Fluoride contamination in drinking water is a global challenge due to its adverse health effects, including dental and skeletal fluorosis. The limitations of conventional removal methods, such as chemical precipitation and ion exchange, drive the search for sustainable and low-cost adsorbents. Coffee grounds, an abundant agro-industrial residue rich in carbon, show great potential as a precursor for activated carbon. Surface modification with citric acid, including its natural source from lemon juice, can significantly enhance adsorption capacity and provide a low-cost process accessible to rural communities, thereby promoting self-sufficiency in safe water treatment locally.

In this study, activated carbons derived from coffee grounds were prepared under different activation conditions (non-activated, CO₂-activated, and H₃PO₄-activated) and subsequently impregnated with citric acid or lemon extract. Adsorption experiments using sodium fluoride solutions were conducted to evaluate performance. CO₂-activated carbon impregnated with citric acid exhibited the highest adsorption capacity, reaching 0.16 mg g⁻¹ after 6 hours of contact.

The results demonstrate that agro-industrial residues, when converted into functional adsorbents, can provide viable, sustainable, and low-cost alternatives for fluoride removal in drinking water. This innovative approach reinforces the role of circular economy strategies and technological innovation in decentralized sanitation, particularly in vulnerable rural communities lacking access to conventional solutions.

Sachet water has been identified in recent years as the most common means of water packaging in West Africa, particularly Ghana. The water is packaged in 500ml heat-sealed Low-Density Polyethylene (LDPE) plastic bags, popularly known in the streets as “pure water” and is considered safe and hygienic for consumption. Sachet water after being consumed, however, is not properly disposed of, causing adverse environmental issues.

This study talks about the effect of improper disposal of the plastic packaging material, with the aim of combining the waste water sachet with pineapple leaf fibres to produce a composite material. The procedure through which the raw materials were obtained and how the composite was made are stated. Impact and breakdown voltage tests were performed on the material obtained, and the results were evaluated. The impact test results showed a decrease in impact strength as the fibre content was increased. This was attributed to the incomplete bond or adherence of the matrix to the fibre. The results obtained for the breakdown voltage test also showed an overall decrease in breakdown voltage values as compared to the value obtained for pure LDPE. Specimens with 15% fibre content had the highest value among the samples containing fibres. The values obtained were attributed to the presence of voids in the composite material.

Environmental pollution has emerged as a critical global concern due to the release of pollutants from industries, agricultural fields, and other human activities, requiring urgent attention and sustainable solutions. Metal–Organic Frameworks (MOFs) are porous materials consisting of organic ligands and inorganic metal ions or clusters. They have been introduced as a promising class of material for environmental remediation. Their variable pore size, large surface area, and diverse structural and functional properties make them suitable for environmental applications. Water purification through the removal of heavy metals, dyes, toxins, and organic pollutants have been achieved through these materials. The removal of harmful gases (carbon dioxide, sulphur dioxide, ammonia) from the environment is another important application of MOFs. This paper gives a critical insight into the mechanistic pathways of MOFs in adsorption, photocatalysis, redox-mediated degradation, and ion-exchange processes used for the removal of pollutants. The structural features of MOFs influence contaminant capture, selectivity, and degradation kinetics. Recent studies employing in situ spectroscopy, computational modeling, and kinetic analysis have unraveled the interaction dynamics between MOFs and pollutants. By bridging structural attributes with mechanistic functions, this paper will be helpful in the further exploration of MOFs, with potential to restore the environment.

The transition to sustainable manufacturing is driving the increased use of recycled aluminium alloys. However, the variability of residual elements such as Mg, Fe, or Mn poses challenges for achieving reliable microstructural control and mechanical performance. This study investigated the influence of Mg and Mn content on the microstructure and properties of recycled Al-Si alloys. Alloys with varying Mg concentrations (0.2 to 0.5 wt.%) and Mn additions (0.07 to 0.54 wt.‰), representative of recycled feedstock compositions, were prepared by casting. Microstructure analysis revealed that increasing Mg promoted Mg₂Si formation, and also modified the morphology and distribution of intermetallic phases. Mechanical testing showed that increasing Mg from 0.2 to 0.5 wt.% enhanced strength through precipitation and solid solution strengthening while reducing ductility; the yield strength increased from 156 to 250 MPa and the ultimate tensile strength from 242 to 296 MPa, whereas ductility decreased from 7.8 to 2.9 %. Addition of 0.54 wt.‰ Mn did not show a significant effect on strength or ductility in the compositions evaluated. The results highlight the critical role of Mg in recycled aluminium alloys, demonstrating both its strengthening potential and its risk of embrittlement as a function of its composition. The findings provide a pathway for alloy design and process optimisation to enable high-value use of recycled Al alloys in structural applications, supporting a more sustainable circular economy in the aluminium sector.

The use of reclaimed asphalt pavement (RAP) in hot-mix asphalt (HMA) has grown as transportation agencies seek to reduce costs and limit landfill waste. Working with RAP allows for the reuse of the aggregate and its asphalt coating, reducing waste. The asphalt coating needed for HMA is largely found on the finer aggregates, resulting in a dominantly finer graded mixture, reducing its compressive strength and increasing its susceptibility to rutting. Recycled asphalt shingles (RAS) have around five times the asphalt content found on fine RAP aggregate, which can offset this issue by supplying an alternative asphalt binder, allowing for more coarse aggregate to be introduced, improving overall pavement performance and durability.

This study investigates the feasibility of incorporating RAS into high-RAP mixtures, reducing dependence on fine RAP binder. The control is a 100% RAP HMA with a baseline gradation of 60% fine aggregate and 40% coarse aggregate. A 5% RAS dosage by total mix weight was added based on manufacturer recommendations. Subsequent designs adjust the fine-to-coarse ratio while holding RAS constant to identify mixtures that meet or surpass the control’s performance. The performance was assessed through the IDEAL-CT test (ASTM D8225) for cracking tolerance and the HT-IDT test (ASTM D6931) for indirect tensile strength (ITS), benchmarked against NYSDOT thresholds of CT index ≥ 135 and ITS ≥ 35 psi.

Incorporating RAS improved the CT index by up to 6% and increased ITS as much as 15%. A mix containing 5% RAS, 35% RAP sand, and 60% RAP stone satisfied the ASTM D6931 strength requirement but didn’t consistently achieve the ASTM D8225 cracking criterion. The shortfall in the CT index values is believed to come from an underestimation of the RAS performance grade (PG), resulting in the mixture being stiffer than expected.

Hexagonal ferrites, particularly strontium ferrite (SrFe₁₂O₁₉), are among the most promising candidates for the partial substitution of rare-earth-based permanent magnets. While they have been successfully implemented in various applications, the fabrication of dense SrFe₁₂O₁₉ components with optimal magnetic properties remains a major challenge. Conventional sintering techniques often require prolonged high-temperature treatments, leading to significant grain growth and consequent deterioration of coercivity—an essential property for magnet performance.

In this study, we explore the use of advanced flash sintering techniques to overcome these limitations. Flash sintering, a rapidly growing field within the FAST (Field-Assisted Sintering Technology) family, enables dramatic reductions in processing time and temperature, offering a more sustainable route for ceramic fabrication. We report on the successful synthesis of SrFe₁₂O₁₉ using three distinct flash-based methods: reactive flash sintering (1), multiphase-reactive flash sintering (2), and touch-free flash sintering (3). These approaches not only improve densification kinetics but also help retain fine microstructures that are critical for high coercivity.

Our results highlight the strong potential of flash techniques for scalable, energy-efficient production of high-performance SrFe₁₂O₁₉ magnets, paving the way for broader industrial adoption of rare-earth-free magnetic materials.

References

[1] A.F. Manchón-Gordón et al. Reactive flash Sintering of SrFe12O19 ceramic permanent magnets, Journal of Alloys and Compounds 922 (2022) 166203.

[2] A.F. Manchón et al. Expanding the scope of multiphase-flash Sintering: Multi-dogbone configurations and reactive processes. Ceramic International 50 (2024) 25210-25215

[3] Syed I.A. Jalali, et al. Touch-free reactive flash sintering of dense strontium hexaferrite permanent magnet Journal of the American Ceramic Society 106 (2023) 7202-7208

In the present research, a general model for the description of the microstructural evolution of metallic systems is presented, which can examine the process without direct measurements and without requiring complex sample preparations. An existing challenge in the field of microstructural studies is to determine the strain dependence of the coefficient in the Taylor and Tabor theories used for the calculation of stress from dislocation densities and hardness values. The parameter describing the geometrical factor in the Taylor equation is analysed as a function of the mean free path. From the measured hardness values, the dislocation densities and characteristic structural size are determined by existing models, in which the general dependence is described by the Sahoo stress model. The dislocation density values are compared with Kocks–Mecking–Estrin and Kubin–Estrin models, and a correlation is found between the coefficients of the various models. The model also calculates the deformation energy.

The structural model is validated by Vickers hardness indentations made on plates with three different chemical compositions from alloy series of Al-1xxx, 5xxx and 6xxx. Based on the results, the applicability can be extended to a wide range of different alloys. The model can be supported by numerical results from the literature on pure aluminum, copper, nickel, iron, chromium, niobium, and aluminum alloys.

This research is supported by the EKÖP-25 University Excellence Scholarship Program of the Ministry for Culture and Innovation from the source of the National Research, Development, and Innovation Fund.

Project no. TKP2021-NVA-29 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-NVA funding scheme.

This study provides novel insights into the influence of additive manufacturing (AM)-induced grain texture on the solidification behavior of AgCuZnSn filler metal during brazing—a phenomenon not previously reported. The AM surface was shown to affect the crystallographic orientation of the filler metal, suggesting that control over AM texture can be used to tailor the properties of brazed joints. Systematic characterization of the joint microstructure was carried out using SEM, EDS, and EBSD techniques.

AM enables the fabrication of complex geometries, but the limited part size often necessitates joining. Brazing is a suitable method for this, though further study is required to understand the interactions between AM surfaces and filler metals. In this work, AM 316L stainless steel tiles were brazed to machined SS316L cylinders using an AgCuZnSn filler metal. Variables included flux type and filler metal quantity.

Microstructural characterization focused on grain size and orientation in the joint region, particularly at the interfaces between the filler and the two different base materials. All samples exhibited porosity at the filler–cylinder interface. Two main phases were identified in the filler: a Cu-rich and an Ag-rich phase, with the Cu-rich phase forming globular structures at the AM tile interface. Notably, grain structures differed between the two interfaces.

The sample brazed with MetaBraze LT 21 showed similar crystallographic orientation in the filler and AM base metal, suggesting a more isotropic response during deformation. These findings indicate that controlling AM-induced texture could serve as a strategy to engineer the microstructure and performance of brazed joints.

Fabricating bimetallic structures (BmSs) to reduce weight and improve performance has challenges in automobile, infrastructure, and aerospace applications. This study investigates the effect of heat input, Q_H, on interfacial properties of three different wire-arc additive manufacturing (WAAM)-based BmSs, SS316L-SS308L, EN31–AA4043, and SS316L–In718, through microstructural and mechanical characterisations. The value 250-400 J/mm is the determined heat input range for SS-SS and SS-Inconel, and for steel–aluminium, the range is 35-60 J/mm. At the interface of SS316L-SS308L BmS, both the austenitic (γ) and delta-ferrite (δ-Fe) phases formed. The higher tensile strength and elongation reached 591 MPa and 37.2 %, respectively, at an optimum Q_H of 330 J/mm, as the composition of the interface was close to the mirror composition with filler wire. While the average micro-hardness achieved at the interface is 248.3 HV, due to δ-α phases, the interface hardness is enhanced. But for the SS316L–In718 interface, the formation of IMCs (FeNi and FeNi₃) is proportionally influenced by the variation in Q_H. The SEM-EDX analysis demonstrated the enhancement of interface thickness (IT) and elongation while tensile stress was reduced (optimum: 542 MPa) with increasing Q_H. The average micro-hardness value reduced (194.7 to 174.6 HV) with increasing QH due to the coarse grain structure. Conversely, the optimum Q_H was achieved at 43.55 J/mm for the EN31-Al4043 interface, and the SEM and XRD analyses revealed the brittle binary (Fe-Al) and ternary (Al-Fe-Si) IMC formations at the interface. Under optimal conditions, minimal IT (<4 µm), considerable tensile strength (73.2 MPa), very little elongation (~0.9%), and an average micro-hardness value of 128.1 HV were achieved. This analysis highlights heat input as a crucial factor for developing tailored BmSs using WAAM as it controls interface properties. To develop a multi-material high-performance structure, process parameters should be optimized.

This study investigates the effects of localized high-energy laser irradiation on polyimide film, as part of a broader effort to develop crystalline silicon–carbon protective coatings on flexible polymer substrates.

The aim of the study was to determine the optimal laser operating conditions, including wavelength, power, beam speed, and frequency modulation, in order to select the best parameters for subsequent crystallization of the material onto the substrate while minimizing damage to the polymer substrate. Polyimide PMA-40 film (40 μm thick) was irradiated using a Ytterbium pulsed fiber laser (λ = 1064 nm, maximum power = 20 W, pulse energy = 1 mJ). Several processing regimes were tested, varying key parameters such as laser power (%), beam travel speed (mm/s), modulation frequency (kHz), and the number of passes.

Significant surface modification and localized swelling were observed under Modes 1 (1 pass, 50% power, 50 mm/s, 40 kHz), 2 (1 pass, 100% power, 100 mm/s, 40 kHz), and 3 (1 pass, 50% power, 75 mm/s, 100 kHz). These conditions caused visible deformation along the laser path and disrupted the integrity of the film surface.

Conversely, under Modes 4 (50%, 100 mm/s, 40 kHz), 5 (50%, 75 mm/s, 25 kHz), and 6 (50%, 200 mm/s, 40 kHz), only isolated crater-like features (~1.5 µm in diameter) were observed, and the overall film structure remained intact.

The results obtained emphasize the importance of choosing the right laser exposure parameters to achieve a balance between effective surface modification and structural preservation of the polyimide substrate. Future work will focus on introducing a silicon–carbon intermediate layer to enhance crystallization and reduce substrate degradation during laser processing.

This work was supported by grant FZWN-2023-0004.