Nano Ferrites Research Articles

An efficient one pot multicomponent synthesis of pyrano pyrazoles using Cu2+ doped Ni-Zn nano ferrite catalyst

An efficient one pot multicomponent synthesis of Pyrano (2,3-C) Pyrazoles (5) from ethyl acetoacetate (1), hydrazine hydrate (2), aromatic aldehydes (3) and malononitrile (4) using magnetically recoverable Cu2+ doped Ni-Zn Nano Ferrite catalyst has been developed. The workup process was clean and products obtained in high yields in shorter time. The Cu2+ doped Ni-Zn nano ferrite catalyst, prepared by the Sol-gel auto-combustion method. All precursors were sintered at 400 0C for four hours. The XRD pattern illustrates formation of single phase cubic nano spinel ferrite. The microstructure and morphology of the prepared samples were studied by scanning electron microscopy (SEM) and Transmission Electron Microscope (TEM) illustrates the fine crystallite structure with weak agglomeration. The IR spectra shows two major absorption bands, the highest ν1, assigned to stretching vibrations of the metal at the tetrahedral site, while the lower ν2 assigned to octahedral site.

Structural, optical, elastic and magnetic properties of Ce and Dy doped cobalt ferrites

Abstract The CoCexDyxFe2-2xO4 (x = 0.0, 0.01, 0.02, 0.03, 0.04, 0.05) have been prepared by sol-gel auto-combustion technique. The structural result confirmed the formation of single phase cubic spinel structure showed by XRD. Crystallite size obtained from the XRD is in the range of 24–28 nm, whereas particle size obtained from the transmission electron microscopy is in the range of 20–30 nm. It is also found that the cation distribution of CoCexDyxFe2-2xO4 resulted in the Fe3+ and Co ions occupy both tetrahedral A-site and octahedral B-site, whereas Ce and Dy cation distributed in both of them. The photoluminescence (PL) analysis reveals that all prepared samples contain four bands; (i) peak centered at 412 nm corresponding to ultraviolet (UV) band i.e. near band edge emission, (ii) a high intensity peak centered at 434 nm belonging to violet band, (iii) a low intensity and sharpness peak positioned at 466 nm refers to blue band, and (iv) a broad and very low intensity peak observed at 502 nm assigned to green band. FTIR results of the prepared samples showed that two vibration bands between 600 cm−1 and 400 cm−1 belonging to the stretching vibration of tetrahedral metal-oxygen bond (vA) and stretching vibration of octahedral site (vB) respectively. Mossbauer spectroscopy has also been performed to investigate the hyperfine structure of undoped, Ce and Dy co-doped cobalt nano ferrites. The higher values of MS and Hhf for x = 0.01 composition can be attributed to the occupation of Dy3+ ions in octahedral site whereas the Ce3+ ions occupied to tetrahedral site.

A study of dielectric relaxation properties of ZnFe2-xBixO4 nano Ferrites synthesized by sol-gel combustion method

A series of bismuth doped zinc nano ferrite particles with the r formula ZnBixFe2-xO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method; and these compositions were sintered at 600°C for 5 hrs. With the effect of bismuth doping, the structural properties of all prepared samples were characterized by X-ray diffraction (XRD). The X-ray diffraction spectra analyses confirm single phase cubic (FCC) spinal structure. The average crystallite size (D) of the samples found to be in the range 17-20 nm. The dielectric properties viz., dielectric constant (ε′), dielectric loss tangent (tan δ) and AC conductivity σAC) were measured at room temperature in the range 20Hz to 2MHz, which confirm the normal ferrite behavior. In the present research work, we are intended to extend dielectric relaxation studies of these samples with the help of Cole-Cole plots. The Cole-Cole plots of the bismuth doped zinc ferrites were drawn as a function of ε′ and ε″ (where, ε″=ε′ tan δ) and hence we have determined the spreading factor (β) for all the samples. It was observed that β decreases with the increase of the concentration of B2O3. It is noticed that the dielectric parameters ε′, tan δ and σAC have exhibited the similar trend. These samples may find suitable applications in electrolytic elements in battery technology.

Development of Magnetic Materials Based on Micro-Nano Particles Natural Ferrite as Microwaves Absorber Materials

Ferrite-based magnetic materials (ferrites) can be simple iron oxide compounds such as Fe2O3 or Fe3O4, and similar compounds containing other cations besides iron, such as BiFeO3, CaFe 4O7, and BaFe12O19. The solid phase of these compounds generally has varying magnetic properties, depending on the cation (A+m) which is the substitution of the iron cation (Fe+3) in its crystal structure. In addition to the magnetic properties of interest, the compound in question also has strong absorption properties in electromagnetic waves in the frequency interval of 1 - 20 GHz (microwave), which is commonly used in the world of communication and radar technology. With these properties it is possible to develop these materials for electromagnetic shielding and stealth technology applications. As a magnetic element, ferrite material requires a conductive reflector element, to form a “core - shell” or “matrix - filler” system which results in absorption properties. The research that has been developed is in the form of Fe3O4 based micro-nano magnetic powder made from natural ferrite (iron sand). The sythesized of magnetic micro-nano particles using chemical extraction-milling and coprecipitation methods. Morphology of micro-nano particles ferrites has been confirmed by using SEM and TEM. The results of measurements of absorption of microwaves using a Vector Network Analyzer showed that the ferrite nano particle powder has greater absorption power (Reflection Loss < - 20 dB) than micro particle powders with ≥ 99 % absorption in the “X-band” region. The extraction-milling method is simpler and more economical than the chemical coprecipitation method so that it is suitable to be an alternative method for producing large-scale ferrite powder.

Structural, Magnetic, Electrical and Photo-Fenton Properties of Copper Substituted Strontium M-Hexagonal Ferrite Nanomaterials via Chemical Coprecipitation Approach.

Copper substituted strontium ferrite nano spinels were synthesized by facile chemical coprecipitation method. Structural properties of all the nano materials were examined using Powder X-ray Diffraction of size ranging 22-50 nm and High Resolution Transmission Electron Microscopy which further revealed the formation of hexagonal spinel structure. The analysis of FT-IR spectra of all the samples confirmed the formation of M-O bond with spinel structure having characteristic peaks at 422 cm-1 and 586 cm-1. All the samples were subjected to dielectric studies at room temperature. A quite narrow band gap around 1.5-1.6 eV for all the samples indicates that these ferrites can behave as visible light photocatalysts. The as synthesized nano spinels were proposed to be promising heterogeneous Photo-Fenton catalysts under visible light for the degradation of organic pollutants. The photo catalytic degradation results revealed 94% degradation for all the prepared nano catalysts. The materials displayed remarkable photo-stability with recyclability up to five consecutive cycles. VSM studies of the materials exhibited weak ferromagnetic property with high surface area. Therefore, these magnetic materials presented no significant loss in activity specifying an exceptional capacity of ferrites to remove organic pollutants from wastewater.

Structural, thermal, spectral, optical and surface analysis of rare earth metal ion (Gd3+) doped mixed Zn–Mg nano-spinel ferrites

The present work reports the structural, thermal, spectral, optical and surface analysis of rare earth metal ion (Gd3+) doped mixed Zn–Mg nano-spinel ferrites. The samples of Gd3+ doped Zn–Mg nano ferrites with equi-amount chemical composition i.e. Zn0.5Mg0.5Fe2-xGdxO4 (0.00 ≤ x ≤ 0.10 in step of 0.02) were prepared by self-ignited sol-gel route. The variance in the thermal behaviour and spinel phase development with weight loss percentage in the prepared samples was investigated by TG-DTA technique. The powder X-ray diffraction (P-XRD) patterns ensured the nanocrystalline mono-phasic formation and spinel-cubic structure of all the samples. The trend of increment in lattice constant (a) and decrement in crystallite (t) size was observed with the doping of Gd3+ ions. The appearance of two requisite vibrational stretching modes was affirmed by the FT-IR spectral studies. The UV–Vis optical analysis displayed the augmentation in absorbance and drastic decrement in energy band gap value (1.96 eV–1.83 eV) with Gd3+ doping. The photo-luminescent (PL) studies revealed the broad near band-edge emission in visible wavelength range (523 nm–528 nm) for all the samples. The surface parameters investigation was undertaken with the help of BET isotherms recorded by the N2-physisorption and BJH model. The various surface parameters such as BET surface area, volume and radius of the pores, distribution of the pore sizes etc were construed from the BET data. The enhancement in these surface parameters via Gd3+ doping was noted for all the samples. The outcomes of the present work reflects the influential doping of Gd3+ ions in Zn–Mg nano ferrites, which can be implementable for bio-applications as thermal seeds in magnetic hyperthermia or as contrast enhancer in medical MRI imaging.

Spinel Structured Copper Ferrite Nano Catalyst with Magnetic Recyclability for Oxidative Decarboxylation of Phenyl Acetic Acids

A simple, efficient and environmentally benign method has been discussed for the synthesis of aldehydes and ketones by the oxidative decarboxylation of phenylacetic acid under ligand free condition using simple, efficient, preparatively easy, magnetically recoverable and low cost spinel CuFe2O4 nanoparticles. The catalyst was characterised using powder-XRD, FTIR, FE-SEM, EDX, VSM and HRTEM. The recyclability was examined and the results showed that the catalyst remained almost equally active up to five consecutive cycles. Spinel Structured Copper Ferrite is a very efficient nano catalyst for Oxidative decarboxylation of Phenyl acetic acids and can be reused up to five cycles without significant loss in catalytic activity.

Mechanical and durability properties of cementitious brick containing Nano Ferrite

This research investigates the influence of addition of Nano materials (Nano ferrite) on the physical and mechanical properties of the cementitious brick, by adding 1, 2, 3% of Nano ferrite by weight of cement. Bearing strength tests at RT and exposure to 100, 200, 300°C temperature after 4 hour, Bulk density and water absorption of resulting bricks were tested. Ni-Zn-Mg-ferrite nanoparticles were prepared using citrate auto combustion method using the X-Ray Diffraction (XRD) to characterize the prepared sample where found the particle size is (49.6 nm) with good crystalline structure. The results show that possibility to synthesize nanoparticles, the optimum content of the Nano ferrite was 2% that produces the ultimate increase in the bearing strength and improvement in physical properties. The mechanical test results showed a tendency to lose strength at high temperature. It was found that a decrease in the water absorption from 4.913 to 3.273 wt % occurred at 3% of Nano ferrite.

Nano ferrites (AFe2O4, A = Zn, Co, Mn, Cu) as efficient catalysts for catalytic ozonation of toluene.

Nano ferrites (AFe2O4, A = Zn, Co, Mn, Cu) were supported on the surface of γ-Al2O3 support by hydrothermal synthesis to prepare a series of novel composite catalysts (AFe2O4/γ-Al2O3) for catalytic ozonation for elimination of high concentration toluene at ambient temperature. The characterization results showed that the high-purity nano-AFe2O4 particles were uniformly loaded on mesoporous γ-Al2O3. Further, it was confirmed that among the several catalysts prepared, the amount of oxygen vacancies (Ovs), Lewis acid sites (LAS), and Brønsted acid sites (BAS) of the ZnFe2O4/γ-Al2O3 catalyst were the highest. This meant that the ZnFe2O4/γ-Al2O3 catalyst had a strong adsorption capacity for toluene and ozone (O3), and had a strong catalytic activity. When the temperature was 293 K and the space velocity was 1500 h−1, the mol ratio of O3 to toluene was 6, the degradation rate of toluene (600 mg m−3) can reach an optimum of 99.8%. The results of electron paramagnetic resonance (EPR) and Fourier infrared (FT-IR) proved superoxide radicals and hydroxyl radicals by catalytic ozonation. Moreover, the GC-MS analysis results indicated that the toluene degradation began with the oxidation of methyl groups on the benzene ring, eventually producing CO2 and H2O. After repeated experiments, the toluene degradation rate remained stable, and the residual content of O3 in each litre of produced gas was less than 1 mg L−1, thereby indicating that the ZnFe2O4/γ-Al2O3 catalyst had excellent reusability and showed great potential for the treatment of toluene waste gas.

Ni addition induced modification of structural, magnetic properties and bandgap of Ni-Zn nano ferrites

We report synthesis, characterization of Zn1-xNixFe2O4 (x = 0.0–1.0) nano ferrites, by using x-ray diffraction 'XRD', vibration sample magnetometery, UV–Vis spectroscopy. XRD validates the formation of fcc spinel structure. Ni-addition leads to: grain diameter modification; linear decrease of lattice parameter; un-equal distribution of both Ni2+, Zn2+, Fe3+ ions on A, B sites; changes in the degree of inversion, and oxygen parameter showing changes in disorder; linear variation of bandgap; significant reduction of coercivity with simultaneous increase of saturation magnetization. Results clearly demonstrate that Ni-addition in Ni-Zn ferrite can be effectively used to tune magnetic properties, bandgap.

Composition assisted tuning properties of CoCrxFe2-xO4 spinel nano ferrites

Structural, magnetic properties, bandgap of sol gel auto-combustion synthesized single phase CoCrxFe2-xO4 (x = 0.0–1.0) nano ferrites, were studied by x-ray diffraction, vibration sample magnetometer, ultra violet visible spectroscopy. Linear decrease of lattice parameter with increasing Cr-content is ascribed to difference between ionic radii of Cr3+ (0.064 nm), Fe3+ (0.067 nm). Linear decrease of grain diameter with increasing Cr-content, shows presence of Cr in spinel lattice which hinders grain growth. Results show bandgap tenability; reveal that Cr-addition is effective in determining coercivity, saturation magnetization of studied samples. Results illustrate effectiveness of compositional variation for structural modification, leads to tuning of magnetic properties, bandgap.

Influence of silver doping on the structural properties of magnesium ferrite nanoparticles and its possible antibacterial activity

An investigation on the effect of doping silver in magnesium ferrite is presented. AgXMg 1-X Fe2O4with x = 0, 0.025 and 0.05 were prepared using sol–gel method. The resulting ferrites were calcined at 700 °C. XRD profile indicates the effect of doping concentration on crystallite size of samples. The IR spectra reveal two main absorption bands, the high frequency band ν1 around 600 cm−1 and the low frequency band ν2 around 400 cm−1 arising from stretching vibrations of the oxygen bond with the metal in the tetrahedral (A) and octahedral (B) sites in the spinel lattice. Antibacterial studies of Ag0.025Mg0.975Fe2O4 shows magnesium ferrite as a positive candidate for different bacteria. The results underline the effect of doping concentration of Ag on the morphology and crystallite size of Nano ferrites.

Inter-digital capacitive ethanol sensor coated with cobalt ferrite nano composite as gas sensing material

Sensor design for environmental pollution monitoring is a great challenge, as the selectivity and sensitivity of the sensor for a desired pollutant gas should be high enough to be detected at low concentrations. This work presents an ethanol gas sensor using inter-digital capacitive (IDC) structure coated with Cobalt ferrite (CoFe2O4) nanocomposite as gas sensing material. CoFe2O4 nanocomposite are prepared by sol gel auto-combustion method. Gas sensing properties of the IDC structure are investigated under various gas concentrations. The sensor exhibits high sensitivity of the order of 100 nF/ppm with a response of 1.4% for ethanol gas at room temperature with a very low gas concentration of 7 ppm, compared to 0.4% and 0.2% respectively for methanol and acetone vapors. The response and recovery times of the sensor are about 180 s. The superior activity of the sensor indicates possible industrial and commercial applications.

Facile and eco-friendly route for green synthesis of magnesium ferrite nano particles

Magnesium ferrite (MgFe2O4) nano-particles were synthesized by using both the ceramic method and egg white assisted green synthesis method. The ceramic method carried out at different temperatures while the combustion method achieved at 300 oC for quarter-hour with various amounts of egg white. The green synthesis method was found to be a simple and cost-effective method compared to the ceramic method. Significant effects of the calcination temperatures and concentration of egg white on the observed phases, sizes, lattice parameters and morphological properties of the as-synthesized nanoparticles have been studied. Investigation of the structural and morphological characteristics of the as prepared samples was determined by XRD and SEM techniques, respectively. However, the relative atomic abundance of Mg, Fe and oxygen species present in various solids were determined by the EDX technique. The results display the nanometer size and partially inverse spinel structure of MgFe2O4 studied.

Nitric acid assisted sol-gel synthesis of cobalt ferrite nano particles

Mono-phase cobalt ferrite nanoparticles possessing excellent magnetostrictive properties having the composition CoFe2O4 was synthesized employing sol gel technique with an acid catalyst. The acidic environment was facilitated using nitric acid. The dried gel was calcined at about 800 °C and the phase formation for the same was studied using X-ray diffraction (XRD). The calcined powder was further analyzed with Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Band gap for the ceramic sample was calculated using UV-visible spectroscopy.

Synthesis and Characterization of Copper Doped Lithium Ferrite Nanocomposite

In this paper copper doped lithium ferrite nanoparticles effectively synthesized using sol-gel technique. The synthesized product was analyzed by using TG/DTA, XRD, FT-IR, FE-SEM, HR-TEM, VSM and CV studies. TG/DTA study indicates that the thermal stable of the prepared copper doped lithium ferrite nanoparticles. XRD result confirms that copper doped lithium ferrite nanoparticles have development of cubic phase with Fd3m group and also average crystallite size calculated for different ratios using Scherrer’s formula around 40 nm. FT-IR spectra confirm the presence of absorption band of lower frequency (ν2) at octahedral site and higher frequency (ν1) at tetrahedral site of prepared nanocomposites. The FE-SEM image of CuxLi1-xFe2O4 (x=0.2) nanocomposites clearly specifies that the spherical morphology with agglomerated particles and the same is confirmed by HR-TEM study. The EDAX analysis showed that the existence of Cu, Fe and O elements. VSM study reveals that copper doped lithium ferrite nanoparticles are paramagnetic in nature. Copper doped lithium ferrite nano composites exhibits the higher specific capacitance value at 587 Fg-1 for 10 mVs-1 studied from CV.

Investigation on Elastic, Magnetic, Optical and Electrical Impedance Properties of Dysprosium Doped Nickel Ferrite Nanocrystals.

Rare earth dysprosium (Dy) doped nickel ferrite nanoparticles were synthesized via economically viable co-precipitation technique and studied for its elastic, structural, magnetic and electrical properties. X-ray diffraction analysis shows the formation of cubic spinel phase with a slight inclination in the cell parameters with respect to the concentration of dopant convivial. The crystallite size and strain of the nanoparticles were determined using Scherrer formula and the Williamson-Hall (W-H) technique. In addition, the theoretical parameters viz., cation distribution, bond length, oxygen positional parameters, etc., have been embrasured. The strength and types of interionic bonds in the nano ferrites were determined utilizing Fourier Transform Infrared spectral analysis. The magnetic properties were analysed using vibrating sample magnetometer at room temperature, it was found that as the dopant concentration increases, the coercivity and magnetic saturation decreases. This result is partially explained by the bridge networking of Dy3+-Fe3+ ions which is equated by Fe2+- Fe3+ ion interaction. This paper deals with the itinerant electron model to determine the distribution of cations by magnetization analysis. The optical properties of the samples were studied utilizing UV-Vis spectral analysis and the optical band gap was evaluated from Kubelka-Munk plot. Electrical impedance was analysed as a function of frequencies at room temperature. This analysis depicts the dielectric constant and loss factor tends to decline with applied frequency and AC conductivity elicits its semiconducting characteristic by obeying Jonscher's law.

A high performance recyclable magnetic CuFe2O4 nanocatalyst for facile reduction of 4-nitrophenol

In this study we have synthesized copper ferrite magnetic nanoparticles, a transition metal based material by wet chemical method. The nanoparticles are mesoporous in nature and have shown very good catalytic property in reduction of 4-nitro phenol (4-NP) to 4-amino phenol (4-AP) with high rate constant and low activation energy value. Detailed characterization of the nanoparticles was done using XRD, EDAX, FTIR, FESEM, TEM, HRTEM, SAED, BET, VSM and TG/DTA to confirm its structural, morphological, magnetic and thermal properties. We have shown the reduction of 4-NP to 4-AP by a non-functionalized copper ferrite nano catalyst (CFNC), occurs at higher rate following first order reaction kinetics in respect of 4-NP, which indicates its high efficiency as catalyst compared to other catalyst. Because of its magnetic property, it can be easily separated from the reaction mixture by magnetic separation method after its use as catalyst. It is also shown; this catalyst can be reused many times without having any significant decay in its catalytic quality. From the applicative point of view, this catalyst may be useful in industrial application because of its high stability, greater catalytic efficiency and cost effectiveness.

Structural and Optical Properties of Cd1−xMnxFe2O4/PMMA Nanocomposites

Cd1−xMnxFe2O4/PMMA nanocomposites are prepared using hydrothermal and casting procedures. Rietveld analysis is performed for Cd1−xMnxFe2O4 (x = 0, 0.3, 0.5, 0.7) nano ferrite. X-ray diffraction and Fourier transform infrared are used to examine the homogenous distribution of Cd1−xMnxFe2O4 throughout PMMA matrix. The influence of nano ferrite on the absorbance, transmittance and refractive index for all samples are examined utilizing UV–Vis spectrophotometer technique. The direct energy gap and other optical parameters of nanocomposite samples are changed depending on the amount of manganese doped Cd-ferrite. All nanocomposite samples display four sub-emissions in UV and visible regions.

Dielectric, impedance, AC conductivity and low-temperature magnetic studies of Ce and Sm co-substituted nanocrystalline cobalt ferrite

Abstract In this study, we report frequency and temperature dependent dielectric, electrochemical impedance and low temperature magnetic properties of Sol-gel auto-combustion synthesized rare-earth (Ce and Sm) co-substituted cobalt ferrite, CoCexSmyFe2-x-yO4 (x = y = 0.00, 0.1, 0.12 and 0.25). The surface morphology and particle size as obtained by XRD studies was confirmed by HRTEM measurements for a representative sample. The dielectric properties such as dielectric constant, loss tangent and AC conductivity have been measured using LCR meter, variation of dielectric parameters with substituent concentrations, frequency range from 0.1 to 10 MHz at room temperature (RT) and temperatures 100–400 °C have been well supported by Maxwell-Wagner interfacial polarization. The AC conductivity increased with applied frequency suggesting that the conduction mechanism is owing to small polaron hopping between cations. Impedance studies shows that, the addition of RE (Ce and Sm) cause a decrease in the Z′ value, with increasing frequency which can be attributed to the space charge polarization effect in the material. Low temperature magnetic measurements in ZFC-FC mode and magnetic isotherms at 20 and 310 K reveals the ferromagnetic nature of RE (Ce, Sm) substituted cobalt ferrite nano particles. The coercive field has been increased at low temperature 20 K compared to that at 310 K, the samples shows super paramagnetism beyond room temperature.