Search Results (40)

Background/Objectives: Magnetic nanoparticles, particularly iron oxide-based materials, such as magnetite (Fe₃O₄), have gained significant attention as contrast agents in medical imaging This study aimsto syntheze and characterize Fe₃O₄-based core–shell nanostructures, including Fe₃O₄@TiO₂ and Fe₃O₄@SiO₂, and to evaluate their potential as tunable contrast agents for diagnostic imaging. Methods: Fe₃O₄, Fe₃O₄@TiO₂, and Fe₃O₄@SiO₂ nanoparticles were synthesized via co-precipitation at varying temperatures from iron salt precursors. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of Fe–O bonds, while X-ray diffraction (XRD) was employed to determine the crystalline phases and estimate average crystallite sizes. Morphological analysis and particle size distribution were assessed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and transmission electron microscopy (TEM). Magnetic properties were investigated using vibrating sample magnetometry (VSM). Results: FTIR spectra exhibited characteristic Fe–O vibrations at 543 cm⁻¹ and 555 cm⁻¹, indicating the formation of magnetite. XRD patterns confirmed a dominant cubic magnetite phase, with the presence of rutile TiO₂ and stishovite SiO₂ in the coated samples. The average crystallite sizes ranged from 24 to 95 nm. SEM and TEM analyses revealed particle sizes between 5 and 150 nm with well-defined core–shell morphologies. VSM measurements showed saturation magnetization (Ms) values ranging from 40 to 70 emu/g, depending on the synthesis temperature and shell composition. The highest Ms value was obtained for uncoated Fe₃O₄ synthesized at 94 °C. Conclusions: The synthesized Fe₃O₄-based core–shell nanomaterials exhibit desirable structural, morphological, and magnetic properties for use as contrast agents. Their tunable magnetic response and nanoscale dimensions make them promising candidates for advanced diagnostic imaging applications. Full article

In this study, Fe₃O₄@SiO₂@TiO₂ (FS-FT (0 g)) photocatalysts, featuring a magnetic core–shell structure, and Fe-doped Fe₃O₄@SiO₂@Fe-TiO₂ (FS-FT (x g)) photocatalysts, were fabricated via the sol–gel method. Structural and compositional analyses of the processed samples were systematically conducted through X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), surface-sensitive X-ray photoelectron spectroscopy (XPS), and optical property assessment via UV-Vis diffuse reflectance spectroscopy (UV-DRS). The results show that TiO₂ on the outer layer of FS-FT (0 g) and FS-FT (x g) has an anatase structure, and that Fe is doped into FS-FT (x g). The photodegradation of methyl orange (MO) using FS-FT (0 g) and FS-FT (x g) with various Fe doping levels was evaluated in both pure MO (C₀ = 10 mg/L) and MO-Na₂SO₄-blended solutions. Under irradiation with high-pressure mercury lamps, the removal rates of MO using FS-FT (0 g) and FS-FT (0.36 g) in pure MO solution reached 90.25% and 99% at 25 min, respectively, which indicates that FS-FT (0.36 g) can enhance photocatalytic performance. The removal rates of MO using FS-FT (0 g) and FS-FT (0.36 g) in MO-Na₂SO₄-blended solution (C₀ = 10 mg/L, C_Na2SO4 = 12.5 g/L) reached 92.38% and 97.16% at 25 min, respectively. The removal rate of MO using FS-FT (0.36 g) decreased in MO-Na₂SO₄-blended solution in the previous 25 min, which indicates that Na₂SO₄ can inhibit degradation using FS-FT (0.36 g). The degradation experiments of MO-Na₂SO₄-blended solutions with different concentrations of Na₂SO₄ using FS-FT (0.36 g) showed that as the concentration of Na₂SO₄ increases, the inhibitory effect becomes more pronounced. Recovery and recycling experiments confirmed that the photocatalyst exhibited robust degradation performance over multiple cycles. Kinetic analysis of the photocatalytic data, based on a first-order model, was conducted to explore the underlying degradation principles. Full article

This study investigates the rheological behavior of oil well cement pastes (OWCPs) modified with core/shell TiO₂@SiO₂ (nTS) nanoparticles and polycarboxylate-ether (PCE) superplasticizers at different temperatures (25, 45, and 60 °C). Results show that nTS particles increased static and dynamic yield stresses and the apparent viscosity of the cement slurries due to an increased solid volume fraction and reduced free water availability. The increase in the slurry dispersion by adding PCE superplasticizers enhanced the effect of the nanoparticles on the rheological parameters. Oscillation rheometry demonstrated that nTS nanoparticles enhanced the structural buildup, while PCE retarded hydration. Furthermore, slurries hydrated at 60 °C experienced higher initial values of the elastic modulus and a faster exponential increase in this rheological parameter due to the acceleration of the cement hydration. Full article

TiC provides a promising potential for high-temperature microwave absorbers due to its unique combination of thermal stability, high electrical conductivity, and robust structural integrity. C@TiC/SiO₂ composites were successfully fabricated using a simple blending and cold-pressing method. The effects of C@TiC’s absorbent content and temperature on the dielectric and microwave absorption properties of C@TiC/SiO₂ composites were investigated. The addition of C@TiC from 10 wt.% to 30 wt.% not only endows the composites with a higher dielectric constant and dielectric loss, but also with a greater high-temperature stability in terms of dielectric and microwave absorption properties. The composite with 30 wt.%C@TiC demonstrates a strong microwave absorption capability with a minimum reflection loss (RL_min) of −55.87 dB, −48.49 dB, and −40.36 dB at room temperature, 50 °C, and 100 °C, respectively; the 50 wt.%C@TiC composite exhibits an enhanced high-temperature microwave absorption performance with an RL_min of −16.13 dB and −15.72 dB at 200 °C and 300 °C, respectively. This study demonstrates that the TiC-based absorbers present an innovative solution for high-temperature microwave absorption, providing stability, versatility, and adaptability in extreme operational environments. Full article

The synthesis and characterization of ZnO/TiO₂, SiO₂/TiO₂, Al₂O₃/TiO₂, and Al_1.9Co_0.1O₃/TiO₂ core/shell nanoparticles (NPs) is reported. The NPs were used for photocatalytic degradation of brilliant blue E-4BA under UV and visible light irradiation, monitored by high-performance liquid chromatography and UV-vis absorption spectroscopy. The size of the NPs ranged from 10 to 30 nm for the core and an additional 3 nm for the TiO₂ shell. Al₂O₃/TiO₂ and Al_1.9Co_0.1O₃/TiO₂ showed superior degradation under UV and visible light compared to ZnO/TiO₂ and SiO₂/TiO₂ with complete photodecomposition of 20 ppm dye in 20 min using a 10 mg/100 mL photocatalyst. The “Co-doped” Al_1.9Co_0.1O₃/TiO₂ NPs show the best performance under visible light irradiation, which is due to increased absorption in the visible range. DFT-calculated band structure calculations confirm the generation of additional electronic levels in the band gap of γ-Al₂O₃ through Co³⁺ ions. This indicates that Co-doping enhances the generation of electron–hole pairs after visible light irradiation. Full article

“Core/shell” composites are based on a ferrite core coated by two layers with different properties, one of them is an isolator, SiO₂, and the other is a semiconductor, TiO₂. These composites are attracting interest because of their structure, photocatalytic activity, and magnetic properties. Nanocomposites of the “core/shell” МFe₂O₄/SiO₂/TiO₂ (М = Zn(II), Co(II)) type are synthesized with a core of MFe₂O₄ produced by two different methods, namely the sol-gel method (SG) using propylene oxide as a gelling agent and the hydrothermal method (HT). SiO₂ and TiO₂ layer coating is performed by means of tetraethylorthosilicate, TEOS, Ti(IV) tetrabutoxide, and Ti(OBu)₄, respectively. A combination of different experimental techniques is required to prove the structure and phase composition, such as XRD, UV-Vis, TEM with EDS, photoluminescence, and XPS. By Rietveld analysis of the XRD data unit cell parameters, the crystallite size and weight fraction of the polymorphs anatase and rutile of the shell TiO₂ and of the ferrite core are determined. The magnetic properties of the samples, and their activity for the photodegradation of the synthetic industrial dyes Malachite Green and Rhodamine B are measured in model water solutions under UV light irradiation and simulated solar irradiation. The influence of the water matrix on the photocatalytic activity is determined using artificial seawater in addition to ultrapure water. The rate constants of the photocatalytic process are obtained along with the reaction mechanism, established using radical scavengers where the role of the radicals is elucidated. Full article

In this paper, Fe₃O₄@SiO₂@TiO₂ and N-doped Fe₃O₄@SiO₂@N-TiO₂ photocatalysts with magnetic core-shell structures were prepared using a multi-step synthesis method. The materials were analyzed using various techniques, such as X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), selected-area electron diffraction patterns (SAED), and X-ray photoelectron spectroscopy (XPS). The results indicated that the prepared samples had an anatase structure, and N was successfully doped. Fe₃O₄@SiO₂@TiO₂ and Fe₃O₄@SiO₂@N-TiO₂ with different amounts of nitrogen doping were used for the study of photocatalytic degradation of methyl orange (MO) in pure MO solution, and in MO and Na₂SO₄ (MO-Na₂SO₄) mixed solution, respectively. The average photocatalytic degradation rate of MO in pure MO solution with three different batches each of Fe₃O₄@SiO₂@TiO₂ and Fe₃O₄@SiO₂@N-TiO₂ (3 mL of NH₄OH used for doping) under high-pressure mercury lamp irradiation reached 85.25% ± 2.23% and 95.53% ± 0.53%, respectively. The average photocatalytic degradation rate of MO in the MO-Na₂SO₄ mixed solution with three different batches each of Fe₃O₄@SiO₂@TiO₂ and Fe₃O₄@SiO₂@N-TiO₂ (3 mL of NH₄OH used for doping) under the same irradiation condition reached 90.46% ± 3.33% and 97.79% ± 2.09%, respectively. The results showed that Na₂SO₄ can promote photocatalytic degradation of MO. The experiment of recycling photocatalysts showed that there was still a good degradation effect after five cycles. Finally, the first-order kinetic model and the photocatalytic degradation mechanism were investigated. Full article

Herein, Fe₃O₄ core-TiO₂/mesoSiO₂ and Fe₃O₄ core-mesoSiO₂/TiO₂ double shell nanoparticles were prepared by first (R1) and second (R2) routes and applied for the removal of methylene blue. The reported adsorption capacities for R1-0.2, R1-0.4 and R2 samples were 128, 118 and 133 mg.g⁻¹, respectively, which were obtained after 80 min as equilibrium contact time, and pH of 6 using a methylene blue concentration of 200 ppm. The adsorption of methylene blue using the prepared Fe₃O₄ core-meso SiO₂/TiO₂ double shell was analyzed by kinetic and isotherms models. In addition, thermodynamic investigations were applied to assess the spontaneous nature of the process. The obtained results confirmed that the pseudo-second order model is well fitted with the adsorption data and the Freundlich-isotherm assumption suggested a multilayer adsorption mechanism. In addition, results of the thermodynamic investigation indicated that ΔG° was in the range of −2.3 to −6.8 kJ/mol for R1-0.2, −2.8 to −6.3 kJ/mol for R1-0.4 and −2.0 to −5.2 kJ/mol for R2. In addition, the ΔH° and ΔS° values were found in the range of 26.4 to 36.19 kJ.mol⁻¹ and 94.9 to 126.3 Jmol⁻¹ K⁻¹, respectively. These results confirm that the surfaces of Fe₃O₄ core-mesoSiO₂/TiO₂ and Fe₃O₄ core-TiO₂/mesoSiO₂ double shell exhibit a spontaneous tendency to adsorb methylene blue from the aqueous solutions. The achieved performance of Fe₃O₄ core-meso SiO₂/TiO₂ and Fe₃O₄ core-TiO₂/meso SiO₂ double shell as adsorbent for methylene blue removal will encourage future research investigations on the removal of a broad range of contaminants from wastewater. Full article

Silicon has been proven to be one of the most promising anode materials for the next generation of lithium-ion batteries for application in batteries, the Si anode should have high capacity and must be industrially scalable. In this study, we designed and synthesised a hollow structure to meet these requirements. All the processes were carried out without special equipment. The Si nanoparticles that are commercially available were used as the core sealed inside a TiO₂ shell, with rationally designed void space between the particles and shell. The Si@TiO₂ were characterised using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The optimised hollow-structured silicon nanoparticles, when used as the anode in a lithium-ion battery, exhibited a high reversible specific capacity over 630 mAhg⁻¹, much higher than the 370 mAhg⁻¹ from the commercial graphite anodes. This excellent electrochemical property of the nanoparticles could be attributed to their optimised phase and unique hollow nanostructure. Full article

SiO₂@TiO₂ core-shell nanoparticles were successfully synthesized via a simple, reproducible, and low-cost method and tested for methylene blue adsorption and UV photodegradation, with a view to their application in wastewater treatment. The monodisperse SiO₂ core was obtained by the classical Stöber method and then coated with a thin layer of TiO₂, followed by calcination or hydrothermal treatments. The properties of SiO₂@TiO₂ core-shell NPs resulted from the synergy between the photocatalytic properties of TiO₂ and the adsorptive properties of SiO₂. The synthesized NPs were characterized using FT-IR spectroscopy, HR-TEM, FE–SEM, and EDS. Zeta potential, specific surface area, and porosity were also determined. The results show that the synthesized SiO₂@TiO₂ NPs that are hydrothermally treated have similar behaviors and properties regardless of the hydrothermal treatment type and synthesis scale and better performance compared to the SiO₂@TiO₂ calcined and TiO₂ reference samples. The generation of reactive species was determined by EPR, and the photocatalytic activity was evaluated by the methylene blue (MB) removal in aqueous solution under UV light. Hydrothermally treated SiO₂@TiO₂ showed the highest adsorption capacity and photocatalytic removal of almost 100% of MB after 15 min in UV light, 55 and 89% higher compared to SiO₂ and TiO₂ reference samples, respectively, while the SiO₂@TiO₂ calcined sample showed 80%. It was also observed that the SiO₂-containing samples showed a considerable adsorption capacity compared to the TiO₂ reference sample, which improved the MB removal. These results demonstrate the efficient synergy effect between SiO₂ and TiO₂, which enhances both the adsorption and photocatalytic properties of the nanomaterial. A possible photocatalytic mechanism was also proposed. Also noteworthy is that the performance of the upscaled HT1 sample was similar to one of the lab-scale synthesized samples, demonstrating the potentiality of this synthesis methodology in producing candidate nanomaterials for the removal of contaminants from wastewater. Full article

The development of pulse power systems and electric power transmission systems urgently require the innovation of dielectric materials possessing high-temperature durability, high energy storage density, and efficient charge–discharge performance. This study introduces a core-double-shell-structured iron(II,III) oxide@barium titanate@silicon dioxide/polyetherimide (Fe₃O₄@BaTiO₃@SiO₂/PEI) nanocomposite, where the highly conductive Fe₃O₄ core provides the foundation for the formation of microcapacitor structures within the material. The inclusion of the ferroelectric ceramic BaTiO₃ shell enhances the composite’s polarization and interfacial polarization strength while impeding free charge transfer. The outer insulating SiO₂ shell contributes excellent interface compatibility and charge isolation effects. With a filler content of 9 wt%, the Fe₃O₄@BaTiO₃@SiO₂/PEI nanocomposite achieves a dielectric constant of 10.6, a dielectric loss of 0.017, a high energy density of 5.82 J cm⁻³, and a charge–discharge efficiency (η) of 72%. The innovative aspect of this research is the design of nanoparticles with a core-double-shell structure and their PEI-based nanocomposites, effectively enhancing the dielectric and energy storage performance. This study provides new insights and experimental evidence for the design and development of high-performance dielectric materials, offering significant implications for the fields of electronic devices and energy storage. Full article

The development of novel and active photocatalysts to industrialize photocatalysis technology is still a challenging task. In this work, a novel method is presented to prepare TiO₂/SiO₂ NSs by covering SiO₂ nanospheres (NSs) with titanate-nanodiscs (TNDs) followed by calcination. In this regard, SiO₂ NSs are first synthesized and then TNDs are deposited on the SiO₂ NSs using a layer-by-layer deposition technique. The morphology of the prepared samples is analyzed via SEM and TEM analyses before and after the deposition. The analysis of metal (Cu, Pt, and Ni) loading on calcined TNDs/SiO₂ NSs reveals the highest specific surface area (109 m²/g), absorption wavelength extension (up to 420 nm), and photocatalytic activity for the Cu-loaded sample. In addition, studying the effect of metal content shows that loading 3% Cu leads to the highest photocatalytic activity. Finally, it is demonstrated that H₂S treatment can improve the photocatalytic activity by around 15%. These findings suggest the calcined TNDs/SiO₂ NSs are a versatile photocatalyst with potential applications in other processes such as hydrogen production and CO₂ valorization. Full article

TiO₂ and core–shell SiO₂@TiO₂ nanoparticles were synthesized by sol-gel process at different calcination temperatures. Mesoporous hollow TiO₂ composites were prepared by etching SiO₂ from SiO₂@TiO₂ nanoparticles with alkali solution. X-ray diffraction (XRD), Scanning electron microscope (SEM),Transmission electron microscope (TEM), and N₂ adsorption–desorption isotherms, and Roman and Diffuse reflectance spectroscopy (DRS) were employed to characterize the synthesized materials. The effects of different calcination temperatures on the morphology, crystallinity, phase composition, and photocatalytic activity of the prepared materials were investigated in detail. It was found that the calcination temperature altered the phase structure, crystallinity, morphology, specific surface area, and porous structure. Additionally, it was verified that SiO₂ could inhibit the transfer of TiO₂ from anatase phase to rutile phase under high temperature calcination (850 °C). The hollow TiO₂ calcined at 850 °C showed the highest photocatalytic efficiency of 97.5% for phenol degradation under UV irradiation. Full article

Iron-based soft magnetic composites (SMCs) are the key components of high-frequency electromagnetic systems. Selecting a suitable insulating oxide layer and ensuring the integrity and homogeneity of the heterogeneous core–shell structure of SMCs are essential for optimizing their magnetic properties. In this study, four types of SMCs—Fe-Si-Cr/ZrO₂, Fe-Si-Cr/TiO₂, Fe-Si-Cr/MgO, and Fe-Si-Cr/CaO—were prepared via ball milling, followed by hot-press sintering. The differences between the microscopic morphologies and magnetic fproperties of the Fe-Si-Cr/AO_x SMCs prepared using four different metal oxides were investigated. ZrO₂, TiO₂, MgO, and CaO were successfully coated on the surface of the Fe-Si-Cr alloy powders through ball milling, forming a heterogeneous Fe-Si-Cr/AO_x core–shell structure with the Fe-Si-Cr alloy powder as the core and the metal oxide as the shell. ZrO₂ is relatively hard and less prone to breakage and refinement during ball milling, resulting in a lower degree of agglomeration on the surface of the composites and prevention of peeling and collapse during hot-press sintering. When ZrO₂ was used as the insulation layer, the magnetic dilution effect was minimized, resulting in the highest resistivity (4.2 mΩ·cm), lowest total loss (580.8 kW/m³ for P_10mt/100kHz), and lowest eddy current loss (470.0 kW/m³ for P_{ec 10mt/100kHz}), while the permeability stabilized earlier at lower frequencies. Full article

Silicon-based anode materials are considered one of the highly promising anode materials due to their high theoretical energy density; however, problems such as volume effects and solid electrolyte interface film (SEI) instability limit the practical applications. Herein, silicon nanoparticles (SiNPs) are used as the nucleus and anatase titanium dioxide (TiO₂) is used as the buffer layer to form a core-shell structure to adapt to the volume change of the silicon-based material and improve the overall interfacial stability of the electrode. In addition, silver nanowires (AgNWs) doping makes it possible to form a conductive network structure to improve the conductivity of the material. We used the core-shell structure SiNPs@TiO₂/AgNWs composite as an anode material for high-efficiency Li-ion batteries. Compared with the pure SiNPs electrode, the SiNPs@TiO₂/AgNWs electrode exhibits excellent electrochemical performance with a first discharge specific capacity of 3524.2 mAh·g⁻¹ at a current density of 400 mA·g⁻¹, which provides a new idea for the preparation of silicon-based anode materials for high-performance lithium-ion batteries. Full article