Search Results (395)

Iron-based Fischer–Tropsch synthesis (Fe-FTS) catalysts are central to coal-to-liquid (CTL) processes but suffer from rapid and complex deactivation under industrial conditions. This review critically examines the key deactivation mechanisms, including carbon/wax deposition, hydrothermal sintering, chemical poisoning (S, Cl, As), and mechanical attrition, and evaluates modern regeneration strategies. These strategies include supercritical fluid extraction for wax removal, controlled oxidative decoking, reductive reconstruction of active iron carbides (χ-Fe₅C₂), chemical de-poisoning, and structural upcycling. We also discuss emerging techniques such as non-thermal plasma and supercritical fluid-assisted reactivation. Finally, we highlight challenges in irreversible phase transformation, in -situ regeneration engineering, and economic feasibility, and outline future directions toward regeneration-friendly catalyst design and advanced syngas purification for a circular CTL economy. Full article

This study investigates the effects of waste glass (GL) and silica fume (SF) on the physical, mechanical, and microstructural properties of clay-based ceramic materials produced from low-grade calcite-rich clay loam. Waste glass and silica fume were incorporated at 10–20 wt.%, and the specimens were fired at temperatures ranging from 1050 to 1150 °C. The average density, water absorption, compressive strength, phase composition (XRD), and microstructure (SEM) were evaluated. The results showed that waste glass significantly enhanced the sintering behavior of the ceramic body through liquid-phase formation at elevated temperatures. The average density increased from approximately 1650 to 2200 kg/m³, while water absorption decreased from 6.5% to 3.2%. The optimum firing temperature was 1125 °C, at which the ceramic compositions containing 10 wt.% and 15 wt.% waste glass exhibited no visible deformation and achieved compressive strengths of 32–36 MPa. In contrast, silica fume was less effective as a fluxing additive, resulting in lower strength, increased deformation, and cracking at temperatures above 1100 °C. SEM observations confirmed the formation of a denser, more homogeneous microstructure in the waste glass-modified specimens, while XRD analysis revealed a reduction in quartz content, accompanied by enhanced formation of the diopside and anorthite phases. Among all investigated compositions, the ceramic material containing 10 wt.% waste glass and fired at 1125 °C exhibited the most balanced combination of density, water absorption, and compressive strength, demonstrating its potential for producing high-performance clay-based ceramic materials. Full article

This study aims to develop eco-efficient ceramic tiles through the valorization of recycled glass (GW; soda–lime glass cullet) as a partial raw material substituent, enabling a reduction in sintering temperature and, consequently, a decrease in thermal energy demand, carbon-equivalent emissions, and the depletion of virgin mineral resources. Ceramic tiles were elaborated by partially substituting natural bentonite with 30–50 wt.% GW and fired at 900 °C and 950 °C. Use of GW promoted liquid-phase sintering, driving significant densification evidenced by a marked reduction in open porosity and water absorption. SEM images confirm a denser, more homogeneous structure with reduced porosity, leading to improved mechanical strength and chemical durability. Compositions containing 30–35 wt.% bentonite exhibit the most optimized microstructure, characterized by well-dispersed crystalline phases embedded within a dense vitreous matrix. These findings demonstrate that high-performance ceramic tiles meeting standard classification thresholds can be manufactured at sub-1000 °C firing temperatures through judicious incorporation of recycled glass waste. This approach offers a viable pathway toward reduced energy consumption, diminished reliance on primary mineral resources, and enhanced circularity within the construction ceramics industry. Full article

This study investigates the correlation between sintering temperature, microstructure, and mechanical properties in AlSi10Mg alloy produced by supersolidus liquid phase sintering and subsequent artificial aging. Sintering was performed at 571, 575, and 579 °C using different heating rates for a total duration of approximately 5 h, followed by a 2 h dwell at the sintering temperature. At low sintering temperature, the alloy exhibits relatively fine α-Al grains with uniformly distributed Si precipitates, whereas intermediate temperature promotes Si coarsening. At higher temperature, excessive liquid formation leads to coarse α-Al grains and the development of partially interconnected Si networks. β-Al₅FeSi progressively coarsen with increasing sintering temperature. In the as-sintered state, the modest mechanical properties result from coarse α-Al grain size and subgrain structure, as well as from the size, morphology, and distribution of the Si phase. After aging (at 160 °C for 6 h following solution treatment at 530 °C for 30 min), the hardness and UTS were almost double (going from 44 ± 1 to 103 ± 2 HV and from 121 ± 1 to 273 ± 40 MPa). Meanwhile, α-Al grain size and Si morphology remained unchanged and Fe-rich intermetallics partially transformed into the more stable γ-Al₃FeSi₂ phase. Full article

Steelmaking produces large volumes of slag, a by-product with environmental risks due to accumulation and possible contamination. This study explores its use as a mineralizing agent in chamotte refractories. Slag rich in clinoferrisilite was added up to 5 wt.% to partially replace fine chamotte. Samples were shaped by semi-dry pressing and fired at 1350 °C. Chemical and phase composition, thermal behavior, microstructure, and physico-mechanical properties were analyzed. Results showed slag addition increased mullite content to 68 wt.% and promoted secondary magnesium–aluminosilicate phases (indialite, cordierite), indicating activation of reactions in the MgO-Al₂O₃-SiO₂ system. DSC and TGA revealed thermal effects between 1298 and 1325 °C, confirming slag’s fluxing role and lowering the liquid-phase sintering temperature. Optimal properties were achieved with 5% slag and 10% clay, yielding compressive strength of 24 MPa and apparent density of 2.30 g/cm³, meeting GOST 390-96 requirements for grade SHA. However, excess liquid-phase components reduce thermal stability. Thus, steelmaking slag is an effective secondary raw material, enhancing mullitization and refractory performance when used within controlled limits. Full article

W₂CoB₂ is a ternary boride-based cermet. Featuring high hardness, high melting point, excellent wear resistance and corrosion resistance, it has been widely used in numerous industrial fields such as cutting processing, surface protection and mold manufacturing. Toughening is a major issue that needs to be addressed for ceramic materials. In this study, the toughness of cermets is improved by the combined addition of CNTs and La₂O₃. The W₂CoB₂ cermets were fabricated via vacuum sintering, and the effects of CNTs and La₂O₃ on the microstructure and properties of the cermets were systematically investigated. The microstructure and phase composition of the specimens were characterized using a SEM and X-ray diffractometry (XRD), respectively. The density of the specimens was measured by the Archimedes drainage method. A Vickers microhardness tester was employed to determine the microhardness and fracture toughness of the specimens. The transverse rupture strength was tested using an electronic universal testing machine, while the wear resistance was evaluated via a wear tester. The results indicate that the addition of either CNTs or La₂O₃ can refine the grain size and improve the toughness of the cermets. The simultaneous incorporation of CNTs and La₂O₃ further enhances grain refinement and mitigates the issue of uneven dispersion of CNTs in the specimens. When 0.5 wt.% CNTs and 0.3 wt.% La₂O₃ are added, the specimen exhibits the following optimal properties: a density of 9.33 g/cm³, a microhardness of 2046 HV_0.5, a fracture toughness of 12.36 MPa·m^1/2, a transverse rupture strength of 985 MPa, and a friction coefficient reduced to 0.36. Synergistic addition of CNTs and La₂O₃ achieves grain refinement and uniform microstructure, which significantly improves the friction and wear performance and service stability of the cermet. The material retains high hardness and wear resistance, accompanied by enhanced comprehensive mechanical and service properties. Further studies will aim to cut costs while preserving material performances, facilitating its industrial application. Full article

This study developed a high-iron-phase steel slag-based silicate cement system through high-temperature reconstruction and multi-source solid waste synergistic modification. The effects of reconstruction temperature and Ca/Si ratio on burnability, mineral evolution, microstructure, and hydration performance were investigated. Results showed that carbide slag and bauxite significantly improved the sintering behavior of steel slag. At 1275 °C, the f-CaO content in reconstructed steel slag decreased sharply from 1.45% to 0.11%, while overburning and liquid-phase coating occurred at 1300 °C, hindering further reaction of residual f-CaO. Reconstruction promoted the conversion of low-reactivity γ-C₂S to active α-C₂S and the formation of well-crystallized C₄AF. The decomposition of the RO phase enabled Mg²⁺ and Mn²⁺ to solid-solve into spinel phases, thus improving volume stability. The Ca/Si ratio regulated intermediate phases: higher ratios favored C₄AF, whereas lower ratios promoted spinel or olivine phases. The optimal sample (1275 °C, 65% steel slag + 25% carbide slag + 10% bauxite) achieved a 28 d compressive strength of 107.56 MPa, 18.26% higher than the reference cement, owing to synergistic hydration of α-C₂S and C₄AF. The F4 sample showed the lowest residual CH content (11.31%) and the highest hydration efficiency. Full article

Sintering additives play a decisive role in the densification behavior, mechanical properties, and thermal conductivity of silicon nitride ceramics. In this study, Mg₂Si and YH₂ were used as sintering additives for gas pressure sintering of silicon nitride based on the synergistic mechanism of “silicide silicon extraction-hydride dehydrogenation”. The regulation rules of the additives on ceramic densification, mechanical properties, and thermal conductivity were systematically investigated. Two optimization strategies were proposed for the technical route of replacing traditional oxide additives with non-oxide systems. (i) Rare-earth hydride YH₂ was used to replace traditional rare-earth oxides. It reacts with SiO₂ to achieve strong deoxidation and precisely regulate the liquid phase composition. (ii) Metal silicide Mg₂Si was used to replace metal oxides. It promotes the preferred growth of β-Si₃N₄ grains, consumes oxygen in the system, and reduces lattice defects. Mg₂Si introduces Si into the liquid phase, increasing the Si/O ratio, which lowers lattice oxygen content and supports higher thermal conductivity. YH₂ consumes SiO₂ on the Si₃N₄ surface, which reduces liquid phase oxygen content and inhibits lattice oxygen incorporation, promoting a liquid phase with a high N/O ratio. Compared with traditional Y₂O₃, YH₂ increases the Y₂O₃/SiO₂ ratio in the liquid phase. It promotes grain growth, reduces SiO₂ activity, and further improves the thermal conductivity of ceramics. Silicon nitride ceramics prepared by gas pressure sintering at 1750 °C with 3 wt.% Mg₂Si and 4 wt.% YH₂ composite additives exhibit the highest thermal conductivity of 87 W/(m·K), with a Vickers hardness of 14.36 GPa and a flexural strength of 643.15 MPa. This study provides an innovative idea for the preparation of high-performance silicon nitride heat dissipation substrates. Full article

Simultaneously achieving high densification, excellent mechanical properties, and high thermal conductivity remains challenging for aluminum nitride–silicon carbide (AlN-SiC) composites. In this study, fine-grained AlN-SiC composite ceramics were fabricated via in situ reaction hot pressing with the addition of small amounts of silicon (Si) and carbon (C). At an optimal sintering temperature of 1800 °C, the primary phase composition consisted of AlN, SiC and residual graphite, with an average AlN grain size of 0.94 μm. The Si additive melted and wetted the AlN matrix via capillary action, thereby providing sufficient kinetic driving force for densification. Meanwhile, the C additive not only removed oxygen impurities and purified grain boundaries but also reacted in situ with liquid Si to form SiC. The uniformly dispersed SiC particles inhibited the abnormal growth of AlN grains via the grain boundary pinning effect. Consequently, the relative density, flexural strength, and Vickers hardness of the obtained AlN-SiC ceramics reached 99.08%, 365 MPa and 22.58 GPa, respectively. At room temperature, the composite exhibited a thermal conductivity of 66 W/(m·K) and a thermal diffusivity of 32.6 mm²/s. This superior thermal performance is attributed to the purified grain boundaries, uniform SiC distribution, high densification, and tightly bonded SiC/AlN interfaces, which result in weak phonon interfacial scattering. Full article

This study aims to demonstrate the feasibility of controlling particle size through a mathematical model in the design of industrially applicable ultrasonic spray nozzles by utilizing the vibrational characteristics of piezoelectric ceramics. A piezoelectric ceramic composition with a low sintering temperature and excellent thermal stability (Curie temperature above 300 °C) was developed and used as a ceramic vibrator. Furthermore, the resonance frequency and nozzle displacement were calculated using the COMSOL program and applied to a mathematical model to design an ultrasonic nozzle capable of producing a spray particle diameter of approximately 30 μm. The designed ultrasonic nozzle was fabricated, and its spray characteristics were analyzed. The consistency of the spray characteristics was examined by comparing them with the mathematical model based on changes in ultrasonic nozzle length, resonance frequency, and fluid viscosity. When the ultrasonic nozzle horn length was 22 mm, the resonance frequency was found to be 42.1 kHz, and at a flow rate of 65 mL/min. the average spray particle size was approximately 30–40 μm, indicating fine and uniform particles. In addition, it can be seen that as the length of the nozzle horn increases, the resonance frequency decreases, reducing the supply energy delivered to the liquid, and the particle size increases as shown in the mathematical analysis. The theoretical separation energy required to atomize pure water at a flow rate of 65 mL/min. is 2100 J, which was found to be greater than all energy loss occurring during the atomization process. However, it can be seen that as the length of the ultrasonic nozzle increases, the maximum atomization volume increases, and as viscosity increases, the energy required to separate a single atomized particle becomes greater. Full article

This study aims to develop CoCrMo/xCu composites through liquid phase sintering. The primary focus is on investigating how the addition of copper influences sintering kinetics, microstructure, and mechanical properties. The copper volume fraction ranged from 10 to 25 wt.% relative to CoCrMo. Sintering was conducted at 1150 °C under an argon atmosphere. Characterization methods included scanning electron microscopy, computed microtomography, and X-ray diffraction analysis. It was observed that molten copper, which forms upon reaching its melting temperature, can fill the interparticle spaces left by CoCrMo particles in the green compacts. During sintering, densification is further enhanced by the dissolution of CoCrMo, resulting in the formation of intermetallic phases enriched in Cr and Mo, as well as a ternary Co-Cr-Cu compound. Both densification and intermetallic formation contribute to increased microhardness as Cu content rises. It is concluded that the CoCrMo/25Cu composite exhibits the best mechanical and corrosion properties because its densification was improved by the Cu liquid. Full article

To address the resource waste caused by the ineffective recycling of large quantities of red mud, this study proposes an innovative technical route consisting of red mud sintering followed by smelting in a small blast furnace or solid-waste smelting furnace for pyrometallurgical iron extraction. Under optimized process conditions—binary basicity of 4.97, a raw material composition of 78.27% wet-based red mud, 15.67% quicklime, and 6.05% fuel, with a solid fuel consumption of 121 kg/t—the produced sinter meets the feeding requirements of blast furnace smelting. The results indicate that the liquid phase generated during red mud sintering mainly consists of composite oxides in the CaO–Al₂O₃–SiO₂ system; calcium aluminosilicate (Ca₂Al₂SiO₇) was detected and inferred to be a potential bonding phase in the sinter matrix. Thermodynamic analysis shows that the Gibbs free energy of Ca₂Al₂SiO₇ is lower than that of calcium ferrite, indicating that its formation is thermodynamically more favorable. The formation amount of this phase is closely related to the Ca/Al ratio, while temperature has a limited influence. In addition, Na₂O can react with CaO·2 Al₂O₃ to form a low-melting-point phase, which significantly reduces the sintering temperature and enhances the fluidity of the liquid phase. These findings provide a new theoretical basis for the sintering of high-alumina ores and offer technical support for the efficient utilization of red mud as well as energy conservation and emission reduction. Full article

Cu is widely employed in power device packaging materials owing to its excellent electrical and thermal conductivity, coupled with economic viability. Sintered Cu currently stands as one of the representative interconnect materials in power device packaging. However, it is prone to oxidation during bonding, requires extended bonding times, and needs considerable pressure. Transient liquid phase bonding (TLPB) technology is regarded as a viable solution for power device packaging, enabling high-melting-point, high-strength, and thermally stable connections at low temperatures. Cu and Sn are widely employed metallic materials in common TLP systems. The Sn-coated Cu particle increases the effective reaction area between Cu and Sn, accelerating the formation of intermetallic compounds (IMCs) and reducing bonding time. Sn-coated Cu particles were produced in this study by chemically plating Sn onto micron-sized Cu powder surfaces. The effects of flux content, bonding time, and applied pressure on joint shear strength were investigated. Results indicate that as flux content increases, the shear strength of the solder joints initially increases and then decreases. The shear strength of the solder joint gradually decreased with increasing bonding time, but no significant change was observed when the time exceeded 20 min. Increasing the applied pressure significantly enhanced the shear strength of the solder joint. The shear strength of the solder joint at 10 MPa is 90.2% higher than at 5 MPa. Full article

Droplets impacting heated porous surfaces trigger a complex process involving liquid and vapor penetration, as well as the growth and rupture of internal bubbles. In the current paper, four types of sintered porous substrates with different permeability and surface roughness are used. The droplet impact process on heated porous surfaces is visualized by high-speed photography and image processing algorithms. The boiling phase transition characteristics of propylene glycol–propanetriol binary droplets impact on different heating surfaces and the variation pattern of the number and diameter of secondary droplets splashed during the boiling process were investigated. The results show that the surface properties of the porous medium and the composition of the droplet solution have a large effect on the boiling state of the droplets as well as the number and diameter of the secondary droplets. An elevated proportion of propanetriol in solution makes it difficult for droplets to penetrate porous substrates, and it is more difficult for droplets on substrates with large pore size and roughness to undergo film boiling, with more secondary droplets erupting during boiling. Full article

Printable piezoelectric materials are emerging as a cornerstone of next-generation sensing, actuation, and energy harvesting technologies, driven by the need for lightweight, flexible, and digitally manufactured transducers. Conventional ceramic piezoelectrics offer exceptional electromechanical performance but require high-temperature sintering and exhibit intrinsic brittleness, limiting their integration with soft or unconventional substrates. Polymeric piezoelectrics, in contrast, provide mechanical compliance and low-temperature processability yet suffer from lower crystallinity, reduced piezoelectric coefficients, and limited thermal stability. These contrasting characteristics have catalyzed the development of functional piezoelectric inks—ceramic, polymeric, and hybrid formulations engineered for additive manufacturing techniques such as direct ink writing, stereolithography, screen printing, and inkjet printing. This review systematically examines the material compositions, dispersion chemistries, printing requirements, thermal treatment pathways, and poling strategies that govern the performance of printed piezoelectric transducers. By comparing ceramic-based, polymer-based, and hybrid systems, we reveal the fundamental trade-offs between printability, crystallinity, mechanical compliance, and electromechanical response, and map how these trade-offs shape device design across wearable electronics, soft robotics, and structural health monitoring. Finally, we highlight emerging approaches—including surface functionalization, low-temperature crystallization, liquid-phase sintering, and engineered ceramic–polymer interfaces—that offer promising routes to bridge the gap between printability and high piezoelectric performance. Full article