Search Results (719)

Nickel ferrite (NiFe₂O₄) is one of the most studied inverse-spinel ferrites because it combines moderate saturation magnetization, comparatively high electrical resistivity, chemical stability, and broad synthesis flexibility. Yet the literature shows that the measured structure and magnetism of NiFe₂O₄ are not intrinsic constants; they evolve strongly with dimensionality, size, thickness, strain state, cation distribution, surface spin disorder, and synthesis pathway. This review develops a unified theoretical and literature-based interpretation of how dimensionality reshapes the structural and magnetic behavior of NiFe₂O₄ across bulk ceramics, nanoparticles, one-dimensional nanostructures, polycrystalline thin films, and ultrathin epitaxial films. The review is anchored in the two uploaded nickel ferrite attachments and expanded using internet-sourced journal literature on spinel inversion, surface effects, mechanochemical synthesis, sputtered and pulsed laser deposited thin films, and epitaxial ultrathin-film anomalies. The central novelty of this article is the formulation of a dimensionality-dependent framework in which the observed magnetic response is governed by a competition among three coupled factors: (i) the cation-distribution function, which controls the A–B superexchange balance and therefore the net ferrimagnetic moment; (ii) the microstructural coherence function, which measures how crystallinity, strain, defects, and anti-phase boundaries preserve or degrade exchange continuity; and (iii) the surface/interface spin-order parameter, which quantifies the loss or reconfiguration of magnetic order at free surfaces and buried interfaces. Within this framework, bulk NiFe₂O₄ behaves as a near-equilibrium inverse spinel with relatively stable magnetization, whereas nanoscale NiFe₂O₄ experiences strong spin canting and finite-size suppression due to the growing fraction of disordered surface spins. Thin films introduce a distinct regime in which strain, texture, anti-phase boundaries, substrate mismatch, and growth kinetics determine both anisotropy and magnetization. In ultrathin epitaxial films, off-equilibrium cation redistribution and interface-controlled electronic reconstruction may even generate magnetization values far above bulk expectations. The review also compares major synthesis routes—solid-state reaction, sol–gel, co-precipitation, hydrothermal growth, reactive milling, combustion, pulsed laser deposition, and radio-frequency sputtering—and explains why each route biases the final dimensionality-dependent properties differently. A set of word-style equations is provided to formalize spinel inversion, finite-size suppression, anisotropy scaling, coercivity trends, and superparamagnetic crossover. Beyond summarizing the field, the review proposes a regime map linking dimensionality to characteristic structural defects and magnetic signatures, and it identifies unresolved questions concerning the true origin of enhanced magnetization in ultrathin NiFe₂O₄, the interplay between anti-phase boundaries and strain, and the distinction between intrinsic inversion changes and extrinsic substrate artifacts. The resulting article offers a submission-ready, originality-focused review that positions dimensionality as the master variable governing structure–magnetism correlations in nickel ferrite. Full article

To address the inherent drawbacks of micro-arc oxidation (MAO), this study employed MAO combined with sol–gel processing to fabricate ZrO₂/Al₂O₃-CeO₂ composite coatings on ZrH_1.8 surfaces, aiming to solve the hydrogen evolution problem of zirconium hydride (ZrH_1.8) materials in high-temperature environments. By adjusting the aluminum concentration in the sol (0.1~0.5 mol/L), a series of composite thin films were prepared on the ZrH_1.8 surface using MAO combined with dip-coating, and their surface morphology and phase composition were characterized. The microstructure, morphology, and hydrogen barrier performance of the thin films were systematically analyzed using scanning electron microscopy (SEM), XRD, laser confocal microscopy, and quadrupole mass spectrometry. The results showed that the composite coating had a low surface porosity, with a maximum hydrogen permeation reduction factor (PRF) of 18.1. When the aluminum concentration was 0.4 mol/L, the relative content of tetragonal ZrO₂ (T-ZrO₂) reached 13.88%, the surface porosity was as low as 4.87%, and the initial temperature of hydrogen loss was increased to 730 °C. Mechanism analysis indicated that CeO₂ may stabilize the tetragonal phase (T-ZrO₂) of ZrO₂ through solid solution effects and inhibit the phase transformation to monoclinic phase (M-ZrO₂), thereby reducing cracks caused by volume expansion. Meanwhile, the synergistic effect of the MAO densified layer and the sol–gel sealed porous layer significantly reduced the coating porosity and blocked hydrogen diffusion paths, thus achieving excellent hydrogen barrier performance under high-temperature conditions. Full article

Driven by the growing demand for functional textiles featuring excellent waterproofness, moisture permeability and mechanical robustness in outdoor sportswear, medical protection and technical apparel, traditional pongee—despite its desirable softness, high wrinkle resistance and good stability as an ideal substrate fabric—is severely restricted in further application by its intrinsically poor hydrostatic pressure resistance in extremely wet environments. Accordingly, we developed a modified waterborne polyurethane (WPU) coating for pongee substrates to fabricate functional textiles that maintain high hydrostatic pressure resistance while possessing good mechanical properties and increased UV absorption. In this study, by using the sol–gel method, an amorphous silicon dioxide (SiO₂) coating layer was constructed on the surface of titanium dioxide (TiO₂) particles, forming silica-modified titania particles (SiO₂/TiO₂). These SiO₂-modified particles were subsequently physically blended with an anionic waterborne polyurethane system that had been previously modified with a polyester-type modifier A to enhance its hydrostatic pressure resistance. The resulting composite coating was designed to combine the high hydrostatic pressure resistance inherited from the modified WPU matrix, the mechanical reinforcement and increased UV absorption contributed by SiO₂/TiO₂, and satisfactory water repellency on fabric substrates. The results indicate that the incorporation of an appropriate amount of modifier A into the prepolymer system significantly enhances hydrostatic pressure resistance while maintaining high elongation at break. At a SiO₂/TiO₂ loading of 0.2 wt%, the composite film exhibits optimal comprehensive performance, characterized by superior mechanical properties, low water absorption, and static water contact angles exceeding 100° for coated fabrics. SiO₂/TiO₂ composite WPU coatings substantially improve hydrostatic pressure resistance across various fabrics, with 380T polyester taffeta demonstrating the best performance. This resistance remains remarkably stable after standard washing, indicating excellent wash fastness and practical applicability. Full article

Background: Overexpression of immune cell populations leads to self-amplifying cytokine loops, contributing to chronic inflammation in both allograft rejection and autoimmune conditions. Tacrolimus (TAC), despite being a potent immunosuppressant, has limitations; its systemic adverse effects include nephrotoxicity, neurotoxicity, and high variability in tissue exposure in patients. Currently available therapeutic options are limited by the lack of targeted and localized drug delivery systems, resulting in ineffective control over drug-release behavior. Moreover, TAC being highly lipophilic poses challenges for formulation development. To address these gaps, this study focuses on developing a thermoresponsive hydrogel platform comprising distinct nanocarriers for localized delivery of TAC. The nanocarriers include nanoemulsion (NE) and micelles as TAC carriers, and their particle sizes are specifically engineered at the nanoscale for differential release behavior and to support immune cell targeting (macrophages and T-cells). Incorporation into a thermoresponsive hydrogel matrix enables it to act as a local depot at the injection site and deliver TAC with a slow, extended-release profile. Methods: TAC was loaded into a coconut-rich lipid-phase-based NE via high-pressure microfluidization. Simultaneously, TAC-loaded micelles were optimized using a full-factorial design of experiments (DoE) and manufactured via the thin-film hydration method. Both nanocarriers were evaluated for long-term colloidal stability assessments. Hydrogels were produced maintaining aseptic conditions for sterile batch production. Rheological characterization was performed to assess sol-gel transition, thermoreversibility, and injectability, and in vitro release studies were conducted to evaluate TAC diffusion from the developed nanoformulations. Results: Developed nanocarriers resulted in distinct particle sizes in NE (80–85 nm) and micelles (15–17 nm) with successful TAC loading maintaining long-term colloidal stability. The developed TAC-loaded dual-nanocarrier hydrogel (Dual-HG) showed thermoresponsive behavior and gelation at 37 °C, forming as a local depot. In vitro release studies showed slow and extended tacrolimus release from hydrogels and demonstrated particle size-dependent release behavior between the NE and micelle. Conclusions: Therefore, our study highlights a novel dual nanocarrier hydrogel platform combining TAC-NE and TAC-micelle for localized delivery. The findings support that nanocarriers can be engineered to modulate drug diffusion behavior. Notably, the dual nanocarrier within a thermoresponsive hydrogel platform can be used to deliver one or multiple drugs locally, minimizing systemic exposure when sustained local immunosuppression is required. The 25 mL scale sterile batch production of hydrogels emphasizes their suitability for future translational applications. Full article

Titanium carbide (TiC) is a technologically important material, which is used in industrial and engineering applications as an abrasive, a wear-resistant material, reinforcement in composites, as well as an electrocatalysis material. This review summarizes the state-of-the-art processes for the synthesis of TiC, for instance, carbothermal reduction, combustion reactions, sol–gel processing, gas phase reaction, and mechanical alloying. Moreover, this review updates the various processes used for the synthesis of nanostructured titanium carbide and its process mechanisms. Nanostructured titanium carbide can be synthesized through optimizing thermal reduction processes, using more reactive titanium-containing precursors, a gas phase reaction or mechanical alloying processes. Under these reaction conditions, reactants are more reactive to overcome the kinetic barriers and the reaction processes proceed at a much lower temperature or have a shorter duration. The sol–gel process allows the formation of nanostructured TiC at a relatively low temperature due to the high reactivity of the sol–gel precursors. Mechanical alloying processing is a versatile method to produce nanostructured TiC. Gas phase processing allows nanostructured TiC formed in particles or in films. Nanostructured TiC has the potential to enhance the performance of TiC as a technological material, which is attractive for various applications in industrial and engineering fields. Full article

As anodized aluminum components are increasingly deployed in high-power optical and precision industrial systems operating in non-vacuum environments, their outgassing behavior has emerged as a critical material reliability concern. In contamination-sensitive optical assemblies, released volatiles can accumulate on nearby surfaces, leading to haze formation, scattering, and progressive optical degradation. The porous anodic oxide layer retains water, hydrogen, dyes, and processing residues that are released under thermal, photonic, and environmental stresses typical of industrial operation. While most qualification data remain vacuum-centric, equivalent evaluation frameworks for ambient environments are limited. This review analyzes surface-driven desorption mechanisms relevant to non-vacuum systems and provides practical guidance for material and process engineers by evaluating mitigation strategies across the anodizing process chain, including fine-grain substrate selection, controlled anodizing with nickel acetate sealing, post-bake stabilization, and alternative dense coatings such as electroless nickel, sol–gel films, and Acktar. The analysis underscores the need for non-vacuum-specific qualification standards to support reliable material selection and long-term system performance. Full article

The need for sustainable and cost-effective thermoelectric materials has brought attention to earth-abundant and mineral compounds, like Cu₂ZnSnS₄ (CZTS). In this work, CZTS nanoparticles (NPs) were synthesized via the sol–gel method using environmentally friendly solvents based on water and ethanol mixtures. The resulting CZTS NPs were then processed into inks through ball milling to produce a thin-film thermoelectric generator (TEG). Structural and microstructural properties were investigated via X-ray diffraction and Raman spectroscopy, confirming the kesterite CZTS phase upon sintering. The chalcogenide exhibited p-type semiconductor behaviour, with a Seebeck coefficient reaching ~69 µV/K at 385 K. Van-der-Pauw measurements of conductivity confirmed a non-degenerate semiconducting behaviour, achieving ~1.77 S/cm at 323 K. A two-leg CZTS thin-film TEG reaching a maximum power output of 32(3) nW at a ΔT ~160 K was used, measured with a home-made setup. The volume-specific power of the generator reached $4\times {10}^{-4}$μW cm⁻³ K⁻². These results point to an effective use of sol–gel-based techniques to produce a functional thermoelectric generator, providing a costless and environmentally friendly approach to CZTS NPs. Full article

With the continuous advancement of display technology and advanced integrated circuits, oxide thin-film transistors (TFTs) have become core devices due to their high mobility, low leakage current and excellent large-area uniformity. To achieve low power consumption, high performance and high reliability, the introduction of high-k gate insulating layers is crucial. Among the numerous high-k materials, hafnium oxide (HfO₂) has attracted significant attention due to its excellent dielectric properties and good compatibility with CMOS processes. In this paper, uniform and dense HfO₂ films were successfully fabricated using the sol–gel method to serve as insulating layers for TFT devices. Through experimental analysis, 400 °C was determined to be the optimal annealing temperature. At this temperature, the effects of replacing SiO₂ with HfO₂ as the insulating layer, as well as the impact of reducing film thickness, on TFT devices were investigated. Ultimately, at an annealing temperature of 400 °C, an 85 nm-thick HfO₂ film achieved the highest on/off current ratio (I_on/off = 1.11 × 10⁶), the lowest subthreshold swing (SS = 0.53 V/dec), the lowest threshold voltage (Vth = −1.1 V) and the lowest off-current ratio (I_off = 2.5 × 10⁻¹² A). It was confirmed that replacing SiO₂ with HfO₂ as the insulating layer is a viable approach for reducing the volume of TFT devices. Full article

Indium hafnium oxide thin-film transistors (TFTs) were prepared by the sol-gel method, and their crystal structures, surface morphologies, chemical compositions, optical and electrical properties were systematically investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) spectroscopy, and a semiconductor parameter analyser. We mainly study the effects of hafnium doping on indium oxide-based thin-film transistors through the following electrical properties, including field-effect mobility (μ FE), carrier concentration, on/off current ratio (Ion/Ioff), threshold voltage (Vth), and subthreshold slope (SS). The oxygen defects concentration decreased from 25.83% to 17.82% when Hf doping was increased to 5 mol%. The effect of Hf doping on the structure, as well as the properties of the Hf-InO_x thin films, was explored and it was found that Hf as a carrier inhibitor can effectively suppress the carrier concentration. This reduces the oxygen vacancy defects and improves the electrical performance of In₂O₃TFTs devices. The doped thin-film transistor exhibits excellent electrical properties with a mobility (μ) of 11.69 cm²/Vs, a threshold voltage (V_TH) of 1.68 V, a subthreshold slope (SS) of 0.68 V/dec, and an on/off current ratio (I_on/I_off) of 10⁷ when the Hf doping level is 3 mol%. Research indicates that the Hf-InO_x thin film prepared by the sol-gel method is a low-cost, high-performance, and widely applicable active layer material. Full article

Mg-doped ZnO (Zn_1−xMg_xO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically investigated as a function of Mg concentration. X-ray diffraction (XRD) patterns confirmed a single-phase hexagonal wurtzite structure with a preferential (₀₀₂) orientation for all compositions, indicating the successful substitution of Mg²⁺ ions into the ZnO lattice. The crystallite size (D₀₀₂) was found to vary between 28.49 and 41.18 nm, while microstrain and stress exhibited non-monotonic behavior depending on Mg content. This behavior reveals a transition from compressive to tensile stress due to lattice distortion and defect formation. Photoluminescence (PL) spectra showed a dominant near-band-edge (NBE) ultraviolet emission, along with broad visible emissions extending from violet to red. Optical constants were accurately extracted using a double-facet-coated substrate (DFCS) model, combined with nonlinear curve fitting using the Nelder–Mead optimization algorithm. The films showed a strong absorption edge at about 370 nm and exceptional optical transparency (≈60–80%) in the visible spectrum. The systematic blue shift in the extinction coefficient with increasing Mg content confirms bandgap engineering in Zn_1−xMg_xO thin films. The refractive index dispersion was successfully modeled using the Cauchy relation, demonstrating composition-dependent tunable optical properties. Depending on the Mg content, the optical bandgap values ranged from approximately 3.265 to 3.315 eV. The band-edge states and optical constants are strongly affected by the combined effects of defect development, Mg-induced lattice distortion, and changes in optical dispersion. These results indicate that sol–gel-derived Mg-doped ZnO thin films with composition-dependent stress states, defect states, and tunable optical properties are promising candidates for UV photodetectors, optical coatings, and transparent optoelectronic devices. Full article

Dye-sensitized solar cells (DSSCs) remain attractive as low-cost photovoltaic devices; however, their practical efficiency is still constrained by electron-transport losses, interfacial recombination, and incomplete light harvesting in conventional titanium dioxide (TiO₂) photoanodes. The effects of TiO₂ film thickness, multi-walled carbon nanotube (MWCNT) incorporation, and multilayer oxide interface engineering on DSSC performance were examined. Degussa P25-TiO₂ photoanodes were first optimized with respect to thickness, after which controlled MWCNT loadings and sequential compact sol–gel TiO₂ and tin dioxide (SnO₂) sublayers were introduced. The optimum pristine P25-TiO₂ photoanode thickness was 9.11 μm, yielding an open-circuit voltage of 0.74 ± 0.01 V, a short-circuit current density of 14.10 ± 0.40 mA/cm², a fill factor of 56.24 ± 1.00%, and a power-conversion efficiency of 5.93 ± 0.20%. The incorporation of 0.025 wt% MWCNTs increased the efficiency to 6.04 ± 0.20%, corresponding to an absolute gain of 0.11 percentage points. The best performance was obtained with the sol–gel SnO₂/sol–gel TiO₂/P25-CNT multilayer photoanode, which delivered 0.74 ± 0.02 V, 16.22 ± 0.40 mA/cm², 57.59 ± 1.00%, and 6.89 ± 0.30%, respectively. FE-SEM, EIS, XRD, Heated Ultrasonic Cleaner and UV–visible analyses indicate that the multilayer architecture preserves porosity, enhances light harvesting, and suppresses interfacial recombination, while the CNT network facilitates charge transport. Full article

Zinc oxide (ZnO) is currently one of the most significant wide-bandgap semiconductor materials, attracting extensive research across diverse fields including materials science, chemistry, physics, medicine, electronics, and power engineering. Its exceptional properties, such as high optical transparency, high electron mobility, chemical stability, and compatibility with low-cost fabrication techniques, have established ZnO as a versatile material with immense application potential. A critical application for ZnO is its role as a transparent conducting oxide (TCO) in modern optoelectronic and photovoltaic devices, as well as in sensors, transparent electronics, and spintronics. To meet the requirements of these advanced applications, precise control over the structural, optical, and electrical properties of ZnO thin films is essential. This is effectively achieved through the selection of specific synthesis methods and intentional modification techniques, such as doping. This review provides a comprehensive overview of the synthesis and modification of ZnO thin films, with a particular focus on how various dopants influence their fundamental characteristics. The work discusses a range of deposition techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), sol–gel methods, spray pyrolysis, and other solution-based approaches. The novelty of this review lies in its comparative analysis of different doping strategies combined with various thin-film deposition techniques, highlighting how specific synthesis routes influence dopant incorporation and ultimately determine functional properties. Furthermore, recent advances in tailoring ZnO thin films are summarized, alongside the identification of key challenges and future research directions. Ultimately, this work aims to provide researchers with a systematic perspective on the synthesis–structure–property relationships in doped ZnO thin films to support the development of optimized materials for next-generation electronic and optoelectronic devices. This review, thus, serves as a comprehensive reference for researchers and engineers seeking to optimize the functionality of ZnO-based thin films for emerging technological applications. Full article

Thin-film cobalt oxides have attracted increasing attention due to their visible-light activity and potential environmental applications. In this work, Co₃O₄ coatings were prepared on glass substrates through a sol–gel dip-coating process followed by thermal treatment at 450, 500, and 550 °C. Structural characterization was carried out using X-ray diffraction (XRD) and Raman spectroscopy. Diffraction patterns, together with the Raman spectra, indicate the formation of the cubic spinel phase of Co₃O₄, while sharper diffraction peaks appeared at higher annealing temperatures, indicating improved crystallinity of the films. Surface morphology was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM observations revealed continuous polycrystalline coatings, whereas AFM measurements showed clear variations in surface topography and roughness produced by thermal treatment. Wettability measurements obtained from contact angle (CA) analysis indicate modifications in the surface properties of the films as the annealing temperature changes. Optical characterization performed by ultraviolet–visible spectroscopy (UV–Vis) showed strong absorption in the visible region with an indirect band gap close to 1.58 eV. Photocatalytic activity was evaluated through the degradation of methylene blue under visible-light irradiation. Degradation efficiencies of approximately 93.9%, 97.4% and 98.7% were obtained after 5 h for films annealed at 450, 500, and 550 °C, respectively. Full article

In this study, the indium (In) composition in amorphous indium gallium zinc oxide (a-IGZO) thin films was systematically varied from 33% to 84% using a sol–gel process. Subsequently, aluminum/IGZO/aluminum (Al/IGZO/Al) metal–semiconductor–metal (MSM) UV photodetectors were fabricated to investigate the influence of composition on the structural, optical, and photoelectric properties. The results indicate that all films maintain an amorphous structure despite the increasing In content, while the ratio of oxygen vacancies, O_vac/(M-O + O_vac), rises from 36% to 52%. Concurrently, the optical bandgap decreases from 2.92 eV to 2.32 eV. Under a bias of 20 V, the dark current increases from 2.11 × 10⁻⁹ A to 1.90 × 10⁻⁵ A as the In content rises. When illuminated by a 360 nm LED with a power density of 8.6 mW/cm², the device with 60% In exhibits a photocurrent-to-dark-current ratio of approximately 10⁴, a responsivity of 19.45 A/W, and a specific detectivity of 8.19 × 10¹² Jones. The response time and recovery time of this device are 39.8 s and 577.4 s, respectively. These findings reveal a competitive relationship between enhanced optical absorption and defect generation induced by In composition, providing valuable guidance for the performance optimization of a-IGZO UV photodetectors through compositional engineering. Full article

Nuclear energy has emerged as a crucial technological solution for ensuring energy security and achieving carbon neutrality goals, given its ultra-high energy density and near-zero carbon emissions against the backdrop of rapid socioeconomic development, increasing energy demands, and accelerated global transition toward low-carbon energy structures. As the core component for energy conversion in nuclear reactors, fuel elements critically determine reactor efficiency and safety performance, with the fission product retention capability of silicon carbide layers in multilayer-coated fuel particles having been thoroughly validated through high-temperature gas-cooled reactor irradiation tests. The precise sphericity control of large-sized UO₂ fuel kernels represents a fundamental requirement for enhancing tristructural isotropic (TRISO) fuel particle performance and advancing Generation IV nuclear power plant development. This study presents a sphericity control strategy based on sol–gel processing that synergistically integrates physicochemical regulation of gelling media with multi-field washing flow field optimization. By implementing silicone oil-mediated interfacial tension gradient control, we effectively suppressed gel sphere destabilization while developing an innovative three-phase sequential washing technique involving kerosene washing, anhydrous ethanol interfacial transition, and ammonia solution replacement, which significantly enhanced mass transfer diffusion in stagnant liquid films and revolutionized fuel microsphere washing technology with improved efficiency and quality. Experimental results demonstrate that this integrated approach increases kernel sphericity qualification to 99.8%, reduces washing solution consumption by 79%, and achieves an average sphericity of 1.03. The research establishes a coupling mechanism between gelling media and multi-field washing processes, elucidating the synergistic effect between interfacial tension regulation and washing optimization, thereby providing both theoretical foundations and engineering application basis for the precision manufacturing of high-performance nuclear fuels. Full article