Search Results (9,562)

This study presents a sustainable approach for processing low-grade lithium-bearing aluminosilicate ores via carbothermic treatment with selective lithium stabilization in the slag phase. The proposed method is based on controlled phase transformations that suppress lithium volatilization and promote its retention in the condensed phases. Thermodynamic analysis revealed that lithium volatilization is unfavorable within a defined temperature window, enabling its stabilization in the slag. Experimental smelting, conducted at 1550–1600 °C with the addition of an iron-bearing component, resulted in the selective reduction of silicon and aluminum into a ferro silicon aluminum alloy, while lithium was efficiently concentrated in the slag phase. Lithium recovery to the slag reached up to 94%, with losses to the gas phase below 6%, demonstrating a significant reduction in volatilization compared to conventional high-temperature processes. X-ray diffraction (XRD) analysis confirmed that lithium is predominantly immobilized in the form of LiAlSiO₄ (pseudo-eucryptite), which enhances the chemical reactivity of the slag. From a sustainability perspective, the proposed process enables efficient utilization of low-grade lithium resources, minimizes lithium losses, and eliminates the need for energy-intensive pre-treatment steps such as roasting or vacuum processing. The resulting lithium-bearing slag represents a reactive intermediate suitable for subsequent hydrometallurgical extraction, enabling an integrated and resource-efficient process route. The results demonstrate that phase-controlled carbothermic processing is a viable and sustainable strategy for lithium recovery from low-grade aluminosilicate ores. Full article

In this study, mullite single-crystal whiskers were prepared by sintering mullite gel powders using HF as a catalyst via the sol–gel process. The effects of the Al₂O₃:SiO₂ molar ratio on the morphology of mullite whiskers in the Al–Si–F system were comprehensively explored during the catalytic reaction. Furthermore, the synergistic effects of the Si:Al ratio and the catalyst content on the growth mechanism of mullite whiskers were evaluated. The morphological characteristics of the whiskers were determined using transmission electron microscopy and scanning electron microscopy. Moreover, morphological parameters, including the diameter and length of whiskers, were statistically analyzed using the Image J software. Additionally, the compositional variation and phase evolution during the whisker growth process were examined via energy-dispersive spectroscopy and X-ray diffraction, respectively, and the corresponding growth mechanism was elucidated. When HF-mediated catalysis reaches a sufficient level (Al₂O₃:SiO₂:HF = 1:1.5:4.3), the low SiO₂ content in the system leads to Al enrichment and the formation of flake-shaped Al₂O₃ structures, indicating an effect analogous to that of increasing catalyst content. Conversely, the simultaneous reduction in the contents of HF and SiO₂ induces different catalytic reactions because of their synergy. Specifically, at relatively low SiO₂ and HF contents, F ions enter the Al–Si–O system via SiF₄, leading to the generation of fluorine-containing topaz, which subsequently transforms into mullite. At relatively high SiO₂ and HF contents, mullite can be directly synthesized via the reaction of AlF3 and SiF₄. With a gradual reduction in the SiO₂ and HF contents, the mullite whiskers exhibit a varying morphology, predominantly transitioning from rod-shaped to flake-shaped and subsequently to rod-shaped structures. This is due to the synergistic effects of the phase transformation and catalytic reactions within the Al–Si–O system. Full article

Chinese Traditional Concrete (CTC), known as “San-he-tu,” has ensured the long-term durability of ancient coastal structures, yet its underlying material design logic remains insufficiently understood. This study investigates the Chongwu Ancient City Wall (Quanzhou, China), a Ming Dynasty granite fortification exposed to over 600 years of marine weathering, to elucidate the structure–property–function relationships of CTC across three functional layers: the horse-track surface, wall core backfill, and masonry bonding layer. A multi-technique analytical framework (XRF, XRD, TG, and SEM) was employed to characterize chemical composition, mineral phases, thermal behavior, and microstructure. Results reveal a deliberate “functional adaptability” material design. The surface layer adopts a rigid protective formulation with high quartz (76.9%) and CaO (17.06%), forming a dense, low-porosity matrix resistant to abrasion and weathering. The wall core exhibits a flexible filling strategy with high porosity (35.44%), enabling moisture dissipation and deformation accommodation. The bonding layer, enriched in kaolinite (~29.8%) and reactive Al–Fe components, promotes pozzolanic reactions that generate hydraulic gels, ensuring durable interfacial adhesion under humid coastal conditions. These findings demonstrate that ancient builders engineered zone-specific material compositions to meet distinct structural and environmental demands, forming a functionally graded system analogous to modern material design concepts. This study provides a scientific basis for adopting partitioned, differentiated restoration strategies in coastal heritage conservation. Full article

This study presents the production of isoamyl, n-butyl and cyclohexyl esters of levulinic acid with an excellent yield under solvent-free conditions. The catalysts used were MgAlO and M²⁺MgAlO-mixed oxides containing the transition metals (M²⁺ = Co²⁺, Ni²⁺, Zn²⁺), obtained from calcined layered double hydroxides (LDH). They are easily accessible, low-cost, and environmentally friendly and possess the requisite acid–base properties for esterification reactions. The effect of reaction time and the molar ratio of levulinic acid to the alcohols used on the esterification reaction was investigated. The catalysts were characterized by X-ray diffraction (XRD), XRF, SEM and temperature-programmed desorption of CO₂ (TPD-CO₂). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. Mixed oxides containing transition metals exhibited significantly higher activity than MgAlO. Under the selected reaction conditions, the conversion of levulinic acid and the yield of isoamyl ester reached 100% at a reagent ratio of 1:1. As a by-product of esterification, only dicyclohexyl ether was found at a reactant ratio of 1:1.5. Full article

This study addresses the corrosion problem of refractory materials during high-temperature molten treatment of pharmaceutical waste salt, and systematically investigates the interface behavior and corrosion mechanism of MgO-based refractory materials in simulated pharmaceutical waste salt (65 wt% NaCl-30 wt% Na₂SO₄-5 wt% CaCO₃). Through sessile drop wetting infiltration experiments, static corrosion tests (950 °C and 1150 °C/48 h), combined with SEM-EDS, XRD characterization, and FactSage thermodynamic calculations, the corrosion resistance of high-purity MgO phase (HM-97) refractory materials and magnesium–aluminum spinel composite phase (MA-85) refractory materials was compared and analyzed. The results show that due to the fine periclase grains and rich grain boundaries, the molten salt infiltration rate of HM-97 material in the 644-800 °C range is significantly higher than that of MA-85. After corrosion at 950 °C, HM-97 and MA-85 formed 47 μm and 53 μm transition layers respectively, and the HM-97 surface generated Ca₃Mg(SiO₄)₂ phase leading to uneven corrosion morphology. At 1150 °C, HM-97 produced long cracks and the transition layer thickness remained almost unchanged due to dissolution, while MA-85 formed an approximately 72 μm transition layer and a dense metamorphic layer. Phase analysis and thermodynamic calculations suggest that the MgAl₂O₄ phase in MA-85 is likely stable at high temperatures, which appears to effectively prevent molten salt infiltration and contribute to forming a protective metamorphic layer, thereby potentially enhancing the material’s corrosion resistance. The MgAl₂O₄ phase is proposed to improve the service performance of MgO-based refractory materials in the molten pharmaceutical waste salt environment. Full article

Significance: This study addresses critical industrial and biomedical applications including glass blowing (thermal management of shrinking sheets), polymer sheet extrusion (controlled cooling), magnetic drug delivery (nanoparticle targeting), and nuclear reactor cooling (enhanced heat transfer). Aim: We present a novel nonlinear analysis of magnetohydrodynamic (MHD) boundary layer flow of a Jeffery Al${}_2$O${}_3$ nanofluid over a shrinking permeable plate with convective boundary conditions, uniquely integrating mixed convection, Ohmic dissipation, heat generation, Brownian motion, and thermophoresis within a non-Newtonian nanofluid framework. Methodology: The governing partial differential equations are transformed using similarity transformations and solved via the Adomian decomposition method (ADM). Comprehensive validation against RK4, RK45, and bvp4c demonstrates excellent agreement with maximum relative errors below $5\times {10}^{-4}$. Key Contribution: (i) Normal velocity decreases by 15–25% as the Biot number increases from $Bi=0.4$ to $0.6$; (ii) tangential velocity decreases by 20–30% as the magnetic parameter increases from $M=5$ to 15; (iii) temperature increases by 30–40% as the Eckert number increases from $Ec=0.5$ to $2.5$; (iv) ADM converges within 12–15 terms with $L_2$ errors $<{10}^{-5}$; (v) skin friction coefficient increases from $C_f=3.02713$ to $3.90082$ as $Q_0$ increases from 1 to 4; (vi) Nusselt number values: $Nu/\sqrt{Re}=0.4621$ at $Pr=0.7$, $0.8954$ at $Pr=2$, $3.2890$ at $Pr=20$. These quantitative findings provide design guidelines for engineers in thermal management and biomedical applications. Full article

Multi-band circular dichroism (CD) with spectral tunability is highly desirable for chiral metasurface-based sensing and polarization control. In this work, we propose a mid-infrared (MIR) metal–insulator–metal (MIM) chiral metasurface absorber composed of gold-alumina-gold (Au-Al₂O₃-Au) layers, where chirality is introduced by symmetry breaking between two gold elliptical bars in the top layer. Finite element calculations show that the structure operates over 3.5–6.5 µm and produces dual-band CD responses with values of 0.83 and −0.81. The CD magnitude in each band can be independently tuned by adjusting the semi-major or semi-minor axis of the elliptical bars. In addition, rectangular slots inserted into the bars enable continuous redshift of the resonance wavelengths, and the tunability can be further enhanced by optimizing the slot dimensions. These results provide a practical strategy for designing tunable dual-band chiral absorbers and may be useful for future chiral sensing and polarization imaging applications. Full article

This article presents preliminary research on the development of a cast iron–ceramic composite for modern braking systems, such as brake discs. The composite matrix is gray cast iron with flake graphite (EN-GJL-150). The reinforcing phase is a porous ceramic composed of SiC and Al₂O₃ particles introduced separately (10% each) and together (70% SiC + 30% Al₂O₃). These particles were applied as a suspension onto polyurethane foam, yielding a ceramic structure with a pore density of up to 10 ppi. The resulting insert was placed in a mold cavity, and cast iron was poured into it. The resulting samples were treated as brake disc material, with a pad made of the commercial friction material P50094 serving as the countersample. Tribological tests showed that the lowest sample wear (average 2.23 mg/5000 m) was achieved for the composite reinforced with SiC + Al₂O₃ particles. This is probably due to the synergy between the antifriction properties of these particles and the lower friction coefficient (µ = 0.180–0.22). Similar mass loss values and the smallest difference between the tested samples were observed for composites with SiC particles (3.01 mg/5000 m) and Al₂O₃ (3.30 mg/5000 m). The second part consisted of microstructural studies. Microstructural analysis of the EN-GJL-150 + SiC + Al₂O₃ composite revealed a previously unobserved nucleation phenomenon at the cast iron–ceramic interface. This confirmed the general assumptions of Riposan’s theory regarding the involvement of oxide microinclusions and complex manganese sulfides of the (Mn, X)S type in the nucleation and crystallization of graphite precipitates. It was also found that, in the case of “in situ” GJL-150 + SiC + Al₂O₃ composites, this theory should account for the beneficial role of ceramic particles in promoting the uniform distribution of type A graphite flakes, which nucleate on their surfaces in the transition zone. Thus, the nucleating role of oxide microinclusions (the first stage of Riposan’s theory) could be taken over by SiC and Al₂O₃ particles, constituting a substrate for the heterogeneous nucleation of (Mn, X)S sulfides. Full article

Clay minerals in coal play a key role in controlling mineralogical composition, geochemical signatures, and the industrial behavior of coal and its combustion residues. This study investigates the occurrence, provenance, and potential applications of clay minerals in Carboniferous ash-rich coals from the Bogatyr, Lenin, and Saradyr coal mines in northeastern Kazakhstan. A total of 60 coal samples were analyzed using XRD, SEM–EDS/BSE, XRF, and ICP-OES following acid leaching. Based on ash yield, 52 samples were classified as coal (<50% ash), while 8 samples were classified as carbonaceous shale or mudstone (>50% ash). Mineralogical assemblages show clear variability among the studied mines. Saradyr samples are strongly quartz-dominated with lower clay proportions, Bogatyr samples exhibit highly heterogeneous quartz–clay–mica assemblages, whereas Lenin samples are relatively more clay-rich and dominated by kaolinite and illite-group minerals. Across all samples, kaolinite is the dominant clay mineral (16.6–46 wt.%), occurring mainly as authigenic pore- and cell-filling aggregates. Minor phases include illite–muscovite (7.1–29.9 wt.%), illite–smectite (up to 7.6 wt.% in Bogatyr), and smectite–montmorillonite (0.4–0.7 wt.%). Clay minerals occur as discrete particles, coatings, and pore fillings, contributing to ash formation; however, their correlation with ash yield is weak (R = 0.03–0.05), reflecting heterogeneous mineral inputs and diagenetic overprinting. All geochemical data are reported on a high-temperature coal ash (HTA) basis (815 °C). Geochemical indices (CIA, CIW, CIX) and Al₂O₃/TiO₂ ratios (1.8–17.4) indicate variable provenance and moderate to high weathering intensity, reflecting mixed mafic to intermediate source rocks. A total of 23 trace elements were identified. Au occurs at trace levels (up to 0.02 ppm), while selected rare earth elements (REE: Ce, Dy, Eu, La, Nd, Sm, Y, Yb) average 0.2–0.3 ppm, indicating negligible economic recovery potential. REEs show a strong positive correlation with clay minerals (r = 0.93), indicating adsorption and minor structural incorporation. In contrast, Au correlates with As, V, Zn, Cu, Ni, and Nb, suggesting sulfide association. HTA is enriched in SiO₂–Al₂O₃ phases dominated by kaolinite and quartz, indicating strong potential for cement, geopolymer, ceramic, and zeolite applications. Full article

The cohesion zone of a blast furnace is instrumental in determining the gas-dynamic regime and the efficiency of reducing gas utilization. The extent of this phenomenon is contingent upon the initial and final temperatures at which iron ore undergoes softening, which, in turn, are determined by the chemical and phase composition, as well as the degree of reduction of the charge. The present study investigated sinter with a basicity (CaO/SiO₂) ranging from 1.2 to 3.0 using a combination of methods. The experimental program involved the use of X-ray diffraction (XRD) with refinement using the Rietveld method, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and load-dependent softening tests. It was established that as the basicity increased, the content of the calcium–aluminum silicoferrite (SFCA) binder phase increased from 6.2 to 17.5 wt.%, whilst the amount of hematite decreased from 12.6 to 2.3 wt.%. The softening onset temperature increases from 1185 to 1260 °C, the softening end temperature from 1345 to 1415 °C, and the softening interval narrows from 160 to 155 °C. The evolution of the phase composition of sinter during controlled reduction (0–95%) has been investigated for the first time. It has been demonstrated that the maximum accumulation of wustite (FeO) is attained at a reduction degree of 40–60%, irrespective of the basicity of the substance. It is precisely in this range that the minimum softening start (1040–1065 °C) and end (1170–1210 °C) temperatures are observed, which is associated with the formation of low-melting eutectics. The sinter belongs to the CaO–SiO₂–FeO–Al₂O₃–MgO system, and the softening behavior is governed by the FeO–CaO–SiO₂ system where low-melting eutectics form. When the reduction rate exceeds 60%, the metallic phase becomes dominant, leading to an increase in softening temperatures and a narrowing of the cohesion zone. It is evident from the data obtained that the optimal basicity range of the sinter is 2.0–2.5. Furthermore, it is recommended that a reduction degree of at least 60% is implemented in order to improve gas dynamics and increase blast furnace productivity. The findings can be utilized to enhance the efficiency of charge materials and refine mathematical models of the blast furnace process. Full article

Solid-state electrolytes (SSEs) are essential for achieving long-term stability and fast-charging performance in secondary batteries. Although Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) offers high ionic conductivity, its practical application is restricted by high-temperature sintering requirements and interfacial reduction at the lithium anode. In contrast, Li-based oxide electrolytes can be sintered below 600 °C, offering improved compatibility with conventional electrodes such as graphite and silicon. In this study, a Li₂O–LiCl–B₂O₃–Al₂O₃ (LCBA)/LATP composite SSE was fabricated via hot-press co-sintering at 600 °C. Composites with LCBA:LATP weight ratios of 8:2, 7:3, 6:4, 5:5, 3:7, and 2:8 were prepared to identify the optimal composition. The 3:7 composite achieved a sintered density of 2.40 g/cm³ and an ionic conductivity of 2.5 × 10⁻⁴ S/cm. Phase evolution and sintering behavior were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Compared to single-phase LCBA or LATP, the composite electrolyte exhibited improved interfacial stability and lower interfacial resistance against lithium metal. Full article

This work presents the design of a $\beta$-Ga₂O₃ MOSFET incorporating a P-type Ga₂O₃ buffer layer on a high-thermal-conductivity AlN/SiC composite substrate. The electrical characteristics of the device were simulated using Sentaurus TCAD. Results demonstrate that the integration of the composite substrate effectively mitigates self-heating effects, reducing the peak temperature ($T_{\mathit{max}}$) from 776.5 K to 570.9 K at 300 K, while simultaneously increasing the threshold voltage ($V_{\mathit{th}}$) from −0.35 V to 1.52 V. Through systematic optimization of the P-Ga₂O₃ buffer layer thickness and doping concentration, the device achieves a breakdown voltage ($V_{\mathit{br}}$) of 4781 V, a power figure of merit (PFOM) of 2.18 GW/cm², an $I_{DS}$, on/off ratio of 9.20 × 10⁹, and cut-off/maximum oscillation frequencies ($f_{\mathit{t}}$/$f_{\mathit{max}}$) of 1.29 GHz and 1.40 GHz, respectively. These findings provide a theoretical foundation for developing $\beta$-Ga₂O₃-based power devices with high breakdown voltage, improved thermal conductivity, and low specific on-resistance ($R_{\mathit{on},\mathit{sp}}$). Full article

Heat transport properties of serpentine minerals are important to the thermal state of subduction zones, but available data contain systematic errors from contact losses, radiative gains, deformation with pressure (P), and/or modelling short-comings. Here, laser flash analysis (LFA) provides thermal diffusivity (D) within ±3% as a function of temperature (T) of perpendicularly oriented, nearly pure Mg₃Si₂O₅(OH)₄ polymorphs, Al-rich lizardite with minor brucite, three serpentinites, plus chrysotile and lizardite near Ni₃Si₂O₅(OH)₄. Visible spectra show that Fe is mostly ferric and Cr³⁺ occasionally occupies tetrahedral sites. The proposed coupled substitution of Al³⁺ + OH⁻ replacing Si⁴⁺ + O²⁻ accounts for extra OH⁻ peaks in infrared spectra. Rietveld refinements and infrared spectra reveal that serpentine dehydration in LFA runs begins near 800 K. Thermal conductivity (K) vs. T is calculated within ~±5% from D, available heat capacity data, and ambient density. For antigorite, D and K are strongly anisotropic whereas chrysotile has extreme differences, but lizardite is nearly isotropic. A thermodynamic identity provides ∂(lnK)/∂P = 11 ± 1% Gpa⁻¹ for soft serpentine, double that of hard olivine. Lizardite becomes more thermally conductive than olivine near the 1 bar decomposition temperature, which increases with P. Through feedback, and because released H₂O vapor carries heat upwards, P,T conditions in serpentinized slabs follow the decomposition phase boundary during subduction. Full article

The rapid expansion of crystalline silicon photovoltaic (PV) modules has increased the demand for sustainable and high-value recycling strategies for end-of-life (EOL) modules. A significant challenge is the removal of impurities such as carbon, oxygen, and non-metallic inclusions introduced into silicon solar cells during the dissociation of PV laminates. To address this, we propose a non-consumable electrode electroslag remelting (NCE-ESR) process to effectively eliminate inclusions. In this process, the reverse flow of alloy droplets and the extensive contact area are crucial during the reverse flow slag washing. Initially, we studied the occurrence characteristics of inclusions in silicon solar cells obtained after pyrolysis from enterprises. Pyrolysis facilitated the formation of inclusions like Si-O, C-O, Al-O, and Si-N, particularly in the fine size range below 5 μm. To enhance impurity removal, the recycled Si was alloyed with Cu, which increased the melt density and impurity activity. Based on optimized thermodynamics and physical properties, we designed a novel electroslag composition of 40%CaO-40%SiO₂-20%CaF₂ suitable for silicon alloy refining. Notably, during the reverse flow slag washing of the Cu-Si alloy, the maximum removal rate of inclusions reached 77.42%. The average diameter of inclusions was reduced to below 6 μm, and the removal rates of impurity elements such as Al, O, and C exceeded 98.09%, 94.86%, and 86.08%, respectively. Finally, we independently developed the NCE-ESR equipment and conducted a kilogram-scale amplification test. The results indicated that the impurity removal rates of Al and O exceeded 97%, and the final inclusion size was less than 10 μm. This study demonstrates a scalable and environmentally friendly approach for the high-value recycling of silicon resources from decommissioned PV modules. Full article

In this work, we report the fabrication and characterization of single-film and double-film composite epitaxial garnet structures based on single-crystalline films (SCFs) and bulk single-crystal (SC) scintillators for enhanced α–γ discrimination in mixed radiation fields. These composite scintillators consist of TbAG:Ce and YAG:Ce SCFs grown by liquid-phase epitaxy (LPE) on Czochralski-grown Gd₃Ga_2.5Al_2.5O₁₂ (GAGG:Ce) bulk SC substrates. Single- and double-film architectures were designed to optimize the energy absorption and pulse-shape discrimination (PSD) performance for low-penetrating α-particles and high-energy γ-rays. Energy calibration was performed using different γ-ray sources (⁵⁷Co, ⁵¹Cr, and ¹³⁷Cs), enabling the conversion of detector signals to a calibrated electron-equivalent energy scale (keVee). Integration gates were systematically optimized, yielding maximum figures of merit (FOM) of 1.4 for the GAGG:Ce SC substrate, 1.9 for the single-film composite, and 5.0 for the double-film composite, demonstrating a progressive improvement in α–γ discrimination with increasing structural complexity. Two-dimensional PSD density maps reveal well-separated α and γ events, with the highest separation observed for the double-film composite. These results indicate that the engineering of LPE-grown composites provides tunable scintillation decay profiles, enhanced temporal separation, and increased light yields, making them promising candidates for applications such as mixed radiation field detection, dosimetry, and radiation monitoring. Full article