Search Results (35)

With the continuous advancement of electromagnetic protection technologies, the development of lightweight electromagnetic wave-absorbing materials with excellent absorption performance has become a critical challenge in the field. In this study, commercially available hollow glass microspheres (HGMs) were employed as templates, and Ni²⁺/Co²⁺ metal ions were used to catalyze the polymerization of dopamine (PDA), forming HGM@Ni_xCo_y/PDA precursors. Subsequent high-temperature pyrolysis yielded lightweight composite absorbing materials, denoted as HGM@Ni_xCo_y/C. This material integrates dielectric loss, conductive loss, magnetic loss, and resonance absorption mechanisms, exhibiting outstanding electromagnetic wave absorption properties. The absorption performance can be effectively tuned by adjusting the Ni-to-Co ratio, with the optimal performance observed at an atomic ratio of 2:3. At a filler loading of 20 wt.%, HGM@Ni₂Co₃/C achieved an effective absorption bandwidth (EAB) of 6.83 GHz (ranging from 10.53 to 17.36 GHz) and a minimum reflection loss (RL_min) of −27.26 dB. These results demonstrate that the synergistic combination of hollow glass bubbles and carbon-based magnetic components not only significantly reduces the material density and required filler content but also enhances overall absorption performance, highlighting its great potential in the development of lightweight and high-efficiency electromagnetic wave absorbers. Full article

Developing resource-efficient technologies for producing ceramic materials with specific properties and performance characteristics is one of the most important tasks in modern materials science. As natural resources face depletion, the use of anthropogenic wastes, including fly ash from coal combustion, for the development of new compositions and the production of ceramics with an improved microstructure is of particular significance. The use of PM₁₀ fly ash microspheres in ceramic production will help to reduce particulate matter emissions. In this study, fine narrow fractions of PM₁₀ microspheres were successfully separated from coal fly ash using aerodynamic and magnetic separation. Glass–ceramic materials with a homogeneous microstructure, an open porosity of 0.4–37%, a compressive strength of 5–159 MPa, and acid resistance of up to 99.9% were obtained using narrow fractions. The materials obtained are promising for application as highly porous ceramics, effective microfiltration membranes, and fine-structured technical ceramics, which can be used in installations operating in aggressive media and/or at high temperatures. The ceramic membranes were characterised by high liquid permeability values up to 1194 L·m⁻²·h⁻¹·bar⁻¹. Filtration tests showed that the retention coefficient for dispersed microsilica particles with d_av = 1.9 μm is 0.99. Full article

In this study, the fabrication of magnetic hemicellulosic composite microspheres and the adsorption of copper ions are explored. The microspheres were prepared by the micro-emulsion technique, using Fe₃O₄ nanoparticles and hemicellulose extracted from wheat straw with the ionic liquid B[mim]Cl as a solvent. Fe₃O₄ nanoparticles, synthesized through coprecipitation, were evenly encapsulated within the hemicellulosic microspheres. The Fe₃O₄ nanoparticles measured 10–15 nm in size, while the microspheres had an average diameter of about 20 μm and displayed a saturation magnetization of 35.95 emu/g. The optimal conditions for copper adsorption by the microspheres were found to be a pH of 5.0, a temperature of 323 K, and an initial copper ion concentration of 80 mg/L, resulting in an adsorption capacity of 85.65 mg/g after 24 h. The adsorption kinetics followed a pseudo-second-order model, and the Langmuir isotherm suggested a monomolecular layer adsorption mechanism, with a theoretical maximum capacity of 149.25 mg/g. In summary, the magnetic hemicellulosic microspheres exhibited considerable adsorption potential and favorable recycling capabilities for copper ions. Full article

With the increasing demand for effective electromagnetic wave (EMW) absorbers due to the proliferation of electronic devices and 5G communication systems, traditional wave-absorbing materials can no longer meet the current requirements. Thus, this research introduces a three-dimensional (3D) composite material consisting of PMMA@Mxene@Co₃O₄ microspheres, prepared through in situ self-assembly and hydrothermal growth. The strong electrical conductivity of Mxene, combined with the magnetic loss of Co₃O₄, ensures enhanced dielectric–magnetic synergy, leading to excellent EMW absorption. The study investigates the influence of varying Co₃O₄ content on the electromagnetic properties of the composite. Experimental results show that the optimal sample, with a thickness of 2.5 mm, achieves a minimum reflection loss (RL_min) of −52.88 dB at 6.88 GHz and an effective absorption bandwidth (EAB) of 5.28 GHz. This work highlights the potential of 3D PMMA@Mxene@Co₃O₄ composites as high-performance microwave absorbers, providing a promising solution to EMW pollution. The findings offer valuable insights into material design strategies, demonstrate a promising pathway for developing lightweight, high-performance EMW absorbing materials by optimizing impedance matching and utilizing advanced microstructure design techniques. Full article

The rational design of magnetic carbon composites, encompassing both their composition and microstructure, holds significant potential for achieving exceptional electromagnetic wave-absorbing materials (EAMs). In this study, FeCo@CM composites were efficiently fabricated through an advanced microwave plasma-assisted reduction chemical vapor deposition (MPARCVD) technique, offering high efficiency, low cost, and energy-saving benefits. By depositing graphitized carbon microspheres, the dielectric properties were significantly enhanced, resulting in improved electromagnetic wave absorption performances through optimized impedance matching and a synergistic effect with magnetic loss. A systematic investigation revealed that the laminar-stacked structure of FeCo exhibited superior properties compared to its spherical counterpart, supplying a higher number of exposed edges and enhanced catalytic activity, which facilitated the deposition of uniform and low-defect graphitized carbon microspheres. Consequently, the dielectric loss performance of the FeCo@CM composites was dramatically improved due to increased electrical conductivity and the formation of abundant heterogeneous interfaces. At a 40 wt% filling amount and a frequency of 7.84 GHz, the FeCo@CM composites achieved a minimum reflection loss value of −58.2 dB with an effective absorption bandwidth (f_E) of 5.13 GHz. This study presents an effective strategy for developing high-performance EAMs. Full article

The modified suspension polymerization technique has been used for the preparation of composite microparticles from the mixture of glycidyl methacrylate (GMA), styrene (S), and divinylbenzene (DVB) in the presence of hydrophobized Fe₃O₄ nanoparticles. The obtained polymer microspheres were characterized using different instrumental and physicochemical techniques, modified with a zero-order PAMAM dendrimer, and impregnated with palladium(II) acetate solutions to immobilize palladium(II) ions. The resulting materials were preliminarily examined as catalysts in the Suzuki reaction between 4-bromotoluene and phenylboronic acid. It was found that the addition of magnetite particles to the composition of monomers provided polymer microparticles with embedded magnetic nanoparticles. The composite microparticles obtained showed a complex, multi-hollow, or raspberry-like morphology. After their modification, they could serve as recyclable catalysts for reactions that include both 4-bromotoluene and several other aryl bromides. Full article

In this study, a renewable and reusable immobilized Microcystis aeruginosa microsphere loaded with magnetic Nano-Fe₃O₄ composite adsorbent material is designed to study the treatment of wastewater containing heavy metal Sb(III). Through static absorption experiments combined with various characterization methods, this article studies the absorption process and mechanism of Sb(III), and investigates the optimal preparation conditions and environmental influencing factors. The results show that the optimal preparation conditions for immobilized Microcystis aeruginosa microspheres loaded with magnetic Nano-Fe₃O₄ adsorbent materials are 50.0% mass fraction of Microcystis suspension, 1.5% mass fraction of Nano-Fe₃O₄, and 2.5% mass fraction of sodium alginate. When the pH of the solution is 4, the reaction temperature is 25 °C, and the adsorbent dosage is 8.5 g/L, the removal rate of Sb(III) is the highest, reaching 83.62% within 120 min. The adsorption process conforms to the pseudo-second order kinetic model and Langmuir adsorption isotherm model, mainly characterized by chemical adsorption and surface complexation. Therefore, the composite material has been proven to be an efficient Sb (III) adsorption material. Full article

The recycling of hazardous industrial waste into high-tech materials with desired properties is of considerable interest since it provides optimal alternatives for its final disposal. Coal fly ash, the major waste generated by coal-fired power plants, contains significant quantities of dispersed microspheres with a diameter smaller than 10 μm, which are anthropogenic atmospheric pollutants PM₁₀. Due to their composition and fine-grained powder morphology, they can be converted into sintered products. In this study, dispersed microspheres from class C fly ash were directly sintered without any additive to form high-strength glass-ceramics with magnetic properties. The optimum processing conditions were achieved at a temperature of 1200 °C, at which samples with a compressive strength of 100.6 MPa were obtained. Sintering reduces the quantity of the glass phase and promotes the formation of larnite, Fe-spinel, ye’elimite, and ternesite. Mössbauer measurements show that the relative concentration of the magnetic phase compared to the paramagnetic one rises almost in order. The sintered sample demonstrates a narrower distribution of the hyperfine magnetic field and a significantly lower value of the coercive field of 25 Oe, which allows proposing such materials as soft magnetic materials. The presented results demonstrate promising industrial applications of hazardous PM₁₀ to minimize solid waste pollution. Full article

The demand to synthesize economical detoxification adsorbents of organic pollutants has been a thriving solicitude for most environmental research aspirants. Here, we synthesized a titanium(III) oxide doped with spherical shaped meta-aminophenol formaldehyde magnetic microspheres (Ti₂O₃/mAPF MMSs) by the polymerization method of Ti₂O₃ nanoparticles with formaldehyde and m-aminophenol. SEM analysis confirmed the synthesized material as crystalline in nature and had ~400–450 nm sized particles. The physical characterization of the Ti₂O₃/mAPF MMSs were quantitatively revealed by FTIR spectrum and PXRD in elaboration. The carboxylate frequency and the characteristic apex of the titanium–oxygen bond was found in the FTIR spectrum for Ti₂O₃/mAPF derived from Ti₂O₃. The PXRD patterns proved that the synthesized magnetic microspheres contained Ti₂O₃ nanoparticles. The experimental methods of TGA and DTA confirmed the thermal stability and its composition of Ti₂O₃/mAPF MMSs. The kinetic adsorption study for methyl violet was confirmed as first-order kinetics. The present study was to investigate the dye desorption of methyl violet from simulated water samples by using a titanium(III) oxide doped with meta-aminophenol formaldehyde magnetic microspheres in an adsorption process. Full article

The rapid, single-stage, flame-spheroidisation process, as applied to varying Fe₃O₄:CaCO₃ powder combinations, provides for the rapid production of a mixture of dense and porous ferromagnetic microspheres with homogeneous composition, high levels of interconnected porosity and microsphere size control. This study describes the production of dense (35–80 µm) and highly porous (125–180 µm) Ca₂Fe₂O₅ ferromagnetic microspheres. Correlated backscattered electron imaging and mineral liberation analysis investigations provide insight into the microsphere formation mechanisms, as a function of Fe₃O₄/porogen mass ratios and gas flow settings. Optimised conditions for the processing of highly homogeneous Ca₂Fe₂O₅ porous and dense microspheres are identified. Induction heating studies of the materials produced delivered a controlled temperature increase to 43.7 °C, indicating that these flame-spheroidised Ca₂Fe₂O₅ ferromagnetic microspheres could be highly promising candidates for magnetic induced hyperthermia and other biomedical applications. Full article

The choice of carrier material is critical in the study of natural drug release preparations and glycosylated magnetic molecularly imprinted materials. The stiffness and softness of the carrier material affect the efficiency of drug release and the specificity of recognition. The dual adjustable aperture-ligand in molecularly imprinted polymers (MIPs) provides the possibility of individualized design for sustained release studies. In this study, a combination of paramagnetic Fe₃O₄ and carboxymethyl chitosan (CC) was used to enhance the imprinting effect and improve drug delivery. A combination of tetrahydrofuran and ethylene glycol was used as a binary porogen to prepare MIP-doped Fe₃O₄-grafted CC (SMCMIP). Salidroside serves as the template, methacrylic acid acts as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) serves as the crosslinker. Scanning and transmission electron microscopy were used to observe the micromorphology of the microspheres. The structural and morphological parameters of the SMCMIP composites were measured, including the surface area and pore diameter distribution. In an in vitro study, we found that the SMCMIP composite had a sustained release property of 50% after 6 h of release time in comparison to the control SMCNIP. The total amounts of SMCMIP released at 25 °C and 37 °C were 77% and 86%, respectively. In vitro results showed that the release of SMCMIP followed Fickian kinetics, meaning that the rate of release is dependent on the concentration gradient, with diffusion coefficients ranging from 3.07 × 10⁻² cm²/s to 5.66 × 10⁻³ cm²/s. The results of cytotoxicity experiments showed that the SMCMIP composite did not have any harmful effects on cell growth. The survival rates of intestinal epithelial cells (IPEC-J2) were found to be above 98%. By using the SMCMIP composite, drugs may be delivered in a sustained manner, potentially leading to improved therapeutic outcomes and reduced side effects. Full article

Magnetic nanoparticles (MNPs) were “green” synthesized from a FeCl₃/FeSO₄/CoCl₂ mixture using ethanolic extracts of Artemisia tilesii Ledeb ‘hairy’ roots. The effect of chemical composition and reducing power of ethanolic extracts on the morphology, size destribution and other features of obtained MNPs was evaluated. Depending on the extract properties, nanosized magnetic materials of spherical (8–11 nm), nanorod-like (15–24 nm) and cubic (14–24 nm) shapes were obtained via self-assembly. Microspherical MNPs composed of nanoclusters were observed when using extract of the control root line in the synthesis. Polyhedral magnetic nanoparticles with an average size of ~30 nm were formed using ‘hairy’ root ethanolic extract without any additive. Studied samples manifested excellent magnetic characteristics. Field-dependent magnetic measurements of most MNPs demonstrated a saturation magnetization of 42.0–72.9 emu/g with negligible coercivity (∼0.02–0.29 emu/g), indicating superparamagnetic behaviour only for solids with a magnetite phase. The synthesized MNPs were minimally aggregated and well-dispersed in aqueous medium, probably due to their stabilization by bioactive compounds in the initial extract. The nanoparticles were tested for magnetic solid-phase extraction of copper (Cu), cadmium (Cd) and arsenic (As) pollutants in aqueous solution, followed by ICP-OES analysis. The magnetic oxides, mainly magnetite, showed high adsorption capacity and effectively removed arsenic ions at pH 6.7. The maximum adsorption capacity was ~150 mg/g for As(III, V) on the selected MNPs with cubic morphology, which is higher than that of previously reported adsorbents. The best adsorption was achieved using Fe₃O₄-based nanomaterials with low crystallinity, non-spherical form and a large number of surface-localized organic molecules. The phytotoxicity of the obtained MNPs was estimated in vitro using lettuce and chicory as model plants. The obtained MNPs did not exhibit inhibitory activity. This work provides novel insights on the morphology of “green” synthesized magnetic nanoparticles that can be used for applications in adsorption technologies. Full article

A magnetite graphene oxide chitosan (MGOCS) composite microsphere was specifically prepared to efficiently adsorb As(III) from aqueous solutions. The characterization analysis of BET, XRD, VSM, TG, FTIR, XPS, and SEM-EDS was used to identify the characteristics and adsorption mechanism. Batch experiments were carried out to determine the effects of the operational parameters and to evaluate the adsorption kinetic and equilibrium isotherm. The results show that the MGOCS composite microsphere with a particle size of about 1.5 mm can be prepared by a straightforward method of dropping FeCl₂, graphene oxide (GO), and chitosan (CS) mixtures into NaOH solutions and then drying the mixed solutions at 45 °C. The produced MGOCS had a strong thermal stability with a mass loss of <30% below 620 °C. The specific surface area and saturation magnetization of the produced MGOCS was 66.85 m²/g and 24.35 emu/g, respectively. The As(III) adsorption capacity (Q_e) and removal efficiency (R_e) was only 0.25 mg/g and 5.81% for GOCS, respectively. After 0.08 mol of Fe₃O₄ modification, more than 53% of As(III) was efficiently removed by the formed MGOCS from aqueous solutions over a wide pH range of 5–10, and this was almost unaffected by temperature. The coexisting ion of PO₄³⁻ decreased Q_e from 3.81 mg/g to 1.32 mg/g, but Mn²⁺ increased Q_e from 3.50 mg/g to 4.19 mg/g. The As(III) adsorption fitted the best to the pseudo-second-order kinetic model, and the maximum Q_e was 20.72 mg/g as fitted by the Sips model. After four times regeneration, the R_e value of As(III) slightly decreased from 76.2% to 73.8%, and no secondary pollution of Fe happened. Chemisorption is the major mechanism for As(III) adsorption, and As(III) was adsorbed on the surface and interior of the MGOCS, while the adsorbed As(III) was partially oxidized to As(V) accompanied by the reduction of Fe(III) to Fe(II). The produced As(V) was further adsorbed through ligand exchange (by forming Fe–O–As complexes) and electrostatic attraction, enhancing the As(III) removal. As an easily prepared and environmental-friendly composite, MGOCS not only greatly adsorbs As(III) but also effectively removes Cr(VI) and As(V) (R_e > 60%) and other metals, showing a great advantage in the treatment of heavy metal-contaminated water. Full article

Copper matrix composites have a wide application as magnetic conductive materials, electromagnetic materials, electrical discharge machining materials, etc. Such materials are expected to have a good combination of excellent electrical conductivity and good mechanical strength. In this work, micro/nano hybrid reinforcements with Fe microspheres and reduced graphene oxide (rGO) nanosheets were developed for copper matrix composites. The rGO/Fe/Cu powders were firstly wet-mixed and then densified by the vacuum hot-pressing sintering to obtain the bulk compacts. Microstructure, electrical conductivity and mechanical properties of such compacts were investigated. Microstructural result of as-sintered compacts shows that the Fe microspheres could distribute in the matrix uniformly, and rGO nanosheets exhibit both agglomerated and dispersed states. The grain size of Cu matrix decreased with the increase of the rGO content. Hardness, compression and tensile 0.2% yield strength of the as-sintered compacts were improved evidently by the addition of the hybrid Fe/rGO, comparing with pure Cu and single Fe-added composites. However, a lower electrical conductivity appeared in the more rGO-added composites, but still reached more than 33.0% international annealing copper standard (IACS). These performance change could be sought in the spatially geometrical distribution and characteristics of such micro/nano Fe/rGO hybrid addition, and the relevant mechanisms were discussed. Full article

ZnFe₂O₄ microspheres were prepared by solvothermal method, and a novel ZnFe₂O₄@TiO₂ core-shell composite photocatalyst was prepared by ultrasonic (denoted as ZT-x) and mechanical stirring (denoted as ZTM-1.2). The morphology, structure, magnetic, and optoelectronic properties of the catalyst were investigated comprehensively, and the degradation performance of the catalyst was explored through the photocatalytic degradation of Rhodamine B (RhB) under UV light. The concentration of RhB was 10 mg/L, and the catalyst concentration was 0.3 g/L. ZT-1.2 showed the best photocatalytic degradation activity, and the degradation rate of RhB reached 97.3% within 60 min. The degradation ability of the catalyst was further evaluated by Methylene blue (MB), Methyl orange (MO), Phenol, and Ofloxacin (OFX). ZT-1.2 also exhibited excellent stability. The improved catalyst degradation performance was attributed to constructing a Z-type heterojunction. Moreover, the low-efficiency degradation of ZTM-1.2 was caused by catalyst agglomeration and low TiO₂ loading, confirming the superiority of the ultrasonic method and providing a new method for the preparation of magnetically recoverable TiO₂-based core-shell photocatalyst. Full article