Search Results (1,531)

The oxygen reduction reaction (ORR), as a key electrode process in fuel cells and metal-air batteries, plays a pivotal role in advancing clean energy technologies. However, the slow kinetics and high overpotential of the ORR significantly limit the efficiency of these energy devices. Therefore, the development of efficient, stable, and cost-effective ORR catalysts has become a central focus of current research. Carbon-based catalysts, with their excellent conductivity, chemical stability, and tunable structural features, have emerged as promising alternatives to traditional precious metal catalysts. Nevertheless, challenges remain in the design of active sites, the tuning of electronic structures, and the large-scale synthesis of carbon-based catalysts. This review systematically introduces the fundamental mechanisms and key factors influencing the ORR, providing an analysis of the critical variables that affect catalyst performance. Furthermore, it summarizes several common methods for synthesizing carbon-based catalysts, including pyrolysis, deposition, and ball milling. Following this, the review categorizes and discusses the latest advancements in metal-free carbon-based catalysts, single-atom and dual-atom catalysts, as well as metal-based nanoparticle catalysts, with a particular focus on their mechanisms for enhancing the ORR performance. Finally, the current state of research on carbon-based ORR catalysts is summarized, and future development directions are proposed, emphasizing the optimization of active sites, improvements in catalyst stability, and potential strategies for large-scale applications. Full article

Background/Objectives: This article reports on the scalability of a combined wet grinding technique applying planetary ball mill and ZrO₂ pearls as the grinding medium. After the determination of the parameters in a laboratory scale, the tenfold scale-up method was set. Meloxicam (MEL) was used as a nonsteroidal anti-inflammatory drug (NSAID) intended for per os delivery. During grinding, the PVA solution was used as a dispersion medium. Methods: The influence of the scaling-up on the particle size, morphology, crystallinity, and intra- and interparticulate phenomena has been studied. Formulation investigations of the milled suspensions were carried out. The dissolution test and the cytotoxicity analyses were accomplished. Results: Submicron MEL particle-containing samples were produced in both grinding scales. After the particle size determination was achieved from the suspensions, the wet milled, dried products were studied. The particle size of the dried products fell into the same range for both scales of milling (the maximum particle size was about 580 nm). There was no significant difference in drug crystallinity after the grindings; 70% of MEL remained crystalline in both cases. A remarkable interaction between the components did not develop as a result of milling. The polarity of the products increased, which resulted in a better dissolution, especially in the case of intestinal fluid (~100% in the first 5 min). The products were not found to be toxic. Conclusions: This research demonstrates that the scaling-up of combined wet grinding technique is feasible by adjusting the milling parameters and the adequate amount of excipient. Full article

Shear emulsifying (SE), ball milling (BM), and autoclave treatment (AT) were utilized for the modification of lotus leaves, and the effects on in vitro gastrointestinal digestion and colonic fermentation of insoluble dietary fiber (IDF) from lotus leaves were compared. Compared with SEIDF and ATIDF, BMIDF released more polyphenols and exhibited better antioxidant capacity during in vitro gastrointestinal digestion. The IDF of lotus leaves changed the gut microbiota composition during in vitro colonic fermentation. SEIDF was beneficial to the diversity of gut microbiota compared with BMIDF and ATIDF. Among the three IDF groups of lotus leaves, six significant differences of OTUs were all in ATIDF; however there was the highest relative abundance of Escherichia-Shigella in ATIDF. In addition, the concentrations of butyric acid and valeric acid produced by SEIDF were significantly higher than that of BMIDF and ATIDF. Overall, SE modification improved the colonic fermentation characteristics of IDFs in lotus leaves more effectively; while BM modification helped to promote the release of polyphenols from IDFs in lotus leaves during in vitro gastrointestinal digestion. The research lays the foundation for the application of the dietary fiber of lotus leaves as a premium fiber additive in functional food. Full article

Esterification of levulinic acid with ethanol was investigated using deep eutectic systems based on choline chloride and oxalic or p-toluenesulfonic acid as catalysts under conventional heating and alternative energy inputs, namely microwave, ultrasound, and mechanochemical treatment. The experiments were performed under varying operating conditions such as catalyst type and loading, alcohol to carboxylic acid molar ratio, temperature, or time. The obtained results demonstrate the overall better catalytic performance of the p-toluenesulfonic acid-based deep eutectic mixture in comparison with the oxalic acid-based analogue. The best results: levulinic acid conversion of 76% and 58%, for p-toluenesulfonic and oxalic acid containing deep eutectic systems, respectively, with 100% selectivity for both cases, were achieved for microwave-assisted synthesis with 5 wt.% of catalyst and excess alcohol to acid (molar ratio 5), at 413.15 K and for 10 min. The main advantage of all of the alternative activation methods studied (microwaves, ultrasounds, and ball mill processing) was the significant reduction in the reaction time. Full article

Carbon nanotube (CNT)/graphene ceramic composites with outstanding properties are expected to replace a number of components currently used in the automotive and aerospace industries in the future. Consequently, this area of research has progressed significantly. This review paper, therefore, delves into the enhancement of ceramic properties through the integration of graphene and CNTs. These reinforcements are known to mitigate the inherent brittleness of ceramics, thereby unlocking their potential for applications in sectors requiring high mechanical reliability, such as the aerospace, automotive, and biomedical industries. By summarizing recent research, this paper outlines various preparation methods, including ball milling, heat pressing and spark plasma sintering, and discusses how these techniques contribute to improved mechanical and thermal performance. This review emphasizes the critical role of graphene and CNT ratios, sizes, and their synergistic effects in enhancing fracture toughness, machinability, and overall structural integrity. Thus, this paper provides a comprehensive overview of the current research in this area and discusses the potential of these technologies. Full article

This study successfully synthesized high-tetragonality barium titanate (BaTiO₃) particles with a small particle size by implementing ball milling in the solid-state synthesis of BaTiO₃ and utilizing nanoscale raw materials. This study also addressed the issues of impurities and uneven particle size distribution that could exist in the synthesized BaTiO₃ particles. The crystal structure, morphology, and particle size of the synthesized BaTiO₃ particles have been meticulously analyzed and discussed through the use of techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and the laser particle size analyzer. BaTiO₃ has been successfully synthesized, exhibiting a uniform particle size with an average diameter of 170 nm and a high tetragonality value of 1.01022. This new solid-state synthesis method provided insights to avoid the impact of “size effects” during the process of electronic device miniaturization. Full article

In this study, the effect of powder preparation techniques on microstructure, mechanical properties, and wear behaviors of graphene-reinforced copper matrix (Gr/Cu) composites was investigated. The composite powders were prepared by two different techniques including high-energy ball (HEB) milling and nanoscale dispersion (ND). The obtained results showed that the ND technique allows the preparation of the composite powder with a smaller and more uniform grain size compared to the HEB technique. By adding Gr, the mechanical properties and wear resistance of the composite were much improved compared to pure Cu. In addition, the composite using the powder prepared by the ND technique exhibits the best performance with the improvement in hardness (40%), tensile strength (66%) and wear resistance (38%) compared to pure Cu. This results from the uniform grain size of the Cu matrix and the good bonding between Cu matrix and Gr. The strengthening mechanisms were also analyzed to clarify the contribution of the powder preparation techniques on the load transfer strengthening mechanisms of the prepared composite. Full article

The demand for advanced Al-based alloys with tailored structural and magnetic properties has intensified for applications requiring a high thermal stability and performance under challenging conditions. This study investigated the phase evolution, magnetic properties, thermal stability, and microstructural changes in the Al-based alloys Al₈₂Fe₁₆Nb₂ and Al₈₂Fe₁₄Nb₂Mn₂, synthesized via mechanical alloying (MA), using stearic acid as a process control agent. The X-ray diffraction results indicated that Al₈₂Fe₁₆Nb₂ achieved a β-phase solid solution with 13–14 nm crystallite sizes after 5 h of milling, reaching an amorphous state after 10 h. In contrast, Al₈₂Fe₁₄Nb₂Mn₂ formed a partially amorphous structure within 10 h, with enhanced stability with additional milling. Magnetic measurements indicated that both alloys possessed soft magnetic behavior under shorter milling times (1–5 h) and transitioned to hard magnetic behavior as amorphization progressed. This phenomenon was associated with a decrease in saturation magnetization (M_s) and an increase in coercivity (H_c) due to structural disorder and residual stresses. Thermal stability analyses on 10 h milled samples conducted via differential scanning calorimetry showed exothermic peaks between 300 and 800 °C, corresponding to phase transformations upon heating. Post-annealing analyses at 550 °C demonstrated the presence of phases including Al, β-phase solid solutions, Al₁₃Fe₄, and residual amorphous regions. At 600 °C, the Al₃Nb phase emerged as the β-phase, and the amorphous content decreased, while annealing at 700 °C fully decomposed the amorphous phases into stable crystalline forms. Microstructural analyses demonstrated a consistent reduction in and homogenization of particle sizes, with particles decreasing to 1–3 μm in diameter after 10 h. Altogether, these findings highlight MA’s effectiveness in tuning the microstructure and magnetic properties of Al–Fe–Nb (Mn) alloys, making these materials suitable for applications requiring a high thermal stability and tailored magnetic responses. Full article

Ice cream is popular but contains high amounts of saturated fats and few health-promoting ingredients. In the presence of xanthan gum (0.25%), blueberry peel particles prepared through ball-milling treatment (BMPs) were used to prepare ice cream containing camellia oil as a fat replacer. The BMPs possessed smaller particle sizes, larger contact angles, and higher contents of anthocyanin aglycone compared with commonly milled blueberry peel particles. BMPs with the largest contact angle (66.30°) were obtained by ball-milling the blueberry peel at 15 Hz for 6 h (BMP_15Hz6h). The ice cream mixes were depicted as linear viscoelastic gel-like solids, and their apparent viscosity, G′ and G′, increased with the increase in the BMP_15Hz6h concentration. Ice cream with strong antioxidant activity and good freeze–thaw stability was acceptable and desirable in the presence of 0.5% BMP_15Hz6h. Full article

In recent years, metal chip powders obtained from solid-state processes have shown great potential as a sustainable raw material for powder technologies. The material and fragmentation process of the chips has a significant role in the final characteristics of the powder particles, such as size and particle size distribution, shape, surface, and structure, which are essential parameters to consider when converting chips to powder for applications. However, tool steel chips as a powder raw material have not yet been significantly studied. In this study, the steel chips were from machining AISI H13 steel and the milling process used a ball mill, and the challenge was to obtain powder particle sizes of around 20 µm with suitable properties from the application of envisaged material extrusion (MEX). A comparison study with the commercial raw material for MEX, such as powder metal filament extrusion, was performed. This study highlights the behaviors of chip powders during all steps of MEX, namely, feedstock and filament production, 3D object shaping, thermal de-binding, and sintering. A comparison of the mixture based on powder from chips and commercial powders for MEX was performed after evaluating the mixing torque of the powder and the system of binders and additives suitable for the rheological characteristics required for an extrusion mixture, and optimizing the binder removal and the sintering conditions. The 3D objects resulting from chip powders had a refined microstructure, showing an increase of 15% in the microhardness when compared with the those resulting from commercial powders. Full article

In the high-speed milling of titanium alloys, the combined application of surface texture and coatings can significantly enhance the performance of cemented carbide tools. Investigating the synergistic effect of surface texture and AlSiTiN coating on tool performance is crucial for advancing the development of their integrated preparation process. Therefore, in this study, a cemented carbide ball-end milling cutter is taken as the research object, and a surface-textured AlSiTiN coating is applied to the rake face. The effects of texture and coating parameters on the milling performance of titanium alloys are analyzed, and a regression model is developed to optimize the relevant parameters. The results indicate that the surface texture effectively reduces the actual contact area between the tool and the chip, serves as a storage space for chips, and enhances the wear resistance of the AlSiTiN coating. The coating thickness significantly affects milling force, milling temperature, and surface wear. An increase in coating thickness improves the hardness and integrity of the coating surface, and it also strengthens the adhesion of the texture to the coating. Additionally, precise control of the laser power plays a key role in reducing the milling temperature, while both the number of scans and the scanning speed significantly influence surface wear. Furthermore, maintaining an appropriate distance from the edge is crucial for enhancing the surface roughness of the workpiece. The optimized parameters for surface texture and coating preparation are as follows: coating thickness (h) = 3.0 µm, laser power (p) = 40 W, scanning speed (v) = 1590 µm/min, number of scans (n) = 6, texture diameter (d) = 42 µm, texture spacing (l) = 143 µm, and distance from the edge (l₁) = 104 µm. The optimized milling performance of the milling cutter shows a significant improvement. Full article

Mineral liberation and concentration have always been the core issues in ore processing. The goal of multi-stage crushing and ball milling is liberation because mineral liberation is the foundation of beneficiation. High energy consumption and environmental pollution have always been unavoidable topics. We put forward the method of high-pressure gas rapid unloading (GRU). Particle size followed MR-R distribution. The scanning electron microscopy data showed that the liberation of apatite particles smaller than 4 mm was sufficient by high-pressure GRU methods, and high-grade apatite concentrated in the particle size range of 0.5 to 4 mm. The average grade of the preferred particle size interval was 3%–5% higher than the original ore. Liberation degrees of apatite less than 4 mm are above 88%, which was beneficial for mineral processing. Compared to the traditional crushing method, the GRU method had a higher liberation and concentration in the particle size range of 0.5 to 4 mm. The total energy consumption was about 1.76 kW·h/t, less than that of the traditional crushing method. Full article

A series of commercial silica-supported polyoxometalate ionic liquids ([C_nmim]₃PMo₁₂O₄₀) with different substitutes in the imidazole ring were prepared via a facile ball milling method and employed as catalysts in the oxidative desulfurization of organosulfur compounds. The experimental results demonstrated that the active polyoxometalate center was successfully immobilized with a highly uniform dispersion on the silica. Without any organic solvent as the extractant, sulfur removal with the sample C₁₆PMo/SiO₂-BM reached 99.5% in 30 min under the optimal condition, which was ascribed to the high specific surface area and lipophilicity. In addition, the active site was verified by a free radical trapping experiment and an ESR spin capture experiment. In addition, the oxidative product was confirmed by GC-MS analysis. Full article

V₂O₅-WO₃(MoO₃)/TiO₂ catalysts are widely used in industrial denitrification (deNO_x) processes based on the selective catalytic reduction (SCR) technique. To lower their cost and shorten the production cycle, V₂O₅-MoO₃/TiO₂ catalysts with and without CeO₂ modification were prepared using the ball milling method. This study demonstrates that the CeO₂-modified catalyst has high NO conversion and a broader temperature window due to the decreased amount of easily reducible vanadium species and the enhanced property of oxygen species activation in CeO₂. Meanwhile, the SO₂ resistance of the catalyst is restrained due to the strong adsorption and oxidation of SO₂ over CeO₂ in the catalyst. Full article

In the present study, a green, scalable, and environmentally friendly approach was developed for the fabrication of Bi₂S₃-decorated CdS nanoparticles with an efficient hydrogen generation ability from the water. As a sulfur source, thiourea was used. The process was completed in two stages: mechanical activation and thermal annealing. The presence of spherical CdS nanoparticles and Bi₂S₃ nanorods in the CdS/Bi₂S₃ nanocomposite was confirmed and proved by XRD, Raman spectroscopy, SEM-EDS, and TEM. The synthesized CdS/Bi₂S₃ nanocomposites were evaluated for their photocatalytic hydrogen evolution capabilities. The CdS/Bi₂S₃ photocatalyst exhibited 25% higher photocatalytic activity compared to CdS, reaching a hydrogen evolution rate of 996.68 μmol h⁻¹g⁻¹ (AQE 0.87%) after 3.5 h under solar-light irradiation. Full article