Search Results (751)

Municipal sewage sludge represents a significant environmental challenge due to its large-scale production and limited disposal options. Pyrolysis, a thermal decomposition process, offers a promising approach for converting sewage sludge into biochar, a carbon-rich material with diverse environmental applications. Sewage sludge-derived biochars were prepared at pyrolysis temperatures of 300 °C, 500 °C, 700 °C, and 900 °C (denoted as B300 to B900) and evaluated for their structural, adsorption, and catalytic performance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray spectrometry (EDS) analyses revealed a distinct temperature-dependent morphological evolution and mineral exposure. The B900 biochar exhibited a BET surface area of 83.8 m²/g and the highest pore volume of 0.101 cm³/g, indicating a well-developed mesoporous structure. In catalytic degradation tests using 20 mg/L persulfate and 500 mg/L B900, rapid oxidation was observed, achieving 91% methylene blue (MB) degradation in 30 min, highlighting its role in activating persulfate via surface-bound Fe and Al species. Optimization studies confirmed that MB removal efficiency was highest at 500 mg/L biochar and 40 mg/L persulfate, and the system was not significantly affected by the tap and synthetic wastewater matrices. This work demonstrates that biochar obtained from sewage sludge can serve as an eco-friendly and multifunctional material for resource recovery and environmental cleanup. Full article

This study investigates the microstructure evolution and mechanical properties of DSS2209 duplex stainless steel fabricated via cold metal transfer wire arc additive manufacturing (CMT-WAAM). The as-deposited thin-wall components exhibit significant microstructural heterogeneity along the build height due to thermal history variations. Optical microscopy, SEM-EDS, and EBSD analyses reveal distinct phase distributions: the bottom region features elongated blocky austenite with Widmanstätten austenite (WA) due to rapid substrate-induced cooling; the middle region shows equiaxed blocky austenite with reduced grain boundary austenite (GBA) and WA, attributed to interlayer thermal cycling promoting recrystallization and grain refinement (average austenite grain size: 4.16 μm); and the top region displays coarse blocky austenite from slower cooling. Secondary austenite (γ₂) forms in interlayer remelted zones with Cr depletion, impacting pitting resistance. Mechanical testing demonstrates anisotropy; horizontal specimens exhibit higher strength (UTS: 610 MPa, YS: 408 MPa) due to layer-uniform microstructures, while vertical specimens show greater ductility (elongation) facilitated by columnar grains aligned with the build direction. Hardness ranges uniformly between 225–239 HV. The study correlates process-induced thermal gradients (e.g., cooling rates, interlayer cycling) with microstructural features (recrystallization fraction, grain size, phase morphology) and performance, providing insights for optimizing WAAM of large-scale duplex stainless steel components like marine propellers. Full article

This study aimed to determine optimal forming conditions by comparing the compaction behavior and microstructural characteristics of two Fe-based Soft Magnetic Composite (SMC) powders, Somaloy 700HR 5P and Somaloy 130i 5P. A full factorial design was employed with powder type, compaction temperature, and punch speed as variables. Finite element modeling (FEM) using experimentally derived properties predicted density and stress distributions in toroidal geometries. 700HR 5P exhibited higher stress under most conditions, while both powders showed similar axial density gradients. Experimental results validated the simulations. SEM analysis revealed that 130i 5P had fewer microvoids and clearer particle boundaries. As revealed by TEM-EDS analyses, after heat treatment, both powders exhibited a tendency for the insulation layers to become more uniform and continuous. The insulation layer of 700HR 5P was relatively thicker but retained some pores, whereas that of 130i 5P was thinner yet exhibited smoother and more continuous coverage. XRD analysis indicated that both powders retained an α-Fe solid solution. These results demonstrate that powder properties, composition, and insulation stability significantly influence compaction and microstructural evolution. This work systematically compares the formability and insulation stability of two commercial Somaloy powders and elucidates process–structure–property relationships through an application-oriented evaluation integrating experimental design, FEM, and microstructural characterization, providing practical insights for optimal process design. Full article

This study investigates the strength and microstructural evolution of SRX-stabilized aeolian sand–gravel mixtures for flexible base applications in desert roads. CBR, UPS (uniaxial penetration strength), and compressive resilient modulus tests were conducted under varying SRX dosages (0.4–1.0%) and aeolian sand contents (30–50%). The results show that increasing the SRX dosage significantly improves all three indices, with the 0.5% SRX and 30% aeolian sand mixture yielding the CBR (385.89%) and UPS (0.938 MPa) and achieving a compressive resilient modulus that meets the requirements for graded aggregate base layers. XRD FTIR and SEM–EDS analyses reveal that the SRX enhances material structure primarily through physical mechanisms, forming dense films and bonding networks without inducing significant chemical reactions. Extended curing improves structural integrity, while excessive aeolian sand reduces compactness. SRX-stabilized aeolian sand gravel is a viable base and subbase material for desert highways. Full article

In this work, a unique approach was used to synthesise black coatings on aluminium alloys (AA) 6061 and 7075 for applications in the aerospace field. In detail, plasma electrolytic oxidation (PEO) technology was used, maintaining the voltage constant at a relatively low value (V_max ≤ 292 V) during the process. NaVO₃ additive was used in the silicate-based electrolyte to obtain a black colour. The coatings were characterised by SEM-EDS, XPS, XRD, VIS-NIR spectroscopy, and EIS. The presence of vanadium oxides in the PEO coatings was detected by EDS, XPS, and XRD analyses. PEO coatings on AA7075 produced with 10 g/L of NaVO₃ exhibited exceptional optical characteristics, with a solar absorptance value of 95.3% in the VIS-NIR spectrum (wavelength range of 400–2000 nm). All the coatings improved the corrosion performances of the tested AA6061 and AA7075 by two or three orders of magnitude in 3.5 wt. % aqueous NaCl. Moreover, there was no sign of delamination, cracks, or any visible changes on coatings after thermal shock, performed by cycling samples between two extreme temperatures, −196 °C and 150 °C, respectively. Full article

Efficient and selective separation of gallium (Ga(III)) from alkaline industrial waste streams remains a significant challenge due to the coexistence of chemically similar ions such as Al(III) and V(V). In this study, a novel ion-imprinted chitosan-based adsorbent (CS/(H-CGCS)-Ga-IIP) was synthesized via a hybrid cross-linking strategy using glutaraldehyde and siloxane-modified chitosan. The optimized material exhibited a high adsorption capacity of 106.31 mg·g⁻¹ for Ga(III) at pH 9, with fast adsorption kinetics reaching equilibrium within 60 min. Adsorption behavior followed the pseudo-second-order kinetic and Langmuir isotherm models, and thermodynamic analysis indicated a spontaneous and endothermic process. In simulated Bayer mother liquor systems, the material demonstrated outstanding selectivity and a distribution coefficient ratio k_d-Ga/k_d-Al = 146.9, highlighting its strong discrimination ability toward Ga(III). Mechanistic insights from SEM-EDS, FTIR, and XPS analyses revealed that Ga(III) adsorption occurs via electrostatic interaction, ligand coordination, and structural stabilization by the siloxane network. The material maintained good adsorption performance over three regeneration cycles, indicating potential for reuse. These findings suggest that CS/(H-CGCS)-Ga-IIP is a promising candidate for the sustainable recovery of gallium from complex alkaline waste streams such as Bayer process residues. Full article

Skutterudite (CoSb₃)-based thermoelectric materials are regarded as one of the most promising candidates for mid-temperature commercial thermoelectric applications, thanks to their excellent electrical performance and alloy-based attributes. By utilizing techniques such as doping, microstructure design, and high-temperature solid-state reactions, synthesis of Brass_x/Co₄Sb_11.5Te_0.5 (x = 0.1, 0.3, 0.5, 0.7, representing wt%) in composite form can be rapidly achieved. XRD analysis indicates that the prepared Brass_x/Co₄Sb_11.5Te_0.5 samples primarily exhibit the CoSb₃ crystal structure, with the formation of minor impurity phases such as Cu₁₃Te₇ and ZnTe. SEM and EDS analyses reveal that the sample is composed of nanoscale equiaxed grains, some of which are micrometer in size, with a large number of microporous structures distributed uniformly, forming abundant grain boundaries. By co-doping with brass and tellurium (Te), the carrier concentration can be effectively regulated, thereby enhancing the power factor of CoSb₃-based thermoelectric materials. Meanwhile, the introduction of nanostructures, grain boundaries, and defects optimizes the microstructure of the samples, leading to a reduction in the lattice thermal conductivity of the CoSb₃-based thermoelectric materials. At a testing temperature of 781 K, Brass_0.1/Co₄Sb_11.5Te_0.5 achieved a maximum power factor of 1.86 mW·m⁻¹·K⁻², a minimum lattice thermal conductivity of 1.02 W/(mK), and a maximum thermoelectric figure of merit ZT of 0.81. Full article

Manure-derived biochar is a promising soil amendment, though its effectiveness is often constrained by limited structural stability and inconsistent nutrient retention. This study evaluated how the pyrolysis method (pre- vs. post-pyrolysis) and rate (5%, 10%, 20%, and 30% w/w) of bentonite incorporation influence the physicochemical properties, nutrient availability, and carbon stability of manure-derived biochar. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses revealed that pre-pyrolysis addition enhanced mineral integration, with silicon and aluminum contents increasing by up to 500% and 600%, respectively, while carbon content decreased by up to 34%. Water holding capacity (WHC) improved by approximately 102% with 5–10% bentonite, and carbon stability more than doubled (≥100% increase) at moderate application rates under pre-pyrolysis treatment. However, nitrate (NO₃⁻) and potassium (K) availability declined by up to 89% and 47%, respectively, in pre-pyrolysis treatments due to strong nutrient immobilization. In contrast, post-pyrolysis bentonite addition increased NO₃⁻ by ~44% and K by ~29%, while phosphorus (P) availability rose by 133% at 30% bentonite. Principal component analysis (PCA) showed a clear distinction between pre- and post-pyrolysis bentonite-treated biochar. Pre-pyrolysis treatments were linked to higher pH, WHC, and carbon stability, while post-pyrolysis treatments were associated with greater nutrient availability (e.g., NO₃⁻, and K levels) and higher EC. These findings underscore the importance of the pyrolysis method, showing that pre-pyrolysis bentonite incorporation strengthens biochar’s structural integrity and long-term carbon sequestration potential, whereas post-pyrolysis addition enhances immediate nutrient availability. This duality enables the development of targeted biochar formulations tailored to specific agronomic needs—whether for sustained soil improvement or rapid fertility enhancement in climate-smart and sustainable land management systems. Full article

Exposure of LIB materials to ambient conditions with some level of humidity, either accidentally owing to imperfect fabrication or cell damage, or deliberately due to battery opening operations for analytical or recycling purposes, is a rather common event. As far as humidity-induced damage is concerned, on the one hand the general chemistry is well known, but on the other hand, concrete structural details of these processes have received limited explicit attention. The present study contributes to this field with an investigation centered on the use of Raman spectroscopy for the assessment of structural modifications using common lithium iron phosphate (LFP) and nickel–cobalt–manganese/lithium–manganese oxide (NCM-LMO) cathodes. The impact of humidity has been followed through the observation of differences in Raman bands of pristine and humidity-exposed cathode materials. Vibrational spectroscopy has been complemented with morphological (SEM), chemical (EDS), and electrochemical analyses. We have thus pinpointed the characteristic morphological and compositional changes corresponding to corrosion and active material dissolution. Electrochemical tests with cathodes reassembled in coin cells allowed for the association of specific capacity losses with humidity damaging. Full article

Boron oxide is introduced into slag as a flux, significantly lowering the liquidus temperature; however, this advantage is accompanied by several undesirable consequences. This study aims to evaluate the impact of boron oxide addition on the wetting reactivity of the CaO-SiO₂-MgO-Al₂O₃-B₂O₃ slag system, particularly on platinum and graphite substrates, which are commonly utilized for wettability investigations of such systems. The slag system was modified to incorporate varying concentrations of B₂O₃, reaching up to 30 wt%, with the addition of this oxide at the expense of CaO and SiO₂ in a constant ratio, while the contents of Al₂O₃ and MgO remained unchanged. High-temperature wettability tests were conducted at temperatures up to 1550 °C under a flow of high-purity argon atmosphere (99.9999%). For the platinum substrate, the results indicated non-reactive wetting, characterized by a decrease in wetting angles with increasing temperature and boron oxide content. Conversely, for the graphite substrate, the nature of wetting varied, resulting in either reactive or non-reactive behavior depending on the B₂O₃ content. Following the high-temperature experiments, additional analyses were performed using scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). Furthermore, the powdered oxide systems underwent characterization through Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). Full article

This investigation examines the impact of machine-made sand methylene blue (MB) values on mortar properties and microstructure through controlled clay type and content testing, encompassing macro-performances, microstructures, and mechanisms measuring compressive strength, flexural strength, drying shrinkage, frost resistance, impermeability, pore structure, microstructure, interfacial transition zones (ITZs), and hydration products. MB testing demonstrates that montmorillonite and illite exhibit a significant sensitivity divergence, where 1% montmorillonite achieves an MB value of 1.42, exceeding 1.40, while illite requires a 5% content to attain an MB of 1.50, complying with SL/T 352-2020 specifications. Increasing MB values induce an initial rise followed by a decline in 7d compressive strength yet a persistent increase in flexural strength for montmorillonite mortars, with both strength parameters decreasing at 28d and 90d. Illite mortars exhibit progressive declines in compressive and flexural strength across all curing ages (7d, 28d, and 90d) with rising MB values. SEM-EDS analyses reveal a deteriorating mortar microstructure, reduced paste compactness, and thickened ITZ under identical clay types as MB values increase. Combined XRD and TG-DTA analyses demonstrate a diminishing hydration degree and decreased hydration products in mortars with ascending MB values. Given a constant clay mineralogy, elevated MB values inhibit hydration-product formation, causing incomplete cement hydration reactions and deteriorated ITZ microstructures, consequently impairing mortar macro-performances. Full article

The objective of this study was to investigate the physicochemical properties of hybrid coatings with titanium nitride and boron nitride nanoparticles deposited on the TiAlV medical alloy via the sol–gel process. The developed layers were intended to impart bactericidal properties and provide protection against surgical abrasions during the implantation procedure. This study focused on evaluating the microstructure (SEM + EDS), structure (XRD, FTIR), and surface properties, including wettability, surface free energy, and roughness of the synthesized layers. Our results confirmed that it was feasible to produce hybrid layers with various microstructures and diverse layer morphologies. The FTIR and XRD structural analyses confirmed the presence of an organosilicon matrix incorporating the two aforementioned types of ceramic particles. Full article

The Qinghai–Tibet Plateau presents a unique challenge for infrastructure development due to its extreme geological and climatic conditions—high elevation, large diurnal temperature fluctuations, frequent freeze–thaw cycles, intense ultraviolet radiation, and seasonal precipitation. These factors greatly accelerate the weathering of rock materials, leading to aggregates with increased porosity, microcracking, and weakened mechanical properties. While the engineering implications of such degradation are evident, the underlying material science of weathered aggregates—particularly their microstructure–property relationships—remains insufficiently explored, necessitating further investigation to inform material selection and design. In this study, three representative types of weathered aggregates (silica-rich, carbonaceous, and alumina-rich), alongside unweathered natural aggregates, were examined through both macro-scale (density, water absorption, crushing value, abrasion resistance) and micro-scale (scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS)) analyses. To capture the material evolution, we introduced a simplified classification framework based on the Si/Al ratio and porosity and applied a gray entropy correlation model to quantify the coupling between microstructure and mechanical performance. Results show that weathering reduces the Si/Al ratio from 2.45 to 1.82, increases porosity from 4.2% to 12.7%, enlarges the average pore size to 0.85 μm, raises microcrack density to 1.40 μm/μm², and increases the proportion of connected pores to 68.2%. These microstructural degradations correlate with decreased aggregate density, increased water absorption (up to 8.0%), higher crushing value (27.4%), and abrasion resistance loss (26.0%). Based on these findings, a weathered aggregate classification and pretreatment strategy is proposed, offering a practical reference for engineers to improve material performance in high-altitude road construction. Full article

Nitrate (NO₃⁻) and cadmium (Cd²⁺) are common water pollutants with distinct chemical behaviors, often requiring different removal strategies. This study presents a low-cost synthesis of carbonated hydroxyapatite nanopowder (cHA), Ca₅(PO₄)_3-y(CO₃)_y(OH) (y = 0.13–0.17), using eggshell waste as a calcium precursor, aimed at removing both NO₃⁻ and Cd²⁺ from wastewater. SEM and TEM analyses revealed a porous nanostructure with an average particle size of 13.53 ± 6.43 nm and a specific surface area of 7.568 m²/g. Adsorption experiments were conducted under varying conditions, including contact time (0.3–3 h), dosage (0.3–2 g/L), initial concentrations (10–100 mg/L for NO₃⁻; 5–15 mg/L for Cd²⁺), and temperature (22 and 50 ± 2 °C). Cd²⁺ removal reached up to 99% at pH 2–4.5, while NO₃⁻ removal peaked at 38% in competitive systems, within 30 min. In single-ion systems, maximum nitrate uptake was 19.14 mg/g at 50 °C. Characterization using FT-IR, EDS, and XRD (with Rietveld refinement) confirmed carbonate B-type substitution and structural changes due to ion exchange and chemisorption. The results demonstrate that cHA derived from food waste is an efficient and sustainable sorbent, particularly for cadmium removal in contaminated water. Full article

This study investigates the adsorption performance of activated carbon (AC) derived from food and agricultural waste, specifically coffee grounds, coffee skin, bamboo, and palm leaves, for the removal of two antibiotics: amoxicillin (AMX) and sulfamethoxazole (SMX). The ACs were synthesized via KOH and ZnCl₂ chemical activation and characterized through BET surface area analysis, thermal stability, electrical conductivity, SEM, EDS, and FTIR. Among all samples, bamboo-derived AC (B-AC) exhibited superior properties, such as the highest surface area (860 m²/g), thermal stability (855 °C), conductivity (0.063 S/cm), and adsorption capacities (292.6 mg/g for AMX and 195.7 mg/g for SMX). SEM and EDS analyses confirmed successful antibiotic adsorption with morphological and elemental changes, while FTIR spectra indicated interaction with surface functional groups. Adsorption data were best described by the Langmuir and Dubinin–Radushkevich isotherm models, suggesting a monolayer physical adsorption process dominated by micropore filling (E < 8 kJ/mol). In contrast, BET and Flory–Huggins models exhibited poor fit, confirming the absence of multilayer or partition-based adsorption mechanisms. Kinetic modeling showed that AMX followed a pseudo-second-order model, while SMX exhibited a more complex adsorption behavior. Thermodynamic studies confirmed that both processes were spontaneous, with AMX adsorption being endothermic and entropy-driven and SMX being exothermic but favorable. These findings demonstrate the high potential of B-AC as a low-cost, eco-friendly, and efficient adsorbent for pharmaceutical removal from water, supporting circular economy and sustainability goals. Full article