Search Results (1,039)

Accelerated industrialization and surging energy demands have led to continuously rising atmospheric CO₂ concentrations. Developing sustainable methods to reduce atmospheric CO₂ levels is crucial for achieving carbon neutrality. Concurrently, the rapid development of new energy vehicles has driven a significant increase in demand for lithium-ion batteries (LIBs), which are now approaching an end-of-life peak. Efficient recycling of valuable metals from spent LIBs represents a critical challenge. This study employs conventional hydrometallurgical processing to recover valuable metals from spent LIBs. Subsequently, Ni-doped Co₃O₄ (Ni:Co₃O₄) supported on the natural mineral attapulgite (ATP) was synthesized via a sol–gel method. The incorporation of a small amount of Ni into the Co₃O₄ lattice generates oxygen vacancies, inducing a localized surface plasmon resonance (LSPR) effect, which significantly enhances charge carrier transport and separation efficiency. During the photocatalytic reduction of CO₂, the primary product CO generated by the Ni:Co₃O₄/ATP composite achieved a high production rate of 30.1 μmol·g⁻¹·h⁻¹. Furthermore, the composite maintains robust catalytic activity even after five consecutive reaction cycles. Full article

Transition-metal and rare-earth element co-doped ZnO nanoparticles have attracted significant attention due to their potential applications in spintronics and optoelectronics. In this study, Zn_0.95Co_0.01EuxO (x = 0.01–0.05) nanoparticles were synthesized using the sol–gel technique. The estimated stress, strain, and crystallite sizes of the synthesized Co/Eu co-doped ZnO nanoparticles were calculated using the Williamson–Hall method, and their electron spin resonance (ESR) properties were investigated to examine the effect on their magnetic and structural properties. X-ray diffraction (XRD) analysis confirmed the presence of a single-phase structure. Surface morphology, elemental composition, crystal quality, defect types, density, and magnetic behavior were characterized using scanning electron microscope (SEM), electron-dispersive spectroscopy (EDS), and ESR techniques, respectively. The effect of Eu concentration on the linewidth (ΔBpp) and g-factor in the ESR spectra was studied. By correlating ESR results with the obtained structural properties, room-temperature ferromagnetic behavior was identified. Full article

Novel high-entropy perovskite oxide powders were synthesized using a sol-gel process. The B-site contained five cations: chromium, cobalt, iron, manganese, and nickel. The B-site cations were present on an equiatomic basis. The A-site cation was lanthanum, with calcium doping. The amount of A-site doping varied from 0 to 30 at%, yielding a composition of La_1−xCa_x(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O_3−δ. The resulting perovskite powders were pressurelessly sintered in air at 1400 °C for 2 h. Sintered densities were measured, and the grain structure was imaged via scanning electron microscopy to investigate the effect of doping. Samples were cut and polished, and their resistance was measured at varying temperatures in air to obtain the electrical conductivity and the mechanism that governs it. Plots of electrical conductivity as a function of composition and temperature indicate that the increased configurational entropy of the perovskite materials has a demonstrable effect. Full article

Silica/alumina composite particles were synthesized via the sol–gel method to promote fine dispersion and homogenous mixing. Aluminum chloride hydroxide served as the alumina precursor, while amorphous silica, obtained from rice husk, was directly incorporated into the alumina sol. Following synthesis, the material was calcined at 1000 °C, yielding an α-cristobalite form of silica and corundum-phase alumina. These hybrid particles were introduced into polymer composites at reinforcement levels of 1 wt.%, 3 wt.%, and 5 wt.%. Mechanical behavior was evaluated through three-point bending tests, Shore D hardness measurements, and controlled-energy impact testing. Among the formulations, the 3 wt.% composite exhibited optimal performance, displaying the highest flexural modulus and strength, along with enhanced impact resistance. Hardness increased with rising particle content. Fractographic analysis revealed that the 3 wt.% loading produced a notably rougher fracture surface, correlating with improved energy absorption. In contrast, the 5 wt.% composite, although harder than the matrix and other composites, exhibited diminished toughness due to particle agglomeration. Full article

Complex oxides with the general formula Gd₂(Ti_1−xZr_x)₂O₇ are promising candidates for radioactive waste immobilization due to their capacity to withstand radiation by dissipating part of the free energy driving defect creation and phase transitions. In this study, samples with varying zirconium content (xZr = 0.00, 0.15, 0.25, 0.375, 0.56, 0.75, 0.85, 1.00) were synthesized via the sol–gel method and thermally treated at 500 °C to obtain nanosized powders mimicking the defective structure of irradiated materials. Synchrotron-based techniques were employed to investigate their structural properties: High-Resolution X-ray Powder Diffraction (HR-XRPD) was used to assess long-range structure, while Pair Distribution Function (PDF) analysis and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy provided insights into the local structure. HR-XRPD data revealed that samples with low Zr content (xZr ≤ 0.25) are amorphous. Increasing Zr concentration led to the emergence of a crystalline phase identified as defective fluorite (xZr = 0.375, 0.56). Samples with the highest Zr content (xZr ≥ 0.75) were fully crystalline and exhibited only the fluorite phase. The experimental G(r) functions of the fully crystalline samples in the low r range are suitably fitted by the Weberite structure, mapping the relaxations induced by structural disorder in defective fluorite. These structural insights informed the subsequent EXAFS analysis at the Zr-K and Gd-L₃ edges, confirming the splitting of the cation–cation distances associated with different metal species. Moreover, EXAFS provided a local structural description of the amorphous phases, identifying a consistent Gd-O distance across all compositions. Full article

A ceramic–metal composite was synthesized using sol–gel and electrospinning methods to serve as a SERS substrate. The precursors used were tetraethyl orthosilicate, aluminum nitrate, and zirconium, and polyvinylpyrrolidone was added to electrospun nonwoven fibrous membranes. The membranes were sintered, decorated with silver nanoparticles. The enhancement substrates were made of fibers of cylindric morphology with an average diameter of approximately 190 nm, a smooth surface, and 9 nm spherical particles decorating the surface of the fibers. The enhancement capacity of the substrates was tested using pyridine, methyl orange, methylene blue, crystal violet, and Eriochrome black T at different concentrations with Raman spectroscopy to determine whether the size and complexity of the analyte has an impact on the enhancement capacity. Enhancement factors of 2.53 × 10², 3.06 × 10¹, 2.97 × 10³, 4.66 × 10³, and 1.45 × 10³ times were obtained for the signal of pyridine, methyl orange, methylene blue, crystal violet, and Eriochrome black T at concentrations of 1 nM. Full article

This study presents the first successful integration of Fe₃O₄ and Li_0.5Cr_0.5Fe₂O₄ into a well-defined core/shell nanostructure through a two-step synthesis that combines co-precipitation and sol–gel auto-combustion methods. Unlike conventional composites, the core/shell design effectively suppresses the magnetic dead layer and promotes exchange coupling at the interface, leading to enhanced saturation magnetization, superior magnetic heating (specific absorption rate; SAR), and improved dielectric properties. Our research introduces a novel interfacial engineering strategy that simultaneously optimizes both magnetic and dielectric performance, offering a multifunctional platform for applications in magnetic hyperthermia, electromagnetic interference (EMI) shielding, and microwave devices. Full article

Bioactive glasses are known for their surface reactivity and ability to bond with bone tissue through the formation of hydroxyapatite. This study investigates the effects of substituting ultrapure water with natural geothermal waters from the Azores in the sol–gel synthesis of 45S5 and MgO-modified bioglasses. Using high-resolution X-ray photoelectron spectroscopy (XPS), we examined how the mineral composition of the waters influenced the chemical environment and network connectivity of the glass surface. The presence of trace ions, such as Mg²⁺, Sr²⁺, Zn²⁺, and B³⁺, altered the silicate structure, as evidenced by binding energy shifts and peak deconvolution in O 1s, Si 2p, P 2p, Ca 2p, and Na 1s spectra. Thermal treatment further promoted polymerization and reduced hydroxylation. Our findings suggest that mineral-rich waters act as functional agents, modulating the reactivity and structure of bioactive glass surfaces in eco-sustainable synthesis routes. Full article

Polyethersulfone (PES) membranes are essential in separation processes; however, their inherent hydrophobicity can limit their effectiveness in water-intensive applications. This study aims to enhance PES membranes by modifying them with a NiFe₂O₄–nanoclay composite nanoparticle to improve both their hydrophilicity and photocatalytic potential as a photocatalytic membrane. The nanoparticles were synthesized using the sol–gel auto-combustion method and incorporated into PES membranes through mixed-matrix embedding (1 wt% and 3 wt%) and surface coating. X-ray diffraction confirmed the cubic spinel structure of the composite nanoparticles, which followed the second order kinetic reaction during the photodegradation–adsorption of crystal violet. The mixed-matrix membranes displayed a remarkable 170% increase in water flux and a 25% improvement in mechanical strength, accompanied by a slight decrease in contact angle at 1 wt% of nanoparticle loading. In contrast, the surface-coated membranes demonstrated a significant reduction in contact angle to 18°, indicating a highly hydrophilic surface and increased roughness. All membranes achieved high dye removal rates of 98–99%, but only the coated membrane system exhibited approximately 50% photocatalytic degradation, following mixed kinetics. These results highlight the critical importance of surface modification in advancing PES membranes, as it significantly reduces fouling and enhances water–material interaction qualities essential for future filtration and photocatalytic applications. Exploring hybrid strategies that combine both embedding and coating approaches may yield even greater synergies in membrane functionality. Full article

The aim of the present research was to synthesize protective composite layers from biodegradable cellulose and biocompatible, sol–gel-derived silica cryogel. An important task in the present work was to achieve good applicability on distinct (smooth and rough) surfaces of various materials (from metallic to ceramic). The aim was to utilize the composite layers as thermal and electric insulation coating. The investigation put some effort into the enhancement of mechanical strength and the elasticity of the thin layer as well as a reduction in its water solubility. The removal of the alkali content leads successfully to a significant reduction in water solubility (97 wt% → 1–3 wt%). Adhesion properties were measured using a specialized measurement technique developed in our laboratory. Treatments of the substrate surface, such as alkaline or acidic etching (i.e., Na₂CO₃, HF, water glass), mechanical roughening, or the application of a thin alkali-containing primer layer, strongly increase adhesion. SEM analyses revealed the interactions between the matrix and the reinforcement phase and their morphology. Full article

The design, synthesis, and application of composite materials based on manganese dioxide (MnO₂) for energy storage are pivotal in advancing efficient, sustainable, and high-performance energy storage systems. The MnO₂ is widely recognized for its abundance, low cost, environmental friendliness, and excellent electrochemical properties, making it a promising candidate for use in supercapacitors, batteries, fuel cells, and other energy storage systems. This study offers a comprehensive overview of how various materials influence the performance of MnO₂ as an energy storage medium. Specifically, the design of composite materials is examined with respect to morphological control, integration with conductive additives, doping strategies, and structural engineering, all of which impact the final material properties. Additionally, the influence of diverse synthetic techniques—including hydrothermal synthesis, electrochemical deposition, sol–gel processing, co-precipitation, and templating methods—is evaluated. The latest attempts through which the developed composites showcase improved structural stability, inherent conductivity, and electron mobility compared to the original first material are presented in this review article. The presented results have been quite promising for the synthesis of great-performing materials with improved electrochemical data compared to that of MnO₂ alone, competing with other significant energy storage materials. This review highlights future prospects for the development of state-of-the-art devices, large-scale production applications, and the use of environmentally friendly materials and methods. It is anticipated that this research will provide valuable insights to facilitate further improvements in performance and broaden the scope of practical applications in this rapidly evolving field of composite materials. Full article

Phased-array ultrasonic transducers using sol–gel composites face challenges in terms of polarization uniformity when using conventional corona poling. Pb(Zr, Ti)O₃ (PZT)/PZT composites with a thickness of 25 µm were fabricated on 3 mm thick titanium substrates, and the samples were poled by AC poling, DC poling, and corona discharge poling at RT. It was found that the polarization direction could be controlled by the voltage off-phase angle. When poling was performed with a voltage off-phase angle of 90°, applied voltage of 200 V (rms), 10 cycles, and frequency of 1 Hz, average values and standards of measured piezoelectric constant d₃₃ of −35.1 ± 0.8 pC/N and ultrasonic sensitivity of 11.4 ± 0.1 dB were obtained. Furthermore, the AC-poled samples demonstrated smaller variations in d₃₃ and ultrasonic sensitivity compared with the corona-poled samples, and higher values of d₃₃ and ultrasonic sensitivity compared with the DC-poled samples, indicating the potential of AC poling for PZT/PZT sol–gel composites with large areas. Full article

Triethylamine (TEA), a volatile organic compound (VOC), has important applications in industrial production. However, TEA has an irritating odor and potential toxicity, making it necessary to develop sensitive TEA gas sensors with high efficiency. This study focused on preparing LaFeO₃ nanoparticles modified by SnS₂ nanosheets (SnS₂/LaFeO₃ composite) using a hydrothermal method together with sol–gel technique. According to the comparison results of the gas-sensing performance between pure LaFeO₃ and SnS₂/LaFeO₃ composite with varying composition ratios, 5% SnS₂/LaFeO₃ sensor had a sensitivity for TEA that was 3.2 times higher than pure LaFeO₃ sensor. The optimized sensor operates at 140 °C and demonstrates strong stability, selectivity, and long-term durability. Detailed analyses revealed that the SnS₂ nanosheets enhanced oxygen vacancy (O_V) content and carrier mobility through heterojunction formation with LaFeO₃. This study provides insights into improving gas-sensing performance via p-n heterostructure design and proposes a novel LaFeO₃-based material for TEA detection. Full article

Nanostructured bimetallic IrSn composites deposited on the natural aluminosilicate montmorillonite were synthesized and evaluated as anode electrocatalysts for polymer electrolyte membrane electrolysis cells (PEMECs). The test series prepared via the sol–gel method consisted of samples with 30 wt. % total metal content and varying Ir:Sn ratio. The performed X-ray diffraction analysis and high-resolution transmission electron icroscopy registered very fine nanostructure of the composites with metal particles size of 2–3 nm homogeneously dispersed on the support surface and also intercalated in the basal space of its layered structure. The electrochemical behavior was investigated by cyclic voltammetry and steady-state polarization techniques. The initial screening was performed in 0.5 M H₂SO₄. Then, the catalysts were integrated as anodes in membrane electrode assemblies (MEAs) and tested in a custom-made PEMEC. The electrochemical tests revealed that the catalysts with Ir:Sn ratio 15:15 and 18:12 wt. % demonstrated high efficiency toward the oxygen evolution reaction during repetitive potential cycling and sustainable performance with current density in the range 140–120 mA cm⁻² at 1.6 V vs. RHE during long-term stability tests. The results obtained give credence to the studied IrSn/MMT nanocomposites to be considered promising, cost-efficient catalysts for the oxygen evolution reaction (OER). Full article

A composite photocatalyst of ceria–cadmium supported on mesoporous SBA-15 silica was synthesized and employed for the aqueous methylene blue (MB) degradation. The composites were prepared using an incipient wetness impregnation technique and a conventional sol–gel approach with triblock copolymer P123 as a structure-directing agent for SBA-15 preparation, enabling the uniform dispersion of CeO₂ and Cd species within the SBA-15 framework. The physicochemical properties of both CeO₂/SBA-15 and Cd-CeO₂/SBA-15 composites were analyzed using small-angle and wide-angle XRD, FT-IR spectroscopy, SEM, TEM, EDX spectroscopy, N₂ physisorption at 77 K, and UV-Vis spectroscopy. The findings revealed that the SBA-15 support retained its well-ordered hexagonal mesostructure in both the ceria–SBA-15 and SBA-15-supported cadmium–ceria (Cd-CeO₂) composites. The highest degradation efficiency of 96.40% was achieved under optimal conditions, and kinetic analysis using the Langmuir–Hinshelwood model indicated that the MB degradation process followed pseudo-first-order kinetics, with a strong correlation coefficient (R² = 0.9925) and a rate constant (k) of 0.02532 min⁻¹. Under irradiation, the Cd-CeO₂/SBA-15 composites exhibited superior photocatalytic activity compared to the pristine components, owing to the synergistic interaction between ceria and cadmium, enhanced light absorption, and improved charge carrier separation. The recyclability test demonstrated that the degradation efficiency decreased slightly from 96.40% to 94.86% after three cycles, confirming the stability and reusability of Cd-CeO₂/SBA-15 composites. The photocatalytic process demonstrated a favorable electrical energy per order (EE/O) value of 281.8 kWh m⁻³, indicating promising energy efficiency for practical wastewater treatment. These results highlight the excellent photocatalytic performance and durability of the synthesized Cd-CeO₂/SBA-15 composites, making them promising candidates for facilitating the photocatalytic decomposition of MB and other dye molecules in water treatment applications. Full article