenerate to different matrices than that produced by other methods. The composition of the nanoscaled globules includes secondary products of reactions of low-molecular hydrocarbons formed from rubber tires at their explosive circulation grinding.