Search Results (7,048)

In this paper, we experimentally investigated the integrated processing of high-iron Kazakh bauxites by reducing smelting of ore–coke–lime briquettes to produce an Fe-Al-Si metallic alloy, which is of potential interest for steel deoxidation, together with calcium-aluminate slag, which is of potential interest for alumina extraction. Briquettes containing bauxite, metallurgical coke (10–20 wt.%), and freshly calcined lime (10 wt.%, constant) were melted in a muffle furnace at a temperature of 1200–1450 °C. Complete separation of metal and slag was achieved at 1400–1450 °C, whereas at 1200–1350 °C, separation remained incomplete. Changing the coke/bauxite mass ratio in the charge from 0.125 to 0.286 increased the total content of metallic Si, Al and Fe in the recovered metallic product from 77.1 to 98.66 wt.%, according to X-ray fluorescence (XRF) analysis after two-stage magnetic separation; the metallic product obtained with a coke/bauxite ratio of 0.286 in the charge contained 72.8% Fe, 23% Al and 2.86% Si (with minor impurities of Ti, Mn and Cr), while the associated slag was represented mainly by CaO (59.5%) and Al2O3 (34.0%). These slag characteristics indicate its potential suitability for alumina extraction or as a filler for structural concrete. The proposed route represents a potentially low-waste alternative for processing high-iron bauxites that are poorly suited to the classical Bayer process, avoiding the direct formation of red mud and supporting Kazakhstan’s transition toward closed-loop bauxite processing. Full article

Composition design is critical for high-performance transparent LAS glass ceramics. This study investigated the effects of heat treatment temperature and CaO/La₂O₃ ratio at a fixed modifier content on crystallization behavior, network structure, microstructure, and comprehensive properties of LAS glass ceramics. Base glasses with different CaO/La₂O₃ ratios at a fixed modifier content were prepared by melt quenching and subjected to two-step nucleation–crystallization treatment at 700~900 °C. XRD and FTIR analyses revealed that β-quartz solid solution initially precipitated at 700 °C, followed by the formation of petalite and Li₂Si₂O₅ at 750~800 °C, whereas β-spodumene and wollastonite emerged at 850 °C. Increasing temperature promoted crystallization, grain growth, and densification up to 850 °C, while excessive heating resulted in grain coarsening and slight property deterioration. Increasing La₂O₃ content refined the grains and improved density, hardness, and visible light transmittance. In contrast, higher CaO content enhanced network depolymerization, ion migration, and wollastonite precipitation. The C4L6 composition exhibited the best overall performance, achieving a bending strength of approximately 160 MPa at 800 °C and the lowest thermal expansion coefficient of 3.64 × 10⁻⁶ K⁻¹ up to 300 °C, demonstrating an optimal balance among crystallization, microstructural refinement, and phase composition. Full article

Polycaprolactone (PCL) is a widely used biodegradable polyester in tissue engineering, drug delivery, and temporary implant design. While its favorable processability, biocompatibility, and low melting temperature are highly advantageous, its slow and condition-dependent degradation remains a major limitation for precise temporal control in biomedical applications. Despite extensive literature on PCL, a critical knowledge gap remains in linking fundamental molecular chain scission directly to macroscopic structural evolution, mechanical failure, and predictable in vivo device performance. To address this, this review provides a comprehensive synthesis of PCL degradation mechanisms, with a particular emphasis on PCL-bioceramic composites designed for hard tissue engineering. We elucidate the progressive degradation pathway—distinguishing between initial hydrolytic chain scission, oligomer formation, the generation of low-molecular-weight degradation products, and their subsequent metabolic fate under physiological conditions. Furthermore, this review critically evaluates how fundamental variables—specifically molecular weight, crystallinity, bioceramic fillers, device geometry, and physiological environments—alter degradation kinetics. By connecting molecular weight reduction to subsequent mass loss, thermal behavior, and mechanical deterioration, we establish a framework for understanding how structural reorganization and crystallinity evolution govern material failure. This review bridges the gap between simplified in vitro models and complex in vivo realities, supporting the rational design of composite biomedical devices with tailored, predictable resorption profiles. Full article

The paper presents thermodynamic data for the aluminothermic reaction used to synthesise hybrid composites (Al₃Zr, ZrB₂)/AA6063. AA6063 alloy was used with K₂ZrF₆, KBF₄ and Na₃AlF₆ as precursors. Composites containing 2.5, 5, 7.5 and 10% wt.% ZrB₂ were produced by direct melt reaction at 900°C and characterised by optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The effect of the salt addition level on the resulting structures is also reported. The compressive behaviour was evaluated at room temperature to an engineering strain of 75% and complemented by tensile tests. The mechanical response is non-monotonic with reinforcement content: the flow stress decreases slightly between 2.5 and 7.5 wt.% ZrB₂ and recovers at 10 wt.%, reaching 321.5 MPa at 30% engineering strain against 278.2 MPa for the matrix. The thermodynamic data and microstructural analysis presented here describe the aluminothermic reaction and its effect on the resulting composites. Full article

In the present work, a series of single-source precursors were prepared via a one-pot synthesis strategy using transition metal chlorides, acetylacetone, and hydroquinone as raw materials. The molecular structure, cross-linking behavior, and polymer-to-ceramic transformation of the obtained precursors were systematically investigated by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The phase composition, phase-transformation temperature, and grain size of the resulting ceramics were characterized by X-ray diffraction combined with Rietveld refinement. The resulting precursors exhibit good solubility in common organic solvents (e.g., ethanol, propanol, and acetone), rendering them suitable for fabricating ultra-high temperature ceramic matrix composites through polymer infiltration and the pyrolysis method. At 1400 °C, the ceramic yields of the TaC, HfC, ZrC, NbC, and TiC precursors were 62.45%, 57.53%, 48.55%, 45.53%, and 30.32%, respectively. After heat treatment at their respective phase-transformation temperatures, the resulting ceramics exhibited grain sizes of carbides in the range of approximately 80–100 nm. The mechanism governing the different phase-transformation temperatures (T) of the derived ceramics, which follow the order T_NbC < T_TaC < T_TiC < T_HfC < T_ZrC, was elucidated through combined thermodynamic and kinetic analyses. This synthesis strategy was extended to the family of ultra-high temperature refractory metal carbides with melting points exceeding 3000 °C, demonstrating promising application potential for ultra-high temperature ceramic matrix composites. Full article

Rubber compounds intended for Mars exploration missions must remain elastic at extremely low temperatures while being manufactured in a reliable and energy-efficient manner. In this study, the effect of vulcanization temperature (100–160 °C) on the network structure and properties of butadiene/silicone rubber (BR/VMQ) blends was investigated, comparing a conventional sulfur curing system (REF) with the same system activated by fluoride anion obtained from tetra-n-butylammonium fluoride (TBAF). The fluoride anion acts as an in situ activator of elemental sulfur, through the opening of the S₈ ring, facilitating the crosslinking process at significantly lower temperatures. Fluoride enabled rapid vulcanization at 100–120 °C, shortening the optimum cure time from 129.1 min to 61.4 min at 100 °C and from 36.7 min to 16.9 min at 120 °C. Equilibrium swelling and thiol-amine analysis revealed opposite structural responses to lowered curing temperature: the crosslink density of the reference compounds increased (from 1.25 × 10⁻⁴ to 1.56 × 10⁻⁴ mol/cm³ between 160 °C and 120 °C), whereas that of the TBAF-containing compounds decreased (from 1.32 × 10⁻⁴ to 0.60 × 10⁻⁴ mol/cm³ between 160 °C and 100 °C), yielding networks dominated by elastic polysulfidic crosslinks (up to 97.2%). We attribute this to a suppressed crosslink maturation under conditions of reduced thermal energy and shortened curing time. Low-temperature curing also suppressed the crystallization of the VMQ phase (melting enthalpy decreasing from 1.23 J/g to 0.21 J/g for TBAF compounds), which we hypothesize results from insufficient energy for phase separation and regular chain packing in this strongly immiscible blend. TBAF-cured compounds exhibited lower tanδ peaks, a stable tanδ plateau between approximately −60 °C and +20 °C, a tanδ-peak shift towards lower temperatures with decreasing curing temperature, and higher elongation at break and tensile strength at −40 °C. The results show that low-temperature, fluoride-activated vulcanization is a promising route for tailoring BR/VMQ networks towards stable dynamic performance across the Martian daily temperature range. Full article

PGM (platinum-group mineral) melt inclusions set in two Pt-Fe alloy nuggets are from the Camumbi River placer, Ecuador. Inclusion bulk compositions are strongly fractionated, mutually exsolved melts Pt–Rh–Pd–Cu > Fe–Ni sulfide-rich and Pt–Cu–Rh ≈ Pd > Fe–Ni telluride-rich respectively, with metal/ligand ratios ~1. They are related to a higher T melt inclusion bulk composition Fe–Cu–Pt >>> Pd > Rh–S also a monosulfide. We use increasing Me/S,Te mineral ratios of inclusion PGM to define each inclusion PGM paragenesis. In the S-rich inclusion, skeletal cuprorhodsite crystallized first with co-exsolved Pt-Fe alloy upon cooling. Next crystallized are braggite, vysotskite, Pt-Fe alloy and oosterboschite. Last crystallized minerals are phase (Pd,Pt)₃(S,Se,Te)₂ and keithconnite (similar synthetic phases are stable at ~350 °C). Within the Te-rich S-bearing inclusion, cooperite first crystallized at high T (~1100 °C) from a subordinate, exsolved S-rich melt. The co-exsolved Te-rich melt next crystallized rare interstitial PGM Rh-bearing mitrofanovite, Rh-bearing moncheite, Rh-bearing monchetundraite, hongshiite, and six minor PGM. Experimental mitrofanovite and moncheite are stable at high T while monchetundraite is stable ~350 °C. We suggest that Rh-bearing mitrofanovite and Rh-bearing monchetundraite could form separate solid solution series with variable Pt–Rh and Ni–Rh respectively. Rh-bearing moncheite indicates a solid solution series with end-member UM (unnamed mineral) Rh(Te,Bi)₂ reported from Ethiopia. Six minor PGMs with extreme compositions are identified by phase mapping using pixel counts combined with BSE (backscattered electron) images. They are stable at lower T hydrothermal conditions and compare with pyrrhotite and pentlandite breakdown products of high T experimental MSS (monosufide solid solution). We suggest the inclusions represent decompression melts formed in the apices of ascending unknown Alaskan–Uralian-type intrusion(s)/volcanics within the Cretaceous Naranjal accreted arc terrane. The melt inclusions are late-formed in the long-fractionating history of this previously defined ore system, and lack detectable As, Sb and Bi suggesting exsolution of higher temperature melts. Full article

High-modulus asphalt binders (HMABs) are critical for heavy-duty pavements but are often constrained by low-temperature brittleness and poor dispersion of conventional granular modifiers. This study develops a novel micro-pulverized composite modifier (ZY) integrating hard asphalt, an ethylene–propylene copolymer, and a plasticizer system via high-shear melt blending and centrifugal atomization. The modification effects and underlying mechanisms were systematically investigated through rheological characterization (DSR, BBR, LAS), thermodynamic analysis (DSC), chemical functional group evaluation (FTIR), and microscopic morphological observation (FM), with two commercial high-modulus agents (PR and JK) as benchmarks. The results demonstrate that ZY significantly enhances high-temperature deformation resistance, elevating the Performance Grade from PG 64-22 to PG 82-10, with the complex modulus (G*) consistently exceeding those of PR and JK across the entire temperature sweep range (46–82 °C). At low temperatures, the synergistic toughening effect of the elastomeric copolymer and plasticizer enables a creep stiffness S of 240 MPa and an m-value of 0.298 at −12 °C, satisfying Superpave requirements and ensuring superior stress relaxation capability. The LAS test reveals a fatigue life of 245,000 cycles at 2.5% strain level, representing an approximately 60% improvement over the JK-modified binder. Microscopic characterization (DSC, FTIR, and FM) confirms that the modification mechanism is dominated by physical blending, forming a highly uniform micro-scale multiphase dispersion system: the hard asphalt component integrates into the matrix to achieve viscosity enhancement and stiffening, while the elastomeric copolymer forms finely dispersed spherical microspheres that effectively impede crack propagation and dissipate strain energy. This synergistic design achieves a favorable balance between high-temperature modulus and low-temperature flexibility, offering a promising solution for durable and rut-resistant pavement applications. Full article

Conventional casting of high-entropy alloys was constrained by multi-principal element solidification behavior and was prone to severe grain boundary segregation and microstructural inhomogeneity, limiting their service performance in extreme environments. Bridgman directional solidification can help to achieve oriented columnar grain growth and mitigate micro-segregation via tailored matching of a temperature gradient, G, and a growth rate, V, yet its stable solidification relied on a high G/V ratio, imposing stringent requirements on equipment and process control. Trace rare earth elements are suggested to potentially stabilize the interfacial morphology and effectively broaden the processing window of Bridgman directional solidification through melt purification and modulation of the solid–liquid interfacial energy based on extrapolation from conventional casting and thermodynamic principles; however, direct experimental confirmation in Bridgman-processed HEAs remains scarce. This review summarizes the solidification microstructure evolution of high-entropy alloys fabricated by the Bridgman method, elucidates the regulatory mechanisms of rare earth microalloying on phase selection, solute partitioning behavior, and interface stability, and reveals the strengthening effects and corrosion performance variations under the synergistic interaction of processing parameters and chemical compositions. Finally, future perspectives are provided regarding interfacial reactions, compositional homogeneity control, and the lack of design criteria in Bridgman-based rare earth composite fabrication systems. Full article

Continuous thermal monitoring of aluminum electrolysis cells—which operate at ~950 °C under strong magnetic fields in a corrosive fluoride melt—remains an unsolved process monitoring challenge. This paper presents a fiber-optic Raman distributed temperature sensing (DTS) deployment for high-temperature cathode steel bar monitoring in a 380 kA industrial cell supplied by a grid with over 30% wind and solar penetration. A custom fiber ring packaging scheme, pressed against the underside of the cathode bar (temperature > 300 °C), achieved >1 m thermal contact length within the confined space beneath the cell. Features encoding supply-side renewable power periodicity, thermal inertia, and local fluctuation intensity were engineered to anchor the learning task in the process physics of the electrolysis cell. CatBoost, LightGBM, and Random Forest were combined in a stacking ensemble with a linear regression meta-learner, attaining RMSE = 0.7451 °C and R2 = 0.9944 over two months of continuous industrial operation across seven cathode bars. Frequency-domain residual decomposition revealed why LightGBM—the aggregate-weakest base learner—received the dominant meta-learner weight (+2.15) while CatBoost—the aggregate-strongest—received a negative weight (−1.85): LightGBM uniquely minimized high-frequency error (1.06 vs. 1.29 °C for CatBoost). The ensemble advantage was spatially robust across all seven bars. The 0.75 °C RMSE establishes a noise floor for residual-based monitoring, demonstrating that process-informed feature engineering and frequency-resolved stacking ensemble learning deliver predictive accuracy suitable as a process monitoring baseline in high-temperature industrial environments under increasing renewable power penetration. Full article

This work is devoted to the investigation of rare-metal granites associated with anorthosite–rapakivi granite rock complexes. This article evaluates the physicochemical conditions that governed the formation of a rare-metal granite dike. It also explores assumptions regarding the geological characteristics of the magmatic chamber, describes evidence for liquid immiscibility, and addresses the post-entrapment evolution of hydrosilicate liquids. In addition, new mineralogical data are presented. The methods employed include optical and electron microscopy, Raman spectroscopy, secondary ion mass spectrometry, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), melt inclusion homogenisation experiments, and fluid inclusion study. The investigated granitic dike formed under low pressure (60–110 MPa) and temperatures of about 580–600 °C, from a specific volatile-saturated magma rich in H₂O (up to 16.76 wt% in quenched hydrosilicate liquid products) and in F (up to 4.16 wt%) and Li (up to 3804 ppm), as indicated by homogenised melt inclusions. At the time of emplacement, a silicate melt, a probable Ca-fluoride melt, an Mg-Fe Al-Si-rich hydrosilicate liquid (either mutually soluble with or mixed with the inferred Ca-fluoride melt), and an essentially aqueous fluid coexisted. Depolymerisation of the silicate melt and the presence of complex ions probably promoted the dissolution and transport of high field strength elements (HFSE) and large ion lithophile elements (LILE) elements by the Mg-Fe Al-Si-rich hydrosilicate liquid. During the final stage of evolution of the granitic magmatic system, Mg behaved incompatibly because of its negligible partitioning into mica; rather than accumulating in the silicate melt, it entered the hydrosilicate liquid as a major component. The residual silicate melt consequently attained even lower Zr/Hf, Nb/Ta, and Y/Ho ratios than the studied rock. Full article

This study systematically investigates the effects of infiltration temperature (800 and 1000 °C) and magnesium (Mg) content (0, 5, and 10 wt.%) on the density, morphology, and chemical composition of silicon carbide/aluminum-magnesium (SiC/Al–Mg) composites. Poor wettability between molten Al and SiC can restrict the infiltration of porous SiC preforms. Although Mg is commonly used to improve wettability, the combined effects of Mg content and infiltration temperature have not been investigated for composites produced from binder-jetted SiC preforms. Porous SiC preforms were first fabricated by binder jetting of SiC powder and then air-assisted oxidation bonded at 1200 °C for 2 h. The oxidation-bonded preforms were subsequently spontaneously melt infiltrated under an inert atmosphere using either pure Al powder or Al–Mg powder mixtures containing 5 or 10 wt.% Mg. The results showed that composite density increased consistently with increasing Mg content. At 800 °C, the density increased from 1.73 to 2.63 g/cm³ as Mg content increased from 0 to 10 wt.%. Similarly, at 1000 °C, the density increased from 1.80 to 2.73 g/cm³. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to evaluate phase formation and microstructural features. The results confirmed effective infiltration in Mg-containing samples, while samples without Mg showed limited infiltration at both temperatures. A two-way ANOVA showed that Mg content was the primary factor controlling post-infiltration density, while infiltration temperature had a smaller but statistically significant effect. These findings provide practical guidance for selecting Mg content and infiltration temperature during the fabrication of binder-jetted SiC/Al–Mg composites. Overall, this study highlights the importance of Mg-assisted infiltration for fabricating binder-jetted SiC/Al–Mg composites and provides processing insights relevant to their potential use in aerospace, automotive, and defense applications, subject to further evaluation of their mechanical and functional properties. Full article

Ultrasonic bonding offers a promising alternative to traditional sewing and other plastic bonding techniques, with several potential advantages. This paper comprehensively analyzes ultrasonic bond characteristics in PVC-coated hybrid textiles, prevalent in awnings and camping tents. Untreated samples were used as controls to compare the effects of ultrasonic bonding on various characteristics. Developed experimental designs were applied using a 12 mm welding width in a lapped seam, with carefully selected parametric levels to achieve higher bond strength based on preliminary test results. Mechanical properties (tensile, cyclic, and tear strength, including thickness reduction) were thoroughly examined to assess ultrasonic bond seam efficiency. The analysis covered thermal, chemical, morphological, and weight loss aspects before and after ultrasonic welding. Results showed that the weld seam tensile efficiency ranged from 68.27% to 96.13%, indicating enhanced durability. Cyclic efficiency exceeded 95%, tear efficiency surpassed 70%, and both treated and untreated samples showed strengths above standard thresholds. Thermal findings indicated a 3% increase in crystallinity after ultrasonic treatment, enhancing thermal stability with lower weight loss and causing shifts in glass transition and melting temperatures. FTIR spectra revealed that ultrasonic bonding had no significant impact on the material’s chemical properties. Morphological analysis identified pre-existing microvoids, with no significant increase in their number and/or size following ultrasonic treatment. Overall, the study demonstrates the efficacy of ultrasonic welding in improving the mechanical, chemical, and thermal properties of PVC-coated hybrid textiles, providing valuable insights for applications like awnings, camping tents, and roofing materials for short- and long-term use. Full article

Phase change thermal storage tanks are important components of clean energy heating systems, and their charging performance depends strongly on storage-unit geometry and heat transfer fluid (HTF) conditions. This study develops a two-dimensional numerical model of a hexagonal honeycomb phase change storage unit and investigates the effects of cell number, HTF inlet temperature, inlet velocity, and fluid type under an approximately constant PCM inventory. Compared with the 4-cell configuration, the 9-, 16-, and 25-cell units reduce the times required to reach an average liquid fraction of 0.8 by 58.3%, 73.9%, and 83.5%, respectively. At 9000 s, the total stored heat of the 25-cell unit is 106.0% higher than that of the 4-cell unit. Increasing the inlet temperature from 338 K to 343 K and 348 K reduces the complete melting time by 27.4% and 42.5% and increases the total stored heat by 14.6% and 26.9%, respectively. An inlet velocity of 0.01 m/s provides the best thermal charging performance, while further increases cause slight deterioration. Water performs best, although differences among the three HTFs remain small. These results provide a quantitative basis for honeycomb PCM storage-unit design. Full article

The mechanical properties of continuous-fiber-reinforced composites in FDM-3D printing are significantly influenced by process parameters. However, research in this area is constrained by printing equipment, control software, and material preparation. This study examines how the tensile and interlaminar shear properties of CCF/PA and CF/PEEK are affected by continuous-fiber nozzle temperature, platform temperature, and printing speed. Studies indicate that enhancing the nozzle temperature can notably improve mechanical properties by enhancing material flowability, ensuring consistent fiber encapsulation and reducing pore defects. Increasing the platform temperature initially boosts both tensile strength and ILSS, but, beyond a certain point, these properties decline. Inadequate platform temperature can result in uneven infiltration and diffusion among deposited CCF/PA paths, leading to void defects. Conversely, excessive platform temperature can cause semi-molten CCF/PA layers to be vulnerable to nozzle pressure and scraping, resulting in continuous-fiber debonding and interlayer tearing. Furthermore, lower printing speeds extend the melt wetting time between adjacent paths, promoting diffusion and adhesion for enhanced performance. Following an experimental investigation, the optimal parameters are identified as a nozzle temperature of 295 °C, a platform temperature of 240 °C, and a printing speed of 3 mm/s. This research provides valuable guidance for the practical production of continuous-fiber-reinforced composites using FDM-3D printing. Full article