High Oxygen Content Research Articles

Critical review on the formations and exposure of polycyclic aromatic hydrocarbons (PAHs) in the conventional hydrocarbon-based fuels: Prevention and control strategies

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the atmosphere and primarily originate from the incomplete burning of fossil fuels and biofuels. Exposure to PAHs leads to harmful effects on human health and the environment. Diesel engines are a major source of PAH production in the transportation sector. Various approaches have been employed to reduce PAH emissions from diesel engines, including the use of biodiesel, green gaseous fuels, exhaust gas recirculation, exhaust after-treatment, and genetically modifying biodiesel with nanoparticles. This review focuses on PAH emissions from different generations of fuels and examines the remedial control actions taken to mitigate PAH formation. The study underscores the necessity for effective regulation of emissions from diesel engines, especially in developing countries where the reliance on fossil fuels is significant. Biodiesel has shown promise in reducing PAHs and carcinogenic pollutants, with higher biodiesel concentrations resulting in lower PAH formation. Replacing diesel with biodiesel and optimizing engine operating conditions are feasible methods to reduce PAH levels in the atmosphere. The use of nanoparticles in fuel blends and higher oxygen content in combustion chambers are also considered potential strategies for pollutant reduction. Additionally, the utilization of hydrogen and ammonia as secondary fuels has been explored as promising alternatives to fossil fuels. The study highlights the importance of further research on the presence of residual PAHs in the atmosphere and the implementation of strategies to curtail vehicular emissions.

Oxygen-enriched pitch-derived hierarchically porous carbon toward boosted zinc-ion storage performance

The lack of cathode materials with satisfactory Zn2+ storage capability substantially hinders the realization of high-performance aqueous zinc-ion hybrid capacitors (ZHCs). Herein, we propose a facile KMnO4 template-assisted KOH activation strategy to prepare a novel oxygen-enriched hierarchically porous carbon (HPC-1-4). This strategy efficiently converts coal tar pitch (CTP) into a well-tuned carbon material with a large specific surface area of 3019 m2 g−1 and a high oxygen content of 9.20 at%, which is conducive to providing rich active sites, rapid charge transport, and appreciable pseudocapacitance for Zn-ion storage. Thus, the as-fabricated HPC-1-4-based aqueous ZHC exhibits prominent performance, including a high gravimetric capacity (206.7 mAh g−1 at 0.25 A g−1), a remarkable energy density (153.4 Wh kg−1 at 184.2 W kg−1), and an impressive power output (15240 W kg−1 at 63.5 Wh kg−1). In-depth ex-situ characterizations indicate that the excellent electrochemical properties of ZHCs are due to the synergistic effect of the Zn2+ adsorption mechanism and reversible chemisorption. In addition, the assembled quasi-solid-state device demonstrates excellent electrochemical stability of up to 100% capacity retention over 50000 cycles, accompanied with a desirable energy density of 115.6 Wh kg−1. The facile preparation method of converting CTP into carbonaceous functional materials has advanced the development of efficient and eco-friendly energy storage technologies.

Oxygen supplementation in anesthesia can block FLASH effect and anti-tumor immunity in conventional proton therapy

BackgroundRadiation-induced neurocognitive dysfunction is a major adverse effect of brain radiation therapy and has specific relevance in pediatric oncology, where serious cognitive deficits have been reported in survivors of pediatric brain tumors. Moreover, many pediatric patients receive proton therapy under general anesthesia or sedation to guarantee precise ballistics with a high oxygen content for safety. The present study addresses the relevant question of the potential effect of supplemental oxygen administered during anesthesia on normal tissue toxicity and investigates the anti-tumor immune response generated following conventional and FLASH proton therapy.MethodsRats (Fischer 344) were cranially irradiated with a single high dose of proton therapy (15 Gy or 25 Gy) using FLASH dose rate proton irradiation (257 ± 2 Gy/s) or conventional dose rate proton irradiation (4 ± 0.02 Gy/s), and the toxicities in the normal tissue were examined by histological, cytometric and behavioral analysis. Glioblastoma-bearing rats were irradiated in the same manner and tumor-infiltrating leukocytes were quantified by flow cytometry.ResultsOur findings indicate that supplemental oxygen has an adverse impact on both functional and anatomical evaluations of normal brain following conventional and FLASH proton therapy. In addition, oxygen supplementation in anesthesia is particularly detrimental for anti-tumor immune response by preventing a strong immune cell infiltration into tumoral tissues following conventional proton therapy.ConclusionsThese results demonstrate the need to further optimize anesthesia protocols used in radiotherapy with the goal of preserving normal tissues and achieving tumor control, specifically in combination with immunotherapy agents.

Combustion characteristics of oxymethylene dimethyl ether-diesel blends: An experimental investigation using a constant-volume combustion chamber

The combustion characteristics of oxymethylene dimethyl ether (OMEx) and its blends with diesel have been investigated using a multi-hole injector in a constant-volume combustion chamber. The results show OMEx addition can reduce the ignition delay, especially when blends of more than 50 vol% are used, at low chamber temperature. Two individual heat-release peaks are observed for OMEx during premixed combustion at 750 K, due to a pronounced low-temperature heat-release phase. The chamber temperature of 800 K can be regarded as a transition point for the behavior of burn duration as well as maximum ROHR peak, mostly caused by combustion regime transition from premixed- to diffusion combustion. It appears that there is an approximate linear relation between maximum ROHR peak and the time at which this peak occurs with injection pressure. The ignition delay of OMEx is almost insensitive to a decrease in ambient oxygen concentration. And the premixed ROHR profile, due to its high oxygen content, is very similar and only ignition delay and burn duration increase slightly. Additionally, comparisons of natural luminosity results for OMEx and diesel indicate that OMEx produces near-zero soot values. Luminosity is expected to be caused by chemiluminescence alone, which increases with injection pressure.

Upgrading of fast pyrolysis bio-oils to renewable hydrocarbons using slurry- and fixed bed hydroprocessing

Liquefaction of lignocellulosic biomass through fast pyrolysis, to yield fast pyrolysis bio-oil (FPBO), is a technique that has been extensively researched in the quest for finding alternatives to fossil feedstocks to produce fuels, chemicals, etc. Properties such as high oxygen content, acidity, and poor storage stability greatly limit the direct use of this bio-oil. Furthermore, high coking tendencies make upgrading of the FPBO by hydrodeoxygenation in fixed-bed bed hydrotreaters challenging due to plugging and catalyst deactivation. This study investigates a novel two-step hydroprocessing concept; a continuous slurry-based process using a dispersed NiMo-catalyst, followed by a fixed bed process using a supported NiMo-catalyst. The oil product from the slurry-process, having a reduced oxygen content (15 wt%) compared to the FPBO and a comparatively low coking tendency (TGA residue of 1.4 wt%), was successfully processed in the downstream fixed bed process for 58 h without any noticeable decrease in catalyst activity, or increase in pressure drop. The overall process resulted in a 29 wt% yield of deoxygenated oil product (0.5 wt% oxygen) from FPBO with an overall carbon recovery of 68%.

Recent progress on non-noble metal catalysts for the deoxydehydration of biomass-derived oxygenates

Abstract The utilization of renewable energy represents an effective way to address current issues associated with fossil fuels. Biomass is considered one type of renewable energy resources with abundant reserves on earth. However, the high oxygen contents and high degree of functionalization of biomass have hindered the direct exploitation of biomass for the production of fuels and chemicals. Considerable efforts have been devoted to developing effective deoxygenation methods capable of reducing the oxygen contents of biomass and its derivatives. The deoxydehydration (DODH) of biomass derivatives to generate olefins over oxophilic metal catalysts is considered a very useful approach in eliminating vicinal OH groups. In recent years, catalysts based on non-noble metals such as Mo, W, and V featuring good catalytic performance have emerged as promising alternatives to classical noble Re-based catalysts for DODH. This review aims to summarize the progress on the DODH of biomass-derived vicinal diols catalyzed by non-noble metals such as Mo, W, and V, with an emphasis on the preparation of catalysts, optimization of experimental conditions, and mechanistic studies. By surveying the performance of non-noble metal catalysts, key factors that determine the DODH activity were proposed, including the choice of reductant, the electronic and steric effects of ligand, and the interaction between solid support and metal center. The latter two could adjust the redox properties of metal centers by directly bonding with ligand or solid support.

Selective adsorption mechanism of CO2/CH4/N2 multi-component gas mixtures by N/S atoms and functional groups in coal

The modification of coal samples will effectively enhance their selective adsorption properties for different gases. To investigate this phenomenon, the adsorption mechanism of CO2/CH4/N2 binary gas mixture by single benzene ring layer doped system and microporous system formed by N/S atoms with different functional groups in coal was investigated at microscopic level, and electrostatic potential, diffusion characteristics, fluid type, radial distribution function (g(r)) and coordination number (CN) were analyzed. The results showed that the interaction of N/S atoms with oxygen-containing functional groups in coal enhanced the electrophilic capacity of the system and enhanced the adsorption capacity of CO2 in the gas mixture, and the Freundlich adsorption capacity of CO2 in the N-doped system was higher than that in the S-doped system. The interaction between N atoms and oxygen-containing functional groups in coal will effectively enhance the adsorption selectivity of CO2 in the gas mixture, with the best capture effect between 80% and 70% of CO2 concentration. The high-energy adsorption sites in N/S-modified coal samples are more inclined to be occupied by CO2, and the fatty functional groups are more likely to trap CH4 and N2. These findings indicate that N-doped modification of coal samples with high oxygen content can lead to solid adsorbents with high adsorption capacity and strong selectivity, which provides theoretical guidance for the development of new and efficient adsorbents.

Fabrication of coal-based oxygen-rich porous carbon nanosheets for high-performance supercapacitors

The modification and optimization of porous carbon electrodes is key to achieving high-performance supercapacitors. Oxygen-rich porous carbon nanosheets (OPCNs) with a two-dimensional (2D) structure produced from the solid by-products of the coal industry were prepared by taking advantage of the rigid confinement of 2D MgAl-layered double hydroxides (MgAl-LDH) combined with KOH activation. The influence of carbonization temperature on the microstructure and surface properties of the OPCNs was investigated. The surface morphologies/compositions and surface textures of the prepared OPCNs were observed and analyzed by SEM, TEM, N2 adsorption and desorption, elemental analysis, etc. The optimized carbon sample activated at 700 °C (OPCN-700) had a high oxygen content of 24.4 wt%, a large specific surface area of 2 388 m2 g−1, and good wettability. In addition, the abundant micropores and 2D nanosheet structure of OPCN-700 provide efficient storage and transport for electrolyte ions. Because of this, when used as the electrode for a supercapacitor it has a high specific capacitance of 382 F g−1 at 0.5 A g−1, an excellent rate performance and cycling stability.

Simple and efficient removal of azo dyes from water samples by dispersive solid-phase micro-extraction employing graphene oxide with high oxygen content

ABSTRACT A technique based on dispersive solid-phase micro-extraction (DSPµE), employing graphene oxide (GO) particle with a higher oxygen content synthesised by through a modification of the Hummers method was investigated. GO particle was characterised using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Dubinin-Radushkevich, and Freundlich models. DSPµE parameters such pH effect, adsorbent amount, and contact time were optimised in the dye removal process. The proposed method was applied for the removal of three azo dyes in tap water samples: sunset yellow (SY), allure red (AR), and tartrazine (TAR). The water samples were previously analysed using large volume sample stacking capillary electrophoresis (LVSS-CE). Maximum removal capacity was achieved under the optimal conditions of pH solution (pH = 6.0), GO amount (10.0 mg), and contact time (10 minutes) with percentages at 99.0%. The precision was measured in terms of recovery (% desorption) and relative standard deviation from 95.5 to 98.0%, RSD (<10.0%). Two positive water samples for SY and TAR were completely free of azo dyes after application of the proposed method, whereas AR was not detected in any of the ten samples.

Facile and green synthesis of biomass-derived N, O-doped hierarchical porous carbons for high-performance supercapacitor application

The development of superior electrode materials using biomass as sustainable carbon sources is of great significance in promoting the practical application of supercapacitors. Herein, we prepared a N, O co-doped hierarchical porous carbon (GPC-0.9 N) with an ultra-high specific surface area of 2808.65 m2 g−1 and abundant microporous, mesoporous and macroporous structures through the straightforward pre-carbonization method using garlic peels combined with KHCO3/melamine activation. Additionally, the relatively high nitrogen (3.81%) and oxygen content (4.79%) can enhance the wettability of the carbon materials and introduce additional pseudocapacitance. As a result, the electrode material achieved a high specific capacitance of 396.25 F g−1 at 1 A g−1 and outstanding rate capability of 283.13 F g−1 at 25 A g−1 in 6 M KOH electrolyte in a three-electrode system. Meanwhile, the symmetrical supercapacitor based on the GPC-0.9 N electrode material showed a high energy density of 9.07 Wh kg−1 at the power density of 309.2 W kg−1. Furthermore, it exhibited excellent cycling stability, with 92.5% of the capacitance retained after 10000 cycles at 10 A g−1. This research provides insights for the rational design of a green, renewable and eco-friendly biomass-derived porous carbon that can be widely used as supercapacitor electrode materials in the future.

ReaxFF study of the decarboxylation of methyl palmitate over binary metallic nickel-molybdenum catalysts

ABSTRACT Biodiesel has emerged as a possible replacement for fossil-based fuels, particularly in the transportation industry. Because of its high oxygen content, it has several limitations including high viscosity, pour point and cloud point. Converting biodiesel to hydrocarbons is one method of improving the poor flow properties. In this study, Reactive Force Field (ReaxFF) molecular dynamics was used to study the decarboxylation of methyl palmitate on α-NiMoO4, β-NiMoO4 and Ni3Mo catalysts. The results show that the reactions are faster in the presence of α-NiMoO4 and β-NiMoO4, and the number of stable products, carbon dioxide and ethene was higher than they were without the catalyst. With Ni3Mo catalyst, there is rapid initial formation of CO2 and C2H4 until a maximum is reached followed by a decrease in their quantity. The C2H4 was found to decompose to C2H2 and H2 while CO2 was reduced to CO. All reactions were found to follow first-order kinetics, from which the activation energies (Ea) were determined. The Ea drops from 36.89 kcal/mol for uncatalyzed reaction to 25.66, 19.34 and 11.69 kcal/mol for the α-NiMoO4, β-NiMoO4 and Ni3Mo catalysed reactions, respectively. The Ni3Mo catalysed system’s Ea was also closest to the experimentally reported value of 10.11 kcal/mol [1].

Graphene oxide quantum dots membrane: a hybrid filtration-advanced technology system to enhance process of wastewater reclamation

The inability of wastewater treatment plants to effectively remove emerging pollutants has necessitated the need to develop newer advanced technologies. An integrated approach of combining advanced oxidation processes (AOPs) and membrane technologies promises superior performances. In this study, graphene oxide quantum dots-based membranes (GQDs-Ms) were fabricated via the phase inversion method. The GQDs-Ms revealed high oxygen content and a negative surface charge. The incorporating graphene oxide quantum dots (GQDs) into the polymer matrix led to enhanced hydrophilicity, pore size, porosity, improved flux as well as superior inhibition of Escherichia coli cells. A multi-AOPs approach was used in this work, wherein AOPs were applied as both pre-treatment (using GQDs) and post-treatment (combining GQDs with peracetic acid) in the disinfection of wastewater. The evaluation of GQDs-Ms performance was carried out and compared with a commercial membrane (Film Tec™NF270). The obtained % removals with GQDs-Ms were 83.45%, 64.12%, 40.76% and 70.36% for turbidity, total dissolved solids, total organic carbon and electrical conductivity, respectively, which compared nearly with commercial membrane’s performance. Interestingly, the integrated hybrid system can further remove and inactivate microbes in wastewater. The developed hybrid filtration-advanced technology system can substantially improve conventional wastewater treatment plants for water reuse.

Enhancing overpressure and velocity of methane detonation by adding sodium chlorate with a view to fracturing shale

Contamination and inefficiency of combustion improver is an unaddressed issue in emerging in-situ methane explosive fracturing. In this work, a cleaner oxidant with higher oxygen content, NaClO3, was employed as an alternative to KMnO4. Explosion experiments on a series of NaClO3 and CH4-O2-air mixtures were conducted in a 500 L pipeline setup, whereby the influences of NaClO3 intrinsic parameters including particle diameter, specific surface area and loading concentration on the enhanced effects were first explored. It is discovered that there is a critical parameter that maximizes the specific surface area of NaClO3 after adsorption and agglomeration, thereby significantly promoting explosion. Two samples closest to it with a diameter of 22.4 and 11.9 μm, corresponding to concentrations of 0.2 and 0.1 g/L, respectively. Furthermore, the influences of equivalence ratios on the enhanced effects of two NaClO3, and the underlying improved mechanisms, were investigated. Results indicate that NaClO3 can provide sufficient O2 to promote the development of flame fronts and thus boost the wall impact and horizontal propagation of detonation waves; meanwhile, an oxygen-rich atmosphere created by decomposition can cause violent explosions in originally fuel-rich mixtures. In methane with a volume fraction of 16% and an equivalence ratio of 1.25, NaClO3 can generate an explosion overpressure of up to 33.197 MPa with a rise rate of 2.221 GPa/s, and a detonation velocity of 1.359 km/s.

Fabrication of N, O dual-doped ultra-microporous carbon from microalgae for efficient CO2 capture via deep eutectic solvent-assisted hydrothermal carbonization

A novel approach for porous carbon fabrication from microalgae is presented for efficient CO2 capture. Microalgae-derived hydrochar is produced through deep eutectic solvent-assisted hydrothermal carbonization (DES-HTC), followed by chemical activation to obtain N, O dual-doped ultra-microporous carbon. The finalized carbon exhibited high nitrogen content (3.92%), oxygen content (21.46%), and ultra-micropore volume (0.25 cm3/g). Subsequently, it exhibited excellent CO2 adsorption capacity (4.37 mmol/g) and CO2/N2 selectivity (32) at 25 °C and 1 bar. Equilibrium and in-situ FTIR spectra of CO2 adsorption substantiated that the synergy between the abundant oxygen and nitrogen functional groups and the ample ultra-micropores significantly enhanced the capacity. Characterization of hydrochar indicated that the addition of DES during HTC effectively accelerated the Maillard reaction, facilitating the insertion of nitrogen and oxygen atoms into the carbon matrix and reducing their loss in subsequent chemical activation. Furthermore, DES was found to increase thermally unstable oxygen functional groups during HTC, promoting in ultra-micropore formation during activation. These findings provide a framework for advancing microalgae-based carbon materials in CO2 capture applications.

Analysis of the possibility of solid-phase ignition of coal fuel

The article presents the results of theoretical and experimental studies of the ignition process of coal fuel particles in a pelletized state during high-temperature radiation-convective heating in an oxidizing environment. A new, different from the known, “two-temperature” mathematical model of the ignition process of a cylindrical coal pellet under intense heating conditions is presented. During the modeling, a detailed kinetic scheme of the reaction of gaseous products of thermal decomposition of coal with atmospheric oxygen was considered. The mathematical model was tested through a comparative analysis of the theoretical and experimental values of the ignition delay times of coal pellet fuel with experimental data. A wide range of heating conditions that could potentially lead to solid-phase ignition were analyzed. The research results showed that even under conditions of high oxygen content in the original coal, solid-phase ignition of coal pellets does not occur during intense heating. Based on the results of numerical modeling, it was established that the ignition process occurs in the gas phase. The oxygen released during the thermal decomposition of coal is not enough for stable gas-phase or heterogeneous ignition of pyrolysis products in the intrapore space of the fuel pellet. Based on the results of the numerical modeling, it was established that the oxygen released during the thermal decomposition of coal is significantly deficient in the intrapore space. The O2 concentration is not enough for a significant (in terms of heat flow) thermochemical intrapore reaction with gaseous and solid products of thermal decomposition.

Study on anodic dissolution behavior and surface evolution of laser-drilled Ni-based superalloys during electrochemical post-processing

Laser drilling is always accompanied by recast layers, micro-cracks, and heat-affected zones, which limit its application in engineering. Due to its unique advantages, such as no heat-affected zones, no residual stresses, and no dependence on the mechanical properties of the materials, electrochemical dissolution has been adopted to remove the laser drilling-induced surface defects. The electrochemical dissolution characteristics and surface evolution of the laser-drilled Ni-based superalloys were studied. The polarization curves and electrochemical impedance spectroscopy (EIS) of the laser-drilled materials and the substrate were measured, indicating that the laser-drilled surface had a smaller corrosion resistance than the original substrate. X-ray photoelectron spectroscopy (XPS) results showed that the laser-drilled surface had a much higher oxygen content than the substrate. Additionally, electric current efficiency curves were obtained to study the anodic dissolution behavior of Ni-based superalloys. An electric current density in the 5–40 A/cm2 range was preferred to enhance the electrochemical dissolution rate. Moreover, the effects of electric current densities and post-processing time on the surface roughness and the recast layer thickness of the laser-processed Ni-based superalloys were investigated using a NaCl and NaNO3 solution electrolyte. The evolution of the surface quality and recast layer thickness were clarified. Furthermore, an anodic dissolution model of the laser-processed surface was established to illustrate the electrochemical post-processing mechanisms. Results revealed that electrochemical dissolution could completely remove the laser drilling-induced surface defects in 20 s using a 12.5 wt.% NaNO3 solution electrolyte and a 40 A/cm2 electric current density. Finally, an electrochemical post-processed surface with surface roughness (Ra) of 1.7 µm and without a recast layer was achieved. Micro holes without recast layers and Ra of 0.69 µm were obtained with high efficiency using laser processing and electrochemical post-processing.

Three-dimensional nitrogen and oxygen co-doped hierarchical porous carbons prepared from polyacrylonitrile/polyamic acid composite films for supercapacitors

Porous carbon materials are widely used in energy storage, adsorption, catalysis, and wastewater treatment. Polymer composite films of polyacrylonitrile (PAN) and polyamic acid (PAA) were firstly prepared by phase separation with modulation of coagulation bath composition. Using these composite films as precursors, nitrogen and oxygen co-doped porous carbon materials were successfully fabricated by preoxidation, carbonization, and subsequent NaOH activation. The porous carbons had a three-dimensional interconnected structure with a specific surface area of 450–737 m2 g−1. The pore volume was 0.245–0.508 m3 g−1 and the pore size mainly located between 1 and 5 nm. The activated porous carbon obtained from PAN/PAA coagulated at a DMSO to water ratio of 3 showed a high oxygen content of 28.0 wt% and nitrogen content of 3.3 wt%. The resultant porous carbon exhibited a good mass-specific capacitance of 407.7 F g−1 at a current density of 0.5 A g−1, an excellent rate capability (237.7 F g−1 at 20 A g−1) and cyclic stability. Using the material as the electrode, a coin-cell symmetric supercapacitor (CR2032) was assembled, which provided a specific capacitance of 156 F g−1 at 0.1 A g−1 and a maximum energy density of 10.9 Wh kg−1 at a power density of 50 W kg−1. The high number of heteroatoms as well as the textural properties could be beneficial for the improvement of electrochemical performance of the carbon-based supercapacitors.

Two-step fast pyrolysis of torrefied corncobs and waste cooking oil under different atmosphere for hydrocarbons production

Biomass pyrolysis is a promising method to produce renewable energy, which can contribute to the realization of carbon neutrality. However, high oxygen content and complex composition hinder the utilization of bio-oil produced by biomass pyrolysis. A new technology, two-step fast pyrolysis of torrefied biomass derived from corncobs and waste cooking oil under CO2 atmosphere, was studied to produce hydrocarbons-rich bio-oil. Results showed that two-step pyrolysis was beneficial to the initial separation of hydrocarbons and oxygen-laden compounds. And the synergy between the torrefied corncobs and waste cooking oil occurred primarily in the second step of the two-step pyrolysis. Application of CO2 in the first step significantly decreased the total peak area of condensable organic compounds, but increased the relative content of hydrocarbons. No matter what atmosphere was used in the first step, the relative content of hydrocarbons during the application of CO2 in the second step was lower. Using a CO2 atmosphere in the first step gave better results, while using N2 in the second step tended to maximize the hydrocarbons content. Combined with CO2-assisted pyrolysis and stepwise pyrolysis, this paper provides a new idea for the thermal conversion of corncobs and waste cooking oil, to produce hydrocarbons.

Achieving synergy of strength and ductility in powder metallurgy commercially pure titanium by a unique oxygen scavenger

Excessive interstitial oxygen (O) contamination, usually causing a dramatic loss of ductility, remains a longstanding challenge for titanium (Ti) and its alloys. Here, we propose to solve this critical problem by adding a minor CaC2 oxygen-scavenger via a simple powder metallurgy (PM) pressureless sintering approach. It is found that the surface oxide layer of hydride-dehydride (HDH) Ti powder begins to dissolve into the Ti matrix between 700 °C and 800 °C during the PM sintering process. The incorporation of CaC2 can react with the surface oxide layer (617-676 °C) prior to its active dissolution and form micrometer-sized TiC and nano-sized CaTiO3 particles, significantly refining the α-Ti grains and creating clean and well-bonded interface with Ti matrix. Therefore, the unique oxygen-scavenging effect by CaC2 produces high strength and superior ductility for Ti alloy. Even with an initially high oxygen content (∼4000 ppm), the Ti-0.4 wt.%CaC2 sample still exhibits a high ultimate tensile strength of 621±25 MPa and superior elongation of 29.3±2.6%, respectively. These values correspond to an increase of 17.6% and 301.4% compared to the as-sintered commercially pure titanium (CP-Ti) properties and far exceed the ASTM standard B381 for Grade 4 wrought Ti alloy (550 MPa and 15%) with the same O content. This work offers a novel method to develop high-strength and superior-ductility Ti materials from much more affordable Ti powder.

The phytochemical study of Eleutherococcus senticosus (Rupr. &amp; Maxim) leaves in hydroponics and soil culture

Background: In the medical fieldEleutherococcus senticosus (Rupr. &amp; Maxim) (E. senticosus) or Siberian ginseng is known as a natural adaptogen and immunomodulator. All parts of E. senticosus: roots, stems, leaves, and berries, have medicinal properties. In medicine, E. senticosus is used to treat depression, Alzheimer's and Parkinson’s diseases, cardiovascular diseases, cerebral ischemia, and diabetes. The adaptogenic properties of the plant are related to its rich composition of biologically active compounds (phenylpropanoids, eleuterosides, flavonoids, phenolic acids, anthocyanins, vitamins, etc.). E. senticosus activates the body’s protection mechanisms, directly affecting tissue metabolism. It increases mental and physical performance, immunity, and protects from stress, making its use important in sports medicine and the military. The use of E. senticosus in food and dietary supplements has become popular in recent years, whereas some studies suggest that its potential benefits are the reduction of stress and enhancement of immune system function. Objective: To study the content of the main biologically active compounds of medicinal raw material (leaves) of E. senticosus, cultivated in outdoor hydroponics and soil conditions during different stages of growth and development. Methods: The spectrophotometric method was used to determine the content of total phenols, flavonoids, phenolic acids and eleutherosides in a 70 % water-alcohol extract from E. senticosus dry leaves at different phases of vegetation period. The spectra were recorded using an Agilent Cary 60 UV-Vis spectrophotometer. Moreover, the content of extractive substances was determined, and the content of vitamin C, and β-carotene in fresh leaves (State Pharmacopoeia 2015).Results:The results of our study showed that levels of phenolic compounds in the leaves of E. senticosus obtained in hydroponics and soil culture are the highest during the flowering phase (August-September). It was observed that during the flowering period, the content of total phenols, phenolic acids, and eleutherosides was 1.3 times higher, and flavonoids - 1.2 times higher compared to the vegetative phase. It is worth noting that the content of vitamin “C”, β-carotene and extractives was also higher during the flowering period. Hydroponic plants had higher content of vitamin “C”, β-carotene, and extractives, respectively by 1.4, 1.2 and 1.2 times compared to soil plants. This could be due to several factors such as the optimal content of nutrients (N=200 mg/L, P=65 mg/L, K=350 mg/L), and the high content of oxygen in the hydroponic system. Conclusion: According to the results of a phytochemical study of E. senticosus leaves grown in outdoor hydroponics and soil culture in the Ararat Valley, the highest content of biologically active compounds (eleutherosides, phenols, phenolic acids, vitamins) is recorded in hydroponic plants in the flowering period. In general, the research has practical importance,since the E. senticosus plants grown in hydroponic conditions can be a rich source for the production of natural food and dietary supplements. Keywords:biologically active compounds, adaptogen, eleutherosides, flavonoids, phenolic acids, medicinal raw material