This study presents the synthesis and characterization of Ni/Al2O3 catalysts prepared via one-pot solution combustion synthesis (SCS) using tartaric acid as a fuel. This is the first time tartaric acid has been used as a fuel to produce a nickel-based catalyst for the decomposition of methane (and C2-C4 associated petroleum gas (APG)). The research aimed to identify optimal synthesis parameters to maximize catalytic activity in the decomposition of methane and associated petroleum gas for the coproduction of hydrogen and carbon nanofibers (CNFs). An experimental design approach was employed to efficiently test the catalysts. Characterization techniques included scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and low-temperature nitrogen adsorption. The results demonstrated that catalysts prepared with a fuel-to-oxidizer ratio (phi) of 0.183, combined with a low synthesis temperature and heating rate (350 degrees C, 1 degrees C/min), exhibit exceptional activity, achieving a carbon yield of up to 49.3 g/gcat. (for 6 h time on stream). The catalysts obtained feature specific surface areas ranging from 60 to 176 m2/g, indicating a highly active and promising material for the efficient decomposition of methane toward turquoise hydrogen and CNFs. A comparison of the decomposition of methane and the mixture simulated associated petroleum gas was carried out, showing more than a twofold increase in the rate of carbon formation, reaching 12.6 g/(gcat.& sdot;h) for APG and 4.57 g/(gcat.& sdot;h) for CH4. It was found that the rapid formation of carbon during the decomposition of APG led to faster deactivation of the catalyst but allowed to obtina the carbon yields at the level of 60-75 g/gcat. for only 6 h (550 degrees C, 1 atm).

The kinetic isotope effect (k(H)/k(D), KIE) during replacement of H2O with D2O is a valuable tool for evaluating water activation in NaBH4 hydrolysis. However, its correlation with catalyst activity and stability remains unclear. In this study, two magnetically separable catalysts of different activity with a Co-0 core and a "Co-Al-O '' shell were synthesized via galvanic replacement. Compared to the non-catalytic process, water activation on the catalyst surface occurs more efficiently, resulting in reduced k(H)/k(D). The active Co-O-max catalyst contains a higher amount of oxidized phases (Co3O4, CoO, Co(OH)(2), Co-Al layered double hydroxide), which reduce to the active component in the reaction medium. Their deficiency in Co-O-min causes a sharp activity decline and a drastic increase in k(H)/k(D) (>5) upon reuse, indicating a shift toward the non-catalytic pathway. In contrast, highly active Co-O-max demonstrates an efficient catalytic water activation supported by a stable k(H)/k(D) of 2.34 +/- 0.05 over five cycles. The observed monotonic decrease in H-2 generation rate for this catalyst is probably attributable to the hydride activation step.

Multi-walled carbon nanotubes (MWCNTs) have been extensively utilized in gas-sensing applications due to their high surface area and excellent electrical conductivity. However, their hydrophilic nature makes them susceptible to humidity interference, as water molecule adsorption compromises gas detection accuracy. To address this limitation, a hybrid sensing material comprising carboxyl-functionalized MWCNTs (COOH-MWCNTs) and twodimensional tungsten disulfide (WS2) was developed to enhance humidity resistance. The gas-sensing performance of pristine MWCNTs, COOH-MWCNTs, and WS2/COOH-MWCNTs was systematically evaluated using machine learning (ML modeling, density functional theory (DFT), and molecular dynamics (MD) simulations to investigate their interaction mechanisms with NO2 molecules. The results revealed significantly stronger interactions between NO2 and the WS2/COOH-MWCNT structure, evidenced by more than a threefold increase in sensor response (Delta R/R). SHAP sensitivity analysis, based on random forest ML modeling, showed that the WS2 layer substantially reduced the impact of humidity-related features on sensor performance. DFT calculations further demonstrated that the NO2/WS2/COOH-MWCNT complex exhibited a lower energy gap (Eg = 3.12 eV) compared to NO2/MWCNT (4.02 eV) and NO2/COOH-MWCNT (3.58 eV), indicating a more stable interaction between NO2 and the hybrid surface. The integration of ML predictions with DFT and MD insights confirmed the superior NO2 sensing capability of WS2/COOH-MWCNTs.

Mesoporous MgAl2O4 + LnFe0.7Ni0.3O3 (Ln = La, Pr) nanocomposites were prepared by a cost-effective one-pot procedure with the Pluronic P123 copolymer and Ni + Ru active components were supported on them by wet impregnation. The real structure of samples was studied by X-ray diffraction and transmission electron microscopy with energy-dispersive X-ray spectroscopy, surface properties were determined by Fourier transform infrared spectroscopy of adsorbed CO, reactivity was evaluated by temperature programmed reduction by H2, and catalytic activity was tested in ethanol steam reforming (ESR). Disordering of the real structure of nanocomposite supports due to incorporation of transition metal cations into MgAl2O4 results in the development of a metal-support interface and domination of single surface metal centers. This provides a high catalytic activity in the ESR reaction in the intermediate temperature range similar to 550 degrees C, close to that of the best known catalysts, and stability to coking. A higher activity for the Pr-containing catalyst is provided by the high reactivity of surface oxygen species bound with Pr cations.

The beneficial impact of carbon coated alumina (C@Al2O3) implemented as support for the CoMoS hydrotreating catalyst has been demonstrated. A series of C@Al2O3 supports with varying carbon contents were obtained by pyrolysis of sorbitol preliminarily impregnated in alumina from an aqueous solution. It was found that carbon coating positively affects the formation of the high-active CoMoS phase. However, control of the carbon content from 2.3 to 11.3 wt % is essential to maintain the sulfide particles dispersion and textural properties. CoMoS/C@Al2O3 catalysts demonstrated superior hydrodesulfurization activity compared with CoMoS/Al2O3. The hydrodenitrogenation activity of most CoMoS/C@Al2O3 samples is similar to CoMoS/Al2O3 but decreases when the carbon content in the support exceeds 11.3 wt %. The determining factor in improving the CoMoS/C@Al2O3 hydrodesulfurization activity is the formation of defective graphene fragments, which partially cover the alumina surface and help to reduce the support acidity and, therefore, metal-support interaction while maintaining the textural characteristics.

In order to manage the environment and perform noninvasive disease diagnostics, it is necessary to continuously identify harmful and highly toxic gases, such as nitrogen dioxide (NO2). This study demonstrates how to design nanocomposites and build a cost-effective NO2 gas sensor based on exfoliated tungsten disulphide and functionalized multiwalled carbon nanotubes (f-MWCNTs) as a highly efficient sensing material operating at room temperature (RT) in humid conditions. The composite sensor's response under various humidity levels, ranging from 2% to 65%, as well as at different temperatures ( 25 C-degrees- 80( degrees)C), was studied. Scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX) were used to analyze the sensing material. The composite-based sensor showed an improved response Delta R/R0 of 52% at RT for 50-ppm NO2 with good selectivity to other gases (e.g., ammonia, methane, benzene, isobutene, and hydrogen). The composite sensor exhibited a low detection limit of 1.39 ppm for NO2 at RT. Furthering this advancement, we delve into the integration of machine learning, specifically the CatBoost regression model, with the NO(2 )sensor. This integration elevates the sensor from a conventional passive detector to an advanced analytical system, significantly boosting its predictive accuracy and adaptability for real-time environmental monitoring and nuanced data interpretation, thereby opening new frontiers in sensor technology and applications in environmental monitoring and health diagnostics.

The detection of toxic gases including NO2 has a great impact on the environment. To address sustainability issues in many sectors, including the energy sector, there is a demand for efficient technologies. Composites based on multi-walled carbon nanotubes (MWCNTs) and various polymers (polyaniline, poly(p-phenylenediamine, polyamide 6, and the mixtures of polyamide-6 with poly(p-phenylenediamine) were obtained. The samples were investigated using transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, etc. The MWCNT-polymer composites were used for creation of NO2 gas sensors operating at room temperature. It was found that the modification of MWCNTs with polymers makes it possible to enhance the sensor response to NO2 at room temperature by 5-6 times compared to the initial sample. The highest sensor response was achieved for MWCNTs treated with the mixture of polyamide 6 with poly(p-phenylenediamine) (2:1) reaching ΔR/R0 = –13.9% at 10 ppm. Additionally, the samples were tested as electrodes for supercapacitors (3.5M H2SO4 electrolyte) via cyclic voltammetry. The highest specific capacitance reached by the MWCNT-polymer composites was 141Fg-1 (at 2mVs-1) compared to 0.3Fg-1 for the untreated sample.

A synthesis procedure for composite precursors of the composition yttrium-stabilized zirconia nanoparticles – 2,2,6,6-tetramethyl-3,5-heptandionato-hafnium(IV) is developed. The thermal behavior of the synthesized composites is studied by the complex thermal analysis up to 600 °C in a wide concentration range. Main components of thermolysis products are determined by the energy-dispersive X-ray (EDX) analysis. Features are revealed in TG curves for all compositions in the temperature range of 310-410 °C. From the IR, XPS, and EDX data it is found that the observed effects are due to low-temperature decomposition of a small part of the volatile metal-organic precursor irreversibly absorbed on the surface of nanoparticles. A hypothesis is put forward that irreversible adsorption is caused by Lewis acid centers on the surface of nanoparticles. The obtained information about the thermal properties of composite precursorscan facilitate the development of methods to control nanoparticle concentrations in the coating formed.

Разработан метод синтеза композитных прекурсоров состава «наночастицы оксида циркония, стабилизированного иттрием - 2,2,6,6- тетраметил-3,5-гептандионато-гафний (IV)». Методом комплексного термического анализа изучено термическое поведение синтезированных композитов до 600 °С в широком концентрационном интервале. Продукты термолиза проанализированы на основные компоненты методом энергодисперсионного анализа. Для всех составов на кривых ТГ выявлены особенности в интервале температур 310-410 °С. На основании данных ИК-спектроскопии, РФЭС и ЭДС установлено, что наблюдаемые эффекты связаны с низкотемпературным разложением небольшой части летучего металлоорганического прекурсора необратимо адсорбировавшегося на поверхности наночастиц. Высказана гипотеза, что необратимая адсорбция связана с кислотными Льюисовскими центрами на поверхности наночастиц. Полученная информация о термических свойствах композитных прекурсоров позволит разработать методы управления концентрацией наночастиц в формируемом покрытии.

This paper is focused on the solution combustion synthesis (SCS) of a set of 90Ni/10Al2O3 2 O 3 (wt. %) catalysts for the production of hydrogen and carbon nanofibers through methane decomposition. A novel approach was employed to optimize the SCS of the catalysts in order to enhance the yields of hydrogen. The obtained catalysts were tested in methane decomposition at 550 degrees C and 1 bar. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, low temperature nitrogen adsorption, and X-ray diffraction were utilized to investigate the catalysts. The SCS process involved programmable heating of a mixture of Ni(NO3)2 & sdot;6H2O 3 ) 2 & sdot; 6H 2 O and Al(NO3)3 & sdot;9H2O 3 ) 3 & sdot; 9H 2 O with citric acid (C6H8O7) 6 H 8 O 7 ) from room temperature to 350-450 degrees C at a heating rates 1-10 degrees C/min and exposure durations of 0-20 min. It was discovered that a high specific yield of hydrogen (17.1 mol/gcat.) cat. ) and carbon nanofibers (171 g/gcat.) cat. ) can be achieved by synthesizing at 450 degrees C using a heating rate of 1 degrees C/min without additional exposure.

Single-phase Ce–Zr oxides with a fluorite structure were synthesized by the solvothermal method in an isopropanol medium. Synthesis was performed at the supercritical parameters of isopropanol. The effect of the synthesis parameters on the characteristics of the obtained materials (specific surface area, morphology, particle size, phase composition) was established. Ni (5 wt

The effect of gadolinium additives on the morphology, phase composition, and catalytic properties of MoVSbNbGdOx/SiO2 catalysts in the oxidative dehydrogenation of ethane to ethylene (ODE) is studied. It is shown that gadolinium concentration has a significant effect on the catalytic properties. At an optimum gadolinium content (Gd/Mo = 0.01–0.015), an increase in catalytic activity and ethylene selectivity is observed: at a temperature of 400°C, the ethylene yield achieves 72

An efficient strategy for synthesizing Ag/multi-walled carbon nanotubes-poly(methyl methacrylate) (Ag/ MWCNT-PMMA) composites has been proposed. The synthesis concept is based on the modification of oxidized MWCNT with Ag nanoparticles and subsequent distribution of the obtained Ag/MWCNT-Ox hybrids in a PMMA matrix. Herein, Ag/MWCNT-Ox hybrids with various size and content of Ag nanoparticles serve as a tool for tuning the electrical conductivity of the two series of Ag/MWCNT-PMMA composites with MWCNT-Ox content before (4 wt%) and after (10 wt%) the percolation threshold. Adding 0.2 wt% of Ag to the first composite series with nanotubes content of 4 wt% leads to a decrease in the percolation threshold in a three-component system. In the case of the second composite series, the introduction of Ag up to 1 wt% leads to a monotonic increase in the conductivity within one order of magnitude. Ag/MWCNT-PMMA demonstrates high shielding efficiency for incident radiation in the frequency range of 26-37 GHz, most of which is absorbed due to the conductive nature of the material. The improved electromagnetic properties of the Ag/MWCNT-PMMA composites are explained by the uniform distribution of fillers in the polymer, which ensures the formation of a 3D conducting network inside

Herein, carbon coated alumina (C@Al2O3) samples obtained by chemical vapor deposition of ethylene have been proposed as supports for CoMoS hydrodesulfurization (HDS) catalysts of full-range FCC naphtha. Various degree of support graphitization (from 30 to 74%) was achieved by changing the treatment time of alumina in ethylene from 15 to 120 min. The influence of the alumina graphitization on the state and morphology of the sulfide component and catalytic performance of CoMoS catalysts has been studied in detail. The dispersion of sulfide particles and the CoMoS phase content is found to increase with the growth of the graphitization degree. This is accompanied by an increase in the selectivity of the CoMoS/C@Al2O3 catalysts in the HDS of FCC naphtha, whereas the reverse trend is observed for the activity. Thus, by changing the support graphitization degree, the selectivity of CoMoS catalysts in FCC naphtha HDS can be tuned. An increase in the support graphitization degree to 74% made it possible to reduce the sulfur content in FCC naphtha from 238 to 10 ppm, with a total loss in octane number of less than 1.5 units, which demonstrates the great potential of CoMoS/C@Al2O3 catalysts for commercial application in selective HDS of FCC naphtha.

In this study, the mechanochemical synthesis of substituted hydroxyapatite (HA) containing zinc and silicon ions having a chemical formula of Ca10−xZnx(PO4)6−x(SiO4)x(OH)2−x, where x = 0.2, 0.6, 1.0, 1.5, and 2.0, was carried out. The synthesized materials were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and inductively coupled plasma spectroscopy. We found that HA co-substituted with zinc and silicate formed up to x = 1.0. At higher concentrations of the substituents, the formation of large amounts of an amorphous phase was observed. The cytotoxicity and biocompatibility of the co-substituted HA was studied in vitro on Hek293 and MG-63 cell lines. The HA co-substituted with zinc and silicate demonstrated high biocompatibility; the lowest cytotoxicity was observed at x = 0.2. For this composition, good proliferation of MG-63 osteoblast-like cells and an increased solubility compared with that of HA were detected. These properties allow us to recommend the synthesized material for medical applications, namely, for the restoration of bone tissue and manufacture of biodegradable implants.

Amorphous carbon (AC) is present in the bulk and on the surface of nanostructured carbon materials (NCMs) and exerts a significant effect on the physical, chemical and mechanical properties of NCMs. Thus, the determination of AC in NCMs is extremely important for controlling the properties of a wide range of materials. In this work, a comparative study of the effect of heat treatment on the structure and content of amorphous carbon in deposited AC film, nanodiamonds, carbon black and multiwalled carbon nanotube samples was carried out by TEM, XPS, XRD and Raman spectroscopy. It has been established that the use of the 7-peak model for fitting the Raman spectra makes it possible not only to isolate the contribution of the modes of amorphous carbon but also to improve the accuracy of fitting the fundamental G and D2 (D) modes and obtain a satisfactory convergence between XPS and Raman spectroscopy. The use of this model for fitting the Raman spectra of deposited AC film, ND, CB and MWCNT films demonstrated its validity and effectiveness for investigating the amorphous carbon in various carbon systems and its applicability in comparative studies of other NCMs.

The synthesis of a 90% Ni/Al2O3 catalyst via solution combustion synthesis with various fuels was studied in this work. Catalysts with a high content of the active component (i.e., nickel) were obtained as a result of the combustion of Ni(NO3)2·6H2O and Al(NO3)3·9H2O mixtures with fuel. The fuels, such as hexamethylenetetramine, glycine, urea, starch, citric acid, and oxalic acid, were investigated. The synthesis was carried out in a furnace, with the temperature being raised from room temperature to 450 °C at a rate of 1 °C per min. The paper evaluates the efficiency of fuels and their effect on the structure and properties of catalysts, as well as their catalytic activity. The catalyst was used for the synthesis of hydrogen and carbon nanofibers by methane decomposition at 1 bar and 550 °C. The catalysts were tested in a vertical flow reactor without preliminary reduction. The obtained samples of catalysts and carbon nanomaterials were studied by transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction. The highest activity of the catalyst was obtained when citric acid was used as a fuel. The specific yields of hydrogen and carbon nanofibers were 17.1 mol/gcat and 171.3 g/gcat, respectively. Catalytic decomposition of methane led to the formation of cup-stacked carbon nanofibers.

In this study, hydroxyapatite with the substitution of calcium cations by iron and phosphate by silicate groups was synthesized via a mechanochemical method. The as-prepared compounds have the general formula Ca10−xFex(PO4)6−x(SiO4)x(OH)2−xOx/2 with x = 0–1.5. The thermal stability of the as-prepared compounds was studied by ex situ annealing of powders in a furnace. It has been established that, at 800 °C for x ≤ 0.5, a partial decomposition of the substituted apatites occurs with the formation of the β–Ca3(PO4)2 phase. At high “x” values, the formation of this phase starts at the lower temperature of 700 °C, followed by the formation of Fe2O3 at 900 °C. The introduction of iron and silicate ions into the hydroxyapatite lattice was shown to decrease its thermal stability.

In this paper, room-temperature chemiresistive gas sensors for NO2 detection based on CVD-grown carbon nanofibers (CNFs) were investigated. Transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction were used to investigate the carbon nanomaterials. CNFs were synthesized in a wide range of pressure (1–5 bar) by COx-free decomposition of methane over the Ni/Al2O3 catalyst. It was found that the increase in pressure during the synthesis of CNFs induced the later deactivation of the catalyst, and the yield of CNFs decreased when increasing pressure. Sensing properties were determined in a dynamic flow-through installation at NO2 concentrations ranging from 1 to 400 ppm. Ammonia detection was tested for comparison in a range of 100–500 ppm. The obtained sensors based on CNFs synthesized at 1 bar showed high responses of 1.7%, 5.0%, and 10.0% to 1 ppm, 5 ppm, and 10 ppm NO2 at 25 ± 2 °C, respectively. It was shown that the obtained non-modified carbon nanomaterials can be used successfully used for room temperature detection of nitrogen dioxide. It was found that the increase in relative humidity (RH) of air induced growth of response, and this effect was facilitated after reaching RH ~35% for CNFs synthesized at elevated pressures.

Ex situ methods (TEM, XRD, and Raman spectroscopy) have been used to study the processes occurring at the multi-walled carbon nanotube/silicon interfaces (MWCNT/Si) during heat treatment of MWCNT-Si composites containing highly dispersed Si particles deposited on the surface of MWCNTs by CVD method. It has been established that during heat treatment, starting from 900 degrees C, the formation of SiC particles occurs. A further increase in temperature leads to the formation of polycrystalline SiC particles and a significant shortening of MWCNTs due to the reaction between Si particles and the surface of MWCNTs. It is shown that one can control the size of the formed SiC crystallites by varying the time and temperature of heat treatment. The kinetic dependences of the SiC formation process were studied within the Avrami-Erofeev model. The activation energy for the formation of SiC is estimated at 470 kJ/mol. The influence of heat treatment on the electrical conductivity and porosity of MWCNT-Si composites in the pressure range of 25-175 MPa has been studied.