Search Results (300)

Intermetallic compounds represent a highly promising class of materials for catalytic applications due to their tuneable structure, composition, and electronic properties. In this study, we report a series of carbon black-supported intermetallic Pt-Te and Pt-Zn nanoparticles synthesized via a novel and facile direct vapour–solid approach. Their catalytic performance toward the oxygen reduction reaction (ORR) in alkaline media was systematically investigated. Incorporation of Te or Zn into Pt/C significantly enhanced the intrinsic activity, as reflected by an increase in the limiting current density from −2.11 mA cm⁻² for Pt/C to up to −2.94 mA cm⁻² for Pt-Zn and −2.85 mA cm⁻² for Pt-Te systems, while maintaining similar half-wave potentials of 0.79 V vs. RHE and onset potentials around 0.90 V vs. RHE. This work provides a direct comparison of two intermetallic systems prepared under identical conditions, demonstrating how composition and crystal structure determine the catalytic activity and selectivity in the ORR. Full article

The design of photodetectors tailored to specific wavelengths in the mid-infrared (MIR) band serves as a foundational enabler for advancements in scientific research, industrial inspection, and environmental monitoring. Metasurfaces, composed of artificially engineered subwavelength unit cells, enable precise tailoring of light–matter interactions, achieving near-unity absorption at target wavelengths and thereby significantly boosting the sensitivity and spectral selectivity of MIR photodetectors. In this study, we developed a double-C open-loop metasurface and optimized its geometric parameters to realize high-efficiency absorption at 4 μm and 6 μm. Utilizing Te thin films fabricated via magnetron sputtering, we constructed a metasurface-enhanced mid-infrared photodetector based on Te thin films. The optimized metasurface structure enhances the light absorption of the Te thin film by a factor of eight within the target wavelength band. Ultimately, the metasurface-enhanced Te-based device achieved responsivities of 10.5 A/W and 13.7 A/W at 4 μm and 6 μm, respectively, representing enhancements of 3.6-fold and 3-fold compared to the initial Te thin-film device. This work provides a critical reference for enhancing the detection performance of infrared photodetectors at specific wavelengths through precise nanophotonic design. Full article

In this study, the carbothermic reduction of sodium antimonate in crucible smelting was investigated. The optimal process temperature was determined to be 900 °C, with 10% coke consumption (with an ash content up to 15.33%) and a feed particle size of minus 1 mm. The process does not involve the addition of slag-forming components. Sodium participates in the formation of the slag phase. According to the smelting results, the amount of antimony recovered as crude metal reached 71–72%, while the Sb content in the crude metal reached up to 94.5%. A significant portion of antimony (up to 27%) volatilizes with off-gases. A notable sodium content was detected in the crude antimony, reaching up to 8% in some samples, while more than 80% of sodium was transferred to the slag phase. Arsenic, present in the initial concentrate at a level of 0.6%, was distributed approximately equally among the metallic, slag, and gas phases. Lead was predominantly concentrated in the crude antimony. Iron preferentially dissolved in the crude antimony. Other impurities were distributed in comparable amounts between the metallic and slag phases. Tellurium, present in sodium antimonate at 0.79%, was detected in some samples within the slag phase. Full article

A micro-cavity based on phase-change material is a very important strategy for the realization of tunable absorption and conversion of terahertz waves. In this work, a tunable terahertz metamaterial absorber based on the phase-change material germanium–antimony–tellurium (GST) is demonstrated. The device features a metal–insulator–metal triple-layer structure, where the dynamic switching of absorption characteristics is achieved via thermally controlled GST phase transition. In the amorphous state, the absorber exhibits a single absorption peak at 7.7 THz. Upon crystallization, the absorption switches to dual peaks at 5.1 THz and 8.3 THz, achieving near-perfect absorption in both states. Full-wave electromagnetic simulations and theoretical analysis based on a multiple-reflection interference model indicate that this performance tuning originates from the GST-phase-transition-induced change in the equivalent optical cavity length. This corresponds to a switch between two resonant modes: coupled inner–outer ring resonance and independent outer ring resonance. These results provide a foundation for developing dynamically tunable terahertz devices with promising applications in terahertz communications, imaging, and sensing. Full article

Copper anodic slime is often smelted with lead to improve silver and gold recovery, generating a fine lead-rich fly ash that contains notable amounts of selenium and tellurium. Due to its high lead content and sub-micron particle size, this residue poses significant environmental and occupational health risks. This study evaluates sodium carbonate (Na₂CO₃) leaching as an environmentally benign pre-treatment aimed at partially removing selenium and tellurium while stabilizing lead through carbonate formation. The goal is detoxification rather than maximum metal recovery, enabling safer disposal or subsequent recycling. A central composite design (CCD) in Design-Expert software (Version 12) was used to assess the effects of Na₂CO₃ concentration, temperature, solid-to-liquid ratio, and time on selenium and tellurium dissolution. Selenium recovery reached up to 53.9%, while tellurium recovery peaked at approximately 33.9%. Scanning electron microscopy showed the dust to consist mainly of semi-spherical and elongated particles, with lead carbonate forming preferentially on particle surfaces during leaching. Energy-dispersive spectroscopy confirmed conversion of lead sulfate phases to lead carbonate, which increasingly restricted selenium and tellurium dissolution. Kinetic evaluation suggested selenium leaching follows mixed control involving both surface reaction and diffusion through product layers, whereas tellurium dissolution lacked consistent kinetic behavior. Thermodynamic calculations supported the stabilization of lead as cerussite (PbCO₃), indicating improved environmental safety. The overall dissolution trends were successfully represented using an apparent Shrinking Core Model (SCM) based on measurements collected at 20 °C, 60 °C, and 100 °C. Full article

We studied experimentally and computationally the structures and optical properties of sulfur (S), selenium (Se) and tellurium (Te) ring clusters. We encapsulated S, Se and Te into AFI, MOR, CHA and LTA zeolites via vapor adsorption or high-pressure injection from melt and studied Raman and optical absorption spectra (RS and OAS, respectively) of zeolite single crystals with incorporated S, Se and Te ring clusters. Importantly, strict orientation of the rings in zeolite crystals allowed us to study the polarization/orientation dependency of ring RS and OAS. The obtained experimental spectra are found to be in agreement with density functional theory results (DFT using the PBE0 functional and def2-TZVP basis sets) for S₈, Se₆, Se₈, Se₁₂, Te₆ and Te₈ ring molecules. The agreement is especially good for Te rings, while for S and Se rings harmonic frequency scaling factors are required. The S and Se rings display light-induced effects, which we attribute to the presence of conical intersections between their ground and excited electronic states, resulting in isomerization and subsequent fragmentation. We consider this effect using the Se₆ ring example. This phenomenon is important for understanding photostructural changes not only in chalcogen clusters but also in bulk materials such as amorphous selenium. Full article

Directional control of heat flow is essential for advanced energy and electronic systems, yet strategies for tuning anisotropic phonon transport in low-dimensional materials remain limited. Hollow tellurium (Te) nanowires were synthesized via a solvothermal method and modified through Pd electroless plating to achieve tunable anisotropic thermal transport. Structural analyses confirmed Pd incorporation as nanoscale surface deposits without crystalline Pd phases, while SEM observations revealed cavity enlargement due to galvanic displacement at higher PdCl₂ concentrations. Bulk films prepared by cold pressing exhibited direction-dependent behavior. Thermal conductivities remained nearly unchanged below 2.2 mM PdCl₂, but at 5.5 mM, the in-plane value increased to 2.14 W/(m·K) and the cross-plane value decreased to 0.39 W/(m·K), enhancing the anisotropy ratio from 2.71 to 5.49. This divergence arises from direction-selective phonon scattering, where Pd-rich regions promote in-plane heat flow while junction irregularity suppresses cross-plane transport. These results demonstrate a controllable approach for engineering anisotropic thermal properties in functional energy materials. Full article

This study presents the development and evaluation of a novel solid–gas reactor designed to enhance the hydrogen reduction kinetics of tellurium oxide (TeO₂) under atmospheric pressure. Such gas–solid reactions can be processed in several types of reactors, including but not limited to fixed-bed reactors, moving-bed reactors, and fluidised-bed reactors. A combination of computational fluid dynamics (CFD) and experimental validation was employed to design and optimise a reactor’s geometry and gas-flow distribution. Single-phase CFD simulations were performed using the k–ω SST turbulence model to examine gas-flow behaviour, temperature uniformity, and gas-flow dead zones for two lance designs. The modified lance produced a stable swirling flow that improved gas distribution and eliminated stagnation regions. Experimental trials confirmed the simulation outcome in optimised gas-flow: the redesigned reactor achieved up to 65% conversion after 1 h and 70% after 2 h, a marked improvement over the rotary kiln, which required 5–6 h to reach similar levels. However, excessive gas flow led to cooling effects that reduced conversion efficiency. These results demonstrate the effectiveness of integrated CFD-guided reactor design for accelerating hydrogen-based oxide reduction and advancing sustainable metallurgical processes. Full article

Two types of devices capable of switchable infrared spectral control are demonstrated by utilizing the phase-change characteristics of In₃SbTe₂ (Indium–Antimony–Tellurium, IST), which transitions from a low-loss dielectric amorphous phase to a high-loss metallic crystalline state. Through comprehensive structural design, theoretical calculation, simulation analysis, experimental measurement, and application demonstration, we realize distinct switching effects and functions of these two devices. In the first design, IST mono-layer thin films integrated with infrared-transparent substrates (KBr and ZnSe) enable switching between amorphous high transmittance and crystalline high reflectance states over the 2.5–15 μm range, suitable for infrared optical switches and stealth applications. In the second design, introducing a Si metasurface disk array atop the IST mono-layer thin film enables switching between broadband infrared transparency and narrowband high emissivity. This configuration allows independent spectral control of the infrared spectra within the non-atmospheric (5–8 μm) and atmospheric (8–14 μm) windows, providing a versatile platform for tunable thermal radiation management and adaptive infrared camouflage. Full article

Second harmonic generation measurements for neodymium-doped bismuth–tellurium borate (Bi₃TeBO₉:Nd³⁺) powders are shown for the first time. Using undoped and low-content Nd³⁺-doped samples associated with the strongest nonlinear optical response, studies of temperature-dependent second-harmonic generation near the absorption edge were conducted. Spectroscopic measurements of the investigated powders revealed characteristic Nd³⁺ absorption bands and helped to estimate the corresponding energy band gaps for the chosen samples. The influence of low Nd³⁺-content on the absorption edge shift, as well as on the enhancement of second-harmonic generation and its temperature attenuation, is discussed. Temperature-dependent X-ray diffraction measurements enabled researchers to calculate the thermal expansion coefficients for undoped and Nd³⁺-doped Bi₃TeBO₉ and to assess the impact of this phenomenon on its acentricity. Thermogravimetric studies demonstrated the absence of phase transitions for the chosen samples up to their incongruent melting points. Energy Dispersive X-ray Spectroscopy measurements verified the uniformity of Nd³⁺ distribution in doped Bi₃TeBO₉ powders. The suitability of polycrystalline Bi₃TeBO₉:Nd³⁺ as media for the self-frequency doubling devices for potential optoelectronic and biomedical applications was assessed. The finest fractions of deagglomerated and suspended powders were extracted and demonstrated near-nanostructural morphology of separated particles, as revealed by means of atomic force microscopy. Full article

Tellurium–selenium alloy films exhibit excellent performance in short-wave infrared photodetection due to their adjustable bandgap, high carrier mobility, low fabrication temperature, and compatibility with CMOS technologies. Owing to their distinctive one-dimensional chain-like architecture, they can form van der Waals heterojunctions with materials such as silicon, III–V compound semiconductors, and metal oxides. This enables the construction of high-performance short-wave infrared photodetectors. This research examines the latest advancements in heterojunction photodetectors utilizing Te_xSe_1−x alloy sheets. First, the backdrop and justification of this review are outlined followed by discussing the fundamental aspects of Te_xSe_1−x alloy films including their appearance, electrical functionality, optoelectronic performance, fabrication methods and figures of merit for photodetectors. Subsequently, we examine recent advancements in heterojunction photodetectors based on Te_xSe_1−x alloy films and discuss methods to enhance device performance through interface engineering and structural design. Finally, we consolidate the findings and discuss potential future developments and challenges we may encounter. Full article

Jiaodong Gold Province is a globally rare giant gold cluster, with ongoing debates regarding its metallogenic material sources and mineralization mechanisms. This study focuses on the Linglong quartz-vein-type gold deposit within the Zhaoping Fault Zone, conducting in situ trace element and S-Pb isotope analyses of pyrite from different mineralization stages. The trace element characteristics were investigated to explore the sources of metallogenic materials, the evolution of ore-forming fluids, and the mechanisms of gold precipitation. The main findings are as follows: (1) In the Linglong gold deposit, gold primarily enters the pyrite lattice as a solid solution (Au⁺) through Au-As coupling. From the Py1 to Py3 stages, Co and Ni contents significantly decrease, while Cu, As, Au, and polymetallic element contents continuously increase. Additionally, Cu mainly replaces Fe²⁺ in the form of Cu²⁺, whereas Pb predominantly exists as micro inclusions of galena. (2) The S isotope (Py1: δ³⁴S = +7.60‰–+8.25‰, Py2: δ³⁴S = +6.15‰–+8.15‰, Py3: δ³⁴S = +6.90‰–+9.10‰) and Pb isotope (²⁰⁶Pb/²⁰⁴Pb = 16.95–17.715, ²⁰⁷Pb/²⁰⁴Pb = 15.472–15.557, ²⁰⁸Pb/²⁰⁴Pb = 37.858–38.394) systems collectively constrain the ore-forming materials such that they are dominated by metasomatized enriched lithospheric mantle, with simultaneous mixing of crustal materials. (3) The ore-forming fluid underwent a continuous evolution process characterized by persistently decreasing temperatures and a transition from mantle-dominated to crust–mantle mixed sources. The Py1 stage was predominantly composed of mantle-derived magmatic fluids uncontaminated by crustal materials, representing a high-temperature, closed environment. In the Py2 stage, the fluid system transitioned to an open system with the incorporation of crustal materials. Through coupled substitution of “As³⁺ + Au⁺ → Fe²⁺” and dissolution–reprecipitation processes, gold was initially activated and enriched. During the Py3 stage, pyrite underwent dissolution–reprecipitation under tectonic stress and fluid activity, promoting extraordinary element enrichment and serving as the primary mechanism for gold precipitation. Concurrently, bismuth–tellurium melt interactions further facilitated the precipitation of gold minerals. Full article

This paper presents results derived from carbothermic reduction of tellurium from a tellurium-containing condensate obtained during the oxidative-distillation roasting of a tellurium-containing middling. It is shown that the tellurium-containing condensate contains TeO₂ and Te₂O₃(SO₄) phases. A regression model and a generalized equation were constructed using mathematical planning methods. This model and equation describe the dependence of tellurium recovery from the tellurium-containing condensate on the main process parameters. The developed models demonstrated a high degree of adequacy and made it possible to calculate the optimal parameters for the carbothermic reduction of tellurium. Experimental verification confirmed the possibility of obtaining elemental tellurium with a purity of 99.5%. The obtained data indicate the feasibility of producing crude tellurium by means of a two-stage pyrometallurgical process performed at low pressure. Organization of the process via the use of sealed equipment for the capture of tellurium-containing compounds through condensation significantly reduces the environmental risks associated with the toxicity of tellurium and its compounds. Full article

The Evevpenta gold–silver epithermal deposit, belonging to an adularia–sericite or low-sulfidation type, is in the northern part of the Kamchatka Peninsula within the Oligocene–Quaternary Central Kamchatka volcanic belt. Variously native gold, silver, and Au–Ag chalcogenides, including calaverite, petzite, hessite, acanthite, uytenbogaardtite-petrovskaite, and naumannite, constitute its Au–Ag mineralization. Extensive fluid inclusion studies, involving fluid inclusion petrography, Raman spectroscopy, and microthermometry, revealed that quartz from gold-bearing adularia–quartz veins crystallized from low-salinity fluids (T ice melting from −0.1 to −3.3 °C) at moderate to low temperatures (140 to 364 °C). The mineralizing fluids consisted of Na, K, and Mg sulfate and bicarbonate-bearing aqueous solutions and low-density CO₂. The gold-bearing mineral assemblages were formed within narrower temperature ranges. The gold–telluride–quartz assemblage was deposited between 325 and 175 °C, while the telluride–sulfide–quartz formed between 219 and 258 °C. Possible influx of meteoric waters led to progressive cooling and a decrease in salinity from the early to late fluid generations during mineral deposition. Overall data on ore and associated with metasomatic alteration mineralogy indicate that the ore formation occurred under relatively reduced or neutral conditions from weakly acidic to near-neutral aqueous solutions, possessing relatively high sulfur and tellurium fugacity. Full article

The Zhunuo porphyry Cu deposit (2.9 Mt Cu @ 0.48%) in the Gangdese belt, southern Xizang, represents a key Miocene post-collisional system. This study integrates textural, major-, and trace-element analyses of pyrite from distinct alteration zones to unravel its hydrothermal evolution and metal precipitation mechanisms. Our study identifies four distinct pyrite types (Py1-Py4) that record sequential hydrothermal stages: main-stage Py2-Py3 formed at 354 ± 48 to 372 ± 43 °C (based on Se thermometry), corresponding to A and B vein formation, respectively, and late-stage Py4 crystallized at 231 ± 30 °C, coinciding with D-vein development. LA-ICP-MS data revealed pyrite contains diverse trace elements with concentrations mostly below 1000 ppm, showing distinct distribution patterns among different pyrite types (Py1-Py4). Elemental correlations revealed coupled behaviors (e.g., Au-As, Zn-Cd positive correlations; Mo-Sc negative correlation). Tellurium variability (7–82 ppm) records dynamic fO₂ fluctuations during system cooling. A comparative analysis of pyrite from the regional deposits (Xiongcun, Tiegelongnan, Bada, and Xiquheqiao) highlighted discriminative geochemical signatures: Zhunuo pyrite was enriched in Co-Bi-Ag-Pb (galena inclusions); Tiegelongnan exhibited the highest Cu but low Au-As; Xiquheqiao had the highest Au-As coupling; and Bada showed epithermal-type As enrichment. Partial Least Squares Discriminant Analysis (PLS-DA) identified Cu, As, and Bi as key discriminators for deposit types (VIP > 0.8), with post-collisional systems (Zhunuo and Xiquheqiao) showing intermediate Cu-Bi and elevated As versus arc-related deposits. This study establishes pyrite trace-element proxies (e.g., Se/Te, Co/Ni, and As-Bi-Pb) for reconstructing hydrothermal fluid evolution and proposes mineral-chemical indicators (Cu-As-Bi) to distinguish porphyry-epithermal systems in the Qinghai-Tibet Plateau. The results underscore pyrite’s utility in decoding metallogenic processes and exploration targeting in collisional settings. Full article