Nickel Ferrite Spinel Research Articles

Synthesis of rod-shaped NiFe 2O 4 spinel ferrites by the precipitation–toptactic reaction and investigation of magnetic properties

The rod-shaped NiFe 2O 4 spinel ferrites were synthesized by the precipitation–toptactic reaction method using pod-like γ-FeOOH as raw materials. The synthesis processes of rod-shaped NiFe 2O 4 spinel ferrites include preparation of the rod-shaped precursor with a length-diameter ratio of 12 ∼ 13, in which the pod-like γ-FeOOH is coated by poor-crystalline Ni(OH) 2 clusters, formations of γ-Fe 2O 3 and NiO through dehydroxylation of pod-like γ-FeOOH and decomposition of Ni(OH) 2, and production of NiFe 2O 4 during the whole calcination. An endothermic decomposition of Ni(OH) 2 at 280 °C ∼ 380 °C blocks the transition of γ-Fe 2O 3 into α-Fe 2O 3 so that NiO reacts directly with γ-Fe 2O 3 to produce NiFe 2O 4. The final product calcinated at 900 °C, uniformly in rod-like shape with a length-diameter ratio of 5 ∼ 8, smaller than that of the as-received precursor, present a higher coercivity than that of spinel nickel ferrites in irregular shape, which may be attributed to its strong shape anisotropy.

Electrical conductivity and molten salt corrosion behavior of spinel nickel ferrite

Nickel ferrite was prepared by solid-state reaction at 1300 °C as inert anode for aluminum electrolysis. DC conductivities and molten salt corrosion behavior of the samples were investigated in detail regarding the effects of different sintering atmospheres. X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis were used to analyse the phase compositions and microstructures. The DC conductivities of the samples sintered in nitrogen showed a drastic increase compared to those sintered in air, and at 960 °C they increased from 1.94 S/cm to 22.65 S/cm. The samples sintered in nitrogen showed much better corrosion resistance than those sintered in air, attributing to the formation of the dense protective layers in the anode surfaces during the electrolysis at 960 °C. The conductive mechanism and molten salt corrosion behavior were also discussed.

Study on the Characteristic and Effect of the Nickel Ferrite Spinel Cermet as Al Electrolysis Inert Anode

Inert anode or non-consume anode possesses more advantages than traditional carbon anode in Al electrolysis. Because it does not consume during electrolysis, the inert anode can maintain its dimension; and this will led to the Al electrolysis easy to operate and administrate. Especially, the inert anode does not emit the carbon dioxide during the Al production, owing to its not consuming, and this has made the inert anode become one of the highlights in Al electrolysis industry. Unfortunately, up till now, there is no any material can endure the erosion of cryolite molten salt, keep its good electrolytic conductivity and be agreeable in price. In this paper, a cermet material composed of 85% nickel ferrite spinel and 15% metallic Ag has been studied, aim at exploring a kind of material which can be used as Al electrolysis inert anode. The works mainly focus on improving the boundary and microstructure between the metallic Ag and the nickel ferrite spinel interface. The practice test of this cermet material being used as Al electrolysis anode has been done in small laboratory scale, and its effect is quite better. We can draw the conclusion that the characteristic such as the conductivity, corrosion resistance and hot shock property of the cermet material can be greatly improved to meet the requirement of Al electrolysis by means of optimizing the spinel/metal interface, and once we settle the technique of fabricating this kind of anode to enough dimension, can we use this kind of material as inert anode in Al electrolysis industry to reduce the gas emission of carbon dioxide.

Combustion synthesis and characterization of highly crystalline single phase nickel ferrite nanoparticles

A combustion route of synthesizing highly crystalline single phase nickel ferrite (NiFe 2O 4) spinel nanoparticles using various amounts of dl-alanine as fuel has been reported in this paper. The role of the amount of fuel is found to be significant in the size control and phase purity of nano crystalline samples. The structural, thermal, morphological and magnetic studies have been carried out. XRD patterns reveal the formation of highly crystalline nano NiFe 2O 4 with high degree of phase purity when fuel concentration is maintained at 1 M and 2 M. FTIR spectra also prove the formation of pure nano NiFe 2O 4. The temperature and fuel effects are found to have strong influence on size, structural, and magnetic properties of materials. The magnetic measurements show that the nano NiFe 2O 4 samples exhibit soft ferromagnetism with the highest saturation magnetization Ms at room temperature as 42.53 emu/g.

Synthesis, structural and electrical characterization of Sb 3+ substituted spinel nickel ferrite (NiSb xFe 2− xO 4) nanoparticles by reverse micelle technique

Spinel nickel ferrite with nominal composition NiFe 2− x Sb x O 4 (where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1) has been synthesized by the reverse microemulsion method. The samples synthesized were characterized by XRD, FTIR, TGA/DTGA, SEM, AFM, Mossbauer Spectroscopy and DC electrical resistivity measurements. The XRD analysis confirmed the formation of single spinel phase and the crystallite size was found to be in the range of 8–38 nm. The particle size of the synthesized samples was also confirmed by the AFM and SEM which was found in the range of 5–45 nm and 10–45 nm, respectively and this size is small enough for obtaining the suitable signal-to-noise ratio in high density recording media. The Mossbauer spectra of samples showed two well-resolved Zeeman patterns corresponding to A and B sites and also observed a doublet at higher substitution. The DC electrical resistivity showed an interesting behavior with temperature and observed a metal-to-semiconductor transition temperature ( T M–S) which suggests that the material can be applied for switching applications. The resistivity increases with the increase in Sb-content and it suggests that the material can be fruitfully used for applications in microwave devices.

A Structural and Magnetic Investigation of the Inversion Degree in Ferrite Nanocrystals MFe2O4(M = Mn, Co, Ni)

The structural and magnetic properties of nanocrystalline manganese, cobalt, and nickel spinel ferrites dispersed in a highly porous SiO2 aerogel matrix were studied. X-ray diffraction and high-resolution transmission electron microscopy indicate that single crystalline ferrite nanoparticles are well dispersed in the amorphous matrix. The cation distribution between the octahedral and tetrahedral sites of the spinel structure was investigated by X-ray absorption spectroscopy. The analysis of both the X-ray absorption near edge structure and the extended X-ray absorption fine structure indicates that the degree of inversion of the spinel structure increases in the series Mn, Co, and Ni spinel, in accordance with the values commonly found in the corresponding bulk spinels. In particular, fitting of the EXAFS data indicates that the degree of inversion in nanosized ferrites is 0.20 for MnFe2O4, 0.68 for CoFe2O4, and 1.00 for NiFe2O4. Magnetic characterization further supports these findings.

Conductivity and dielectric studies of copper–aluminate substituted spinel nickel ferrite

Abstract Effect of Cu substitution in the spinel ferrite Ni 1− x Cu x Al 0.6 Fe 1.4 O 4 (0.0 ≤ x ≤ 1.0) in steps of 0.25 has been studied. Electrical measurements in the frequency range 10 2 –10 5 Hz and at temperature between 300 and 600 K show that these materials have a semiconductor-to-metallic transition as copper content increases. All studied compositions exhibit a transition with a change in the slope of the conductivity versus temperature curve. Dielectric parameters of these materials were studied as a function of frequency and temperature, where the dielectric permittivities ( ɛ ′, ɛ ″) revealed a dielectric anomaly at the transition temperature T c . The obtained T c is found to decrease with increasing Cu concentration. Relaxation spectrum was obtained in the relation of dielectric loss tangent (tan δ ) with frequency for sample with ( x = 0.5) where relaxation time τ and the maximum frequency ν ∞ of the hopping conduction mechanism is obtained. The variation of ( ɛ ′, ɛ ″ and tan δ ) with frequency and temperature displays a strong dependence on both nickel and copper concentrations. The results are explained in light of the cation–anion–cation and cation–cation interactions over the octahedral site in the spinel structure.

Chemical synthesis of spinel nickel ferrite (NiFe 2O 4) nano-sheets

The present investigation is related to the deposition of single-phase nano-sheets spinel nickel ferrite (NiFe 2O 4) thin films onto glass substrates using a chemical method. Nano-sheets nickel ferrite films were deposited from an alkaline bath containing Ni 2+ and Fe 2+ ions. The films were characterized for their structural, surface morphological and electrical properties by means of X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and two-point probe electrical resistivity techniques. The X-ray diffraction pattern showed that NiFe 2O 4 nano-sheets are oriented along (3 1 1) plane. The FT-IR spectra of NiFe 2O 4 films showed strong absorption peaks around 600 and 400 cm −1 which are typical for cubic spinel crystal structure. Microstructural study of NiFe 2O 4 film revealed nano-sheet like morphology with average sheet thickness of 30 nm. The room temperature electrical resistivity of the NiFe 2O 4 nano-sheets was 10 7 Ω cm.

Ultrasonic Nozzle Spray in Situ Mixing and Microwave-Assisted Preparation of Nanocrystalline Spinel Metal Oxides: Nickel Ferrite and Zinc Aluminate

Nanocrystalline spinel nickel ferrite and zinc aluminate particles (6−20 nm) can be prepared by a recently developed continuous flow method that combines microwave heating and in situ ultrasonic nozzle spray mixing. The preparations were carried out at ambient pressure (1 atm), microwave power (0−600 W), and ultrasonic nozzle with resonant frequency of 48 or 120 kHz. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microcopy, X-ray electron dispersive spectroscopy, Brunauer−Emmett−Teller spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and temperature-programmed desorption mass spectrometry. The results showed that the ultrasonic nozzle and microwave irradiation complement each other, with respect to the purity of the products. The specific advantages of INM method for the preparing nickel ferrites are that pure materials with high surface areas and tunable particle sizes are produ...

Frequency dependence of the magnetoelectric effect in ceramic composites based on lead zirconate titanate and nickel ferrite

The magnetoelectric (ME) effect in ferrite-piezoelectric ceramic composites based on a nickel ferrite spinel and lead zirconate titanate (PZT) has been theoretically and experimentally studied. Using the method of effective medium, an expression for the ME coefficient is obtained and its frequency dependence is analyzed. It is shown that, in the region of electromechanical resonance, the magnitude of the ME effect exceeds that in a layered structure of the same components and is more than two orders of magnitude greater than the low-frequency value. The results of calculations for a nickel ferrite spinel-PZT composite are in good agreement with the experimental data.

CoFe 2O 4 and NiFe 2O 4 synthesized by sol–gel procedures for their use as anode materials for Li ion batteries

Cobalt and nickel spinel ferrites with CoFe 2O 4 and NiFe 2O 4 stoichiometries have been prepared by a sol–gel process based on a vacuum sublimation of a citrate precursor. Several samples of CoFe 2O 4 were obtained by varying the conditions of citrate precursor formation and further annealing. SEM images demonstrated the strong influence of synthesis parameters on the morphologies of secondary and primary particles. The formation of layered flake-like aggregates defining a macroporous system is assumed to improve the electrolyte–electrode contact in iron-containing samples. An enhanced electrochemical performance was achieved for samples annealed at high temperatures, especially for CoFe 2O 4 heated at 1000 °C for 24 h. Capacity values higher than 700 mAh g −1 was recorded after 75 cycles. 57Fe Mössbauer spectroscopy was used to clarify aspects of the mechanism of the electrochemical reaction.

Nickel Stabilization Efficiency of Aluminate and Ferrite Spinels and Their Leaching Behavior

Stabilization efficiencies of spinel-based construction ceramics incorporating simulated nickel-laden waste sludge were evaluated and the leaching behavior of products investigated. To simulate the process of immobilization, nickel oxide was mixed alternatively with gamma-alumina, kaolinite, and hematite. These tailoring precursors are commonly used to prepare construction ceramics in the building industry. After sintering from 600 to 1480 degrees C at 3 h, the nickel aluminate spinel (NiAl204) and the nickel ferrite spinel (NiFe204) crystallized with the ferrite spinel formation commencing about 200-300 degrees C lower than for the aluminate spinel. All the precursors showed high nickel incorporation efficiencies when sintered at temperatures greater than 1250 degrees C. Prolonged leach tests (up to 26 days) of product phases were carried out using a pH 2.9 acetic acid solution, and the spinel products were invariably superior to nickel oxide for immobilization over longer leaching periods. The leaching behavior of NiAl2O4 was consistent with congruent dissolution without significant reprecipitation, but for NiFe2O4, ferric hydroxide precipitation was evident. The major leaching reaction of sintered kaolinite-based products was the dissolution of cristobalite rather than NiAl2O4. This study demonstrated the feasibility of transforming nickel-laden sludge into spinel phases with the use of readily available and inexpensive ceramic raw materials, and the successful reduction of metal mobility under acidic environments.

Synthesis and magnetic characteristics of crystallized ceramic in the BaO–NiO–TiO 2–Fe 2O 3 system

Composite materials with mixed spinel nickel ferrite–barium titanate as co-existing phases have been synthesized using a conventional glass–ceramics route over a certain composition of the BaO–NiO–TiO 2–Fe 2O 3 system. The crystallographic phases present in the composition synthesized were mainly BaTiO 3 and NiFe 2O 3 using 2% boric acid flux while varieties of phases as NiFe 2O 4, Ba 1.12Ti 8O 16, BaTi 4O 9 and Ni 3(BO 3) 2 were observed using higher content of flux. Magnetic measurement of glasses crystallized at various time and temperature show that a ferromagnetic behavior is present that vary greatly as the flux content varies from 2% to 10%.A specific induction B s = 7.6 emu/g and a permeability of 4809 at applied field 5000 Oe was reached by crystallizing the parent material at 900 °C for 4 h. The variation of the magnetic properties of the composite materials as a function of added flux, particle sizes and microstructure of the samples were investigated.

Magnetic and Gas Sensing Property of Nanosized NiFe2O4 Powders Synthesized by Pulsed Wire Discharge

Nickel ferrite (NiFe2O4) powders were synthesized by pulsed wire discharge method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses show that only nickel ferrite spinel and no other phase was observed in the powders. Mean size of the obtained particles strongly depended on the oxygen pressure: the higher oxygen pressure corresponds to larger powder size, as determined by Brunauer–Emmet–Teller (BET). The room temperature saturation magnetization of the synthesized powders was 42–46 emu/g depending on the powder size. These powders also showed high chlorine sensitivity at about 280–360°C, and a good linear sensitivity with chlorine concentration.

Growth of nickel ferrite thin films using pulsed-laser deposition

Epitactic thin films of nickel ferrite spinel (NiFe 2O 4) have been grown on (0 0 0 1) oriented sapphire substrates using pulsed-laser deposition. Three different methods were used to produce the films. The first was direct deposition using a stoichiometric NiFe 2O 4 target. In the other two methods, a solid-state reaction between NiO and Fe 2O 3 was utilized to produce the spinel. In one case, the spinel was formed in situ while film growth occurred in the deposition system; in the other case, a NiO/Fe 2O 3 heterostructure was reacted ex situ at elevated temperatures in air. The resulting ferrite films were analyzed in cross section using both conventional and high-resolution transmission electron microscopy. In general, the predominant defects found in the spinel films were twin boundaries. However, the topology of the twin boundaries in each of the three films was different. These differences were attributed to, and correlated with, the growth method and reaction processes used to produce the spinel film.

Preparation of Ultrafine Nickel Ferrite Powders Using Mixed Ni and Fe Tartrates

Ultrafine nickel ferrite powders of 10 nm in particle size were prepared by the calcination of gel powders of coprecipitated Ni- and Fe-containing tartates at 250° to 400°C/2 h. The gel powder was a mixture of Ni and Fe tartrates exhibiting characteristics of the individual salts. The mixing homogeneity of the two salts strongly influenced the history of thermal reaction and the characteristics of the powder thus obtained. Both the formation temperature and the particle size increased with the retrograde of the mixing state, which initiated the increase in crystallite sizes of the intermediates, γ-Fe2O3 and NiO or Ni metal phases. Defect nickel ferrite spinel was formed if the oxygen fugacity was lower. Defect ferrites, especially those obtained at lower calcination temperatures, were highly susceptible to thermal decomposition at higher temperatures.

Semiconducting gas sensor for chlorine based on inverse spinel nickel ferrite

Nickel ferrite, a p-type semiconducting oxide with an inverse spinel structure has been used as a gas sensor to selectively detect chlorine in air. This compound was prepared by two different routes namely, the citrate and co-precipitation method and sensor properties of the resulting compounds from both the methods were compared. X-ray diffraction was used to confirm the structure. The gas sensing characteristics were obtained by measuring the sensitivity as a function of various controlling factors like dopant, concentration of the dopant, operating temperature, concentration of the gas and finally the response time. The sensitivity to chlorine has been compared with that of other interfering gases. A probable explanation has been proposed to explain the selective sensitivity to oxidising gases like chlorine.

Catalytic properties of some mixed transition-metal oxides

The effect of preparation procedure of some mixed transition-metal oxides on their catalytic properties has been investigated. The catalytic activity of the oxides, attributed to their n- or p-semiconductive character, was also studied with regard to the reaction of thermal decomposition of potassium and sodium chlorates and perchlorates. The oxides studied were the nickel spinel ferrites and the erbium-iron garnets and perovskites (orthoferrites) and it was found that catalytic activity depends on their preparation procedure. Materials mainly consisting of the spinel or perovskite and garnet phases, present increased catalytic activity.

Passivity, pitting and corrosion of anodically polarized Fe-Ni alloys in 0.5 M H2SO4 containing Cl?

Iron-nickel alloys containing 0, 20, 40, 60, 80 and 100% Ni (wt%) have been anodically polarized in 0.5 M H2SO4 containing Cl−, and the conditions for passivity, pitting and corrosion with respect to alloy composition and Cl− concentration broadly defined. Breaks occur in the values of the corrosion properties at about 30% and 70% Ni. It is considered that the corrosion properties of alloys containing up to 30% Ni are determined by the ferrite in the alloy and the low corrosion resistance of its surface film, that alloys containing 30 to 70% Ni have a corrosion resistant film probably similar to a nickel ferrite spinel, and that alloys containing over 70% Ni have properties similar to nickel and probably have a surface film based on a solid solution of iron in NiO.

Transmission electron microscope observation of the {001} 〈110〉 glide system in spinel nickel ferrite at room temperature

Abstract It is confirmed that the fine structure of screw dislocations in the spinel structure consists of a core appreciably dissociated in a {001} plane. An example of a {001} 〈110〉 glide system is given by electron microscope analysis of a deformed area close to a room-temperature Vickers indentation. It is concluded that isolated dislocations behave as if their glide were easier on {001} planes than on {111} planes at room temperature.