Increasing Oxygen Content Research Articles

Исследование влияния термической обработки в атмосфере аргона на физико-химическое состояние титановой фольги

The structure and elemental composition of titanium foil annealed in an inert ambient in the presence of hydrocarbons are studied by optical microscopy and scanning electron microscopy. The heat treatments carried out are simulated the synthesis process of multi-walled carbon nanotubes. As a result of the treatments, the plasticity of the material under study is significantly reduced. It is shown that the structure of the foil changes as a result of annealing. With an increase in the annealing temperature, an increase in carbon and oxygen concentrations is observed, and the hardness of the material increases significantly, which is probably due to the formation of titanium oxide and titanium carbide in the foil structure.

Far-field signature of fire in low gravity: Influence of ambient oxygen content and pressure on size distribution of smoke particles

Fire detection in space habitats is hindered by the unique characteristics of smoke particles released by weakly buoyant flames. For the first time, non-invasive measurements of particle concentration, size, and light absorption properties are performed in the downstream flow of a flame spreading in microgravity. The studied flame spreads over Low Density PolyEthylene (LDPE) coated Nickel/Chrome (NiCr) wires in an opposed oxidizer flow. The far-field signature can then be contrasted with previous measurements performed over the same configurations and related to the morphology of soot particles sampled in and behind the flame.Following measurements regarding the impact of gravity, the influence of ambient pressure and oxygen content on the characteristics of the particles is reported in microgravity. Increased pressure boosts the soot production rate, leading to higher concentration levels of particles detected for any class of particle size. Higher pressure also causes larger aggregates that exhibit a higher level of polydispersity among the constituting primary particles. This tends to enhance light absorption, more specifically at larger particle size. Less intuitively, increased oxygen content accelerates the pyrolysis rate, therefore hastening soot particles’ maturity, and ultimately increasing the detected soot concentration. In addition, enhanced oxygen content reduces organic carbon within particles, boosting light absorption regardless of the particle size. The far-field signature and its sensitivity to the ambient conditions are in decent agreement with observations of soot particles collected at the trailing edge of the flame. As a result, combining higher oxygen content and lower pressure in future space habitats as projected by the main space agencies can cancel out the effect on the detection threshold of a given flame if this threshold only includes the concentration level.

Purification of surface waters in the conditions of Karakalpakstan using microscopic and high-water plants and their application in agriculture

The article provides information on issues related to the decrease in potable water, which is currently the most pressing, about methods of water treatment without harm to health, namely using biological methods such as water purification with the help of high and low aquatic plants, as well as information on the possibilities of reusing purified waters. Recommendations are given for the use in agriculture of biomass from aquatic plants. The main research object is the “National Water Supply Company in Karakalpakstan.” Water for treatment was taken from drinking water sources. Pistia (Pistia stratiotes L.) is considered a perennial annual aquatic plant, its leaf length is 10-12 cm, and width is 6-8 cm. Lemna minor L. is relatively small, its leaves and fronds are tubular in shape, with a length of 2-4 mm and a width of 2-3 mm. Chlorella vulgaris, Lemna minor. L., and Pistia stratiotes. L. are bred in fish ponds, enzymes that counteract pathogenic microorganisms such as bacteria, viruses, and fungi are produced in water and destroy pathogenic microorganisms. Chlorella vulgaris increases oxygen content in fish ponds by 30-40%, meaning it emits 200 times more oxygen from its biomass.

Combined flow, temperature and soot investigation in oxy-fuel biomass combustion under varying oxygen concentrations using laser-optical diagnostics

In pulverized oxy-fuel biomass combustion, intricate interaction of complex fluid-mechanical, particle-dynamical, and chemical processes manifests even at intermediate scales. This study performs a comprehensive analysis aimed to understand the processes of flame stabilization, pollutant formation, and combustion behavior of biomass particles, while evaluating the impact of varying oxygen concentration on combustion. The investigation is conducted with a comprehensive data set, encompassing various oxy-fuel operation conditions ranging from 27vol.% to 36vol.% in O2 concentration, along a comparable air flame. These conditions are realized in an optically accessible gas-assisted solid fuel combustor designed to generate flames up to 70kWth. Advanced laser-optical diagnostics are employed to capture the combustion process. These techniques include the use of two-phase PIV/PTV for simultaneous measurements of flow and particle velocities, the application of tomographic absorption spectroscopy to elucidate three-dimensional gas temperature distributions, and the establishment of a quasi-simultaneous LII and LIF experimental setup to capture both PAH and soot occurrences. Additionally, chemiluminescence imaging of CH∗ is incorporated. The analysis extends to both single-phase and two-phase combustion, revealing a pronounced influence of oxygen concentration on both regimes. The inner recirculation zone, characteristic of a swirl flame, decreases with increasing oxygen content, coupled with an acceleration of the main flow downwards due to heightened heat release proximate to the nozzle. In two-phase combustion, a significant combustion delay is observed compared to single-phase combustion. Furthermore, the occurrences of PAHs and soot are clearly separated, and a pronounced influence of local gas composition on soot formation is evident. Comparative examination between oxy-fuel and air combustion show that an oxy-fuel condition with an oxygen concentration just below 33vol.% closely mirrors the flame characteristics of air combustion.

Oxidation behavior and kinetics of shale oil under different oxygen concentrations

The oxidation behavior and kinetics of crude oil within tight shale differ from those of traditional light and heavy oils. In this study, the static oxidation tests on tight shale samples were conducted under different oxygen concentrations (11%, 16%, 21%, and 26%), followed by analysis of effluent gas and oxidized oil. Specifically, the compositional changes in shale oil at the molecular level were studied. Additionally, the self-ignition potential of shale oil under different oxygen concentrations was evaluated using accelerating rate calorimetry, and the corresponding kinetic parameters were determined. The results indicated that as the oxygen concentration increased from 16% to 26%, the relative abundance of O1 species decreased from 10.96% to 8.66%, whereas that of O3 species increased from 6.16% to 8.46%. Also, the relative abundance of chain saturated aliphatic acids and tricyclic naphthenic acids was observed to decrease and increase, respectively, in the shale oil oxidized at 26% oxygen concentration compared to the other shale oils oxidized at oxygen concentration lower than 26%. The shale oil displayed significant oxidation activity under different oxygen concentrations (16%, 21%, and 26%), and an increased oxygen partial pressure resulted in a shorter induction period of oxidation and higher combustion intensity. The kinetics results showed that the combustion activity of coke was enhanced while increasing oxygen concentration from 16% to 26%. The shale oil encountered fewer concentration-dependent oxidation reactions under higher oxygen concentration. Overall, this study provides valuable insights into the oxidation behavior of crude oil within tight shale.

Effects on local oxygen conditions by the invasive macrophyte Myriophyllum spicatum

Myriophyllum spicatum, Eurasian watermilfoil, is a submerged aquatic plant invasive to North America. Several characteristics found in M. spicatum provide reasoning behind its invasion success such as its ability to spread and grow rapidly as well as displace other surrounding native species. However, Eurasian watermilfoil’s effects on ecosystem functioning (such as dissolved oxygen) and how such functioning differ from effects of native vegetation have seldom been studied. Using data collected in field, we used statistical models including Gaussian multivariate linear effect models and structural equation modelling (SEM), to investigate the effect of vegetation type and cover on dissolved oxygen (DO) and temperature gradients. Here, we show that invasive Eurasian watermilfoil colonies, relative to native submerged vegetation, can have a direct effect on DO gradients. These changes in DO conditions were driven by both an increase in surface oxygen concentrations and a decrease in bottom layer oxygen concentration in dense M. spicatum vegetation. Furthermore, we find that the differences in DO gradients could be predicted from M. spicatum’s direct impact on oxygen concentration and not indirectly via its effects on water temperature. Our results demonstrate that dense colonies of M. spicatum can directly affect DO concentrations and may do so more than native macrophytes which could explain its rapid spread and potential impacts on ecosystem functioning.

Thermal hazard analysis and fire risk assessment of rocket kerosene in oxygen-enriched environment

Fire hazard of liquid fuel exposed in oxygen-rich environment is significantly greater than that in air, which should be considered in the safety risk assessment of scenarios where oxygen and fuel coexist. To reveal the effect of oxygen concentration on fuel properties and combustion characteristics of liquid fuel, a series of experiments were conducted to measure the liquid-phase component, flash point, lower flammability limit, heat release rate and flame height of rocket kerosene at different oxygen concentrations. The results show that the flash point of rocket kerosene (with an average chemical formula of C11.98H22.64) decreases nonlinearly with the increased oxygen concentrations, while the oxygen concentration has a great enhancement effect on the heat release rate and visible flame height of rocket kerosene pool fire. Prediction models of the flash point and lower flammability limit based on the Clausius-Clapeyron equation, Le Chatelier rule and decreasing temperature assumption, as well as empirical equations of the heat release rate and visible flame height, were derived for different oxygen concentrations in this work, providing a new comprehensive understanding of the effect of oxygen concentration on the rocket kerosene, and could be further applied to fire risk assessment in liquid fuel and oxygen coexisting scenarios.

Effect of Pulsed Currents on Oxygen and Carbon Contents of Trivalent Chromium Based Deposits

Hexavalent chromium salts have been identified as toxic for both humans and the environment by Health authorities, which led the authorities to take measures such as the implementation of strict rules, such as the REACH regulation. While some applications may be substituted by other processes, the thick hard chromium plating used for its functional properties in friction and wear lacks of alternatives. Among them, trivalent chromium salts have been extensively studied [1], but this kind of electrolytes presents typical difficulties, leading to more fragile coatings with through-cracks, and a typical increase of hardness up to very high values after annealing. This change in the chromium coating behavior is often attributed to a significant increase in carbon and oxygen contents [2].If temperature as well as current density have shown a great influence on both carbon and oxygen, their effects are reversed, with for example a decrease in oxygen content with temperature (due to a high solubility of hydroxides) accompanied by an increase in carbon content that leads to amorphous deposits. It is however very difficult to reduce both carbon and oxygen. The present work is built on a parallel study carried-out in the IRT M2P project CRONOS 2024, which discover the possibilities to limit the pH increase at the interface by inserting long-time toff during electrodeposition [3].Various parameters (ton times, toff times, peak current density) have been scanned for chromium deposition on a copper tip (to make the oxygen and carbon analysis easier). It has been showed that a possible control of oxygen and carbon is possible, leading to very low values and changes in deposits properties (hardness, behavior after annealing, roughness ...). The best sequence was studied for various temperatures, and the combination of parameters extensively described.Finally, 15CDV6 steel samples were coated and fully characterized.[1] P. Benaben, « An Overview of Hard Chromium Plating Using Trivalent Chromium Solutions », Plating and Surface Finishing, p. 8, 2011.[2] A. Baral et R. Engelken, « Modeling, Optimization, and Comparative Analysis of Trivalent Chromium Electrodeposition from Aqueous Glycine and Formic Acid Baths », J. Electrochem. Soc., vol. 152, no 7, p. C504, 2005, doi: 10.1149/1.1933688.[3] M. Marcelet et al., « Influence of Pulse-Current Parameters on pH Measured By Local Method », Meet. Abstr., vol. MA2019-02, no 21, p. 1046, sept. 2019, doi: 10.1149/MA2019-02/21/1046.

Experimental study on the fragmentation behavior of coal particles during gasification process in drop-tube furnace

Studying the fragmentation characteristics of coal particles is important for enhancing furnace gasification efficiency. Based on the processing method of visualization imaging technology, this study investigated the proportion of particle fragmentation, fragmentation mode, surface temperature, and other characteristics of the Fuhua Indonesian Coal (FIC) gasification process at different temperatures and oxygen concentrations in a drop-tube furnace. The results show that the proportion of fragmentation at the center was higher than the proportion of fragmentation at the outer zone under experimental conditions. The most significant difference between the two phenomena was the length of the fragmentation period and the overall structural changes. The proportion of fragmentation at the center positively correlated with an increase in temperature and negatively correlated with an increase in oxygen concentration. Under high-temperature and low-oxygen concentration conditions, FIC tends to be in the high fragmentation mode. The temperature at the time of FIC fragmentation increased with increasing particle size. Compared with the temperature, the change in oxygen concentration had a more remarkable effect on the fragmentation temperature, specifically in the outer zone. Elevating the oxygen concentration and temperature both promoted particle fragmentation. Temperature had a greater effect on fragmentation in the outer zone, while fragmentation at the center was more sensitive to changes in oxygen concentration.

Possible Role of Non-coding DNAs in the Cambrian Explosion

The "Cambrian explosion" (CE) refers to a sharp increase in the number of fossils of living beings in the sediments of the Cambrian period (CP), which began 538.8 ± 0.2 million years ago and ended 485.4 ± 1.9 million years ago. It was in the CP that drastic changes took place in the biosphere: if before that almost all life was simple and unicellular, then after the CE there was a sharp increase in the number of complex multicellular organisms. However, the reason(s) for these drastic changes remains unknown. Various hypotheses were put forward: a sharp change in climate; the appearance of sexual reproduction; bilaterality or an increase in oxygen concentration that allowed the development of multicellularity. Apparently, the essence of the problem is to clarify the mechanisms and material basis of fundamental changes in the biosphere. For such an explosion, radical changes in the genome are necessary. It is suggested that the CE is associated with the evolution of the most mobile part of the eukaryotic DNA genome, rather than an increase in the number of previously existing or newly emerged genes. From our point of view, the evolution of non-coding DNAs, which make up the vast majority of DNA in the eukaryotic genome, could play an important role in the emergence of CE.

Influence of oxygen on the optical and electrical properties of magnetron-sputtered indium tin oxide thin films at ambient temperature

Indium Tin Oxide (ITO) thin films are commonly used as transparent conductive layers in the production of solar cells. ITO films are typically heat-treated at temperatures exceeding 200 °C after magnetron sputtering to optimize the physical, optical, and electrical characteristics for photovoltaic devices. This high temperature heating procedure greatly limits the use of potential substrates, particularly those comprised of low-temperature-rated polymers. Herein, we examine the physical, optical, and electrical transport effects of oxygen:argon plasmas during radio frequency magnetron sputtering of ITO on glass and flexible polymer surfaces without subsequent heat treatment. ITO thin films were characterized via sheet resistance testing, UV–Vis spectroscopy, X-ray diffraction, and scanning electron microscopy imaging. Sheet resistance measurements revealed an increase in surface resistance with increasing oxygen concentration during sputtering. UV–Vis optical transmittance measurements demonstrated an improvement in optical transmittance with an increase in oxygen concentration reaching a maximum transmittance at an oxygen concentration of 1-2%. Most importantly, it was discovered that producing bilayers of ITO with pure argon sputtered plasmas followed by oxygen:argon plasmas produced ITO thin films with suitable resistance and transmittance without the need for high temperature post annealing. These results highlight a methodology for the deposition of ITO thin films on temperature sensitive substrates for flexible photovoltaics and low-cost module production.

Obtaining accurate non-methane hydrocarbon data for ambient air in urban areas: comparison of non-methane hydrocarbon data between indirect and direct methods

Abstract. Since non-methane hydrocarbons (NMHCs) include numerous species of volatile organic compounds (VOCs), they are the only indicators that can characterize the total amount of VOCs in ambient air. More than 90 % of NMHC instruments in the market use the indirect method for NMHC determination, utilizing a gas chromatograph to determine the concentrations of total hydrocarbons (THCs) and methane in air. However, we found indirect NMHC measurements incorrectly characterized the low NMHC concentrations in the urban air. These measurements were hindered by the uncertain changes in the errors associated with low THC concentrations, humidity and macroscopic substances (oxygen) in the atmosphere. In this study, we conducted intercomparisons between 10 instruments in the market using different operation principles; among these, two used the direct method, and eight used the indirect method. For the indirect method, experiments showed that when the NMHC concentration was 50 ppb C, the errors in the measurement results were 32 % (CH4) and 98 % (THC) when compared to theoretical values. The oxygen content in the sample gas directly affected the response of the THC. The effect of increased oxygen content on the analysis of oxygen-containing substances was more significant than that of the increase in hydrocarbon substances. The response of dry zero was blank, and the response value increased non-linearly with relative humidity (RH). RH had a great impact on low NMHC concentrations of nearly 50 %. For the direct method, although various flow designs were applied for different instruments, the results indicated that they generally showed lower interference and higher accuracy for the ambient NMHC measurements. With the online direct methods, we obtained more reliable data and characteristics for low-concentration NMHCs in downtown Shanghai. The median of hourly data was 163.1 ppb C, and the highest ratio of the maximum and minimum concentrations of NMHCs reached 9.56 in a single day.

Oxidation dynamics of Cu thin film on Si surface by mass analyzed O+ ion implantation and study their electrical and optical properties

In this article, the ion beam-induced oxidation dynamics of copper (Cu) thin film and transport properties of the ion-modified films, deposited on Si substrate by e-beam evaporation, are investigated. Low energy (10 keV) O+ ion bombardment on Cu films at normal incidence leads to the formation of cuprous oxide (Cu2O) and cupric oxide (CuO) phases at different stages of bombardment. The dynamical change of the cuprous oxide (Cu2O) phase to the mixture of Cu2O and CuO phases with increasing ion fluence is observed via X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction. Ion implantation leads to a decrease in crystalline size with an increase in ion fluence. The increase of oxygen concentration and the absence of foreign impurities in Cu films at higher ion fluence are also measured by XPS and Energy-Dispersive X-ray spectroscopy. The oxygen concentration reduces from 82 % to 58 % for the cuprous oxide phase, whereas the same increases from 18 % to 42 % for the cupric oxide phase. The optical response due to enhancement of the oxygen atoms in ion-modified Cu thin films investigated using UV–visible spectrophotometer, shows higher absorption in the visible region compared to untreated Cu film. Post-bombardment changes in resistivity of copper oxide films, containing the mixture of two chemical phases, exhibit metallic and semiconducting behavior at temperatures 10–110 K and above 110 K, respectively. Temperature varying (300–350 K) Hall measurements of the oxygen implanted Cu film shows changes in the threshold values of mobility (1.4 to 2.4 cm2/Vs), resistivity (18 × 10−6 -150 × 10−6 Ω-cm) and carrier concentration (2 × 1022 -15 × 1022 cm−3). The potential applications of pure copper oxide films prepared by low-energy ion implantation without thermal treatment are also addressed here.

Reverse combustion propagation in an oxygen-limited and -enriched N2/O2 flow for a bed packed with rice husk

Propagation characteristics of reverse combustion significantly impact the conversion of solid fuels in packed beds, especially under variable reaction atmosphere conditions. In this study, the propagation of reverse combustion was experimentally studied in an oxygen-limited and -enriched O2/N2 flow with an oxygen concentration range of 21–100 % for a bed packed with rice husk. The temperature profile measured by thermocouples along the bed height was processed to appreciate the driving mechanism of combustion front, as well as the reaction structure inside the bed. Besides, the contribution of volatiles gas-phase oxidation and char surface oxidation to reverse combustion was also evaluated. Results show that compared to the air case, an oxygen-enriched condition broadens the operating range of oxygen flow rate for the oxygen-limited reverse combustion. Under high oxygen concentration conditions, the low-temperature oxidation of rice husk inside the reaction front becomes enhanced. Such chemical reaction effect widens the whole reaction front thickness and thereby reduces the oxidation intensity in local regions, resulting in a faster ignition rate and a lower temperature for combustion front. It is found that this process is dominated by the gas-phase oxidation of volatiles, of which oxygen consumed is above 60 % of the supplied. As oxygen concentration increases, the gas-phase oxidation of volatiles becomes further enhanced. Correspondingly, the oxidation ratio of char is gradually approaching a limit, about 12 %, especially at the oxygen concentration above 50 %. These findings will facilitate a better fundamental understanding of driving mechanism of this special combustion process and thereby provide an important theoretical basis for efficient thermal conversion of solid fuels.

BRONCHOPULMONARY DYSLASIA OF NEWBORNS AND PROSPECTS OF CELL THERAPY IN UKRAINE AND WORLDWIDE

Introduction. Premature birth is a serious challenge for modern medicine – in the world, about 14.9 million babies are born before 37 weeks of pregnancy, which is approximately 11.0% of all newborns. Bronchopulmonary dysplasia (BLD) is the most common form of chronic lung disease that affects premature babies and contributes to their morbidity and mortality. BPD develops in approximately 25.0% of infants with a birth weight of less than 1,500 g. Among infants born at less than 28 weeks' gestational age, the overall incidence of BPD is estimated to be 48–68%. The limited possibilities of BPD pharmacotherapy prompted the search for new therapeutic approaches. One of the alternatives is biological therapy based on mesenchymal stem cells (MSCs), secretome of MSCs, cryopreserved tissue extracts, etc.
 The aim of the study: to characterize current information on the therapeutic potential of mesenchymal stem cells in the treatment of newborns with bronchopulmonary dysplasia.
 Materials and methods. Publications were selected based on the databases PubMed, Clinical Key Elsevier, Cochrane Library, eBook Business Collection, and Google Scholar, which covered information about the pathogenesis of BPD and the prospects for the use of MSCs in the treatment of newborns.
 Results. Over the past decades, the understanding of the pathogenesis of BPD has evolved from a complication of secondary lung damage after mechanical ventilation and the effect of increased oxygen concentration to a multifactorial disease in which prenatal and postnatal factors are involved. Adult stem cells have been found to be naturally capable of sustaining, generating and replacing terminally differentiated cells. Stem cells function in response to physiological cell turnover or tissue damage due to trauma caused by mechanical ventilation, barotrauma, volutrauma, and hyperoxia in preterm infants. It is believed that the therapeutic effect of MSCs is related to their immunomodulatory, anti-inflammatory, angiogenic, antibacterial and regenerative effects. According to ClinicalTrials.gov, out of 301 clinical studies devoted to BPD, 18 clinical studies are currently known to study the effectiveness of MSCs in the treatment of newborns with BPD, which have already involved 770 newborns. The largest number of studies is conducted in East Asian countries (5 in China, 5 in the Republic of Korea, and 2 in Taiwan).
 Conclusions. Currently, research into the clinical therapy of BPD with stem cells is mainly focused on umbilical cord blood MSCs, umbilical cord MSCs, and bone marrow MSCs. Success in proving the safety and feasibility of incorporating stem cells for BPD led to the appearance of the biological drug PNEUMOSTEM® – a product of allogeneic MSCs obtained from human umbilical cord blood.

Effect of modified atmosphere packaging assisted cold plasma on performance of edible soybean protein isolate films

The preparation of bioactive materials with good film-forming properties has become a hot research topic nowadays in recent years. In this study, an edible protein film with good mechanical and barrier properties was made from soybean protein isolate (SPI) in terms of physical modification. Specifically, the SPI was treated by dielectric barrier discharge cold plasma (DBD-CP) via modified atmosphere packaging (MAP). The effects of oxygen content in MAP on the structure SPI as well as its edible film surface microstructure, mechanical properties, barrier properties and opacity were all investigated. The results showed that the particle size of SPI gradually decreased with the increase of oxygen content. In addition, the surface of the resulting film became smoother and more detailed. At the same time, the elongation at break (EB), water vapor performance (WVP) and opacity of the edible film were significantly improved (p < 0.05). The functional properties of the edible film were most significantly improved when the oxygen content was 50%. Compared with control samples, the EB of the film and water contact angle increased by 122.60% and 47.70%, while the WVP and opacity decreased by 19.28% and 27.40%, respectively. Therefore, the MAP-assisted DBD-CP method has the potential of modification of edible protein film with good functional properties and facilitates the application of edible SPI film in various fields.

Synthesis of diethylenetriamine-modified carbon quantum dots for dual sensing Fe3+ and Co2+and its application

Surface modification is an important method for regulating the carbon quantum dots structure and enhancing the performance. Herein, green fluorescent carbon quantum dots (G-CQDs) were synthesized by the solvothermal method using p-phenylenediamine as carbon source, diethylenetriamine as modifier and anhydrous ethanol as solvent. G-CQDs were characterized by TEM, FTIR, XPS, UV–Vis absorption spectroscopy, fluorescence spectroscopy and Zeta potential. The particle size of G-CQDs was about 2.11 nm and the fluorescence quantum yield of G-CQDs was increased from 1.07 % to 28.90 % after diethylenetriamine modification. The increase of nitrogen and oxygen contents after modification enriches the oxygen-containing and nitrogen-containing groups on the surface, providing more reaction sites for metal ions. It was further found that G-CQDs can detect Fe3+ and Co2+ based on two different fluorescence “on-off” mechanisms with detection limits of 0.88 μM and 0.95 μM, respectively. In practical applications, the excellent fluorescence performance of G-CQDs for information anti-counterfeiting has a good effect. It was used for the detection of Fe3+ and Co2+ in tap water, the spike recovery were in the range of 98.11 % ∼ 106.80 % and 95.87 % ∼ 104.49 %, respectively, showing good accuracy and reproducibility.

Experimental study on the catalytic effect of AAEMs on NO reduction during coal combustion in O2/CO2 atmosphere

During oxy-fuel combustion, the NO emission can be inhibited by the strongly reductive atmosphere caused by the high proportion of gasification reaction, which is a unique feature that differs from air combustion. The alkali and alkaline earth metals (AAEMs) contained in coal ash can catalyze gasification reactions, promoting the homogeneous reduction process of NO. Besides, AAEMs also suppress NO emission through catalyzing the NO heterogeneous reduction by char (CNO). Both catalytic effects of AAEMs have been studied at relatively low temperatures (below 1000 °C) in a simple atmosphere (pure CO2). However, the catalytic effect of AAEMs on NO reduction is still unclear during oxy-fuel combustion due to the more complex reaction atmosphere, higher reaction temperatures, and the presence of gasification reactions. In this work, the effect of different factors on the catalytic effect of AAEMs under O2/CO2 atmosphere is investigated. Results show that the order of the catalytic effect of AAEMs on NO reduction is Na > K > Ca > Mg, with the highest NO reduction efficiency of 30 % for Na. The catalytic effect of Na on NO reduction weakened as the temperature increases. When the temperature increased from 1373 K to 1573 K, the NO reduction efficiency (ηNO) of Na decreased from 30 % to 6 %. While the catalytic effect of Na on NO reduction strengthened as the oxygen concentration increases. When the O2 concentrations increased from 10 vol.% to 30 vol.%, the ηNO values of Na increased from 27 % to 35 %. The K-Na binary additive is more effective in reducing NO emissions than K and Na alone, with NO reduction efficiency as high as 46.8 % at a K/ Na is 1:2. Besides, the Raman test results reveal that K contributed to the conversion of amorphous carbon into a regular graphite crystal structure. Na disrupted the graphite structure resulting in more defective points appearing in the graphite lattice. These results are expected to provide a theoretical reference and new insights for the reduction of NO emission during oxy-fuel combustion.

Effect of Electrocautery and Laser Treatment on the Composition and Morphology of Surface-Modified Titanium Implants.

The purpose of this study was to investigate the effects of different peri-implantitis treatment methods (Er,Cr:YSGG laser, diode laser, and electrocautery) on various titanium implant surfaces: machined; sandblasted, large-grit, and acid-etched; and femtosecond laser-treated surfaces. Grade 4 titanium (Ti) disks, with a diameter of 10 mm and a thickness of 1 mm, were fabricated and treated using the aforementioned techniques. Subsequently, each treated group of disks underwent different peri-implantitis treatment methods: Er,Cr:YSGG laser (Biolase, Inc., Foothill Ranch, CA, USA), diode laser (Biolase, Inc., Foothill Ranch, CA, USA), and electrocautery (Ellman, Hicksville, NY, USA). Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and wettability were used to characterize the chemical compositions and surfaces of the treated titanium surfaces. Significant changes in surface roughness were observed in both the electrocautery (Sa value of machined surface = 0.469, SLA surface = 1.569, femtosecond laser surface = 1.741, and p = 0.025) and Er,Cr:YSGG laser (Ra value of machined surface = 1.034, SLA surface = 1.380, femtosecond laser surface = 1.437, and p = 0.025) groups. On femtosecond laser-treated titanium implant surfaces, all three treatment methods significantly reduced the surface contact angle (control = 82.2°, diode laser = 74.3°, Er,Cr:YSGG laser = 73.8°, electrocautery = 76.2°, and p = 0.039). Overall, Er,Cr:YSGG laser and electrocautery treatments significantly altered the surface roughness of titanium implant surfaces. As a result of surface composition after different peri-implantitis treatment methods, relative to the diode laser and electrocautery, the Er,Cr:YSGG laser increased oxygen concentration. The most dramatic change was observed after Er:Cr;YSGG laser treatment, urging caution for clinical applications. Changes in surface composition and wettability were observed but were not statistically significant. Further research is needed to understand the biological implications of these peri-implantitis treatment methods.

Experimental investigation of the failure of conical picks under thermal and abrasive effects

Conical picks are widely used in fields such as tunnel excavation, and high temperatures often occur on the surfaces of conical picks during the hard rock cutting process. To explore the influence of temperature on the wear of conical picks, a rotary cutting test was arranged. The cutting head torque, heat distribution and wear on the conical pick at different rotating speeds and cutting depths were explored. Moreover, the working process with and without cooling liquid was taken into consideration, and the mass losses of the conical pick under those conditions were analyzed. The experimental results showed that under cooling liquid conditions, the maximum temperature on the conical pick decreased by 230°C, and the mean mass loss of the conical pick decreased by 15.8 g. Therefore, high temperature could not be ignored in hard rock cutting. On the basis of these findings, a method for the measurement of rock abrasiveness was proposed in this paper, and different from previous research, the thermal effect was taken into consideration. A test bed for rock abrasiveness measurement was assembled in which a sintered WC-Co rod was used for rotary grinding on the rock sample, and the mass loss of the grinding rod was determined to evaluate the rock abrasiveness. The loading force between the grinding rod and rock sample was considered in the measurement of rock abrasiveness. The results showed that the mass losses of sintered WC-Co rods increased with the loading force. In addition, the characteristics of oxygen found from scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) showed that peeling and cracking could be found at distances of 5 mm and 10 mm from the end face of the grinding rod, and the increased oxygen content suggested obvious oxidization at those regions as well.