Mixed Atmosphere Research Articles

Enhanced photocatalytic performance of TiO2 with tunable oxygen vacancies induced by H2/N2 mixture treatment

Surface treatment can effectively modulate the surface properties of a photocatalyst to hasten the separation and transfer of photoinduced charges, ultimately achieving high photocatalytic performance. Herein, surface treatment of anatase-phase TiO2 prepared by a hydrothermal method was performed under H2/N2 mixed atmosphere. The experimental results demonstrate that roasting TiO2 in a H2/N2 atmosphere can effectively reduce partial Ti4+ to Ti3+, thereby facilitating the production of tunable oxygen vacancies (OVs) by disrupting Ti-O-Ti bonds. OVs can construct defective energy levels to bring about a decrease in the bandgap of TiO2 and an extension of light absorption range. Moreover, OVs remarkedly improve the separation of photoinduced charges of TiO2 and accelerate the photocatalytic reaction as active sites. The photocatalytic experimental results demonstrate that TiO2 exhibits the highest performance when roasting TiO2 in a H2/N2 atmosphere for 2 h, and the photocatalytic degradation rate constant of rhodamine B (RhB) and tetracycline (TC) on this sample under simulated solar light irradiation is 2.24 and 1.11 times higher than that on the reference TiO2, respectively. These findings provide valuable insights for designing highly efficient photocatalysts for effective water pollution treatment.

The combustion mechanism of aluminium in the steam/carbon dioxide mixed atmosphere

AbstractThe ignition and combustion characteristics of aluminium (Al) in the steam/carbon dioxide (H2O/CO2) mixed atmosphere were calculated by using a close homogeneous catch reactor and premixed laminar flame‐speed of CHEMKIN‐PRO. The effects of initial reaction temperature and H2O/CO2 ratios on the system temperature, products, and ignition delay time were explored. The main reaction paths were analyzed by the temperature sensitivity. Al (l) entered the system with a pronounced phase transition and only one heating stage, but there are two heating stages in the Al (g) system. The reaction of Al in the H2O/CO2 mixed atmosphere has a positive effect on the ignition delay time of the system. The high contents of CO2 in the H2O/CO2 mixed atmosphere can increase the maximum temperature of system and decrease the ignition delay time. Temperature sensitivity analysis shows that AlO, Al2O, and AlOH are important intermediate products, and Al2O2 is the main substance that produces Al2O3. The dominant reaction path is Al → AlOH→AlO → Al2O → Al2O2 → Al2O3. In addition, when the initial temperature was 2300 K, the laminar flame velocity was calculated to reach 35.6 m/s.

The corrosion behavior of Al2O3-SiO2 refractory in reducing atmosphere

Hydrogen metallurgy technology is essential for reducing CO2 emissions. Hydrogen (H2) serves as an ideal energy carrier to replace carbon-based fuels, producing only water as a byproduct. Al2O3-SiO2 refractories are commonly used in hydrogen metallurgy technology, including in technologies like HyCROF(Hydrogen-enriched Carbonic oxide Recycling Oxygenate Furnace) and gas heating furnaces. It is important to systematically study their corrosion in high-temperature reducing gas environments. The results indicated that the Al2O3-SiO2 refractory remained stable in pure H2 atmosphere at temperatures below 1200 °C. However, SiO2 and mullite were reduced by H2 when the temperature was increased above 1200 °C. Carbon precipitation was observed in both pure CO atmosphere and H2-CO mixed atmosphere, resulting in an increase weight of the sample. Additionally, the sample developed mullite whiskers after heating treatment at 1200 °C in H2-CO mixed atmosphere. This study aims to clarify the corrosion mechanism of Al2O3-SiO2 refractory in reducing atmosphere and to provide a theoretical basis for the selecting and optimizing refractories for hydrogen metallurgy technology.

Enhancement of Wear and Corrosion Resistance of Ti6Al4V Alloy through Hollow Cathode Discharge-Assisted Plasma Nitriding.

In order to improve the wear and corrosion resistance of Ti6Al4V alloy, a Ti-N compound layer was formed on the alloy by plasma nitriding at a relatively low temperature (750 °C) and within an economical processing duration (4 h), in a mixture of NH3 and N2 gases with varying ratios. The influence of the gas mixture on the microstructure, phase composition, and properties of the Ti-N layer was investigated. The results indicated that the thickness of the nitrided layer achieved in a mixed atmosphere with optimal proportions of NH3 and N2 (with a ratio of 1:2) was substantially greater than that obtained in an atmosphere of pure NH3. This suggests that appropriately increasing the proportion of N2 in the nitriding atmosphere is beneficial for the growth of the nitrided layer. The experiments demonstrated that the formation of the surface nitrided layer significantly enhances the corrosion and wear resistance of the titanium alloys.

The impact of different batter mixing atmospheres on the quality of reduced sucrose sponge and cream cakes

Cakes are chemically-leavened sugar-rich bakery products. Depending on the cake type, air is incorporated differently during mixing. Sponge cake batter is a gas bubble rich foam, while cream cake batter is an emulsion containing less gas cells. Given the consumer interest in reduced sucrose food systems, we here examined the potential of using altered mixing atmospheres [pure nitrogen (N2) or carbon dioxide (CO2)] to improve reduced sucrose cake quality. The use of poorly soluble N2 resulted in voluminous, stable batter. This was especially the case for foam-type sponge cake batters. During baking of sponge and cream cake batters, leavening was similar for batters prepared either under air or N2, resulting in similar cake qualities. Use of the highly soluble CO2 as mixing atmosphere negatively affected batter density, but positively leavening during baking due to temperature-induced release of previously solubilized CO2. In foam-type sponge cake making, the significant negative effect of CO2 on batter density was not overruled by the positive effect of CO2 release during leavening/baking. In contrast, the CO2 mixing atmosphere during batter-type cream cake making had only a limited negative effect on batter density while greatly affecting leavening, and resulting in high-quality, voluminous (reduced sucrose) cakes.

Memristive gas sensor (gasistor) based on Ag/ordered TiO2 nanorods/FTO sandwich structure for evaluation of ethanol concentration in mixed ambient

Herein, we designed a memoristor-type gas sensor (gasistor) with Ag/ordered TiO2 nanorods/FTO sandwich structure for recognizing ethanol concentration in ethanol-methanol mixtures. The gas adsorption characteristics of different TiO2 substrates were first investigated by first-principle calculations. The results showed that the TiO2 surface in the low resistance state exhibited better immunity to other interfering gas molecules. However, similar adsorption energies and charge transfers calculated for adsorption of methanol and ethanol mean that the interference of methanol to the response of ethanol cannot be completely ignored. In next experiments, the Ag/TiO2/FTO gasistor with well-aligned TiO2 nanorods as the resistive layer was constructed successfully and demonstrated the stable resistive switching function and excellent retention characteristic. Further device tests confirm the ability of the gasistor in the low resistance state to discriminate between ethanol and methanol, as well as better anti-interference for other organic vapors. Also, an ultra-short recovery time (∼1.8 s) was observed by applying a direct current scanning voltage to the gasistor. Finally, to improve the recognition rate of ethanol in ethanol-methanol mixed atmosphere, a neural network algorithm based on back-propagation was incorporated and good prediction accuracy was obtained at ethanol concentrations ≥ 5 ppm.

Evolution Mechanism of Carbon Covalent Bond during Coal Activation Using Mixed Atmosphere of H2O and CO2

Evolution Mechanism of Carbon Covalent Bond during Coal Activation Using Mixed Atmosphere of H2O and CO2

Hierarchical mesoporous Co3O4@C-N nanostructure rods derived from a metal-organic framework as high-performance anode for lithium-ion battery

A uniform hierarchical mesoporous Co3O4@C-N nanostructure rods were in situ fabricated successfully by developing a facile one-step strategy. Cobalt-based metal organic framework [Co3(ndc)(HCOO)3(μ-OH)(H2O)]n with special Co chine constructed framework structure treated as a precursor directly pyrolyzed in a mixed atmosphere of argon and oxygen (95:5) at 500 °C for 2 h. According to the XRD pattern, SEM, TEM, EDS mapping images and XPS spectrum analysis, the well-defined hierarchical mesoporous Co3O4@C-N nanostructure rods showed pure Co3O4 phase, are assembled from a large number of core–shell structured Co3O4@C-N spherical particles with an ultrasmall and uniform size (∼8 nm) which were further connected by N doped carbon net to form nanostructure rods. Using as anode material for lithium-ion batteries, these hierarchical mesoporous Co3O4@C-N nanostructure rods exhibit excellent electrochemical performance with high reversible capacity, rate capability and good cycling stability. They maintained a reversible specific capacity of more than 1000 mAh/g at 100 mA/g, and the discharge specific capacities at the 5 current density of 0.1, 0.2, 0.5, 1, 2, and 5 A/g reached 1123, 1094, 1044, 979, 879 and 688 mAh/g, respectively.

Preparation of high purity phase (Bi, Pb)-2223 superconducting films by sol–gel method

In this work, a (Bi, Pb)2Sr2Ca2Cu3O10+δ ((Bi, Pb)-2223) solution with good film-forming capability and chemical stability was synthesized through using metal acetates as raw materials, acrylic acid as an additive, and anhydrous methanol as a solvent to adjust the sol formula. Subsequently, (Bi, Pb)-2223 thin films were fabricated on LaAlO3 (LAO) single-crystal substrates via dip-coating technology at different heat treatment temperatures, and the structures and properties of (Bi, Pb)-2223 films were characterized. It was found that when the sol stoichiometric ratio of Bi: Pb: Sr: Ca: Cu was controlled at 1.9: 0.35: 2: 2: 3 and the gel film was heat-treated at 860 °C and dwelled for 120 min in an mixed atmosphere of N2: O2 = 96: 4, the prepared thin film with a pure (Bi, Pb)-2223 superconducting phase exhibited excellent biaxial texture, a dense surface structure, and had a T c of 106 K and a ΔT c of 6 K. The microstructure analysis revealed a layered epitaxial growth of the film along the LAO substrate with a regular arrangement of atoms and a consistent interlayer spacing.

Collaborative disposal of exhaust gas and waste wind turbine blades: Mechanical properties of recycled glass fibres and economic analysis

The accumulation of waste wind turbine blades poses significant environmental challenges. Pyrolysis offers an industrially viable solution for both disposal and the recycling of valuable glass fibers from these blades. Exhaust gas from industrials with waste heat can be utilized to reduce the process cost. However, for mixed atmosphere of exhaust gas containing both CO2 and O2, its influence on resin matrix decomposition characteristics and fiber mechanical properties are currently unclear. This work provided a solution collaborated with exhaust gas to disposal of waste wind turbine blades, in which operating parameters (atmosphere composition and process procedure) were optimized. Results showed that the early invention at pyrolysis with low concentration of O2 in exhaust gas played a major role in facilitating the formation of surface protection. Atmosphere during oxidation of pyrolytic residual carbon was crucial in maintaining fiber strength. At this stage, the interaction between CO2 (especially at 15% concentration) and O2 could mitigating fiber degradation through promoting the re-oxidization of Si dangling bonds and reducing water corrosion. However, stepwise processing of pyrolysis first and then oxidation under exhaust gas with O2 containing was not recommended due to its little cost-effectiveness. The single step disposal of wind turbine blades collaborated with coal-fired flue gas could increase the strength of recycled glass fiber by over 50% and reduced process costs by 34%.

Experimental study and correlation analysis for the effect of hydrogen pressure on biomass fluidized hydropyrolysis under N2-H2 mixed atmosphere

The utilization of fluidized bed reactors for the biomass hydropyrolysis vapor upgrading is essential in the conversion of biomass into liquid fuels. Conducting pyrolysis experiments in fluidized bed reactors with a N2-H2 mixed atmosphere is advantageous for system operation as it allows for lower minimum operating velocities, enhances pyrolysis efficiency, and reduces heat loss. This research examines the impact of hydrogen pressure in a bubbling fluidized bed reactor using a N2-H2 mixed carrier gas, with poplar wood as the feedstock and Ni-Moγ/Al2O3 as the catalyst. Through experimental and correlation analyses, significant relationships are observed between hydrogen pressure and the production of liquid and gas-phase products, with varying effects attributed to changes in hydrogen ratio and reaction pressure. Elevated hydrogen ratios facilitate secondary reactions such as the CO2 hydrogenation, resulting in a decline in CO2 production and an elevation in the yields of light hydrocarbons and aqueous phase products. Augmenting the reaction pressure to enhance hydrogen pressure aids in promoting hydrogen saturation and cracking, and amplifying the hydrogen pressure through an increase in the reaction pressure at a specific hydrogen ratio proves more efficacious in enhancing both the quantity and quality of bio-oil produced. In the context of poplar hydropyrolysis vapor upgrading utilizing a Ni-Moγ/Al2O3 catalyst, a hydrogen ratio of 50 % at a reaction pressure of 1.5 MPa emerged as the preferred option for achieving a 12 % bio-oil yield with a moderate average bio-oil carbon number and satisfactory hydrogenation levels. This comprehensive investigation examines the influence of hydrogen pressure on biomass hydropyrolysis, highlighting variations in the impacts of changes in hydrogen ratio and reaction pressure on pyrolysis results. These results offer a theoretical framework for discerning distinctions between hydropyrolysis investigations carried out in pure hydrogen atmospheres versus mixed N2-H2 atmospheres.

Bottom-up construction of low-dimensional perovskite thick films for high-performance X-ray detection and imaging

Quasi-two-dimensional (Q-2D) perovskite exhibits exceptional photoelectric properties and demonstrates reduced ion migration compared to 3D perovskite, making it a promising material for the fabrication of highly sensitive and stable X-ray detectors. However, achieving high-quality perovskite films with sufficient thickness for efficient X-ray absorption remains challenging. Herein, we present a novel approach to regulate the growth of Q-2D perovskite crystals in a mixed atmosphere comprising methylamine (CH3NH2, MA) and ammonia (NH3), resulting in the successful fabrication of high-quality films with a thickness of hundreds of micrometers. Subsequently, we build a heterojunction X-ray detector by incorporating the perovskite layer with titanium dioxide (TiO2). The precise regulation of perovskite crystal growth and the meticulous design of the device structure synergistically enhance the resistivity and carrier transport properties of the X-ray detector, resulting in an ultrahigh sensitivity (29721.4 μC Gyair−1 cm−2) for low-dimensional perovskite X-ray detectors and a low detection limit of 20.9 nGyair s−1. We have further demonstrated a flat panel X-ray imager (FPXI) showing a high spatial resolution of 3.6 lp mm−1 and outstanding X-ray imaging capability under low X-ray doses. This work presents an effective methodology for achieving high-performance Q-2D perovskite FPXIs that holds great promise for various applications in imaging technology.

Correlating Molecular Precursor Interactions with Device Performance in Solution-Processed Cu2ZnSn(S,Se)4 Thin-Film Solar Cells.

Research efforts aimed at improving the crystal quality of solution-processed Cu2ZnSn(S,Se)4 (CZTSSe) absorbers have largely employed delicate pre- and postprocessing strategies, such as multistep selenization, heat treatment in mixed chalcogen atmospheres, and multinary extrinsic doping that are often complex and difficult to reproduce. On the other hand, understanding and tuning chemical interactions in precursor inks prior to the thin-film deposition have received significantly less attention. Herein, we show for the first time how the complexation of metallic and chalcogen precursors in solution have a stark influence on the crystallization and optoelectronic quality of CZTSSe absorbers. By varying thiourea to metal cation ratios (TU/M) in dimethylformamide (DMF) and isopropyl alcohol (IPA)-based inks, we observed the formation of nanoscale metal-organic complexes and submicron size aggregates which play a key role in the morphology of the precursor layers obtained by spin-coating and drying steps. We also identify the primary cations in the complexation and assembling processes in solution. The morphology of the precursor film, in turn, has an important effect on grain growth and film absorber structure after the reactive annealing in the presence of Se. Finally, we establish a link between metal complexes in precursor solutions and device performance, with power conversion efficiency increasing from approximately 2 to 8% depending on the TU/M and Cu/(Zn + Sn) ratios.

Exploration and development of (TiB + TiC)/Ti6Al4V through the economically viable melt hydrogenation technique

Titanium matrix composites (TMCs) are widely used for their excellent properties. This paper explores fabricating (2.5vol.%TiB + 2.5vol.%TiC)/Ti6Al4V composites under varying hydrogen concentrations in a hydrogen-argon mixed atmosphere, analyzing the microstructure through optical microscopy and scanning electron microscopy with electron backscattered diffraction patterns. The results show that hydrogen leads to microstructure refinement in the matrix, increases β phase content, and modifies reinforcing phase distribution. Three-point bend tests reveal improved room temperature fracture toughness when hydrogen gets incorporated.

Synthesis of highly dispersed metallic bismuth nanoparticles in CuO–Bi2O3–SiO2 glass-ceramics for sodium ion battery anode

The formation of bismuth and copper nanoparticles from CuO–Bi2O3–SiO2 glass by heat treatment in the presence of hydrogen and their functionality as anode active material in sodium ion batteries was examined. Oxides consisting of xCuO-(85-x)Bi2O3–15SiO2 (mol%) vitrify in the composition range of x from 5 to 30. In compositions with large amounts of copper oxide (x > 35), Cu2O crystallizes, suggesting the presence of Cu+ and Cu2+ with different valence states in the glass. Heat treatment in a mixed atmosphere of hydrogen and nitrogen resulted in the crystallization of bismuth oxide and their reduction to form glass ceramics with dispersed bismuth and copper particles. As bismuth and copper are consumed from the glass matrix by phase separation, a cross-linked structure of silica develops in residual glass matrix. The resulting bismuth particles was small in size than borate-based glass ceramics, indicating that the cross-linked silicates have an inhibiting effect on bismuth grain growth. Charge-discharge tests in a sodium ion battery showed a reversible charge-discharge profile without the initial irreversible reaction of bismuthate reduction.

The effect of nitrogen on the tensile strength of Ti–22Al–25Nb alloy using laser beam powder bed fusion

Titanium-aluminum (TiAl) based alloys have a wide application prospect in aerospace and auto-industry fields due to low density, good physical and mechanical performances. However, the mechanical strength of TiAl-based alloys is also put forward more stringent requirements with the complexity of the application conditions. In this work, an argon-nitrogen (Ar–N2) reactive atmosphere was designed to achieve nitrogen interstitial solid-solution strengthening of Ti–22Al–25Nb alloy during the laser beam powder bed fusion (PBF-LB) process. An in-depth microstructure and mechanical performance analysis for the as-printed sample under various atmosphere conditions were performed via scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The nitrogen atoms can be dissolved in the octahedral gap of the β phase through the PBF-LB in the Ar–N2 atmosphere, and a small amount of nitride was detected when the volume ratio of Ar to N2 was 95:5. Compared with 100 vol% Ar atmosphere condition, finer grains of the β phase can be obtained after using the mixed gas atmosphere, and the ratio of the O phase was significantly reduced. The yield strength and ultimate tensile strength can be increased from 932 MPa to 947 MPa–1080 MPa and 1099 MPa at room temperature, respectively. At the same time, the elongation reaches ∼11 % while obtaining higher tensile strength. The strength of as-printed Ti–22Al–25Nb alloy was improved by adopting a practical methodology without sacrificing plasticity.

Erosion behaviors and mechanisms of Ti3AlC2 material under arc discharge in various mixed atmospheres

The present study establishes an experimental platform for investigating arc erosion and explores the erosion characteristics of Ti3AlC2 material under a voltage of 10 kV in SF6/N2, SF6/CO2, and N2/CO2 environments. Our findings reveal that the arc energy and duration exhibit a gradual increase in the sequence of SF6/N2, SF6/CO2, and N2/CO2, while the breakdown strength decreases. Scanning electron microscopy (SEM) and a three-dimensional laser confocal microscope were employed to observe uneven erosion morphology. Additionally, high-speed camera footage captures the arc bending and drifting phenomenon caused by Rayleigh-Taylor instability between the arc and gas. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis were utilized to characterize the composition of eroded surfaces. Erosion models were proposed for each mixed atmosphere along with comprehensive discussions on their underlying mechanisms. This work expands the application scope of MAX phase materials while providing a theoretical foundation for designing electrical contact materials.

Evolution of Natural Ferroan Brucite Under Different Atmospheres

The study on the evolution of natural ferroan brucite (MgFe(OH)[Formula: see text] was beneficial to discovering the function of brucite in the geologic cycle and directing the reasonable utilization of brucite resources. In this study, natural MgFe(OH)2 was characterized in detail and Rietveld refinement was employed to determine the precise content and existing environment of Fe[Formula: see text]. The reaction products of MgFe(OH)2 under various atmospheric conditions, including CO2, O2 and a mixed atmosphere of CO2 and O2 were innovatively investigated to gain insights into the evolution process and the crucial role played by Fe[Formula: see text]. Accordingly, the evolution mechanism of MgFe(OH)2 under different atmospheres was afforded based on the characterization and molecular simulations like electron transfer and binding energy. Fe[Formula: see text] in MgFe(OH)2 layers could be oxidized by O2 easily and give positive layers, CO[Formula: see text] produced by CO2 dissolving in water simultaneously was attracted to finally produce CO[Formula: see text] intercalated MgFe- layered double hydroxides (MgFe-CO[Formula: see text]-LDHs) which could be used as adsorbents, catalysts and so on. This process was supported by thermodynamics and also the dominant evolution route due to the dynamic reason. The existence of Fe[Formula: see text] in MgFe(OH)2 resulted in the diversity of the evolution products. This work highlighted the composition and structure of evolution products of natural MgFe(OH)2 under different environment as well as its possible application field.

Effect of amine groups on the NO adsorptive separation selectivity of FeAl‐BDC‐NH2 MOFs

In this work, the effect of amine groups of MOFs materials on the NO separation selectivity under the simulated mixed atmosphere had been first investigated by comparison of NO adsorptive separation selectivity of Fe‐BDC, Al‐BDC, FeAl‐BDC and Fe‐BDC‐NH2, Al‐BDC‐NH2, FeAl‐BDC‐NH2 synthesized by solvothermal method. The experimental results showed that the adsorption capacity of NO by Fe‐BDC‐NH2, Al‐BDC‐NH2, and FeAl‐BDC‐NH2 was significantly larger than Fe‐BDC, Al‐BDC, and FeAl‐BDC at 100 kPa, which indicated ‐NH2 promotes the adsorption of NO and was much higher than the adsorption capacity of CO2, O2, and N2 under the same conditions. The NO adsorption capacity and selectivity of bimetallic FeAl‐BDC‐NH2 were significantly better than that of monometallic Fe‐BDC‐NH2 and Al‐BDC‐NH2. The NO adsorption capacity of FeAl‐BDC‐NH2 can reach 216.42 cc g−1, which exceeded lots of MOFs materials reported, and the adsorption selectivities of NO/CO2 and NO/O2 by IAST under the simulated mixed atmosphere reached 1,350 and 15,962. It also proved that the material adsorbed NO because NO forms NONOate with ‐NH2 by the in situ IR and enthalpy calculation of adsorption, and the adsorption mechanism of NO was preliminarily investigated. The results provided a new direction for the application of adsorption and separation of NO in flue gas.

Low oxidation conditions in pulsed laser deposition enhance polarization without degradation of endurance and retention in Hf0.5Zr0.5O2 films

Interplay between oxygen vacancies and the stabilization of the ferroelectric orthorhombic phase in doped HfO2, as well as the resulting impact on endurance and retention, is far from being well understood. In Hf0.5Zr0.5O2 (HZO) thin films, it is commonly found that high polarization occurs usually at the the expense of robustness upon cycling due to the polarization–endurance dilemma. It has been reported that HZO thin films grown by pulsed laser deposition under the mixed Ar and O2 atmosphere exhibit a high polarization. Here, we show that this strategy enables functional properties tuning, allowing to obtain HZO films with high polarization at low oxidation conditions without degradation of endurance and retention.