Search Results (279)

Juniperus species form critical, long-lived high-mountain forest ecosystems in Central Asia, serving essential phytocoenotic and ecological functions in environmentally challenging habitats. However, the relationships between the elemental composition of these evergreen conifers and their underlying soils remain poorly understood. This study evaluated and compared the distribution of major elements (Fe, Ca, P, Mg, Al, Na, K, S), trace elements (Cu, Pb, Zn, Ni, Co, Mn, As, Cd, Cr, Mo, U, Th, Sr, Sb, Bi, V, La, Ba, Ti, B, W, Sc, Zr, Tl, Ta, Nb, Se, Te, Ga, Cs, Ge, Hf, Rb, Sn and others), and environmental pollution indices (Igeo, EF, CF, BAF) in plant tissues (leaves and cones) and canopy soils of three key juniper species (Juniperus seravschanica, J. turkestanica, and J. semiglobosa) in the Fann Mountains, Tajikistan. Soil and plant samples were collected across natural habitats and analyzed for total chemical composition using ICP-OES. The soils showed a near-neutral reaction (pH 7.02–7.42 in H₂O and 6.41–7.15 in KCl), with considerable variability in Corg. content (5.04%–21.82%) and Nt content (0.337%–1.149%) in the humus (A) horizons. Geochemical indices (Igeo up to 2.42, EF up to 35.30) indicated noticeable soil enrichment and localized contamination by arsenic (As) and cadmium (Cd), likely driven by a combination of regional industrial and mining activities alongside natural geogenic enrichment. Across all sites, elemental concentrations followed a consistent sequence: soil > leaves ≈ cones. Heavy metals in plant tissues remained well below toxic thresholds. High organ-specific partitioning was observed: K predominated in cones (K > Ca > P), whereas Ca and Fe accumulated predominantly in leaves (Ca > K). Low bioaccumulation factor values (BAF < 1) indicate limited element accumulation relative to total soil concentrations for all three species, which may be influenced by both reduced bioavailability in neutral-to-alkaline soils and potential physiological regulation. As the first data reported from this region, these findings establish an essential baseline for long-term ecological monitoring, soil–plant chemistry, conservation, and environmental risk assessment in the Fann Mountains’ juniper ecosystems. Full article

Resistive random-access memory (RRAM) has emerged as one of the most promising device platforms for neuromorphic, in-memory computing because its two-terminal metal–insulator–metal (MIM) structure can reproduce the weight-update behavior of biological synapses while remaining compatible with mainstream CMOS processing. This review summarizes the current state of RRAM-based neuromorphic technology from four complementary perspectives: device physics, materials, fabrication processes, and packaging. We first describe the operating principles of filamentary and interface-type RRAM, including the forming/set/reset switching sequence, and the two dominant analytical frameworks used to describe the reset transition—the ion-migration model and the thermally driven filament-dissolution model. We then review the switching-layer and electrode materials that have been most widely investigated such as HfO_x, TiO_x, TaO_x, ZnO, ZrO₂, and Cu/Ag-based conductive-bridge systems, together with representative bilayer and doped architectures reported for synaptic devices. The biological functions that RRAM can emulate are discussed alongside the non-ideal characteristics that currently limit on-chip training accuracy, with emphasis on separating device-to-device from cycle-to-cycle variability and on the workload-dependent nature of endurance and retention requirements. We further summarize the process technologies used to integrate RRAM into large-scale, CMOS-compatible arrays, including atomic layer deposition, interfacial oxygen-reservoir engineering, low-thermal-budget back-end-of-line integration, and three-dimensional vertical RRAM patterning, and discuss the advanced packaging strategies such as 2.5D/3D heterogeneous integration, chiplet architectures, thermal-interface materials, and nanostructured underfills required to manage the power density and interconnect demands of large synaptic arrays, distinguishing solutions that have been demonstrated specifically for RRAM neuromorphic arrays from those that remain general advanced-packaging concepts. Finally, RRAM is benchmarked against competing emerging non-volatile memories, and the key research directions such as three-terminal memtransistor architectures, three-dimensional integration with high-performance selectors, and hardware–algorithm co-design that will determine whether RRAM-based neuromorphic hardware can move from laboratory demonstrations to on-device AI, autonomous systems, and large-scale artificial-neural-network accelerators are outlined. Relative to prior reviews that focus primarily on RRAM device physics or on switching-layer materials in isolation, the distinctive contribution of this review is an explicit, cross-layer synthesis that connects device-level non-idealities to their consequences for wafer-scale process integration and for advanced 2.5D/3D packaging—a combination that, to our knowledge, has not been jointly treated in the recent review literature on RRAM-based neuromorphic hardware. Full article

CO/CO₂ co-methanation provides an effective route for the high-value utilization of coke oven gas and carbon-rich industrial off-gases. However, the highly exothermic nature of methanation readily induces local hot spots, leading to Ni particle sintering, pore blockage, carbon deposition, and surface passivation, which severely restrict the long-term stability of catalysts. In this work, Ni-Mn/Ti-Zr-La-Ce and SiC-modified Ni-Mn/Ti-Zr-La-Ce-SiC catalysts were constructed to systematically elucidate the role of SiC in enhancing catalyst stability during CO/CO₂ co-methanation. Stability tests showed that the SiC-modified catalyst maintained nearly complete CO and CO₂ conversions during long-term operation at 250 °C, 1.0 MPa, and a GHSV of 5000 h⁻¹, whereas the unmodified catalyst exhibited obvious deactivation, particularly in CO₂ conversion. Spectroscopic and structural characterizations revealed a dual mechanism for the stability enhancement induced by SiC. On the one hand, SiC provides physical anchoring and thermal-management effects: it strengthens the metal–support interaction, suppresses Ni particle growth and sintering, and alleviates local hot-spot formation through its high thermal conductivity, thereby preserving the catalyst structure. On the other hand, SiC exerts electronic and surface-chemical regulation effects: it stabilizes Ni⁰ sites required for CO hydrogenation, moderates CO₂ adsorption, promotes the hydrogenation of reaction intermediates, and inhibits carbon deposition. These two effects act synergistically to optimize both thermal management and interfacial stability. This study provides a theoretical basis and practical guidance for the design of efficient and stable CO/CO₂ co-methanation catalysts for industrial applications. Full article

This study integrates conventional sediment geochemistry with explainable machine learning to investigate the provenance of surface sediments from Wular Lake, Kashmir Valley, NW Himalaya. Twenty-two samples were analysed for 49 geochemical variables (10 major oxides, 25 trace elements and 14 rare earth elements), complemented by XRD mineralogy, which reveals an assemblage dominated by quartz, muscovite/illite, chlorite and feldspar. The Chemical Index of Alteration (CIA = 68.5–75.1, mean 72.1), corroborated by CIW, PIA and the A–CN–K trend, indicates moderate weathering under a cold temperate climate, and the Index of Compositional Variability (ICV > 1), together with uniformly low Zr/Sc ratios (3.4–6.0), which preclude significant zircon addition through recycling, records compositionally immature, first-cycle detrital input. Conventional discrimination ratios and the Herron system classify the sediments as geochemically equivalent to shale, and elevated Fe₂O₃/K₂O (2.6–4.0), Al₂O₃/TiO₂ (12.6–16.0), Cr/Th and Co/Th ratios record a substantial mafic imprint. Chondrite-normalised REE patterns show pronounced LREE enrichment ((La/Yb)_N = 8.0–19.4), moderate negative Eu anomalies (Eu/Eu* = 0.56–0.73) and negligible Ce anomalies (Ce/Ce* = 0.98–1.03), with Eu/Eu* discriminating felsic crystalline from mafic volcanic contributions. A three-stage pipeline (principal component analysis (PCA) → random forest → SHapley Additive exPlanations (SHAP)) achieved a median leave-one-out cross-validation (LOO-CV) accuracy of 95.5% (n = 22; Wilson 95% CI 78%–99%), and unsupervised k-means clustering reproduced the same three geochemically distinct provenance end-members: siliceous-mature, detrital-mafic and carbonate-bearing, without reference to the assigned labels (Adjusted Rand Index = 1.0). Because the training labels derive from the same geochemical dataset, the classification quantifies the internal consistency of the provenance model, but does not provide independent validation. SHAP analysis reveals that trace elements (Cr, Co, Sc, Ni, Zn) carry greater discriminating power than do conventional major-oxide ratios, demonstrating that explainable machine learning robustly supplements and extends traditional provenance approaches. Full article

In this work, the structural, mechanical, electronic, and optical properties of the 18-valence-electron half-Heusler compounds MCoBi (M = Ti, Zr, Hf) are investigated using the all-electron full-potential linearized augmented plane wave (FP-LAPW) method. The relativistic effect of spin–orbit coupling (SOC) is systematically incorporated and analyzed. Structural optimization confirms the stability of the Type-III phase, with lattice parameters in good agreement with available experimental data. Mechanically, the inclusion of SOC reduces both stiffness and brittleness, indicating a clear softening effect on the material behavior. SOC significantly lifts the degeneracy of the electronic bands, resulting in splitting (Δ_SO) at the valence band maximum of approximately 0.10 eV and 0.12 eV for TiCoBi and ZrCoBi, respectively, which subsequently reduces the band gap; however, HfCoBi exhibits a remarkably weak splitting. The impact of SOC is further evidenced in the optical response across all three compounds. The absorption coefficient reaches high values (>${10}^5 {\mathrm{c}\mathrm{m}}^{-1}$) in the visible spectrum. Furthermore, a dramatic reduction in the intensity of plasmon resonance frequencies is observed, with values dropping to approximately 0.10–0.11 for the studied compounds. These findings highlight the potential of these materials for future electronic and optoelectronic device applications. Full article

This review summarizes the development of Ti-based high-entropy and multi-principal element shape memory alloys (SMAs), with a particular focus on TiZrHfCoNiCu, TiHf(Zr)Ni(Pt)Pt, and TiPd-based systems. Alloy composition and heat treatment significantly influence martensitic transformation temperatures (MTTs), thermal hysteresis, superelasticity (SE), shape memory effect (SME), and elastocaloric effect (eCE) through precipitation reactions, compositional partitioning, and lattice strain effects. These parameters are summarized in the tables. Furthermore, recent advances in machine learning have provided powerful tools for predicting MTTs and thermal hysteresis. Important features governing phase transformation behavior, as well as suitable regression models for predicting MTT and thermal hysteresis, are introduced. These developments demonstrate a transition from empirical alloy development toward data-driven and physics-informed design of next-generation HE-SMAs. Full article

The emergence of all-d-metal Heusler alloys has opened up new pathways for the design of advanced functional materials. In this work, we employ first-principles electronic structure calculations to systematically investigate the electronic and magnetic properties of 27 all-d-metal Heusler compounds following the stoichiometry $X_{2}YZ$, where $X=$ Co, Rh, Ir, $Y=$ V, Cr, Mn, and $Z=$ Ti, Zr, Hf. Electronic band structure calculations show a consistent minority-spin pseudogap across the series, the width and characteristics of which are strongly dependent on the d-band broadening introduced by $4d$ (Rh, Zr) and $5d$ (Ir, Hf) transition metals. Magnetically, these materials largely follow the $M_{\mathrm{t}}=Z_{\mathrm{t}}-24$ Slater–Pauling rule, driven by exactly 12 occupied minority-spin bands at the $\Gamma$ point. Notably, substituting Co with Rh or Ir significantly redistributes the magnetization, drastically reducing the X-site spin magnetic moment while amplifying the spin magnetic moments on the Y-site atoms. This study provides a comprehensive understanding of the interplay between structural symmetry, orbital hybridization, and magnetism in all-d-metal Heuslers, highlighting their promise for future spintronic applications. Full article

Lead-free [(Ba_0.85Ca_0.15)_1−1.5xNd_x][(Zr_0.1Ti_0.9)_0.995Mn_0.005]O₃ (x mol% Nd/Mn BCZT, x = 0.05, 0.1, 0.5, 1 mol%) ceramics were prepared by the traditional solid-state reaction method, in which the synergistic effects of sintering temperature and Nd/Mn co-doping on the phase structure, microstructural evolution, and electrical properties were systematically investigated. All ceramics exhibit a pure perovskite structure, with the tetragonal (P4mm) phase dominating at room temperature as confirmed by the X-ray diffraction Rietveld refinement. The sintering temperature (1475–1520 °C) is found to be the primary factor governing densification and grain growth, with the relative density peaking at 91.7% for the x = 0.5 mol% sample sintered at 1505 °C. Within this optimized processing window, increasing the Nd content induces a gradual migration of the Curie temperature (T_C) toward lower temperatures, accompanied by enhanced relaxor behavior. A highlight of this work is the strategic balance between piezoelectric activity and mechanical quality factor through a “donor–acceptor” co-doping mechanism. Specifically, for the x = 0.5 mol% ceramics, an exceptionally high mechanical quality factor (Q_m = 424.5) is achieved for samples sintered at 1490 °C, which is proposed to be associated with the temperature-modulated formation of ${Mn}_{Ti}^{″}-V_O^{••}$ defect dipoles, while a peak inverse piezoelectric coefficient $d_{33}^{*}$ of 685.1 pm/V is maintained at a sintering temperature of 1520 °C. Full article

High-entropy alloy (HEA) coatings exhibit enhanced chemical stability when doped with carbon, primarily due to the strong bonding between carbon and transition metals. Typical transition metals used in these coatings include Cr, Fe, Co, Ni, Cu, Ti, V, W, Nb, Ta, and Zr. Owing to their excellent chemical stability, HEA coatings are widely employed to protect component surfaces operating in highly corrosive environments. Against this backdrop, the present study investigates the effect of carbon doping introduced via methane gas flow during the physical vapor deposition of TiAlTaZrNb HEA coatings on corrosion resistance. The morphology and structure of the coatings were analyzed by field emission scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Corrosion protection and coating resistance were assessed through potentiodynamic polarization and electrochemical impedance spectroscopy. While increasing the methane flow resulted in an approximately 34% reduction in coating thickness, the overall coating resistance increased by one order of magnitude, reaching a maximum at a methane flow rate of 9 sccm, corresponding to the carbon solubility limit. This improvement was evidenced by a decrease in the corrosion rate from 8.02 × 10⁻² mm y⁻¹ for the uncoated H13 steel to 8.00 × 10⁻⁴ mm y⁻¹ for the HEA-coated samples. However, at higher methane flow rates, carbon precipitation and the formation of parallel microcracks contributed to an increase in corrosion rate. Full article

Two-dimensional heterostructures have attracted considerable attention in electrocatalytic hydrogen evolution due to their pronounced interfacial effects, tunable electronic properties, and large specific surface areas. In this work, two representative oxygen-terminated transition metal carbides (MXenes) and three typical transition metal dichalcogenides (TMDs) were selected to construct six heterostructures. Using first-principles density functional theory (DFT) calculations, their binding energies, structural stability, electronic structures, and HER catalytic performance were systematically investigated. The results showed that all heterostructures possessed good thermodynamic stability and favorable electronic properties. In particular, SnS₂/Ti₂CO₂, SnSe₂/Ti₂CO₂, SnTe₂/Ti₂CO₂, and SnTe₂/Zr₂CO₂ exhibited near-optimal hydrogen adsorption Gibbs free energy, indicating excellent HER activity. Moreover, the variation in Gibbs free energy of hydrogen adsorption from isolated monolayers to heterostructures could be effectively correlated with the work function difference. The predicted trends provided a useful descriptor for catalytic performance. Overall, this study provides theoretical insights into the rational design of efficient, advanced HER catalysts and contributes to the advancement of sustainable energy conversion technologies. As this work is based solely on first-principles calculations, the predicted catalytic activity of the heterostructure should be regarded as a theoretical prediction and awaits experimental confirmation. Full article

Liquid electrolytes in conventional lithium-ion batteries pose safety risks associated with flammability, leakage, and explosion, whereas solid polymer electrolytes are generally limited by insufficient ionic conductivity at ambient temperature, restricting the development of high-energy lithium batteries. To address these issues, flexible poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte membranes (GPEs) were prepared via a slit-coating process combined with UV curing. NASICON-type lithium aluminum titanium phosphate (Li_1.3Al_0.3Ti_1.7P₃O₁₂, LATP) and garnet-type tantalum-doped lithium lanthanum zirconate (Li_6.4La₃Zr_1.4Ta_0.6O₁₂, LLZTO) were introduced as inorganic ceramic fillers to improve the ion-transport and interfacial properties of the GPE. Among the investigated samples, the PVDF-HFP-based GPE containing 10 wt% LLZTO exhibited the best overall performance, with an ionic conductivity of 3.40 × 10⁻⁴ S·cm⁻¹ at ambient temperature and a Li⁺ transference number of 0.77. Cyclic voltammetry results showed that the LLZTO-modified electrolyte membrane exhibited sharper and more symmetric redox peaks, higher peak current response, and better curve overlap during repeated cycles, indicating improved electrochemical reversibility and interfacial stability. In addition, LLZTO incorporation enhanced the mechanical strength, broadened the electrochemical stability window, and improved the flame-retardant behavior of the membrane. The LiFePO₄/GPE/Li cell assembled with the optimized membrane delivered an initial discharge capacity of 160 mAh·g⁻¹ at 0.1 C and maintained 80 mAh·g⁻¹ at 1 C, demonstrating good rate capability. Moreover, a capacity retention of 96% was maintained after 100 cycles at 0.1 C, confirming excellent cycling stability. Therefore, this work provides an effective strategy for the structural optimization and scalable preparation of high-performance gel polymer electrolyte membranes for lithium battery applications. Full article

Methane combustion over palladium-based catalysts is a critical process for reducing greenhouse gas emissions from lean-burn engines and natural gas installations, yet the role of oxide support in controlling both the population and the intrinsic reactivity of Pd active centres remains incompletely understood. In this work, Pd catalysts at two series of higher and lower loading were prepared on five oxide supports—Al₂O₃, CeO₂, SiO₂, TiO₂, and ZrO₂—and characterised by a complementary suite of techniques including SEM-EDX, XRD, BET, AAS, in situ CO-FTIR, DRIFTS with methanol as a probe molecule, and Raman spectroscopy. Catalytic activity testing revealed the order Pd/CeO₂ > Pd/ZrO₂ > Pd/Al₂O₃ > Pd/TiO₂ > Pd/SiO₂. In situ CO-FTIR site quantification showed that active site density spans nearly an order of magnitude across the series, with Pd/CeO₂ reaching 105.44 µmol g⁻¹ and Pd/Al₂O₃ only 11.63 µmol g⁻¹. Turnover frequency analysis revealed a striking inversion: Pd/Al₂O₃ exhibited the highest TOF (0.1327 s⁻¹), approximately six times greater than Pd/CeO₂ (0.0226 s⁻¹). DRIFTS/methanol profiling demonstrated that CeO₂ and ZrO₂ expose cooperative redox and basic centres that promote methane activation, while SiO₂ supports only weakly bound methoxy species, consistent with its lowest activity. These results establish that the oxide support simultaneously governs Pd dispersion—and hence site density—and the electronic environment of each Pd centre, thereby modulating intrinsic reactivity. High specific surface area alone does not guarantee catalytic performance, and rational support selection is therefore the decisive lever for optimising methane combustion catalysts at ultra-low Pd loadings. In all, our findings provide a quantitative, molecular-level framework that disentangles support-controlled site density from intrinsic site reactivity under identical reaction conditions. By combining in situ CO-FTIR, DRIFTS, and Raman spectroscopy with kinetic analysis on well-defined, high-purity oxide supports, this work transforms previously qualitative “support effects” in Pd-catalysed methane combustion into predictive structure–activity relationships. Full article

This study explored the influence of high silver (Ag) loading (5–10 mol%) on the photocatalytic performance of zirconium (Zr) co-doped TiO₂ (AZT) with a low Zr content. Although various Ag/Zr ratios have been reported, the effect of high Ag loading combined with low Zr content remains largely unrevealed, particularly in low-temperature synthesis where the role of Zr as a phase inhibitor is less critical. To address this gap, the AZT photocatalyst was fabricated via a solvothermal method combined with organic-free peroxy route. Characterization indicated Zr⁴⁺ incorporated into the TiO₂ lattice, inducing structural distortions and promoting Ti³⁺ defect states. Simultaneously, silver existed as ternary Ag species, which functioned as visible light responsive co-catalysts that enhanced light absorption via Surface Plasmon Resonance (SPR) and facilitated efficient charge separation. Photocatalytic performance was evaluated through Methylene Blue (MB) decolorization under household LED lamp. The optimized 7% Ag loaded catalyst achieved 99.4% removal efficiency within 6 h, with a reaction rate ten times higher than the Zr-doped sample. This superior activity was attributed to a p-n heterojunction and the SPR effect, narrowing the optical band gap to 2.60 eV. Radical scavenger experiments confirmed that the process was primarily driven by photogenerated holes. Full article

The safe immobilization of high-level waste (as actinide) remains a critical bottleneck in the disposal of high-level radioactive waste worldwide. Moreover, the higher specific surface area and surface energy of nano-scale powders enable the production of ceramic materials featuring denser crystal structures and superior strength, hardness, and toughness. Therefore, in this study, Gd³⁺ was used as a surrogate for actinides, and Nb⁵⁺ was introduced as a high-valence charge-compensating cation. Nano-scale powders of CaCO₃, ZrO₂, Gd₂O₃, TiO₂, and Nb₂O₅ were employed to prepare a series of defect-fluorite-derived ceramics, CaZr_1-xGd_xTi_2-xNb_xO₇ (x = 0.1–1.0), via a high-temperature solid-state reaction method, aiming to investigate the atomic substitution mechanisms, phase evolution, and chemical stability under high-valence charge compensation. Laboratory X-ray diffraction (XRD), synchrotron X-ray diffraction (SXRD), and backscattered scanning electron microscopy with energy-dispersive X-ray spectroscopy (BSEM-EDX) confirmed a phase evolution sequence from zirconolite-2M to zirconolite-4M and finally to pyrochlore. This behavior is consistent with that reported for other Ln³⁺-Nb⁵⁺ co-doped zirconolite systems. Rietveld refinement of the SXRD data further revealed, for the first time, the site-occupancy mechanism of Gd and Nb in zirconolite-4M. In both zirconolite-2M and zirconolite-4M, Gd preferentially occupies the Ca sites, whereas Nb substitutes at the Ti sites. In the pyrochlore structure, Ca, Zr, and Gd occupy the 16d sites, while Ti and Nb occupy the 16c sites. Static leaching tests following the MCC-1 protocol showed that pyrochlore exhibits the highest leaching resistance, whereas zirconolite-2M shows the lowest. After 28 days, the highest Gd leaching rate was 1.92(1) × 10⁻⁵ g m⁻² d⁻¹. These results provide new insights into actinide immobilization behavior and compositional design in zirconolite-based waste forms. Full article

Nanotextured thin film metallic glasses (TFMGs) have emerged as promising antimicrobial coatings for biomedical applications; however, systematic comparisons across compositionally distinct Ti- and Zr-based systems, as well as their early-stage bactericidal mechanisms, remain limited. Here, we show, for the first time, a comparative, compositionally resolved correlation linking alloy chemistry, nanotexture, and bactericidal mechanisms across polymorphic TFMGs. Three co-sputtered biocompatible coatings (Ti₄₇Fe₄₁Cu₁₂, Zr₇₁Fe₃Al₂₆, and Zr₅₈W₃₁Cu₁₁) were deposited on medical-grade titanium and stainless steel (SS316L) via magnetron co-sputtering, producing uniform amorphous films (190–298 nm) with nanoscale roughness of 1.6 ± 0.05 to 8.1 ± 0.05 nm. Surface wettability spanned hydrophilic (71.1 ± 5.6°) to hydrophobic (106.5 ± 3.5°), modulating bacterial interactions. Antimicrobial performance against Pseudomonas aeruginosa was evaluated using live/dead fluorescence imaging, quantitative image analysis, and electron microscopy after 2–4 h incubation. All coatings reduced bacterial adhesion and viability relative to bare substrates, with Zr₅₈W₃₁Cu₁₁ achieving >60% reduction in surface-associated bacterial coverage. Time-resolved analysis revealed a rapid transition to predominantly non-viable populations on coated surfaces, in contrast to sustained viability on controls. Mechanistically, bactericidal activity arises from the synergistic coupling of nanotopography-induced membrane stress, wettability-governed adhesion energetics, and in situ formation of CuO, Fe₂O₃, WO₃, and ZrO₂ oxides that promote electrostatic interactions and proposed reactive oxygen species generation, driving oxidative membrane damage. These results establish a scalable design framework for TFMGs, while highlighting the need for long-term biofilm and electrochemical validation. Full article