Search Results (171)

Precise control over nanostructure evolution is critical for optimizing the electrochemical performance of pseudocapacitive materials. In this work, Nb₂O₅ nanostructures were synthesized via a time-engineered hydrothermal route by systematically varying the reaction duration (6, 12, and 18 h) to elucidate its influence on structural development, charge storage kinetics, and supercapacitor performance. Structural and surface analyses confirm the formation of phase-pure monoclinic Nb₂O₅ with a stable Nb⁵⁺ oxidation state. Morphological investigations reveal that a 12 h reaction time produces hierarchically organized Nb₂O₅ architectures composed of nanograin-assembled spherical aggregates with interconnected porosity, providing optimized ion diffusion pathways and enhanced electroactive surface exposure. Electrochemical evaluation demonstrates that the NbO-12 electrode delivers superior pseudocapacitive behavior dominated by diffusion-controlled Nb⁵⁺/Nb⁴⁺ redox reactions, exhibiting high areal capacitance (5.504 F cm⁻² at 8 mA cm⁻²), fast ion diffusion kinetics, low internal resistance, and excellent cycling stability with 85.73% capacitance retention over 12,000 cycles. Furthermore, an asymmetric pouch-type supercapacitor assembled using NbO-12 as the positive electrode and activated carbon as the negative electrode operates stably over a wide voltage window of 1.5 V, delivering an energy density of 0.101 mWh cm⁻² with outstanding durability. This study establishes hydrothermal reaction-time engineering as an effective strategy for tailoring Nb₂O₅ nanostructures and provides valuable insights for the rational design of high-performance pseudocapacitive electrodes for advanced energy storage systems. Full article

In this study, a systematic investigation was undertaken to elucidate the influence of polymeric surfactants such as polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and their hybrid combination (PVP/PEG) on the structural, morphological, and electrochemical evolution of Fe₂O₃ electrodes designed for high-performance supercapacitor applications. Fe₂O₃ nanostructures were synthesized via a controlled hydrothermal route, wherein the surfactant composition was precisely tuned to modulate crystal growth, particle dispersion, and surface active-site density. Detailed physicochemical characterization revealed that hybrid PVP/PEG incorporation induced a hierarchically nanograined morphology with optimized porosity. The optimized PVP/PEG-Fe electrode exhibited the largest CV area, lowest equivalent series resistance (0.33 Ω), and superior areal capacitance of 9.17 F cm⁻² at 8 mA cm⁻², attributed to accelerated redox kinetics and efficient ion diffusion. Long-term cycling demonstrated remarkable structural resilience, with ~85.1% capacitance retention after 12,000 cycles. Furthermore, an asymmetric pouch-type supercapacitor (PVP/PEG-Fe//AC) was assembled to validate practical performance, achieving a wide potential window of 1.5 V, an areal capacitance of 0.260 F cm⁻², energy density of 0.081 mWh cm⁻², and coulombic efficiency of 95.73% after 7000 cycles. This work highlights the critical role of cooperative polymer–metal oxide interactions in achieving structural uniformity, optimized electrochemical kinetics, and long-term durability, offering a versatile strategy for engineering cost-effective, high-performance transition metal oxide electrodes for next-generation flexible energy storage devices. Full article

Nanomaterials are usually associated with modern technologies and advanced processing methods. Three silver Dacian bracelets within Cehei hoard (Salaj County, Romania) are tougher than they should be according to the apparently higher silver content. The microstructural investigation reveals that all three bracelets have silver content of about 90 wt.%. The metallographic inspection of a bracelet sample reveals a very refined microstructure of α grain while fewer eutectic grains are almost undetectable, indicating intensive plastic deformation. XRD patterns of the bracelets reveal relevant peaks for silver (without copper) having a much-broadened aspect indicating nanostructural level. The nano-grains were evidenced at high magnification of SEM imaging: 55 nm for bracelet 1, 95 nm for bracelet 2 and 75 nm for bracelet 3. Elemental maps reveal that the nanograins are basically formed by α phase; the finest eutectic traces are situated and uniformly dispersed within α phase, appearing as small red spots. Vickers µHV10 micro indentation was calibrated on a pure silver 999.9 ‰ in annealed state, resulting in 37 HV10. The nanostructured bracelets have about 56 µHV10 for bracelet 1; 50 µHV10 for bracelet 2 and 52 µHV10 for bracelet 3. Dyrrachium drachmas have Vickers microhardness of about 37 µHV10. The obtained results confirm the historian’s supposition that Dyrrachium drachmas could be the source for silver but also clearly indicate that the final steps of bracelets manufacturing were effectuated by cold deformation with intensive cold hardening. It results that cold deformation of the bracelets rods induces a nanostructural state that significantly increases their microhardness instead of their higher silver title. Full article

This paper investigates the influence of substrate grain size on the behavior of a multilayer CrN/CrAlN coating, with the bilayer thickness varying across the cross-section in the range of 200–1000 nm. The substrate tools were made of WC-Co sintered carbide with three different grain sizes. The coatings were subjected to mechanical and tribological tests to assess their performance, including nanohardness, scratch resistance, and tribological testing. The coating’s roughness was measured using a 2D profilometer. Additionally, the chemical composition and surface morphology were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX). The durability tests were performed on an industrial CNC machine tool on the particleboard. The results revealed that tools with ultra-fine nano-grain (S) and micro-grain (T) WC-Co substrates exhibited a significant increase in tool durability by 28% and 44%, respectively. Significant differences in the microgeometry of the substrate U, especially in relation to the tool based on substrate S, explain the lack of improvement in its durability despite the use of a multilayer coating. Full article

BaTiO₃-based lead-free ferroelectric films with a large recoverable energy density (W_rec) and a high energy efficiency (η) are crucial components for next-generation dielectric capacitors, which are used in energy conditioning and storage applications in integrated circuits. In this study, grain-engineered (Ba_0.95,Sr_0.05)(Zr_0.2,Ti_0.8)O₃ (BSZT) ferroelectric thick films (~500 nm) were prepared on Si substrates. These films were deposited at 350 °C, 100 °C lower than the temperature at which the LaNiO₃ buffer layer was deposited on Pt/Ti. This method reduced the (001) grain population due to a weakened interface growth mode, while promoting volume growth modes that produced (110) and (111) grains with a high polarizability. As a result, these films exhibited a maximum polarization of ~88.0 μC/cm², a large W_rec of ~203.7 J/cm³, and a high energy efficiency η of 81.2% (@ 6.4 MV/cm). The small-field dielectric constant nearly tripled as compared with that of the same BSZT/LaNiO₃ heterostructure deposited at the same temperature (350 °C or 450 °C). The enhanced linear dielectric response, delayed ferroelectric polarization saturation, and increased dielectric strength due to the nano-grain size, collectively contributed to the improved energy storage performance. This work provides a novel approach for fabricating high-performance dielectric capacitors for energy storage applications. Full article

Multi-scale characterization techniques have been employed to analyze the size effect of microstructure on the phase transition behavior and dielectric properties of poly(vinylidene fluoride) (PVDF) films. The results show that oriented amorphous fraction layers are prone to form in the vicinity of the grain boundaries of nano-grained films, while the interfacial polarization and electrostriction effect play a major role. Polar nano-regions are prone to form in micro-grained films, and the maximum fraction of polar crystalline phase and maximal dielectric constant can be achieved due to the balance between the intrinsic effect and extrinsic effect of the material. On the contrary, the extrinsic effect corresponding to interfacial charges greatly influences the phase transition behavior between beta and alpha phases for coarse-grained PVDF films, while the dielectric properties are mainly influenced by the intrinsic electrostatic field and van der Waal interaction of the material. Hence, the dielectric behavior of nano-grained films can be adjusted by the copolymerization technique, that of micro-grained films can be adjusted by both the copolymerization technique and the controlling of microstructure morphology, and that of coarse-grained films can be adjusted by the doping technique. Full article

TiAlSiN/AlSiN coatings, with 3 and 30 periods, were successfully deposited by cathodic-arc evaporation technology. The composition, structure, mechanical, and tribological properties were studied at thermal treatment from 700 °C to 900 °C. The SEM observation and EDS analysis verified the dense structure and stable element composition in the coating depth at increased temperatures. A limited surface oxidation was identified at 800 °C, which increased moderately at a higher temperature of 900 °C. The coating period displays a nanocomposite structure of TiAl(Si)N and AlN nanograins incorporated in an amorphous Si₃N₄ matrix obtained by XRD and XPS analyses. The coatings exhibit high hardness of 41.1 GPa and 36.4 GPa for the 3- and 30-period coatings, respectively. The coatings with higher modulation periods demonstrate an excellent high temperature hardness and resistance to elastic and plastic deformations up to 900 °C. The hardness of the coatings with a smaller modulation period reduces to 29.7 GPa at the same temperature, causing a decrease in the H/E and H³/E^*2 ratios. The tribological tests found that the high-temperature wear resistance depends strongly on the coating composition and architecture. An oxidation wear mechanism dominates the coatings with a large modulation period, and the wear rate decreases with a temperature increase. Abrasive wear is predominant in coatings with a lower modulation period, leading to an increasing wear rate. Wear rate values of 7.27 × 10⁻⁶ mm³/N·m and 8.53 × 10⁻⁶ mm³/N·m were determined after annealing at 900 °C for the 3- and 30-period coatings, respectively. Full article

Tailoring the microstructural heterogeneity of metallic coatings is a promising strategy for enhancing their corrosion resistance; however, its systematic optimization remains underexplored. Here in, we present a one-step, scalable electrodeposition strategy to fabricate Ni coatings with tunable nanocrystalline heterostructures on Cu substrates by varying the current density from 1 mA/cm² to 50 mA/cm². The coating with a current density of 10 mA/cm², featuring a heterogeneous nanograin structure of coexisting small and large grains, exhibited optimal corrosion resistance in 3.5 wt.% NaCl solution, with a low self-corrosion current density of 4.48 µA/cm². Electrochemical impedance spectroscopy (EIS) and molecular dynamics (MD) simulations revealed that the heterostructure dispersed Cl⁻ adsorption sites and promoted passivation. High-resolution transmission electron microscopy (HRTEM) revealed that as the current density increased from 10 mA/cm² to 50 mA/cm², the corrosion product transitioned from a crystalline NiOOH structure to an amorphous structure, which correlated with a reduced corrosion resistance. The heterogeneous microstructure enhances durability, offering a cost-effective and alloy-free alternative for offshore applications. These findings provide a theoretical and experimental basis for designing advanced corrosion-resistant coatings. Full article

Fe-based amorphous and nanocrystalline alloys, such as FINEMET and its improved variants, are highly valued as green energy-saving materials due to their unique magnetic properties, including high permeability, low coercivity, and near-zero saturation magnetostriction. These characteristics have enabled their extensive use in power electronics and information technology. However, the full potential of these alloys remains unfulfilled due to insufficient understanding of their stress sensitivity. This study focuses on the development history, heat treatment, annealing processes, chemical composition, and underlying mechanisms of Fe-based amorphous and nanocrystalline alloys, aiming to provide insights into stress-induced magnetic anisotropy and guide the development of greener and more efficient soft magnetic materials. Full article

This work systematically investigated the effects of warm shot peening (WSP) on the microstructure evolution, residual stress, and microhardness of the Mg-8Gd-3Y-0.4Zr (GW83) alloy by X-ray diffraction line profile analysis, transmission electron microscopy, and X-ray stress analyzer and hardness tester. The results indicated that severe plastic deformation induced by WSP resulted in a gradient nanostructure in the GW83 alloy, accompanied by significant compressive residual stress. In contrast to conventional SP, WSP led to working softening due to the dynamic recrystallization behavior. The formation of nanograins in the GW83 alloy during WSP occurs in three steps: (i) at an early stage, the introduction of a high density of dislocations and a few deformation twins subdivide bulk grains into substructures; (ii) through the processes of dislocation gliding, accumulation, and rearrangement, these substructures undergo further refinement, gradually evolving into ultrafine grains; and (iii) the inhomogeneous ultrafine grains develop into nanograins through dislocation-assisted lattice rotation and dynamic recrystallization. Full article

In recent decades, substantial progress has been made in embedding molecules, nanocrystals, and nanograins into nanofibers, resulting in a new class of hybrid functional materials with exceptional physical properties. Among these materials, functional nanofibers exhibiting ferroelectric, piezoelectric, pyroelectric, multiferroic, and nonlinear optical characteristics have attracted considerable attention and undergone substantial improvements. This review critically examines these developments, focusing on strategies for incorporating diverse compounds into nanofibers and their impact on enhancing their physical properties, particularly ferroelectric behavior and nonlinear optical conversion. These developments have transformative potential across electronics, photonics, biomaterials, and energy harvesting. By synthesizing recent advancements in the design and application of nanofiber-embedded materials, this review seeks to highlight their potential impact on scientific research, technological innovation, and the development of next-generation devices. Full article

TiNi-based alloys are widely utilized in various engineering and medical applications. This study presents a newly developed and optimized technology for producing TiNi wires with a diameter of 40 μm utilizing a combined mechano-chemical treatment and drawing process. The resulting thin wires were tested and characterized using multiple methods to determine their structural, phase, and mechanical properties. The structure of the TiNi wires, designed for use as textile implants in reconstructive medicine, features a TiNi metal matrix (B2 and B19′ phases) at the core and a surface oxide layer. A key structural characteristic of these wires is the presence of fine nanograins averaging 15–17 nm in size. No texturizing of the metallic material was observed during repeated plastic deformations throughout the drawing process. The applied mechano-chemical treatment aimed to modify the structure of the wires’ surface oxide layer. Specifically, reducing the thickness and roughness of this layer decreased the friction coefficient of the alloy during drawing, thus significantly reducing the number of breaks during production. At the same time, the cryogenic treatment of the final product was found to stabilize the martensitic phase B19′, which reduces the Young’s modulus by 10 GPa. Consequently, this newly developed methodology enhances the material’s quality and reduces labor costs during production. Full article

The aerosol deposition (AD) method utilizes high kinetic-energy submicron powders to impact and form a film on a substrate. It is a highly efficient deposition method, capable of producing films or coatings with a strong interfacial bonding and a dense nano-grain structure without thermal assistance. In this work, PbZr_0.53Ti_0.47O₃ (PZT53/47) films (~1.2 μm thick) were deposited on Pt/Ti/Si(100) substrates via the AD method. After a conventional annealing process (700 °C for 1 h), these PZT53/47 films displayed a dense, crack-free, nano-grained morphology, corresponding to an optimal electrical performance. A large maximum polarization (P_max = 70 μC/cm²) and a small coercive field (E_c = 104 kV/cm) were achieved under the maximum applicable electric field of 1.6 MV/cm. The PZT53/47 films also exhibited a large small-field dielectric constant of ~984, a high tunability of 72%, and a low leakage current of ~3.1 × 10⁻⁵ A/cm² @ 40 V. Moreover, the transverse piezoelectric coefficient (e_31.f) of these AD-processed films was as high as −4.6 C/m², comparable to those of sputter-deposited PZT53/47 films. These high-quality PZT53/47 thick films have broad applications in piezoelectric micro-electromechanical systems. Full article

Fracture toughness is a critical indicator for the application of NiTi alloys in medical fields. We propose to enhance the fracture toughness of NiTi alloys by controlling the spatial grain size (GS) gradient. Utilizing rolling processes and heat treatment technology, three categories of NiTi alloys with distinct spatial GS distributions were fabricated and subsequently examined through multi-field synchronous fracture tests. It is found that the one with a locally ultra-high GS gradient (20 nm−3.4 μm) has significantly enhanced fracture toughness, which is as high as 412% of that of the normally distributed nano-grains with an average GS of 8 nm and 178% of that of the coarse-grains with an average GS of 100 nm. Theoretical analysis reveals that in such a gradient structure, phase transition in the coarse-grained matrix greatly absorbs the surface energy of subcritical and stable propagation. Meanwhile, the locally non-uniform GS distribution leads to deviation and tortuosity of the crack path, increasing the critical fracture stress. Furthermore, the nanocrystalline clusters distributed in the form of network nodes reduce the stress intensity factor due to their higher elastic modulus compared to the coarse-grained matrix. This work provides guidance for developing new gradient nanostructured NiTi alloys with high fracture toughness. Full article

In this paper, the structure characteristics and magnetic properties of Fe₈₃Si₆B₆P_1.5C_1.5Cu₁Nb₁ amorphous alloy ribbons annealed at 550 °C for different times were systematically investigated using X-ray diffraction, vibrating sample magnetometer, and atom probe chromatography. The results show that high-density Cu atomic clusters of appropriate sizes help to stabilize the α-Fe(Si) phase and improve the uniformity of the grains to enhance the soft magnetic properties. The solubility difference between the α-Fe(Si) phase and the B-rich phase, the formation of a localized amorphous structure in the transition region, and the inhibition of nanograin growth. However, when the annealing time is extended, the size of the α-Fe(Si) grains decreases, the grain boundary density increases and secondary phases such as Cu clusters become pinning sites for magnetic domain walls. This leads to a decrease in soft magnetic properties, an increase in hard magnetic properties, and a rapid increase in coercivity. When annealed at 550 °C for 20 min, the number density of Cu atomic clusters was 9.18 × 10²² m⁻³, the spherical equivalent radius was 1.13 ± 0.29 nm, and the ribbons had good soft magnetic properties with a coercivity of 4.59 Oe. The saturation magnetic induction reached a peak value of 185.11 emu/g. Full article