Search Results (642)

High density alumina–zirconia–tantalum ceramic–metal composites with the addition of 0.5 vol.% of graphene oxide were fabricated via a wet processing technique followed by spark plasma sintering. Scanning electron microscopy confirmed the even distribution of metal particles in the composite matrix. The thermal reduction of graphene oxide after consolidation at 1500 °C was proved using Raman spectroscopy. The engineered materials exhibit a fracture resistance of 16 MPa∙m^1/2, which is 30% greater than in the reference ZTA ceramic composites fabricated using the same technology. That increase in fracture toughness could be down to a synergetic interaction mechanism; more specifically, crack trapping, renucleation and blunting, and elongated tantalum particles bridging. In addition to the above-mentioned mechanisms, tetragonal monoclinic phase transformation in zirconia is also an additional source of increased crack resistance in the developed composites. Full article

This paper proposes an enhanced cooling method for multi-chip power modules (e.g., in MMC inverters) with uneven power loss in all-electric propulsion ships based on sintered heat pipe parameter optimization and special-shaped design. First, five key parameters of straight sintered heat pipes were optimized: placement directly under hotspot chips, 10 mm in diameter, quantity matching the number of hotspot chips, length equal to the heatsink side length, and direction perpendicular to heatsink fins. Then, a C-shaped heat pipe was designed using the parallel thermal resistance principle, which forms two parallel low-thermal-resistance paths and outperforms conventional U-shaped ones. Finite element simulations showed that the hotspot temperature of the conventional heatsink was 91.26 °C, while it dropped to 87.35 °C with optimized straight heat pipes and further to 80.85 °C with C-shaped ones. Experiments verified an 11.65% temperature reduction (from 86.7 °C of conventional heatsinks to 76.6 °C of C-shaped heat pipe heatsinks). This method effectively lowers hotspot temperatures, reduces device failure rates, improves the thermal reliability of power modules, and provides a generalized design methodology for heatsinks of various power electronic converters. Full article

Coal is commonly used as both fuel and reducing agent in producing synthetic rutile from ilmenite (FeTiO₃) via the Becher process, which upgrades ilmenite to high-purity TiO₂ (>88%). However, coal-based reduction generates significant carbon waste. This study investigated the effect of adding 1–5% w/w potassium hydroxide (KOH), sodium hydroxide (NaOH), and sodium tetraborate (borax) to coal during ilmenite reduction to improve metallisation and reduce carbon burn-off. Results showed that 1% w/w additives significantly increased metallisation to 96% (KOH), 95% (NaOH), and 93% (borax), compared to 80% without additives, while higher concentrations (3–5% w/w) decreased metallisation. Scanning electron microscopy (SEM)analysis showed cleaner particle surfaces and optimal metallisation at 1% w/w, whereas higher additive levels caused agglomeration or sintering due to elevated silica and alumina activity. Additive type also influenced TiO₂ quality, with KOH enhancing TiO₂ at low concentrations but causing negative effects at higher levels, while NaOH and borax reduced TiO₂ quality via sodium-based compound formation. All additives reduced carbon burn-off, with KOH producing the greatest reduction. The iodine number of the carbon residue increased with higher additive concentrations, with KOH achieving 710 mg/g at 1% w/w and 900 mg/g at 5% w/w, making the residue suitable for water treatment. Overall, KOH is the most effective additive for producing high-quality synthetic rutile while minimising carbon waste. Full article

Methane dry reforming (DRM) represents a promising route for the simultaneous valorization of CH₄ and CO₂ into syngas; however, conventional Ni-based catalysts suffer from rapid deactivation due to sintering and carbon deposition. In this work, we present a synergistically engineered Ni-based catalyst integrating hierarchical SiC confinement, Pd promotion via oleic-acid-assisted complexation, and MgO surface modification to overcome these challenges. Under optimized reaction conditions (CH₄/CO₂ = 1:1, 750 °C, GHSV = 36,000 mL g⁻¹ h⁻¹), the multifunctional NiPd/Si–xMg catalyst achieved steady-state conversions of 85% for CH₄ and 84% for CO₂, maintaining an H₂/CO ratio close to 1.0 over 100 h of continuous operation without noticeable deactivation. In contrast, the reference Ni/SiC and Ni/MgO catalysts exhibited initial conversions of 75–80% but declined by more than 50% within the same period, confirming the superior durability of the optimized system. Thermogravimetric analysis (TGA) revealed a drastic reduction in carbon deposition—from 119.0 mg C g⁻¹ for Ni/SiC to 81.4 mg C g⁻¹ for NiPd/Si-xMg—indicating enhanced coke resistance. Transmission electron microscopy (TEM) confirmed uniform Ni dispersion with an average particle size of 7.2 ± 1.8 nm, while H₂-TPR and CO₂-TPD analyses demonstrated improved reducibility and surface basicity. The combination of SiC confinement, Pd-induced hydrogen spillover, and MgO-mediated CO₂ activation effectively mitigated sintering and carbon accumulation, resulting in high activity, stability, and carbon tolerance. This integrated catalyst design provides a robust pathway toward industrially viable DRM systems for sustainable syngas production. Full article

As an energy-intensive sector, China’s iron and steel industry is crucial for achieving “Dual Carbon” goals. This study fills the research gap in systematically comparing the synergistic effects of multiple policies by evaluating five key measures (2020–2023) in ultra-low-emission retrofits and clean energy alternatives. Using public macro-data at the national level, this study quantified cumulative reductions in air pollutants (SO₂, NOx, PM, VOCs) and CO₂. A synergistic control effect coordinate system and a normalized synergistic emission reduction equivalent (AP_eq) model were employed. The results reveal significant differences: Sintering machine desulfurization and denitrification (SDD) showed the highest AP_eq but increased CO₂ emissions in 2023. Dust removal equipment upgrades (DRE) and unorganized emission control (UEC) demonstrated stable co-reduction effects. While electric furnace short-process steelmaking (ES) and hydrogen metallurgy (HM) showed limited current benefits, they represent crucial deep decarbonization pathways. The framework provides multi-dimensional policy insights beyond simple ranking, suggesting balancing short-term pollution control with long-term transition by prioritizing clean alternatives. Full article

This study presents a novel methodology for the fabrication of aluminum matrix composites (AMCs) reinforced with a hybrid of MAX phase (Ti₃AlC₂) and MXene (Ti₃C₂T_x) particles via vacuum hot-pressing sintering, aiming to enhance the mechanical properties and tribological performance of aluminum matrix composites. The hybrid-reinforced aluminum matrix composites were fabricated with Ti₃AlC₂/Ti₃C₂T_x reinforcements at a 1:1 mass ratio, incorporating reinforcement contents of 5 wt.%, 15 wt.%, and 25 wt.%, respectively. The optimized vacuum hot press sintering process was as follows: firstly, a cold press pressure of 20 MPa was applied to the composite powder, and then hot press sintering was carried out by means of segmental pressurization with a sintering pressure of 20 MPa, a temperature of 500 °C, and a heat preservation of 1 h before cooling in the furnace. It was found by micro-morphological characterization and mechanical property testing that with the increase of Ti₃AlC₂/Ti₃C₂T_x reinforcement content (5 wt.%→15 wt.%), the micro-hardness of the composites (31.9→76.1 HV_0.2), compressive strength (41.7→151.9 MPa), and tribological properties (friction coefficient 0.68→0.50) were significantly improved; however, when the content of reinforcement exceeded 15 wt.%, the deterioration of properties triggered by the increase in pore defects and particle agglomeration leads instead to a decrease in compressive strength (by 12.3%), apparent modulus of elasticity (specimen’s compressive specific stiffness, by 9.8%) and frictional stability (coefficient of friction recovered to 0.62). The 15 wt.% hybrid reinforcement composites demonstrated optimal strength-toughness synergies, exhibiting a 361.6% increase in yield strength and a 597.1% increase in apparent modulus of elasticity compared to pure aluminum. Furthermore, the friction coefficient exhibited a 26.47% reduction in comparison to pure aluminum, thereby substantiating enhanced tribological performance. The observed enhancements are attributed to the synergistic effects of the MAX and MXene phases, where MXene improves interfacial wettability and densification, while MAX particles enhance overall strength through diffusion reinforcement. Full article

In this study, TiC_xO_y was produced by sintering in an argon atmosphere using carbon–thermal reduction with TiO₂ and graphite powder as the initial materials. The sintered TiC_xO_y was analyzed using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. As the oxygen content increased, the grain color of the sintered TiC_xO_y gradually shifted from gray to reddish-brown. The structure of TiC_xO_y resembles that of a coral, with a uniform distribution of Ti, C, and O throughout the sample. Analysis using X-ray photoelectron spectroscopy reveals the presence of bivalent, trivalent, and tetravalent titanium. Utilizing General Structure Analysis System software (GSAS-II), the X-ray Diffraction data obtained were refined, revealing a gradual decrease in lattice parameters as the oxygen atom content increased. Furthermore, the conductivity and density of the single phase, determined through the four-probe method and the Archimedes method, respectively, exhibited an increase in tandem with the rise in C content. Full article

Modern manufacturing is increasingly shaped by the paradigm of Industry 4.0 (Smart Manufacturing). As one of its nine pillars, additive manufacturing plays a crucial role, enabling high-quality final products with improved profitability in minimal time. Advances in this field have facilitated the emergence of diverse technologies—such as Fused Deposition Modelling (FDM), Stereolithography (SLA), and Selective Laser Sintering (SLS)—allowing the use of metallic, polymeric, and composite materials. Within this context, Klipper v.0.12, an open-source firmware for 3D printers, addresses the performance limitations of conventional consumer-grade systems. By offloading computationally intensive tasks to an external single-board computer (e.g., Raspberry Pi), Klipper enhances speed, precision, and flexibility while reducing prototyping time. The purpose of this study is twofold: first, to identify and analyze bottlenecks in low-cost 3D printers and second, to evaluate how these shortcomings can be mitigated through the integration of supplementary hardware and software (Klipper firmware, Raspberry Pi, additional sensors, and the Mainsail interface). The scientific contribution of this study lies in demonstrating that a consumer-grade FDM 3D printer can be significantly upgraded through this integration and systematic calibration, achieving up to a 50% reduction in printing time while maintaining dimensional accuracy and improving surface quality. Full article

The present study investigates the luminescent behaviour of sol–gel derived Y₂SiO₅ powders doped with Eu³⁺ ions, subjected to spark plasma sintering. The sintering process induces the partial reduction of Eu³⁺ to Eu²⁺, and the phenomenon is strongly dependent on the holding time within the SPS chamber. The luminescent properties are tunable via the initial Eu concentration, holding time and excitation wavelength, resulting in a wide range of emission colours from red (Eu³⁺) at 220 nm excitation to blue (Eu²⁺) at 365 nm, and mixed colours at 257 nm. Moreover, the Eu³⁺/Eu²⁺ redox process is reversible. Overall, the results demonstrate that SPS conditions can be exploited to modulate the valence state of luminescent centres, which is reversible by oxidation under ambient conditions, enabling controlled modulation of the optical properties. Full article

This study investigates the impact of in situ boron reinforcement on a biocompatible Ti-30Zr-10Ta alloy produced by powder metallurgy for biomedical applications. This research focused on understanding the influence of boron content (0 to 5 wt.%) on the microstructure, mechanical properties, and tribological behavior of the alloy. The main results showed that increasing boron additions progressively decreased the relative density of the sintered samples. Microstructural analysis via X-ray diffraction (XRD) revealed that the base Ti-30Zr-10Ta alloy exhibited a dominant β-Ti phase with the presence of orthorhombic α″ martensite. The addition of boron led to the in situ precipitation of various borides, specifically TiB, TiB₂, TaB, and TaB₂. Further characterization revealed that the microhardness was enhanced up to 19.6% with lower boron additions, maintaining the elastic modulus of the alloys. Tribological tests demonstrated a significant improvement of 25.7% in wear resistance because of the reinforcement with lower amounts of boride particles. However, higher amounts of boron resulted in a reduction in hardness and elastic modulus at the surface level of 47.2 and 49.3%, respectively, an increase in porosity, and the formation of three-body particles, which contributed to more severe wear and decreased more than twice the wear resistance of the alloy. This research successfully determined the threshold value in a maximum of 0.5 wt.% of boron additions for in situ reinforcement of a biocompatible Ti-30Zr-10Ta alloy suitable for load-bearing applications. Full article

Thermochemical energy storage (TCES) has gained significant attention as a high-capacity, long-duration solution for renewable energy integration, yet material-level challenges hinder its widespread adoption. This review for the first time systematically examines recent advancements in nano-engineered composite thermochemical materials (TCMs), focusing on their ability to overcome intrinsic limitations of conventional systems. Sorption-based TCMs, especially salt hydrates, benefit from nano-engineering through carbon-based additives like CNTs and graphene, which enhance thermal conductivity and reaction kinetics while achieving volumetric energy densities exceeding 200 kWh/m³. For reversible reaction-based systems operating at higher temperatures (250–1000 °C), the strategies include (1) nanoparticle doping (e.g., SiO₂, Al₂O₃, carbonaceous materials) for the mitigation of sintering and agglomeration; (2) flow-improving agents to enhance fluidization; and (3) nanosized structure engineering for an enlarged specific surface area. All these approaches show promising results to address the critical issues of sintering and agglomeration, slow kinetics, and poor cyclic stability for reversible reaction-based TCMs. While laboratory results are promising, challenges still persist in side reactions, scalability, cost reduction, and system integration. In general, while nano-engineered thermochemical materials (TCMs) demonstrate transformative potential for performance enhancement, significant research and development efforts remain imperative to bridge the gap between laboratory-scale achievements and industrial implementation. Full article

Antimony (Sb) is a key material in high-capacity potassium and sodium batteries, particularly in the fabrication of Sb–carbon composites. In this work, nanoscale Sb powder was synthesized directly from SbCl₃, using Al powder as a reducing agent. The reduction process was carried out by gradually adding Al powder to an SbCl₃—acetone solution under continuous cooling and stirring, owing to the highly exothermic nature of the reaction. Acetone was found to be an effective solvent, enabling the formation of Sb nanoparticles with an average particle size of 50 nm and a crystallite size of 25 nm. The purity of the produced powder was nearly 100%, as confirmed via SEM/EDS and XRD analyses. XRD patterns of both commercial and synthesized Sb powders displayed identical and ideal Sb reflections, while FTIR spectra further confirmed their structural similarity. Sintering studies revealed relative densities of 99% for pellets prepared from both commercial and synthesized powders. SEM/EDS examinations of the raw powders and sintered pellets provided complementary microstructural and compositional insights. Overall, this study demonstrates the feasibility of producing high-purity nanoscale Sb powder through a simple, single-step redox process that is both cost-effective and efficient. Full article

Copper matrix self-lubricating composites are critical for high-temperature industrial applications. In this study, Cu-Ni-Sn-Mo-Gr composites with 3–7 wt.% graphite were fabricated via spark plasma sintering (SPS). The influence of graphite content on microstructure, mechanical properties, and tribological behavior from room temperature (RT) to 500 °C were systematically investigated. The results demonstrate that increasing graphite content progressively reduces density, hardness, and yield strength, whereas it significantly enhances high-temperature tribological performance. The composites with 7 wt.% graphite addition achieve outstanding self-lubricity and wear resistance across the RT-500 °C, achieving an average friction coefficient of 0.09 to 0.21 and a wear rate of 1.32 × 10⁻⁶ to 7.52 × 10⁻⁵ mm³/N·m. Crucially, temperature-dependent lubrication mechanisms govern performance: graphite-dominated films enable friction reduction at RT, while synergistic hybrid films of graphite and in situ-formed metal oxides (Cu₂O, CuO, NiO) sustain effective lubrication at 300–500 °C. Full article

This study investigates the use of preliminary thermochemical activation in a NaHCO₃ solution under elevated pressure and temperature to modify the chemically stable and hard-to-process phase composition of various mineral raw materials and improve the recovery of valuable components. The method was tested on various types of mineral raw materials, including slag from the reductive smelting of red mud from alumina production prior to acid leaching, ash before chemical beneficiation, gibbsite–kaolinite bauxite prior to gravity separation, and nephelines, for which the sintering process was replaced with chemical beneficiation. The slag from the reductive smelting of red mud was also tested before acid leaching. The activation of slag enhanced tricalcium silicate formation lead to leaching recoveries of ~96% for rare earth elements, ~92% for TiO₂, ~98% for CaO and Al₂O₃, and 50% for Fe₂O₃, compared to much lower values without activation. With ash, activation eliminated the sillimanite and hedenbergite phases, increased mullite and free silica, and formed calcite, resulting in a 15–20% higher silica recovery. With gibbsite–kaolinite bauxite, activation altered kaolinite, siderite, quartz, and hematite contents; eliminated calcium silicate; and improved the silicon modulus of the sand fraction by 35.9% during gravity beneficiation. For nepheline ore, activation promoted the formation of albite and hydrosodalite, eliminated corundum and andradite, and increased silica recovery from 33.58% to 59.6%. These results demonstrate that thermochemical activation effectively transforms mineral structures and significantly improves the efficiency of subsequent beneficiation processes. Full article

This study examines the influence of vanadium carbide (VC) on the physical and mechanical properties of SiC–VC composites fabricated by a modified spark plasma sintering (SPS) method at a uniaxial pressure of 45 MPa. It was found that the addition of 40 wt.% VC into the SiC matrix led to a substantial reduction in porosity from ca. 30% to less than 8.2% and caused enhancement of the properties. Fracture toughness increased from 2.9 to 7.0 MPa·m^1/2, and hardness rose from 2.9 to 22.6 GPa. In the SiC–VC system, vanadium carbide acted as a grain growth inhibitor and particulate reinforcement. A sintering temperature increase from 1900 °C to 2000 °C resulted in a ~70% improvement in hardness and a ~50% gain in fracture toughness. The results highlighted the critical balance between densification parameters and microstructural stability. Utilization of n-dimensional vector space of material features, Mahalanobis distance, and Pareto trade-off optimization helped to describe the features of the newly obtained composites and to optimize the manufacturing process. Full article