Search Results (31)

The demand for high-performance supercapacitors has driven extensive research into novel electrode materials with superior electrochemical properties. This study explores the supercapacitive behavior of quaternary CuNiCoZnO (CNCZO) films engineered into a three-dimensional (3D) flower-like morphology and developed on versatile substrates, including carbon cloth, stainless steel mesh, and nickel foam. The unique structural design, comprising interconnected nanosheets, enhances the electroactive surface area, facilitates ion diffusion, and improves charge storage capability. The synergistic effect of the multi-metallic composition contributes to remarkable electrochemical characteristics, including high specific capacitance, excellent rate capability, and outstanding cycling stability. Furthermore, the influence of different substrates on the electrochemical performance is systematically investigated to optimize material–substrate interactions. Electrochemical evaluations reveal outstanding specific capacitance values of 2318.5 F/g, 1993.7 F/g, and 2741.3 F/g at 2 mA/cm² for CNCZO electrodes on stainless steel mesh, carbon cloth, and nickel foam, respectively, with capacitance retention of 77.3%, 95.7%, and 86.1% over 5000 cycles. Furthermore, a symmetric device of CNCZO@Ni exhibits a peak specific capacitance of 67.7 F/g at a current density of 4 mA/cm², a power density of 717.4 W/kg, and an energy density of 25.6 Wh/kg, maintaining 84.5% stability over 5000 cycles. The straightforward synthesis of CNCZO on multiple substrates presents a promising route for the development of flexible, high-performance energy storage devices. Full article

The preservation and continuous monitoring of cutting tools in a computer numerical control (CNC) machine is essential for ensuring seamless transitions in the manufacturing workflow, as well as maintaining adequate part quality. The implementation of tool condition monitoring (TCM) when milling can provide the user with necessary data regarding tool life, wear, and part quality. However, it is important to broaden the application of the TCM process across a much broader class of workpiece materials to understand the effects of material properties on the condition of the tool. The aim of this paper is to investigate the efficacy of tool condition monitoring techniques while milling low- and high-yield-strength materials across varied process parameters. A Fast Fourier Transform (FFT) analysis was conducted in this research. Vibration data were acquired from both uniaxial and triaxial accelerometers to investigate irregularities in vibrational amplitudes between new and worn milling tools. The experimental results show that there is a significant increase in vibrational amplitudes for the worn tool when compared to the new tool across various frequencies, which affirms the expected increase in vibrations and cutting forces at the tool–workpiece interface from using a worn tool. The F-values and p-values calculated using an F-test with a 95% confidence interval indicated statistically significant differences in vibration data between new and worn tools across various materials, including polyurethane foam, aluminum 6061, mild steel, and stainless steel, under different cutting conditions (low, medium, and high). These results further validate the findings obtained from the FFT analysis and highlight the effectiveness of vibration-based monitoring in distinguishing tool wear under varying material characteristics and machining conditions. Full article

Composite metal foam (CMF) is a new class of material based on a mixture of metal matrix composites and metal foams. While the mechanical properties of CMF are well studied, its thermal properties, particularly at extreme temperatures, are yet to be evaluated and established. This study investigates the specific heat capacity of stainless-steel composite metal foam at temperatures up to 1200 °C while comparing data obtained using the laser flash method and a differential scanning calorimetry method (DSC). Moreover, it outlines a detailed procedure for investigating the surface emissivity of composite metal foam (CMF) as a function of the emissivity of separate components (spheres and matrix). It uses experimental and analytical procedures to show how emissivity is directly affected by surface roughness, temperature, sphere curvature and viewing angles. The CMF used in this study consists of 316L stainless steel matrix and stainless-steel hollow spheres with varying sphere sizes. Full article

This paper proposes an innovative multi-material approach for introducing auxetic behaviour to syntactic foams (SFs). By carefully designing the size, shape, and orientation of the SFs, auxetic deformation behaviour was induced. Re-entrant hexagon-shaped SF elements were fabricated using expanded perlite (EP) particles and a plaster of Paris slurry first. Then, an auxetic pattern of these SF elements was arranged within a stainless-steel casting box. The empty spaces between the SF elements were filled with molten aluminium alloy (A356) using the counter-gravity infiltration casting technique. The cast auxetic composite had a bulk density of 1.52 g/cm³. The cast composite was then compressed under quasi-static loading to characterise its deformation behaviour and to determine the mechanical properties, especially the Poisson’s ratio. The cast composite deformation was auxetic with a Poisson’s ratio of −1.04. Finite Element (FE) simulations were conducted to understand the deformation mechanism better and provide means for further optimisation of the geometry. Full article

Microplastic contamination is a global concern due to its conspicuous presence in aquatic ecosystems and its toxic nature to environmental and human health. False mussels are among the most notable fresh- and brackish water invaders. The invasive Mytilopsis leucophaeata in Rodrigo de Freitas Lagoon-RFL (Rio de Janeiro, Brazil) is the most abundant macrofaunal invertebrate, widely established and distributed throughout the lagoon. This study aimed to assess microplastic contamination in this invasive filter feeder and evaluate its potential use as a bioindicator. Agglomerates (~100 mussels) were manually collected using a stainless-steel spatula in ten sampling areas distributed throughout the whole lagoon and kept frozen. In the laboratory, 60 individuals were sorted by area for soft-tissue digestion. Each pool of 10 soft-tissue mussels (n = 6 by area) was wet-weighted and then placed in a 150-mL decontaminated glass beaker with 50 mL of 10% KOH. Samples were heated (40 °C) for 48 h, and digested samples were filtered in glass-fiber membranes. Microplastics were found in all samples of mussels (n = 60) from RFL; the particles were mostly lower than 100 µm with a mean concentration (±SD) of 35.96 ± 47.64 MPs g wet-weight⁻¹. Microplastics were distinguished in seven shapes with different occurrences in samples (%): fiber (43.3%); fragment (34.3%); film (16.3%); sponge/foam (4.9%); pellet (0.57%), rope/filaments (0.17%); and undefined (0.4%). Thirteen colors of microplastics were found, but transparent (54.94%), black (10.77%), and white (9.36%) were the most common. Mytilopsis leucophaeata were useful to assess microplastic contamination in RFL and might be preferentially used in other invaded brackish systems instead of native and often threatened bivalves. Our results confirm the effective application of bivalves as an indicator of coastal microplastic pollution. Full article

The development of accurate methodologies for a thorough comprehension of the erosion phenomenon is a challenging and necessary task. This study entailed an exhaustive analysis, incorporating empirical data obtained from an experiment involving the impingement of a sand and water jet on a submerged stainless-steel plate and numerical simulations, employing the Oka Erosion model that was compilated in OpenFOAM. The primary focus of this study was to generate W-shaped profiles delineating the impingement zone, derived both from experimental observations and the developed numerical model. This comparative approach facilitated a robust evaluation of the model’s efficacy in replicating erosion patterns. The outcomes of this analysis revealed a concurrence between the experimental and simulated erosion contours, affirming the model’s proficiency in representing erosion phenomena. Nevertheless, a minor discrepancy was noted, characterized by a slight underestimation of erosion rate and thickness loss. Furthermore, the investigation unveiled a noteworthy time-dependent trend in mass loss from the experimental data denoting a pseudo stabilization of the erosion rate across the time. This research contributes to the refinement of erosion modeling parameters and underscores the nature of time-dependent erosion behavior, a pivotal consideration for optimizing material durability. Full article

As one of the most common forms of waste, waste PET is a serious pollutant in natural and human living environments. There is an urgent need to recycle PET. For this study, the complete degradation of PET was realized at a low temperature. A lipophilic hydrophobic membrane was formed on the surface of a stainless steel mesh (SSM) using a simple dip coating method, and an oil–water separation material was successfully prepared. After loading with degradation products, the surface roughness of SSM increased from 19.09 μm to 62.33 μm. The surface changed from hydrophilic to hydrophobic, and the water contact angle increased to 123°. The oil–water separation flux of the modified SSM was 9825 L/(m²·h), and the separation efficiency was 98.99%. The modified SSM had good reuse performance. This hydrophobic modification method can also be used to modify other porous substrates, such as activated carbon, filter paper, foam, and other materials. The porous substrate modified by the degradation product of waste PET was used to prepare oil–water separation materials, not only solving the problem of white pollution but also reducing the dependence on non-renewable resources in the conventional methods used for the preparation of oil–water separation materials. This study provides new raw materials and methods for the industrial production of oil–water separation materials, which have important application prospects. Full article

In the present work, a novel foam burner design is proposed and experimentally evaluated for operation with highly diluted syngas mixtures. The lab-scale burner consists of a purpose-built, square-shaped, high-temperature-grade stainless steel tubular reactor filled with square-sectioned siliconized silico carbide (SiSiC) foams. The assembly was installed in an electrical furnace. Spatially resolved temperature measurements were obtained along the reactor axis, while simultaneous measurements of CO, CO₂, H₂, O₂, and N₂ were taken at the burner exit and the water levels were recorded upstream and downstream of the reactor. The results clearly show that flames can be stabilized along the reactor for a range of foam characteristics and operating conditions. Hydrogen conversion efficiencies in excess of 98%, and overall thermal efficiencies close to 95% were achieved for the selected operating conditions. Overall, the denser 10 ppi foam demonstrated superior combustion characteristics in terms of stability, lower enthalpy rises, and a wider operating range at the expense of a very modest pressure drop penalty. Finally, scanning electron microscopy, coupled with energy dispersion spectroscopy (SEM/EDS) and Raman spectroscopy analyses, was used to determine the morphological and compositional characteristics of the pristine and aged foams. After more than 100 h of operation, no significant performance degradation was observed, even though the burner design was subjected to considerable thermal stress. Full article

In the last decade, plastic waste has become one of the main threats to marine ecosystems and their biodiversity due to its abundance and increased persistence. Microplastics can be classified as either primary, i.e., fabricated for commercial use, or secondary, i.e., resulting from the fragmentation/weathering processes of larger plastic pieces in the environment. In general, microplastics are detected in a number of aquatic organisms (e.g., fish, bivalves, mollusks, etc.) with alarming effects on their health. Therefore, the present work focuses on the detection and identification of microplastics in fish species (Dicentrarchus labrax, Sparus aurata) and mussels (Mytilus galloprovincialis) from aquaculture systems since these aquatic organisms are largely commercially available for consumption. In addition, seawater was also screened for the types of polymers present as well as their aging. The experimental protocol for biota samples contains a digestion step using Fenton’s reagent (0.05 M FeSO₄⋅7H₂O with 30% H₂O₂ at a volume ratio of 1:1) to remove organic material followed by filtration and a density separation step where the sample material was mixed with a saturated ZnCl₂ solution to separate microplastic particles from heavier material. For seawater samples (sampled by a microplastic net sampler), only sieving on stainless steel sieves followed by filtration on silica filters was applied. Detection of microplastics and identification of their polymeric composition was achieved through the combined use of micro-Raman analysis, Attenuated Total Reflectance–Fourier Transform Infrared spectroscopy, and Scanning Electron Microscopy in tandem with Energy Dispersive X-ray spectroscopy. Microplastic abundance was 16 ± 1.7 items/individual in mussels and 22 ± 2.1 items/individual in sea bass, and 40 ± 3.9 items/individual in sea bream, with polyethylene (74.4%) being the most detected polymer type, while polyethylene-co-vinyl acetate (65%), polyvinyl-butyral (36.8%), polyvinyl alcohol (20%), and polybutyl methacrylate (15.8%) were also detected to a lesser extent. The microplastics isolated from seawater samples were films (30%), fragments (30%), and fibers (20%), while some of them were derived from foams (20%). Also, in most of these seawater-recovered microplastics, a relatively high degree of oxidation (carbonyl index > 0.31) was observed, which was further confirmed by the results of Energy Dispersive X-ray spectroscopy. Finally, the Scanning Electron Microscopy images showed various morphological characteristics (cracks, cavities, and burrs) on the surfaces of the microplastics, which were attributed to environmental exposure. Full article

Compared with high-pressure water and reagent washing decontamination, foam decontamination has a promising application due to its ability to significantly reduce the volume of radioactive waste liquids and effectively decontaminate the inner surface of the pipes, the interior of the large cavities, and the vertical walls. However, the foam is less stable, leading to a low decontamination rate. Currently, three main types of stabilizers with different stabilizing mechanisms, namely nanoparticles, polymers, and cosurfactants, are used to improve foam stability and thus increase the decontamination rate. Nanosilica (NS), xanthan gum (XG), and n-tetradecanol (TD) were used as typical representatives of nanoparticles, polymers, and cosurfactants, respectively, to improve the stability of the foam detergent with pH < 2 and chelating agents. The differences in the effects of these three types of stabilizers on foam properties were investigated. Although NS, XG, and TD all increase the half-life of the foam from 7.2 min to about 40 min, the concentration of TD is much lower than that of NS and XG in the foaming solution, and TD foaming solution has the highest foaming ratio. Moreover, TD can markedly lower the surface tension, resulting in a significant reduction of the wetting contact angle on the surfaces of glass, ceramic tile, stainless steel, and paint, while NS and XG cannot signally change the surface tension and have no obvious effect on the wetting contact angle. At low shear rates, TD can increase the apparent viscosity of foam by two orders of magnitude, and the wall-hanging time of the foam on the vertical wall is more than 30 min. In contrast, NS and XG cause a limited increase in the apparent viscosity of the foam, and the wall-hanging times are both less than 5 min. In addition, TD foaming solution has excellent storage stability, and the storage time has no obvious effect on the performance of the foam. And after only three days of storage, NS undergoes severe agglomeration and precipitation in the foaming solution, resulting in a complete loss of the stabilizing effect. After 90 days of storage, the half-life of XG foam decreases by 26%. For simulated radioactive uranium contamination on both horizontal and vertical surfaces, TD can significantly improve the decontamination rate, especially for vertical surfaces, where TD can increase the single decontamination rate by more than 50%. Full article

Green hydrogen production seems to be the best route to achieve a sustainable alternative to fossil fuels, as hydrogen has the highest energy density on a mass basis and its combustion does not produce greenhouse gases. Water electrolysis is the method of choice for producing green hydrogen. Among commercially available water electrolysis systems, alkaline water electrolysis (AWE) is the most well-established technology, which, nevertheless, still needs to improve its efficiency. Since the electrodes’ performance is of utmost importance for electrolysis efficiency, nickel foam (NF) and stainless steel foam (SSF) electrodes were analyzed via voltammetry to validate their catalytic activity toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 30 wt.% NaOH electrolyte solution. Moreover, at a current density of 50 mA cm⁻², the NF and the SSF exhibited good stability, with the potential for HER and OER stabilizing at −0.5 V and 1.6 V vs. reversible hydrogen electrode. A lab-scale electrolyzer attained current densities of 10, 20, and 50 mA cm⁻² at small cell voltages of 1.70 V, 1.80 V, and 1.95 V. The results validated NF and SSF as electrodes for a high-performance AWE electrolyzer, especially at higher temperatures. They ensured the progress for the project’s next stage, i.e., constructing an electrolyzer at a pilot scale. Full article

The effect of porosity and pore size on the quasi-static compression properties and energy absorption characteristics of the steel foam was investigated in this paper. The 316L steel foams were prepared through powder metallurgy using urea as the space holder. The macrostructure of steel foam and microstructure of the pore walls were characterized, and the quasi-static compression experiments were conducted on the specimens in the axial direction at a strain rate of 10⁻³ s⁻¹. The results show that the increase in porosity decreases the yield strength and plastic modulus of the steel foam but increases the densification strain of the steel foam. The yield strength of the steel foam decreases significantly when the pore size is 2.37 mm. However, the pore size has little effect on the plastic modulus. Moreover, the energy absorption per volume of the steel foam decreases with increasing porosity at the same strain. The effect of porosity on energy absorption efficiency is greater than that of pore size. Full article

In the food industry, the surfaces of processing equipment are considered to be major factors in the risk of food contamination. The cleaning process of solid surfaces is essential, but it requires a significant amount of water and chemicals. Herein, we report the use of foam flows based on alkyl polyglucosides (APGs) to remove spores of Bacillus subtilis on stainless-steel surfaces as the model-contaminated surface. Sodium dodecyl sulfate (SDS) was also studied as an anionic surfactant. Foams were characterized during flows by measuring the foam stability and the bubble size. The efficiency of spores’ removal was assessed by enumerations. We showed that foams based on APGs could remove efficiently the spores from the surfaces, but slightly less than foams based on SDS due to an effect of SDS itself on spores removal. The destabilization of the foams at the end of the process and the recovery of surfactant solutions were also evaluated by using filtration. Following a life cycle assessment (LCA) approach, we evaluated the impact of the foam flow on the global environmental footprint of the process. We showed significant environmental impact benefits with a reduction in water and energy consumption for foam cleaning. APGs are a good choice as surfactants as they decrease further the environmental impacts. Full article

At present, microplastics (MPs) pollution has attracted people’s attention, and MPs in seawater have caused great harm to the marine environment. Taking Yugang Park Beach (YPB) in Zhanjiang Bay (ZJB) as the research object, we studied the spatial and temporal distribution, composition, and inventory of MPs in the bathing seawater affected by the ebb tide by filtering the bathing seawater with a 45 μm stainless steel sieve. The results showed that the average abundance of MPs in the bathing seawater was 201.3 ± 183.0 items·m⁻³, with the highest at mid-tide, followed by high and low tides. The size of MPs in the bathing seawater was mainly 1–2 mm, with most being white (23.5%) and green (29.8%) MPs, and the largest proportion being foam (27.5%) and fiber (29.5%). The main polymer types were polypropylene (PP), polystyrene (PS), and cellulose (CE). Correlation analysis between MP abundance and their sizes showed that the abundance of 0.33–5 mm MPs was significantly and positively correlated with their sizes (p < 0.05). The average MP inventory was 3.2 × 10⁶ items, with the largest at high tide, followed by mid and low tides. In conclusion, these results highlighted that tidal variations were the main factor causing the uneven distribution of MPs in the bathing seawater at YPB. This study provides theoretical support for future study of MP pollution in bathing waters, and the effect of tidal variations on MPs. Full article

In order to prepare stainless steel foams (SSFs) with high specific strength, cost-effective performance, and multiple relative density ranges, this work used CaCl₂ as a space holder to prepare 304 and 430 SSF samples with different relative densities using the powder metallurgy method. The microstructure and the properties were compared and analyzed by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and a universal testing machine. The results show that the matrix of 304 SSFs is austenite and 430 is ferrite. In the quasi-static compression test, when the relative density was in the range of 0.33~0.12, their compressive strength increased with the relative density increasing; the maximum compressive strength of 304 SSFs reached 40.29 MPa and that of 430 SSFs was 49.79 MPa. While the compressive strength of 430 SSFs is significantly higher than 304 SSFs at a similar relative density, 304 SSFs show better stability in the plastic deformation stage. When the deformation reached densification, the maximum energy absorption value of 304 SSFs reached 15.94 MJ/m³, while 430 SSFs was 22.70 MJ/m³. The energy absorption value increased with the relative density increasing, and 430 SSFs exhibited a higher energy absorption capacity than 304 SSFs. Full article