Search Results (3,265)

The effect of Mn addition on the structural, dielectric, ferroelectric, and mechanical properties of Bi_0.5Na_0.5TiO₃ (BNT) and 0.94(Bi_0.5Na_0.5TiO₃)–0.06(BaTiO₃) (BNT–BT) ceramics was systematically investigated under identical processing conditions. Powders were calcined at 750 °C for 2 h and 900 °C for 2 h, followed by sintering at 1060 °C for 5 h. Mn contents of 0.5 and 5 mol% were selected to represent low-level substitution and near-saturation regimes. XRD confirmed single-phase perovskite formation within laboratory detection limits, while Raman spectroscopy revealed Mn-induced lattice distortions. Low Mn addition (0.5 mol%) enhanced densification and improved remanent polarization in BNT–BT (Pr = 33.5 μC/cm²). In contrast, 5 mol% Mn promoted grain coarsening, increased porosity, and reduced functional performance. Mechanical properties evaluated using two-parameter Weibull statistics showed composition-dependent variations in characteristic hardness and elastic modulus. The results demonstrate that Mn-doping effects depend strongly on both dopant concentration and host-lattice structural state, distinguishing beneficial substitution from defect-saturation behavior in lead-free BNT-based ceramics. Full article

Al₂O₃-Cu ceramic-metal composites containing 2.5 vol.% of a metallic phase were fabricated using the Pulse Plasma Sintering (PPS) method in order to evaluate the influence of sintering temperature on densification, microstructure, and mechanical performance. Consolidation was carried out at 1200 °C, 1250 °C, 1300 °C, and 1400 °C under uniaxial pressure with a short sintering time of 3 min. Regardless of the processing temperature, all composites exhibited very high relative densities exceeding 99% of the theoretical value, indicating the high efficiency of PPS in densifying Al₂O₃-Cu systems while suppressing copper leakage. X-ray diffraction confirmed the presence of only two phases, Al₂O₃ and Cu, with no secondary reaction products. Microstructural observations revealed irregular copper particles and areas of dispersed metallic phase, whose proportion decreased with increasing sintering temperature due to accelerated matrix densification and copper immobilization. Grain growth in the alumina matrix was strongly temperature-dependent, with the average equivalent grain diameter increasing from 0.49 µm at 1200 °C to 2.35 µm at 1400 °C. Hardness decreased from 19.5 ± 2.8 GPa to 12.2 ± 1.6 GPa with increasing temperature, whereas fracture toughness reached a maximum of 5.42 ± 0.65 MPa·m0.5 at 1400 °C. The highest strength under monotonic compression conditions was obtained for samples sintered at 1300 °C, indicating an optimal balance between densification and microstructural coarsening. These results demonstrate that PPS is an effective method for producing dense Al₂O₃-Cu composites with tailored microstructure and mechanical properties. Full article

Eutectic alloys stand out for their ability to combine high strength and good ductility; a behaviour rooted in their characteristic two-phase microstructure—lamellar or globular—formed at a constant solidification temperature that minimizes segregation and suppresses brittle phases. Their low interfacial energy limits microcrack propagation, while interfacial sliding and dislocation blocking at phase boundaries enhance both strength and toughness. In this work, we investigate how controlled microstructural modifications influence the behaviour of the eutectic high-entropy alloy AlCoCrFeNi2.1, composed of B2 (Ni–Al-rich) and L12 (Co–Fe–Ni-rich) phases. Because these phases exhibit distinct mechanical responses, microconstituent morphology becomes a design parameter. Powder metallurgy is the only processing route capable of providing the level of microstructural control required in this study. It preserves the rapidly solidified eutectic architecture of gas-atomised powders while allowing its intentional transformation during consolidation. Two strategies were implemented: (i) tuning the thermal–electrical input in Spark Plasma Sintering (SPS) and Electrical Resistance Sintering (ERS), and (ii) engineering the particle size distribution, including a bimodal design that enhances surface-energy-driven morphological transitions. SPS enables a gradual lamellar-to-globular evolution, whereas ERS induces ultrafast transformations governed by current intensity. The bimodal PSD significantly accelerates globularisation at lower energy input. EBSD-KAM (Electron Backscatter Diffraction—Kernel Average Misorientation) mapping identifies the lamellar B2 phase as metastable and highly strained, while globular B2 domains show reduced dislocation density. Nanoindentation confirms that intrinsic phase properties remain unchanged, whereas microhardness scales with morphology and lamellar spacing. These results demonstrate that the macroscopic mechanical response is governed by microstructure, establishing powder metallurgy as a uniquely powerful pathway for microstructure-driven design in eutectic HEAs. Full article

Ferronickel slag, as a major solid waste in the stainless-steel industry, poses a serious threat to the environment due to its large-scale production and low utilization rate. In this study, magnesium oxide in the ferronickel slag was leached out and converted into high-purity magnesium sulfate, while the leach residue was utilized for cement clinker production. During the complete utilization of ferronickel slag, the Mg leaching efficiency reached 90.75% and was significantly enhanced by reducing the particle size of the ferronickel slag with H₂SO₄ solution as the sole solvent. High-purity magnesium sulfate with a purity of 99.92% was prepared from the leachate through a multi-step process involving primary crystallization, purification, and secondary crystallization. The leach residue, accounting for 68.20% of the original mass, was primarily composed of 79.4 wt% SiO₂ and less than 6.1 wt% MgO and is used as a key raw material in the production of Portland cement. Sintering temperature significantly influenced the structure and properties of the resulting cement. Both the Portland clinker and cement were successfully produced at sintering temperatures of 1400 °C and 1450 °C when the leach residue was used as a primary raw material, with well-developed cementitious phases of calcium silicate and aluminate formed during calcination. The setting time, soundness, and compressive and flexural strengths of the hardened C1400 and C1450 mortars met the requirements specified in relevant standards. Through this integrated process, the overall utilization rate of the ferronickel slag reached 100%. Based on a preliminary estimate, full utilization of the annual ferronickel slag production in China could substitute at least 19.5 million tons of magnesite and 15.0 million tons of silica and reduce CO₂ emissions by 10.3 million tons. Full article

The integration of sustainable and natural waste-derived materials into lightweight metals presents a promising strategy with both environmental and performance-related benefits. In this study, a biobased magnesium composite reinforced with dried leaf powder (DLP) derived from fallen waste leaves was synthesized using a controlled powder metallurgy method incorporating energy efficient hybrid microwave sintering, followed by hot extrusion at varying temperatures (350 °C, 250 °C, 150 °C). Microstructural analysis revealed that the addition of DLP had minimal effect on the overall grain morphology, while lower extrusion temperatures promoted finer grains due to restricted grain growth. Mg–5DLP composites consistently exhibited higher porosity than pure Mg, primarily due to the evaporation of organic constituents during sintering. The damping performance of the biomass-containing materials was improved (54.5% increase), particularly at lower extrusion temperatures (250 °C), though mechanical performance showed a trade-off with reduced hardness and compressive strength. A slight increase in yield strength at lower extrusion temperatures was attributed to retained dislocation density and grain refinement. Thermal stability remained largely unaffected, while corrosion behavior was strongly dependent on both DLP addition and extrusion temperature, with Mg–5DLP samples corroding faster than pure Mg when extruded at higher temperatures; interestingly, however, at the lowest extrusion temperature (150 °C), improved corrosion resistance to pure Mg (1.3 mm/year for Mg-5DLP vs. 2.0 mm/year for pure Mg) was observed. Overall, this work demonstrates that extrusion temperature is a critical factor in controlling the microstructure, thermal response, damping response, mechanical behavior and corrosion of biobased composites. The study not only highlights the potential of using direct biomass reinforcement of magnesium to synthesize lightweight, ecofriendly materials, but also lays a strong foundation for future investigations into biobased composite design, processing optimization, and property tailoring. Full article

This paper presents an evaluation of two new approaches to improve the surface quality and the mechanical properties of ceramic parts printed by fused deposition of ceramic (FDC). Dip-coating and aerosol-treatment are performed in order to reduce the staircase effect in the vertical printing direction, which typically represents the weakest orientation in most additive manufacturing processes, particularly in fused filament fabrication (FFF). The post-treatments are applied on two highly filled alumina feedstocks. A commercial aerosol-treatment machine for fused deposition modeling is used with ethanol as solvent. A suspension composition for dip-coating is developed to reduce the surface roughness without compromising the printing resolution. The influence of these post-processing steps on the mechanical properties and surface roughness of the green and sintered parts is investigated using perthometer measurements and four-point bending tests in the vertical build direction on as-processed, aerosol-treated, and dip-coated samples. The mechanical results are compared to extruded strand samples. An improvement in surface quality is achievable by dip-coating despite reduction in the parts strength, with a reduction of 65% of the R_z values in the sintered state compared to untreated samples. Aerosol-treatment neither improves the surface quality nor the mechanical properties of the parts. The feedstock and post-processing steps developed in this research aim at printing dense ceramic parts with high surface quality, serving as a basis for developing ceramic parts with higher strength. This advancement will facilitate the utilization of FDC in structural and aesthetic design applications. Full article

Materials capable of withstanding extreme environments open promising opportunities for nuclear fusion reactors. In this study, equiatomic CrFeTaVW and CrFeTiVW high-entropy alloys are investigated as interlayer materials between W and CuCrZr. Monte Carlo and Molecular Dynamics simulations predicted a bcc-type structure for both systems. Additionally, the Monte Carlo simulation predicts lower potential energy and a more stable structure for both systems than Molecular Dynamics. For CrFeTaVW, the chemical segregation values are lower in MC than in the MD simulation, whereas for CrFeTiVW, the opposite trend is observed, with MC indicating stronger segregation values. After simulation, the high-entropy alloys were prepared by planetary ball milling, consolidated by spark plasma sintering, and analyzed using X-ray diffraction, scanning electron microscopy, and thermal diffusivity. The experimental results for the milled powders confirmed the formation of a bcc structure in both alloys. The consolidated material revealed a bcc-type structure and an Fe₂Ta Laves phase for the CrFeTaVW HEA, while the CrFeTiVW HEA exhibits two different bcc-type structures. The values of CrFeTaVW and CrFeTiVW thermal diffusivity are between 3.5 and 7 mm²/s, which is consistent with the expected values for high-entropy alloys. Overall, the findings indicate that these HEAs have promising properties that can be used in extreme environments. Full article

Polymer powder bed fusion (PBF) is strongly influenced by powder chemistry and powder state, yet many studies discuss the materials and processing conditions in isolation. This review synthesises the literature using a powder-centred framework that connects polymer chemistry and powder production history to measurable powder descriptors, and then links these descriptors to processing windows, defect mechanisms, and application outcomes. Key descriptors include crystallinity and thermal transitions, additive packages, particle size distribution, morphology, and surface texture. Environmental sensitivities are also considered, including moisture uptake, temperature effects, and optical response. These factors are related to powder spreading, energy absorption, and melt solidification or sintering to explain how flowability, packing density, and melt dynamics govern porosity, lack of fusion, distortion, and degradation. Powder qualification is discussed together with lot-to-lot variability and lifecycle effects, including ageing, reuse, and refresh, using the indicators commonly reported in laboratory and production settings and supported by emerging in situ monitoring. Application case studies are consolidated to illustrate how powder state and process control translate into repeatable qualification targets as polymer PBF moves toward a predictable and transferable manufacturing practice. Full article

Reforming processes are key technologies for the production of hydrogen and synthesis gas from hydrocarbon feedstocks, with steam reforming and dry reforming being the most extensively studied routes. Steam reforming remains the dominant industrial process due to its high efficiency and economic viability; however, its associated CO₂ emissions raise environmental concerns, partially mitigated through an integration with carbon capture and storage technologies. Dry reforming has emerged as an attractive alternative, although it requires high operating temperatures and suffers from catalyst deactivation. Catalyst design is therefore critical for improving process efficiency and stability. Supported metal catalysts, particularly Ni-based systems, are widely employed, with the support material playing a decisive role in metal dispersion, resistance to sintering and coking, and reaction selectivity. Microporous and mesoporous silica-based materials, including zeolites and ordered mesoporous silicas, offer tunable structural and surface properties that enhance catalytic performance. The novelty of this work lies in its holistic approach to reforming catalysis, where the catalytic performance is not discussed solely in terms of active metals, but is systematically correlated with the surface properties, chemical composition, and structural features of silica-based supports. Moreover, this study expands the perspective to alternative and less-explored feedstocks. By considering multiple fuels and support types, the study provides new design guidelines for developing more efficient and sustainable reforming catalysts. Full article

(Zr,Ti)B₂ ceramics with enhanced hardness and fracture toughness were prepared by spark plasma sintering using platelet TiB₂ and irregular ZrB₂ as starting powders. The effects of sintering temperature (1700–1900 °C) and platelet TiB₂ content (0–30 wt.%) on the sinterability, phase composition, microstructure, and mechanical properties of the (Zr,Ti)B₂ ceramics were investigated. With increasing sintering temperature, the relative density of the solid solution increased from 89.9 ± 0.5% at 1700 °C to 97.7 ± 0.4% at 1800 °C, followed by no significant change upon further temperature elevation; however, the relative density showed an initial increase and subsequent decrease with increasing TiB₂ content. Under optimized parameters (1800 °C, 3 min, 50 MPa, with a TiB₂ content of 30 wt.%), (Zr,Ti)B₂ ceramics achieve a maximum hardness of 24.9 ± 1.0 GPa, a fracture toughness of 5.0 ± 0.3 MPa·m^1/2, and a relative density of 96.5 ± 0.5%. The high content of platelet TiB₂ refined the (Zr,Ti)B₂ grain size, reducing the D50 by 25.8% to 1.70 μm compared to the 20 wt.% content. This study provides a novel perspective for the design and preparation of high-performance ceramics. Full article

The sintering process represents a primary source of dust, SO₂, NOx, and CO₂ emissions in steel mills. Utilizing high-grade concentrate with low impurity content can directly reduce slag generation at the source, thereby decreasing fuel consumption and minimizing associated emissions. This study investigated the physicochemical properties, microstructure, and elemental distribution of hematite concentrates (H2 and H3) and H1 sinter fines. Sinter pot tests were conducted to evaluate the effects of blending these two concentrates on sintering performance and key quality indices. Microstructural analysis and quantitative phase composition statistics of the sintered products were performed to elucidate the mechanisms by which these concentrates influence sintering outcomes. Results demonstrated that replacing 33% H1 sinter fines with 33% H2 or H3 concentrates reduced the tumbler index from 73.6% to 68.5% and 73.2%, respectively. The productivity coefficient decreased to 68.5% and 73.2%, while solid fuel consumption increased from 73.9 kg/t to 90.5 kg/t and 81.2 kg/t. RI declined from 80.0% to 77.9% and 78.4%, whereas RDI improved from 72.9% to 76.8% and 75.8%. Full article

New glass-free low-temperature co-fired microwave dielectric composites with compositions (1–4x/3)Ba₃(VO₄)₂–xBaWO₄–(2x/3)Li₃VO₄ (x = 0.3–0.7) were fabricated by reactive liquid-phase sintering of (1–x)Ba₃(VO₄)₂–xLi₂WO₄ mixtures at 850 °C. During sintering, Li₂WO₄ is fully consumed by reacting with Ba₃(VO₄)₂ to form BaWO₄ and Li₃VO₄ while providing a transient liquid phase that promotes densification. As a result, the sintered ceramics achieve high relative densities of ≈94–98% at 850 °C. The relative fractions of Ba₃(VO₄)₂, BaWO₄, and Li₃VO₄ can be systematically tailored by adjusting the initial Li₂WO₄ content, enabling effective control of the temperature coefficient of the resonant frequency (${\tau }_f$) and the quality factor (Q × f). With increasing Li₂WO₄ content, the ${\tau }_f$ values shift from +23.97 to −45.48 ppm/°C, owing to the increasing contributions of the negative ${\tau }_f$ phases BaWO₄ and Li₃VO₄, while the Q × f values increase moderately from 44,300 to 47,300 GHz. The optimal microwave dielectric properties are obtained for x = 0.5, meaning ${\epsilon }_r$ = 9.19, Q × f = 45,900 GHz, and ${\tau }_f$ = −1.15 ppm/°C when sintering at 850 °C for 1 h. Chemical compatibility tests confirmed that the composites exhibit no detectable reaction with Ag electrodes, indicating that the Ba₃(VO₄)₂–BaWO₄–Li₃VO₄ system is a promising glass-free dielectric for LTCC applications requiring low firing temperature, near-zero thermal drift, and reliable electrode compatibility. Full article

The 0.006Pb(Mn_1/3Ta_2/3)O₃-0.114Pb(Ni_1/3Ta_2/3)O₃-0.43PbZrO₃-0.45PbTiO₃ lead-based ceramics (PMT-PNT-PZT) were synthesized via the solid-state reaction at different sintering temperatures to study their effects on phase structure, microstructure, and electrical properties. The maximum mechanical quality factor (Q_m) and relative permittivity (ε_r) were achieved at the sintering temperature of 1200 °C. The piezoelectric constant d₃₃ of 400 pC/N was obtained at 1180 °C, which is attributed to the high grain density and the significant contribution from the remanent polarization and permittivity product (P_rε_r = 39,115 μC/cm²). Compared with commercial PZT4 ceramics, the present composition sintered at 1180 °C exhibits an optimal balance between d₃₃ and Q_m, together with the superior figure of merit (FOM = 2.04 × 10⁵ pC/N). Furthermore, it demonstrates excellent temperature stability in electromechanical coupling performance. Full article

The pantograph slider is a key friction component in high-speed train systems, and its performance directly affects the safety and efficiency of operation. In this study, Cf/C/CuNi composites with carbon fiber contents of 1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% were prepared by a solvothermal method combined with spark plasma sintering (SPS). The influence of carbon fiber content on the mechanical and friction properties of the composites was systematically studied. The results show that the flexural strength of the composites increases from 20.20 MPa to 38.45 MPa with an increase in the carbon fiber content. However, excessive carbon fiber content can lead to fiber agglomeration and interface defects, thereby reducing the friction stability and increasing the wear rate from 0.64 g/m³ to 1.60 g/m³. A carbon fiber content of 1 wt.% helps to form a continuous lubricating film, resulting in a low and stable friction coefficient. This study provides valuable insights for the design and optimization of high-performance pantograph slider materials for high-speed railway applications. Full article

This paper presents a novel approach to modeling and optimizing the mechanical and microstructural properties of 316L stainless steel surfaces manufactured by spark plasma sintering (SPS). The integration of artificial intelligence techniques, particularly artificial neural networks (ANNs), with the optimization of material properties and the spark plasma sintering (SPS) process reflects the growing emphasis on intelligent manufacturing in advanced industrial applications. The surface functionality depends on the material’s mechanical and microstructural characteristics. The optimization technique was developed through the processing of a comprehensive set of measurement data, forming the foundation for the artificial intelligence method. To model the relationships between SPS parameters (sintering temperature and holding time) and material properties (density, porosity, hardness, and surface-affected zone (AKA the possible carbide zone depth), a series of controlled experiments was conducted. The performance of neural network models was evaluated using their coefficients of determination (R² > 0.95) and the sum of squared errors (SSE < 0.02). These metrics were calculated by comparing actual measurement data with values predicted by the models. Validation experiments confirmed the reliability of the presented models and their relevance for implementation in industrial environments. The predictive model is valid for 316L stainless steel within the tested SPS setup and parameter range. Full article