Search Results (682)

Fe-based amorphous and nanocrystalline alloys are essential core materials for high-efficiency distribution transformers, high-frequency transformers, and power electronic transformers, owing to their high saturation magnetic flux density (B_s), low coercivity (H_c), low core loss, and excellent high-frequency response. This review summarizes recent progress in the modulation of soft magnetic properties, covering composition design, heat treatments, structural engineering, and transformer applications. For compositional design, a central issue is how to achieve high B_s while retaining sufficient Glass-forming ability (GFA), and appropriate additions of metalloid and transition-metal elements provide an effective route to this balance. Conventional isothermal, stress, magnetic-field, and rapid annealing processes enable structural relaxation, nanocrystallization, and anisotropy modulation. Ultrafine nanocrystals, amorphous/nanocrystalline transitional structures, and gradient and multilayer structures further improve overall performance through grain refinement, interface engineering, and domain optimization. Key engineering challenges include continuous ribbon casting, heat-treatment uniformity, winding-induced residual stress, and practical operating conditions. Future advances require the integration of in situ characterization, multiscale modeling, and machine learning, alongside advances in continuous heat treatment and low-stress manufacturing, to facilitate wider application in transformers. Full article

Hydrogen storage remains a major challenge for the large-scale implementation of hydrogen energy technologies. In this study, the hydrogen sorption behavior of Pd–Ti–Mg alloys synthesized by spark plasma sintering (SPS) was investigated using a combination of experimental characterization and numerical modeling. The phase composition and structural state of the synthesized material were analyzed by X-ray diffraction (XRD), while hydrogen absorption measurements were performed at different temperatures to evaluate its sorption behavior. A finite-difference numerical model was developed in MATLAB to simulate hydrogen diffusion, concentration distribution, thermally stimulated desorption, relaxation-stimulated gas evolution, pressure–composition–temperature (PCT) behavior, and hydrogen absorption–desorption kinetics. XRD analysis indicated a multiphase structure consisting predominantly of Pd₂Mg₅ and Pd₅Ti₃ intermetallic phases, together with residual Ti. Williamson–Hall analysis confirmed the nanocrystalline state of the synthesized material, with an average crystallite size of approximately 20–30 nm and microstrains of (3–5) · 10⁻³. The individual calculated crystallite sizes ranged from 18 to 35 nm, whereas the representative average value was approximately 20–30 nm. Experimental measurements demonstrated a pronounced temperature dependence of hydrogen uptake, with the highest measured hydrogen content reaching approximately 0.40 wt.% at 500 °C. Numerical simulations indicated that hydrogen transport is predominantly diffusion-controlled, resulting in a pronounced concentration gradient across the sample thickness. The thermally stimulated desorption model predicted a maximum hydrogen evolution rate of approximately 1.8 · 10⁻⁸ atoms s⁻¹ at 560–600 °C. The calculated PCT characteristics demonstrated a strong dependence of equilibrium hydrogen content on temperature and hydrogen pressure, with higher hydrogen contents predicted at lower temperatures and elevated pressures. Simulated absorption kinetics showed a rapid approach to hydrogen saturation within 10–30 s, whereas hydrogen desorption approached equilibrium within 80–120 s, depending on the applied pressure. The combined experimental and numerical results demonstrate the complementary roles of Pd-, Ti-, and Mg-containing phases in the hydrogen sorption behavior of the material, with Pd-containing intermetallic phases contributing to hydrogen dissociation and transport, while Ti- and Mg-containing phases contribute to hydrogen retention and storage. These findings demonstrate the potential of Pd–Ti–Mg-based intermetallic materials as candidate materials for solid-state hydrogen storage and related hydrogen-energy applications. Full article

Tribological loading can substantially modify the near-surface structures of nanocrystalline metals, yet the microstructural evolution of worn tribolayers remains insufficiently understood. Here, an electrodeposited nanocrystalline Ni coating with an average grain size of ~10 nm was investigated under ball-on-disk sliding against AISI 52100 steel in laboratory air at sliding speeds of 0.03 and 0.3 m/s with identical normal load and sliding distance. The worn surfaces and subsurface regions were characterized using laser confocal microscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and four-dimensional scanning transmission electron microscopy (4D-STEM). The steady-state coefficient of friction was higher at 0.03 m/s (~0.05) than at 0.3 m/s (~0.02). Low-speed sliding produced greater material pile-up and surface topographic changes, accompanied by the formation of an ~1 μm-thick porous oxide-rich tribolayer containing transferred Fe and isolated Ni-rich regions. In contrast, high-speed sliding generated a thinner (~300 nm) oxide layer above a ~150 nm metallic lamellar subsurface zone. 4D-STEM orientation analysis of reliably indexed near-surface regions further revealed local crystallographic orientation features consistent with ${\mathrm{A}}_1^{\mathrm{*}}$/${\mathrm{A}}_2^{\mathrm{*}}$ and C components in the quasi-lamellar region at 0.03 m/s, whereas additional shear-related components, including C, B/$\overline{\mathrm{B}}$, and ${\mathrm{A}}_1^{\mathrm{*}}$/${\mathrm{A}}_2^{\mathrm{*}}$, were identified in the highly deformed subsurface region under the 0.3 m/s condition. Combined TEM observations and 4D-STEM crystallographic analysis demonstrate that different sliding conditions produce distinct tribolayer architectures, subsurface deformation structures, and crystallographic evolution in nanocrystalline Ni/AISI 52100 steel contacts. Full article

Hydroxyapatite (HAp) possesses exceptional compositional flexibility, allowing for extensive cationic, anionic, and coupled substitutions that can modify its structural, mechanical, electronic, magnetic, catalytic, and biological properties. However, experimental identification of dopant locations and charge-compensation mechanisms remains challenging, particularly in nanocrystalline, calcium-deficient, and multiphase materials. This review evaluates first-principles studies of ion-substituted HAp, with particular emphasis on substitution-site preferences, defect association, charge compensation, thermodynamic stability, configurational effects, surfaces, hydration, and comparison with experimental observables. Unlike earlier reviews that primarily catalogued individual dopants and their calculated effects, the present work critically examines the methodological and defect-chemical assumptions underlying reported substitution mechanisms, including charge compensation, configurational sampling, chemical-potential definitions, hydration, finite-temperature effects, and experimental validation. The literature demonstrates that dopant site preference is not an intrinsic and concentration-independent property of an element. Instead, it depends on supercell size, dopant concentration, hydroxyl ordering, oxidation and spin states, compensating defects, chemical potentials, hydration, temperature, and the presence of other impurities. Many apparent discrepancies between studies arise from small simulation cells, incomplete configurational sampling, inconsistent formation-energy definitions, or calculations performed for assumed compositions without explicit charge compensation. The strongest structural assignments combine defect energetics with directly calculated spectroscopic parameters. Future predictive models should treat substituted HAp as a condition-dependent ensemble of interacting defects and integrate large-scale configurational sampling, finite-temperature methods, hydrated surfaces, machine learning, and advanced spectroscopic validation. Full article

The catalytic performance of copper-modified strontium titanate-based materials (SrTi_1−xCu_xO₃, where x = 0.02, 0.04, 0.06, and 0.10) in the NH₃-SCR and NH₃-SCO processes was studied. The catalytic materials were obtained by the modified Pechini method and characterized in terms of structural properties (XRD, XAS), surface composition (XPS), microstructural properties (SEM/EDS, SSA measurements), and reducibility (TPR). Catalytic activity, selectivity to N_2, and long-term stability in the NH₃-SCR and NH₃-SCO processes were experimentally verified. The catalytic materials consisted of agglomerates of nanocrystalline perovskite grains with homogeneously distributed copper, except for the material with the highest copper content. The catalytic activity of these materials was found to be highly dependent on copper loading, with STO_4Cu emerging as the optimal catalyst—the NO conversion in NH₃-SCR on the level of 88% and exceptional N₂ selectivity (>98%) was obtained at 275 °C, despite an extremely low Cu content (below 2 wt.%). Lower copper content (STO_2Cu) in catalysts appears to limit the low-temperature activity, which correlates with a higher Cu(I) contribution. On the other hand, the higher copper loading (STO_10Cu) triggers their aggregation. Twelve-hour isothermal stability tests confirmed robust long-term performance and stable N₂ selectivity for both the NH₃-SCR (at 250 °C) and NH₃-SCO (at 375 °C) reactions, demonstrating the potential of finely dispersed, low-loading copper perovskites for environmental catalysis. Full article

Nanocrystalline (NC) alloys hold significant promise as structural alloys due to their superior mechanical properties over the traditional coarser grained microcrystalline alloys. Often, there is an optimal range of mean grain size for most metals about which maximum material strength can be realized. In the context of NC alloys, stabilization of the grain size in this optimal range is one of the primary synthesis challenges. A large volume fraction of NC alloy microstructure is occupied by grain boundaries (GBs). Since GBs increase the internal surface energy of the system, during solidification and grain growth phases, there is a tendency to minimize GBs through grain coarsening. However, in NC alloys, phenomena like GB–solute segregation and solute precipitation are active and mitigate grain growth and thus stabilize the desired small grains. Numerically modeling these phenomena of GB–solute interactions, and the evolution of these stabilized GBs under mechanical load, is of immense interest to the NC alloy community. To enrich the numerical modeling formulations available in this space, we present here a phase-field-method-based numerical framework to model GB segregation, solute precipitation and effect of external loading on NC alloys. While some of these effects have been modeled in isolation, a unified treatment of the solute–GB segregation-related effects and its coupling with mechanics has not be considered in the literature. We present a three-dimensional, finite element method (FEM)-based, finite-strain phase-field formulation for modeling grain evolution and microstructure stabilization in NC alloys. Beyond the formulation and its computational implementation, various case studies demonstrate the applicability of this framework. Further, thermodynamic and kinetic arguments are provided based on the evolution of GB energy to explain the effects of solute drag, GB pinning and mechanical deformation. Full article

Soft magnetic materials determine the efficiency, size, thermal burden, and reliability of transformers, inductors, electrical machines, electromagnetic interference (EMI) components, and magnetic sensors. This review differs from property-by-property surveys by using a condition-aware, application-driven framework: magnetic performance is compared only together with frequency, peak magnetic flux density, temperature, waveform, direct current (DC) bias, geometry, and processing route. After a concise treatment of coercivity, permeability, saturation polarization, magnetostriction, and loss mechanisms, the major material families are quantitatively compared in terms of magnetic performance, processing, cost, and industrial maturity. The review then maps these families onto grid transformers, high-speed electrical machines, wide-bandgap power converters, integrated magnetics, wireless power transfer, aerospace electrical systems, and radiofrequency components. Particular attention is given to the trade-offs among saturation polarization, permeability, core loss, mechanical strength, thermal stability, manufacturability, and sustainability. Recent advances in strong and ductile soft magnets, wide-temperature ferrites, vortex and easy-plane composites, mixed-powder soft magnetic composites, nanocrystalline flake-ribbon cores, and additive manufacturing are assessed by technology maturity. A prioritized roadmap identifies near-term needs for standardized condition-specific data and manufacturing control, medium-term opportunities in magnetic–thermal co-design and digital twins, and longer-term prospects for adaptive, self-healing, and GHz magnetic architectures. The resulting framework is intended to support both material development and defensible industrial material selection. Full article

In the era of global energy transition, the development of third-generation photovoltaic technologies, such as dye-sensitized solar cells, has emerged as a paramount challenge in materials engineering. This study is dedicated to the synthesis and implementation of graphene quantum dots as eco-friendly sensitizers within DSSC architectures. The GQDs were synthesized via a microwave-assisted hydrothermal route using biodegradable organic precursors, providing a “green” alternative to conventional, toxic heavy-metal-based materials. The nanocrystalline structure and optoelectronic properties of the sensitizer were verified through UV-Vis and visual photoluminescence assessment. A focal point of this research was the optimization of the GQD concentration on the mesoporous surface of the titanium dioxide photoanode. Measurements were conducted utilizing a custom-designed experimental setup integrated with 3D-printed (FDM) components and an Arduino microcontroller, ensuring precise data acquisition under controlled illumination conditions (405–625 nm). The results indicated an optimal operational point at a fivefold dilution of the stock solution (0.4 g/dm³), which yielded the highest open-circuit voltage ($V_{\mathrm{oc}}$) of 545.4 mV under UV irradiation. The decline in photovoltaic performance observed at higher concentrations was attributed to excessive nanostructure agglomeration, which effectively blocked the mesopores of the semiconductor. Furthermore, the demonstrated high chemical capacitance of the system imparts electrochemical capacitor-like characteristics to the cell, enabling energy stabilization under fluctuating illumination. To elucidate the underlying sensitization mechanisms at the atomic level, computational simulations were conducted utilizing the MACE machine-learning potential and the GFN2-xTB semi-empirical method. The theoretical models revealed that the formation of stable covalent Ti–O–C bridges (chemisorption) is imperative for establishing strong interfacial electronic coupling. Solvation models and molecular dynamics (MD) at 300 K confirmed the thermodynamic and operational robustness of the hybrid system in an aqueous electrolyte. Ultimately, this combined experimental and theoretical work conclusively demonstrates that graphene quantum dots represent an efficient, highly stable, and non-toxic alternative to classic molecular dye sensitizers. Full article

Among the vast array of technologies available for surface modification of materials, sputtering emerges as one of the most versatile methods through coating deposition. Included in the family of physical vapor deposition (PVD) techniques, sputtering allows the production of coatings with a great variety of characteristics, based on a bottom-up approach that forms coatings from individual species (atoms or ions). This versatility is achieved by controlling: (i) the layer architecture, from monolithic to multilayers, (ii) the structures, from amorphous to nanocrystalline or nanocomposite, until highly crystallized, including epitaxial; (iii) the morphologies, from very porous through columnar or zig-zag to very dense and featureless; (iv) the chemical composition, allowing the deposition of metallic, polymeric, ceramic or composite materials types. In this paper, after a brief introduction of sputtering as a deposition technology, we will review the application of sputtering for depositing protective coatings to which an extra functionality is provided: (a) aesthetic color; (b) high-temperature lubrication; and (c) temperature sensing ability. Full article

In the present work, graphene-modified zinc oxide (ZnO-rGO) and fluorine-doped tin oxide (FTO) thin films were successfully fabricated using a simple, low-cost pulsed spray pyrolysis technique. The structural, morphological, optical, electrical, and surface electronic properties of the deposited films were systematically characterized. X-ray diffraction (XRD) analysis confirmed the formation of polycrystalline ZnO- and SnO₂-based phases with crystallite sizes in the nanometer range. The crystallographic parameters, microstrain, and dislocation density of the deposited films were found to be influenced by the incorporation of reduced graphene oxide (rGO) and fluorine dopants. Scanning electron microscopy (SEM) revealed compact and homogeneous surface morphologies with good film coverage and well-defined nanocrystalline features. Optical characterization demonstrated the wide-bandgap semiconducting behavior of the deposited films, with optical bandgap energies ranging from 3.262 to 3.312 eV for the ZnO-rGO films and from 3.91 to 4.01 eV for the FTO films. Kelvin probe measurements yielded work-function values in the range of approximately 5.0–5.2 eV, indicating favorable surface electronic characteristics suitable for optoelectronic applications. Furthermore, fluorine incorporation enhanced the dielectric response of the SnO₂ films, particularly in the low-frequency region owing to increased interfacial polarization effects. The obtained results demonstrate that pulsed spray pyrolysis provides a simple, cost-effective, and efficient route for fabricating ZnO-rGO and FTO thin films with desirable structural, optical, electrical, and surface electronic properties. These findings highlight the considerable potential of the developed materials for transparent electrodes and a wide range of optoelectronic applications. Full article

Threatening environmental resources such as water, air and soil, and thus indirectly threatening biodiversity, through rapid, uncontrolled and non-ecological industrial production systems must be prevented through appropriate purification methods. In this research, the sorption of Reactive blue 19 anthraquinone dye from aqueous solution was carried out in a batch system using nano zinc–manganese ferrite carbonate (ZnMn–Fe₂O₄–CO₃) synthesized by the co-precipitation method. Various factors affecting the sorption activity of the material were examined, and the most suitable conditions were determined to be pH 2 and ZnMn–Fe₂O₄–CO₃ concentration of 0.25 g/L, whereby an equilibrium sorption capacity of 1463.10 mg/g was achieved. The ZnMn–Fe₂O₄–CO₃ removal efficiency was found to be 88.48% in effluent from a textile manufacturing industry. Utilizing FTIR, SEM, EDS, XRD, TGA and BET methods, the material’s morphological and structural characteristics were thoroughly investigated and reported. Regarding the kinetic and isotherm models that were analyzed, the Langmuir and pseudo-second-order (PSO) models provided the best fit to the aforementioned sorption system. Thermodynamic data confirmed the spontaneity of the sorption reaction and the exothermic nature of the process. An extensive study of ZnMn–Fe₂O₄–CO₃ demonstrated its high efficiency in removing RB19 dye, as well as the safety and simplicity of the synthesis, the cost-effectiveness of the sorption process, and the possibility of regeneration and reuse over multiple cycles. These findings highlight the potential of ZnMn–Fe₂O₄–CO₃ for advanced water and wastewater purification technologies targeting anthraquinone dyes. Full article

W-modified TiAlN coatings were developed as hydrogen permeation barrier coatings for magnetic materials. TiAlN and TiAlN-W coatings with comparable thicknesses of approximately 1.5 μm were deposited on Fe and NdFeB substrates by physical vapor deposition. GIXRD and SEM results showed that W modification was associated with a change from weakly crystalline, columnar TiAlN to a more compact, low-crystallinity W-modified Ti–Al–N coating with amorphous/nanocrystalline features inferred from the broad diffraction response. XPS analysis identified low-valence W-related species, such as W–N/Wⁿ⁺-related bonding, together with overlapping Ti 3p/W–O_x contributions and surface oxide/oxynitride species, indicating a modified surface and near-surface chemical environment. Electrochemical hydrogen permeation tests on Fe substrates showed that TiAlN reduced the steady-state current density from 2.54 ± 0.86 to 0.55 ± 0.08 μA cm⁻², corresponding to a permeation reduction factor of 4.68 ± 0.16. In contrast, TiAlN-W showed no obvious hydrogen breakthrough during the 15,000 s test period, and the current density remained below the practical detection limit of 0.01 μA cm⁻², giving a lower-bound permeation reduction factor of >250. In high-pressure H₂ exposure tests, the TiAlN-W-coated NdFeB sample remained macroscopically intact after exposure to 5 MPa H₂ at 23 °C for 24 h, whereas the uncoated and TiAlN-coated samples were pulverized. The markedly improved hydrogen permeation resistance is associated primarily with the more compact cross-sectional morphology and W-modified coating structure. Full article

In this study, pure hydroxyapatite (HAp) was successfully produced by using eggshells. The eggshells were collected locally and calcined to get CaO from them. The CaO powder was reacted with diammonium hydrogen phosphate in a mechanochemical method using attritor milling. A portion of the synthesized samples was subjected to a second calcination process at 900 °C to investigate the thermal effects on the material. The structures of the samples were investigated by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. The as-prepared HAp appeared to be nanocrystalline with low-intensity reflections, which transformed into a highly crystalline hexagonal phase after heat treatment, as revealed by XRD analysis. Quantitative analysis revealed the thermal evolution of the secondary Ca(OH)₂ phase, due to the thermal decomposition into CaO without causing HAp decomposition into tricalcium phosphates. FTIR analysis showed characteristic phosphate bands for both samples, but the calcined sample displayed sharper peaks and a clear loss of residual water and carbonates. SEM observations also highlighted the major morphological transformation. The highly aggregated as-prepared nanoparticles formed larger, well-defined grains. Notably, the calcined sample also exhibited a rough, textured surface with a macroporous network with interconnected channels. EDS analysis confirmed a Ca-P-O-rich composition, where the elevated Ca/P ratio (Ca/P = 2.28) suggested the presence of secondary calcium-rich phases. These structural, chemical, and morphological characteristics suggest that eggshell-derived HAp, with or without a second heat treatment, has high potential and may be optimized for different applications in bone tissue engineering. However, biological performance was not evaluated in this study. Full article

Tungsten trioxide (WO₃) is the most widely studied cathodic electrochromic (EC) material, serving as the core component of energy-efficient smart windows, displays, and optical modulation devices. Post-deposition annealing, as a critical post-processing technique, precisely regulates the microstructure, crystallinity, oxygen vacancy concentration, and electronic structure of WO₃ thin films, thereby directly determining their EC performance. This review summarizes the research progress of annealing effects on WO₃ films, focusing on the synergistic regulation of annealing temperature, atmosphere, and dwell time. It elaborates on the fundamental EC mechanisms of amorphous and crystalline WO₃, including polaron hopping and free-electron Drude behavior, and analyzes the influence of different deposition methods (magnetron sputtering, sol–gel, electrodeposition, etc.) on the annealing response of films. The optimal annealing windows for balancing optical modulation, coloration efficiency, switching speed, and cycling stability are clarified: moderate temperatures (200–350 °C) and inert/air atmospheres yield mixed amorphous–nanocrystalline structures with optimal oxygen vacancy content. Current challenges such as the inherent contrast–stability trade-off and thermal budget limitations of flexible substrates are discussed, and future directions including spatially resolved annealing, interface co-design, and machine learning-assisted optimization are prospected. This work provides a theoretical reference and process guidance for the development of high-performance WO₃-based EC devices. Full article

This review shows that lignocellulosic biomass is not merely an abundant feedstock for nanocellulose production but a strategic platform for building the next generation of sustainable, high-performance materials, integrating feedstock diversity, processing logic, characterization, market direction, and translational applications into a single narrative. Comparing woody and non-woody biomass through the lens of processability, recalcitrance, and value creation while showing why agricultural residues are increasingly central to low-cost, circular nanocellulose production beyond the usual acid-hydrolysis-centered discussion by emphasizing enzymatic hydrolysis as a lower-energy, lower-toxicity alternative while still acknowledging the persistent industrial advantages and environmental costs of chemical and mechanical routes. A further strength of this review is its effort to bridge structure and function: it links extraction strategy to morphology, crystallinity, thermal stability, and surface chemistry, then connects these properties to real applications in packaging, drug delivery, electronics, filtration, energy storage, and biomedical systems. Its distinctive contribution lies in showing that the future of nanocellulose depends not only on how it is extracted but also on how intelligently the biomass source, processing route, material performance, and market need are aligned. Full article