Ferrite Nanofibers Research Articles

Electrospun bismuth ferrite nanofibers for potential applications in ferroelectric photovoltaic devices.

Bismuth ferrite (BFO) nanofibers were synthesized via a sol-gel-based electrospinning process followed by thermal treatment. The influences of processing conditions on the final structure of the samples were investigated. Nanofibers prepared under optimized conditions were found to have a perovskite structure with good quality of crystallization and free of impurity phase. Ferroelectric and piezoelectric responses were obtained from individual nanofiber measured on a piezoelectric force microscope. A prototype photovoltaic device using laterally aligned BFO nanofibers and interdigital electrodes was developed and its performance was examined on a standard photovoltaic system. The BFO nanofibers were found to exhibit an excellent ferroelectric photovoltaic property with the photocurrent several times larger than the literature data obtained on BFO thin films.

Electrospun synthesis and lithium storage properties of magnesium ferrite nanofibers

In this study, we successfully synthesized magnesium ferrite (MgFe2O4) nanofibers by a facile electrospinning technique followed by calcining at 800°C. The lithium storage properties of MgFe2O4 nanofibers as anode materials for lithium-ion batteries have been discussed for the first time. It is demonstrated that MgFe2O4 nanofibers electrode not only deliver a high initial discharge capacity of around 1304mAhg−1, but also maintain a reversible capacity of 714mAhg−1 after 100 cycles. Moreover, the MgFe2O4 nanofibers electrode also exhibits high capacity at higher charge/discharge rate. Even at a current density of 2000mAg−1, the reversible capacity can attain 409mAhg−1 after 100 cycles, suggesting its excellent rate capability. The superior lithium storage properties of the MgFe2O4 nanofibers electrode may be related to the unique continuous fibrous morphologies, nanostructured architectures, porous structures, and large specific surface area, which provide an easily Li+ diffusion path and promote electron transfer. In addition, the formation of MgO appears to act as a buffer layer that prevents agglomeration of nanocrystalline, accommodate the large volume change and reduces polarization during cycling.

Tunable properties of GO-doped CoFe2O4 nanofibers elaborated by electrospinning

We report on the synthesis of cobalt ferrite (CoFe2O4) nanofibers doped with graphene oxide (GO) via the electrospinning technique and the study of their chemical, structural and magnetic properties.

Superior elastomeric nanocomposites with electrospun nanofibers and nanoparticles of CoFe2O4for magnetorheological applications

Cobalt ferrite nanofiber filled polydimethylsiloxane nanocomposites show 100–400% improvement in magnetorheological properties compared to that with nanoparticles.

Preparation and microwave absorption mechanisms of the NiZn ferrite nanofibers

In this paper, the NixZn(1−x)Fe2O4 (x=0.2, 0.4, 0.5, 0.6, 0.8) ferrite nanofibers were synthesized by electrospinning method. The microstructure, electromagnetic properties and microwave absorption mechanisms were analyzed (in detail). The results indicated that the nanofiber diameter, the saturation magnetization, the coercivity and the electromagnetic properties could be optimized by tuning the Ni2+ content. The Ni0.5Zn0.5Fe2O4 ferrite nanofiber finally performed the excellent microwave absorption properties. The reflection loss was less than −10dB in the whole X-band frequencies. The analysis of microwave absorption mechanism indicated that the microwave absorption bandwidth was mainly depended on the input impedance matching, the enhanced electromagnetic loss properties ensured that the entering wave could be mostly absorbed, and the frequency appearing the reflection loss peak was determined by the absorber thickness.

Dynamic Magnetic Properties of Electrospun NiZn Spinel Ferrite Nanofibers

NiZn spinel ferrite nanofibers with diameters in 50-100 nm were fabricated by electrospinning followed by thermal treatment. Deploying a rotating collector, nanofibers can achieve certain degree of alignment. The morphology phase contents, static, and dynamic magnetic properties of ferrite fibers were experimentally studied. Measured magnetic hysteresis loops indicate that the NiZn ferrite nanofibers are anisotropic with easy magnetization axis along the fiber alignment direction. The relationship between ferromagnetic resonant frequencies of nanofibers and bias magnetic fields was determined and can be described using a modified Kittel's formula developed for polycrystalline ferrites.

High lithium electroactivity of electrospun CuFe2O4 nanofibers as anode material for lithium-ion batteries

In this study, copper ferrite (CuFe2O4) nanofibers were successfully fabricated by a combination of electrospinning and calcination process. The crystal structure was investigated by X-ray diffractomentry, and the results show only peaks of CuFe2O4 could be observed from the product obtained at 800°C, indicating the formation of pure compound. SEM and TEM images showed the as-spun CuFe2O4 nanofibers possessed good continuous fiber morphology with an average diameter of about 66nm. The electrochemical properties of electrospun CuFe2O4 nanofibers as anode material for lithium-ion batteries were discussed for the first time. The results demonstrated that the electrospun CuFe2O4 nanofibers anode exhibited a high initial discharge capacity of 1226.0 mAh g−1, and maintained a stable capacity of 572.4 mAh g−1 after 50 cycles. Meanwhile, the electrodes showed high capacity at higher discharge and charge rate. The excellent electrochemical properties of electrospun CuFe2O4 nanofibers anode were attributed to the high crystallinity, as well as the unique mesoporous and fibrous structures.

The Cobalt Zinc Spinel Ferrite Nanofiber: Lightweight and Efficient Microwave Absorber

To solve the heavy mass problem of the traditional spinel ferrite using as the microwave absorber, the CoxZn(1−x)Fe2O4 (x = 0.2, 0.4, 0.6, 0.8) ferrite nanofibres were synthesized by electrospinning method. The phase composition, morphology, and electromagnetic properties were analyzed. The results showed that all the as‐prepared CoxZn(1−x)Fe2O4 ferrites exhibited the homogeneous nanofibrous shape. The saturation magnetization and coercivity were enhanced by tuning the Co2+ content. The electromagnetic loss analysis indicated that the Co0.6Zn0.4Fe2O4 ferrite nanofiber performed the strongest microwave attenuation ability. The microwave absorbing coating containing 15 wt% of Co0.6Zn0.4Fe2O4 ferrite nanofiber showed the reflection loss less than −10 dB in the whole X‐band and 80% of the Ku‐band frequencies. Meanwhile, the surface density was only 2.4 Kg/m2.

Unique electromagnetic properties of the zinc ferrite nanofiber

The ZnFe2O4 ferrite nanoparticle and nanofiber were synthesized by electrospinning method. The phase composition, morphology, magnetic and electromagnetic properties were analyzed. The results showed that both the samples exhibited a pure phase of spinel type ferrite. The ZnFe2O4 ferrite nanoparticle was aggregated, while the ZnFe2O4 ferrite nanofiber performed the homogeneous nano-fibrous shape as well as single-particle-chain structure. The magnetic analysis indicated that the ZnFe2O4 ferrite nanofiber showed ferromagnetic behaviour. Moreover, the dielectric loss and magnetic loss properties of ZnFe2O4 ferrite nanofiber were both enhanced due to its better dipole polarization, interfacial polarization and shape anisotropy.

Aligned Ferrite Nanofibers Fabricated by Electrospinning

Using polyethylene pyrrole(PVP) and metal nitrate as precursors,smooth,uniform,and aligned Co0.8Zn0.2Fe2O4 nanofibers were prepared via electrospinning and sol-gel method,and subsequent heating process.The thermal decomposition process,crystal structure,and morphology of the nanofibers were studied by means of thermogravimetric-differential thermal analysis(TG-DTA),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM),respectively.Co0.8Zn0.2Fe2O4 nanofibers with particle sizes of 20.5—61.9 nm and a well-developed spinel structure were successfully obtained after calcinations of the as-spun nanofibers at 550—950 ℃ in air for 3 h.The as-spun nanofibers collected at 2000 r/min with the best morphology is ca.300 nm in diameter,which decreases down to ca.70 nm on annealing at 750 ℃ from SEM and TEM images.Room temperature magnetization results showed a ferromagnetic behavior of the calcined Co0.8Zn0.2Fe2O4 nanofibers.Compared with CoFe2O4 nanofibers,the anisotropy of Co0.8Zn0.2Fe2O4 nanofibers decreased,resulting in the lower coercivity(Hc) and higher saturation magnetization(Ms) of the obtained sample.The Ms of the sample increased with the calcinations temperature,while the Hc reaches a maximum value of 16.6 A/m at the calcinations temperature of 750 ℃.The Hc results suggest that the critical single-domain size of Co0.8Zn0.2Fe2O4 is about 44 nm.In comparison with a powder sample prepared using conventional sol-gel process,significant differences in magnetic properties were noted between these two samples.

Synthesis of Nickel-Based Ferrite Nanofibers and their Static Magnetic and Microwave Absorption Properties

Ni0.5Zn0.5Fe2O4, Ni0.3Cu0.2Zn0.5Fe2O4 and Ni0.4Co0.2Zn0.4Fe2O4 spinel ferrite nanofibers with 60–100 nm in diameter were fabricated through the sol-gel assisted electrospinning method, followed by calcination at 600°C for 2h in air. The phase structure morphology and element composition of these nanofibers were determined by XRD, FE-SEM and EDS. Magnetic measurements were used to justify the ferromagnetic properties of these nanofibers. Microwave absorption, which was in the range of 2-18 GHz, was studied by a vector network analyzer. The adoption of Cu2+ and Co2+ substitution was found to improve the microwave absorption in relation to non-substituted NiZn ferrite nanofibers. Reflection loss exceeding –5 dB is obtained between 11 and 18 GHz for silicon rubber composites containing 15 vol% nickel-based ferrite nanofibers with coating thicknesses of 3 mm. The results indicate that the prepared nickel-based ferrite nanofibers possess good electromagnetic wave absorption performance in the Ku band and have great potential as microwave absorber for practical applications.

Electrospinning of magnetical bismuth ferrite nanofibers with photocatalytic activity

Bismuth ferrite (BiFeO3) nanofibers were prepared by combining the electrospinning technique with sol–gel chemistry. The structural features of the as-prepared nanofibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained BiFeO3 nanofibers showed a rhombohedral perovskite structure after getting annealed in an argon atmosphere. Both SEM and TEM results showed that BiFeO3 fibers were composed of nanocrystalline particles. The photocatalytic behaviors of BiFeO3 nanofibers were investigated by the degradation of Rhodamine B (RhB). BiFeO3 nanofibers exhibited excellent catalytic activity under UV light irradiation, as well as under visible light irradiation in the presence of H2O2. The catalyst was further examined by magnetic measurement. The BiFeO3 nanofibers exhibited a ferromagnetic behavior at room temperature, which was associated with the nanometer-size of BiFeO3 particles. This provides an easy and efficient way to recover BiFeO3 photocatalysts from the suspension system by applying an external magnetic field.

Synthesis of ferromagnetic nickel ferrite nanofibers via electrospinning with iron acetate as an iron precursor

We report the synthesis of nickel ferrite nanofibers via an elecrospinning technique particularly using iron (II) acetate as an iron precursor. Nanofibers of a single-phase nickel ferrite with a uniform diameter of ∼90 nm were successfully synthesized by adopting a properly prepared solution and calcination condition. Individual nickel ferrite nanofibers synthesized by electrospinning were made up of nanograins of ∼20 nm in diameter. In addition, the hysteresis observed in a magnetization measurement confirmed their ferromagnetism, supporting their potential use in magnetic devices. These results demonstrate that the use of iron (II) acetate as an iron precursor is another way to synthesize ferromagnetic nickel ferrite nanofibers.

Electrospinning preparation, characterization and magnetic properties of cobalt–nickel ferrite (Co1−xNixFe2O4) nanofibers

Uniform Co1−xNixFe2O4 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanofibers with average diameter of 110nm and length up to several millimeters were prepared by calcination of electrospun precursor nanofibers containing polymer and inorganic salts. The as-spun and calcined nanofibers were characterized in detail by TG–DTA, XRD, FE-SEM, TEM, SAED and VSM, respectively. The effect of composition of the nanofibers on the structure and magnetic properties were investigated. The nanofibers are formed through assembling magnetic nanoparticles with poly(vinyl pyrrolidone) as the structure-directing template. The structural characteristics and magnetic properties of the resultant nanofibers vary with chemical composition and can be tuned by adjusting the Co/Ni ratio. Both lattice parameter and particle size decrease gradually with increasing nickel concentration. The saturation magnetization and coercivity lie in the range 29.3–56.4emu/g and 210–1255 Oe, respectively, and both show a monotonously decreasing behavior with the increase in nickel concentration. Such changes in magnetic properties can mainly be attributed to the lower magnetocrystalline anisotropy and the smaller magnetic moment of Ni2+ ions compared to Co2+ ions. Furthermore, the coercivity of Co–Ni ferrite nanofibers is found to be superior to that of the corresponding nanoparticle counterparts, presumably due to their large shape anisotropy. These novel one-dimensional Co–Ni ferrite magnetic nanofibers can potentially be used in micro-/nanoelectronic devices, microwave absorbers and sensing devices.

Fabrication and Magnetic Property of BaSmxFe12–xO19 (x ≦ 0.4) Nanofibers

BaSm(x)Fe(12-x)O19 (x < or = 0.4) ferrite nanofibers were prepared by sol-gel method from starting reagents of metal salts and citric acid. These nanofibers were characterized by TG-DTA, FTIR, SEM, XRD and VSM. These results show that the BaSm(x)Fe(12-x)O19 (x < or = 0.4) ferrite nanofibers were obtained subsequently from calcination at 750 degrees C for 1 h. The BaSm(x)Fe(12-x)O19 (x < or = 0.4) microstructure and magnetic property are mainly influenced by chemical composition and heat-treatment temperature. The grain sizes of BaSm0.3Fe11.7O19 ferrite nanofibers are in a nanoscale from 40 nm to 62 nm corresponding to the calcination temperature from 750 degrees C to 1050 derees C. The saturation magnetization of BaSm(x)Fe(12-x)O19 ferrite nanofiber calcined at 950 degrees C for 1 h initially decreases with the Sm content from 0 to 0.3 and then increases with a further Sm content, while the coercivity exhibits a continuous increase from 348 kA x m(-1) (x = 0) to 427 kA x m(-1) (x = 0.4). The differences of magnetic properties are attributed to lattice distortion and enhancement for the anisotropy energy.

Magnetic framework composites for polycyclic aromatic hydrocarbon sequestration

A framework composite was prepared by growing MOF-5 crystals on ferrite nanofibers. We demonstrated that the resulting superparamagnetic framework composite was used for the sequestration of a carcinogenic molecule (1,2-benzanthracene), enabling the loaded vessel to then be collected and removed from the solution using the magnetic properties of the embedded nanofibers.

An intermediate-temperature solid oxide fuel cell with electrospun nanofiber cathode

Lanthanum strontium cobalt ferrite (LSCF) nanofibers have been fabricated by the electrospinning method and used as the cathode of an intermediate-temperature solid oxide fuel cell (SOFC) with yttria-stabilized zirconia (YSZ) electrolyte. The three-dimensional nanofiber network cathode has several advantages: (i) high porosity; (ii) high percolation; (iii) continuous pathway for charge transport; (iv) good thermal stability at the operating temperature; and (v) excellent scaffold for infiltration. The fuel cell with the monolithic LSCF nanofiber cathode exhibits a power density of 0.90 W cm−2 at 1.9 A cm−2 at 750 °C. The electrochemical performance of the fuel cell has been further improved by infiltration of 20 wt% of gadolinia-doped ceria (GDC) into the LSCF nanofiber cathode. The fuel cell with the LSCF–20% GDC composite cathode shows a power density of 1.07 W cm−2 at 1.9 A cm−2 at 750 °C. The results obtained show that one-dimensional nanostructures such as nanofibers hold great promise as electrode materials for intermediate-temperature SOFCs.

Influence of La Doping on Magnetic and Optical Properties of Bismuth Ferrite Nanofibers

The influence of La doping on the crystal structure, ferromagnetic, and optical properties of BFO nanofibers was investigated. Bi1−xLaxFeO3 ultrafine nanofibers were synthesized by the electrospinning method. The surface morphology and crystal structure of the as‐spun and sintered fibers were not affected by the doping. The impurity phases of the BFO crystals were weakened with the increment of La concentration. The magnetization field curves showed that the magnetization weakened under low La doping proportion, but strengthened with the increase of the doped proportion. The magnetization curves also showed continuous strong enhancement of ferromagnetic behavior. The results of UV‐vis and photoabsorption testing revealed little influence of La doping on the optical property.

Microstructure, magnetic properties and exchange–coupling interactions for one-dimensional hard/soft ferrite nanofibers

SrFe12O19 (SFO)/Ni0.5Zn0.5Fe2O4 (NZFO) composite ferrite nanofibers with diameters about 120nm have been prepared by the electrospinning and calcination process. The SFO/NZFO composite ferrites are formed after calcined at 700°C for 2h and the composite nanofibers with various mass ratios obtained at 900°C are fabricated from NZFO grains about 16–40nm and SFO grains of 19–45nm with a uniform phase distribution. With the SFO ferrite content increasing, the coercivity (Hc) and remanence (Mr) for the composite ferrite nanofibers initially increase, reaching maximum values of 379.8kA/m (297K) and 242.2kA/m (77K), 39.1Am2/kg (297K) and 53.5Am2/kg (77K), respectively, at a mass ratio (SFO:NZFO) of 4, and then show a reduction tendency with a further increase of the mass ratio. This enhancement in magnetic properties is attributed to the competition of the exchange–coupling interaction and the dipolar interaction in the composite nanofibers.

One-Dimensional SrFe&lt;SUB&gt;12&lt;/SUB&gt;O&lt;SUB&gt;19&lt;/SUB&gt;/Ni&lt;SUB&gt;0.5&lt;/SUB&gt;Zn&lt;SUB&gt;0.5&lt;/SUB&gt;Fe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt; Composite Ferrite Nanofibers and Enhancement Magnetic Property

SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers of diameters about 100 nm with mass ratio 1:1 have been prepared by the electrospinning and calcination process. The SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrites are formed after calcined at 700 degrees C for 2 hours. The composite ferrite nanofibers are fabricated from nanosized Ni(0.5)Zn(0.5)Fe2O4 and SrFe12O19 ferrite grains with a uniform phase distribution. The ferrite grain size increases from about 11 to 36 nm for Ni(0.5)Zn(0.5)Fe12O4 and 24 to 56 nm for SrFe12O19 with the calcination temperature increasing from 700 to 1100 degrees C. With the ferrite grain size increasing, the coercivity (Hc) and remanence (Mr) for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers initially increase, reaching a maximum value of 118.4 kA/m and 31.5 Am2/kg at the grain size about 40 nm (SrFe12O19) and 24 nm (Ni(0.5)Zn(0.5)Fe2O4) respectively, and then show a reduction tendency with a further increase of the ferrite grain size. The specific saturation magnetization (Msh) of 63.2 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers obtained at 900 degrees C for 2 hours locates between that for the single SrFe12O19 ferrite (48.5 Am2/kg) and the single Ni(0.5)Zn(0.5)Fe2O4 ferrite (69.3 Am2/kg). In particular, the Mr value 31.5 Am2/kg for the SrFe12O19/Ni(0.5)Zn(0.5)Fe2O4 composite ferrite nanofibers is much higher than that for the individual SrFe12O19 (25.9 Am2/kg) and Ni(0.5)Zn(0.5)Fe2O4 ferrite (11.2 Am2/kg). These enhanced magnetic properties for the composite ferrite nanofibers can be attributed to the exchange-coupling interaction in the composite.