Cobalt Ferrite Nano Research Articles

Effects of Bi3+ Substitution on Structural, Morphological, and Magnetic Properties of Cobalt Ferrite Nanoparticles

In this research, the structural, morphological, and magnetic properties of Bi-doped cobalt ferrite (CoFe2-xBixO4) nanoparticles with x = 0.0, 0.05, 1, 0.15, and 0.2, prepared by the sol-gel method, were studied. In order to characterize the samples, several equipment and analyses including thermo-gravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared spectrometer (FT-IR), and vibrating sample magnetometer (VSM) were used. The average crystallite sizes of the prepared CoFe2-xBixO4 were calculated using the Scherer, UDM, SSP, and Halder-Wagner methods. The average crystallite sizes for the samples were found in the range of 26 to 44 nm, which can be attributed to the grain growth of the particles. FT-IR spectrum showed bands in the range of 430 to 590 cm−1 due to the stretching vibration of an oxygen atom and metal ions (Fe-O), confirming the formation of spinel ferrite. Surface morphology of the samples was studied using FESEM. The VSM results showed that the saturation and remanence magnetizations increased by raising the doping values up to x = 0.1. The Curie temperature of the cobalt nanoferrites was determined using Faraday’s technique. The highest Curie temperature was found to be 580 °C for the undoped sample.

Surface Modification of Spinel Ferrite with Biopolymer for Adsorption of Cationic and Anionic Dyes in Single and Ternary Dye System

In this work, nano cobalt ferrite was modified with biopolymer sodium alginate in alginic form and the prepared magnetic composite (CoFN-Alg) was examined by different techniques such as Fourier transform infrared spectroscopy, transmission electron microscope with energy dispersive spectra, X-ray diffraction, thermo-gravimetric analysis, and Brunauer-Emmett-Teller equation. The CoFN-Alg composite was used as adsorbent to remove Congo red (CR), brilliant green (BG), and methylene blue (MB) dyes from single and ternary dye systems. The adsorption of different dyes on CoFN-Alg composite was studied at varying parameters such as contact time, varying pH, adsorbent dose, and initial concentration at different temperatures through batch mode. Results of kinetic studies revealed that the adsorption data of different dyes in single system as well as ternary system was best fitted in Lagergren pseudo second order model. Similarly, the adsorption equilibrium data was well correlated by Langmuir isotherm model in both types of dye systems. In single system, the maximum adsorption capacities of CR, BG, and MB dyes for CoFN-Alg composite were 93.0, 92.1, 95.8 mg/g and for ternary system were 60.0, 64.4, and 76.9 mg/g, respectively. The calculated adsorption thermodynamic parameters confirmed that adsorption process was spontaneous in nature. The results of regeneration studies concluded that CoFN-Alg composite retained around 78% regeneration efficiency even after five successive cycles in single as well as ternary system. The present study revealed that CoFN-Alg composite might be suitable alternative for the removal of different dyes in single as well as multi-component system.

Tunable structures of copper substituted cobalt nanoferrites with prospective electrical and magnetic applications

Spinel ferrites (SFs) show high potential in different aspects of modern technology. Particularly, copper ferrite represents a promising electrode material for supercapacitors and lithium based batteries. This paper is devoted to synthesizing and characterizing nanostructured copper substituted cobalt ferrites using an eco-friendly sol–gel method. Energy dispersive X-ray (EDX) and FT-IR analyses confirm the chemical composition and the successful formation of the cubic phase of CuFe2O4, respectively. XRD analyses based on Williamson–Hall (W–H) method indicate that the average crystallite size drops from 25.1 to 12.1 nm dependent on the Cu2+ content in the samples. Further, scanning electron microscopy (SEM) reveals that the CoFe2O4 (CFO) has a honeycomb structure, which gradually disappears with the soaring of Cu2+ content in the samples and converts to a porous sponge-like shape structure. The investigated copper substituted CFO holds a high specific surface area equals to 102.5139 m2 g−1 which satisfies the contaminant adsorption applications. The measured DC resistivity (ρDC = 108 Ω m) is high enough to meet the requirements of transformer cores applications. Due to the difference in the magnetic moment between Cu2+ and Co2+ cations, the coercivity of the CFO significantly depends on the Cu2+ content; it has declined by more than 50% for the system Co0.25Cu0.75Fe2O4 in comparison to the pure CFO (Hc = 1617.30 Gauss).

Study of hyperthermia temperature of manganese-substituted cobalt nano ferrites prepared by chemical co-precipitation method for biomedical application

Abstract The initiation of ferrite nanoparticles has changed the perception of nanotechnology in the biomedical field especially magnetic hyperthermia based application. Wet chemical co-precipitation method has been used to synthesize chitosan-coated Co1−xMnxFe2O4 (0.0 ≤ x ≤ 1.0, in the steps of 0.2) nano ferrites. From the XRD data, the lattice constant, ionic radii and bond lengths at tetrahedral sites and octahedral sites were estimated. The analysis revealed that the hoping lengths at tetrahedral and octahedral sites are increased with the addition of manganese content. The FESEM has shown that the ferrite nanoparticles are agglomerated in the powder sample. The magnetic characterization has been done by VSM. Heating of the nanoparticles is dependent on hysteresis loss that is related to the larger area of the hysteresis loop. In agreement with magnetization data, there shows a transition from ferromagnetic to paramagnetic behaviour revealed by Mossbauer spectra. From Mossbauer spectra, values of isomer shift, quadrupole splitting, and hyperfine field have been measured. Hydrodynamic diameter and polydispersity index (PDI) of all coated samples have been found in the limits that the samples can be used for biomedical applications. Hyperthermia temperatures of all coated ferrite samples have been measured. From the steep slope of time dependence temperature graph, the value of specific loss power (SLP) has been calculated and found that the SLP value is highest for Co0.8Mn0.2Fe2O4.

Superparamagnetic Behavior of Zn and Al Substituted Cobalt Nanoferrites

Nanostructured Zn- and Al-doped cobalt spinel ferrites ZnxCo1-xFe2-xAlxO4 (0 ≤ x ≤ 1.0) with particle size in the range of 7–13 nm were synthesized by glycol-thermal reaction. XRD analysis confirmed single-phase cubic spinel structure with no impurity phases. The Mossbauer spectra for Zn- and Al-substituted fine powders could be resolved into two quadrupole doublets associated with 57Fe nuclei in paramagnetic spin phase. An unusual reducing magnetization with increasing particle size has been observed. The field cooled and zero field cooled magnetization measurements show superparamagnetic nanoparticles in the compounds investigated. The blocking temperatures (TB) are sensitive to particle size. Larger particles are blocked at higher temperatures compared to smaller particles at the same field.

Effect on structural and magnetic properties of Mg2+ substituted cobalt nano ferrite

Abstract Nanoparticle-sized inverse spinel structured Cobalt ferrite materials doped with Mg2+ at lower concentrations have been synthesized using sol-gel auto combustion technique. Two-step annealing procedure has been employed to obtain a clear phase of the synthesized materials. Structural and phase formation have been studied using the thermo gravimetric analysis, powder X-ray diffraction and Fourier transform infrared spectroscopy. Powdered samples texture and morphology has been studied using scanning electron microscopy. Moreover, magnetic properties were studied by room temperature vibrating sample magnetometer. Lattice parameters and crystallite sizes in the range of 8.3702–8.3845 A and 53.2–81.2 nm, respectively, have been calculated. Tuned magnetic parameters have also been obtained using VSM measurement.

Role of rare-earth (Nd3+) ions on structural, dielectric, magnetic and Mossbauer properties of nano-sized CoFe2O4: useful for high frequency application

The glycine nitrate technique is used to synthesis a series of Neodymium substituted Cobalt Ferrite samples i.e. Co1-xNdxFe2O4 (x = 0, 0.1, 0.3, 0.5, 0.7). XRD, FT-IR, TEM, VSM and Mössbauer spectrum was carried out to investigate the structural, morphological and magnetic properties. Crystallite sizes calculated from the XRD patterns exhibited a decreasing trend with the increase in Nd content and was in good agreement with FESEM results. Temperature-dependent dielectric properties: dielectric constant (ε′), dielectric loss (ε″) and resistivity and activation energy were studied as a function of applied frequency in the range from 100 Hz to 1 MHz. The conductivity measurements divulge the semiconducting characteristic of the synthesised sample. The dielectric study indicated the dielectric dispersion curve to have possessed typical dielectric dispersion which can be explained on the basis of Koop’s theory based on the Maxwell–Wagner model. Incorporation of Nd in Cobalt nanoferrite significantly enhances the dielectric properties providing a gateway to high frequency device based application. The magnetic properties reveal a strong dependence on the grain size where the saturation magnetization reduced with the average particle size.

Effect of calcination temperature on structural and magnetic properties in cobalt ferrite nano particles

We discuss the calcination temperature dependence of the structural and magnetic properties of co-precipitated cobalt ferrite. Calcination process was performed under atmospheric condition without inert gas. High-purity cobalt ferrite nanoparticles are obtained experimentally. The size of the crystallites increases with the increase of the calcination temperature. Furthermore, the XRD analysis result show that cation redistribution occurs with the increase of the calcination temperature. The SEM result show that the structural organization of these particles changes from separate nanoparticles to the formation of compact granules with increasing calcination temperature. As a result, the saturation magnetization increases with the calcination temperature, reaching up to 62.30 emu/g. It was found that the cation distribution for both tetrahedral and octahedral sites affected by the calcination temperature.

Synthesis of Co1–xZnxFe2O4 and Evaluation of Structural, Magnetic, Antimicrobial Properties of ZnFe2O4, Co0.6Zn0.4Fe2O4 by Citrate Gel Method, Calcined at 600°C

Co1–xZnxFe2O4 was prepared by citrate precursor method using raw materials: citric acid, cobalt, zinc and iron nitrates and by following calcination at 600°C. This assessment presents the effect of substitution of the Zn2+ ion on the structural properties of cobalt nanoferrite. The structural characteristics of the calcined samples were determined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). X-ray diffraction studies of the nanoparticles heat-treated at 600°C confirms that the crystallite size is in the range of 22 to 29 mm and also the X-ray diffraction analysis indicates the formation of single phase ferrite particles in nano size. The morphology of the calcined sample was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mean particle size of Co0.6Zn0.4Fe2O4 was determined to be 19 nm calculated from TEM which is supporting the X-ray diffraction studies. The Fourier transform infrared spectra (FTIR) show two strong absorption bands in the series of ferrites between the range of 4500–500 cm−1 responsible for the characteristic of spinel ferrites. The high-frequency band and low-frequency band are assigned to the tetrahedral and octahedral complexes, respectively. The weight %, atomic %, and elemental analysis of calcined samples were confirmed by elemental spectral signals of energy dispersive spectroscopy (EDS). At the room temperature, magnetic measurements of pure ZnFe2O4 and Co0.6Zn0.4Fe2O4 were calculated based on hysteresis curves (Hc), it is observed that the substitution of nonmagnetic Zn2+ ion increases the magnetic behavior in mixed cobalt-zinc ferrites. The antimicrobial activity of ZnFe2O4, Co0.6Zn0.4Fe2O4 synthesized nanoferrites has been successfully tested against harmful microbes.

Microstructure and magnetic properties of cobalt ferrite nano powder prepared by solution combustion synthesis

In this study, cobalt ferrite nanoparticles (CoFe2O4NPs) were prepared by solution combustion synthesis using urea and glycine as fuels. The magnetic properties of the CoFe2O4 powders were modified by using various amounts of extra fuel (above the stoichiometric value). Thermodynamic calculations indicates that as the extra fuel increases, the amount of gases produced and the adiabatic flame temperature (Tad) rise. To investigate effect of urea, glycine and amount of extra fuel on the structural and magnetic properties of CoFe2O4 powders, the produced samples were studied by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), and Brunauer-Emmett-Teller (BET) technique. XRD results of the produced sample indicated that the single phase CoFe2O4with an average crystallite size between 17 and 33 nm was synthesized. By using two different type of fuel, the specific surface area of the produced powders were increased from 1.6 (glycine fuel) to 56.2 m2/g (urea fuel). By changing the type of fuel and the amount of extra fuel, the CoFe2O4 coercivity (Hc) ranges between 870 and 1667.8Oe and the saturation magnetization (Ms) varies between 31.6 and 83.7 emu/g. The solution combustion synthesized CoFe2O4 powders exhibit a hard ferrimagnetic behavior. Based on the results, Urea is the proper fuel for producing cobalt ferrite nanoparticles (with a particle size less than 100 nm) and in case of using glycine, the minimum amount of this fuel should be 2 times the stoichiometric amount.

Modulation in magnetic exchange interaction, core shell structure and Hopkinson’s peak with chromium substitution into Ni0.75Co0.25Fe2O4 nano particles

The ever growing applications and ever evolving challenges of magnetic nano particles has been motivating the researchers from various disciplines towards this area of magnetic nano particles. Cation substitutional effect on the magnetic structure of the nanoparticles forms a crucial aspect in their applications. Here the environmentally benign auto combustion method was employed to synthesize chromium substituted nickel cobalt ferrite (Ni0.75Co0.25Fe2-xCrxO4; x = 0, 0.10, 0.15) nano particles, from aqueous metal nitrate solutions. Chromium substitution has shown its effect on the structural, magnetic and electrical properties of Ni0.75Co0.25Fe2O4. Structural and phase analysis of the prepared samples show increased phase purity of ferrite sample with increasing Cr substitution. The TEM (Transmission Electron Microscope) image confirms the nano size of the particles, EDS (Energy dispersive X-ray Spectroscopy) has supported the stoichiometry of the prepared samples and FTIR (Fourier-transform infrared spectroscopic) analysis confirms the spinel structure and also suggests cation redistributions with chromium substitution. VSM (Vibrational Sample Magnetometer) is used to study the magnetic properties through magnetic hysteresis (M−H) loop and magnetic Hopkinson effect. All samples show hysteresis and show reduction in magnetic properties with increase in chromium content. The thermo magnetic study shows Hopkinson peak(s) in the magnetization vs. temperature (M−T) graph and also shows variation in the nature of Hopkinson peak with chromium substitution. Possible reasons for the changes in the nature of the peak are discussed.

Temperature dependent and applied field strength dependent magnetic study of cobalt nickel ferrite nano particles: Synthesized by an environmentally benign method

Spinel ferrites have come a long way in their versatile applications. The ever growing applications of these materials demand detailed study of material properties and environmental considerations in their synthesis. In this article, we report the effect of temperature and applied magnetic field strength on the magnetic behavior of the cobalt nickel ferrite nano powder samples. Basic structural properties of spinel ferrite nano particles, that are synthesized by an environmentally benign method of auto combustion, are characterized through XRD, TEM, RAMAN spectroscopy. Diffuse Reflectance Spectroscopy (DRS) is done to understand the nickel substitution effect on the optical properties of cobalt ferrite nano particles. Thermo magnetic studies using SQUID in the temperature range 5 K to 400 K and room temperature (300 K) VSM studies are performed on these samples. Fields of 0Oe (no applied field: ZF), 1 kOe (for ZFC and FC curves), 5 kOe (0.5 T), 50 kOe (5T) (for M-H loop study) are used to study the magnetic behavior of these nano particles. The XRD,TEM analysis suggest 40 nm crystallites that show changes in the cation distribution and phase changes in the spinel structure with nickel substitution. Raman micrographs support phase purity changes and cation redistributions with nickel substitution. Diffuse reflectance study on powder samples suggests two band gap values for nickel rich compounds. The Magnetic study of these sample nano particles show varied magnetic properties from that of hard magnetic, positive multi axial anisotropy and single-magnetic-domain structures at 5 K temperature to soft magnetic core shell like structures at 300 K temperature. Nickel substitution effect is non monotonous. Blocking temperature of all the samples is found to be higher than the values suggested in the literature.

Facile room temperature CTAB-assisted synthesis of mesoporous nano-cobalt ferrites for enhanced magnetic behaviour

We report a facile, room temperature synthesis of nanostructured mesoporous cobalt ferrites using the cationic surfactant, cetyltrimethylammonium bromide (CTAB). The synthesis was carried out at various concentrations of CTAB ranging from its pre- to post-micellar concentrations. The pristine and calcined samples exhibit pure cobalt ferrite phase which are confirmed by XRD studies. The morphology of all uncalcined samples was quasi-spherical as shown by TEM images. Nitrogen adsorption – desorption study on pristine samples indicates the presence of mesopores in them. The magnetic properties of the uncalcined and calcined samples were studied by vibrating sample magnetometry. Coercivity and saturation magnetization were found to vary with the concentration of the CTAB employed. Also, the pristine samples were soft magnets, whereas the calcined samples tended towards exhibiting hard magnetism. We have proposed a mechanism to explain the mesoporosity of nanostructured ferrite based the role of CTAB in the present synthetic method.

Fungicides: Nanomaterial Fungicides: In Vitro and In Vivo Antimycotic Activity of Cobalt and Nickel Nanoferrites on Phytopathogenic Fungi (Global Challenges 9/2017)

Fungicides: Nanomaterial Fungicides: In Vitro and In Vivo Antimycotic Activity of Cobalt and Nickel Nanoferrites on Phytopathogenic Fungi (Global Challenges 9/2017)

Study of superparamagnetic nano particles of MnxCo1−xFe2O4 ferrite system prepared by co-precipitation technique

The ferrites with magnetic nano-particles of MnxCo1−xFe2O4 (with x = 0.0 to 1.0, step 0.2) system are prepared by the chemical co-precipitation method. Structural and magnetic properties of Mn2+ doped cobalt nano ferrites have been studied by x-ray diffraction (XRD), scanning electron microscopy (SEM), saturation magnetization and low field AC susceptibility. The crystallite size is determined from the FWMH of the higher angle Bragg line (4 0 0) using the Scherer’s formula. The saturation magnetization at 300 K in the peak field of 5 kOe is measured using B → H loop technique. The observed saturation magnetic moment is found very low compared to the Neel’s magnetic moment. The lower value of observed magnetic moment is explained on the basis of high magneto-crystalline anisotropy and exchange disorder. The Curie temperatures are determined through thermal variation of low field (0.5 Oe) AC susceptibility. All the plots of thermal variation AC susceptibility exhibit large hump due to single domain to superparamagnetic transition which is the characteristic of high anisotropic ion present in the system. The ZFC-FC curves exhibit thermo-magnetic irreversibility. The magnetic behavior observed through Mossbauer spectra also supports the concept of fine particle superparamagnetism.

Anealling dependence of structural and magnetic properties in aluminum substituted cobalt-ferrite nano particle

Anealling dependence of structural and magnetic properties in aluminum substituted cobalt ferrite nano particle are presented here. The composition is defined by the mole-stociometry calculation. The co-precipitation method is performed to produce of the aluminum substituted cobalt ferrite. The anealling temperature are selected to be 600°C, 800°C and 1000°C for 5 hours at atmosphere condition. The XRD results show that the XRD-peak increase with the increase of the anelling temperature. It mean that the fine crystalline structure realize at the higher temperature. The The VSM results indicate that the saturated magnetisation increase with increasing anealling temperature. This is can be explained that the refine of crystalline structure is also promote re-distribution cation at crystalline cites which the final of the magnetic moment become large at a higher temperature anealling.

Exploring the magnetic and structural properties of Nd-doped Cobalt nano-ferrite for permanent magnet applications

Abstract CoFe 2 O 4 and Co 0.5 Nd 0.5 Fe 2 O 4 spinel ferrites have been synthesized by coprecipitation method, X-ray diffraction (XRD), Transmission electron microscopy (TEM), and superconducting quantum interference device magnetometer (SQUID) techniques were used to characterize crystal structure, morphology and magnetic properties. Spinel structure of single phase is obtained according to XRD results for both samples. From TEM characterization results, we obtained a spherical morphology for CoFe 2 O 4 with an average of 8.71 nm and a nanorod morphology for Nd doped Cobalt ferrite with a particle diameter of about 6 nm and length of 40 nm. According to the hysteresis loop, Co 0.5 Nd 0.5 Fe 2 O 4 exhibits a maximum energy product (BH) max of 0.431 MGOe (3.434 kJ/m 3 ) at room temperature, with an enhancement of 7% compared to pure cobalt ferrites nanoparticles, which prove the efficiency of this material in permanent magnets application.

Morphological, Infrared and Structural Studies for Nano Cobalt Ferrite Doped with Lanthanum

A series of LaxCoFe2-xO4 prepared by flash method, where x=0.05, 0.1, 0.15, 0.2, 0.25 and 0.3. Thepowder samples were characterized by X-ray diffraction, FTIR and TEM (transmission Electron Microscope). Thex-ray analysis shows that the samples have a single phase cubic spinel structure. The lattice constant was founded tobe nearly constant up to x=0.25 and then increase as lanthanum content increase. The FTIR spectra of the samplewere recorded from 200-4000 cm-1, which analyzed the molecular structure of the samples and the formation ofspinel structure in bulk and nano modes. The HRTEM photographs clearly show the presence of cubic nanoparticlewith average diameter of 16nm for flash samples. The high resolution (HRTEM) indicates the presence of latticeplanes which confirm the crystalline nature of the sample. The effect of La3+ ions on dielectric properties arepresented in this paper.

Structural and Magnetic Studies of Nano-crystalline Ferrites MFe2O4 (M = Zn, Ni, Cu, and Co) Synthesized Via Citrate Gel Autocombustion Method

Nano-crystalline ferrites with the chemical formula MFe2O4 (M = Zn, Ni, Cu, and Co) were synthesized via autocombustion route with citric acid as fuel. The ratio of citric acid to metal nitrate was taken as 1:1. The synthesized samples were characterized by powder X-ray diffraction and far-IR spectroscopy. The measured lattice constants and observed characteristic IR absorption bands of all samples were in good agreement with the reported values and showed the formation of a cubic spinel structure. The crystallite sizes of all samples were determined using high-intensity peaks and a W-H plot. The crystallite sizes of all samples were observed to be in the range of 16–26 nm with the least crystallite size of 16.8 nm for copper ferrite. All structural parameters were calculated using an experimental lattice constant and an oxygen positional parameter and correlated with far-IR results. Zinc and copper owing to their large cation radii showed the expansion of the lattice in view of the oxygen positional parameter. Magnetic measurements were carried out using a vibrating sample magnetometer at room temperature, and parameters such as saturation magnetization, coercivity, remanence, squareness ratio, and Bohr magnetons were calculated. Among all synthesized nano-ferrites, cobalt nano-ferrite showed the highest saturation magnetization of 41 emu/g, whereas zinc ferrite displayed a low saturation magnetization value of 12.87 emu/g.

Modification of Co/Cu nanoferrites properties via Gd3+/Er3+doping

Pure nanoparticles of the rare earth-substituted cobalt and copper ferrites with general formula Me Gd0.025 Er0.05 Fe1.925 O4 (Me = Co, Cu) were prepared by the chemical citrate method. X-ray diffraction, field emission scanning electron microscopy, BET analysis are utilized to study the effect of rare earth substitution and its impact on the physical properties of the investigated samples. Rare earth-doped cobalt shows type IV isotherm suggesting mesopore structure with its hysteresis loop. The estimated crystallite sizes are found in the range of 21.49 and 36.11 nm for the doped Co and Cu samples, respectively. The magnetic properties of rare earth-substituted cobalt and copper ferrites showed a definite hysteresis loop at room temperature. An increase in coercivity and a decrease in saturation magnetization were detected. This can be explained in view of weaker nature of the Re3+–Fe3+ interaction compared to Fe3+–Fe3+ interaction. Greater than 1.13-fold increase in coercivity (Hc = 2184 Oe) was observed in doped cobalt nanoferrite samples compared to copper (Hc = 1936 Oe). It was found that the decreasing in temperature leads to great improvement in the magnetic properties of the investigated samples. As the magnetic recording performance of the magnetic samples is improved for well-crystallized samples with nano-structural, the effect of rare earth substitution seems to be particularly valuable in this regard.