Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases
The journal is focused on key investigations across a broad spectrum of condensed matter problems, physicochemical and electrochemical processes on interphase boundaries. The journal is issued 4 times a year.
Copyright (c) 2026 Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases http://creativecommons.org/licenses/by/4.0
Юбилей профессора Александра Викторовича Введенского
Клетки E.coli как источник биогибридного материала: исследование методами электронной микроскопии и микроанализа
Effect of Sr2+ ions on the gas-sensitive properties of LaCrO3 and GdCrO3
Objectives: Thin films obtained from La1–xSrxCrO3–δ and Gd1–xSrxCrO3–δ (x = 0.05, 0.10, and 0.15) synthesized by the modified citrate method were studied. Experimental: An analysis of the phase composition, structure, and gas-sensitive properties of films in the presence of carbon monoxide was carried out. Doping with Sr2+ ions led to an increase in the defect rate of nanoparticles due to the formation of vacancies in the oxygen sublattice. This phenomenon had a positive effect on their gas-sensitive properties. Conclusions: It was found that samples of La0.9Sr0.1CrO3–δ and Gd0.9Sr0.1CrO3–δ showed the highest sensory response at 180°C, 2.26 and 1.78, respectively. The results obtained confirmed the prospects of using these materials as gas sensors
Thermodynamic study of the BiSI-BiSeI system by the electromotive force method
Objectives: Chalcohalides of arsenic subgroup elements and solid solutions based on them are of great interest as functional materials exhibiting thermoelectric, photoelectric, piezoelectric, optical, and other properties. Experimental: This paper presents the results of a study of the thermodynamic properties of BiSI, BiSeI, and BiS1–xSexI solid solutions using electromotive force (EMF) analysis. For this study, concentration cells of the type (–) Bi (solid)/liquid electrolyte, Bi3+/(Bi in alloy) (solid) (+) were constructed and their EMFs were measured in the temperature range of 300-370 K. An ionic liquid, namely, morpholine formate, was used as the electrolyte. To select the compositions of the right-hand electrodes, solid-state equilibria in the BiSI-BiSeI-BiI3 system were studied using X-ray diffraction analysis. Continuous solid solutions of the BiSI-BiSeI boundary system were shown to form stable tie-line with BiI3. Using these data and literature information on boundary systems, a fragment of the solid-phase equilibria diagram for the Bi- S-Se-I system was constructed. Based on constructed diagram, the BiS1-xSexI solid solutions of various compositions with a 2–3 mol % excess of BiI3 and S1–xSex were selected as electrode-alloys for the aforementioned concentration cells. The partial molar functions of bismuth in the alloys were calculated from the obtained pairs of E(mV) and T(K) values. Conclusions: The constructed phase diagram made it possible to determine the virtual reactions of potential formation corresponding to the aforementioned partial molar functions and calculate the standard thermodynamic functions of formation and the standard entropies of bismuth thio- and selenoidide and BiS1-xSexI solid solutions. The calculations were performed using literature data on the corresponding standard integral thermodynamic functions of the BiI3 compound and S1–xSex alloys involved in potential-forming reactions. The thermodynamic functions of the BiSI and BiSeI compounds were compared with existing fragmentary literature data, and for solid solutions, they were determined for the first time
Microstructural and hydrophilic properties of acrylonitrile-butadiene-styrene copolymer ABS samples with different3D-printed patterns
Objectives: The aim of this study is to investigate the influence of different 3D printing patterns, under identical thermal and mechanical parameters of the 3D printing process itself, on the microstructural and hydrophilic properties of amorphous ABS copolymer samples printed with five different 3D printing patterns by sequentially depositing layers using FDM (Fused Deposition Modeling). Conclusions: The results of studying the printed samples using SEM, X-ray diffraction, IR spectroscopy, and contact angle measurements showed that the combination of thermal and mechanical effects during 3D printing in the studied extrusion mode does not cause noticeable orientation of the polymer chains of the original amorphous ABS copolymer, does not disrupt its intrastructural chemical bonds, and the surface of all printed samples with five different patterns is hydrophilic. Moreover, the printed sample with the most complex geometry is the 1_Hilbert pattern, which has the most distorted morphology and surface defects and exhibits the highest contact angle (j = 67o), exceeding the corresponding values in samples with other patterns (j ≈ 60o) by ~10 %, and has a hydrophilic surface
Acrylonitrile-butadiene-styrene copolymer ABS
Бессвинцовые интеллектуальные материалы на основе ниобатов щелочных металлов: фазообразование, кристаллическая структура, макроотклики
Электронное строение и пространственная структура химически осажденных высокофосфористых покрытий никеля для применения в передовых технологиях микроэлектроники
MOCVD and ferromagnetic resonance of epitaxial Lu3Fe5O12 films for high-frequency applications
Objectives: The production of thin films of rare earth iron garnets with a narrower ferrimagnetic resonance (FMR) linewidth is extremely important in the development of spintronic materials. Among rare earth iron garnets, the compound Lu3Fe5O12, which has the highest saturation magnetization, is promising. The aim of this work is to study the dependence of the FMR linewidth of Lu3Fe5O12 iron garnet films on the lattice mismatch between the film and the substrate, as well as on the film thickness during their production by metalorganic chemical vapor deposition (MOCVD). Experimental: Thin films of Lu3Fe5O12 garnet were obtained by MOCVD technique on isostructural single-crystal substrates of Nd3Ga5O12(111), Gd3Ga5O12(111), Gd3Ga5O12(210), Gd3(AlGa4)O12(111) and Y3Al5O12(111). The films were studied by XRD, EDX, and FMR methods. The dependences of the FMR linewidth on the mismatch of the unit cell (UC) parameters of the garnet at the film–substrate interface, substrate orientation, and film thickness were studied. Conclusions: It has been established that the minimum FMR linewidth (ΔН) of Lu3Fe5O12 films is achieved on substrates with minimal mismatch at the interface. The dependence of ΔН on film thickness is shown to be extreme, with the minimum corresponding to a film thickness at which significant relaxation of epitaxial stresses has occurred, but the concentration of defects characteristic of the polycrystalline state is still low. Taking these factors into account will make it possible to obtain iron garnet films with a narrower ferromagnetic resonance linewidth, which can subsequently be used in various areas of spintronics as sensitive elements in microwave detectors
Stability against crystallization and optical properties of (Ga10Ge15Te75)100-x(AgI)x ( x = 0–15 mol %) glasses
Objectives: Germanium telluride based glasses, due to theirwide transparency range and high refractive index, are promising optical materials for the middle infrared range. The tendency of such glasses to crystallize, which limits their practical application, requires the search for new compositions and the study of their properties. The aim of this work was to investigate the stability against crystallization and optical transparency of (Ga10Ge15Te75)100-x(AgI)x (x = 0–15 mol %) glasses as new materials for fiber optics. Experimental: The glasses were analyzed using differential scanning calorimetry, scanning electron microscopy combined with X-ray spectral microanalysis, and near- and mid-infrared spectroscopy. The main goal of the work is the establishment of high stability against crystallization of the studied glasses with a silver iodide content of 5–15 mol %. Conclusions: This makes it possible to consider such glasses as one of the most promising materials for the production of fibers with lowoptical losses in the spectral range of 4–15 μm
Features of equilibrium uranium sorption on the fibrous carboxylated sorbent FORPAN from carbonate-containingsolutions simulating seawater
Objectives: The purpose of this work is to study and identify the features of the equilibrium sorption of uranium from carbonate-containing solutions on a fibrous sorbent obtained (at the St. Petersburg Institute of Textile and Light Industry named after S. M. Kirov) by synthesizing carboxylated polyacrylonitrile (PAN) fiber with formaldehyde, with the common name of FORPAN. Experimental: The equilibrium sorption of uranium by the carboxylated fibrous sorbent FORPAN from carbonate-containing solutions simulating seawater was studied in the range of initial concentrations (3.36·10–5–7.13·10–4 mol/l) and temperatures (293–338 K) at pH = 7.85. It was found that during the contact of the fiber with the carbonate-containing uranium solution, a sharp decrease in the pH of the solution and the cleavage of the tricarbonate uranilate complex occur due to the protolysis of carboxyl groups. Based on mathematical processing (using the least squares method) of the dependences of the equilibrium distribution coefficients of uranium (ml/g) on the equilibrium concentration of uranium in solution (mol/ml) at different temperatures, a generalized equation was obtained that made it possible to calculate the capacity of the fiber for uranium (mol/g) during its sorption from model solutions prepared based on Caspian Sea water in the range of studied concentrations and temperatures, as well as to calculate the capacity of the FORPAN sorbent relative to uranium in Caspian Sea water (1.22·10–5 mol/g = 2.9·10–3 g/g) and the distribution coefficient of uranium in seawater (1.6·104 ml/g) at T = 293.3 K. Conclusions: Based on the conducted studies of the features of equilibrium sorption of uranium from model carbonate-containing solutions and the results obtained, FORPAN fiber can be recommended for the extraction uranium from dilute carbonate-containing solutions of natural waters, in particular from Caspian Sea water, with a uranium content of 2.5·10–6 mol/l, in the range of relatively low temperatures of 293–307 K
Semi-empirical description of the regularity of change in thermal conductivity of single crystals based on the exampleof a concentration series of Ba1–xLaxF2+x solid solutions
Purpose: To study the thermal conductivity of single crystals of a Ba1–xLaxF2+x solid solution and a semi-empirical description of changes in thermal conductivity depending on the lanthanum content. Experimental: In the temperature range of 50–300 K, the thermal conductivity of single crystal Ba1–xLaxF2+x samples with lanthanum content from x = 0.001 to x = 0.300 was determined by the experimental method of long heat flow. Conclusions: A monotonic concentration dependence of thermal conductivity has been revealed. A semi-empirical expression has been proposed to approximate the experimental values of thermal conductivity
Детектирование ацетона сенсором на основе клиноптилолита
Kinetics of cathodic deposition of copper from an acid sulfate solution in the presence of organic disulfides
Objectives: In this work, we established the kinetic patterns and evaluated the main parameters of heterogeneous nucleation and growth of a new phase during the electrocrystallization of copper during cathode deposition from an acid sulfate solution in the presence of organic disulfides (disodium salts of 3,3′-dithiodipropanedisulfonic acid, 4,4′-dithiodibenzene disulfonic acid and 3,3’-dithiodi(4-aminobenzene) sulfonic acids). The additives under study contain a disulfide group (-S-S-), which is characteristic of accelerators of the copper cathode deposition process in the implementation of electrochemical void-free filling of through holes (through silicon vias) of silicon wafers used in microelectronics in the manufacture of microcircuits. Experimental: Electrodeposition of copper coatings was carried out from aqueous sulfate solutions of copper plating in galvanostatic mode. Using scanning electron microscopy, it was found that in the presence of all the studied organic disulfides, copper crystallites with clearer edges are formed in the acid sulfate electrolyte of copper plating than in solutions without additives. The presence of aromatic groups in the structure of the accelerator molecule increases the size of the crystallites of the galvanic copper deposit, and the additional introduction of terminal amino groups into the disulfide structure, on the contrary, leads to a decrease in the size of the crystallites. The latter can be explained by the bifunctional nature of 3,3′-dithiodi(4-aminobenzene)sulfonic acid, capable of exhibiting both an accelerating and leveling effect due to the presence of a disulfide group and an amino group in the structure, respectively. The kinetics of cathodic deposition of copper coatings was studied using transient electrochemical methods of voltammetry, chronopotentiometry, and chronoammetry. In the presence of the studied additives, the overvoltage of copper electrodeposition decreases, while the kinetics of the process does not change: the charge transfer stage proceeds irreversibly, the activation of nucleation sites is progressive, and the growth of a new phase is controlled by the diffusion of copper ions from the solution to the cathode surface. Conclusions: The functionalization of aliphatic disulfide by the introduction of aromatic and amino groups does not lead to significant changes in the parameters of heterogeneous nucleation and the growth of a new phase during cathodic deposition of copper from an acid sulfate solution. However, the rate of electrocrystallization increases with the transition from aliphatic disulfide (disodium salt of3,3′-dithiodipropanedisulfonic acid) to disodium salt of 3,3’-dithiodi(4-aminobenzene)sulfonic acid, which contains both aromatic groups and amino groups in its structure
Silicon nanowires modified with Au/Ag nanoparticles for the label-free detection of prostate-specific antigen usingsurface-enhanced Raman spectroscopy
Objective: Prostate-specific antigen (PSA) is an important biomarker widely used for the early diagnosis of prostate cancer. In this work, substrates based on silicon nanowires coated with bimetallic gold and silver nanoparticles (AuAg@SiNWs) are presented for the highly sensitive detection of PSA using surface-enhanced Raman spectroscopy (SERS). Experimental: The fabrication of AuAg@SiNWs was based on simple and readily accessible chemical etching and metal deposition techniques, making the approach suitable for scaling and potential biomedical applications. The thickness of the silicon nanowire array was approximately 800 nm, while the bimetallic nanoparticle layer was formed predominantly in the upper region of the nanostructures and exhibited a thickness of 100–200 nm. To ensure the biospecificity of the sensor, the surfaces of the AuAg@SiNW substrates were functionalized with antibodies. Analysis of the SERS spectra revealed a clear dependence of the intensity of characteristic amide bands (in particular, at 1294 and 1030 cm–1) on the PSA concentration, starting from 1 ng/mL. The calculated calibration curve in the concentration range of 0.001–1 μg/mL demonstrated a high degree of linearity (R2 = 0.96), while the stable presence of characteristic spectral features at a concentration of 1 ng/ mL indicates the high functional sensitivity of the proposed platform. Conclusions: The results obtained demonstrate that AuAg@SiNW-based substrates possess significant potential for label-free and highly sensitive detection of protein cancer biomarkers, including PSA, and can be used as a platform for the development of compact biosensors for laboratory diagnostics and point-of-care applications
Electrochemical reduction of nitrate ions on copper coatings of various roughness under conditions of mixed transportand kinetic control
Objectives: In this work, the influence of electrode surface roughness on the kinetics of the non-stationary electrochemical process of cathodic reduction of nitrate ion under conditions of mixed transport-kinetic control under potentiostatic polarization conditions is established. Experimental: The research was carried out on two copper coatings obtained by galvanostatic deposition from a copper sulfate electrolyte, which was supplemented with various organic additives to vary the roughness of the synthesized copper coatings. The kinetics of the electrochemical reduction of nitrate ions on the obtained copper coatings were studied by transient electrochemical methods of voltammetry and chronoammetry in an aqueous deaerated solution of 10 mM KNO3 + 100 mM H2SO4. Potentiostatic measurements were performed at a cathodic potential of -470 mV, corresponding to a mixed transport-kinetic control. The surface roughness of the synthesized copper coatings was evaluated using atomic force microscopy and underpotential deposition of lead monolayer. Conclusion: Based on the previously developed theoretical model of the electrochemical process occurring in a mixed transport-kinetic mode on a rough electrode, an approach is proposed for estimating the main parameters of the kinetic stage, taking into account normalization to the real surface area, using the example of the electrichemical reduction of nitrate ions on copper coatings of various roughness. Within the framework of this approach, it was found that a rougher copper coating is characterized by higher values of the heterogeneous constant of the rate and density of the exchange current, which indicates an increase in the electrocatalytic activity of copper in the reaction under study during the transition to electrodes with increased roughness
On the formation of the Ag2Si metastable phase in an Ag-Si film obtained by ion-beam sputtering
Objectives: Nanocomposite films based on Ag-Si compounds have application in many areas of science and technology. However, their manufacturing process can be accompanied by the formation of silicides and metastable phases. In this connection, the task of developing methods for their identification arises. In this work, we attempted to solve this task using X-ray diffraction, ultra-soft X-ray emission spectroscopy, and theoretical calculations of the electron density of states for an Ag55Si45 film obtained by ion-beam sputtering of a composite target. Experimental: As a result of comprehensive studies, a nanogranular structure of the film was revealed, with an average silver particle size of ~15 nm, separated by a matrix based on phases of amorphous silicon a-Si, SiO2, and suboxide SiO1.3, as well as a silver silicide phase. A comparison of the experimental Si L2.3 X-ray emission spectrum of the Ag55Si45 film with theoretically calculated spectra of the AgSi3, Ag2Si, and Ag3Si phases shows the best agreement with the spectrum of the Ag2Si phase. Moreover, the Ag2Si phase was detected in the works of other authors. Conclusions: Thus, based on X-ray diffraction, X-ray emission spectroscopy, and theoretical calculations of the electronic density of states, it has been established that a metastable Ag2Si phase is formed in the Ag55Si45 film produced by ion-beam sputtering
Metastable Ag-Si-based phases, AgSi3, Ag2Si, Ag3Si
Ultra-soft X-ray emission spectroscopy (USXES)
Tunable magnetic, dielectric, and optical properties of cobalt ferrite/PVA nanocomposites: Effect of nanoparticle calcination temperature
Objectives: This study investigates the magnetic and dielectric properties of nanocomposites composed of cobalt ferrite (CoFe2O4) nanoparticles embedded in a polyvinyl alcohol (PVA) matrix. Experimental: CoFe2O4 nanoparticles were synthesized via a sol-gel auto-combustion method and subsequently calcined at 600 and 900 °C. X-ray diffraction results indicated that increasing the calcination temperature from 600 to 900 °C led to an increase in crystallite size from 23.3 nm to 48.5 nm. This was accompanied by an enhancement in saturation magnetization (Ms) from 68.7 emu/g to 81.3 emu/g and a decrease in coercivity (Hc) from 1150 to 860 Oe. Conclusions: Most importantly, the PVA/CoFe2O4 composites exhibited enhanced dielectric properties compared to pure PVA. At 100 Hz, the dielectric constant (ε′) of the composite increased from approximately 18 (for PVA/CF600) to 42 (for PVA/CF900), values significantly higher than that of pure PVA, which was approximately 9. This enhancement highlights a synergistic effect between the ferrite nanoparticles and the polymer matrix, opening possibilities for designing composites with tunable dielectric responses for applications such as embedded capacitors and electromagnetic wave absorption devices
Formation of oxide films on manganese silicide-germanides of various compositions during anodic polarization in an aqueous sodium sulfate solution
Objectives: Manganese silicide-germanides, with the general formula composition Mn5(Si,Ge)3, different in the quantitative ratio of silicon and germanium with the formula Mn5Si2.40Ge0.60, Mn5Si0.60Ge2.40, and Mn5Si0.15Ge2.85, were subjected to anodic polarization in an aqueous sodium sulfate solution. The main objective of the study was the determination of the products of their anodic transformation in a non-oxidizing neutral medium and the identification of regularities of the formation of oxide films on their surface. Experimental: The cyclic voltammetry method showed that the anodic oxidation process is not reversible. Polarization measurements were accompanied by subsequent monitoring of changes in the surface state using electron microscopy. The micro-X-ray spectral analysis was used for the determination of the ratio of elements on the surface before polarization of the sample and in the corrosion products. Conclusions: The results of the study demonstrated that during the anodic transformation process for all materials, the fraction of manganese in the samples decreased, the fraction of germanium increased, and the fraction of silicon changed insignificantly. It was concluded that the dissolution of the material components occurs selectively: manganese was predominantly ionized from the solid phase of manganese germanide into the solution, and its content on the surface was reduced to insignificant amounts. Silicon and germanium formed loose oxide layers without good adhesion to a hard, manganese-depleted surface and did not provide a serious protective effect. Germanium (II) oxide and partially hydrated germanium (IV) oxide GeO2 x H2O were the main products of anodic oxidation that remained on the surface. Silicon oxide was also present in anodic oxidation products, but in lower quantities, and was not sufficient for the provision of the protective effect of the material.
Copyright (c) 2025 Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases
Azeotropism of clathrate hydrates: a brief overview
Objectives: The objective of this work was to provide a review of the specific features of azeotropism manifestation in hydrate-forming mixtures. The physical basis of azeotropic behavior in clathrate hydrates and its relation to molecular structures and intermolecular forces are analyzed. The influence of hydrate system stability on azeotropic properties is considered, along with the effects of individual component characteristics such as molecular size and structure on azeotropy. Experimental: Experimental methods for identifying azeotropy in clathrate hydrates are reviewed. Computational approaches to determining the azeotropic point are analyzed, and theoretical predictions are compared with experimental data for known azeotropic hydrates. A concise overview of hydrate-forming mixtures exhibiting azeotropic behavior is also presented. Conclusions: Possible applications of azeotropic behavior in hydrate systems are discussed, highlighting its significant potential in practical and industrial contexts.
Phase equilibria in the GeTe-Sb2Te3-Te system
Objectives: Germanium-antimony tellurides are of considerable practical interest as thermoelectrics with low thermal conductivity, topological insulators and phase memory materials. In this paper, the results of a study of phase equilibria in the region of GeTe-Sb2Te3-Te compositions of the Ge-Sb-Te system using the DTA, X-ray diffraction and SEM methods are we presents. Experimental: The studied samples were synthesized using a special technique that allows them to be obtained in a state as close to equilibrium as possible. Conclusions: A diagram of solid-phase equilibria at 300 K, a projection of the liquidus surface and some polythermal sections of the phase diagram are constructed. The fields of primary crystallization of phases are outlined, non- and monovariant equilibria are determined. According to the obtained picture of phase equilibria, the curves of monovariant equilibria originating from the peritectic and eutectic points of the boundary system GeTe-Sb2Te3 undergo transformations at certain transition points. In the region of compositions rich in tellurium, a number of invariant transition reactions occur, corresponding to the joint crystallization of two-phase mixtures of telluride phases and elemental tellurium.
Simulation of a non-stationary electrochemical process on rough electrodes under mixed kinetic-diffusion control
Objectives: In this work, the effect of electrode surface roughness on the rate of a transient electrochemical process under mixed transport-kinetic control is established. A mathematical model of the electrochemical process occurring on an electrode with a rough surface and characterized by a different ratio of the rate constant of the charge transfer stage and the coefficient of non-stationary bulk diffusion is constructed. Experimental: Using the numerical method of finite element modeling, chronoamperograms of a transient electrochemical process were obtained under conditions of mixed transport and kinetic control on electrodes with different surface profiles defined by harmonic and fractal functions. The transient “roughness function - time” curves are calculated and the boundaries of the transition region are determined, within which it varies from the roughness factor to unity. It is found that the shape of the chronoamperogram depends in a complex way both on the geometric characteristics of the rough surface and on the ratio of the diffusion-kinetic parameters of the process. With relatively short durations, the gross process rate is equal to the charge transfer rate at a given potential and is proportional to the roughness factor. With relatively long durations, the chronoamperogram transforms into a current decay curve of the diffusion-controlled process, while the effect of roughness is nonlinear in this case and manifests itself only with relatively short process durations. Under these conditions, the thickness of the diffusion layer is much smaller than the size of the irregularities, and the rate of the process on the rough electrode is proportional to the true surface area and roughness factor. Conclusions: The position of the transition region depends on the value of the rate constant of the charge transfer: in the case of a slow kinetic stage, the transition manifests itself over increasingly long periods and gradually widens, while depending on the geometric shape of the irregularity.
Congratulations to Professor A. G. Syrkov
Study of the influence of the microstructure of Pt/C materials on the electrochemical characteristics of PtCo/C electrocatalysts based on them
Objectives: The paper studies the effect of the uniformity of spatial distribution of Pt nanoparticles over the support surface in Pt/C materials on the microstructure and electrochemical behavior of PtCo/C catalysts obtained on their basis. PtCo/C catalysts are synthesized by the impregnation of Pt/C followed by heat treatment in an Ar/H₂ atmosphere. The use of a Pt/C material with a platinum mass fraction of about 20% and a uniform distribution of Pt nanoparticles over the surface of the carbon support makes it possible to obtain a PtCo/C catalyst, the activity of which in the oxygen reduction reaction at 0.90 V is 1215 A/g (Pt), which is 4.8 times higher than a similar figure for a commercial Pt/C catalyst. In this case, the use of a Pt/C material with an ununiform distribution of nanoparticles leads to the production of a PtCo/C catalyst with large particle size and low active surface area, which significantly worsens its activity in oxygen reduction reactions. The purpose of this article is to study the effect of the uniformity of the spatial distribution of Pt nanoparticles over the support surface in Pt/C materials on the microstructure and electrochemical behavior of the PtCo/C catalysts obtained from them. Experimental: PtCo/C catalysts were synthesized by impregnation with Pt/C followed by heat treatment in an Ar/H2 atmosphere. Conclusions: The use of a Pt/C material with a platinum content of approximately 20% and a uniform distribution of Pt nanoparticles over the carbon support surface allows the production of a PtCo/C catalyst with an oxygen reduction reaction (ORR) activity of 1215 A/g (Pt) at 0.90 V, which is 4.8 times higher than that of a commercial Pt/C catalyst. The use of a Pt/C material with a non-uniform distribution of nanoparticles results in a PtCo/C catalyst with a large particle size and a low active surface area, which significantly reduces its ORR activity
Biotemplate synthesis of In2O3-Pd for room temperature sensor of hydrogen
Objective: The solution to the urgent task of creating compact gas analyzers capable of long-term autonomous operation in hard-to-reach places is related to the development of sensors with reduced energy consumption. The aim of this work was to create a room temperature hydrogen sensor, as it is the sensor’s heating that contributes significantly to the energy consumption of the entire device. Experimental: To solve this problem, a new method for the synthesis of a nanomaterial based on In2O3 with a 3 % palladium additive was developed, which differs significantly from the common methods of sol-gel synthesis and hydrothermal synthesis. This was due to the fact that at low sensor temperatures, minimizing the effect of humidity is crucial. Performing the synthesis in an aqueous environment leads to the formation of a large number of hydroxyl groups on the surface, which attract water. In our work, the nanomaterial was prepared by sintering a cellulose fiber pre-impregnated with a solution of indium nitrate (+3) and tetraammine palladium nitrate (+2). According to X-ray phase analysis, the powder sintered at a temperature of 500 °C consists mainly of the triclinic phase of indium oxide (+3). According to scanning electron microscopy, the samples largely retained the reproducible characteristic macrostructure of the cellulose template. The electrophysical characteristics of the nanomaterial obtained at room temperature showed the possibility of determining hydrogen in the air. The detection limit is less than 10 ppm. Conclusions: The sensitivity of our hydrogen sensor at room temperature is higher than that of sensors described in other publications. The effect of humidity on sensor readings is minimized.
Phase composition and texture of palladium (II) oxide thin films on SiO2/Si
The objects of the study are nanostructures based on palladium (II) oxide of various elemental compositions and morphological organization. The aim of the work is to establish the influence of synthesis conditions on the phase composition and texture of thin films of palladium (II) oxide synthesized by oxidation in an oxygen atmosphere of initial ultrafine layers of metallic palladium of various thicknesses on SiO2/Si(100) substrates. Conclusions: It has been established that the oxidation of the initial ultrafine layers of metallic palladium with thicknesses of ~ 95, ~ 190, and ~ 290 nm in an oxygen atmosphere in the temperature range Tox = 873 - 1123 K leads to the formation of homogeneous polycrystalline films of palladium (II) oxide on SiO2/Si (100) substrates. It is shown that the surface layers of PdO/SiO2/Si (100) films have a pronounced texture (001), the degree of which increases with increasing oxidation temperature.
Composition, structure, and electrophysical properties of natural zeolite clinoptilolites subjected to mechanical activation with potassium hydrosulfate
Objectives: The mechanochemical modification of zeolites with the addition of acidic salts causes an increase in the defectiveness of their structure, a change in the dispersion of the powder, and the conductivity of tableted samples. The aim of the study was to obtain mineral samples with improved conductivity using a mechanochemical method from air-dry mixtures of clinoptilolite-stilbite, clinoptilolite rocks and, potassium hydrosulfate in different ratios. Experimental: The shape and size of particles, chemical and phase composition of powders, and their physical properties were studied using electron microscopy, energy-dispersive X-ray spectrometry, X-ray phase analysis, differential scanning calorimetry, infrared spectroscopy, sieve analysis, gravimetry, and air permeability. The electrical conductivity of the tableted samples was measured using a three-electrode circuit in the temperature range from 25 to 100 °C. Conclusions: The results of the study demonstrated that mechanical treatment of mixtures of zeolites with an acidic salt leads to the amorphization of stilbite and feldspar, polymorphic transformations of quartz into cristobalite and tridymite, and an increase in structural defects. The interaction of components occurs via the silanol groups of clinoptilolite and hydrosulfate groups through the formation of hydrogen bonds and with the involvement of water molecules. It was also established that the electrical conductivity of a mineral tablet sample based on clinoptilolite rock and potassium hydrosulfate in an equimass ratio, subjected to shock-shear action with a mechanical energy dose of 2.16 kJ/g, amounted to 4.26·10–4 S·m–1 at 100 °C. Electrical conductivity values of the same order were obtained earlier for the mechanochemical activation of natural zeolites with potassium hydrophosphates. Consequently, the hydrosulfate anion does not make a significant contribution to the conductivity of zeolite samples compared to the hydrophosphate anion.