Search Results (111)

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 magmatic Ni-Co-Cu mineralization in the Iken deposit in the central part of the Kun-Manie complex, Amur Oblast, Russia, hosted by an olivine-bearing websterite, is of a low-sulfide type. The fine-grained disseminations of base metal sulfides (BMS), dominantly pyrrhotite, pentlandite (a major source of Ni of industrial importance), and chalcopyrite, are followed by a scarce Pd-Pt-Ag mineralization. Elevated contents of Al in orthopyroxene (mean 2.78 wt.% Al₂O₃) along with Al–Na enrichment in clinopyroxene (diopside; mean 5.10 wt.% Al₂O₃) are associated with highly aluminous compositions of low-chromium members of the spinel–hercynite series. High levels of TiO₂ in kaersutite and titanian phlogopite also reflect a pronounced degree of fractionation of the ore-forming melt. Minor portions of sulfide melt are distributed evenly as a result of immiscibility at advanced stages of orthopyroxene crystallization, after the formation of olivine. Differentiated grains of droplet-like BMS largely settled in situ close to grain boundaries of orthopyroxene or occupied interstitial spaces of pyroxenes and olivine in association with spinel–hercynite and fluorapatite. A combination of late saturation in S with relatively quick cooling rates of the hypabyssal body prevented the effective settlement and accumulation of sulfide droplets in the ore zone. The well-developed lamellae of troilite (Fe₅₀S₅₀) exsolved from the host pyrrhotite Fe₄₈S₅₂ during subsolidus cooling, as a consequence of a low-temperature reaction triggered by a sudden drop in fO₂. An influx of mantle-derived fluid bearing CO₂, CO, and CH₄ with the rising magma could be the primary cause of the fO₂ reduction. Also, graphite-bearing metasedimentary rocks could have been assimilated. Tiny grains of minerals of noble metals (moncheite and merenskyite with essential amounts of melonite component, sperrylite, hessite, alloy Au_63.2Ag_36.8, and argentopentlandite) deposited late in a fluid-enriched medium under submagmatic conditions. Full article

Dry reforming of methane (DRM) converts the greenhouse gases methane (CH₄) and carbon dioxide (CO₂) into syngas (hydrogen (H₂) and carbon monoxide (CO)). Despite its numerous advantages, DRM has not yet been industrialized due to catalyst deactivation and competing side reactions. While Ni-based catalysts have been widely used, they are prone to increased carbon deposition and sintering, and although bimetallic systems and oxygen-based supports have shown promise, their effects on carbon deposition are yet to be fully understood. In this study, carbon nanotube (CNT)-supported Pt-Ni catalysts incorporating mixed oxides of CeZrO₂ and CeZrLaO₂ were investigated to evaluate the impact of support composition and metal–support interactions in DRM. The catalysts were synthesized and subsequently tested in DRM. Catalysts supported on CNTs displayed higher CH₄ and CO₂ conversions compared to conventional ceria–zirconia, highlighting the beneficial role of the carbon nanotube support in improving dispersion and accessibility of the metal active sites. Addition of Pt was found to promote reverse water–gas shift (RWGS) reaction, whereas the addition of La was found to decrease catalytic activity. Despite the formation of a Ni-Pt alloy, the obtained catalysts favored RWGS over DRM. These findings illustrate key limitations and design considerations for optimization of CNT-supported bimetallic catalysts in DRM. Full article

The microstructure, phase composition, and high-temperature oxidation behavior of Al_0.5CoCr_0.5NiPt_0.1 and AlCoCr_0.5NiPt_0.1 multi-principal element alloys (MPEAs) at 1100 °C in air were investigated. Depending on the content of aluminum, the microstructure of as-cast samples contains FCC and BCC solid solutions. Similarly, the ratio of two solid solutions varies depending on the aluminum content in the alloy. When the content of aluminum is x = 0.5, the microstructure is dominated by the FCC solid solution, while a BCC solid solution is dominated when the concentration of aluminum is increased to x = 1.0. Moreover, in both MPEAs, platinum exists as a part of solid solutions rather than a separate phase. High-temperature oxidation was carried out in a Plavka.Pro PM-1 SmartKiln muffle furnace under isothermal conditions at 1100 °C for 100 h exposure in air, and weighing was performed every 10 h. The maximum specific weight gain for the Al_0.5CoCr_0.5NiPt_0.1 alloy was 0.965 mg/cm², and 0.675 mg/cm² for the AlCoCr_0.5NiPt_0.1 alloy. Based on the high-temperature oxidation experiment results, it was established that AlCoCr_0.5NiPt_0.1 MPEA exhibits greater resistance towards high-temperature dry air corrosion with the formation of an exclusive Al₂O₃ scale on the surface with 3–5 μm thickness; the parabolic oxidation rate constant for this alloy is k_p = 20.2 × 10^–13 (g²/cm⁴s). Introduction of platinum into the composition of the Fe-free AlCoCr_0.5Ni alloy reduces the value of the parabolic oxidation rate constant by half. Full article

Achieving selective conversion of lignin-derived phenolic compounds to cycloalkanes under mild conditions remains a significant challenge. Herein, we report a novel iron-incorporated two-dimensional NiO nanosheet supported Pd-Pt alloy catalyst (Pd_1.7-Pt_0.3/NiO-5FeO_x) that is capable of facilitating highly efficient hydrodeoxygenation (HDO) of lignin-derived phenolic model compounds (e.g., 2,6-dimethoxy-4-methylphenol) under mild conditions (250 °C, 5 atm H₂). The reaction mechanism was investigated through various characterization techniques and mechanistic studies: introducing FeO_x into the NiO support increases the proportion of defect-related oxygen species (Oβ), enhances adsorption of the key hydrogenated alcohol intermediate 4-methylcyclohexanol, and optimizes the acidity distribution of the catalyst, thereby promoting C(_sp³)-O bond cleavage (dehydroxylation) toward cycloalkane formation. The catalyst achieved high conversion (>95%) for various lignin-derived phenolics and high selectivity (93.0%) toward methylcyclohexane under mild conditions. This work offers new insights into the design of efficient biomass conversion catalysts under mild conditions and provides an energy-efficient route for the sustainable utilization of lignin resources. Full article

The rapid growth of electronic waste (e-waste) demands sustainable recovery solutions based on green chemistry. Conventional recycling relies on energy-intensive pyrometallurgical routes that cause emissions and material losses. This study applies Molecular Recognition Technology™ (MRT™) for selective energy-efficient recovery of base (Cu, Ni, Fe, Sn) and precious/platinum group metals (Ag, Pd, Pt) from a collector metal alloy. A hydrometallurgical process combining electrowinning, sequential acid leaching, and MRT™ separations achieved >99% metal purity with minimal waste generation. The results demonstrate MRT™ as a scalable green alternative for high-efficiency metal recovery from e-waste, supporting circular economy objectives. Full article

This study investigates reduced graphene oxide (rGO)-supported bimetallic M–Pt (M = Co, Ni, Cu) alloy nanoparticles as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media. Monometallic Pt and bimetallic M–Pt nanoparticles were synthesized and uniformly dispersed on rGO, followed by structural and compositional characterization using transmission electron microscopy and inductively coupled plasma mass spectrometry. Their electrocatalytic performance toward HER was systematically evaluated at different temperatures. All electrocatalysts exhibited enhanced activity at higher temperatures, with current densities increasing by approximately 1.68–2.65 times at 338 K compared with 298 K. Among the investigated materials, CoPt/rGO delivered the highest cathodic current densities and a Tafel slope of 75 mV dec⁻¹, indicating favorable reaction kinetics. This performance is associated with a higher electroactive surface area, as determined by cyclic voltammetry, and reduced charge-transfer resistance, as revealed by electrochemical impedance spectroscopy. Notably, the CoPt/rGO electrocatalyst demonstrated excellent short-term operational stability at a constant potential of −0.28 V vs. RHE. These results highlight the potential of rGO-supported CoPt bimetallic alloys as efficient electrocatalysts for alkaline water electrolysis. Full article

Pt-Fe alloys with abundant inclusions are from the Camumbi River placer deposit, Ecuador. They are derived from unknown Alaskan–Uralian-type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Compositions of our previously documented chilled silicate glass inclusions are increasingly fractioned from hydrous ferrobasalt to rhyolite in terms of TAS (total alkalis vs. silica). Their liquid lines of descent change from tholeiitic to the calc-alkaline magma series. Here, we document seven rare composite inclusion parageneses of Cu–PGM (platinum-group mineral) sulfides, each coexisting with and exsolved from related fractionated silicate glass (melt). Differentiation is dominated by fractional crystallization in PGM bulk compositions from tholeiitic silicate melts at the highest T (temperature): ~1018 °C. Silicate glass inclusions following the lower T calc-alkaline trend coexist with sulfide PGM parageneses that were likely differentiated, in terms of Pt-Rh-Pd and BMs (base metals), by incongruent melting due to decompression and S-degassing at ~983–830 °C. S-saturated sulfide melts become S-undersaturated below 845 °C. The calculated temperatures are for silicate glass. Pt-rich braggite shows increasing fractionation towards Pd-rich vysotskite within one inclusion paragenesis. A late braggite–vysotskite fractionation trend shows decreasing minor base metals (BMs). Thiospinels are dominated by cuprorhodsite. Minor thiospinels indicate Fe and then strong Ni enrichment at the lowest T. Decompression exsolutions, deflation, and the partial melting of some sulfide inclusion parageneses support rapid ascent to higher crustal levels within a deep-sourced cumulate intrusion. Full article

The aim of this work was high-temperature synthesis of PtPdCoNiCu/C nanoparticles with high-entropy alloy (HEA) structure as catalysts for oxygen reduction reaction. The materials were synthesized using a highly dispersed PtPd/C support, which was impregnated with Cu, Ni, and Co precursors followed by their precipitation with an alkali. Subsequently, the material was subjected to thermal treatment in a tube furnace at 600 °C for 1 h in a stream of argon containing 5% hydrogen. In combination with HRTEM, element mapping and line scan, XRD, and XPS data, these results confirm the successful synthesis of five-component PtPdCoNiCu high-entropy alloy nanoparticles on the surface of the carbon support. The obtained materials are characterized by a high electrochemical surface area of up to 63 m²/g(PGM), as determined by hydrogen adsorption/desorption and CO-stripping, and a high specific oxygen reduction reaction (ORR) activity of approximately 269 A/g(PGM) at 0.9 V vs. RHE. The synthesized material demonstrated outstanding stability, as confirmed by an accelerated stress test of 10,000 cycles. After the test, the electrochemical surface area decreased by only 12%, while the catalytic activity for ORR even increased. The proposed synthetic strategy opens a new pathway for obtaining promising highly stable five-component HEA nanoparticles of various compositions for application in catalysts. Full article

This study systematically investigates the effect of substituting Copper (Cu) with Nickel (Ni) on the glass-forming ability (GFA) and corrosion resistance of a Pt-based bulk metallic glass (BMG). We demonstrate that a minor substitution of 5 at.% Ni for Cu in the Pt₄₀Pd₂₀Cu₂₀P₂₀ base alloy significantly enhances both properties. The GFA is markedly improved, as evidenced by the supercooled liquid region (ΔTx) widening from 68 K to 91 K. The optimized Pt₄₀Pd₂₀Cu₁₅Ni₅P₂₀ alloy exhibits a compressive fracture strength of 1.38 GPa. Electrochemical tests in a 3.5 wt.% NaCl solution reveal a substantial improvement in corrosion resistance. Compared to the Ni-free baseline alloy, the passive film resistance (R_f) and charge-transfer resistance (R_ct) of the Ni-containing alloy are enhanced by factors of 2.75 and 2.60, respectively. This superior performance is attributed to a synergistic effect wherein Ni alloying both stabilizes the amorphous structure and promotes the formation of a more robust passive film. This work presents a viable strategy for designing cost-effective, high-performance multi-component BMGs for applications in aggressive chloride environments. Full article

Non-precious catalysts for alkaline hydrogen evolution reaction (HER) face a fundamental multi-scale challenge: lack of synergy between electronic structure tuning for balancing H adsorption and water dissociation, active site stabilization for boosting intrinsic turnover frequency (TOF), and mass transport. Even Pt loses 2–3 orders of magnitude activity in alkaline media due to inefficient water dissociation, a synergistic gap unresolved by the Sabatier principle alone. Existing strategies only address isolated aspects: phase engineering optimizes electronic structure but not active site stability; heteroatom doping introduces defects unlinked to mass transport; and nanostructuring enhances mass transfer but not atomic-level activity. None of them address multi-scale mechanistic synergy. Herein, we design a hierarchically porous P-doped NiCo alloy (hpP-NiCo) with an aim of achieving this synergy via integrating α-FCC/ε-HCP phases, P-induced defects, and 3D porosity. The formed α/ε interface tunes the d-band center to balance H adsorption and water dissociation; and the doped P stabilizes metal-vacancy sites to boost TOF. In addition, porosity matches mass transport with active site accessibility. In 1 M KOH, hpP-NiCo reaches 1000 mA cm⁻² at 185 mV overpotential and has a Tafel slope of 43.1 mV dec⁻¹, corresponding to electrochemical desorption as the rate-limiting step and verifying Volmer acceleration. Moreover, it also exhibits bifunctional oxygen evolution reaction (OER), achieving 100 mA cm⁻² at potential of 1.55 V. This work establishes a mechanistic synergy model for non-precious HER catalysts. Full article

This study investigates the structural and magnetic properties of ultra-high coercivity (Fe₈₀B₁₄Nb₆)_0.88Dy_0.12 alloys, doped with 0.5–5 at.% of selected metallic additions: magnetic (Ni, Co) and non-magnetic (Pt, Cu) elements. Material characterization involved both structural and magnetic measurements. Alloys containing dopant concentrations up to 2 at.% exhibited similar phase compositions, with the Dy₂Fe₁₄B compound being dominant. Magnetic hysteresis loops revealed a superposition of two components: magnetically soft and hard phases. A significant change in magnetic properties was observed within the 0.5 to 1 at.% dopant concentration range. Notably, the addition of 0.5 at.% Ni increased the apparent anisotropy field from 5.2 T to 7.5 T. Furthermore, 0.5 at.% Pt led to an increase in the coercive field from 4.6 T to 5.5 T. These additions influenced crystallization, resulting in the formation of a more regular microstructure without submicrometric dendrite branches, when compared to the base alloy. Full article

The development of high-performance electrochemical sensors is crucial for ammonia–nitrogen detection. Therefore, in this study, we successfully prepared one ternary PtNiCo nanosheet via the one-step electrodeposition technique. The ratio of H₂PtCl₆·6H₂O, Ni(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O and electrodeposition time were controlled. Under optimal conditions, Pt₆Ni₂Co₂-2000 demonstrated outstanding electrocatalytic performance, exhibiting a high oxidation peak current of 45.27 mA and excellent long-term stability, retaining 88.09% of its activity after 12 h. Furthermore, the sensing performance of Pt₆Ni₂Co₂-2000 was evaluated, revealing high sensitivity (10.01 μA μM⁻¹), a low detection limit (0.688 µM), strong anti-interference capability, great reusability, great reproducibility, and remarkable long-term stability. Additionally, recovery tests conducted in tap water, lake water, and seawater yielded highly favorable results. This study demonstrated that designing Pt-based alloys can not only enhance the electrochemical performance of Pt but also serve as an effective strategy for improving electrocatalytic ammonia oxidation and ammonia–nitrogen detection. Full article

Liquid Organic Hydrogen Carriers (LOHCs) represent a promising technology for the safe storage and transport of hydrogen. Its technical development largely depends on the catalysts used in the hydrogenation and dehydrogenation processes. Typically, noble metal-based monometallic catalysts are employed, although they present limitations in terms of cost and availability. This study uses the DBT system to explore the potential of nickel (Ni) as a catalytic alternative. In dehydrogenation, its role as an additive in low-loaded Pt-based catalysts (0.25 wt%) was evaluated, showing a significant increase in activity, with dehydrogenation levels exceeding 95%, compared to 82% obtained with monometallic Pt catalysts. This improvement is attributed to the formation of Pt-Ni alloys. On the other hand, although the bimetallic systems were not effective in hydrogenation, a commercial Ni/Al₂O₃-SiO₂ catalyst was tested, achieving hydrogenation degrees of 80% in just 40 min, after pressure and catalyst loading optimization. These results position Ni as a key component in LOHC catalysis, either as an effective additive in Pt-based systems or as an active metal itself, due to its excellent performance and low cost. This paves the way for economically viable and efficient catalytic solutions for hydrogen storage applications, bridging the gap between performance and practicality. Full article

The development of efficient platinum group metal-free (PGM-free) catalysts for the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) is essential for advancing hydrogen-based energy technologies. In this study, Ni_xMo_100−x composites supported on Carbon Ketjenblack EC-300J (CK) were synthesized via thermal reduction under a controlled Ar/H₂ (95:5) atmosphere to investigate the effect of the Ni/Mo molar ratio on electrocatalytic performance. Structural and morphological analyses by XRD and TEM confirmed the formation of the NiMo alloys and carbide phases with controlled particle size distributions (~18 nm), while BET measurements revealed specific surface areas up to 124.69 m² g⁻¹ for the Pt-loaded samples. Notably, the 3% Pt/Ni₉₀Mo₁₀-CK catalyst exhibited outstanding bifunctional activity in a half-cell configuration, achieving an overpotential of 65.2 mV and a Tafel slope of 41.6 mV dec⁻¹ for the HER, and a Tafel slope of 32.9 mV dec⁻¹ with an exchange current density of 1.03 mA cm⁻² for the HOR. These results demonstrate that compositional tuning and minimal Pt incorporation synergistically enhance the catalytic efficiency, providing a promising platform for next-generation hydrogen electrocatalysts. Full article