Search Results (776)

In powder-based additive manufacturing (AM), thermal exposure during processing can modify powder surface chemistry and promote oxide growth, even under inert atmospheres from residual oxygen contamination. This study investigates the effect of thermal oxidation on the surface chemistry and triboelectric charging behavior of three AM metal alloy powders: AlSi10Mg, 316L stainless steel (SS 316L), and Ti6Al4V. The work examines the evolution of the oxide layer during baking at 100 and 300 °C using triboelectric charging corroborated by X-ray photoelectron spectroscopy (XPS), diffuse-reflectance spectroscopy, and work-function measurements. The results show that heating modifies the surface oxide state of all powders, with changes dependent on the alloy composition and baking temperature. For AlSi10Mg, heating modified the Al₂O₃-rich surface oxide, with changes consistent with increased oxide ordering and γ-Al₂O₃-like characteristics, with the work function increasing from 4.34 ± 0.01 eV in the as-received (AR) condition to 4.92 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.91 to 1.38. For SS 316L, transformation of Cr(OH)₃ to Cr₂O₃ reduced triboelectric charge accumulation, while the oxygen concentration increased from 49.92 to 54.87 at.% and the work function decreased from 5.74 ± 0.02 to 5.28 ± 0.04 eV after baking at 300 °C. This reflected a drop in the $n$-exponent from 0.82 for AR to 0.73 at 300 °C. For Ti6Al4V, charging variations were associated with titanium oxide evolution and surface modifications consistent with rutile-related titanium oxide characteristics, with the work function increasing from 5.33 ± 0.01 to 5.44 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.49 to 0.52. Overall, triboelectric charging is a sensitive approach for detecting thermally driven surface oxide modifications in additive manufacturing powders. Full article

This study investigates the tribological performance of chromium nitride (CrN)-coated polyether ether ketone (PEEK) polymers. CrN coating was deposited by physical vapor deposition (PVD) onto two commercially available substrates: neat PEEK and a modified PEEK. The suitability of the coated substrates for tribological applications was evaluated using ball-on-disc tests against stainless-steel (SS) counterparts. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed the high thermal stability of the PEEK substrates, ensuring compatibility with low-temperature coating deposition. Microstructural analysis revealed dense and continuous CrN coatings with an average thickness of ~1.5 µm on both substrates. Tribological results of selected PEEK-based polymers showed that under the applied load of 2 N, uncoated PEEK substrates exhibited lower coefficients of friction (COFs) and smoother wear tracks compared with coated samples. In contrast, under the applied load of 4 N, CrN-coated PEEK substrates demonstrated reduced friction and improved stability relative to uncoated PEEK. This behavior is attributed to load-induced tribo-oxidation and the formation of a chromium-oxide-rich tribolayer that stabilized the sliding interface and suppressed adhesive wear. Overall, the results demonstrate that CrN coatings significantly enhance the load-bearing capacity and tribological performance of selected PEEK substrates under applied load of 4 N, highlighting their potential for advanced lightweight engineering applications requiring improved wear resistance. Full article

Bentonite slurry (BS) and steel slag powder (SS) were co-utilized to develop bentonite-slurry/steel-slag foamed concrete (BS-SSFC). The evolution of compressive strength and the associated deterioration mechanisms were examined after repeated wetting–drying exposure in four environments, namely H₂O, H₂SO₄, NaOH, and Na₂SO₄, by combining mechanical testing with microstructural observations. The mix-design results indicate that, for the SS-only mixtures, 20% SS replacement produced a relatively high strength, whereas the binary SS-BS system reached its maximum strength at 10% SS and 5% BS; this combination was consequently adopted for the durability experiments. After 20 cycles, the severity of degradation followed Na₂SO₄ > H₂SO₄ > NaOH > H₂O. XRD and SEM-EDS evidence shows that sulfate ions in the H₂SO₄ and Na₂SO₄ solutions favored ettringite-type expansive products, and Na₂SO₄ further caused salt-crystallization pressure during drying. For NaOH exposure, the main damage was related to reduced stability of cementitious phases together with ion redistribution and localized re-precipitation in a strongly alkaline pore environment. Based on fractal theory, an empirical strength–degradation correlation model was established by using SEM-derived two-dimensional apparent areal porosity as a structural parameter and by linking fractal dimension with the number of cycles. Within the scope of the present experiments, the model captures the empirical link between strength loss and apparent pore-structure deterioration in BS-SSFC; however, its use remains dependent on the image-acquisition procedure, thresholding method, and material system considered. The results provide useful support for using BS-SSFC in aggressive engineering settings such as saline ground and acid-rain regions. 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

The objective of this study was to quantitatively evaluate the effect of metallic pipe thickness on position-dependent temperature rise characteristics in vertical pipe firestop systems. Carbon steel (CS) pipes, stainless steel (SS) pipes, and a 0.5 mm galvanized steel spiral duct (GSD) were tested under the same 120 min standard fire exposure, and temperatures at key measurement positions were compared. Thinner metallic pipes produced higher temperature rises, with the clearest difference observed at the upper insulation. At 120 min, CS 3.0 and SS 2.8 reached approximately 200 and 195 °C, whereas CS 7.0 and SS 7.0 remained at approximately 106 and 114 °C, respectively. GSD 0.5 showed the highest initial rise rate at the pipe surface (~3.4 °C/min during 0–30 min). Regression analysis showed a clear relationship between cross-sectional area and upper-insulation temperature, with R² values of 0.921 and 0.878 for CS and SS at 60 min and 0.999 and 0.865 at 120 min. Conversely, the ratio of room-temperature thermal conductivity to cross-sectional area did not consistently improve this relationship. These results indicate that pipe thickness and metallic cross-sectional area should be considered when determining approval ranges for metallic pipe firestop systems. Full article

This study used red mud (RM), steel slag (SS), and desulfurization slag (DS) as raw materials to construct three catalytic oxidation systems, namely RM-DCDA/H₂O₂, SS-DS/H₂O₂, and SS-DS/peroxymonosulfate (PMS), to promote the utilization of industrial solid waste and enhance the treatment of recalcitrant antibiotic wastewater. The ciprofloxacin (CIP) degradation performances, influencing factors, and preliminary reaction mechanisms of these systems were investigated. RM formed an Fe₃N/C composite structure after acidification and dicyandiamide-assisted calcination. The Fe₃N active phase, coexistence of Fe²⁺/Fe³⁺, and N-doped C structure facilitated H₂O₂ activation and electron transfer. The SS-DS catalyst exhibited a rough and porous structure and contained Fe, Ca, and S species, which could provide reactive sites for H₂O₂ and PMS activation, following acid modification and urea-assisted calcination. Under the necessary reaction conditions, the CIP degradation efficiencies of the RM-DCDA/H₂O₂, SS-DS/H₂O₂, and SS-DS/PMS systems reached 94.60%, 92.58%, and 95.17%, respectively. These results indicate that RM- and SS-derived materials can be used for CIP oxidative degradation; however, the values should not be interpreted as a strict comparison of the intrinsic catalytic activity because the operating conditions differed among the systems. Parametric experiments showed that the catalyst dosage, oxidant concentration, and initial pH influenced the degradation efficiency. The H₂O₂-based systems were more suitable under acidic conditions, whereas the SS-DS/PMS system showed wider pH adaptability. Coexisting anion and humic acid experiments indicated that the systems were tolerant to natural organic matter, whereas HCO₃⁻ and HPO₄²⁻ inhibited degradation. CIP was further oxidized in total organic C and recycling experiments; however, it was difficult to completely mineralize it within a short reaction time, and the catalyst retained relatively high activity after repeated use. Radical quenching experiments suggested that ·OH and ·O₂⁻ participated in the degradation reactions in the RM-DCDA/H₂O₂ and SS-DS/H₂O₂ systems. In the SS-DS/PMS system, comparative quenching experiments revealed that non-radical singlet oxygen (¹O₂) was the dominant reactive species, while SO₄⁻· and ·OH contributed only marginally. In conclusion, RM and SS-DS can be used as low-cost raw materials to prepare industrial solid-waste-derived catalysts for the oxidative degradation of CIP, thereby providing a reference for industrial solid waste valorization and antibiotic wastewater treatment. Full article

Ultrashort Pulse Laser (USPL) ablation is a versatile manufacturing process, but predicting its outcomes across different materials often requires extensive and costly experimentation. This work provides a machine learning framework that leverages transfer learning to bridge the gap between simulation and experimental data, enabling accurate prediction of material behavior during USPL ablation under data-scarce conditions. We generated a high-fidelity computational dataset using the LS-PLUME^® simulator for Stainless Steel 316 (SS 316), and then complemented with targeted experimental studies on SS 316, Silicon (Si) and Aluminum (Al) to capture real-world deviations. A model pre-trained on the simulation data was successfully adapted to the experimental domain, effectively absorbing systematic deviations and extending its predictive capability to new materials with minimal experimental data. Our transfer learning framework bridged the simulation-to-experiment gap using minimal data, successfully fine-tuning a base model trained on 3075 samples with just 49 experimental points for Si and 46 for Al with mean percentage errors under 5%, thus demonstrating high data efficiency for industrial laser surface texturing. Furthermore, the application of explainable artificial intelligence revealed that the model predictions are more sensitive to peak fluence and the number of passes, with SS 316 exhibiting higher overall sensitivity to input parameter variations than Si and Al, thus providing actionable physical and process-level insight relevant for industrial optimization. Full article

Partial substitution of ordinary Portland cement (OPC) with supplementary cementitious materials is a key strategy for reducing the clinker factor and associated CO₂ emissions from cement production. This study investigates the feasibility of incorporating untreated electric arc furnace steel slag (EAF-SS), collected from a steel plant in Kenitra, Morocco, as a partial replacement of OPC in Portland cement. The material was characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), and particle size distribution (PSD) analysis. Cement blends containing 2–15 wt.% EAF-SS as a replacement of OPC were prepared and tested in accordance with EN standards to evaluate consistency, setting time, density, porosity, and compressive and flexural strengths at 2, 7, and 28 days. Increasing EAF-SS content from 2% to 15% slightly delayed the initial setting time by 3–17 min and reduced early-age compressive strength from 36 MPa for OPC to 26 MPa for the 15% blend at 2 days. At 28 days, mixtures containing 2–5% EAF-SS achieved compressive strengths of 42–52 MPa, satisfying class 42.5R requirements, whereas higher replacement levels (10–15%) reduced strength to 36–39 MPa. Flexural strength decreased from 7.5 MPa for OPC to 5.7 MPa for the 15% blend at 2 days and to 7.3 MPa at 28 days, while density decreased by 2–4% and total porosity increased from 12% to 18% with increasing slag content. Drying shrinkage decreased slightly with increasing EAF-SS content, from 630 µm/m for OPC to 560 µm/m for BC15 at 28 days, suggesting a modest beneficial effect on dimensional stability. The investigated slag exhibited an Fe₂O₃ content of ~57 wt.%, substantially higher than values commonly reported for many European and Chinese EAF slags. Accordingly, the novelty of the present work lies not simply in the geographical origin of the material, but in the standardized experimental assessment of a compositionally atypical, untreated, Fe-rich EAF steel slag used directly as a partial replacement of OPC in Portland cement. The study is intended as a first performance-oriented evaluation of this Moroccan by-product under EN-based testing conditions, rather than as a complete mechanistic or environmental assessment. These findings support the feasibility of low-level EAF-SS incorporation in blended cement and indicate a potential contribution to clinker factor reduction and associated CO₂ savings under the assumptions adopted in this study. However, the environmental benefit assessment remains preliminary and should be confirmed by full life-cycle and leaching analyses. Full article

This study presents an experimental investigation of reinforced concrete T-beams strengthened using ultra-high-performance concrete (UHPC) with steel plates, and in some cases, UHPC with a geotextile layer. Ten reinforced concrete specimens with the same internal reinforcement but different strengthening methods were tested. These included a control specimen and nine strengthened specimens. Four of the strengthened specimens had grooves in the wooden formwork before pouring to secure the strengthening composite plates inside it, four had it directly attached to the RC beam surface, and the last had vertical lines 10 mm deep to enhance bonding. The external composite plate consisted of four types: the first type included a composite of UHPC and steel plates as strips with 220 × 150 mm at 105 mm, while the remaining types consisted of a plate along the shear zones made of UHPC with steel, geotextiles, or steel and geotextiles. This study also included increasing the number of steel plate layers and the direction of strengthening placement. The results showed that all the strengthened beams failed in flexure, unlike the control specimen, which failed in shear. The strengthening systems improved the load-bearing capacity and overall structural behavior of the tested beams. Among the investigated specimens, beam IR-2S90SS, strengthened with two layers of steel plates, showed the highest improvement, achieving a 39.2% increase in ultimate load compared to the control beam. Debonding was observed in some specimens and was identified as one of the governing failure mechanisms. Overall, the investigated strengthening techniques demonstrated their effectiveness in improving the structural performance of reinforced T-beams. Full article

The high-voltage spinel ${\mathrm{LiNi}}_{0.5}{\mathrm{Mn}}_{1.5}{\mathrm{O}}_4$ (LNMO) is a promising cobalt-free cathode material for lithium-ion batteries, yet its integration as a binder-free thin film on metallic current collectors via simple solution routes remains underexplored. Here, LNMO films were synthesized on 304 stainless steel (SS304) by metal–organic decomposition (MOD) from metal–acetate precursors in ethanol, followed by spin-coating and annealing at 500, 600, and 700 °C under flowing ${\mathrm{O}}_2$. The films were characterized by XRD, FESEM–FIB cross-sectioning, EDS, and XPS, and tested as binder-free cathodes by cyclic voltammetry and galvanostatic charge/discharge. All samples are dense, approximately 1.9 μm thick, and crystallize in the disordered spinel phase. The LNMO crystallite size increases from 21.9 to 43.8 nm between 500 and 700 °C, while the grain size also shows a temperature dependence, increasing the average size from 25 up to 56 nm in diameter. XPS confirms ${\mathrm{Mn}}^{4+}$ as the dominant manganese surface species (45–49%) across all samples. The films deliver reversible discharge capacities of 92, 92, and 70 mAh ${\mathrm{g}}^{-1}$ at 0.1 C for LNMO500, LNMO600, and LNMO700, respectively, with well-defined ${\mathrm{Ni}}^{2+}{\mathrm{/Ni}}^{3+}$ and ${\mathrm{Ni}}^{3+}{\mathrm{/Ni}}^{4+}$ redox peaks at 4.7 and 4.8 V. DFT calculations independently predict a voltage plateau at ∼4.7 V for $0.2\le x\le 1$, in agreement with the experimental profiles. These findings establish MOD as a viable, vacuum-free route to the synthesis of nanostructured LNMO cathodes. Full article

As a novel low-carbon material, alkali-activated materials (AAMs) can effectively mitigate the environmental burden caused by the cement industry, and their functional development can further enhance their additional commercial benefits. This study employed alkali-activated blast-furnace slag (AAS) as a matrix and incorporated steel slag (SS) as a functional component, and the compressive strength, workability, shrinkage characteristics, microstructure, and microwave-absorbing properties of SS-containing AAS were systematically investigated. The results show that although the low reactivity of SS impairs the compressive strength of AAS, it effectively reduces the setting rate of AAS. At an SS dosage of 50% (sample B-S50), the 28-day drying shrinkage of AAS reached a minimum value of 778 με. The dissolution and hydration of SS provide additional Ca²⁺ and OH⁻ for AAS, thereby effectively promoting the hydration of blast-furnace slag and facilitating the formation of C–(A)–S–H and N–A–S–H gels. Moreover, SS acts as a conductive functional component, enhancing the conductivity of AAS and enabling a minimum reflection loss of −29.47 dB with 0.53 GHz effective bandwidth at 20 mm thickness. After further modification with steel fibers, the thickness-dependence of the microwave-absorbing properties of AAS was reduced, allowing effective absorption across multiple thicknesses (5 mm, 15 mm, and 25 mm). This study offers new insights into the high-value utilization of low-reactivity industrial solid waste and offers design methods for its functional development. Full article

Reusing industrial byproducts to prepare recycled aggregate concrete (RAC) is a sustainable approach that can protect the ecological environment. This study tested the possibility of preparing an eco-efficient recycled concrete containing steel slag (SS), ground-granulated blast-furnace slag (GGBS), and polypropylene (PP) fibers to avoid resource waste and depletion and decrease CO₂ emissions. To this end, 12 mix proportions were designed to analyze the effects of SS, GGBS, and PP fibers on the macro- and micro-performances of the developed RAC. The experimental results showed that increasing the SS content decreased the RAC mechanical strength, whereas partially substituting SS with GGBS in the RAC improved the mechanical properties, especially at a later stage. Adding PP fibers to the RAC containing SS and GGBS significantly increased the splitting tensile strength. However, it had little effect on the compressive strength as the PP fiber content was less than 0.6%. The microscopic experiment revealed that adding GGBS promoted the degree of hydration of SS, reduced the Ca (OH)₂ content, made the ITZ structure more compact, and optimized the pore characteristics of the RAC. Furthermore, according to the raw materials and results of mechanical properties, a hybrid Genetic Algorithm/Artificial Neural Network (GA-ANN) technique was proposed to predict the compressive strength of the RAC containing SS, GGBS, and PP fibers. We found that the proposed GA-ANN model effectively predicts the compressive strength. The findings of this study demonstrate that preparing RAC incorporating SS, GGBS, and PP fibers is promising for the reuse of industrial byproducts and construction waste. Full article

This study aims to enhance the hydration performance and mechanical strength of steel slag-based cementitious materials via the synergistic activation of Na₂SiO₃ and triethanolamine (TEA), solving the early-age hydration and low reactivity of steel slag. The mix is 32% steel slag (SS), 43% blast furnace slag (BFS), 12% desulfurized gypsum (DG), and 13% ordinary Portland cement (OPC). The full factorial design uses Na₂SiO₃ (4–6%) and TEA (0.03–0.08%) as composite activators. Mortar specimens were tested for compressive and flexural strengths at 3d, 7d, 10d, and 28d. XRD, SEM, FTIR, and TG revealed the hydration mechanism and microstructure evolution. The results show an optimal dosage of 5% Na₂SiO₃ and 0.05% TEA increasing compressive strengths at 3d and 28d by 43.10% and 22.09%, respectively, compared with the control group. This synergy improves matrix compactness, supporting the high-value utilization of steel slag and development of steel slag-based cementitious materials. Full article

This study investigates the use of sugarcane bagasse ash (SCBA) and steel slag (SS) as partial replacements for cement and natural river sand in concrete, with the objective of identifying replacement levels that maintain structural performance while reducing the consumption of conventional materials. An experimental program was conducted to evaluate the unit weight, compressive strength, and splitting tensile strength of concrete containing SCBA and SS in individual and combined replacement systems. The results showed that the incorporation of SCBA reduced concrete density, whereas SS increased unit weight due to its higher specific gravity. At 28 days, compressive strength ranged from 13.09 to 38.10 MPa, while splitting tensile strength varied between 1.81 and 4.74 MPa, depending on the replacement level and combination of materials. Among the investigated mixtures, the concrete containing 15% SCBA and 50% SS exhibited the most favourable overall performance, achieving the target compressive strength of 25 MPa required for structural applications while maintaining acceptable tensile strength. In contrast, higher replacement levels resulted in strength reductions attributed to cement dilution, increased porosity, and the delayed pozzolanic reactivity of SCBA. Overall, the findings demonstrate that appropriately proportioned SCBA and SS can be successfully incorporated into concrete without compromising structural performance. The optimal mixture provides an effective balance between mechanical performance and the utilization of alternative raw materials, highlighting the potential of these industrial by-products to support more sustainable concrete production. Full article

This study presents a hybrid additive manufacturing approach to fabricate bioinspired stainless steel 316L-copper (SS316L-Cu) multimaterial structures using laser powder bed fusion (LPBF). The present study incorporates honeycomb lattice structures with varying wall thicknesses (0.25 mm, 0.5 mm, 0.75 mm, and 1.0 mm) to investigate the effect of geometric parameters on mechanical performance. Mechanical testing was conducted according to ISO 6892 standards, and the results revealed a strong dependence of tensile strength and ductility on lattice thickness. Copper (Cu) infiltration into SS316L lattice structures improved ductility by 30% compared to the monolithic SS316L lattice, with minimal compromise in tensile strength. To complement experimental results, molecular dynamics (MD) simulations were performed to study atomic-scale deformation and validate the trend of strength enhancement with increasing wall thickness. The findings demonstrate the potential of combining LPBF and liquid Cu infiltration to develop multifunctional, mechanically robust, and thermally conductive metallic composites. This approach provides valuable insight into structure–property relationships and supports the design of next-generation multifunctional composites for structural and thermal applications. Full article