Journal of Materials Science最新文献

The Co–N–C catalyst has exhibited its effectiveness as a substitute for the 2e⁻ ORR in the synthesis of H₂O₂. However, it still exhibits low selectivity towards 2e⁻ ORR. In this work, the P doped Co–N–C (Co–N/P–C) electrocatalysts with enhanced performance for H₂O₂ production were synthesized through in situ P-doping method. Moreover, the P content of Co–N/P–C was varied to investigate its correlation with H₂O₂ selectivity. The results revealed that P doping greatly enhanced both selectivity and yield of H₂O₂. Under acidic conditions (pH = 1), Co–N/P–C-0.75 exhibited optimal 2e⁻ ORR performance (H₂O₂ yield of 174 mmol g⁻¹ h⁻¹, H₂O₂ selectivity of 34.39%, electron transfer (n) of 3.31), significantly outperforming the P-free Co–N–C catalyst (H₂O₂ yield of 64 mmol g⁻¹ h⁻¹, H₂O₂ selectivity of 10.81%, n of 3.78). Additionally, Co–N/P–C-0.75 based electron-Fenton process showed attractive performance for rhodamine B (RhB) degradation, whose degradation rate was two times higher than that of Co–N–C. The experimental findings revealed that the improved efficiency of Co–N/P–C-0.75 could be attributed to the substitution of coordinated N atom with less electronegative P atom, which enhanced the electron density around the Co atom and facilitated *OOH desorption for H₂O₂ production.

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In this study, a series of composite solid polymer electrolyte (CPE) films was synthesized by employing poly(vinylidene fluoride-co-hexa-fluoropropylene) (PVdF-HFP), sodium bis(trifluoromethane sulfonyl)imide (NaTFSI), ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl sulfonyl) imide [PYr₁₄] [TFSI], and SiO₂ nanoparticles using the solution cast technique. The SiO₂ nanoparticles have been prepared using Stöber’s method and post-synthesis functionalized with thiol groups using (3-mercapto-propyl) trimethoxysilane (MPTMS), respectively. The attachment of the thiol group on SiO₂ has been confirmed by XRD and FTIR studies. The optimized film having 3.5 wt% SiO₂ has been characterized via various techniques. It is found to have maximum ionic conductivity of ~ 0.84 mS/cm at RT and is thermally stable up to 370 °C. The addition of SiO₂ improves the mechanical properties of the electrolyte films. The optimized film exhibits a large working potential window of ~ 5.9 V. In this work, porous activated carbon (AC) has been synthesized from bio-derived Gond Katira obtained from the Astragalus gummifer shrubs using an activating agent (KOH). The synthesized AC shows porous nature and high specific surface area (870.62 m²g⁻¹). Using the optimized CPE film and AC, an electric double-layer capacitor (EDLC) has been fabricated. The EDLC characteristics have been obtained using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) techniques. The fabricated EDLC shows a maximum specific capacitance of ~ 165 Fg⁻¹ with an efficiency of ~ 97%.

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This study presents a machine learning (ML)-driven framework for optimizing the design of polyaniline (PANI)-based supercapacitors, a promising material for energy storage. The framework integrates experimental data and advanced optimization techniques to systematically investigate the effects of key fabrication parameters such as mesh size, deposition cycles, voltage window, and operating potential on performance metrics, including specific capacitance, energy density, and internal resistance (IR) drop. Two ML models, gradient boosting regressor (GBR) and random forest regressor (RFR), were trained on 145 experimental datasets, achieving high predictive accuracy (R² > 0.95). Bayesian optimization (BO) was used to identify the global optimum fabrication conditions, resulting in significant reductions in mean absolute percentage errors 15% for energy density, 20% for capacitance, and 7% for IR drop. Feature importance analysis, including SHAP and partial dependence plots, revealed that mesh size and operating potential were the most influential parameters, aligning with electrochemical theories on ion transport and polymer growth. This integrated approach not only accelerates the design and optimization of PANI-based supercapacitors but also minimizes material waste and provides a scalable, interpretable pathway for ML-driven optimization in the development of high-performance, cost-effective energy storage devices.

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The non-uniformity of phase transformation between different regions during the cooling process of dual-phase steel is a key factor determining the level of residual stress. In this paper, a new mechanism is revealed through experimental studies and thermal-metallurgical-mechanical coupled simulations, in which austenite-stabilizing elements (Nb, C, and Mn) synergistically regulate phase transformation kinetics, improving the uniformity of phase transformation and thereby suppressing residual stress. It is found that Nb retards ferrite transformation through the solute drag effect and improves its distribution uniformity in a two-phase microstructure. The synergistic effect of Nb-C-Mn significantly reduces the martensite Ms temperature and transformation rate, thereby decreasing the difference in martensite content between the surface and the core. The enhancement of phase transformation uniformity effectively alleviates the phase transformation stress and non-coordinated plastic strain caused by the difference in phase transformation volume expansion, which becomes a key factor in reducing residual stress. In a typical Ferrite/Martensite dual-phase steel, optimizing the alloy composition reduces surface and core residual stress by 35.1 and 35.6%, respectively. This study clarifies the correlation mechanism between alloy composition, phase transformation uniformity, and residual stress, providing a new perspective for the development of low-stress, high-strength steels.

To address the limitations of traditional supercapacitors in wearable electronics, we developed a low-cost stepwise processing to fabricate a hierarchical mesoporous composite electrode directly grown on carbon cloth. A cobalt-based MOF (Co-BTC) precursor was directly grown on carbon cloth. Afterward, mesoporous nanocomposites were derived via appropriate carbonization, followed by polypyrrole (PPy) encapsulation via in situ polymerization. Systematic structural analyses (XRD, XPS, FTIR) confirmed that the derived nanocomposite consists of Co₃O₄, CoO, and a small amount of Co with amorphous carbon. PPy covered on the surface of the mesoporous nanocomposites. The flexible and conductive PPy-coated CoOx/C nanocomposite not only sustains the integrity of mesoporous structure, increases the electronic conductivity, but only enhances the adhesion to the carbon cloth current collector. Such novel formula and processing enabled the electrode to maintain structural integrity and excellent cycle life under repeated 180° bending in a prototype symmetric supercapacitor device setting.

Antimony sulphoselenide Sb₂(S_1−xSe_x)₃ solid solution exhibits tailored semiconducting characteristics that are widely useful in various optoelectronic, catalytic and photocatalytic applications. In addition, these compounds are nontoxic and made of earth abundant constituent elements. In this work, the viability of syntheses of Sb₂(S_1−xSe_x)₃ solid solution series (x = 0, 0.6, 1.2, 2.1, 2.4 and 1) via dry ball milling method in Ar atmosphere is evaluated. X-ray diffraction, Raman spectroscopy analysis confirmed the formation of single-phase Sb₂(S_1−xSe_x)₃ bulk compounds with orthorhombic crystal structure. Scanning electron microscopy, transmission electron microscopy and X-ray spectroscopy analyses allowed for a comprehensive understanding of the morphological and compositional details of the solid solution compound series. Optical absorption and band gap values were estimated from diffused reflectance measurements and found to vary between 1.61 and 1.13 eV, confirming the composition-controlled bandgap tunability. Cyclic Voltammetry, Electrochemical Impedance Spectroscopy and Linear Sweep Voltammetry analyses were done to infer the electrocatalytic properties of the series. It is inferred that among all the compositions, Sb₂S₃ showed low charge transfer resistance (~ 73 Ω) and onset potential of 197 mV versus RHE for hydrogen evolution reaction.

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This study explores the influence of nitrogen plasma-treated SnO₂ NPs (NPs) on the structural, permittivity, and impedance behavior of nematic liquid crystals. ML-0648 samples doped with 0.5 wt% SnO₂ NPs were subjected to alternating current nitrogen plasma for 2, 7, and 14 min. Plasma treatment reduced NPs size from 28.27 to 21.68 nm, altered surface topography, and adjusted NP–LC interfacial interactions. Permittivity measurements revealed non-monotonic alteration of both parallel and perpendicular components, with dielectric anisotropy being most significant for untreated samples and minimal at 7 min, originating from plasma-induced defect creation. Impedance spectroscopy and Cole–Cole analyses showed time-dependent development of bulk resistance, capacitance, and space charge polarization, consistent with facilitated surface-mediated conduction and defect creation. XRD confirmed the retention of SnO₂ crystallinity, with intensity variations from particle size and morphology. The novelty of the current contribution lies in the illustration of nitrogen plasma as a tunable route for tailoring NP–liquid crystal interfaces to enable minute manipulation of anisotropic dielectric and impedance properties in future photonic and display technologies.

Unveiling the morphological transition mechanism of eutectic structures in the Ag-based filler metals is crucial to control the microstructures in the brazing seam and improve the mechanical properties of brazed joints. In this study, the effect of alloying elements addition (Co, Mn, Ni, and Ti) on the morphological evolution in the Ag-based filler metals was investigated, and the morphological transition mechanism of eutectic structures after addition of different contents at various cooling rates was elucidated. The variation in addition content of alloying elements and solidification velocity strongly affected the formation and morphologies of Ag dendrites and Ag–Cu binary eutectic structures. For the low content of alloying element and slow solidification velocity, the FES and LES always coexisted in the samples, indicating a competitive growth. With increasing content and/or solidification velocity, the LES → FES, FES → LES, and LES → AES transitions were determined. The AES formation with four different patterns including AES at the intersections of FES clusters, AES at the intersections of LES clusters, AES resulting from Cu-rich phase precipitating between Ag dendrites, and between secondary dendritic arms. The AES formation was mainly attributed to the recalescence during solidification promoting the partial remelting of FES or LES, and the precipitation of Cu-rich phase splitting Ag dendrite skeleton. The result provides a deep insight into the microstructural evolution in the Ag-based filler metals and the brazing seam and offers guidelines for controlling the microstructure and properties of brazed joints by modifying the brazing filler metal composition and brazing process parameters.

To enhance the performance of the AlCoCrFeNi_2.1 high-entropy alloy (HEA) and expand its potential engineering applications, this study investigated the effects of Nb addition on its precipitate phases, strength–toughness balance, and mechanical behavior. The results show that the introduction of Nb promotes the formation of (Cr, Fe, Ni)₂Nb-type Laves phases and eutectic structures in the alloy, while refining the FCC phase, coarsening the BCC phase, and precipitating particulate Laves phases uniformly within the BCC matrix. The impact mechanism of the eutectic phases and the dispersed Laves phases on the alloy’s strength–toughness synergy was systematically analyzed through the indentations and crack features observed in microhardness tests. With increasing Nb content, both the average microhardness and wear resistance of the alloy were significantly improved. Compared with the AlCoCrFeNi_2.1 HEA, the AlCoCrFeNb_0.6Ni_2.1 alloy exhibited a 210% increase in microhardness and an 86% reduction in wear rate. This study provides a quantitative basis for using Nb within a specific addition range to regulate precipitate phases and achieve a balanced optimization of the mechanical properties in this series of high-entropy alloys.

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Solar-driven photocatalytic water splitting is a highly promising approach for sustainable energy conversion. In this work, first-principles computations grounded in density functional theory are employed to comprehensively explore the structural configurations, electronic properties, catalytic performance, and optical responses of the WS₂/ZrS₂ heterostructure system. According to the calculated electronic structure, the WS₂/ZrS₂ heterojunction demonstrates a staggered type-II band alignment, featuring an indirect energy gap of 1.28 eV, which is significantly narrower than that of its monolayer components. Charge density analysis further confirms that the WS₂/ZrS₂ heterojunction follows a distinct Z-type charge transfer path. This unique carrier transfer pattern effectively promotes the separation of photogenerated electron–hole pairs, thereby significantly enhancing the catalytic performance in both hydrogen and oxygen evolution reactions. The band edge positions of the WS₂/ZrS₂ heterostructure effectively encompass the potentials for photolysis of water in the pH range of 0 to 14. Moreover, introducing sulfur vacancies on the WS₂ side significantly reduces the reaction energy barrier. Meanwhile, Considering the effective optical absorption onset and excitonic effects, the theoretical STH efficiency is conservatively estimated to be above 25.33%, further confirming the exceptional catalytic potential of the WS₂/ZrS₂ heterojunction. Therefore, this heterojunction holds significant promise for photocatalytic water-splitting applications.

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