Search Results (1,027)

Dealloyed nanoporous metals have a unique bicontinuous solid/void structure that provides a sizable surface area and outstanding electrical conductivity, making them attractive candidates for use in a range of applications. But for many of these applications, the utilization of an engineered hierarchical porous network topology that promotes and optimizes mass transport would be quite advantageous. We present a soft template approach for the routine fabrication of hierarchical multimodal nanoporous gold monolith (hm-NPG). This self-supporting framework composed of multimodal porosity is produced employing a synergistic mix of metal reduction, templating, annealing, and chemical dealloying. This method provides for the simultaneous optimization of active surface area and mass transport in a porous metal electrode. It is reliable, simple, economical, accessible, and environmentally friendly. The procedure should be scalable and can produce hm-NPG for use in applications such as biosensing, energy systems, biofiltration, and catalysis. The material visually displays two visibly unique structural length scales that range from the macroporous network structure (average pore size of 0.58 ± 0.29 μm) to the mesoporous pore/ligament morphology (average pore size of 37 ± 10 nm) as determined by SEM analysis. Modification by self-assembly with lipoic acid (LA) gave a coverage of 5.12 × 10¹⁴ molecules/cm² of the hm-NPG surface, according to calculations made using thermogravimetric analysis (TGA) data. Following the dealloying procedure, a compositional study of the np-Au monolith using EDS revealed that it was almost 98.2 atomic % gold. The specific surface area of the hm-NPG was found to be 7.84 ± 0.01 m²/g (n = 3) through analysis utilizing the Brunauer–Emmett–Teller (BET) multi-point surface area method applied to krypton adsorption isotherms. BET analysis using N₂ adsorption isotherms and the Barrett–Joyner–Halenda (BJH) pore distribution analysis gives strong evidence for the additional presence of micropores of diameter 2–3 nm, thus making the material likely trimodal. Full article

In this study, pure hydroxyapatite (HAp) was successfully produced by using eggshells. The eggshells were collected locally and calcined to get CaO from them. The CaO powder was reacted with diammonium hydrogen phosphate in a mechanochemical method using attritor milling. A portion of the synthesized samples was subjected to a second calcination process at 900 °C to investigate the thermal effects on the material. The structures of the samples were investigated by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. The as-prepared HAp appeared to be nanocrystalline with low-intensity reflections, which transformed into a highly crystalline hexagonal phase after heat treatment, as revealed by XRD analysis. Quantitative analysis revealed the thermal evolution of the secondary Ca(OH)₂ phase, due to the thermal decomposition into CaO without causing HAp decomposition into tricalcium phosphates. FTIR analysis showed characteristic phosphate bands for both samples, but the calcined sample displayed sharper peaks and a clear loss of residual water and carbonates. SEM observations also highlighted the major morphological transformation. The highly aggregated as-prepared nanoparticles formed larger, well-defined grains. Notably, the calcined sample also exhibited a rough, textured surface with a macroporous network with interconnected channels. EDS analysis confirmed a Ca-P-O-rich composition, where the elevated Ca/P ratio (Ca/P = 2.28) suggested the presence of secondary calcium-rich phases. These structural, chemical, and morphological characteristics suggest that eggshell-derived HAp, with or without a second heat treatment, has high potential and may be optimized for different applications in bone tissue engineering. However, biological performance was not evaluated in this study. Full article

To enhance gold recovery from tailings of a quartz-vein gold deposit in Hainan, China, this study systematically characterized the chemical composition, mineral composition, and process mineralogical characteristics of gold particles using inductively coupled plasma optical emission spectrometry (ICP-OES), Advanced Mineral Identification and Characterization System (AMICS), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The results show that the tailings have an average gold grade of 0.44 g/t, and the gold occurs predominantly as native gold (average fineness approximately 92%). The gold grains are predominantly fine (89.74% < 10 µm, n = 312), with 92.31% occurring as locked inclusions, predominantly in quartz and chlorite. Particle-size-dependent liberation analysis reveals that gold liberation is strongly size-dependent: 42.31% of the total gold resides in the −5 µm fraction, where grains are almost entirely locked and complete mechanical liberation is technically and economically unattainable. The fine-grain size and insufficient liberation of gold from gangue minerals are the primary causes of gold loss during processing. Additionally, chlorite, as the dominant locking mineral, is prone to overgrinding and likely induces slime coating on gold surfaces, further impairing flotation recovery. A two-pronged optimization strategy is hypothesized: regrinding to a P80 of 20–45 µm combined with dispersants such as sodium silicate or sodium hexametaphosphate. These findings provide a scientific basis for gold recovery from these tailings and for the processing of similar refractory gold tailings. Full article

The activity and stability of Ni-based catalysts for CO₂ methanation strongly depend on the morphology and chemical composition of the support. In this work, Ni catalysts with four oxidic supports (SiO₂, Al₂O₃, CeO₂, ZrO₂) were synthesized via a one-step spray pyrolysis approach. Comprehensive characterization by STEM-EDS, XRD, and N₂ adsorption was used to resolve support morphology, Ni particle size, and nanoparticle incorporation into the support matrix. Beyond steady-state activity and reaction mechanism, the support material also affects the activation period and initial stability of the catalysts. By combining temperature-programmed methanation scans on fresh and spent samples with long-term stability tests, we clearly identify support-dependent changes in initial activity and their correlation with Ni–support interactions. Enhanced physical embedding and stronger chemical binding of Ni nanoparticles significantly reduce activity changes during the first hours on stream. Overall, this study demonstrates that the support and the corresponding metal–support interactions not only affect reaction pathways and activity, but also the pretreatment and activation required to reach a stable operating point, which is of crucial importance in kinetic catalysis research. Full article

The Böhme abrasion test (EN 14157) is widely used to evaluate the wear resistance of natural stones; however, the abrasive powder specified by TS 699 requiring 70–80 wt.% crystalline Al₂O₃ is not commercially available in the Turkish market. Commercially supplied abrasives deviate substantially from both the prescribed chemical composition and the grain-size distribution of TS 699, introducing a recognized but unresolved source of variability in Böhme abrasion measurements. This study evaluates the influence of abrasive type and particle-size distribution on Böhme abrasion performance with the aim of identifying which available abrasive material yields the most reliable and reproducible test results. The emphasis is therefore metrological—on test repeatability and standardization—rather than on ranking the abrasion resistance of the stones. Six natural stones representing contrasting lithologies—four crystalline marbles, one limestone, and one granite—were tested using five abrasive powders: two locally produced natural emery abrasives (Emery-1 and Emery-2), silicon carbide (SiC), white corundum, and brown corundum. Each abrasive was evaluated under both standardized graded conditions prepared in accordance with TS 699 and heterogeneous ungraded conditions reflecting common industrial practice. Chemical analyses confirmed that both emery abrasives deviate markedly from TS 699 specifications, with Al₂O₃ contents (~57.7 wt.%) well below the required range and Fe₂O₃ (~24 wt.%) considerably exceeding the standard limit. Sieve analyses further revealed substantial particle-size deviations in several commercial abrasives. One-way ANOVA demonstrated that abrasive type exerts a statistically significant influence on abrasion performance (F = 8.99, p < 0.05, η² = 0.297). SiC consistently produced the highest abrasion values, followed by corundum-based abrasives, while emery abrasives showed comparatively lower but stable performance. Independent-samples t-tests showed that particle-size grading significantly affected abrasion performance only for brown corundum (p < 0.05), attributable to its markedly elevated coarse particle fraction. Petrographic analysis, XRD, and SEM–EDS characterization of the investigated rocks confirmed that abrasion response is additionally modulated by rock mineralogy and microstructure. Under standardized grading conditions, SiC provided the most consistent and reproducible results across all lithologies, supporting its suitability as the reference abrasive for inter-laboratory Böhme testing. Locally produced emery abrasives, despite their chemical non-compliance with TS 699, yielded stable and reproducible outcomes under controlled grading, supporting their potential as cost-effective alternatives for routine testing. Full article

The aim of this paper is the analysis of the main elements of the patinas of an outdoor bronze monument by using portable energy-dispersive X-ray fluorescence (ED-XRF) equipment designed and assembled at the University of Salento. Thanks to the versatility of the ED-XRF portable apparatus, we carried out a scan based on a limited set of measurements that was representative of the studied surface of the monument before the restoration in a relatively short time and in a completely non-invasive way. We investigated the concentrations of copper, zinc, lead, chlorine, iron, tin and sulphur in the statue dedicated to the emperor Caesar Augustum, which was created in 1935 and later placed in Brindisi (Apulia, Southern Italy). Moreover, X-ray diffraction (XRD) and Raman spectroscopy were carried out for a sample of patina in order to identify its chemical composition. The information obtained can be helpful for restoration work on this statue and possible future monitoring. Full article

Freshwater contamination by phosphate and pathogenic bacteria requires low-cost multifunctional treatment materials. Unlike previous studies that use a single biogenic agent to synthesize a single nanoparticle type, this work uses one fixed Aloe vera extraction protocol to generate three chemically distinct nanoparticles (Ag, CuO, Fe₃O₄) on the same waste-derived carbon support, enabling a direct, extract-controlled comparison of nanoparticle identity on water-treatment performance. Activated carbon (AC) was prepared from waste wattle bark (Acacia mearnsii) by steam activation at 700 °C and functionalized with biogenically synthesized Ag, CuO, and Fe₃O₄ nanoparticles (NPs) using Aloe vera extract as a reducing and stabilizing agent. Average nanoparticle sizes were 43 nm for Ag, 59 nm for CuO, and 13 nm for Fe₃O₄. FTIR, PXRD, SEM-EDS, TEM, DLS, TGA, and BET analysis characterized the materials. Among the composites, Fe₃O₄NPs/AC showed the best phosphate removal performance, achieving 93% removal and a maximum adsorption capacity of 9.3 mg/g under acidic conditions, compared with 3.3 mg/g for pristine AC. Equilibrium data were better described by the Freundlich model (R² = 0.999), indicating adsorption on a heterogeneous surface. Ag NPs/AC exhibited complete inactivation of both Escherichia coli and Staphylococcus aureus within 2 h, while CuO NPs/AC (a more economical alternative) achieved near-complete inactivation of both bacteria within 6 h. AC from spent wattle bark and functionalized with green-synthesized nanoparticles is thus a promising platform for combined phosphate removal and antibacterial water treatment. Consistent with their respective roles, Fe₃O₄ NPs/AC was evaluated exclusively for phosphate adsorption, while Ag NPs/AC and CuO NPs/AC were evaluated exclusively for antibacterial activity; no single composite was tested for both functions. Full article

Laser powder bed fusion (LPBF), one of the most established metal additive manufacturing technologies, depends strongly on the physical, morphological, and rheological characteristics of the powder feedstock to ensure process stability, layer uniformity, and final part quality. This study compared three AlSi10Mg powders intended for LPBF: one ultrasonic-atomized powder and two gas-atomized powders from different suppliers. The powders were evaluated in the as-received condition and after exposure to high-temperature/high-humidity and high-temperature/low-humidity environments. Particle size distribution, SEM/EDS, helium pycnometry, Karl Fischer moisture analysis, apparent density, Carney funnel flow, FT4 powder rheometry, and a LAMMPS-based Carney funnel simulation were used. The ultrasonic-atomized powder showed the lowest moisture uptake (77.74 ppm after humid conditioning, compared with 386.9 and 495.7 ppm for the gas-atomized powders), fewer satellite particles, lower agglomeration, and higher apparent density. Its Carney funnel flow time remained nearly constant (8.0–8.6 s), whereas one gas-atomized powder increased from 12.2 to 15.2 s after humid exposure. FT4 measurements also indicated lower effective internal friction and wall-friction angles for the ultrasonic-atomized powder, while the gas-atomized powders exhibited greater resistance to motion and stronger sensitivity to the applied stress state. Although the powders showed broadly similar chemical composition, differences in particle size distribution, morphology, moisture sensitivity, and frictional behavior led to clear differences in flow performance. Because the powders also differed substantially in particle-size distribution, the effects attributed to atomization route are interpreted together with particle size and supplier effects rather than as route effects alone. The LAMMPS simulation remained qualitative because the modeled mass was limited to 10% of the estimated powder mass; nevertheless, it reproduced the same discharge ranking observed experimentally in the Carney funnel tests. Full article

Pure ZnO and ZnO/Gd₂O₃ (1 and 2 mol %) nanoneedles were synthesized via a sonochemical route and evaluated as catalytic materials for the degradation of paracetamol using glass and PTFE (Teflon) stirring rods. The morphology and elemental composition of the obtained nanostructures were investigated by SEM and EDS analyses, confirming the formation of anisotropic rod-like architectures and the successful incorporation of gadolinium species into the ZnO matrix. The optical and defect-related properties were further examined by photoluminescence and UV–Vis spectroscopy, revealing defect-related modifications in the electronic structure and improved charge carrier behavior in the gadolinium-modified samples. Comparative catalytic experiments showed higher degradation efficiencies in the system employing the glass stirring bar compared to the PTFE. However, the differences between these two setups are not limited solely to the stirring bar material, but also involve variations in interfacial contact conditions during operation. Therefore, the observed differences in catalytic activity cannot be attributed to a single mechanistic origin such as mechanically induced effects, but rather reflect the combined influence of catalyst–surface interactions and the specific nature of the stirring medium. The influence of inorganic ions on paracetamol degradation was also investigated using distilled water and aqueous solutions containing sodium chloride, sodium sulfate, and sodium hydrogen carbonate. In both systems, the ZnO/Gd₂O₃ samples exhibited higher degradation efficiency than pristine ZnO, indicating that Gd incorporation plays a key role in enhancing catalytic performance. This improvement can be associated with a modified defect structure and more favorable charge carrier dynamics in the doped material. The mineralization efficiency of the treated solutions was additionally evaluated through chemical oxygen demand (COD) measurements, confirming a significant reduction in organic load after treatment. Full article

Corrosion of reinforcing steel and degradation of concrete caused by chloride penetration are the most critical forms of durability failure in marine environments. This requires that repair materials possess both high impermeability and stable chemical binding capacity. In this study, the impact patterns of sulfoaluminate cement (SAC) dosage on the chloride erosion durability of an OPC-GGBS-SAC ternary repair system were systematically evaluated. Through chloride ion binding capacity tests, electrical flux experiments, and microscopic analytical techniques including XRD, DTG and SEM-EDS, the synergistic regulation mechanisms of the dual functions of ‘physical barrier’ and ‘chemical binding’ in the composite material were elucidated. The findings show that the performance of the composite material was optimal at an SAC content of 10%. The electrical flux of composite materials at 28 d was 28.9% lower than that of the OPC system, whilst the chloride ion binding rate increased by 3.92%. Microstructural analysis indicates that an appropriate amount of SAC promoted the generation of ettringite (AFt) to optimize the early-age pore structure and stimulated the production of more C-S-H gel and AFm phases, thus synergistically enhancing impermeability and chemical binding capacity. When the SAC content exceeded 10%, excess gypsum inhibited the formation of AFm. Moreover, the concentration of early-stage hydration led to microdefects, resulting in a decline in durability. This study identifies the optimal dosage of SAC in the ternary system and clarifies the underlying mechanism, thereby providing a scientific basis for designing high-durability repair materials suitable for harsh ocean conditions. Full article

In this study, the possibility of ²²²Rn removal through the deferrization/demanganization applied for water treatment was considered, assuming a sorption process. This study demonstrates the possible removal of dissolved radon from groundwater using manganese oxide sand (MnO₂) employed in conventional water treatment systems. Four groundwater samples with varying chemical compositions were treated, and the simultaneous removal of ²²²Rn, Mn²⁺, Fe²⁺, NH₄⁺, and NO₃⁻ was evaluated. Radon activity was quantified using a Lucas scintillation cell coupled with a Pylon AB-5 system, while inorganic ions were analyzed by ion chromatography. Structural characterization of MnO₂ sand by XRD, SEM–EDS, and FTIR confirmed a heterogeneous oxide surface favorable for adsorption. The treatment achieved average removal efficiencies of 95% for ²²²Rn, 79% for Mn²⁺, 87% for Fe²⁺, 85% for NH₄⁺, and 73% for NO₃⁻. Equilibrium adsorption capacities increased with initial contaminant concentrations, indicating a multi-species uptake. Importantly, radon removal was largely independent of coexisting ions. These results reveal the benefit of MnO₂-based water treatment, offering an effective solution for simultaneous radon and inorganic contaminant mitigation. Full article

Continuous alumina (Al₂O₃) fibers are critical reinforcement materials for ceramic matrix composites (CMCs) utilized in extreme high-temperature environments. While their baseline thermal and mechanical properties are well-documented, their long-term service reliability in complex, multi-field environments—specifically coupled thermal, hygral, and atmospheric conditions—remains insufficiently quantified. This study systematically investigates the degradation mechanisms of alumina ceramic fiber ropes subjected to simulated engine exhaust atmospheres and cyclic rain exposure. By integrating macroscopic tensile testing with rigorous multi-scale microstructural characterizations (SEM, XRD, TGA, and advanced surface chemical state analyses via EDS and XPS), a comprehensive degradation model is proposed. Our findings reveal a pronounced two-stage mechanical degradation behavior: an initial catastrophic strength collapse followed by a stabilization phase. We elucidate that the initial embrittlement is governed not merely by thermal damage, but fundamentally by the hydrothermal volatilization and depletion of the surface amorphous SiO₂ binder, which annihilates the inter-fiber cooperative load-sharing capability. Concurrently, quantitative XPS and XRD analyses strongly suggest that the internal amorphous grain-boundary films undergo rapid structural rearrangement and crystallization, effectively homogenizing the microstructure and shifting the fracture mechanics from energy-dissipative crack deflection to unhindered brittle cleavage. After the preferential depletion of the amorphous silicate phase, the exposed α-Al₂O₃ core dictates a stabilized mechanical response. This research provides critical theoretical frameworks and experimental evidence for the life-cycle assessment and microstructural optimization of advanced oxide ceramic fibers in next-generation aerospace applications. Full article

The electrochemical performance of eight commercially available bioelectrodes for electrophysiological measurements was systematically evaluated in isotonic saline solution. The studied bioelectrodes included sintered Ag/AgCl pellet, cup and ring, an Ag/AgCl multipin, tin (Sn) ring and disc, a gold cup, and a stainless-steel needle. Open circuit potential (OCP) and drift rate, electrochemical impedance spectroscopy (EIS), and electrochemical noise (ECN) measurements were performed to assess interfacial stability, impedance behavior, and generated noise in time and frequency domains. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) were used to study the morphology and chemical composition of the bioelectrodes. Ag/AgCl-based bioelectrodes exhibited the highest OCP stability and potential reproducibility, lowest impedance, and electrochemical noise, attributed to the fast and reversible Ag/AgCl electrochemical equilibrium, and high area related to roughness and porosity. EIS analysis showed predominantly low-resistance charge-transfer behavior and high capacitance for Ag/AgCl bioelectrodes, while tin, gold, and stainless-steel bioelectrodes displayed higher impedance and mixed capacitive/resistive responses associated with passive oxide films and slower interfacial kinetics. Tin, gold, and stainless-steel bioelectrodes also presented substantially higher low-frequency noise and OCP drift rate. Among all tested bioelectrodes, sintered Ag/AgCl bioelectrodes demonstrated the most favorable electrochemical characteristics for electrophysiological signal acquisition, particularly for low-amplitude and low-frequency biosignals. Full article

Animal-based biomass is gaining increasing attention in composites technology as a sustainable alternative to conventional fillers, offering a green pathway in the generation of composites exhibiting improved performance via waste valorization. In the present study, carbonized sheep wool was incorporated into high-density polyethylene (HDPE) in various weight ratios up to 10% wt. to fabricate composite specimens. The resulting composites were evaluated through Dynamic Mechanical Analysis (DMA), while their morphology and chemical structure were investigated by Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. FTIR analysis revealed the presence of residual keratin-derived oxygen- and nitrogen-containing functional groups, indicating the retention of chemically active surface functionalities upon low-temperature carbonization. This evidence is further corroborated through qualitative (SEM-EDS) elemental mapping of the pristine surfaces of sheep wool fibers and the pyrolyzed biochar product. DMA experimental data demonstrated that sheep wool-derived biochar (SWB) can effectively reinforce HDPE, resulting in stiffness enhancement while reducing viscous dissipation, thereby highlighting its potential as a sustainable, eco-friendly filler and a viable pathway for circular valorization of animal biomass waste. Full article

Due to fractures in young and mature people, combined with aging and other factors increasing year by year, there is a demand for new materials to efficiently address fracture-healing-related issues. There are designs of new biodegradable Zn-based alloys whose chemical composition provides new opportunities to manufacture medical devices for supporting and assisting bones in their healing processes. To achieve this goal, it is well known that a strength–ductility balance and appropriate degradation are required. In this context, it is vital to know and understand how the addition of elements modifies the as-cast microstructure, which is the basis of further processing steps such as heat treatment and thermomechanical processing. In the present work, a broad characterization was performed of two as-cast hypoperitectic Zn-Ag-based alloys with Mg and Cu additions. First, cooling curves were presented, and a dissertation regarding the temperature appearance of their secondary phases was made. Also, XRD and SEM-EDS techniques were performed, and their mechanical and corrosion performance was analyzed to elucidate which third element is the best option for intended orthopedic applications. Full article