Mixture Of CO Research Articles

Thermodynamic Analysis of an Increasing-Pressure Endothermic Power Cycle Integrated with Closed-Loop Geothermal Energy Extraction

The thermodynamic analysis of an increasing-pressure endothermic power cycle (IPEPC) integrated with closed-loop geothermal energy extraction (CLGEE) in a geothermal well at a depth from 2 km to 5 km has been carried out in this study. Using CLGEE can avoid some typical problems associated with traditional EGS technology, such as water contamination and seismic-induced risk. Simultaneous optimization has been conducted for the structural parameters of the downhole heat exchanger (DHE), the CO2 mixture working fluid type, and the IPEPC operating parameters. The CO2-R32 mixture has been selected as the optimal working fluid for the IPEPC based on the highest net power output obtained. It has been found that, when the DHE length is 4 km, the thermosiphon effect is capable of compensating for 53.8% of the pump power consumption. As long as the DHE inlet pressure is higher than the critical pressure, a lower DHE inlet pressure results in more power production. The power generation performance of the IPEPC has been compared with that of the organic Rankine cycle (ORC), trans-critical carbon dioxide cycle (t-CO2), and single-flash (SF) systems. The comparison shows that the IPEPC has more net power output than other systems in the case that the DHE length is less than 3 km, along with a DHE outer diameter of 0.155 m. When the DHE outer diameter is increased to 0.22 m, the IPEPC has the highest net power output for the DHE length ranging from 2 km to 5 km. The application scopes obtained in this study for different power generation systems are of engineering-guiding significance for geothermal industries.

Evaluation of microstructure, corrosion resistance performance, and mechanical properties of 316L austenitic stainless steel FCAW welded joints: a comparative study

ABSTRACT This research aims to not only examine the effect of different mixtures of Ar and CO2 on microstructural features and corrosion behavior of double-pass FCAW of 316L SS but also compare these characteristics with gas tungsten arc welding (GTAW) and self-shielded FCAW. Different shielding gas mixtures, namely 100%Ar, 100%CO2, 82%Ar+18%CO2 were used to make the specimens. All specimens represent biphasic microstructures containing austenite (Ɣ) and delta-ferrite (δ-ferrite). Based on the potentiodynamic (PD) test results, the anti-corrosion protection performance of the welded region was enhanced when using GTAW compared to self-shielded FCAW. Additionally, the impedance value of the GTAW joint was higher than that of the FCAW-welded specimens. The ductility of welded joints was ranked as GTAW > CO2 +Ar shielded FCAW > self-shielded FCAW > CO2 shielded FCAW. The ranking of transverse tensile strength was as follows: CO2 shielded FCAW> self-shielded FCAW > CO2+ Ar shielded FCAW> GTAW.

Modeling hydrodynamic and biomass pyrolysis effects of recycled product gases in a bubbling fluidized bed reactor

Fast pyrolysis of biomass in a fluidized bed reactor is typically conducted in a nitrogen gas environment. Recycling product gas can improve the economics of operating such a system by reducing reliance on pure process streams, but much less is known about how recycling pyrolysis product gas may affect fluidization behavior and pyrolysis kinetics. Therefore, gas effects in a fluidized bed biomass pyrolysis reactor were investigated using engineering correlations, low-order models, and CFD simulations for N2, H2, CO, CO2, and CH4 carrier gas mixtures. Our findings reveal viscosity of a gas mixture can be significantly underestimated depending on the model and correlation. Furthermore, fluidization characteristics such as Umf and gas-solid convective heat transfer can be greatly affected by the gas properties. By utilizing H2 as the fluidizing gas (instead of N2), while maintaining a constant fluidization ratio (Us/Umf), the bio-oil yields can be increased ∼5%. This is due to the lower density H2 producing similar hydrodynamics as N2 at higher gas flow rates. These higher flow rates result in shorter gas residence times, and as a result, less secondary reactions that convert bio-oil to light gases and char. Model results also suggest that bio-oil yield is not significantly affected by the type of carrier gas used, with bio-oil yield varying by ∼2% across different gas mixtures while maintaining constant flow rate. This indicates that recycled pyrolytic gas can be used as the carrier gas for biomass pyrolysis.

Current Progress and Development Trend of Gas Injection to Enhance Gas Recovery in Gas Reservoirs

Conventional recovery enhancement techniques are aimed at reducing the abandonment pressure, but there is an upper limit for recovery enhancement due to the energy limitation of reservoirs. Gas injection for energy supplementation has become an effective way to enhance gas recovery by reducing hydrocarbon saturation in gas reservoirs. This review systematically investigates progress in gas injection for enhanced gas recovery in three aspects: experiments, numerical simulations and field examples. It summarizes and analyzes the current research results on gas injection for EGR and explores further prospects for future research. The research results show the following: (1) Based on the differences in the physical properties of CO2, N2 and natural gas, effective cushion gas can be formed in bottom reservoirs after gas injection to achieve the effects of pressurization, energy replenishment and gravity differentiation water resistance. However, further experimental evaluation is needed for the degree of increase in penetration ability. (2) It is more beneficial to inject N2 before CO2 or the mixture of N2 and CO2 in terms of EGR effect and cost. (3) According to numerical simulation studies, water drive and condensate gas reservoirs exhibit significant recovery effects, while CO2-EGR in depleted gas reservoirs is more advantageous for burial and storage; current numerical simulations only focus on mobility mass and saturation changes and lack a mixed-phase percolation model, which leads to insufficient analysis of injection strategies and a lack of distinction among different gas extraction effects. Therefore, a mixed-phase-driven percolation model that can characterize the fluid flow path is worth studying in depth. (4) The De Wijk and Budafa Szinfelleti projects have shown that gas injection into water drive and depleted reservoirs has a large advantage for EGR, as it can enhance recovery by more than 10%. More experiments, simulation studies and demonstration projects are needed to promote the development of gas injection technology for enhanced recovery in the future.

The Influence of Slim Tube Length on the Minimum Miscibility Pressure of CO2 Gas–Crude Oil

This study focuses on the Bozhong 25-1 oilfield formation oil as the experimental subject, systematically investigating the influence of different slim tube lengths (1 m, 12.5 m, 20 m, and 25 m) on the minimum miscibility pressure (MMP) of the CO2 and formation oil mixture system. Through slim tube experiments, the interaction process of CO2 with formation oil in slim tubes of different lengths was simulated, with a particular focus on analyzing how changes in slim tube length affect the MMP. The experiments revealed an important phenomenon: as the slim tube length gradually increased from shorter dimensions, the MMP showed a decreasing trend; when the slim tube length reached 12.5 m, this trend stabilized, meaning that further increasing the slim tube length no longer led to significant changes in the MMP, with its stable value determined to be 27.86 MPa. This phenomenon can be explained within the theoretical framework of fluid dynamics and interfacial science, where several key factors play a significant role. Firstly, the flow characteristics of the fluid inside the slim tube significantly influence it; secondly, the interfacial tension between phases is also a decisive factor; lastly, the impact of the internal microstructure of the slim tube cannot be overlooked. These aspects together form the basis for understanding the impact of slim tube length on MMP and reveal the underlying mechanisms. This research is significant for deeply understanding and quantifying this effect, providing a solid theoretical basis for optimizing CO2 flooding technology and guiding more precise operational strategies in oilfield development practices to enhance oil displacement efficiency and economic benefits.

Dicalcium ferrite: A chemical heat pump in integrated carbon capture and chemical looping combustion for the steel industry

An integrated calcium and chemical looping combustion using dicalcium ferrite (Ca2Fe2O5, C2F), a mixed phase from iron and calcium oxides, is proposed here to remove carbon (CO + CO2) contained in the blast furnace gas from the steel industry. C2F is particularly attractive in chemical looping hydrogen production due to its lower PO2, therefore C2F can split steam into H2. Here, the low PO2 property allows C2F to have endothermic combustions in CO and H2 combustion (Stage 1 in the carbonator). The heat of combustion is chemically stored as reduced-carbonated C2F to be utilised for sorbent regeneration (Stage 2 in the calciner), essentially pumping the heat from the carbonator to the calciner. Combustion that occurred at PCO/PCO2 of the typical BFG in which the C2F should have not been able to combust CO, suggesting an enhanced combustion phenomenon. Experiments demonstrated in a fluidised bed and a thermogravimetric analyser led to indications that rather than following reaction pathways in an order of (i) C2F is reduced into CaO and metallic Fe and (ii) the CaO is absorbed CO2 in Stage 1, C2F might directly form Fe + CaCO3 under a mixture of CO and CO2, allowing the C2F to react with BFG. Reincorporation of the reduced-carbonated oxides into C2F drives lower decarbonation temperatures compared to CaO alone, suggesting a promising route to improve energy efficiency in capturing carbon in the hard-to-decarbonise steel industry.

LateSearching for the most energy-efficient composition of a mixture of dimethyl ether and carbon dioxide as an air conditioning system refrigerantr

BACKGROUND: Carbon dioxide can be an alternative refrigerant for vapor compression refrigeration systems, particularly air conditioning systems (ACSs). However, its use suffers from the increased pressure in the refrigeration circuit. To solve this, for its reduction, a mixture of CO2 with a substance that has significantly lower pressures under the same conditions can be developed, for example, dimethyl ether (DME), which has zero GWP and ODP, is inexpensive and readily available. The study of DME, in particular, was conducted by the Department E4 “Refrigeration and Cryogenic Engineering, Air Conditioning and Life Support Systems” of N.E. Bauman Moscow State Technical University. DME is moderately toxic and flammable.
 AIM: This study aims to investigate the possible use of a mixture of DME and carbon dioxide for energy-efficient application in ACSs using commercially available compressors for R410A.
 METHODS: Comparative calculation analysis of the characteristics of a simple one-stage vapor compression cycle was performed using R410A and a mixture of DME and CO2 using the calculation packages Mathcad 15, Aspen HYSYS v. 10, SOLKANE8, and REFPROP.
 RESULTS: 1. The cycle on pure DME is the most effective in terms of the coefficient of performance: ε = 5.63 at an ambient air temperature of 26°C, ε = 3.07 at 40°C. 2. It is necessary to consider the influence of temperature glides, the average value of which ranges from 10°C to 30°C depending on the concentration of components. 3. At DME/CO2 ratios of 40/60% and 60/40% (in mole fraction), the discharge pressure corresponds to the discharge pressure in the R410A cycle, with 39.62 bar at an ambient temperature of 26°C and 37 bar at 40°C, respectively.
 CONCLUSIONS: An environmentally friendly mixture of DME and CO2 with low GWP and zero ODP is developed. An increase in the percentage of DME in the mixture increases the coefficient of performance and reduces the pressure range, and at the same time, significant temperature glides arise, which affects the installation efficiency, namely, the transition to a cycle with a receiver tank, i.e., with a recuperative heat exchanger between the fluorinated refrigerant flow leaving the evaporator and the fluorinated refrigerant flow leaving the condenser. The developed mixture is less efficient than the R410A refrigerant in terms of the coefficient of performance and discharge pressure. However, it is possible to further consider a mixture of DME and CO2 with concentrations of 40% and 60%, respectively, as a replacement for the R410 refrigerant because there is a correspondence of discharge pressures for serial compressors (about 40 bar); however, it is necessary to keep in mind the flammability risk of the mixture.

Electrocatalytic reduction of simulated industrial CO2 and CO mixtures: Revising chronoamperometry to enable selective gas mixture reduction via cyclic voltammetry

While substantial advancements have been achieved in the electrocatalytic reduction of pure CO2 or CO, the reduction of carbon oxide mixtures remains underexplored, a key limitation in scaling the technology for industrial applications. This underexplored domain gains practical importance by considering carbon oxide mixtures, given that CO and CO2 together constitute a large proportion of diverse industrial gas streams. However, the simultaneous reduction of mixed CO and CO2 poses a potential challenge due to their differing optimal reduction potentials, which complicates an efficient reduction process. While cyclic voltammetry (CV) is typically used for characterization, which involves sweeping between positive and negative potentials, we utilized it to conduct reduction reactions within a defined negative potential window. This approach, serving as an alternative to conventional chronoamperometry that maintains a constant potential, ensures a continuous reduction reaction throughout the entire cycling process. By employing cycling between the optimized reduction potentials of CO2 (−1.4 V) and CO (−1.6 V), CV achieved an increase in production efficiency, ranging from 25 % to 40 % for predominant products (HCOOH and C2H4), in comparison to chronoamperometry. Meanwhile, the results underscored the dependency of performance enhancement on the scan rate of cycling, revealing plausible correlations with mass transfer and electrode surface dynamics. Furthermore, the findings indicated that the selectivity towards HCOOH and C2H4 is closely related to the CO2/CO ratios of gas sources. This provides insight into the potential for modulating selectivity of industrial gas reduction for improved product quality and customization.

Thermal decomposition of polyolefins under different oxygen content. Composition of products and thermal effects

The thermal decomposition of polyethylene and polypropylene was studied under conditions of different oxygen contents in the carrier gas in the temperature range of 200–600 °C. The effect of adding an oxidizing agent to the carrier gas was studied at (O2/N2)mol ratios of 0/100; 1/99; 2/98; 4/96; 6/94; 10/90; 21/79. Combined TG-FTIR and TG-DSC techniques were used in the studies. Based on FTIR spectra, a quantitative and qualitative analysis of the process gaseous products was performed. The study showed that the thermal degradation of polyolefins can lead to mixtures of saturated and unsaturated hydrocarbons, which are an attractive substitute for natural gas for hydrogen production. The molar ratio of saturated/unsaturated hydrocarbons for PE and PP is 3/2. The composition of the gas product mixture as well as the heat balance of the process can be controlled by adjusting the oxygen concentration in the carrier gas. With a content of 3%O2 in the carrier gas for PE and 4%O2 for PP, autothermal conditions of the thermal processing of polyolefins are achieved. The addition of oxygen accelerates the transformation of polyolefins and thus lowers the optimal process temperature. The CxHyO and CO mixture, coexisting with the hydrocarbon mixture in some process variants, can be converted by the water shift reaction into a mixture of H2 and CO2.

Selective CO2 Capture from CO2/N2 Gas Mixtures Utilizing Tetrabutylammonium Fluoride Hydrates.

Gas hydrates, a type of inclusion compound capable of trapping gas molecules within a lattice structure composed of water molecules, are gaining attention as an environmentally benign gas storage or separation platform. In general, the formation of gas hydrates from water requires high-pressure and low-temperature conditions, resulting in significant energy consumption. In this study, tetrabutylammonium fluoride (TBAF) was utilized as a thermodynamic promoter forming a semi-clathrate-type hydrate, enabling gas capture or separation at room temperature. Those TBAF hydrate systems were explored to check their capability of CO2 separation from flue gas, the mixture of CO2 and N2 gases. The formation rates and gas storage capacities of TBAF hydrates were systematically investigated under various concentrations of CO2, and they presented selective CO2 capture behavior during the hydrate formation process. The maximum gas storage capacities were achieved at 2.36 and 2.38 mmol/mol for TBAF·29.7 H2O and TBAF·32.8 H2O hydrate, respectively, after the complete enclathration of the feed gas of CO2 (80%) + N2 (20%). This study provides sufficient data to support the feasibility of TBAF hydrate systems to be applied to CO2 separation from CO2/N2 gas mixtures based on their CO2 selectivity.

Oxidation of hydrogen sulfide and CO2 mixtures: Laser-based multi-speciation and kinetic modeling

Hydrogen sulfide (H2S), encountered in sour natural gas and in fossil fuel refineries, has adverse health and environmental impacts, but also the potential to be a source of clean hydrogen. This work addresses knowledge gaps and inconsistencies in H2S oxidation measurements and model predictions, emphasizing the scarcity of detailed kinetic modeling of H2S oxidation in the presence of carbon dioxide (CO2), a significant component of acid gas. This study leverages a shock tube coupled with laser absorption techniques to investigate the oxidation of mixtures of acid gas (H2S and CO2) with high H2S concentrations, equivalence ratios between 1.5 and 3.0, over the temperature range of 1300 – 1900 K and pressure near 1.3 bar. A detailed kinetic mechanism is proposed and validated through the measurement of time-histories of SO2, H2O, and CO, during fuel-rich acid gas oxidation. For the species measurements, we first conducted a comprehensive wavelength analysis for interference-free detection of the target species, providing new temperature-dependent absorption cross-section measurements of SO2 at its strongest IR band; moreover, we proposed a new laser-based thermometry technique for temperature time-history measurements behind reflected shock waves. The proposed kinetic mechanism is updated based on our recently calculated rate constants for reactions involving sulfurous species using high-level quantum chemistry and master equation calculations. The model outperforms former models at predicting measured time histories across the range of experimental conditions and elucidates different stages of the formation of target species. Important reactions in the new kinetic model are identified and discussed with reference to literature models, highlighting the reasons for the differences in model predictions.

Catalytic bi-reforming of methane as a potential source of hydrogen rich syngas: Promotional effect of strontium on the catalytic performance of Ni/MgO-ZrO2

Bi-reforming of methane (BRM) has gained significant attention due to escalating environmental concerns. This study investigates the performance of a monometallic Ni/MgO-ZrO2 catalyst with varying strontium (Sr) content ranging from 0 to 10 wt% added to the 10 wt% nickel, utilized in BRM. The synthesis of the MgO-ZrO2 support employed the co-precipitation method, while both Ni and Sr metals were added via impregnation route. The physiochemical properties of the prepared catalysts were analyzed using various characterization techniques such as X-Ray Diffraction (XRD), N2-Physisorption Analysis, Temperature-Programmed Reduction (TPR), Temperature-Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). To assess catalytic performance, the catalyst was tested in a fixed-bed continuous reactor using a reactant mixture of CH4, H2O, and CO2 in a 3:2:1 ratio, respectively, at a temperature of 800 °C. The Ni-6%Sr/ZrO2-MgO catalyst provided optimal conversion rates for both CH4 and CO2 at 95.2% and 85.7% respectively, without significant deactivation observed even after 36 h of reaction. This excellent catalytic performance was attributed to several factors, including smaller metal particle size, improved metal dispersion, stabilization of the t-phase in zirconia and synergistic effects between the Ni and Sr particles. The spent catalyst characterization including XRD, FESEM and HRTEM revealed that the addition of Sr significantly reduced carbon deposition. It also demonstrated that stable and best performance of the Ni-Sr/MgO-ZrO2 catalyst is ascribed to the production of filamentous carbon with a crystalline nanotubular structure. Conversely, the rapid deactivation of the Ni/MgO-ZrO2 monometallic catalyst may be attributed to amorphous carbon.

Poisoning Mechanism of the CO and H2S Mixture on the Anode of Polymer Electrolyte Membrane Fuel Cell

AbstractDespite the coexistence of CO and H2S in reformed hydrogen, studies on the interaction between impurities are lacking. In this study, the co‐poisoning effect of CO and H2S on a polymer electrolyte membrane fuel cell (PEMFC) is systematically investigated using a hydrogen reference electrode inserted into a membrane electrode assembly (MEA). Notably, when CO and H2S are present simultaneously, the poisoning rate is accelerated and is higher than the simple sum of the poisoning by the individual gases, suggesting a complex synergic effect between the two gases. This phenomenon can be attributed to the potential‐dependent behavior of H2S poisoning, whereas CO poisoning remains independent of the potential but depends on the total poisoning time. Therefore, the potential of the anode rises over time due to the time‐dependent CO poisoning, which accelerates the potential‐dependent H2S poisoning. As a result, the cell voltage decreases more rapidly in the CO and H2S mixture.

Refined line-shape parameters for CO lines broadened by air predicted from requantized classical molecular dynamics simulations

Line-shape parameters and their temperature dependences for CO lines broadened by air have been predicted using requantized classical molecular dynamics simulations. The latter were carried out for mixtures of CO in air for five temperatures ranging from 200 K to 400 K, all at a pressure of 1 atm. For each temperature and pressure condition, various Doppler widths have been considered enabling the calculations of absorption spectra for a large range of collisional to Doppler widths ratios. The simulated spectra were then fitted with the speed-dependent Nelkin-Ghatak, speed-dependent Voigt and Voigt profiles, providing the corresponding line-shape parameters. First-order line-mixing parameters were also retrieved. The temperature dependences of these parameters were then determined using a single power law. Comparisons between the predicted parameters and available experimental values as well as those of the latest edition of the HITRAN database show good agreements. The theoretically predicted values and their temperature dependences can thus be used for the modeling of the absorption spectrum of CO in air and to complete spectroscopic databases when accurate experimentally-determined values are not available.

Recent Advances in Coke Management for Dry Reforming of Methane over Ni-Based Catalysts

The dry reforming of methane (DRM) is a promising method for controlling greenhouse gas emissions by converting CO2 and CH4 into syngas, a mixture of CO and H2. Ni-based catalysts have been intensively investigated for their use in the DRM. However, they are limited by the formation of carbonaceous materials on their surfaces. In this review, we explore carbon-induced catalyst deactivation mechanisms and summarize the recent research progress in controlling and mitigating carbon deposition by developing coke-resistant Ni-based catalysts. This review emphasizes the significance of support, alloy, and catalyst structural strategies, and the importance of comprehending the interactions between catalyst components to achieve improved catalytic performance and stability.

Modified Cu–ZnO Catalysts Supported on the Mixture of ZnO and Zn–Al Oxide for Methanol Production via Hydrogenation of CO and CO2 Gas Mixture

Modified Cu–ZnO Catalysts Supported on the Mixture of ZnO and Zn–Al Oxide for Methanol Production via Hydrogenation of CO and CO2 Gas Mixture

Investigating arc and molten metal transport phenomena in gas metal arc welding with Ar–CO2 gas mixtures using a numerical method

This paper presents a numerical investigation of the transient transport phenomena of the arc and molten metal during gas metal arc welding (GMAW) using shielding gas mixtures ranging from 100% Ar + 0% CO2 to 80% Ar + 20% CO2. The thermophysical parameters of the Ar–CO2 mixtures, considering the presence of metal vapor, were calculated as a function for a temperature range of 1000–30 000 K. The influence of metal vapor content and CO2 proportion on the thermophysical properties of the mixed gas was discussed in detail. As the CO2 content increased from 0 to 20%, the shape of the arc changed from a bell to a cone due to the increase in mass density, specific heat, and thermal conductivity. The maximum arc temperature and velocity decreased with increasing CO2 content, resulting in larger droplets and a lower droplet transfer frequency. Although the change in electrical conductivity did not affect the arc shape, it did influence the arc temperature by altering the distribution of current density. Experiments of droplet transfer and arc behavior were carried out, and the results showed that the simulated droplet size, transfer frequency, and arc temperature distribution agreed well with the experimental values. These findings could serve as a theoretical tool for better understanding the underlying physical mechanisms of the GMAW process using different shielding gases, ultimately aiming to achieve high weld quality.

Polarized hydroxyapatite, a ceramic nanocatalyst to convert automotive carbon emissions into ethanol

This paper is aimed to develop ultrananoporous polarized hydroxyapatite (HAp) catalyst and evaluate its performance in transforming CO2 into useable ethanol considering three different scenarios: 1) a batch reaction using a mixture of CO2 and CH4 as feeding gas; 2) a batch reaction using as reactant exhaust gases captured from the fumes of diesel vehicles; and 3) a continuous flow reaction using pure CO2 as feeding gas. Ultrananoporous HAp scaffolds were prepared using a four-step process: 1) as prepared HAp powder was mixed with 60% wt. of a commercial hydrogel at low-temperature; 2) the resulting paste was shaped at low temperature to reduce the adhesion between the metallic tools and the mixture, enhancing the homogeneity of the sample; 3) the shaped paste was calcined in air by applying 1000 ºC during 2 h to eliminate the hydrogel; and 4) an external DC electric field of 3 kV/cm was imposed at 1000 ºC during 1 h to the calcined scaffold. The resulting polarized scaffolds both ultrananoporosity and catalytic activation. Thus, the mass: volume ratio of the ultrananoporous catalyst was much lower than that of conventional HAp catalyst (718 vs 5093 g/L. Furthermore, the ethanol yield was much higher (up to a factor of ×21.4) for the ultrananoporous catalyst than for the compact one, allowing us to conclude that ultrananoporous polarized HAp catalyst is a promising technology for transforming CO2 into valuable chemical products from highly polluted gases, especially those coming from road, sea and air transport.

New spinel‐structured high‐entropy oxides with high‐ and stable‐infrared radiation properties

AbstractSpinel‐structured high‐entropy oxides (HEOs), the novel materials, have recently attracted great attention for their unexpected properties and extensive applications. In this work, employing a facile scalability process of solid‐state reaction method, we synthesized a new kind of non‐equimolar (Co2/11Mn2/11Fe2/11Cr2/11Ni2/11Cu1/11)3O4 HEOs powder. However, under the same condition, the raw mixed oxide powders, with equimolar cations and higher configuration entropy, cannot form single‐phase HEOs powder but with the mixture of (Co,Mn,Fe,Cr,Ni,Cu)3O4 and residual CuO powders, ruling out the crucial role of entropy effect in forming single‐phase spinel‐structured HEOs. In addition to (Co2/11Mn2/11Fe2/11Cr2/11Ni2/11Cu1/11)3O4 powder, various (Co,Mn,Fe,Cr,Ni,Cu)3O4 HEOs powders can be obtained by controlling the Cu cation content in an appropriate range. To explore the application of the spinel‐structured HEOs in high‐temperature infrared field, the infrared radiation properties of the (Co2/11Mn2/11Fe2/11Cr2/11Ni2/11Cu1/11)3O4 powder were evaluated and exhibited a high‐infrared radiation emissivity of 0.880 in the near‐infrared wavelength range (0.78–2.5 µm) and superior thermal stability. Notably, the infrared radiation emissivity of the HEOs powder was maintained at 0.855 with a slight loss of 2.8% after high‐temperature treatment. This work not only provides a valuable strategy for fabricating high‐ and stable‐infrared radiation properties materials but also expands the great potential application of spinel‐structured HEOs to high‐temperature infrared field, such as energy saving in industrial high‐temperature furnaces.

Enhanced hydrogen storage capacity and kinetics in AZ61 alloy with nickel and cobalt additives: Insights into reaction mechanisms and activation energy

This study explores the synthesis of AZ61 alloy composite powders with Co-Ni additives using high-energy ball milling (HEBM). The powders are extensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to analyze their morphology, composition, structure, and bonding. The hydrogen storage capacity of the powders is measured using a Sievert's-type system revealing diverse capacities. For AZ61 alloy with Ni additive (2 µm), it absorbs 90% of the capacity in 410 s, showing an activation energy of 91.46 kJmol−1 and displays Mg2NiH4 as an intermediate. On the other hand, AZ61 alloy with Co additive requires 576 s to absorb 90% of the capacity, showing an activation energy of 117.23 kJmol−1 and Mg2CoH5 as an intermediate. When a mixture of Ni and Co is added to AZ61 alloy, it achieves 90% capacity absorption in 300 s. In the absence of additives, AZ61 alloy (15 µm) reaches 90% capacity absorption in 1600 s. The incorporation of additives significantly reduces the activation energy. A correlation between longer absorption times and larger activation energies provides valuable insights into the storage kinetics and activation energy associated with the hydrogen absorption/desorption process.