CoFe2O4 Composites Research Articles

Efficient degradation of tetracycline by cobalt ferrite modified alkaline solution nanofibrous Ti3C2Tx MXene activated peroxymonosulfate system: Mechanism analysis and pathway

Magnetic CoFe2O4 nanoparticles have received considerable attention as an activator for peroxymonosulfate (PMS) in the degradation of tetracycline. However, it is still challenging to construct CoFe2O4 composites with good dispersion and highly exposed reactive sites. Herein, the KOH fiber-functionalized MXene matrix decorated by cobalt ferrite nanoparticles (denoted as CoFe2O4@Alk-MXene) was developed by electrostatic self-assembly method. The layered fibrotic structure effectively disperses and fixes cobalt ferrite nanoparticles, increasing the exposure of reactive sites. The as-prepared CoFe2O4@Alk-MXene material exhibited rapid removal of 100% tetracycline hydrochloride (TC-HCl) within 10 minutes by activating PMS, leveraging the excellent conductivity of alkalized MXene and the efficient activation of transition metal atoms. The experimental and theoretical analysis revealed that the electron transfer process of Ti2+/Ti4+, Co2+/Co3+ and Fe3+/Fe2+, as well as the free radical and non-free radical attack behaviors produced by the adsorption of PMS by the composite, are the primary mechanisms for achieving rapid removal of pollutants. A comprehensive degradation mechanism and potential pathways were proposed based on these findings. Overall, CoFe2O4@Alk-MXene/PMS emerges as a promising catalytic system for TC removal.

Magnetic interaction in Sr0.7La0.3Fe11.75Co0.25O19–CoFe2O4 composite system: observation, evidence, and influence

(100-x) Sr0.7La0.3Fe11.75Co0.25O19–(x) CoFe2O4 composites were synthesized by the one pot sol–gel auto-combustion method. The individual phase purity, morphology, and magnetic hysteresis loop of the composite magnet were analyzed by x-ray powder diffraction, field emission scanning electron microscopy and vibrating sample magnetometer, respectively. The apparent observation of the room temperature hysteresis loop indicates the existence of interfacial exchange interactions. Nevertheless, saturation magnetization (Ms ) follows the trend of Vegard’s law. The nature of magnetic interaction and its dependency on the amount of each phase were analyzed by employing the Thamm–Hesse plot. The critical size of the soft phase particle did not corroborate with the results of ΔM vs H plot. However, this synthesis method is found to be successful in obtaining single-step magnetization reversal in hard–soft composite magnets. The deviation from ideal non-interacting Stoner–Wohlfarth particles puts the single hard phase into the limelight. The (BH)max in the range of 1.07–0.98 MGOe has been obtained for the synthesized composite magnet.

Reduced graphene oxide supported CoFe2O4 composites with enhanced peroxymonosulfate activation for the removal of sulfamethoxazole: Collaboration of radical and non-radical pathways

In this work, an environmentally friendly reduced graphene oxidized supported cobalt ferrite (CFO/rGO) catalyst was constructed using a hydrothermal technique to heterogeneously activate peroxymonosulfate (PMS) and utilized for the degradation of sulfamethoxazole (SMX) antibiotic in aqueous solution. The results exhibited that the complete degradation of SMX was achieved in 25 min under optimal conditions ([SMX] = 8.0 mg/L, [CFO/rGO-30%] = 0.5 g/L, [PMS] = 5.0 mM, pH = 7.0) in the presence of CFO/rGO-30%/PMS with a rate constant of 0.3076 min˗1, which was roughly 6.08 times higher compared to the CoFe2O4/PMS system (0.0506 min˗1). The enhanced degradation of SMX in the CFO/rGO-30%/PMS system might be attributed to the large surface area of the CFO/rGO-30% (98.11 m2/g) catalyst compared to the pristine CoFe2O4 (24.31 m2/g), which increased the availability of active sites for PMS activation. Furthermore, the influence of pivotal reaction parameters and interfering anions on SMX mineralization was also scrutinized. The formation of free radicals (SO4•−, •OH, and 1O2) was established through quenching experiments and electron paramagnetic resonance analysis. The degradation mechanism of SMX was speculated based on the identification of degradation intermediates and X-ray photoelectron spectroscopy spectral analysis. Mechanistic investigations suggested that the transition of Co2+/Co3+ and Fe3+/Fe2+ pairs on the catalyst surface was responsible for the PMS activation, and the SMX degradation was accomplished through radical and non-radical pathways. Furthermore, CFO/rGO-30% exhibited high stability after four consecutive cycles and maintained catalytic activity. Finally, the developed CFO/rGO-30% catalyst exhibited promising potential for the purification of SMX polluted water.

CoFe content-controlled magnetic exchange coupling in CoFe2O4-CoFe composites prepared by a simple and single-step sonochemical reduction method

CoFe2O4 and CoFe2O4-CoFe composites (with varied amounts of CoFe) are synthesized under atmospheric conditions by a simple single-step sonochemical method that enables easy control of CoFe content in the CoFe2O4-CoFe composites. X-ray and electron diffraction and high-resolution electron microscopy revealed the formation of CoFe2O4-CoFe composites. High-resolution transmission electron microscopy of CoFe2O4-CoFe composites showed the formation of core–shell type nanostructures. Therefore enhanced exchange coupling between soft CoFe and hard CoFe2O4 magnetic phases is observed. This work shows that the magnetic properties (saturation magnetization, coercivity, and remanent magnetization) of CoFe2O4-CoFe composites can be tuned as per requirement by controlling the content of soft magnetic phase CoFe and thereby, the exchange coupling between the hard magnetic phase CoFe2O4 and the soft magnetic phase CoFe can be tuned.

Elevated degradation of di-n‑butyl phthalate by activating peroxymonosulfate over GO[sbnd]CoFe2O4 composites: Synergistic effects and mechanisms

Rational design of heterogeneous catalysts with high activity and stability is crucial in peroxymonosulfate (PMS)-based oxidation treatment of wastewater. Herein, the graphite oxide-cobalt ferrite (GO-CoFe2O4) composite was constructed, and its morphological, component and structural characteristics were thoroughly examined, respectively. GO-CoFe2O4 obviously boosted PMS catalytic performance on di-n‑butyl phthalate removal (DBP, RDBP = 90%, RTOC = 37%), which indicated by the first-order kinetic constant (kDBP = 0.060 min−1) being roughly 4 times than pure CoFe2O4 (kDBP = 0.015 min−1). The fabrication of GO-CoFe2O4 brought the favorable stability and repeatability up to six cycles. Moreover, the method of batch dosing catalyst was creatively proposed to improve the PMS utilization efficiency. The coupling of GO enhanced the dispersion of CoFe2O4 particles to obtain sufficient active sites, additionally, the plentiful C=O groups and free-flowing electrons on GO promoted GO-CoFe2O4 to coordinate a redox process during PMS activation. With the aid of theoretical calculations, GO-CoFe2O4 was revealed to exhibit a strong affinity toward PMS adsorption, where PMS spontaneously dissociated into sulfate radical (SO4•−), hydroxyl radical (•OH) and singlet oxygen (1O2), acting as the reactive oxygen species (ROSs). Electrons cycling between Co, Fe and O species ensured continuous ROSs generation and excellent catalytic performance.

Exchange coupling in SrFe12O19/CoFe2O4 composites: Effect of component proportions

(100-x)SrFe12O19/(x)CoFe2O4 composites were prepared by ball milling technique using different fractions of hexagonal and cubic ferrite powders as precursors, namely x = 10, 20, 30, 40 wt%. After grinding in a ball mill, as-prepared composites were annealed at 900 °C for 3 h. X-ray powder diffraction was carried out for structural analysis. Energy dispersive X-ray analysis allowed elemental analysis of the composites. Magnetic properties were studied at room temperature by magnetization versus applied external magnetic field, direct current demagnetization and isothermal remanence magnetization measurements. A relationship has been established between structural parameters (depending on the proportions of fractions of different crystallite size) and magnetic properties of the composites. Composite sample with 10 wt% CoFe2O4 reveals the highest energy product (BH)max = 10.9 kJ/m3, which is approximately 20 % higher than that of pristine SrFe12O19. The presence of the exchange coupling effect extracted from Henkel plots nicely explain the improved magnetic characteristics of composite.

Cobalt ferrite/MIL-101(Fe)/graphene oxide heterostructures coupled with peroxymonosulfate for triclosan degradation

Sulfate radical-based-advanced oxidation processes (SR-AOPs) have been recently considered for micropollutants degradation in water treatment. In the present study, cobalt ferrite (CoFe2O4), a metal-organic framework (MOFs) (MIL-101(Fe)), and graphene oxide (GO) were used to synthesize a novel heterostructure, CoFe2O4/MIL-101(Fe)/GO (C/M/G), through a hydrothermal method. The structural properties of C/M/G were determined by several characterization methods. The samples tested in the degradation of triclosan (TCS) with peroxymonosulfate (PMS), were able to activate it generating the highly active hydroxyl (HO•) and sulfate radicals (SO4•−). The effect and interaction of controlling parameters on TCS removal were investigated. Complete removal of TCS (500 μg/L) was achieved with pH 5, 0.04 g/L catalyst, and 8 μM PMS in only 30 min. The TCS removal declined obviously in the presence of radical scavengers and coexisting ions. The leachings of cobalt (Co) and iron (Fe) ions were lower than those of other CoFe2O4 composites coupled with PMS. Moreover, this process demonstrated high performance in the treatment of TCS in tap and well water. Accordingly, the C/M/G/PMS system seems to be a highly effective and environmentally compatible process for micropollutant degradation in water treatment.

Optical, ferroelectric, and magnetic properties of NiTiO3–CoFe2O4 composites prepared by one-step sol–gel method

Optical, ferroelectric, and magnetic properties of NiTiO3–CoFe2O4 composites prepared by one-step sol–gel method

Microstructure and magnetoresistance driven magnetocapacitance in ex-situ combustion derived BaTiO3-CoFe2O4 bulk magnetodielectric composites

Enhanced magnetodielectric properties including magnetocapacitance have been observed in the BaTiO3-CoFe2O4 composites due to the microstructural interactions between the dielectric and magnetic phases. Based on this concept, this research work explores the frequency and field dependent magnetocapacitance and magnetoresistance of 70 wt% BaTiO3 – 30 wt% CoFe2O4 composites. Ex-situ synthesis method is adopted to form a partial 0–3 microstructure and this composite is sintered at 900 °C and 1000 °C. Phases such as pseudo-cubic BaTiO3 and cubic CoFe2O4 have been observed in both composites. Secondary phase of barium hexaferrite is observed at 1000 °C. Based on FESEM, CoFe2O4 phase is found to be embedded in the BaTiO3 matrix at 900 °C, however interconnected CoFe2O4 along with partially shrunk BaTiO3 has been observed at 1000 °C. The permittivity of composite is found to be ∼ 317 and ∼ 451 at 900 °C and 1000 °C, respectively, and the Maxwell-Wagner polarization is tuned by the microstructure. The effect of space charge is found to be relatively larger at 1000 °C. Magnetic nature is altered due to the connectivity of ferrite phases. Magnetocapacitance values are mostly analogues to the magnetoresistance behavior in both composites. The percentage of magnetocapacitance is found to be increased nearly 5 times due to the microstructural variations. Field and frequency-dependent magnetocapacitance responses along with Cole-Cole plots of composite confirmed the role of microstructural interactions and magnetoresistance.

Influence of micro-topological textures of BaTiO3–CoFe2O4 composites on the nonlinear pyrocoupled dynamic response of blast loaded magneto-electro-elastic plates in thermal environment

Influence of micro-topological textures of BaTiO3–CoFe2O4 composites on the nonlinear pyrocoupled dynamic response of blast loaded magneto-electro-elastic plates in thermal environment

Fine-grained magnetoelectric Sr0.5Ba0.5Nb2O6–CoFe2O4 composites synthesized by a straightforward one-pot method

Fine-grained magnetoelectric Sr0.5Ba0.5Nb2O6–CoFe2O4 composites synthesized by a straightforward one-pot method

Fine-grained magnetoelectric Sr0.5Ba0.5Nb2O6–CoFe2O4 composites synthesized by a straightforward one-pot method

Magnetoelectric (Sr0.5Ba0.5Nb2O6)1−x−(CoFe2O4)x (x = 0.2–0.6) composites were prepared by a one-pot soft-chemistry synthesis using PEG400. Calcining at 700 °C resulted in nanocrystalline composite powders (dcryst. = 24–30 nm) which were sintered between 1050 and 1200 °C to ceramic bodies with relative densities up to 98%. SEM investigations confirm the formation of composite ceramics with a 0–3 connectivity and variable grain sizes from 0.2 to 3.6 μm for sintering up to 1150 °C, while sintering at 1200 °C leads both to a change in the microstructure and a considerable grain growth. Magnetic measurements at 300 K reveal ferrimagnetic behaviour with saturation magnetization values smaller than bulk CoFe2O4 and coercivities between 790 and 160 Oe. Temperature-dependent impedance spectroscopy showed that the relative permittivities decrease both with rising frequency and CoFe2O4 fraction. The frequency dependence of the impedance can be well described using a single RC circuit. Magnetoelectric measurements show the presence of pronounced field hystereses. The maximum magnetoelectric coefficient (αME) depends both on the CoFe2O4 fraction (x) and sintering temperature. The composite with x = 0.3 exhibits the largest αME value of 37 μV Oe−1 cm−1 (@ 900 Hz). With rising frequency of the AC driving field αME increases up to 300–400 Hz and is nearly constant until 1 kHz.

Fabrication of graphitic carbon nitride functionalized P–CoFe2O4 for the removal of tetracycline under visible light: Optimization, degradation pathways and mechanism evaluation

In this study, nano-sized CoFe2O4 composites were prepared through co-precipitation process. Then the phosphorus-doped strong magnetic graphitic carbon nitride hybrids composites (P–CoFe2O4@GCN) was stemmed from the CoFe2O4 composites via the thermal polymerization method. The TEM results show that the CoFe2O4 nanoparticles have been successfully embedded into the graphitic carbon nitride (GCN). The BET specific surface area of P–CoFe2O4@GCN-1 could reach 36.91 m2/g, which was 5.38 times higher than that of GCN. Thus, it provided sufficient reaction active sites to enhance the photocatalytic activity for tetracycline (TC) decomposition. The results from the photocatalytic experiments showed that the degradation efficiency of TC by P–CoFe2O4@GCN-1 could reach 96.2% within 60 min, which is 3.19 times higher than that of GCN. The h+, O2•- and •OH radicals detected by the electron spin resonance (ESR) were responsible for the TC decomposition in the photocatalytic reaction system. Persulfate (PS) can further activate the hybrid mixture system, and the fitting model predicted by the response surface methodology (RSM) indicated that the maximum tetracycline removal could reach 99.6% within 30 min. In addition, the degradation intermediates of TC were detected by HPLC-MS and the photodegradation mechanism was discussed.

Dysprosium doped CoFe2O4 with enhanced magnetic property and photodegradation activity of methyl orange

Visible-light-initiated degradation of dyes has received much attention because of environmental friendliness and low cost. Here, dysprosium (Dy) doped CoFe2O4 composites with enhanced photocatalytic activity that are capable of fast magnetically recovering have been successfully synthesized by partially substitution Fe3+ in the crystalline lattice with Dy3+. The as-prepared CoFe1.97Dy0.03O4 nanoparticles possess a significantly improved magnetic property, which facilitates the separation of solid–liquid mixtures. Meanwhile, an obviously enhanced photocatalytic activity toward methyl orange degradation has been observed. The introduction of Dy in the lattice of CoFe2O4 can not only improve the light adsorption of the photocatalysts but also increase the carrier density, leading to enhanced performance for photodegradation of methyl orange.

Synthesis and characterization of BaFe12O19-CoFe2O4 ferrite composite for high-frequency antenna application

Recently, ferrite composite ceramics have received much attention for high-frequency device applications as the composite has both dielectric and magnetic properties, good chemical stability, and high electrical resistivity. M-type hexagonal ferrite BaFe12O19 (BaM) and cubic spinel ferrite CoFe2O4 (CoF) composites; (BaM)1−x(CoF)x (x = 0.0, 0.25, 0.50, 0.75, and 1.0) were successfully synthesized by co-precipitation method. X-ray diffraction (XRD) analysis confirmed the formation of pure-phase BaM ferrite at 800 °C and CoF ferrite at 600 °C, respectively. The XRD analysis of composite ferrite showed the presence of both BaM and CoF ferrite phases in the composite. The composites were sintered at 1100 °C/4 h. The composite with x = 0.25 composition showed the most compact microstructure structure and higher bulk density compared to other composites. The composite (with x = 0.25) also showed the highest permittivity (~ 15), permeability (~ 13), and antenna miniaturization factor (~ 14) at 500 MHz due to mainly better densification. The permeability of composite was almost stable up to about 500 MHz. The coercivity was lowest in the composite with x = 0.25 composition indicating a change of hard magnetic behavior of BaM ferrite into a soft magnetic character after composite formation, which may be due to the formation of enlarged grain of BaM in the composite.

Graphene nanosheets wrapped CoFe2O4 nanosphere composites as high performance anode for advanced lithium storage

High electrochemical performance anode materials played a key role in the lithium-ion batteries employed in electric vehicles. In this work, graphene nanosheets wrapped CoFe2O4 (G/CFOs) composites were successfully prepared by a facile one-pot method with hydrothermal reaction. The scanning electron microscopy showed that the CoFe2O4 nanospheres were uniformly wrapped by the graphene nanosheets. The as-prepared G/CFOs composites displayed excellent electrochemical performance with high specific capacity of 1496 mAh g−1 at the current density of 0.2 A g−1 and superior rate performance of 1026 mAh g−1 at high rate of 6 A g−1. Besides, the G/CFOs composites exhibited excellent cycle stability of 796 mAh g−1 at 6 A g−1 after 300 cycles. It is believed that our work may provide a new method to develop the anode materials for the lithium-ion batteries.

Magnetic finite size effects, coercive field and irreversibility in sintered (1-x)BaTiO3–xCoFe2O4 nano-composites

We present detailed magnetic properties of (1-x)BaTiO3–xCoFe2O4 (x = 1, 0.5, 0.4, 0.3, 0.2, 0.1, 0.75, 0.05, 0.025) nanocomposites, synthesized through multiple-step chemical synthesis technique. Stepwise synthesis and structural optimization of composites include oxalate route synthesis of BaTiO3 with specifically chosen tetragonality followed by mixing in citric acid solution, and a final addition of the precursor for CoFe2O4. Heat treatment temperature were appropriately chosen to obtain composites with distinct spinel and tetragonal perovskite phases. Peak broadening has been observed in composites being a consequence of presence of strain. Main goal of the present work is to investigate magnetic response as a function of temperature for various compositions and to compare them with the magnetic properties of CoFe2O4 nanoparticles. BaTiO3 acts as a barrier for the growth of the CoFe2O4 due to the phase separation between these constituent phases in the composites. The nanoscopic features are consistently observed in the magnetic properties of the composites. These features include increase in coercivity, stronger temperature dependence of coercivity and magnetic irreversibility. CoFe2O4 and BaTiO3 composites exhibit strong temperature dependence with a more than an order of magnitude increase in coercivity at low temperatures.

Microstructural, magnetic and electric properties of sol-gel synthesized Na0.5Bi0.5TiO3–CoFe2O4 composites

In this work, we presented investigations on the microstructural, magnetic, dielectric and conductive properties of (1-x)Na0.5Bi0.5TiO3-xCoFe2O4 (NBT-CFO) composite ceramics (x = 0.1, 0.2, 0.3 and 0.5). The composites were synthesized using the in-situ sol-gel method, and the resulting CFO/NBT embedded structure was observed in the 0.9NBT–0.1CFO sample. Rietveld refinement confirmed that the embedded structure had remarkable effects on the c/a ratios of NBT-CFO composites. Increasing normalization saturation magnetizations were observed with increasing of CFO contents, thus revealing the influence of phase interfaces on magnetism. Dielectric relaxation anomalies were observed on both temperature dependent permittivity and loss spectra. Two sets of anomalies in these spectra were caused by space charges on the phase interfaces of embedded CFO grains and the NBT matrix. The conduction behavior of ceramics with and without the embedded structure obeyed the double power law and Jonscher's fraction power law, respectively, which inferred a transformation from the AC to the DC conduction mechanism with the disappearance of the embedded structure.

Influence of interphase on the multi-physics coupled frequency of three-phase smart magneto-electro-elastic composite plates

The present article researches the influence of piezoelectric interphase thickness on the coupled frequency response of three-phase smart magneto-electro-elastic (TPS-MEE) plates with the aid of Reddy’s third-order shear deformation theory (RTSDT). A three-phase smart composite constituted of CoFe2O4 piezomagnetic matrix embedded with carbon fibers in the piezoelectric shell is considered for evaluation. The coupling characteristics of the smart carbon/PZT-5A (PZT-7A)/CoFe2O4 composites significantly changes with the interphase thickness of piezoelectric interphase. Thereby the stiffness and the natural frequency of the structure composed of these three-phase MEE materials drastically changes. A finite element (FE) formulation has been derived incorporating Hamilton’s principle. The equations of motion are obtained through condensation technique. The results reveal a significant effect of interphase thickness on the natural frequency of the three-phase smart magneto-electro-elastic plate. Further, a special attention has been paid on evaluating the influence of carbon fiber/piezoelectric volume fraction on the free vibration behaviour of TPS-MEE plate. Also, a parametric study has been performed to investigate the effect of boundary conditions, aspect ratio and length-to-width ratio.

Enhanced magneto-electric coupling and energy storage analysis in (BiFeO3–BaTiO3)/CoFe2O4 composites

Enhanced magneto-electric coupling and energy storage density analysis of solid-state route derived (BiFeO3–BaTiO3)/CoFe2O4 composites were investigated for memory application under the variation of the magnetic phase of CoFe2O4. The powder X-ray diffraction data, SEM–EDX, Raman spectroscopy, and FTIR measurements were carried out to investigate the crystalline structure, composite formation and phase purity of all the samples. Magnetic measurements showed very high magnetization values obtained from 0.063 emu/g for 0.7BF–0.3BT to 18.14 emu/g for (0.7BF–0.3BT)/30CF composite near room temperature. The weak but countable maximum ferroelectric polarization (Pmax) was achieved due to the change in the area of the loops with the variation of frequencies from 50 to 200 Hz. The highest value of energy storage density (Ju) and efficiency (η) for (BF–BT)/30CF (Ju = 37.08 mJ/cm3 and η = 89.40%) composite was achieved. The dielectric anomaly near the magnetic transition temperature (Tc ~ 425 °C) and the variation in the maximum polarization values from 4.63 to 6.6 µC/cm2 with respect to the applied magnetic field confirmed the strong evidence of magneto-electric coupling in (BF–BT)/CF composite samples. The highest values of magneto-electric coefficients (α) were achieved 9.039 mV/cm Oe at 600 Oe, 9.039 mV/cm Oe at 1100 Oe and 22.59 mV/cm Oe at 1600 Oe for (BF–BT)/10CF, (BF–BT)/20CF and (BF–BT)/30CF composites respectively.