Search Results (784)

Alkaline water electrolysis (AWE) is a promising technology for sustainable hydrogen production, although its performance is limited by electrode overpotential, interfacial charge-transfer resistance, and limited electrochemically accessible surface area. In this study, a monolayer ternary carbon nanomaterial (CNM) composite comprising reduced graphene oxide (rGO), carbon nanotubes (CNTs), and Vulcan XC-72 was fabricated on stainless steel (SS) using a hybrid polyvinyl alcohol–polytetrafluoroethylene (PVA–PTFE) binder. Thermal treatment generated a porous conductive network that enhanced electrolyte accessibility and electron transport. Electrochemical characterization in 0.12 M NaOH showed that the CNM-modified electrode exhibited substantially higher current response and CV-derived double-layer capacitance (C_dl) of 62.61–78.51 mF/cm², compared with 3.43–3.74 mF/cm² for bare SS. Electrochemical fitting further showed markedly higher exchange-current density (i₀) parameters for the modified electrode, along with a reduced solution resistance (Rs) of ~2.1–2.2 Ω·cm² and a lower Rct. The oxyhydrogen (HHO) production rate reached 0.304 mL/min at 3.8 V, compared with 0.262 mL/min for bare SS at 4.0 V. Repeated HHO measurements showed ~2% variation (n = 3), indicating good reproducibility of the gas-production response. These results demonstrate that the rGO/CNT/XC-72 composite provides an effective and reproducible surface-engineering approach for enhancing electrochemical performance and HHO production in alkaline electrolysis systems. Full article

The design of efficient small-scale hydrogen energy storage systems requires balancing hydrogen production rate, electrical efficiency, and system simplicity. This study experimentally investigates the energetic compromise imposed by separator material and electrolyzer architecture through a comparative analysis of finite-gap alkaline, finite-gap acidic, and zero-gap proton exchange membrane (PEM) electrolyzers. Zirfon^® Pearl 500 (Agfa, Mortsel, Belgium) diaphragms were employed in alkaline electrolysis using 25 wt.% KOH, whereas Nafion™ 117 (Chemours, Wilmington, DE, USA) membranes were used in both finite-gap acidic electrolysis (2.55 M H₂SO₄) and a commercial five-cell zero-gap PEM electrolyzer supplied with deionized water. Electrochemical performance was evaluated in terms of polarization behavior, apparent resistance, hydrogen production rate, Faradaic efficiency, and energy conversion efficiency. The zero-gap PEM architecture exhibited the best electrochemical performance, with an apparent resistance of only 0.138 Ω per cell, corresponding to reductions of approximately 43-, 51-, and 64-fold compared with the finite-gap PEM, stainless steel/Zirfon alkaline, and nickel/Zirfon alkaline configurations, respectively. The zero-gap electrolyzer delivered currents from 1.53 to 10.0 A while operating below 2.8 V, demonstrating the benefit of minimizing the ionic transport path. In contrast, the finite-gap acidic configuration achieved higher hydrogen production rates than the alkaline system owing to the superior proton conductivity of Nafion™ 117, whereas the alkaline Ni/Zirfon configuration reached the highest Faradaic efficiency (≈98%) and energy conversion efficiency (≈36%) because of improved gas separation and reduced hydrogen crossover. Electrochemical impedance spectroscopy further revealed that the normalized ohmic resistance of the zero-gap PEM cell was only 0.029 Ω, with charge-transfer processes accounting for approximately 96.2% of the total impedance. These results demonstrate that separator properties and cell architecture govern the trade-off between reaction kinetics and energy efficiency, providing practical guidelines for selecting electrolyzer configurations dedicated to decentralized and small-scale hydrogen energy storage. Full article

Introduction: In modern vehicles, new enhancements are being sought for engine components, break disks, and valves, using light-weight materials which are applicable not only in conventional cars but also in electric vehicles. The utilization of novel additive manufacturing aims to reduce energy loss and mechanical stress, improving component longevity at a lower cost. Method: The effective hardfacing of silicon carbide (SiC) over stainless steel was achieved using a Rofin Sinar Nd:YAG 2 kW robotized laser system with powder feedstock. Different Metal Matrix Composites (MMCs) were manufactured using Laser Directed Energy Deposition (DED-LB), making it possible to additively manufacture near-net-shaped parts while having the freedom to obtain variable geometries for the surface layout. Samples were prepared from the following flat products of EN 10088: X2CrTi12(1.4512, AISI 409), X15CrNi25-20 (1.4840, AISI 310), X5CrNi18-10 (1.4301, AISI 304), and X1CrNiMoCuN20-18-7 (1.4547, UNS: S31254). The reinforcement comprised a fine carbide powder of SiC, and the MMCs were produced after the solidification of the molten mixture. The study included an assessment of the interface zones and measurement of their microhardness, as well as microstructural analysis with visual defect evaluation focused on porosity and microcracking detection. Results: In order to increase durability and heat and wear resistance, advanced MMC sample components for various vehicles applications were explored. In one layer with a thickness of 1.5 mm, composed of X1NiCrMoCuN20-18-7 and SiC, the hardness characteristic was observed to be about 25 MPA higher than that experimentally obtained for the base material. For the same MMC, the carbide–metal interface zones were investigated. No cracks were observed, and it displayed a porosity of ≈1.57%. DED-LB MMCs possess excellent thermal stability and resistance to abrasion. Conclusion: Laser application allows various geometric applications on the surfaces of car parts. The appropriate selection of component phases can enable the design of parts with specific functionality, where the interaction between the microstructure and properties is complex. Full article

This study compared the volatile organic compound (VOC) profiles and their relationships with microbial genera in Spanish-style table olives fermented in an interconnected under-vacuum stainless-steel system (F) and in traditional independent fiberglass vessels (G). VOCs were analyzed by HS-SPME-GC-MS, and microbial communities were characterized by metataxonomic analysis. A total of 97 VOCs were identified, mainly alcohols (29), esters (21), carbonyls (20), hydrocarbons (5), phenols (4), and terpenes (6). Among the most abundant compounds were 4-ethylphenol, ethanol, (Z)-3-hexen-1-ol, phenylethyl alcohol, ethyl acetate, and isobutanol. Only five VOCs—decanal, methyl ethyl ether, linalool, 2-methylbutanoic acid, and ethyl lactate—showed no significant variation with fermentation system or time, suggesting formation during debittering or early fermentation. The fermentation system strongly influenced volatile development, with 16 VOCs unique to F, 15 unique to G, and 66 shared. Among shared compounds, 48 differed significantly between systems, and 43 changed during fermentation. The F system was associated with a more restricted VOC profile, whereas G generated a more diverse volatile profile. Microbial–VOC relationships also differed: Leuconostoc, Lactiplantibacillus, Candida, and Dekkera were mainly associated with F-system VOCs, whereas less common bacterial genera and fewer fungi characterized G. Overall, the interconnected under-vacuum system is suitable for standardized production, while the traditional system favors greater microbial and volatile complexity. Full article

The rapid transition toward electrified mobility and climate neutrality has prioritized the structural and environmental optimization of battery electric vehicle (BEV) subsystems. While vehicle lightweighting enhances operational efficiency, the production phase of structural enclosures and battery cells frequently introduces severe environmental and economic impacts and supply chain vulnerabilities. This study presents a comprehensive cradle-to-gate environmental life cycle assessment (LCA), life cycle costing (LCC), and semi-quantitative social assessment of alternative battery housing materials and battery cell architectures. To achieve a functionally accurate comparison, alternative materials, including a novel recyclable thermoplastic acrylic sheet molding compound (SMC), commercial thermoset SMCs, aluminum (AlMg₃), and stainless steel, are evaluated using an analytical stiffness- and strength-equivalent methodology across three real-world geometric demonstrators. Simultaneously, lithium iron phosphate (LFP) liquid electrolyte prismatic cells and solid-state polymer pouch cells are assessed. Material-level results indicate that, while aluminum minimizes the structural mass, primary aluminum manufacturing exhibits the highest global warming potential and processing costs. Conversely, Polytec SMC and Elium SMC achieve the lowest environmental impacts alongside competitive total production costs. At the cell level, prismatic LFP architectures display superior environmental performance compared to solid-state pouch cells, which suffer from energy-intensive processing and lower volumetric capacity normalization. Demonstrator-level aggregation reveals that the electrochemical cells heavily dominate the environmental and economic footprint of the complete assembly, with the housing accounting for less than 5% of the total global warming potential (GWP) and 1% of the total costs. The social assessment reveals moderate and comparable performance across all systems, with slight advantages for thermoplastic composite-based configurations in terms of circularity potential and innovation perception. Overall, the study highlights the critical importance of the cell architecture and manufacturing processes in determining battery system sustainability, while demonstrating the relevance of lightweight composite housings in reducing the structural mass with a minimal environmental penalty. Full article

Background: ExPEC9V was a 9-valent vaccine candidate intended for the prevention of invasive extraintestinal pathogenic Escherichia coli (ExPEC) disease (IED). Here, we describe more than a decade-long formulation development trajectory of this vaccine candidate aimed at establishing a stable, robust and scalable drug product that maintains long-term stability while addressing potential manufacturing challenges and increasing the probability of successful global deployment. Methods: Selected formulation development studies of the ExPEC multivalent vaccine candidate are summarized, spanning formulation screening, confirmation, and design of experiments (DoE)-based robustness, stability and compatibility studies. A formulation initially developed for an early low-valency vaccine candidate was subsequently tested and confirmed for candidates with additional serotypes incorporated based on antigen heterogeneity evidence. Contact materials employed included primary packaging—polycarbonate (PC) and polyethylene terephthalate glycol (PETG) bottles, borosilicate glass vials, stoppers, and prefilled syringes; vessel types—bags and stainless steel vessels used in drug substance (DS) and drug product (DP) manufacturing; and varying concentrations of tungsten and hydrogen peroxide. An evolving analytical panel was applied to assess attributes such as purity, protein concentration and degree of O-acetylation. Results: A phosphate-based formulation containing sorbitol, methionine, and polysorbate 80 showed superior stability in screening and was confirmed as fit for purpose across increasing vaccine valency. The ExPEC 9V drug product displayed remarkable thermal and formulation robustness, long-term (3 years) stability at 2–8 °C in glass vials and prefilled syringes, and compatibility with assessed primary containers and manufacturing materials. DoE-based robustness studies defined acceptable excipient and pH ranges, supporting a wide formulation design space. Conclusions: The development trajectory of the ExPEC9V vaccine candidate demonstrates that early prioritization of a robust, scalable formulation that remains fit for purpose across valency evolution supports a stable late-stage manufacturable drug product. Full article

Chromo-magnesian ore materials constitute a complex resource base for producing both metallurgical and chemical products, yet existing research remains fragmented across beneficiation, smelting, chemical extraction, waste valorization, and refractory applications. This systematic review, conducted according to PRISMA 2020 using Scopus, Web of Science Core Collection, and SpringerLink, evaluates processing routes based on feedstock type and product orientation. Of 625 identified records, 19 studies met the final inclusion criteria. The reviewed technologies were classified into four groups: chemical processing, metallurgical reduction and smelting, integrated beneficiation–chemical–metallurgical routes, and refractory/materials production. Primary chromite ores and concentrates are predominantly used for ferrochrome and stainless-steel alloy production, whereas tailings, slimes, overburden, and serpentine-bearing materials are mainly processed into chromium oxide, magnesium compounds, and silica-rich products. Integrated routes show the greatest potential for low-grade and technogenic materials through multi-product recovery and improved resource efficiency. However, route selection depends on feedstock quality, mineralogy, target products, and process intensity. Major research gaps include limited comparative studies, insufficient mineralogy-driven process design, and inadequate techno-economic and environmental evaluation. Overall, future development should focus on integrated, feed-specific processing strategies that maximize resource utilization. Full article

Additive manufacturing (AM) of stainless steel has been gaining industry attention in recent years due to the need to manufacture complex steel components. Many sectors stand to benefit from the design flexibility, customization, and rapid production capabilities of AM. However, the industry’s adoption of this technology remains limited due to concerns about the mechanical integrity and reliability of AM products. This experimental study examines the wear and tribological behavior of Wire Arc Additive Manufactured (WAAM) austenitic stainless steel 316L. Pin-on-disk tests were conducted using a 5 mm tungsten carbide ball under dry sliding conditions at normal loads of 1.5 and 2.5 N and sliding speeds between 0.03 and 0.229 m/s. The results showed that the coefficient of friction remained relatively stable at approximately 0.6, while wear volume generally decreased with increasing sliding speed. Lower normal loads resulted in lower wear volume, whereas the wear factor showed only limited sensitivity to the applied load. Optical microscopy revealed a ferrite–austenite microstructure with residual δ-ferrite that contributes to the observed wear behavior. These findings demonstrate the suitability of WAAM-produced 316L stainless steel for tribological applications requiring stable frictional performance. Full article

With contemporary advancements in additive manufacturing (AM), it has become possible to obtain hull structures for spacecraft made of relatively cheap materials. The possibility of substituting super-austenitic stainless steel Avesta SMO 254 X1NiCrMoCuN20-18-7 (EN 10088) for that already used in the Starship SpaceX 304 L-Modified is focused on achieving better thermal stability and durability in extreme conditions. The Directed Energy Deposition Arc (DED-Arc) method for AM has enabled the production of high-strength-to-weight ratios. The aim is to engage low-cost material with treatment optimization to provide greater corrosion resistance and high yield and tensile strength. For the DED-Arc, a filler wire was selected for the welding source, Fronius TPS 400i. A simulation via the RoboDK Robot Development Kit for the FANUC ARC Mate 100ID10L is provided. Additional shot pining/vibration treatment is proposed for the finished structure, which can be a substitute for the cold-worked initial metal. A comparison is made for stainless steel that has already been tested for space travel. Regimes for the manufacturing process are proposed, with representative samples of Avesta SMO 254 obtained and tested using microhardness measurements, microcracking detection, porosity measurements, interface zone assessment, and microstructural analysis. The DED-Arc process can be applied to large-space shell manufacturing. A comparison is made with a focus on the mechanical and corrosion advantages. For Avesta SMO 254, microhardness measurements ranged from 235 to 246 HV1 and increased after treatment. The controlled parameters provided a maximum heat input of 0.7 KJ/mm, no defects, and a fine microstructure. The successful use of stainless steel with AM increases the potential for multiple space missions. The advanced method shows high quality, allows cost savings and provides extended service life. Full article

AISI 316L stainless steel (316L SS) exhibits inadequate corrosion resistance in chloride-containing soils. Fe-based amorphous coatings (Fe-ACs), owing to their high Cr, Mo, and W contents and defect-free amorphous structure, are promising candidates for superior protection. In this work, the corrosion behavior of 316L SS and an Fe-based amorphous coating (Fe-AC) fabricated by high-velocity oxygen-fuel (HVOF) spraying was systematically compared by burial in Daqing saline soil (25% water content) with 0, 1.0, and 2.0 wt.% NaCl for 15–55 days. Corrosion rates were measured via mass loss, and surface morphology, elemental distribution, and phase constitution were characterized using OM, SEM/EDS, and XRD. Electrochemical impedance spectroscopy and potentiodynamic polarization were employed to assess passive-film stability and charge-transfer resistance. The Fe-AC consistently exhibited an extremely low corrosion rate (below 0.01 mm y⁻¹), nearly independent of NaCl concentration and exposure time, with only sporadic rust spots and the formation of a compact Cr/Mo/W-enriched passive film. In contrast, after 55 days in soil containing 2.0 wt.% NaCl, the 316L SS showed a corrosion rate of 0.0562 mm y⁻¹—six times that of the Fe-AC—accompanied by severe pitting (pit depth up to 3.6 mm) and loose corrosion products (γ-FeOOH and α-Fe₂O₃). Electrochemical tests confirmed that the charge-transfer resistance of the Fe-AC under the 0% NaCl condition reached 1.16 × 10⁶ Ω cm² and its breakdown potential exceeded 1.12 V, far outperforming 316L SS (2.30 × 10³ Ω cm² and 0.22 V, respectively). The novelty of this study lies in the systematic evaluation of the buried corrosion performance of HVOF-sprayed Fe-based amorphous coatings versus 316L SS in an actual saline soil and in elucidating the synergistic passivation mechanism of Cr, Mo, and W. This passive film effectively impedes chloride ingress and maintains high impedance over extended periods. Full article

This paper studies the effect of welding heat input on microstructure and low-temperature toughness of laser-arc hybrid welded (LAHW) SAF2507 super-duplex stainless-steel (SDSS) joints. Heat input was adjusted from 0.204 to 0.407 kJ/mm by changing the welding speed. Results indicate that low heat input brings high ferrite content and low impact toughness. The medium heat input generates a balanced two-phase microstructure and gains the highest impact energy of 36.0 J at −46 °C. Excessively high heat input results in obvious grain coarsening and degraded impact performance. This study offers an experimental basis and parameter reference for practical welding production. Full article

This study examines the influence of powder characteristics and laser powder bed fusion (LPBF) processing parameters on the microstructure and mechanical performance of ASTM F139 stainless steel fabricated from powders supplied by two manufacturers. Feedstock powders were characterized with respect to chemical composition, particle size distribution, morphology, density, and flowability. Cubic and tensile specimens were produced using different combinations of laser power, scan speed, hatch spacing, and scanning strategy. The fabricated components were evaluated by density and porosity measurements, surface roughness analysis, optical and electron microscopy, hardness testing, and tensile characterization in both horizontal and vertical build orientations. Powder flowability and packing density were found to strongly influence consolidation behaviour, with improved flow characteristics promoting higher densification and reduced porosity. Scanning strategy also affected defect formation, and a 67° interlayer rotation produced lower porosity than the conventional 0°/90° pattern. An optimal processing window was identified at a laser power of 212 W, scan speed of 1600 mm s⁻¹, hatch spacing of 0.07 mm, and layer thickness of 30 μm, yielding components with ~1% porosity, surface roughness below 15 μm, and a density of 7.65 g cm⁻³ (>95% of the theoretical density). Under these conditions, horizontally built specimens exhibited an ultimate tensile strength of 612 ± 43 MPa and a yield strength of 544 ± 37 MPa, exceeding the corresponding values obtained for vertically built specimens. Microstructural characterization revealed a refined cellular austenitic structure associated with epitaxial grain growth during solidification, while fractographic analysis indicated predominantly ductile failure through microvoid coalescence. The results establish clear process–structure–property relationships in LPBF-fabricated ASTM F139 stainless steel and demonstrate that the combined optimization of powder quality, scan strategy, and energy input enables the production of near-full-density components. Full article

The optimization and the engineering development of additive manufacturing (AM) products both require accurate, non-destructive techniques to extract their mechanical performances. The Instrumented Indentation Test (IIT) has such a potential, although it currently lacks standard procedures that are suitable for analyzing materials which are affected by internal residual stress (RS). Additionally, nanoindentation testing suffers from the presence of indentation size effects (ISE), which hamper the possibility of correlating the measured mechanical performance at different indentation depths or peak loads using the standard indentation hardness (H_IT) and modulus (E_IT). This paper presents a novel IIT methodology that is based on new indentation parameters, namely the loading stiffness rate (LSR) and the rate-derived hardness (H_R), which are then used to assign the desired mechanical performances of an L-PBF 316L austenitic stainless-steel alloy obtained via multiload/multiscale IIT strategy. The mean values of LSR, H_R, H_IT, and E_IT on the macroscale were 57.3 ± 1.4 GPa, 2.33 ± 0.059 GPa, 2.41 ± 0.13 GPa, and 201 ± 7.8 GPa, respectively, whereas on the nanoscale they were 56.1 ± 5.1 GPa, 2.30 ± 0.21 GPa, 3.00 ± 0.36 GPa, and 219 ± 24 GPa, respectively. Unlike the standard H_IT, the new indentation parameters of the nano- and macro-IITs are within the standard deviation, proving their ISE-free property. The obtained E_IT was slightly higher than the reference Young’s modulus (~190 GPa) of the 316L stainless steel. The loading secant stiffness versus depth plot can be used to assess the susceptibility of RS to relax during indentation, which is an important performance factor for the engineering design of AM components. The successful correlation that has been found between electron backscatter diffraction (EBSD) analysis (in terms of crystal anisotropy, grain size, and dislocation density) and nanoindentation testing at three subregions of the core zone of the investigated deposit confirms the validity of the proposed methodology. The proposed methodology is a step towards the full determination of the three Ps, that is, process, properties, and performance of advanced AM products. Full article

6061 aluminum alloy is lightweight and has good thermal conductivity, while 304 stainless steel possesses excellent mechanical properties and corrosion resistance; both have broad application prospects in cooling circuits. Propylene glycol coolant shows great potential in liquid cooling systems due to its low toxicity and good antifreeze properties. However, during operation, galvanic corrosion may occur when the two metals come into direct contact within the coolant, thereby threatening system safety and service life. This study focuses on 6061 aluminum alloy, 304 stainless steel, and their galvanic couples. Electrochemical testing, SEM, 3D confocal microscopy, and XPS were used to systematically investigate their self-corrosion and galvanic corrosion behavior in propylene glycol coolant at pH values of 4.8, 6.8, and 8.8. The results indicate that 6061 aluminum alloy is more sensitive to pH changes; its corrosion resistance first increases and then decreases as pH rises, with the least corrosion occurring at pH = 6.8 and the most severe at pH = 4.8. 304 stainless steel exhibited lower corrosion rates at pH 6.8 and 8.8, but corrosion significantly worsened at pH 4.8. For the 6061 aluminum alloy/304 stainless steel couple, the galvanic current first decreased and then increased with rising pH, while the galvanic potential first increased and then decreased. The 6061 aluminum alloy consistently acted as the anode, and the 304 stainless steel consistently acted as the cathode, with the highest sensitivity to galvanic corrosion observed at pH 4.8. XPS analysis shows that under different pH conditions, the corrosion products of 6061 aluminum alloy are Al(OH)₃ and Al₂O₃, while the main components of the passivation film on 304 stainless steel remain unchanged. Full article

The corrosion behavior of ferritic–martensitic 17Cr stainless steel in CO₂-saturated brine was investigated using static autoclave immersion tests in 4.12 wt% NaCl solution at 230 °C under CO₂ partial pressures of 6.36, 18.28, and 24.57 MPa. The calculated in situ pH values obtained using the OLI System were 3.79, 3.55, and 3.49, respectively. Corrosion morphology, microstructural evolution, and corrosion products were characterized by SEM, EDS, EBSD, and Raman spectroscopy. The average mass-loss corrosion rate increased from 0.138 ± 0.0221 mm/year at 6.36 MPa pCO₂ to 0.326 ± 0.0142 mm/year at 24.57 MPa pCO₂. Although the specimens did not show severe macroscopic pitting, localized attack preferentially occurred in fine-grained martensitic banded regions. EBSD analysis revealed that these regions exhibited higher local misorientation and defect density, which may reduce the stability of Cr-rich surface films. Raman spectra identified Cr(OH)₃ in the corrosion products, and the Cr(OH)₃ signal became more evident with increasing CO₂ partial pressure. The results indicate that, under fixed temperature and salinity, the corrosion behavior of 17Cr stainless steel is governed by CO₂ partial pressure and microstructural heterogeneity. Full article