Relative Oxygen Content Research Articles

Chemical changes from N-doped graphene and Metal-Organic Frameworks to N-G/MOF composites for improved electrocatalytic activity

Chemical changes from N-doped graphene and Metal-Organic Frameworks to N-G/MOF composites for improved electrocatalytic activity

Rational tuning of SnO2 electron transport layer grown by atomic layer deposition for performance improvement of perovskite solar cells

Rational tuning of SnO2 electron transport layer grown by atomic layer deposition for performance improvement of perovskite solar cells

Efficient Removal of Nickel from Wastewater Using Copper Sulfate-Ammonia Complex Modified Activated Carbon: Adsorption Performance and Mechanism.

The necessity to eliminate nickel (Ni) from wastewater stems from its environmental and health hazards. To enhance the Ni adsorption capacity, this research applied a copper sulfate-ammonia complex (tetraamminecopper (II) sulfate monohydrate, [Cu(NH3)4]SO4·H2O) as a modifying agent for a Phragmites australis-based activated carbon preparation. The physiochemical properties of powdered activated carbon (PAC) and a modified form ([Cu(NH3)4]-PAC) were examined by measuring their surface areas, analyzing their elemental composition, and using Boehm's titration method. Batch experiments were conducted to investigate the impact of various factors, such as Ni(II) concentration, contact time, pH, and ionic strength, on its substance adsorption capabilities. Additionally, the adsorption mechanisms of Ni(II) onto activated carbon were elucidated via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The findings indicated that modified activated carbon ([Cu(NH3)4]-PAC) exhibited a lower surface area and total volume than the original activated carbon (PAC). The modification of PAC enhanced its surface's relative oxygen and nitrogen content, indicating the incorporation of functional groups containing these elements. Furthermore, the modified activated carbon, [Cu(NH3)4]-PAC, exhibited superior adsorption capacity relative to unmodified PAC. Both adsorbents' adsorption behaviors conformed to the Langmuir model and the pseudo-second-order kinetics model. The Ni(II) removal efficiency of PAC and [Cu(NH3)4]-PAC diminished progressively with rising ionic strength. Modified activated carbon [Cu(NH3)4]-PAC demonstrated notable pH buffering and adaptability. The adsorption mechanism for Ni(II) on activated carbon involves surface complexation, cation exchange, and electrostatic interaction. This research presents a cost-efficient preparation technique for preparing activated carbon with enhanced Ni(II) removal capabilities from wastewater and elucidates its underlying adsorption mechanisms.

Unveiling the nature of room-temperature-fabricated p-type SnO thin films: the critical role of intermediate phases, lattice disorder, and oxygen interstitials

This study showcases the use of ion-beam-assisted deposition for fabricating p-type SnO thin films at room temperature, which reveals crucial links between Hall mobility and lattice disorder, and between hole concentration and the relative content of interstitial oxygen.

Low-temperature synthesized hierarchical porous carbon from waste hydrochar with super capacity for dye adsorption

Low-temperature synthesized hierarchical porous carbon from waste hydrochar with super capacity for dye adsorption

5-ALA Improves the Low Temperature Tolerance of Common Bean Seedlings through a Combination of Hormone Transduction Pathways and Chlorophyll Metabolism.

Low-temperature stress is a key factor limiting the yield and quality of the common bean. 5-aminolevulinic acid (5-ALA), an antioxidant in plants, has been shown to modulate plant cold stress responses. However, the molecular mechanisms of 5-ALA-induced physiological and chemical changes in common bean seedlings under cold stress remains unknown. This study explored the physiological and transcriptome changes of common bean seedlings in response to cold stress after 5-ALA pretreatment. Physiological results showed that exogenous 5-ALA promotes the growth of common bean plants under cold stress, increases the activity of antioxidant enzymes (superoxide dismutase: 23.8%; peroxidase: 10.71%; catalase: 9.09%) and proline content (24.24%), decreases the relative conductivity (23.83%), malondialdehyde (33.65%), and active oxygen content, and alleviates the damage caused by cold to common bean seedlings. Transcriptome analysis revealed that 214 differentially expressed genes (DEGs) participate in response to cold stress. The DEGs are mainly concentrated in indole alkaloid biosynthesis, carotenoid biosynthesis, porphyrin, and chlorophyll metabolism. It is evident that exogenous 5-ALA alters the expression of genes associated with porphyrin and chlorophyll metabolism, as well as the plant hormone signal transduction pathway, which helps to maintain the energy supply and metabolic homeostasis under low-temperature stress. The results reveal the effect that applying exogenous 5-ALA has on the cold tolerance of the common bean and the molecular mechanism of its response to cold tolerance, which provides a theoretical basis for exploring and improving plant tolerance to low temperatures.

Effect of Kaolin on the Thermal Conversion Performance of Zhundong Sub-bituminous Coal.

In order to investigate how kaolin affects the structure and thermal conversion performance of Zhundong sub-bituminous coal (ZSBC), this study focused on analyzing the pyrolysis, combustion, and gasification of both ZSBC and a mixture of kaolin and Zhundong sub-bituminous coal (ZSBC-K) using the TG-DTG technique. The findings demonstrated that the addition of kaolin enhanced the pyrolysis and combustion performance of ZSBC-K. To explain the above phenomena, the composition and structure of char from ZSBC and ZSBC-K were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the addition of kaolin decreased the degree of graphitization of char and increased the relative content of oxygen on the surface of the char. Moreover, the addition of kaolin increased the degree of disorder of the char and formed more char pores. The rich pores were conducive to the entry of the gasification agent into the coal char particles, which enhanced the gasification activity. Additionally, the coal char mixed with kaolin contains several oxygen-containing functional groups and defect sites that facilitate the cracking and gasification performance of the macromolecular network's aromatic ring structure.

Comparative advantages analysis of oxidative torrefaction for solid biofuel production and property upgrading

This study performs the comparative advantage analysis of oxidative torrefaction of corn stalks to investigate the advantages of oxidative torrefaction for biochar fuel property upgrading. The obtained results indicate that oxidative torrefaction is more efficient in realizing mass loss and energy density improvement, as well as elemental carbon accumulation and surface functional groups removal, and thus leads to a better fuel property. The maximum values of relative mass loss, higher heating value, enhancement factor, and energy yield are 3.00, 1.10, 1.03, and 0.87, respectively. The relative elemental carbon, hydrogen, and oxygen content ranges are 1.30-3.10, 1.50-3.30, and 2.00-6.80, respectively. In addition, an excellent linear distribution is obtained between the comprehensive pyrolysis index and torrefaction severity index, with elemental carbon and oxygen component variation stemming from pyrolysis performance correlating to the elemental component and valance.

Critical firing conditions for titanium alloys by molten droplet ignition

Critical firing conditions for titanium alloys by molten droplet ignition

Effect of the carrier gas on the structure and composition of Co–Ni bimetallic nanoparticles generated by spark ablation

Spark ablation is a versatile technique for producing pure size-selected nanoparticles. The carrier gas used in spark ablation affects the nanoparticles’ generation, crystalline structure, and chemical composition. The comprehension of this phenomenon can contribute to the design of nanoparticles with tailored properties. In this paper, we evaluate the effects of reducing (95%N2 + 5%H2), inert (N2), and oxidative (air) carrier gases in a spark ablation setup with Co–Ni alloyed electrodes. The agglomerates’ particle size distribution, morphology, structure, and composition were highly dependent on the carrier gas, especially its relative oxygen content. The agglomerates were then sintered into compacted particles. Three different crystalline structures and chemical compositions were observed with X-ray diffraction and confirmed with transmission electron microscopy for the compacted particles. For 95%N2 + 5%H2 and air, single-phase (Co,Ni) and (Co,Ni)O particles were identified, respectively, whereas for N2, two-phase (Co,Ni) and (Co,Ni)O particles were obtained. This work opens up new possibilities of tuning the structure and composition, i.e., distribution of metallic and oxide phases, of the produced particles and thus tailor their properties for specific applications by simply changing the carrier gas.

Study on the Relationship between Indoor Vertical Greening and Oxygen Content in High-Rise Buildings

This article clarifies the quantitative relationship between vertical greening, indoor ventilation, and the oxygen content in high-rise buildings, with the aim of determining values for a high-oxygen-content threshold to assess the ventilation and greening of high-rise buildings. The quantitative index could be provided to architects to assist in the sustainable design of vertical greening in high-rise buildings. The quantitative index offers an effective, convenient, and environmentally friendly oxygen-content-testing method for interior spaces, while avoiding the air pollution caused by the current red phosphorus combustion method. Firstly, a floor of a high-rise building in Harbin was selected for on-site and fixed-point experiments. Secondly, through the design of a candle-burning experiment in a gas bottle, we measured the change in candle-burning time before and after installing vertical greening, as well as under different ventilation states. Finally, the changes in relative oxygen content in each functional space before and after vertical greening and under different ventilation states were statistically analyzed. The results showed that there was a potential correlation between indoor oxygen content and vertical greening placement in high-rise buildings; this correlation was found to be directly related to room orientation, the degree of the plants’ photosynthesis, and indoor airflow. In general, vertical greening should be placed in south-facing rooms. For daily ventilation, two or more windows should be opened to ensure convection in rooms, which can increase their oxygen content.

Экологическая валентность северокаспийских моллюсков к кислороду

North Caspian molluscs are characterized by high frequency of occurrence and wide variability of quantitative indicators. In studies conducted in the period from 2013 to 2017 in the water area of the western part of the Northern Caspian the frequency of molluscs was 64%. The population was in the range of 10-8290 species/m2; biomass – 0.003-1162.066 g/m2. Molluscs lived at depths of 2.5-29.0 m, with an absolute oxygen content of 1.29-8.52 ml/l, and a relative oxygen content of 21-134%. Most abundant was Abra ovata (29%). Mytilaster lineatus occured with frequency 24%. According to the results of the research, there were determined the limits of tolerance to the oxygen content for all molluscs living in the Northern Caspian, as well as the optimum zone for the most frequent representatives of malacofauna. The minimum oxygen concentration registered in the bottom water of the western part of the Northern Caspian during the study period (1.29 ml/l) is not critical for species Mytilaster lineatus, Hypanis angusticostata and Didacna barbotdemarnyi. Oxygen concentration of less than 3 ml/l is resistant to species Cerastoderma lamarcki and Abra ovata, less than 4 ml/l – to Hypanis vitrea. Other species including those encountered in rare cases are found at concentrations above 4.06 ml/l. The oxyphilous species are Hypanis semipellucida and Didacna pyramidata. Mytilaster lineatus, Didacna barbotdemarnyi and Cerastoderma lamarcki have a wide environmental valence to oxygen. The absolute oxygen content within the range 5.78-9.08 ml/l is considered the most favorable for the of molluscs development, where all species of molluscs can be found. Most species demonstrated a quantitative increase with oxygen concentrations rising from 4 to 6 ml/l.

An optical-based method to estimate the oxygen content in recycled metal powders for additive manufacturing

Powder recycling is key to enable sustainable and economically viable production of metal parts by fusion-based additive manufacturing (AM) processes. Determining the recyclability of a powder batch, however, requires continuous monitoring of the powder conditions during processing—notably the oxygen content—to avoid waste of resources while maintaining high build quality standards. In this work, we present a rapid and inexpensive method to acquire this information optically during the powder recoating step. Using a “powder bed scanner”, we capture high-resolution optical images of different powder batches and compute their relative oxygen content by assessing the colour of individual powder particles, which is a function of the surface oxide layer thickness. We compare these measurements against those obtained using conventional techniques and confirm that our method yields higher sensitivity and more consistent results. This work pinpoints a pathway to improving the recyclability of metal powders—at least of those which are heat-tintable—through continuous monitoring of their appearance during AM processes.

Impact of Bentonite Clay on In Situ Pyrolysis vs. Hydrothermal Carbonization of Avocado Pit Biomass

Biofuels produced via thermochemical conversions of waste biomass could be sustainable alternatives to fossil fuels but currently require costly downstream upgrading to be used in existing infrastructure. In this work, we explore how a low-cost, abundant clay mineral, bentonite, could serve as an in situ heterogeneous catalyst for two different thermochemical conversion processes: pyrolysis and hydrothermal carbonization (HTC). Avocado pits were combined with 20 wt% bentonite clay and were pyrolyzed at 600 °C and hydrothermally carbonized at 250 °C, commonly used conditions across the literature. During pyrolysis, bentonite clay promoted Diels–Alder reactions that transformed furans to aromatic compounds, which decreased the bio-oil oxygen content and produced a fuel closer to being suitable for existing infrastructure. The HTC bio-oil without the clay catalyst contained 100% furans, mainly 5-methylfurfural, but in the presence of the clay, approximately 25% of the bio-oil was transformed to 2-methyl-2-cyclopentenone, thereby adding two hydrogen atoms and removing one oxygen. The use of clay in both processes decreased the relative oxygen content of the bio-oils. Proximate analysis of the resulting chars showed an increase in fixed carbon (FC) and a decrease in volatile matter (VM) with clay inclusion. By containing more FC, the HTC-derived char may be more stable than pyrolysis-derived char for environmental applications. The addition of bentonite clay to both processes did not produce significantly different bio-oil yields, such that by adding a clay catalyst, a more valuable bio-oil was produced without reducing the amount of bio-oil recovered.

Polymeric Structure Evolution Behavior Analysis of Aluminosilicate-Based Smelting Slag

The physical and chemical properties of the CaO–SiO2–Al2O3–MgO slag system depend on structure evolution caused by the synergistic mechanism among the components at high temperature, especially the structural complexity of the anion group. In this study, Si–O, Al–O, and Al–Si–O anion groups were found in the high-temperature slag systems at 1773 K. The [Si2O5]2− (Q3) structural unit of the silicate polymer changed to [Si2O6]4− (Q2), [Si2O7]6− (Q1), and [SiO4]4− (Q0) as the binary basicity (R2) and ω(MgO)/ω(Al2O3) increased, while there was a trend toward a simplified structure. That is, the stability of each structural unit weakened, and the relative content of non-bridging oxygen increased. As a result, the degree of polymerization of slag decreased, and the experimental results of the relative content of non-bridge oxygen can be fitted well with the calculations from the reference documents. At the same time, the number of Si–O–Al structural units gradually decreased. The 27Al-MAS-NMR spectroscopy results showed that the structure of aluminate changed from [AlO4]5− tetrahedral structure to [AlO5]7− pentahedral and [AlO6]9− octahedral structure, and the degree of polymerization of the slag decreased. Comprehensive analysis showed that basicity controlled within 1.2 with the ω(MgO)/ω(Al2O3) ratio; less than 0.55 allows for suitable fluidity and energy-saving ability, which is beneficial for the stable and smooth production of the blast furnace.

Simultaneous aging of DGEBA/MeHHPA epoxy resin under thermal heating and gamma irradiation up to 1000 kGy

• Degradation of EP under simultaneous thermal and gamma irradiation was studied. • Thermal heating furtherly increased the thickness of the oxidized layer to 1.0 mm. • Aliphatic carbons are more sensitive to oxidation induced by gamma irradiation. • Thermal heating accelerated the degradation of EP caused by gamma irradiation. Although epoxy resins in nuclear facilities may be exposed to elevated temperatures and gamma irradiation, changes in the chemical structures and mechanical properties of a diglycidyl ether of bisphenol-A (DGEBA)/methyl hexahydrophthalic anhydride (MeHHPA) epoxy resin under these conditions have not been reported yet. In this study, we aim to understand the accelerated aging of the DGEBA/MeHHPA epoxy resin under simultaneous thermal heating and gamma irradiation. Samples were irradiated at ambient temperature and 70 °C with a dose rate of 2 kGy/h and a total dose of up to 1000 kGy. Various characterizations were performed to investigate the changes in their chemical structures and mechanical properties. The results showed that the relative oxygen content of the resin increased near the surface owing to the degradation of the main macromolecular chains, which was accompanied by a decrease in the thermal stability and glass transition temperature ( T g ). Under gamma irradiation at room temperature, the tensile strength increased with the absorbed dose up to 500 kGy and then decreased with higher doses. This trend indicated that thermal heating at 70 °C significantly enhanced the degradation of the DGEBA/MeHHPA epoxy resin upon gamma irradiation.

Unveiling the collective effects of moisture and oxygen on the photocatalytic degradation of m-Xylene using a titanium dioxide supported platinum catalyst

• The interplay between moisture and O 2 was investigated during PCD of m-xylene. • Higher humidity levels decreased the photocatalytic degradation of m-xylene. • The O 2 level controlled the total degradation efficiency of m-xylene. • Moisture inhibited the adsorption of the m-xylene and O 2 molecules on Pt/TiO 2 . • Reaction mechanisms were proposed for the photocatalytic decomposition of X. The development of practical photocatalytic system is of great significance in pursuit of efficient removal of hazardous volatile organic compounds (VOC) in indoor environments. The photocatalytic degradation (PCD) of VOC, as assessed commonly in terms of conversion efficiency (e.g., into intermediate/by-product species), is affected by the combined effects of multiple variables in the reaction environment such as relative humidity (RH) level and oxygen (O 2 ) content. In this research, the interactive relationship between such variables (e.g., RH from 0 to 100% and the O 2 level from 0 to 21%) has been studied using m-xylene (X) as model compound in a dynamic flow reactor system made of the titanium dioxide-supported platinum (Pt/TiO 2 ). Accordingly, the involvement of water (H 2 O) and O 2 is found to synergistically increase the PCD efficiency for the mineralization of xylene through the generation of a large number of reactive oxygen species (ROS: e.g., superoxide anion and hydroxyl radicals from the adsorbed O 2 and H 2 O molecules, respectively) under ultraviolet (UV) irradiation. The detailed information acquired in this research is expected to offer valuable insights into the degradation pathways of aromatic VOC and the interactive roles between PCD process variables, especially water and oxygen.

Online monitoring of an additive manufacturing environment using a time-of-flight mass spectrometer

Laser-based Directed Energy Deposition (L-DED) is a promising additive manufacturing technology, which has broad application prospects and practical value in many fields. The nondestructive testing technology of L-DED work piece quality monitoring requires high accuracy and capability for real-time process. This work developed an online monitoring system based on a miniature electron impact ion source time-of-flight mass spectrometer (EI-TOF) and a high-speed camera, which monitored the atmosphere above the molten pool area. The number of spatters was measured using a high-speed camera. The composition of the samples and spatters was measured by using element analyzer, inductively coupled plasma mass spectrometry, and electron spectroscopy. The variation in the atmosphere was measured using EI-TOF, and the results confirmed that the O2, N2 and H2O content decreased during the L-DED process. At the laser power of 400 W, the oxygen consumptions were 92.5% and 86.4% compared with those at the laser power of 500 W and 600 W, respectively. During the L-DED process, the number of spatters decreased when the laser power was increased from 400 W to 600 W. And at the laser power of 600 W, the average number of spatters was reduced to 59.3% compared with the laser power of 400 W. It can be found that dust contained a large amount of virgin powder and little spatters. It also can be found that at the laser power of 400 W, 500 W and 600 W, the amount of oxygen in the dust was 0.544%, 0.242% and 0.159%, respectively. The relative content of oxygen in the cross section of the seam was 35.58%, 43.79% and 44.30%, respectively. The deviation of the monitoring results (H2O, N2, O2) are significant at the same power when different materials was used as the substrate.

Excess soluble alkalis to prepare highly efficient MgO with relative low surface oxygen content applied in DMC synthesis

The activities of various MgO catalysts, which were prepared from different methods such as hydration synthesis, thermal decomposition, combustion, sol–gel and co-precipitation, were conducted in dimethyl carbonate (DMC) synthesis via transesterification of ethylene carbonate with methanol. MgO-P-Na2CO3-3.14 synthesized by the excess Na2CO3 precipitation compared the best catalytic activity and stability, which could be reused for seven times without obvious deactivation. The DMC yield was as high as 69.97% at 68 °C. The transesterification reaction could be separated into two steps, and the samples obtained by NaOH precipitant exhibited better ring-opening capability, while the catalysts acquired by Na2CO3 precipitant displayed superior transesterification ability. The structure-performance relationship was evaluated by multiple characterization methods. The results indicated that the as-synthesized catalyst derived from dried precursors with more crystalline magnesium carbonate was favorable for the promotion of DMC yield, and MgO-P-Na2CO3-3.14 with more Mg-O pairs, which were the active center for the transesterification of 2-hydroxyethyl methyl carbonate (HEMC) intermediate with methanol, resulted in more moderately basic sites left that was in accordance with the DMC yield variation. MgO-P-Na2CO3-3.14 with greater BET surface area and mesopore volume, relative low surface oxygen content and larger moderately basic sites amount compared the excellent activity in DMC synthesis.

Effect of acidic conditions on electrochemical desulfurization of clean coal

ABSTRACT In this study, the electrochemical indirect oxidation desulfurization of organic sulfur in coal was carried out using a diaphragmless electrolytic cell. The desulfurization effect of NaBr, HCl, HNO3, and H2SO4 in the electrolysis system with different acid concentrations of pH = 1–6 was investigated, and the reaction mechanism and desulfurization were analyzed. After the impact on coal quality. In the experiment, the clean coal with high organic sulfur content after washing from Shanxi’an Yi Coal in China was used as the raw material. After grinding, it was suspended in three different electrolyte systems of NaBr-HCl, NaBr-HNO3, and NaBr-H2SO4 to control different pH values. Desulfurization of coal particles suspended in the electrolyte is carried out by generating active oxides through electrode reaction, and the influence of desulfurization conditions on coal quality is analyzed using the whole industry analysis index and the test results of TGA, FTIR and EDS. The results show that a certain amount of NaBr and acid have different electrochemical desulfurization effects in different environments with pH = 1–6. The same acid has different desulfurization effects at different pH and different acids at the same pH, which has different effects on coal quality. There are also significant differences. The relative content of oxygen in coal samples increased after desulfurization, resulting in a decrease in the relative content of carbon, lowering the calorific value of the coal and improving the combustion performance; in the environment of HCl pH = 6, the electrolytic desulfurization reaction will cause Cl substitution reaction, H2SO4 under pH = 6 environment, the oxygen content increases significantly, causing serious deterioration of coal quality. Compared with HCl and H2SO4, HNO3 pH = 6 environment is better. It can effectively remove organic sulfur from clean coal and maintain the basic structure of coal without change, as ash content is reduced.