Optimal Porosity Research Articles

Effect of shielding gas on keyhole stability and pores in laser-CMT hybrid welding of ultra-high strength steel

Laser-CMT hybrid welding (LCHW) is a highly efficient and high-quality welding technique, showing promise for welding ultra-high strength steel (UHSS) in the aerospace industry. However, the presence of pores significantly limits its application in this field. It has been observed that using an argon-rich gas can effectively stabilize the keyhole and prevent the formation of pores. Therefore, this study aims to investigate the effect of different shielding gases on keyhole stability and porosity. The weld profile, pores, electrical signal, droplet transfer, and molten pool internal flow were carefully characterized and compared with various shielding gases. The results show that increasing the CO2 content gradually reduces weld porosity. The optimal weld formation and porosity were achieved at a CO2 content of 25 %. With the CO2 content increases, the droplets shift from off-axis upwards to downwards. This shift increases the distance between the droplet and the keyhole, reducing the time for droplet growth and promoting droplet transfer. Furthermore, the surface tension pressure gradually decreases from 3.86 Kpa to 1.1 Kpa, and at Ar + 25 % CO2, itpromote the opening of keyhole and further suppress the formation of the protrusion on the keyhole rear wall. In addition, when the CO2 content reaches 25 %, the top metal of the molten pool changes from counterclockwise flow to clockwise flow, reducing the likelihood of keyhole collapse. These effects stabilize the keyhole and suppress the formation of pores.

Development of a multi-physics numerical model for a multi-component thermoelectric generator with discontinuous porosity in the exhaust gas channel

A critical technical challenge in the energy harvesting performance of a thermoelectric generator (TEG) is the optimal utilization of the thermal energy from exhaust gas. In most TEG applications, the exhaust gas flowing through the exhaust channel exhibits high inertia forces, causing significant temperature maldistribution on the hot surfaces of thermoelectric modules (TEMs). To address this challenge, we developed a numerical model that incorporates the primary multi-physics phenomena associated with TEGs, designed with a porous flow conditioner and extended surfaces for practical use. A reliable three-zone method is employed to simulate thermoelectric energy conversion phenomena, including the resulting heat pumping and Joule heating effects in individual TEMs. The model accounts for the communication effect between electrically connected TEMs by integrating Kirchhoff’s voltage and current laws into the solving process. A selective porous media method is proposed for accurately analyzing the pressure jump induced by the flow conditioner and the porosity jump occurring at the interfaces between the flow conditioner and plate fins while ensuring model convergence reliability. The developed numerical model aligns with experimental results, showing a maximum error of 5 %. Comprehensive analyses of TEM-wise heat absorption rates and channel-wise flow distribution characteristics were conducted to identify the optimal position and porosity of the flow conditioner. The findings demonstrate that optimal use of the flow conditioner improves the net output power of the TEG by 31.5 % compared to the case without any flow conditioner.

Development and optimization of parameters for HVOF sprayed Al2O3 and ZrO2 blended aluminum coating on 316L SS

Abstract A significant number of gas turbines, aircraft engines, bearings, and automotive engines operating under a wide temperature range fail frequently due to fatigue and surface oxidation. Thus, a new coating formulation 40Al-35Al2O3-25ZrO2 was deposited on 316L SS substrate through the high velocity oxygen-fuel (HVOF) thermal spray coating method. The number of passes, spray distance and oxygen flow rate were varied by using Taguchi L9 array to achieve an optimized coating with higher hardness, less porosity, and roughness. The coating phase analysis, microstructure, elemental composition, microhardness and nano hardness were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), Vickers microhardness and nano indentation testing. The sample 5 prepared at spray distance of 20 cm and oxygen/acetylene ratio of 2 exhibited optimal hardness (1972 HV1), tensile strength (6.463 GPa), porosity (0.75%) and roughness (6.2 μm) due to α-Al2O3 and t-ZrO2 phases. Oxygen flowrate was the influential parameter contributing 48.71% to microhardness and 42.41% to roughness, while spray distance with contribution 51.62% was influential parameter for porosity.

Predicting the Impact of Parameter Uncertainty on Model-Guided Li-O2 Cathode Design

Abstract Despite their high theoretical capacity, actual performance in lithium-oxygen (Li-O2) batteries is limited by sluggish transport and kinetic processes. Cathodes must provide ample surface area to host solid reduction products, but must also support species transport to access these surfaces. Numerous modeling studies therefore attempt to optimize cathode design by identifying microstructures to balance these two needs. However, model validation has historically relied on literature-sourced transport properties, which vary greatly between studies. In this work, we develop an open source, 1-D, continuum-scale Li-O2 battery model to examine the impact of electrolyte properties on predicted Li-O2 battery performance and design. Results demonstrate that O2 diffusion and solubility have the greatest impact on optimal design. Varying O2 diffusivity within the range of literature values surveyed led to maximum energy density variations of nearly 400%. These variations have a meaningful impact on the associated design conclusions: the optimal cathode porosity varied between 55 and 75%, depending on the O2 diffusivity. Moreover, the impact of advanced micrsotructures, such as graded cathode porosity, varies greatly with changes in electrolyte transport parameter estimates. As such, fundamental studies are required to accurately measure key electrolyte properties to enable numerical simulation as a guide to Li-O2 cathode design.

FORMULATION, CHARACTERIZATION AND OPTIMIZATION OF PLGA-CHITOSAN-LOADED FATTY ACID SCAFFOLDS FOR THE TREATMENT OF DIABETIC WOUNDS

Objective: The objective of the current research to formulate Eicosapentanoic Acid/Decosahexanoic Acid (EPA/DHA)incorporated into Chitosan (CS)and Poly-Lactic-Glycolic Acid (PLGA), nanoparticles composite scaffolds to the accelerated diabetic wound healing. The main focus of this present research is to evaluate and develop the chitosan–PLGA biodegradable polymer scaffolds loaded with long-chain omega-3 Polyunsaturated Fatty Acids (PUFA’s) (EPA/DHA). Methods: Nano scaffolds were prepared by solvent evaporation method loaded with CS-PLGA, EPA and DHA to treat diabetic wounds at targeted site as pharmacotherapeutically. Upon investigation, the developed biodegradable crosslinked scaffold possesses matrix degradation, optimal porosity, prolonged drug release action than the non-cross linked scaffold. The prepared formulation containing CS-PLGA loaded with EPA/DHA were formulated as nanoscaffold for wound topical applications was carried out by using freeze drying process. Results: The prepared CS-PLGA nano scaffolds were optimized and evaluated for physicochemical properties, dynamic light scattering with a particle size of 248 nm and zeta of-24mVand Scanning Electron Microscopy (SEM) were found to be spherical. In addition, the optical properties of EPA/DHA and PLGA, along with CS, can be compared by examining their absorption and wavelength (nm) using UV-visible spectroscopy. The structural and functional groups of the prepared end products were characterized by Fourier-Transformed Infrared Spectroscopy (FT-IR) has shown good compatibility with excipients and nanoformulaton, in vitro drug release studies done by using dialysis bag membrane results find that first-order Higuchi model was followed showing 20% release in first 0.2 h. MTT(3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide) assay was carried out and it showed that both crosslinked and non-crosslinked scaffolds(110 and 120%) improved cell growth when compared to control (100%). Conclusion: Finally, the results showed that the PLGA, CS nanoscaffolds containing 98% of PUFA’s (EPA/DHA) have increased in proinflammatory cytokines production at the particular wound site and thus accelerated healing activity, depending on the pre-clinical studies have trespassed, the therapeutic potential to penetrating at wound site. The optimized nanoformulation could be a better formulation for targeting and treatment of diabetic wounds at an optimal ratio.

Fabrication of SiC-Al2O3 foam ceramic and its application in fluoride-containing water

Silicon carbide (SiC) foam ceramics demonstrate excellent filtration efficiency as filter supports due to their complex pore network and chemical stability. However, their fabrication demands high sintering temperatures (above 2100 °C), resulting in substantial energy consumption and production costs, which restricts their wider use in separation and purification application processes. To address this, we utilized fly ash, a by-product of coal combustion rich in inorganic Al₂O₃, as a sintering aid to develop a porous silicon carbide–alumina foam ceramic (SAFC) and investigated the effects of Al₂O₃ on its performance. Additionally, we introduced SAFC as an adsorbent material, synthesizing the fluoride adsorbent (La@SAFC) and evaluating its fluoride removal efficacy through batch experiments. Results indicate that Al₂O₃, as a sintering aid, promotes the sintering process by forming a liquid phase that enhances Si and C diffusion at lower sintering temperatures. SAFC containing 16 wt.% Al₂O₃ achieved optimal porosity, low bulk density, and compressive strength at a sintering temperature of 1150 °C. The addition of Al₂O₃ also facilitated mullite formation, significantly enhancing the ceramic's mechanical properties. However, excess Al₂O₃ can produce an overabundant liquid phase and gas release, potentially compromising the mechanical integrity of SAFC. Batch experiments revealed that La@SAFC exhibited strong fluoride removal from water containing competing ions across a pH range of 3–7, achieving effluent within strict discharge standards. Mechanism analysis suggested fluoride removal via ion exchange and electrostatic interaction. La@SAFC maintained high fluoride removal efficiency across five regeneration cycles, underscoring its promise for practical applications.

ИССЛЕДОВАНИЕ ПРУТКОВО-КОЛЬЧАТОГО КАТКА В ПРОИЗВОДСТВЕННЫХ УСЛОВИЯХ

One of the methods of surface tillage is its rolling, which improves the contact of seeds with the soil and creates optimal porosity to provide the necessary amounts of moisture and air for plant seeds. The optimal parameters of the roller for high-quality soil rolling were determined. The new design of the rod-ring roller proposed by us was developed taking into account the guaranteed fulfillment of agrotechnical requirements. Production studies have shown that favorable conditions for seed development are created in the soil processed by the proposed roller, which contributes to the acceleration of plant development and the formation of a larger number of grains in an ear. The optimization criterion kko, taking into account the conformity of the soil to agrotechnical requirements both in density and in fractional composition after rolling crops with a rod-ring roller was 0.74, while a smooth water-filled roller provided kko = 0.63. The optimum value of kko is achieved at a specific pressure of the roller on the soil of 1533.3 N/m, a rotation frequency of the disks with rings of 1300 min1, a speed of the rod-ring roller of 15 km/h and a gear ratio of the passive drive of 5.21. The use of the roller developed by us for compacting the soil after sowing spring wheat led to an increase in the height of seedlings by 14.5% compared to the use of a conventional smooth water-filled roller on the 7th day. In addition, the use of the developed rod-ring roller increased the yield of spring wheat by 1.2 c/ha, which ensured an increase in yield by 7.4% compared to the control variant, in which a widely used smooth water-filled roller was used. Thus, the use of a rod-ring roller improves the quality of the soil and increases the yield of spring wheat by 1.2 c/ha, which is 7.4% more than when using a smooth waterfilled roller.

Designing methacrylic anhydride-based hydrogels for 3D bioprinting

Methacrylic anhydride-based hydrogels, derived by introducing methacryloyl groups to various polymer side chains, are promising bioinks for 3D printing in medical applications. These hydrogels combine the inherent biocompatibility and therapeutic benefits of their parent polymers with the unique photocrosslinking properties conferred by the methacryloyl groups, allowing the precise control over their mechanical properties through light-curing parameters. Using three-dimensional (3D) biological compression, these hydrogels serve as bioinks for producing scaffolds with optimal porosity, facilitating cell adhesion, proliferation, and differentiation. This technology enables the precise spatial distribution of bioactive substances, offering targeted therapeutic treatment and controlled release. This review delved into recent advancements in bioprinting technologies, outlined the preparation of methacrylic anhydride-based bioinks, and summarized factors influencing the resulting biological and mechanical properties of bioscaffolds. Additionally, the properties and applications of methylpropionic anhydride-based hydrogels in various medical fields were discussed, addressing current limitations and future challenges in integrating these hydrogels with 3D bioprinting for clinical applications.

Understanding the impact of porosity on Li-ion diffusion enhancement in micro-sized silicon particles for advanced batteries

Lithium-ion batteries (LIBs) require advanced and practical anode materials, such as porous silicon (PSi), which can meet these expectations due to their rapid Li-ion diffusion rates and structural relaxation. Several studies have focused on the structural design of PSi or its composites to improve Li-ion diffusion; however, no systematic and quantitative evaluations of the impact of porosity on Li-ion diffusion and battery performance have been reported. Therefore, to understand the impact of porosity on Li-ion diffusion, we developed micro-sized porous silicon (m-PSi) particles with various porosities via metal-assisted chemical etching (MACE) method using different concentrations of AgNO3 (0.02–0.08 M). Among the as-prepared samples, m-PSi-0.06 (prepared using 0.06 M AgNO3) with ∼70 % porosity achieved a maximum Li-ion diffusion rate of 2.35 × 10−9 cm2 s−1. This led to a high-rate capability, enhanced Li-ion storage, and better cyclic retention of 61.4 % compared to the non-porous micro-sized Si (m-Si) (5.8 %) sample at a current density of 0.1 A g−1. Furthermore, the optimal porosity of m-PSi-0.06 resulted in an impressive rate capability of 760 mAh g−1 at a high current density of 4 A g−1 with a recovery rate of 80 %. The improved efficiency of m-PSi-0.06 is attributed to its optimized mesoporosity, which ensures sufficient space for Li-ion storage and shortens the effective transmission path to accelerate Li-ion diffusion. Moreover, the mesopores provide a greater number of active sites for the reversible adsorption of Li ions, thereby improving the capacitive behavior of the anode. In contrast, the highly nanoporous m-PSi-0.08, with a pore diameter of 1–3 nm, impeded Li-ion movement and restricted diffusion. These results reveal that a high nano porosity hinders Li-ion diffusion, whereas an optimal mesoporosity ensures swift diffusion in m-PSi anodes. These insights could guide the design of Si-based anode materials for advanced LIBs.

Hydrogels with Essential Oils: Recent Advances in Designs and Applications.

The innovative fusion of essential oils with hydrogel engineering offers an optimistic perspective for the design and development of next-generation materials incorporating natural bioactive compounds. This review provides a comprehensive overview of the latest advances in the use of hydrogels containing essential oils for biomedical, dental, cosmetic, food, food packaging, and restoration of cultural heritage applications. Polymeric sources, methods of obtaining, cross-linking techniques, and functional properties of hydrogels are discussed. The unique characteristics of polymer hydrogels containing bioactive agents are highlighted. These include biocompatibility, nontoxicity, effective antibacterial activity, control of the sustained and prolonged release of active substances, optimal porosity, and outstanding cytocompatibility. Additionally, the specific characteristics and distinctive properties of essential oils are explored, along with their extraction and encapsulation methods. The advantages and disadvantages of these methods are also discussed. We have considered limitations due to volatility, solubility, environmental factors, and stability. The importance of loading essential oils in hydrogels, their stability, and biological activity is analyzed. This review highlights through an in-depth analysis, the recent innovations, challenges, and future prospects of hydrogels encapsulated with essential oils and their potential for multiple applications including biomedicine, dentistry, cosmetics, food, food packaging, and cultural heritage conservation.

Performance-tunable thermal barrier coating for carbon fiber-reinforced plastic composites via flame spraying

Thermal barrier coatings (TBCs) are essential for improving the heat resistance of materials operating in high-temperature environments. This paper proposes a new method for manufacturing double-layered TBC with graded porosity for carbon fiber-reinforced plastic (CFRP) composites. The TBC was created by a flame spraying process, consisting of relatively dense and porous layers: (1) a dense layer was produced by spraying yttria-stabilized zirconia (YSZ) particles directly onto neat carbon fabric substrate and (2) a porous layer was prepared by co-spraying YSZ particles with sacrificial polyetheretherketone (PEEK) particles. The porosity of the porous layer was controlled by varying a PEEK injection distance (D) and a PEEK feed rate (R). The correlation between porosity and thermal conductivity of the TBC layer was investigated to assess its thermal barrier performance. The TBC fabricated with the D = 5 cm and the R = 1.0 g/min offered the optimal porosity and conductivity. The 640μm-thick TBC with 34% porosity and 0.27 W/m·K thermal conductivity protected the CFRP substrate remarkably under the subjected torch at 500°C, as the TBC layer reduced the surface temperature of CFRP to 230°C. Thermomechanical analysis, following thermal shock tests, revealed that the double-layered TBC/CFRP composite retained 87% and 75% of its pristine flexural strength and modulus, respectively, while the neat CFRP composite was completely burnt out. This study explored the application of flame spray technology to develop highly effective double-layered TBCs with tunable porosity to maximize their thermal barrier performances. All results from the current study provide new insights into the design and development of TBC and CFRP composites, which will benefit a wide range of lightweight high-temperature applications.

Design and parametrization of TPMS lattice using computational and experimental approach

Triply periodic minimal surface (TPMS) based lattices are extensively explored as a scaffold design for bone regeneration. TPMS maintains zero mean curvature at each point and offers a large surface area comparable to a trabecular bone. The best four TPMS minimal surfaces (IWP. Neovius, primitive, and F-RD) were selected, designed, and fabricated using acrylonitrile butadiene styrene (ABS) resin through the stereolithography (SLA) technique. The results indicate that small changes in unit cell dimensions do not significantly alter the structure topology, which ensures stress distribution within the lattice remains relatively uniform across different unit cell sizes when the porosity level is constant. The optimal unit cell size (2 to 5 mm) and porosity (70 to 80%) significantly affect the compressive strength and surface area to volume (SA/V) ratio due to a unique arrangement of the internal architecture of each TPMS unit cell. The lattice structure (formed by stacking unit cell) of unit cell size 2.11 mm with 70% porosity exhibited a maximum compressive strength of 39.8 MPa in IWP, followed by Neovius, primitive, and F-RD-based lattice structures. Moreover, the lattice showed more stability under compression force, minimized stress concentration compared to a unit cell, and exhibited distinct deformation patterns at different strain levels during compression.

Numerical study on the combined application of multiple phase change materials and gradient metal foam in thermal energy storage device

Latent heat thermal energy storage (LHTES) offers significant energy-saving benefits, but its application is limited due to the low thermal conductivity of phase change material (PCM). To address this issue, this article studied the combined application of metal foam structures with different porosity gradients and multiple PCMs with different melting points through numerical simulation to accelerate the melting of PCM and enhance system efficiency. The results showed that the application of multiple PCMs improved the heat transfer performance of the system, reducing the complete melting time by 9.18% compared to using a single PCM with uniform metal foam. Based on the multi-PCM storage system with an average porosity of 0.90, this article designed metal foam structures with one-dimensional and two-dimensional porosity gradients and explored their impacts. The results indicated that in the structure with a one-dimensional porosity gradient along the heat flow direction, the positive gradient decreased thermal resistance, further reducing the complete melting time by 6.18%, while the negative gradient increased it by 19.78%. However, the temperature non-uniformity was lowest with the negative gradient and highest with the positive gradient. The optimal two-dimensional porosity gradient multi-PCM storage model not only reduced thermal resistance but also effectively solved the issue of uneven melting, reducing the complete melting time by 17.96% and increasing the energy storage efficiency by 20.16% compared to the single PCM system with uniform porosity. Furthermore, the article conducted a dimensionless analysis of the optimal structure and different gradient structures, establishing formulas for the liquid fraction concerning modified Fourier number, modified Stefan number, and modified Rayleigh number.

Sustainable production of in-situ activated carbon from arecanut husk and their supercapacitor applications

A facile and sustainable method is adopted for the synthesis of activated carbon from arecanut husk biomass. The inherent potassium enrichment in arecanut husk is exploited for an in-situ activation process. The activated samples exhibited an optimal porosity with abundant meso/micro pores and channels making them a promising candidate for supercapacitor applications with a specific capacitance value as high as 217 Fg−1 as calculated from the CV curves. The values for non activated and KOH activated carbon samples derived from arecanut husk were only 60 and 80 % of this value respectively. A fully functional symmetric supercapacitor prototype was also fabricated which exhibited a capacitance value of 46.2 Fg−1 with an energy density of 6.1 Whkg−1 at a power density of 270 Wkg−1.

Analysis of charging performance of thermal energy storage system with graded metal foam structure and active flip method

The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is characterized by high energy storage density, small volume change, and constant operation temperature, which is widely employed in waste heat recovery, solar thermal utilization, and equipment thermal management. This paper introduces active flipping and graded porous to strengthen natural convection and heat conduction to alleviate the issue of low thermal conductivity and non-uniform phase change of PCM. Based on the fixed grid system, the enthalpy-porosity method combined with time-dependent gravity and non-Darcy porous effect is employed to solve the solid-liquid phase change problem under different porosity gradients, dimensionless flipping times (t*), and modified Ra (Ra*) numbers. Furthermore, the effects of the Ra* on the optimal t* and porosity gradient are also discussed. The results show that the flipping method can significantly enhance flow and heat transfer within the container, improve temperature field uniformity, and increase the proportion of latent heat storage. With the increase of porosity gradient and t*, the melting time initially decreases and then increases and the optimal thermal performance is achieved at a 6 % porosity gradient and t* = 0.4. Compared to the uniform porous structure without flipping, it can shorten melting time by 49.37 % and improve thermal energy storage rate (TESR) by 76.23 %. Additionally, the optimal porosity gradient is 6 % under different Ra*, but the optimal t* decreases with the increase of Ra*. This paper explores the charging performance of the thermal energy storage system with the graded metal foam structure and active flip method, which can contribute to the study of heat transfer enhancement in LHTES technology.

Using Micrometer Scale X-Ray CT and Pore Network Modeling to Assess High-Energy Bi-Layer Li-Ion Battery Cathode Structures

The optimization of cathode pore space is pivotal for enhancing the rate capability of lithium-ion battery electrodes. Previous studies on simulated cathodes have highlighted the importance of achieving an optimal porosity gradient, with a gradual increase from the current collector side to the separator side to accommodate the growing demand for ion transport in that direction [1]–[3]. In this research, we address this requirement by introducing and investigating bi-layer NCM 811 cathodes. These cathodes consist of a slurry-coated dense bottom layer and a spray-coated highly porous top layer with varying relative thickness to approximate the desired porosity gradient. Employing Micrometer-scale X-ray CT characterization and pore network modeling, we evaluate the structural features, demonstrating the effectiveness of the design, and quantify essential parameters such as porosity and tortuosity. Furthermore, the cathodes are integrated into lithium anode half-cells and subjected to electrochemical cycling at different rates to assess ion transport and rate capability. Our findings reveal that to achieve the highest discharge spatial energy density above 1C for cathodes approximately 100μm thick, the compressed bottom layer with 30% porosity should have a thickness of 60μm, while the highly porous top layer with around 47% porosity should be 40μm thick.Reference:[1] A. Shodiev et al., “Deconvoluting the benefits of porosity distribution in layered electrodes on the electrochemical performance of Li-ion batteries,” Energy Storage Mater., vol. 47, pp. 462–471, May 2022, doi: 10.1016/j.ensm.2022.01.058.[2] X. Lu et al., “3D microstructure design of lithium-ion battery electrodes assisted by X-ray nano-computed tomography and modelling,” Nat. Commun., vol. 11, no. 1, p. 2079, Apr. 2020, doi: 10.1038/s41467-020-15811-x.[3] K. Song, C. Zhang, N. Hu, X. Wu, and L. Zhang, “High performance thick cathodes enabled by gradient porosity,” Electrochimica Acta, vol. 377, p. 138105, May 2021, doi: 10.1016/j.electacta.2021.138105.

A novel nanoparticles spilled-over In2O3 microcubes-enabled sustainable chemiresistor for environmental carbon dioxide monitoring

Achieving sustainable future energy goals includes enhancing renewable energy production, optimizing daily energy consumption using feedback loops and minimizing/monitoring contributions to atmospheric carbon dioxide (CO2). Developing economic next-generation CO2 sensors enables local monitoring of industrial CO2 emissions, aiding energy management and climate monitoring. This study elucidates the efficacy of CO2 chemiresistor based on indium oxide (In2O3) micro cubes with spilled-over nanoparticles. The investigation primarily focuses on fabricating and optimising In2O3-based CO2 chemiresistors utilizing a hydrothermal technique, creating porous micro cubes essential for enhanced CO2 monitoring. As revealed by various characterization techniques, the minimum crystallite size was found to be 24.92 nm with optimum porosity and a high surface-to-volume ratio comprising spilled-over nanoparticle morphology. The fabricated chemiresistor demonstrated excellent CO2 sensing efficacy with a maximum response of around 4.1% at room temperature with selectivity, repeatability, and reversible sensing behavior. The sensing mechanism has been revealed, which is supported by theoretical density functional theory evaluations. Notably, the sensing results reveal the capability of In2O3-based sensors to detect CO2 at low concentrations as low as ⩽10 ppm, which enables the chemiresistor for practical implementation in diverse sectors to achieve sustainability.

Tailoring the surface topography and crystallinity of EuMnO3 films: A study on sintering effects

We obtained EuMnO3 films through a sol-gel process at varying temperatures, aiming to investigate spatial layout variations influenced by different sintering temperatures. Our results indicate that films adopt an orthorhombic structure when sintered between 800 °C and 850 °C, accompanied by a reduction in nanocrystal size during annealing. Surface analysis reveals that films processed at higher temperatures exhibit increased roughness, negative asymmetry, heightened kurtosis, elevated peak densities, and more distinct peak forms. Furthermore, these films display surfaces with greater anisotropy and lower spatial frequencies compared to those sintered at lower temperatures. Nevertheless, fractal analysis uncovers that both the EuMnO800 and EuMnO850 samples showcase heightened spatial complexity, a more uniform nanotexture, optimal surface porosity, and improved topographic consistency. The findings suggest that films sintered at 800 °C display a spatial arrangement with superior topographic qualities, rendering them potentially valuable for the advancement of semiconductor films derived from perovskite rare-earth oxides for various technological applications.

Hydrochar from Pine Needles as a Green Alternative for Catalytic Electrodes in Energy Applications.

Hydrothermal carbonization (HTC) serves as a sustainable method to transform pine needle waste into nitrogen-doped (N-doped) hydrochars. The primary focus is on evaluating these hydrochars as catalytic electrodes for the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR), which are pivotal processes with significant environmental implications. Hydrochars were synthesized by varying the parameters such as nitrogen loading, temperature, and residence time. These materials were then thoroughly characterized using diverse analytical techniques, including elemental analysis, density measurements, BET surface area analysis, and spectroscopies like Raman, FTIR, and XPS, along with optical and scanning electron microscopies. The subsequent electrochemical assessment involved preparing electrocatalytic inks by combining hydrochars with an anion exchange ionomer (AEI) to leverage their synergistic effects. To the best of our knowledge, there are no previous reports on catalytic electrodes that simultaneously incorporate both a hydrochar and AEI. Evaluation metrics such as current densities, onset and half-wave potentials, and Koutecky-Levich and Tafel plots provided insights into their electrocatalytic performances. Notably, hydrochars synthesized at 230 °C exhibited an onset potential of 0.92 V vs. RHE, marking the highest reported value for a hydrochar. They also facilitated the exchange of four electrons at 0.26 V vs. RHE in the ORR. Additionally, the CO2RR yielded valuable C2 products like acetaldehyde and acetate. These findings highlight the remarkable electrocatalytic activity of the optimized hydrochars, which could be attributed, at least in part, to their optimal porosity.

Multiobjective optimization of porous medium for efficient transpiration cooling of hypersonic vehicles using genetic algorithm

Transpiration cooling has been proven an effective method for reducing heat flux on the surfaces of high-speed vehicles. This study investigates the effects of porous medium properties, employing a black-box optimization method to determine the optimal length, thickness, and porosity for a porous medium in a transpiration cooling system on a flat plate under hypersonic laminar flow. The objectives include optimizing thermal effectiveness, coolant consumption, and the weight and cost of the porous material. A multiobjective genetic optimization algorithm is directly integrated with a Computational Fluid Dynamics (CFD) solver, and 1562 CFD simulations were conducted to identify the optimal configuration. The results demonstrate that the length and porosity of the porous medium more significantly impact thermal effectiveness than the thickness. Furthermore, the optimization identified a configuration for the porous medium that, when compared to the original case, shows reductions in length, thickness, and porosity of 3.5%, 11%, and 29%, respectively. Additionally, there were average improvements in thermal effectiveness and coolant consumption of 4.56% and 3.9%, respectively, while the weight and cost of the porous material increased by 3.73% and 3.65%, respectively.