Search Results (79)

Cemented carbides are among the primary materials for tools and wear parts. Today, energy prices and carbon emissions have become key concerns worldwide. Cemented carbides consist of tungsten carbide combined with a binder, typically cobalt, nickel, or more recently, various high-entropy alloys. Producing tungsten carbide involves reducing tungsten oxide, followed by carburization of tungsten at 1400 °C under a hydrogen atmosphere. The tungsten carbide produced is then mixed with the binder, milled to achieve the desired particle size, and granulated to ensure proper flow for pressing and shaping. This study aims to bypass the tungsten carburizing step by mixing tungsten, carbon, and cobalt; shaping the mixture; and then applying reactive sintering, which will convert tungsten into carbide and consolidate the parts. The mixtures were prepared by planetary ball milling for 10 h under different conditions. Tests demonstrated that tungsten carburization successfully occurs during sintering at 1450 °C for 1 h. The samples exhibit a typical cemented carbide microstructure, characterized by prismatic grains with an average size of 0.32 μm. Densification reached 92%, hardness is approximately 1800 HV30, and toughness is 10.9 ± 1.15 MPa·m^1/2. Full article

Mechanochemical and transition-metal-catalyzed reactions of alkynes, exhibiting significant advantages like short reaction time, solvent-free, high yield and good selectivity, were considered to be green and sustainable pathways to access functionalized molecules and obtained increasing attention due to the superiorities of mechanochemical processes and the reactivities of alkynes. The ball milling and CuI-catalyzed Sonogashira coupling of alkyne and aryl iodide avoided the use of common palladium catalysts. The mechanochemical Rh(III)- and Au(I)-catalyzed C–H alkynylations of indoles formed the 2-alkynylated and 3-alkynylated indoles selectively. The mechanochemical and copper-catalyzed azide-alkyne cycloaddition (CuAAC) between alkynes and azides were developed to synthesize 1,2,3-triazoles. Isoxazole could be formed through ball-milling-enabled and Ru-promoted cycloaddition of alkyne and hydroxyimidel chloride. In this review, the generation of mechanochemical and transition-metal-catalyzed reactions of alkynes was highlighted. Firstly, the superiority and application of transition-metal-catalyzed reactions of alkynes were briefly introduced. After presenting the usefulness of green chemistry and mechanochemical reactions, mechanochemical and transition-metal-catalyzed reactions of alkynes were classified and demonstrated in detail. Based on different kinds of reactions of alkynes, mechanochemical and transition-metal-catalyzed coupling, cycloaddition and alkenylation reactions were summarized and the proposed reaction mechanisms were disclosed if available. Full article

Wood ash is a promising supplementary cementitious material (SCM) due to its inherent pozzolanic properties. Intensive grinding has been shown to enhance this aspect and reduce the negative effects of variability in the chemical composition. This study investigated the influence of grinding through ball milling on the pozzolanic properties of wood ash. Four different types of wood ash were studied, each subjected to grinding durations of 10 and 20 min. Coal fly ash was used as a reference material. The pozzolanic activity of raw and ground wood ashes was evaluated using the strength activity index (SAI), the Frattini test, the R3 test, thermogravimetric analysis (TGA/DTG), X-ray diffraction (XRD) analysis, and scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). The results indicated that both 10 min and 20 min grinding durations enhanced the reactivity and compressive strength. However, the 10 min grinding duration showed better overall performance than 20 min grinding, likely due to reduced agglomeration and more effective particle refinement. For calcium-rich wood ashes, the reactivity was linked to the hydraulic properties rather than the pozzolanic properties. Full article

In this study, we investigate the environmental stability of the sulfide-based argyrodite solid electrolyte Li₆PS₅Cl₀.₅Br₀.₅, a promising candidate for all-solid-state lithium batteries due to its high ionic conductivity and favorable mechanical properties. Despite its potential, the material’s sensitivity to ambient air humidity presents challenges for large-scale battery manufacturing. Moisture exposure leads to performance degradation and the release of toxic hydrogen sulfide (H₂S) gas, raising concerns for workplace safety. The objectives of this study are to validate the electrolyte synthesis process, evaluate the effects of air humidity exposure on its reactivity and ionic conductivity, and establish a standardized protocol for assessing environmental stability. We report a synthesis method based on ball milling and heat treatment that achieves an ionic conductivity of 2.11 mS/cm, along with a fundamental study incorporating modeling and formulation approaches to evaluate the electrolyte’s environmental stability. Furthermore, we introduce a simplified testing method for assessing environmental stability, which may serve as a benchmark protocol for the broader class of argyrodite solid electrolytes. Full article

To improve the combustion performance of boron powder, a method was developed for synthesizing boron–magnesium–titanium (B-Mg-Ti) ternary composite powders with controlled metal content. Boron–magnesium (B-Mg) base materials were first prepared via electrical explosion, followed by the incorporation of titanium powder at varying mass fractions (1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.%) through mechanical ball milling. Field emission scanning electron microscopy (FE-SEM) revealed that the addition of titanium promoted a more uniform dispersion of magnesium within the boron agglomerates. Moreover, nanoscale titanium particles were observed to be embedded on the particle surfaces, confirming successful microscale composite formation. Particle size distribution was measured using a Malvern 3000 laser particle size analyzer, and results showed that the particle size of the ternary composites decreased gradually with increasing titanium content. Specific surface area was determined via the Brunauer–Emmett–Teller (BET) method, with all samples exhibiting values greater than 15 m²/g, indicating good surface reactivity. Furthermore, the rheological behavior of the B-Mg-Ti composite powders, when combined with terminal hydroxyl polybutadiene (HTPB)—a typical binder in solid propellants—was evaluated. Viscosity measurements were conducted using a rotational rheometer at constant temperatures of 20 °C and 70 °C. The results demonstrated a marked decrease in viscosity with increasing titanium content, suggesting that titanium incorporation enhances the flowability of the composite powders. This study systematically evaluated the influence of titanium content on the structural and physicochemical properties of B-Mg-Ti composite powders, thereby providing a valuable experimental foundation for the optimized design of boron-based combustion systems and the enhancement of their processing and application performance. Full article

LaFeO₃/TiO₂ composites were prepared in the range 0–12.2 wt% of LaFeO₃, characterized, and tested for both benzoic acid (BA) and 4-methoxycinnamic acid (MCA) degradation in aqueous solution, and hydrogen evolution. The preparation method was via ball-milling without thermal treatment. The composite materials presented agglomerates of LaFeO₃ with an average size from 1 to 5 μm, and the TiO₂ powder was well dispersed onto the surface of each sample. They showed varying activities for BA degradation depending on composition and light wavelength. The 6.2 wt% and 12.2 wt%-LaFeO₃/TiO₂ composites exhibited the highest activity under 380–800 nm light and could degrade BA in 300 min at BA concentration 13.4 mg L⁻¹ and catalyst 0.12 g L⁻¹. Using a 450 nm LED light source, all composites degraded less than 10% of BA, but in the presence of H₂O₂ (1 mM) the photocatalytic activity was as high as 96% in <120 min, 6.2 wt%-LaFeO₃/TiO₂ composite being the most efficient sample. It was found that in the presence of H₂O₂, BA degradation followed first order kinetic with a reaction rate constant of 4.8 × 10⁻⁴ s⁻¹. The hydrogen production rate followed a classical volcano-like behavior, with the highest reactivity (1600 μmol h⁻¹g⁻¹ at 60 °C) in the presence of 3.86%wt- LaFeO₃/TiO₂. It was also found that LaFeO₃/TiO₂ exhibited high stability in four recycled tests without losing activity for hydrogen production. Furthermore, a discussion on photogenerated charge-carrier transfer mechanism is briefly provided, focusing on lacking significant photocatalytic activity under 450 nm light, so p-n heterojunction formation is unlikely. Full article

This review explores hydrogen production via magnesium hydrolysis, emphasizing its role in the energy transition. Articles were selected from the Scopus database based on novelty. Magnesium’s abundance, high reactivity, and potential for recycling industrial waste make it a strong candidate for sustainable hydrogen production. A key advantage is the use of non-potable water, enhancing environmental and economic benefits. A major challenge is the passivating Mg(OH)₂ layer, which limits hydrogen release. Recent advances mitigate this issue through additives (metals, oxides, salts), alloying (Ni, La, Ca), mechanical treatments (ball milling, cold rolling), and diverse reaction media (seawater, acids, saline solutions). These strategies significantly improve hydrogen yields and kinetics, enabling industrial scalability. Magnesium hydrolysis exhibits a wide activation energy range (3.5–102.6 kJ/mol), highlighting the need for optimization in additives, concentration, temperature, and medium composition. Critical factors include additive selection, particle size control, and alloying, while secondary additives have a minimal impact. This review underscores magnesium hydrolysis as a promising, circular, economy-compatible method for hydrogen generation. Despite challenges in balancing efficiency and environmental impact, recent advancements provide a solid foundation for scalable, sustainable hydrogen production. Full article

LiAlH₄, characterized by high hydrogen capacity and metastable properties, is regarded as a promising hydrogen source under mild conditions. However, its reversible regeneration from dehydrogenated production is hindered thermodynamically and kinetically. Herein, we demonstrate an active Li–Al–Ti nanocrystalline alloy prepared by melt spinning and cryomilling to enable directly synthesizing nano-LiAlH₄. Due to the non-equilibrium preparation methods, the grain/particle size of the alloy was reduced, stress defects were introduced, and the dispersion of the Ti catalyst was promoted. The refined Li–Al–Ti nanocrystalline alloy with abundant defects and uniform catalytic sites demonstrated a high reactivity of the particle surface, thereby enhancing hydrogen absorption and desorption kinetics. Nano-LiAlH₄ was directly obtained by ball milling a 5% Ti containing Li–Al–Ti nanocrystalline alloy with a grain size of 17.4 nm and Al₃Ti catalytic phase distributed under 20 bar hydrogen pressure for 16 h. The obtained LiAlH₄ exhibited room temperature dehydrogenation performance and good reversibility. This finding provides a potential strategy for the non-solvent synthesis and direct hydrogenation of metastable LiAlH₄ hydrogen storage materials. Full article

In this study, the novel composite materials of activated carbon (AC) and persulfate (PS) doped by nitrogen (N) and sulfur (S) were successfully synthesized through one-step mechanical ball milling. Different from the previous liquid-phase activation process of PS, the direct in situ solid-phase activation of PS was achieved through the newly generated chemical bonds between AC and PS. The increased crystal surface exposure and highly electronegative atoms provided more reactive sites for the modified composites, enabling them to extract electrons from the pollutant. Compared to S doping, the N-doped composite exhibited a higher oxidative degradation ability, with a removal rate of 93.6% for tetracycline (TC, 40 mg/L) within 40 min. The interactions between AC and PS that occur in the interior of the composite avoid the limitations of mass transfer between the solid–liquid interface, thus expanding the pH application range of the catalytic reaction and minimizing the interference of other components in the solution. The synergistic effect between active oxygen species and electron transfer is the main mechanism for promoting pollutant degradation. This research puts forward a new insight into the activation approach of PS and proposes a feasible method for the advanced treatment of TC wastewater. Full article

Single-atom catalysts (SACs) are presently recognized as cutting-edge heterogeneous catalysts for electrochemical applications because of their nearly 100% utilization of active metal atoms and having well-defined active sites. In this regard, SACs are considered renowned electrocatalysts for electrocatalytic O₂ reduction reaction (ORR), O₂ evolution reaction (OER), H₂ evolution reaction (HER), water splitting, CO₂ reduction reaction (CO₂RR), N₂ reduction reaction (NRR), and NO₃ reduction reaction (NO₃RR). Extensive research has been carried out to strategically design and produce affordable, efficient, and durable SACs for electrocatalysis. Meanwhile, persistent efforts have been conducted to acquire insights into the structural and electronic properties of SACs when stabilized on an adequate matrix for electrocatalytic reactions. We present a thorough and evaluative review that begins with a comprehensive analysis of the various substrates, such as carbon substrate, metal oxide substrate, alloy-based substrate, transition metal dichalcogenides (TMD)-based substrate, MXenes substrate, and MOF substrate, along with their metal-support interaction (MSI), stabilization, and coordination environment (CE), highlighting the notable contribution of support, which influences their electrocatalytic performance. We discuss a variety of synthetic methods, including bottom-up strategies like impregnation, pyrolysis, ion exchange, atomic layer deposition (ALD), and electrochemical deposition, as well as top-down strategies like host-guest, atom trapping, ball milling, chemical vapor deposition (CVD), and abrasion. We also discuss how diverse regulatory strategies, including morphology and vacancy engineering, heteroatom doping, facet engineering, and crystallinity management, affect various electrocatalytic reactions in these supports. Lastly, the pivotal obstacles and opportunities in using SACs for electrocatalytic processes, along with fundamental principles for developing fascinating SACs with outstanding reactivity, selectivity, and stability, have been highlighted. Full article

As a well-known photocatalyst, TiO₂ still suffers from rapid electron–hole recombination and limited visible light absorption. To overcome these challenges, the combination of graphene and TiO₂ has been proposed. However, traditional methods such as ball milling and hydrothermal synthesis face limitations, including high energy consumption and complex procedures. Here, we develop a simple and industrially feasible method to prepare reduced graphene oxide (rGO)-coated TiO₂ nanoparticles, referred to as rGO-TiO₂ composites. The optimized rGO-TiO₂ composites exhibit an enhanced photocatalytic degradation of rhodamine B (RhB) under simulated sunlight conditions, about 99.95% for 4% rGO-TiO₂ within 80 min. The first-order reaction rate constant (k) of 4% rGO-TiO₂ (0.0867 min⁻¹) is 5.42 times higher than that of nano TiO₂ (0.0135 min⁻¹). The key reactive species involved in the degradation process are identified. Additionally, the effects of pH and NaCl concentration on the degradation efficiency of rGO-TiO₂ are also investigated. The 4% rGO-TiO₂ composite exhibits an excellent photocatalytic activity within the pH range of 3.87–11.89, and the NaCl concentration does not affect its photocatalytic efficiency. After characterization, the enhanced photocatalytic activity is ascribed to the introduction of rGO and the generation of surface oxygen vacancies (O_V) and Ti³⁺ in TiO₂ crystals. Full article

Chemical looping partial oxidation of methane (CLPOM) is a low energy consumption and environmentally friendly new technology that can generate syngas. The main challenge is to find suitable oxygen carriers, which should be highly active, stable, low cost, and eco-friendly. This study found that Fe₂SiO₄ had good reactivity in the CLPOM process. Thermodynamic calculations were carried out by FactSage8.1 to demonstrate the feasibility of Fe₂SiO₄ as an oxygen carrier for CLPOM. Fe₂SiO₄ was prepared by the direct ball milling method and the high-temperature solid-phase synthesis method. The reaction properties of Fe₂SiO₄ were investigated in the fixed bed reactor. The XRD and FTIR results indicate that Fe₂SiO₄ can be synthesized successfully through the high-temperature solid-phase synthesis method. The results of fixed bed experiments showed that when the reaction temperature was 980 °C and the reaction time was 28 min, the $X_{C{H}_4}$ reached 87%, and the $S_{H_2}$ and $S_{\mathit{CO}}$ were 70% and 71%, respectively. Subsequently, 20 redox cycle experiments were conducted under the optimal reaction conditions. The results showed that Fe₂SiO₄ exhibited good reactivity in the first two cycles, and as the reaction progressed, the reduced oxygen carrier could not regain the lattice oxygen, leading to a decline in cyclic performance. This study demonstrates that Fe₂SiO₄ can couple CO₂ and CH₄ to produce syngas and is conducive to reducing carbon emissions. Full article

Pterins are molecules of substantial interest as they occur in nature in a number of forms with quite distinct and often indispensable roles. Chemically, the synthesis of the principle pterin scaffold is comparably simple, while the insolubility of the pterin building block renders synthetic derivatization extremely difficult. When aiming at modeling naturally occurring pterins of extended chemical structure, this is a considerable problem. A notable set of strategies was developed in the course of the present study, which are able to overcome the lack of reactivity of the pterin backbone. These include a strategic choice regarding protection groups, uncommon chemical transformation, ball milling and combinations thereof. Some novel pterins with quite distinct substitution motifs were successfully synthesized and characterized by spectroscopic and spectrometric analyses as well as single-crystal structural analyses for three of them. Full article

This research investigates the mechanical activation of kaolin as a supplementary cementitious material at the laboratory scale, aiming to optimize milling parameters using the response surface methodology. The study evaluated the effects of rotation speed and milling time on the amorphous phase content, the reduction in crystalline kaolinite, and impurity incorporation into the activated clay through the Rietveld method. The results demonstrated that adjusting milling parameters effectively enhanced clay activation, which is crucial for its use in low-carbon cements. High rotation speeds (300/350 rpm) and prolonged grinding times (90/120 min) in a planetary ball mill increased the pozzolanic activity by boosting the formation of amorphous phases from kaolinite and illite and reducing the particle size. However, the results evidenced that intermediate milling parameters are sufficient for reaching substantial degrees of amorphization and pozzolanic activity, avoiding the need for intensive grinding. Exceedingly aggressive milling introduced impurities like ZrO₂ from the milling equipment wear, underscoring the need for a balanced approach to optimizing reactivity while minimizing impurities, energy consumption, and equipment wear. Achieving this balance is essential for efficient mechanical activation, ensuring the prepared clay’s suitability as supplementary cementitious materials without excessive costs or compromised equipment integrity. Full article

Ethanol sensors have found extensive applications across various industries, including the chemical, environmental, transportation, and healthcare sectors. With increasing demands for enhanced performance and reduced energy consumption, there is a growing need for developing new ethanol sensors. Micro-electromechanical system (MEMS) devices offer promising prospects in gas sensor applications due to their compact size, low power requirements, and seamless integration capabilities. In this study, SnO₂-TiO₂ nanocomposites with varying molar ratios of SnO₂ and TiO₂ were synthesized via ball milling and then printed on MEMS chips for ethanol sensing using electrohydrodynamic (EHD) printing. The study indicates that the two metal oxides dispersed evenly, resulting in a well-formed gas-sensitive film. The SnO₂-TiO₂ composite exhibits the best performance at a molar ratio of 1:1, with a response value of 25.6 to 50 ppm ethanol at 288 °C. This value is 7.2 times and 1.8 times higher than that of single SnO₂ and TiO₂ gas sensors, respectively. The enhanced gas sensitivity can be attributed to the increased surface reactive oxygen species and optimized material resistance resulting from the chemical and electronic effects of the composite. Full article