共查询到20条相似文献,搜索用时 78 毫秒
1.
The optical properties of multi-functionalized cobalt ferrite (CoFe 2O 4), cobalt zinc ferrite (Co 0.5Zn 0.5Fe 2O 4), and zinc ferrite (ZnFe 2O 4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications. 相似文献
2.
Spinel cobalt ferrites (CoFe 2O 4) with varying levels of substoichiometry were prepared via sol-gel synthesis with different combinations of citric acid, dextrose and PVP (polyvinylpyrrolidone). The gels, prepared from the metal nitrates, were dried at 110?°C, further treated at 850?°C and finally subjected to thorough structural and magnetic characterization in order to correlate the composition of the gel to the structural and magnetic properties displayed by the ferrites. The materials synthesized in the present work have shown to be rather iron-depleted, reaching over 50% deficiency of the metal, which leaves the spinel lattice and forms Fe 2O 3 instead. The fuel/oxidant ratio and the thermal behavior of the xerogels exert a direct influence on the compositional variation of the prepared spinels, which could in turn be correlated to the magnetic properties displayed by the particles. A maximum in coercivity of 2154.4?Oe was achieved without the application of any additive to the nitrate precursors. On the other hand, the magnetic remanence displayed by the ferrites shows a linear relationship to the iron content in their chemical formula. The results open up the possibility of fine-tuning the structural and magnetic properties displayed by the spinel product via careful control of the composition of the reaction medium. 相似文献
3.
Fabrication of magnetoelectric (ME) polymer composite films by embedding ferromagnetic cobalt ferrite (CoFe 2O 4) nanofibers into electroactive poly(vinylidene fluoride–hexafluoropropylene) (P(VDF-HFP)) matrix is reported. Single-phase CoFe 2O 4 nanofibers made of cubic spinel nano crystallites are synthesized by using electro-spinning method, whereas the solution-casting technique is adapted to prepare flexible polymer composite films. The influence of CoFe 2O 4 nanofiber on structural, functional, magnetic, ferroelectric, and magnetoresistance properties of the composite films is investigated. The cross-coupling between ferroelectric and ferromagnetic orderings is ensured, by the variations of ferroelectric response at different magnetic fields. These magnetoelectric films are found to exhibit a negative tunneling magnetoresistance (TMR) effect with maximum TMR% of 28 for the film with 20 wt% of CoFe 2O 4 loading. The dielectric constant and electrical energy storage density of the films are increased with the addition of CoFe 2O 4 nanofiber. The ME films exhibiting TMR and high energy density can be the potential candidates for multifunctional device applications such as memory and spintronics devices, magnetic sensor, and bio-sensor. 相似文献
4.
The aim of this study is to synthesize and assess the potential applications of rare earth doped cobalt ferrite nanoparticles in cancer treatment through hyperthermia.The synthesis of CoFe 2−xRE xO 4 (where RE=Yb, Dy, Gd and x=0.01–0.3) through the co-precipitation method is presented. The composition and properties of the nanoparticles where investigated and evaluated in correlation with their heat generating capability. The XRD and EDX analysis indicated phase separation for high rare earth content with the appearance of Gd 2O 3 and Dy 2O 3 secondary phases, which leads to unwanted changes in the nanoparticles' magnetic properties and consequently of the specific absorption rate. All the nanoparticles present functional group belonging to the surfactant as determined by FT-IR and Raman. Magnetic and specific adsorption rate measurement suggest increases in saturation magnetization and SAR value in doped ferrites, compared to CoFe 2O 4 with as much as 26% and 15% for Dy doped and Gd doped samples respectively. 相似文献
5.
Rare-earth (RE) substituted cobalt ferrite CoFe 1.9RE 0.1O 4 (RE=Pr 3+, Sm 3+, Tb 3+, Ho 3+) nanoparticles are synthesized by a facile hydrothermal method without any template and surfactant. The effects of RE 3+ substitution on structural, magnetic and adsorption properties of cobalt ferrite nanoparticles are investigated. Structure, morphology, particle size, chemical composition and magnetic properties of the ferrite nanoparticles are studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), high solution transmission electron microscopy (HRTEM), energy-dispersive spectrometer (EDS), Fourier transform spectroscopy (FTIR), Raman spectra and vibrating sample magnetometry (VSM). The results indicate that the as-synthesized samples have the pure spinel phase, uniform crystallite size and narrow particle size distribution. Meanwhile, the RE 3+ substitution leads to the decrease in the particle size, magnetization and coercivity of the CoFe 2O 4 ferrite. Notably, it demonstrates that the RE 3+ doping can apparently enhance the adsorption capacity for Congo red (CR) onto ferrite nanoparticles. Adsorption equilibrium studies show that adsorption of CR follows the Langmuir model. The monolayer adsorption capacities of CoFe 1.9Sm 0.1O 4 and CoFe 1.9Ho 0.1O 4 are 178.6 and 158.0 mg/g, respectively. The adsorption kinetics can be described by the pseudo-second-order model. 相似文献
6.
Three different spinel metal oxide catalytic systems including NiFe 2O 4, CuFe 2O 4 and CoFe 2O 4 were synthesized using co-precipitation technique and their catalytic activities were compared to each other in α-arylation of oxindole derivatives under the optimized reaction conditions. Both nickel ferrite and copper ferrite magnetic nanoparticles show approximately the same behavior in these reactions but cobalt ferrite ones indicate slightly different properties and were not as good as the other two catalysts. These superparamagnetic catalysts allowed that α-arylation of different types of oxindoles will occur in high yields under mild conditions and at very short times. 相似文献
7.
In this article, we have reported an effective, rapid as well as economical Er 3+ substituted Ni 0.4Co 0.6Fe 2O 4 ferrite nanoparticles synthesized via surfactant-assisted co-precipitation route. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), dielectric properties, current-voltage (I–V) measurements, and vibrating sample magnetometry (VSM). XRD and FTIR confirmed the face-centered (FCC) spinel structure of all compositions of the synthesized spinel ferrite nanoparticles. The deviations in the lattice constant granted with the variation in size of the guest (Er 3+) and host (Fe 3+) cations. These ferrites were also subjected for electrical, magnetic and dielectric investigations. I–V measurements showed that resistivity values decreased from 6.20 × 10 7 Ω cm to 0.03 × 10 7 Ω cm with the increased Er 3+ contents. Saturation magnetization increased from 35.99 to 39.95 emu/g. This high value of saturation magnetization suggested the possible utilization of such ferrites for practical applications such as microwave and recording devices fabrication. Interestingly, the magnetic and dielectric properties of nickel-cobalt ferrite nanoparticles showed ample improvement upon Er 3+ substitution. The results clearly indicate the potential of Er +3 substituted spinel ferrite particles in various advanced technological devices fabrication. 相似文献
8.
The influence of the CoFe 2O 4 nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe 2O 4/(100−x)SiO 2 nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe 2O 4 nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 °C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe 2O 4 nanoparticles have spherical shapes and size in the 6–35 nm range. The Mössbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe 2O 4 nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix. 相似文献
9.
In this study, pure cobalt ferrite (CoFe 2O 4) nanoparticles and europium doped CoFe 2O 4 (CoFe 2−xEu xO 4; x = 0.1, 0.2, 0.3) nanoparticles were synthesized by the precipitation and hydrothermal approach. The impact of replacing trivalent iron (Fe 3+) ions by trivalent rare earth europium (RE-Eu 3+) ions on the microstructure, optical and magnetic properties of the produced CoFe 2O 4 nanoparticles was studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra exposed the consistency of a single cubic phase with the evidence of Eu 2O 3 phases for x ≥ 0.2. FTIR transmittance spectra showed that, the all investigated samples have three characteristic metal-oxygen bond vibrations corresponding to octahedral B-site (υ 1 and υ 2) and tetrahedral A-site (υ 3) around 415 cm −1, 470 cm −1 and 600 cm −1 respectively. XRD and energy dispersive X-ray spectroscopy studies affirmed the integration of RE-Eu 3+ ions within CoFe 2O 4 host lattice and decrease of average crystals size from 13.7 nm to 4.7 nm. Transmission electron microscopy (TEM) analysis showed the crucial role played by RE-Eu 3+ added to CoFe 2O 4 in reducing the particle size below 5 nm in agreement with XRD analysis. High resolution-TEM (HR-TEM) analysis showed that the as-synthesized spinel ferrite, i.e., CoFe 2−xEu xO 4, nanoparticles are single-crystalline with no visible defects. In addition, the HR-TEM results showed that pure and doped CoFe 2O 4 have well-resolved lattice fringes and their interplanar spacings matches that obtained by XRD analysis. Magnetic properties investigated by the vibrating sample magnetometer technique illustrated transformation of magnetic state from ferromagnetic to superparamagnetic at 300 K resulting in introducing RE-Eu 3+ in CoFe 2O 4 lattice. At low temperature (~5 K) the magnetic order was ferromagnetic for both pure and doped CoFe 2O 4 samples. Substitution of Fe 3+ ions in CoFe 2O 4 nanoparticles with RE-Eu 3+ ions optimizes the sample nanocrystals size, cation distribution and magnetic properties for many applications. 相似文献
10.
The study demonstrates the performance of heating efficiency in single-phase and binary phase spinel ferrite nanosystems. Ferrimagnetic cobalt ferrite (CoFe 2O 4) (CFO) and superparamagnetic copper ferrite/copper oxide (CuFe 2O 4/CuO) (CuF) nanosystems of different particle sizes were synthesized through a microwave-assisted coprecipitation method. The heating behavior was observed in range of both field amplitudes (8-24 kA/m at 516 kHz) and frequencies (325-973 kHz at 12 kA/m). The heating efficiency was analyzed and compared by means of particle size, magnetization, effective anisotropy constant, and Néel relaxation mechanism. Indeed, the heating rate was maximized in larger ferrite particles with low effective anisotropy constant. Moreover, though the magnetization and effective anisotropy constant of single-phase CoFe 2O 4 nanoparticles were higher, the binary phase CuFe 2O 4/CuO nanosystems of similar crystallite size (28 nm) exhibited superior heating efficiency (4.21°C/s). For a field amplitude and frequency of 24 kA/m and 516 kHz, the heating rate of CuF and CFO ferrites with different crystallite sizes decreased in the order of 4.21 > 2.14 > 0.58 > 0.52°C/s for 29 nm > 25 nm > 12 nm > 15 nm, respectively. The results emphasize that binary phase ferrite nanoparticles are better thermoseeds than the single-phase ferrites for the magnetic hyperthermia application. 相似文献
11.
Researchers have taken a prodigious consideration in characterizing and synthesizing zinc substituted cobalt ferrite nanoparticles because of their substantial applications across diverse technological and industrial fields. Zinc substituted cobalt ferrite nanoparticles are a class of lenient magnetic nanomaterials, which have potentially high magnetic, optical, electrical, and dielectric properties. These properties include a high value of permeability, low power losses, permittivity, saturation magnetization, coercivity, resistivity, and other beneficial properties that make them promise candidates for applications in various fields. These ferrites are also used in biomedical areas such as MRI and cancer treatments. In electronic fields, zinc substituted cobalt ferrite nanoparticles are used to make transducers, transformers, biosensors, and sensors. Apart from these advantages, they are found in our everyday electronic and electrical appliances like LED bulb, refrigerator, mobile charger, TV, microwave oven, juicer, washing machine, mixer, iron, printer, laptop, mobile, desktop, etc. Hence, the current review reports some properties of these spinel ferrites and emphasizes the different synthesis techniques that can be used to prepare them. Afterward, the impact of dopant on the materials' properties, the characterization techniques, and the momentous application in the present era have been well discussed. 相似文献
12.
Cobalt ferrite magnetic nanoparticles were synthesized and developed by a modified Pechini method using iron nitrate, cobalt nitrate, ethylene glycol (EG), and sucrose with different volumes of lemon juice (10, 20, 30, 40, 50, 60, and 70 ml) as the source of chelating agent as well as nonmagnetic elements such as Ca and Mg ions. The XRD patterns confirmed that all samples synthesized by different contents of extracted lemon juice had a cubic crystal structure with single-phase spinel. Scanning electron microscopy revealed that cobalt ferrite nanoparticles had a semi-spherical morphology. Also, the vibrating sample magnetometer indicated that the saturation magnetization of CoFe 2O 4 nanoparticles prepared with different values of extracted lemon juice increased from 18.6 emu/g for 10 ml extracted lemon juice to 75.7 emu/g for 50 ml extracted lemon juice, after which the saturation magnetization diminished. Afterwards, the CoFe 2O 4 nanoparticles were coated with polyethylene glycol (PEG) and doxorubicin (DOX) drugs, whereby drug delivery was detected at different pH levels. The CoFe 2O 4-PEG-DOX nanocomposite could release doxorubicin by more than 42% at pH = 5.4 in 75 h. 相似文献
13.
Due to their strong magnetic dissipation and low cost, ferrites were one of the first generations of microwave absorbers. However, ferrites also have some drawbacks, such as a low natural resonance frequency ( fr), a lack of dielectric loss, and high density. In order to overcome these drawbacks and improve the microwave dissipation features of ferrites, we successfully prepared CoFe 2O 4 samples with flower-like and crochet ball-like morphologies (named as M1 and M2 samples, respectively). Structural and optical properties were studied by XRD, FTIR, and UV–Vis light absorption. The microwave performance of CoFe 2O 4 was significantly improved with the reflection loss (RL) of M2 of ?40 dB. Furthermore, M1 and M2 samples achieved an ultra-wide effective absorption bandwidth (EAB) of 13 and 12.5 GHz, respectively. It is worth noticing that the EAB of M1 was one of the largest EABs for CoFe 2O 4 that has been reported so far. The excellent microwave dissipation of M1 and M2 samples in the 2–18 GHz frequency range was due to the enhancement of ferrite fr to the high-frequency range and the introduction of dielectric loss to achieve impedance matching. The flower-like and crochet ball-like morphologies with many pores of M1 and M2 also resolved the high-density issue of CoFe 2O 4. With the relatively good values of RL and EAB combined with low filler loading, thin thickness, and low density, M1 and M2 samples could be expected to be promising microwave absorbers for practical applications. 相似文献
14.
The structural, morphological and magnetic properties of MFe 2O 4 (M = Co, Ni, Zn, Cu, Mn) type ferrites produced by thermal decomposition at 700 and 1000 °C were studied. The thermal analysis revealed that the ferrites are formed at up to 350 °C. After heat treatment at 1000 °C, single-phase ferrite nanoparticles were attained, while after heat treatment at 700 °C, the CoFe 2O 4 was accompanied by Co 3O 4 and the MnFe 2O 4 by α-Fe 2O 3. The particle size of the spherical shape in the nanoscale region was confirmed by transmission electron microscopy. The specific surface area below 0.5 m 2/g suggested a non–porous structure with particle agglomeration that limits nitrogen absorption. By heat treatment at 1000 °C, superparamagnetic CoFe 2O 4 nanoparticles and paramagnetic NiFe 2O 4, MnFe 2O 4, CuFe 2O 4 and ZnFe 2O 4 nanoparticles were obtained. 相似文献
15.
Owing to its unique magnetic, dielectric, electrical and catalytic properties, ferrite nanostructure materials gain vital importance in high frequency, memory, imaging, sensor, energy and biomedical applications. Doping is one of the strategies to manipulate the spinel ferrite structure, which could alter the physico-chemical properties. In the present work, Co 1-xZn xFe 2O 4 ( = 0, 0.1, 0.2, 0.3, and 0.4 wt%) nanoparticles were prepared by sol-gel auto-combustion method and its structural, morphological, vibrational, optical, electrical and magnetic properties were studied. The structural analysis affirms the single-phase cubic spinel structure of CoFe 2O 4. The crystallite size, lattice constant, unit cell, X-ray density, dislocation density and hopping length were significantly varied with Zn doping. The Fe–O stretching vibration was estimated by FTIR and Raman spectra. TEM micrographs show the agglomerated particles and it size varies between 10 and 56 nm. The Hall effect measurement shows the switching of charge carriers from n to p type. The dielectric constant (ε′) varies from 0.2 × 10 3 to 1.2 × 10 3 for different Zn doping. The VSM analysis shows relatively high saturation magnetization of 57 and 69 emu/g for ZC 0.1 and ZC 0.2 samples, respectively than that of undoped sample. All the prepared samples exhibit soft magnetic behaviour. Hence, it can be realized that the lower concentration of Zn ion doping significantly alters the magnetic properties of CoFe 2O 4 through variation in the cationic distribution and exchange interaction between the Co and Fe sites of the inverse spinel structure of CoFe 2O 4. 相似文献
16.
In recent years, spinel ferrites with chemical formula MFe 2O 4, have attracted much attention due to their impressive photocatalytic and electrocatalytic performances, which are significantly influenced by their spinel structures. However, it is still a big challenge to distinguish or predict spinel structures for spinel ferrites. As an attempt to address this issue, this paper presents a first-principles study of the thermodynamics and electronic structures for six spinel ferrites with different spinel structures. The configurational free energy of these spinel ferrites at different inversion degrees is calculated to determine the equilibrium inversion degree for each spinel, which successfully predicts the spinel structure type of these spinel ferrites. The partial density of states is obtained for six spinel ferrites assuming they are normal or inverse spinels. The electronic states close to the Fermi energy of each spinel ferrite are carefully examined, showing that normal spinels have weak interactions between M and Fe states, while strong interactions exist in mixed or inverse spinels. Our results offer an insightful understanding of different spinel structures, and provide a reliable approach to determine the spinel structure of spinel ferrites. 相似文献
17.
Cobalt ferrite (CoFe 2O 4) particles were synthesized by sol–gel method using metal nitrates, citric acid (CA) and polyvinyl alcohol (PVA). X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), thermogravimetry/differential scanning calorimetry analysis and vibrating sample magnetometer were used to study the structural, thermal and magnetic properties of the CoFe 2O 4 powder. XRD results indicate that the resultant particles have crystalline, pure single phase spinel structure. From HR-SEM images, a systematic decrease in particle size is observed with an increase in PVA concentration, along with addition of CA. CA at various concentrations of PVA significantly enhance the magnetic properties of the materials. 相似文献
18.
In the present work, we reported a facile synthesis of cobalt ferrite (CoFe 2O 4) nanoparticles in the presence of L-cysteine (Lys). The morphology and size of samples were characterized by SEM and TEM. The successful coating of Lys on the surface of CoFe 2O 4 was confirmed by XRD, XPS and TGA. The investigation of magnetic properties showed that both bare CoFe 2O 4 and Lys-coated CoFe 2O 4 nanoparticles exhibited room-temperature superparamagnetic behavior. The results of MTT experiments revealed insignificant cytotoxicity of Lys-coated CoFe 2O 4 nanoparticles even after 24?h incubation. More importantly, Lys-coated CoFe 2O 4 nanoparticles displayed an excellent drug loading capacity and a pH-sensitive drug release behavior. In summary, the prepared Lys-coated CoFe 2O 4 nanoparticles demonstrated a promising application potential in controlled drug delivery. 相似文献
19.
Nanocomposites of magnetic nanoparticles and polymer matrices combine the properties of their components, and as such are good examples of functional nanomaterials with excellent application potential. Against this background, experimental and theoretical studies of such composites are of great interest. In this study we aim to provide insight into the static and dynamic magnetic response, as well as the dielectric response, of magnetic nanocomposites subjected to external magnetic and electric fields. We directly compare the behavior of polyurethane films doped with superparamagnetic Fe 3O 4, and blocked ferromagnetic CoFe 2O 4 nanoparticles. While a reversible, Langevin magnetization curve is observed for Fe 3O 4@PU films, hysteretic magnetic behavior is found in case of CoFe 2O 4@PU films. The hysteresis observed for CoFe 2O 4 nanoparticles can be explained by interactions at the interface between particles and polymer matrix in conjunction with its ferromagnetic nature. The results of dielectric spectroscopy experiments revealed different effects of Fe 3O 4 and CoFe 2O 4 nanoparticles on polymer dynamics. 相似文献
20.
It would be helpful to achieve appropriate synthetic routes to attain larger-scale production at industrial levels of nanocomposites at low costs. In the present work, diphasic composites with core–shell nanostructures formed by La2Fe2O6/CoFe2O4 are investigated. The core–shell structure is fabricated via different preparation methods. The advantages and the demerits of the synthesis techniques are discussed. The presence of both the spinel CoFe2O4 nano ferrite and orthorhombic La2Fe2O6 perovskite phases is revealed by X-ray diffraction. XPS spectroscopy is utilized to investigate the chemical composition of the prepared samples. The hysteresis loops of the prepared samples exhibit a smooth loop that is resulted from the existence of two homogeneous magnetic phases. For the first time, it has been found that the preparation conditions have the advantage of reducing the switching field distribution value for the core–shell nanoparticles. Exchange coupled core–shell nanoparticles present a high potential to regulate the magnetic properties for numerous applications such as heavy metal removal and/or data storage devices. The maximum adsorption capacity (qm) of Cr III on the core–shell (S3) is higher compared to other adsorbents previously testified in the literature. The cost-effective and eco-friendly prepared core–shell samples with good metal removal capacity have great potential for commercialization. 相似文献
|