Steel columns are key structural elements in metallic frameworks, providing essential load-bearing capacity and stability. However, their long-term performance is strongly influenced by environmental exposure, which often leads to corrosion. This degradation typically begins as localized surface damage that propagates over time, reducing the effective cross-section and amplifying stress concentrations, ultimately increasing the risk of buckling and structural failure. While previous studies have largely focused on uniform corrosion, fewer investigations have addressed localized degradation in critical regions where geometric discontinuities generate significant stress concentrations. In this study, a three-dimensional numerical model was developed to analyze the impact of localized corrosion on the buckling resistance of S235 steel columns. Special attention was given to areas around base plate holes, which are particularly vulnerable to severe corrosion damage. The numerical simulations reveal that corroded columns experience a substantial reduction in buckling capacity compared with intact members. This decline is mainly attributed to the combined effects of increased local stress concentrations and plastic deformation caused by corrosion. These findings highlight the importance of incorporating elastoplastic material behavior in predictive models for accurate structural assessment. Beyond the numerical analysis, the study offers valuable insights for maintenance planning and rehabilitation strategies, providing practical guidance to enhance the durability and safety of steel structures exposed to aggressive environments.

Introduction

The growing use of 3D printing in both industrial and academic settings has increased the demand for high-quality polymeric filament [1]. Producing filament using a commercial extruder from pellets can reduce costs and improve material customization. However, ensuring dimensional stability and consistent quality remains a key challenge. This work focuses on the setup and optimization of a commercial single-screw extruder for the production of filament suitable for fused deposition modeling (FDM) 3D printers.

Methods

A commercial tabletop extruder was adapted and calibrated to process thermoplastic pellets into filament. Key operational parameters, including extrusion temperature, screw speed, and cooling rate, were systematically varied. A real-time diameter monitoring system was implemented to assess filament uniformity during extrusion. The influence of each parameter on filament diameter and surface finish was analyzed. Post-extrusion, the filament was evaluated using calipers and visual inspection to ensure dimensional consistency.

Results

This research found that maintaining a stable extrusion temperature and carefully controlling the extrusion rate and cooling environment are critical for achieving consistent filament diameter. The optimal combination of parameters led to the production of filament with a diameter close to 1.75 mm. The real-time implemented monitoring system proved effective in identifying anomalies during the manufacturing process, allowing for rapid control adjustments.

Conclusions

The successful optimization of the extrusion process enables the reliable production of polymeric filament from raw pellets using a commercial extruder. The methodology ensures dimensional stability and quality suitable for 3D printing applications. Future work will focus on extending the approach to recycled plastic to promote sustainability in additive manufacturing.

Geopolymers represent a sustainable alternative to traditional binders, as they utilize industrial and construction waste, contributing to a reduction in the environmental impact. In this context, the present research focuses on the fabrication of geopolymers from ceramic and brick powder obtained from construction waste through milling and fine sieving, resulting in particles smaller than 150 μm. The study evaluated the influence of three factors on the physical and mechanical properties of the geopolymers: sodium hydroxide (NaOH) concentration, the mass ratio of sodium silicate (Na₂SiO₃)/NaOH, and the curing method. Mixtures were prepared with mass ratios of 2:1 and 2.5:1 (Na₂SiO₃:NaOH), using dry NaOH dissolved in concentrations of 5, 7.5, 10, and 12 mol/L. A constant liquid-to-solid ratio of 0.4 was used and this was adjusted with additional water to improve workability. Three curing conditions were tested to determine the optimal method: air curing for 7 days, curing in a humid environment for 7 days, and mixed curing (6 days in air and 1 day at 60 °C before the compressive strength test). The characterization of the hardened samples included tests for density, absorption, and voids, as well as compressive strength. The preliminary results indicate that mixed curing produces higher mechanical strength and that the workability of the mixtures vary depending on the NaOH concentration and the Na₂SiO₃/NaOH ratio. This work provides criteria for optimizing the preparation and curing of geopolymers made with ceramic and brick waste, promoting their application in civil engineering within a sustainable context.

This integrated experimental–computational framework provides both empirical evidence and mechanistic insights into hydrogen transport in steels, establishing a robust pathway for the predictive modelling of embrittlement in hydrogen-based energy systems.

When steels are exposed to hydrogen, a crucial degrading process known as hydrogen embrittlement (HE) causes early brittle failure. In this investigation, baseline, pre-strained, and hydrogen-charged conditions were used to assess the mechanical reaction of annealed 0.2 weight percent carbon steel. Significant ductility loss was found in tensile testing; total elongation dropped from 34.6% in the baseline condition to 12.0% following hydrogen charge and then to 11.3% when pre-strain and hydrogen exposure were combined. In embrittled samples, the reduction in area decreased by over 80%, indicating a significant loss of toughness. Fractography showed a distinct change from brittle, flat fracture in hydrogen-charged conditions to ductile cup-and-cone fracture in uncharged specimens.

A strain-controlled diffusion model was created using Physics-Informed Neural Networks (PINN) and compared to a traditional Forward-Time Centered-Space (FTCS) solver in order to supplement the experimental results. The strain-dependent diffusivity included in the governing equation creates a feedback loop in which the concentration of hydrogen modifies the elastic modulus, strain, and diffusivity. The results show that, in comparison to Fickian diffusion, strain localisation speeds up hydrogen infiltration, which explains the experimentally observed embrittlement in pre-strained specimens.
A strong foundation for the predictive modelling of embrittlement in hydrogen-based energy systems is established by this combined experimental–computational approach, which offers empirical data and mechanistic insights into hydrogen transport in steels.

Quantum dots (QDs) have drawn a lot of attention as photocatalytic materials due to the growing need for environmentally friendly wastewater treatment technologies. Among these, carbon-based QDs, including graphene oxide quantum dots (GOQDs), graphitic carbon nitride (g-C₃N₄), and carbon quantum dots (CQDs), have exceptional optical, electronic, and surface characteristics that increase their suitability for degrading pollutants when exposed to sunlight or visible light. These composites are better at transferring charge, staying stable in light, and breaking down pollutants. In terms of environment, QDs are a promising way to clean up urban wastewater in a way that will last. They follow eco-friendly and energy-efficient treatment principles because they can use solar energy, work in mild conditions, and break things down quickly. Metal-based QDs like ZnO and CdS also have strong photocatalytic activity, but their sustainability remains a concern due to the potential release of toxic ions when they corrode in light. The green synthesis approach addresses these challenges. Using natural extracts, like polyphenols from tea leaves, to biofunctionalize surfaces has been shown to reduce toxicity and improve photocatalytic performance. Green synthesis using renewable precursors solves problems with toxicity, resource depletion, and environmental pollution, which supports a low-impact and circular technological approach. QDs are a strong type of nanomaterial for cleaning up the environment, but there are still problems with making them bigger, cheaper, and more stable and with getting them approved by the government. This study examines recent developments in the making, modifying, and use of QD-based photocatalysts in the environment, with a focus on CQD/g-C₃N₄ hybrid systems. Future research should focus on making green, non-toxic, regenerable, and highly active carbon-based QDs for safe large-scale water treatment.

Microscale synthesis in droplets enables the precise production of materials in tiny, isolated volumes, offering benefits such as high throughput, reduced reagent use, and improved reaction control. Inspired by the rose petal effect, hydrophobic surfaces with high water adhesion have shown potential for facilitating controlled synthesis within individual microdroplets. In this study, a novel hydrophobic filter paper (HFP) with high adhesion properties was fabricated and applied to carry out reactions in microscale settings. The fabrication process involves a straightforward two-step procedure and utilizes environmentally friendly chemicals. In the first step, iron hydroxide nanoparticles were deposited via a precipitation reaction, endowing the modified filter paper with hierarchical surface roughness. In the second step, a fatty acid was used to lower the surface energy and produce a hydrophobic surface (WCA ≈ 146°). The hydrophobic nature of the filter paper repels water-based liquids, while its adhesive properties enable microdroplet manipulations, such as transfer and mixing, without the use of external devices. The oxidative polymerization of aniline was demonstrated as a model reaction for the proposed microscale synthetic methodology. To the best of our knowledge, this is the first report of microscale synthesis achieved on hydrophobic paper with strong adhesion properties. This approach aligns with green chemistry principles by minimizing chemical consumption and reducing chemical waste. The fabricated HFP has potential application as a microreactor device for microscale synthesis and for reactions involving microdroplet transfer through controlled wettability and adhesion.

The objective of this study was to evaluate whether any coating material would have a beneficial influence on maintaining color stability and surface roughness, and to what extent an uncoated resin composite can keep its original color. The study evaluated three direct composite resins (Gradia Direct Anterior A2, Tetric EvoCeram A2, Filtek Z550 A2) using 30 samples per material (1 mm thick, 14 × 10 × 1 mm). Samples were prepared in 3D-printed molds, light-cured for 40 seconds, and initially smoothed with abrasive paper (grit 400–2000). The surface treatments applied were as follows: group 1—polished with a brush and Compo + polishing paste; group 2—conditioned with 37% phosphoric acid, with single bond adhesive applied, light-cured.

All samples were cleaned ultrasonically for 5 minutes. Initial surface roughness and color were measured with a profilometer and spectrophotometer. Samples were then immersed in distilled water (control), Coca-Cola (at 37 °C ) and red wine (at 10 °C), with surface roughness and color changes measurements taken on days 1, 7, and 14. Immersion media were refreshed weekly.

The most notable color changes after immersion in coloring solutions were observed in the groups treated with Coca-Cola and red wine, compared with the control group in distilled water. Statistically significant differences were found between the four evaluation stages, with the most pronounced changes occurring after 2 weeks of immersion.
This study simulates the oral environment and the exposure of restorative materials to staining agents. As the loss of esthetic properties over time is a continuous problem, the clinical significance of this research lies in demonstrating how a restorative material could resist pigmentation, when in contact with well- known high staining beverages, in order to maintain its esthetic properties and remain suitable for long-term use in the oral cavity. Moreover, the hypothesis that a coating material would protect the resin composite surface and reduce discoloration was tested.

Abstract

AISI 304 austenitic stainless steel (ASS) was systematically investigated to evaluate its mechanical behavior at cryogenic temperatures, with particular emphasis on its potential application in cryo-compressed hydrogen storage systems. Such systems are considered a cornerstone technology in the realization of global clean energy and decarbonization targets for 2050. To assess AISI 304 ASS's performance under cryogenic conditions, uniaxial tensile tests were conducted at room temperature (298 K) and at progressively reduced temperatures of −30 °C (243 K), −60 °C (213 K), and −80 °C (193 K). All experiments were performed using a universal testing machine equipped with a cooling chamber under a constant strain rate of 10⁻³ s⁻¹ to ensure the consistency and reliability of results. The experimental data revealed a distinct temperature-dependent strengthening response. The ultimate tensile strength (UTS) increased significantly by approximately 54.2% as the testing temperature decreased, while the yield strength demonstrated a more moderate improvement of 7.25%. Although uniform elongation showed a gradual reduction with decreasing temperature, the alloy retained sufficient ductility, thereby maintaining a favourable strength–ductility balance even under cryogenic conditions. These results confirm that AISI 304 ASS possesses the mechanical reliability necessary for hydrogen storage at low temperatures. Beyond its demonstrated mechanical suitability, the deployment of this widely available material supports broader sustainability objectives. Its use in cryo-compressed hydrogen storage can directly contribute to strengthening clean energy infrastructure, minimizing carbon emissions, reducing health risks associated with fossil fuel reliance, and accelerating the global transition toward a net-zero energy system by 2050.

The progressive miniaturization of electronic and photonic devices has catalyzed growing scientific interest in the structural and functional behavior of ultrathin liquid crystal (LC) films. In this study, we present the first successful fabrication of ultrathin films of 4-hexyl-4’-isothiocyanatobiphenyl (6BT), a non-glassforming liquid crystal, using organic molecular beam deposition (OMBD) under room temperature conditions. This solvent-free, vacuum-based deposition technique enables precise control over film growth and molecular organization at the nanoscale.

Quantitative thickness measurements were performed using spectroscopic ellipsometry and X-ray reflectometry, allowing nanometer-resolution characterization of film morphology. Fourier-transform infrared (FTIR) spectroscopy revealed a distinct evolution of molecular ordering with increasing film thickness. At minimal thicknesses, we observe initial self-organization dominated by π–π stacking of aromatic biphenyl cores and van der Waals interactions among alkyl chains. As the film grows thicker, a significant degree of orientational ordering emerges among the isothiocyanate (-NCS) terminal groups, suggesting enhanced intermolecular cooperativity.

Complementary broadband dielectric spectroscopy (BDS) was employed to probe the dynamic response of the films, uncovering relaxation processes and vibrational dynamics that progressively shift toward bulk-like behavior with increasing thickness. These findings provide fundamental insight into structure–property relationships in confined liquid crystalline systems.

Our results offer a new platform for tailoring liquid crystal alignment, dynamics, and interfacial interactions in ultrathin geometries, opening promising avenues for the integration of anisotropic organic materials into next-generation nanoelectronic, photonic, and sensing technologies.

Worldwide, the sunflower is an important agricultural crop—the seeds are used as a food source for people and animals, and as feedstock for liquid biofuel production. The biomass residues are utilised as solid biofuel for local heating systems and industrial facilities. Although the biomass ash is a tertiary product of biomass usage, it is not classed as waste—depending on the biomass type, it consists of valuable elements such as potassium, calcium, sodium, phosphorus, etc. The current study aims to investigate the alkalizing properties of biomass ash in two forms: sunflower husk ash (SHA) and sunflower husk ash granules (SHAGs). Both materials were characterized with dominant alkaline oxides, as K₂O was in the range of 15.09-17.56 wt. % and Na₂O was in the range of 4.42-6.19 wt. %. The pH measurements were carried out with an apparatus type HI-5522, while the elemental analysis of solid and liquid samples was performed using an X-ray fluorescence (XRF) apparatus type E-lite. The experiments were conducted with 30 ml of deionized water, different amounts (2 and 3 g) of SHA and SHAG, with and without stirring, at contact times of 2 and 72 hours. The investigated materials demonstrated good alkalizing properties—the pH rose from 6.8 to over 10.3 and remained stable over time, with a maximum pH of 10.96 for 3 g SHA without stirring, after 2 hours. The XRF results were similar for both materials—Na reacted with water was found to contain 37.51% SHA and 35.87% SHAG, while the dissolved K in the water was measured at 84.43% for SHA and 83.33% for SHAG. The obtained results are a prerequisite for further utilization of this by-product as a green chemical material for increasing pH, with different applications like the production of liquid fertilizers, soaps, etc., or for wastewater decontamination from heavy metals.