Nano Ferrites Research Articles

Solvothermal synthesis of magnetic copper ferrite nano sheet and its antimicrobial studies

Carbon embedded magnetic ferrite materials are highly active, stable and being widely used in catalysis and pollution control. The carbon containing magnetic copper ferrite was synthesised by solvothermal decomposition method using precursor derived from e-waste. The prepared material was characterized by PXRD, FE-SEM, TEM, Raman, FT-IR, XPS, and NH3-TPD. During the solvothermal decomposition of Fe3(OCH3CH3COO)5·2CH3OH and Cu(CH3COO)2 in-situ generated CO2 would act as a reducing agent for M+3 to M+2 ions reduction and can also be used as carbon source. The as-synthesised copper ferrite (C@CF) was calcined at 400 °C was designated as CF. Both the materials were tested for antimicrobial activity against environmental microorganisms B. subtilis (gram positive, rod shaped) and P. aeruginosa (gram negative, rod shaped) at three exposure concentrations 50, 100 and 200 μg/ml. The possible mechanistic aspects of the antimicrobial actions for CF and C@CF was studied by reactive oxygen species generation and cell membrane permeability assays. C@CF nanoparticles consistently showed significantly higher cytotoxic effects against the test species compared to the CF particles, and this was strongly corroborated by the reactive oxygen species generation and the cell membrane damage results.

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.

Structural and physical property study of sol–gel synthesized CoFe2−xHoxO4 nano ferrites

CoFe2-xHoxO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20) ferrites were prepared by the suitably modified Sol-Gel technique. X-ray diffraction (XRD) analysis revealed that the substituted samples show phase pure formation till 10% substitution, which is far higher phase pure than the earlier reports. Upon further substitution an inevitable secondary phase of HoFeO3 along with the spinel phase despite regulating synthesis parameters in the sol-gel reaction route. These results are further corroborated more convincingly by room temperature neutron diffraction. Morphological features of the ferrites were studied by Scanning Electron Microscopy (SEM). The magnetic parameters viz. the saturation magnetization (Ms), coercivity (Hc) and remanence (Mr) were determined from room temperature isothermal magnetization. These parameters were found to decrease with increase in Ho substitution. The decrease in magnetization is analyzed in the light of exchange interactions between rare earth and transition metal ions. Magnetostriction measurements revealed interesting results and the presence of a secondary phase was found to be responsible for decreased measu-red magnetostriction values. The solubility limit of Ho in CoFe2O4 lattice is also reflected from the X-ray and neutron diffraction analysis and magnetostriction studies.

A Comparative Study of Physical Properties of Er and Yb Nanophase Ferrite for Industrial Application

Nano ferrites CuCr0.3Er0.03Fe1.67O4 and CuCr0.3Yb0.03Fe1.67O4 were synthesized using standard ceramic technique. X-ray diffraction (XRD) patterns confirmed that the samples had cubic spinel structures. The average crystallite sizes of Er and Yb samples were in the range of 104.2–100 nm. The morphology analyses using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) confirmed that the samples were in the nanoscale range. The compositional analyses using energy-dispersive x-ray (EDX) showed the atomic percentage (at.%) and weight percentage (wt%) of the investigated samples. The magnetic properties were carried out at room (300 K) and at low (100 K) temperatures magnetic hysteresis loop. The data showed that Er sample had higher saturation magnetization (Ms) and lower coercivity (Hc) than that of Yb sample suggesting that Er sample can be applied in magnetic applications. Moreover, Er sample had higher dielectric constant (e’), dielectric loss (e”) and dielectric loss tangent (tan δ) than that of Yb sample. However, Yb sample had higher resistivity than that of Er sample suggesting that Yb sample can be applied in electrical applications.

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.

Tổng hợp vật liệu cấu trúc spinel nickel ferrite NIxFE3-xO4 bằng phương pháp sol-gel và khảo sát hoạt tính quang xúc tác

Nano ferrite has been published by many previous studies because of its important properties such as magnetic materials and catalysts. In this study, nickel ferrite (NixFe3-xO4) was prepared by sol-gel method with ethylenediaminetetraacetic acid (EDTA) as complex agent. The effect of parametters on material structure and properties were investigated such as EDTA (in acid and salt of sodium compounds), calcination temperature, calcination time, the molar ratio of nickel/iron. The XRD results showed that with calcination temperature higher 600 oC the product was formed with spinel structure and single phase. The product had narrow band gap value, about 1.52 eV. Its photocatalytic in wave lenght of visible light range was investigated with methylene blue solution at wave length of 578 nm and the decompositional yield about 83.4%.

Phase transformation in white etching area in rolling contact fatigue

Rolling contact fatigue (RCF) involves microstructural change in the subsurface of contact. The changed microstructure is generally termed as white etching area (WEA) as it appears white under optical microscope when etching in nital solution. WEA has been acknowledged as one of the primary failure modes in RCF since it causes severe local inhomogeneity of microstructure. It was reported that WEA consists of nano ferrites as martensite grains and carbides are significantly refined in the WEA. Some carbides are dissolved. In some cases, an amorphous-like structure was occasionally observed in the WEA, indicating that phase transformation may possibly occur. The WEAs were studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Electron back scattered diffraction (EBSD). The result showed that WEA is dominated with an amorphous phase with martensite, austenite and carbides embedded interior. A distinct interface between the matrix and the WEA was present. In addition to grain refinement down to nanometers, phase transformation including amorphization and austenitization happened in WEAs. The content of austenite was increased from 2% in the matrix to 20% in the WEA. The analysis showed that phase transformation is controlled by plastic deformation mechanism.

Structural Analysis of Nano Ferrites Synthesized by Combustion and Microwave Methods

We suggest a new approach to synthesis of nano nickel ferrites via combustion synthesis in electric and microwave ovens. The oxidation of organic compounds, decomposition of salts, and their degradation were explored by TGA–DTA. As-prepared nanopowders were characterized by X-ray powder diffraction. Structures of both ferrites were slightly different. Detailed material parameters such as crystallite size (D), lattice constant (a), micro strain (e), X-ray density (ΔX), dislocation density (ρX), hopping lengths (LA and LB), bond lengths (A–O and B–O), ionic radii (rA and rB), texture coefficient [TC(hkl)], and mechanical properties were measured and comparatively analyzed.

Structural, Morphological and Temperature Dependent Dielectric Studies of Sr-Cu Nano Sized Hexa Ferrites

A series of polycrystalline SrCu nano ferrites substituted with Sn-Co having generic formula Sr2Cu2Fe12-X(SnCo)X/2O22 (where x changes from 0 to 2.5 in equal steps of 0.5) have been synthesized by novel microwave assisted sol gel process using urea as fuel. Structural characterization of the prepared compounds have been performed using X-ray powder diffraction pattern, which shows formation of single Y-type hexagonal phase and belonging to space group R3-m(no.166). The lattice parameters, X-ray density (Dx), measured density (Dm), and porosity (P) of samples are calculeted from XRD data. We observed that the lattice parameters “a” and “c” increasewith content of SnCo. The crystallite size is in the range 13- 47nm, shows nanometer size of prepared compounds. The microstructure is studied by transmission electron microscopy (TEM).The ac electrical conductivity (σac) dielectric constant (∊’), and dielectric loss (tan δ) are studied a function of temperature. The plot of conductivity verses 1/T shows semiconducting nature of the compounds. The results of dielectric constant and dielectric loss are explained on the basis of the assumption that the mechanism of dielectric polarization is similar to that of conduction process.

Dielectric properties of Chromium substituted Nickel nano ferrites

Background The powders of Ni-Cr Nano ferrites were synthesized with the chemical formula, NiCrXFe2−XO4 (Where X = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) by using citrate-gel auto combustion technique. The structural characterization was investigated by X-Ray Diffractomerter (XRD). X-ray analysis shows that the samples are cubic spinel structure (single phase) without any impurity peak and average crystallite size was in the range of 8.5-10.5nm. The dielectric measurements were carried out as a function of frequency and composition (X) at room temperature in the range of 20Hz-2MHz. The real part of dielectric constant (e’) and dielectric loss factor (tan δ) showed a decreasing trend with increasing field frequency. The ac conductivity (σac) is calculated from the dielectric measurements and it is increased with the increase of frequency. The composition dependent dielectric parameters are reported.

Mechanical and Solvent Transport Properties of Nickel Ferrite Embedded Natural Rubber Nanocomposites

In the present scenario nanocomposites centered on rubber matrices and modified fillers exemplify a remarkable opening for the proposal of high characteristic materials especially from the mechanical properties and solvent permeability points of view. Natural rubber composites with nickel ferrite nano fillers are prepared at various loadings. Nickel ferrite was synthesized using a very unique co-precipitation method using sodium hydroxide as the precipitating agent. The prepared fillers were incorporated into natural rubber matrix at 5, 15, 25, 50 and 75 phr (parts per hundred rubber) loading. The rubber mixes were vulcanized for corresponding cure time and the obtained rubber sheets were analyzed for mechanical and solvent penetration behavior.

Impact of Gd3+/graphene substitution on the physical properties of magnesium ferrite nanocomposites

Magnesium nano ferrite with composition MgFe2O4, MgGd0.05Fe1.95O4 and MgFe2O4 – 5 wt% GO was synthesized using a citrate auto-combustion method. The crystal structure, morphology, and magnetic properties of the investigated samples were studied. High Resolution Transmission Electron Microscopy (HRTEM) images show that the substitution of small amounts of Gd3+/GO causes a considerable reduction of the grain size. Studies on the magnetic properties demonstrate that the coercivity of GO-substituted magnesium nano ferrites is enhanced from 72 Oe to 203 Oe and the magnetocrystalline anisotropy constant increases from 1171 to 3425 emu Oe/gm at 300 K. The direct effects of graphene on morphology, crystal structure as well as the magnetic properties reveal that the studied sample are suitable for turbidity color and removal. The magnetic entropy change is estimated from magnetization data using Maxwell relation. The calculated Curie temperature from the Curie-Weiss law and the maximum entropy change are in good agreement with each other. Based on UV diffuse reflectance spectroscopy studies, the optical band gaps are in the range of 1.4–2.15 eV. In addition, the combination of small particle size and good magnetic properties makes the investigated samples act as a potential candidates for superior catalysts, adsorbents, and electromagnetic wave absorbers.

Preparation and Characterization of Chromium Doped Ni-Cu-Zn Nano Ferrites.

Chromium doped Ni-Cu-Zn nano ferrites with chemical formula Ni0.2Cu0.2Zn0.6Fe2-xCrxO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by using sol-gel auto combustion method. The prepared precursors of Chromium substituted Ni-Cu-Zn ferrites were sintered at 500 °C for 4h. Compositional stoichiometry were confirmed from EDAX patterns. The XRD data revealed that the all samples possess a single phase cubic spinel structure. The Lattice constant, X-ray density, hopping lengths and crystallite size determined from XRD data decreases with increase in Cr3+ concentration. The IR spectra show two major absorption bands, high frequency band ν1 ≈ 600 cm-1 and low frequency band ν2 ≈ 450 cm-1 attributed to the stretching vibration of tetrahedral and octahedral sites respectively. The surface morphology of the prepared samples was studied by Scanning Electron Microscopy and Transmission Electron Morphology.

Investigation of structural, optical, magnetic and electrical properties of tungsten doped Ni[sbnd]Zn nano-ferrites

Tungsten substituted nickel-zinc ferrite nanoparticles with chemical composition of Ni0.5Zn0.5WxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 & 1.0) were successfully synthesized by a chemical co-precipitation method. The prepared ferrites were pre sintered at 850 °C and then annealed at 1000 °C in a muffle furnace for 3 h each. This sintered powder was inspected by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM) to study the structural, optical, and magnetic properties. XRD measurement revealed the phase purity of all the nanoferrite samples with cubic spinel structure. The estimated crystallite size by X-ray line broadening is found in the range of 49–62 nm. FTIR spectra of all the samples have observed two prominent absorption bands in the range 400–700 cm−1 arising due to tetrahedral and octahedral stretching vibrations. Vibrating sample magnetometer experiments showed that the saturation magnetizations (MS) decreased with an increase in non-magnetic tungsten ion doping. The electrical resistivity of tungsten doped NiZn nano ferrites were examined extensively as a function of temperature. With an increase in tungsten composition, resistivity was found to decrease from 2.2 × 105 Ω cm to 1.9 × 105 Ω cm which indicates the semiconducting behavior of the ferrite samples. The activation energy also decreased from 0.0264 to 0.0221 eV at x = 0.0 to x = 1.0. These low coercive field tungsten doped NiZn ferrites are suitable for hyperthermia and sensor applications. These observations are explained in detail on the basis of various models and theories.

Comparative study of synthesis, structural and magnetic properties of Cu2+ substituted Co-Ni, Co-Zn and Co-Mg nano ferrites

Mixed ferrites of the form Co0.5M0.1Cu0.4Fe2O4 (M = Ni, Zn and Mg) have been synthesized using the sol-gel auto combustion technique. Structural analyses are carried out using powder X-ray diffraction to idntify pure ferrite phases. SEM analysis revealed clear crystal morphology with relatively uniform grain sizes with polygonal structures. The FT-IR studies also confirm the bond formation and cation vibrations at low (365–392 cm−1) and high (579–587 cm−1) bands that correspond to the tetrahedral and octahedral sites, respectively. The magnetic properties studied through vibrating sample magnetometer showed that the Ni substituted sample has more magnetic character by exhibiting the highest saturation magnetization.

Self-propagation combustion method for the synthesis of solar active Nano Ferrite for Cr(VI) reduction in aqua system

Abstract The study aimed at the development of a facile route to the synthesis of a solar active nano ferrite via the self-propagation combustion protocol. The solar activity of the synthesised ferrite sample (FSP) was determined using the reduction of Cr(VI) to Cr(III) as a case study, in the presence of oxalic acid, as the hole scavenger. The analysis of the time-concentration profile data of the photoreduction reaction with the pseudo first order kinetic equation showed that the rate and half-life (t1/2) of photoreduction of Cr(VI) to Cr(III) is dependent on the initial Cr(VI) concentration. The photoreduction efficiency (PE) (%) of the FSP is a function of the initial FSP dosage and the hole scavenger. The determination of the influence of hydrochemistry on the PE (%) showed that Cr(VI) solution pH and ionic strength had no visible negative impact. Aside the presence of carbonate in the Cr(VI) solution, other anionic interfering species (i.e. NO−3, Cl− and SO3 2−) had minimal or no visible influence on the PE (%) values. The presence of carbonate, at higher concentration (i.e. ˃10 mg/L) significantly impacted on the PE values and hyperchromic shift in the absorbance values of the treated water from the photo reduction process was observed. The tendency of the Cr(III) that is formed from the photoreduction reaction to form Cr(III)-oxalato complex was confirmed after a certain minimum time of the photoreduction process.

Structural and temperature dependent dielectric behavior of Cr and Zn doped MnFe2O4 nano ferrites

The Mn0.5Zn0.5Fe2O4 and Mn0.5Cr0.5Fe2O4 ferrites were synthesized by low temperature sol gel auto combustion method. The laboratory and Synchrotron x-ray diffraction confirms the formation of face centered cubic structure with Fd-3m space group. Particle sizes as calculated from Synchrotron (laboratory) source discern decreasing value 14.85 (15.17) nm in Mn0.5Zn0.5Fe2O4 ferrites, however an enhanced particle size of 27.67 (19.88) nm is seen for Mn0.5Cr0.5Fe2O4. The dielectric constant (dielectric loss) is 400 (7.88) for Mn0.5Zn0.5Fe2O4 and 1.1 × 104 (0.6) for Mn0.5Cr0.5Fe2O4 ferrites at 300 K and at 100 Hz and found to have increasing value with temperature and frequency. The increase in the value of ac conductivity is also observed with the increase in temperature and frequency. The activation energy for Mn0.5Zn0.5Fe2O4 (Mn0.5Cr0.5Fe2O4) ferrite is 0.42 (0.44) eV at 100 Hz and 0.22 (0.23) eV at 1 MHz, respectively. These observations indicate that Cr doping is more useful in device application as compared to Zn in MnFe2O4.

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.