Synthesis and characterization of nanosize nickel-doped cobalt ferrite obtained by precursor combustion method

Nanoparticles of the spinel ferrite, Co_1?x Ni _x Fe₂O₄ (x?=?0, 0.2, 0.3) have been synthesized by the precursor combustion technique. Novel precursors of metal fumarato-hydrazinate have been employed to yield the nanosized spinel ferrite. A characteristic feature of these precursors is that they decompose autocatalytically after ignition to give the monophasic nanocrystalline ferrite. This fact is corroborated by X-ray powder diffraction analysis. The thermal decomposition pattern of the precursors has been studied by isothermal thermogravimetric and differential thermal analysis. In order to fix the chemical composition, the precursors have been characterized by FTIR and chemical analysis and their chemical composition has been fixed accordingly. The Curie temperature of the ??as-prepared?? oxide was determined by alternating current susceptibility measurements.     

Synthesis of cobalt nickel ferrite nanoparticles via autocatalytic decomposition of the precursor

The chemistry, structure, and properties of spinel ferrites are largely governed by the method of preparation. The metal carboxylato-hydrazinate precursors are known to yield nanosized oxides at a comparatively lower temperature. In this study, we are reporting the synthesis of one such precursor, cobalt nickel ferrous fumarato-hydrazinate which decomposes autocatalytically to give cobalt nickel ferrite nanoparticles. The XRD study of this decomposed product confirms the formation of single-phase spinel, i.e., Co_0.5Ni_0.5Fe₂O₄. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric (TG), and differential scanning calorimetric (DSC) analysis. The precursor has also been characterized by FTIR, EDX, and chemical analysis, and its chemical composition has been determined as Co_0.5Ni_0.5Fe₂(C₄H₂O₄)₃·6N₂H₄.     

Synthesis and characterization of Ni<Subscript>0.6</Subscript>Zn<Subscript>0.4</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nano-particles obtained by auto catalytic thermal decomposition of carboxylato-hydrazinate complex

Ni_0.6Zn_0.4Fe₂O₄ nano-particles have been synthesized by self-propagating auto-combustion of nickel zinc ferrous fumarato-hydrazinate complex. The precursor complex has been characterized by chemical analysis, IR, AAS, thermal analysis and isothermal mass loss studies. The precursor on ignition undergoes self-propagating auto combustion to give Ni_0.6Zn_0.4Fe₂O₄. The X-ray diffraction studies confirmed the single phase formation of nano-size ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. TEM observation showed the average particle size to be 20 nm. Infrared and magnetization studies were also carried out on the ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. The lower value of saturation magnetization and higher Curie temperature of ‘as synthesized’ ferrite also hint at the nano size nature.     

Synthesis and characterization of Co<Subscript>0.8</Subscript>Zn<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

Cobalt zinc ferrite, Co_0.8Zn_0.2Fe₂O₄, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate. The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been determined as Co_0.8Zn_0.2Fe₂(C₄H₂O₄)₃·6N₂H_4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements.     

Preparation,spectroscopic and thermal analysis of hexa-hydrazine nickel cobalt ferrous succinate precursor and study of solid-state properties of its nanosized thermal product,Ni<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

Nickel cobalt ferrite, Ni_0.5Co_0.5Fe₂O₄, has been prepared by precursor combustion technique from hexa-hydrazine nickel cobalt ferrous succinate precursor. The precursor was characterized by chemical analysis, CHNS analysis, infrared spectroscopy, TG–DTA and mass loss studies. The thermal data show how the precursor decomposes in four steps to give stable ferrite phase. The precursor decomposes autocatalytically once initially ignited, to give the ‘as-prepared’ nano-spinel ferrite. The X-ray diffraction analysis reveals single cubic spinel phase structure. The infrared measurements between 4000 and 350 cm^?1 confirmed the intrinsic cation vibrations of the spinel structure. The SEM image clearly shows the nanosized nature of the ferrite. The dielectric constant and loss tangent are found to decrease with increase in frequency which is due to Maxwell–Wagner interfacial polarization. The loss tangent shows a relaxation peak at ~1 kHz. The variation of DC electrical resistivity with temperature indicates semiconductor behaviour. The temperature- and field-dependent magnetization data of ‘as-prepared’ ferrite reveal that the lattice has either a canted or partially misaligned spin structure due to the nanosized nature of the ferrite.     

Synthesis and thermal studies of the cobalt zinc ferrous fumarato-hydrazinate

Nanosize Co_1?x Zn _x Fe₂O₄ (x?=?0, 0.1, 0.3, and 0.4) have been synthesized by the precursor combustion technique via autocatalytic combustion of the mixed-metal fumarato-hydrazinate precursors. A key feature of these precursors is that they decompose autocatalytically once ignited to give the monophasic nanocrystalline ferrite. This fact is confirmed by X-ray powder diffraction analysis. The thermal decomposition pattern of the precursors has been studied by thermogravimetric and differential thermal analysis. The precursors have also been characterized by FTIR and chemical analysis to fix the chemical composition. The Curie temperature (T _c) of the ??as-prepared?? oxide was determined by alternating current susceptibility measurements.     

Impact of Gd3+ and Nd3+ ions substitution on structural and magnetic properties of Co0.5Ni0.5Fe2O4 ferrite system

Co_0.5Ni_0.5(Gd/Nd)_xFe_2-xO₄ (x ?= ?0.0 and 0.06) ferrites were prepared by the solid-state reaction method. These materials were characterized by XRD, FT-IR spectroscopy, and VSM techniques. The XRD analysis revealed the phase formation of all samples and their cubic spinel structure with the Fd-3m space group. Lattice constant was found to increase due to Gd and Nd ions substitution. However, the crystallite size was observed to decrease by the substitution effect. The FT-IR spectra showed the two vibrational frequency bands of the tetrahedral and octahedral sites. From the magnetic properties study, it was identified that the pure and Gd substituted Co_0.5Ni_0.5Fe₂O₄ ferrite showed a ferromagnetic behaviour. While the Nd substituted Co_0.5Ni_0.5Fe₂O₄ ferrite delivered a superparamagnetic behaviour. The substitution of Gd and Nd changed the values of the magnetic parameters of Co_0.5Ni_0.5Fe₂O₄ ferrite. An increase in the saturation magnetization (M_s) value was observed due to substitution of Gd and Nd in Co_0.5Ni_0.5Fe₂O₄ ferrite, indicating that Gd and Nd substitution strengthen the supermagnetic interactions in Co_0.5Ni_0.5Fe₂O₄ ferrite. The highest value of M_s was observed in Gd doped sample.     

Synthesis of multielement ferrites and their silica composites

Ferrites of composition M_0.2Co_0.4Zn_0.4Fe₂O₄ with M = Cu²⁺, Mn²⁺ and Ni²⁺ were prepared by citrate complex method. Later, their composites with silica have also been obtained by a simple route. The citrate complex precursors of multielement ferrites were characterized by FTIR spectroscopy and thermal analysis, been found a similar behavior for the three systems. The thermal treatment (at 400, 600 and 800 °C) of precursors gives, as result, the spinel type cubic ferrite pure when the ions substituted were copper and nickel; when manganese was used an hematite phase was obtained as contaminant at 800 °C. The presence of all ions involved and the particle size was corroborated by EDX analysis and measured from a TEM micrograph, respectively. The magnetic parameters related to magnetic properties, magnetization and coercivity, were different depending of the chemical composition of the ferrite and the thermal treatment temperature, as it was expected. At room temperature, the values obtained were near to those reported for Co-ferrite in bulk. The synthesis route of the composites M_0.2Co_0.4Zn_0.4Fe₂O₄-SiO₂, proposed in this work, gives as result magnetic nanoparticles in an amorphous silica matrix. Their magnetic properties were depending on weight percentage of the magnetic phase in the composite.     

Synthesis, characterization, infrared studies, and thermal analysis of Mn0.6Zn0.4Fe2(C4H2O4)3·6N2H4 and its decomposition product Mn0.6Zn0.4Fe2O4

Manganese zinc ferrous fumarato–hydrazinate precursor, Mn_0.6Zn_0.4Fe₂(C₄H₂O₄)₃·6N₂H₄ was synthesized for the first time and characterized by chemical analysis, infrared spectral studies, and thermal analysis. Infrared studies show band at 977 cm^?1 indicating bidentate bridging nature of the hydrazine in the complex. Thermogravimetric (TG) studies show two steps dehydrazination followed by two steps total decarboxylation. The precursor on touching with burning splinter undergoes self propagating autocatalytic decomposition yielding ultrafine Mn_0.6Zn_0.4Fe₂O₄. XRD studies confirms single phase formation as well as nanosize nature of “as prepared” Mn_0.6Zn_0.4Fe₂O₄. The saturation magnetization of the “as prepared” Mn_0.6Zn_0.4Fe₂O₄ was found to be 31.46 emu gm^?1, which is lower than the reported, confirms the ultrafine nature of the oxide.     

Preparation and characterization of Co0.5Zn0.5Fe2(C4H2O4)3·6N2H4 A precursor to prepare Co0.5Zn0.5Fe2O4 nanoparticles

A good precursor is foremost in the preparation of nanosized metal or mixed metal oxides. In the present study a novel precursor, cobalt zinc fumarato-hydrazinate Co_0.5Zn_0.5Fe₂(C₄H₂O₄)₃·6N₂H₄ has been prepared which decompose at a much lower temperature to give nanosized mixed-metal oxides. X-ray investigations, confirms the formation of single spinel phase. The FTIR spectra show N-N stretching vibration at 965 cm⁻¹ which confirms the bidentate bridging hydrazine. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential scanning calorimetric analysis. The precursor shows two-step dehydrazination followed by decarboxylation to form Co_0.5Zn_0.5Fe₂O₄, the chemical analysis of the sample is corroborative of this.     

Preparation and Characterization of Single-Phase Perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ

Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ has been successfully prepared by using citrate-EDTA complexation method at relatively low calcination temperature. The structure and thermal decomposition process of the complex precursor have been investigated by means of differential scanning calorimetry-thermal gravimetric analysis (DSC/TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopic (FT-IR) measurements. The precursor decomposed completely and started to form perovskite-type oxide above 420℃ according to the differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results. Single-phase perovskite La0.6Sr0.4Co0.8Fe0.2O3-δ obtained has been confirmed from the XRD pattern, and no peak of SrCO3 was found by XR.D of the oxides synthesized at a relatively low temperature of 800 ℃. The reducibility of La0.6Sr0.4Co0.8Fe0.2O3-δ was also characterized by the temperature programmed reduction (TPR) technique. Disk shaped dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was prepared by the isostatical pressing method. The oxygen flux rate of dense La0.6Sr0.4Co0.8Fe0.2O3-δ membrane was (2.8-18)×10-8 mol/(cm2·s) in the temperature range of 800-1 000℃.     

Nickel‐substituted cobalt ferrite nanoparticles supported on arginine‐modified graphene oxide nanosheets: Synthesis and catalytic activity

The amino acid arginine was used to modify the surface of graphene oxide nanosheets and then nickel‐substituted cobalt ferrite nanoparticles were supported on those arginine‐grafted graphene oxide nanosheets (Ni_0.5Co_0.5Fe₂O₄@Arg–GO). The prepared Ni_0.5Co_0.5Fe₂O₄@Arg–GO was characterized using flame atomic absorption spectroscopy, inductively coupled plasma optical emission spectrometry, energy‐dispersive spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The application of Ni_0.5Co_0.5Fe₂O₄@Arg–GO as a catalyst was examined in a one‐pot tandem oxidative cyclization of primary alcohols with o ‐phenylenediamine to benzimidazoles under aerobic oxidation conditions. The results showed that 2‐phenylbenzimidazole derivatives were successfully achieved using Ni_0.5Co_0.5Fe₂O₄@Arg–GO nanocomposite catalyst via the one‐pot tandem oxidative cyclization strategy.     

纯相和镍取代的Co_3O_4尖晶石催化剂用于N_2O直接分解(英文)

A series of NixCo1-xCo2O4(0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N2O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500 °C for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co3O4. The N2O decomposition measurement revealed significant increase in the activity of Co3O4 spinel oxide catalyst with the partial replacement of Co2+ by Ni2+. The activity of this series of catalysts was controlled by the degree of Co2+ substitution by Ni2+, spinel crystallite size, catalyst surface area, presence of residual K+, and calcination temperature.     

Enzyme mimics of spinel-type CoxNi1−xFe2O4 magnetic nanomaterial for eletroctrocatalytic oxidation of hydrogen peroxide

A series of spinel-type Co_xNi_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) magnetic nanomaterials were solvothermally synthesized as enzyme mimics for the eletroctrocatalytic oxidation of H₂O₂. X-ray diffraction and scanning electron microscope were employed to characterize the composition, structure and morphology of the material. The electrochemical properties of spinel-type Co_xNi_1−xFe₂O₄ with different (Co/Ni) molar ratio toward H₂O₂ oxidation were investigated, and the results demonstrated that Co_0.5Ni_0.5Fe₂O₄ modified carbon paste electrode (Co_0.5Ni_0.5Fe₂O₄/CPE) possessed the best electrocatalytic activity for H₂O₂ oxidation. Under optimum conditions, the calibration curve for H₂O₂ determination on Co_0.5Ni_0.5Fe₂O₄/CPE was linear in a wide range of 1.0 × 10⁻⁸–1.0 × 10⁻³ M with low detection limit of 3.0 × 10⁻⁹ M (S/N = 3). The proposed Co_0.5Ni_0.5Fe₂O₄/CPE was also applied to the determination of H₂O₂ in commercial toothpastes with satisfactory results, indicating that Co_xNi_1−xFe₂O₄ is a promising hydrogen peroxidase mimics for the detection of H₂O₂.     

Synthesis and magnetic properties of nanocomposite Ni1?xCoxFe2O4–BaTiO3 fibers by organic gel-thermal decomposition process

Nanocomposites of ferrite and ferroelectric phases are attractive functional ceramic materials. In this work, the nanocomposite Ni_1−x Co _x Fe₂O₄–BaTiO₃(x = 0.2, 0.3, 0.4, 0.5) fibers with fine diameters of 3 ~ 7 μm and high aspect ratios were synthesized by the organic gel-thermal decomposition process from the raw materials of citric acid and metal salts. The structure, thermal decomposition process and morphologies of the gel precursors and the resultant fibers derived from thermal decomposition of the gel precursors were characterized by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction and scanning electron microscopy. The magnetic properties of the nanocomposite fibers were measured by vibrating sample magnetometer. The nanocomposite fibers of ferrite Ni_1−x Co _x Fe₂O₄ and perovskite BaTiO₃ are formed at the calcination temperature of 900 °C for 2 h. The average grain sizes of Ni_1−x Co _x Fe₂O₄ and BaTiO₃ in the nanocomposite fibers increase from about 15 nm to approximately 67 nm with the increasing calcination temperatures from 900 to 1,180 °C. The saturation magnetization of the nanocomposite Ni_1−x Co _x Fe₂O₄–BaTiO₃(x = 0.2, 0.3, 0.4, 0.5) fibers increases with the increase of grain sizes of Ni_1−x Co _x Fe₂O₄ and Co content, while the coercivity reaches a maximum value at the single-domain size of about 65 nm of Ni_0.5Co_0.5Fe₂O₄ obtained at the calcination temperature of 1,100 °C.     

Synthesis and magnetic properties of octahedral ferrite Ni χ Co1−χ Fe2O4 nanocrystals

A series of Ni doped cobalt ferrite compounds with the formula Ni _χ Co_1−χ Fe₂O₄ where x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were prepared using a hydrothermal method and subsequently sintered/annealed at 600 °C for 3 h. The influence of the Ni content on the lattice parameter, a, stretching vibration and the magnetization of specimens were subsequently studied. XRD and FTIR were used to investigate structure and composition variations. All samples were found to have a cubic spinel structure. SEM was used to study morphological variations. The results indicate that the average particle sizes are between 30–35 nm with a narrow size distribution along with nanocrystals forming of regular octahedrons. A decrease in the peak to peak line width and increase in resonance field with increasing Ni content were observed from ESR measurements. Based on ESR results, a core-shell type of formation was proposed where the core is made up of undoped CoFe₂O₄ and the shell is Ni²⁺ doped CoFe₂O₄.      

Ammonia gas sensor based on a spinel semiconductor,Co<Subscript>0.8</Subscript>Ni<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanomaterial

Thick film of nanocrystalline Co_0.8Ni_0.2Fe₂O₄ was obtained by sol–gel citrate method for gas sensing application. The synthesized powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy. The XRD pattern shows spinel type structure of Co_0.8Ni_0.2Fe₂O₄. XRD of Co_0.8Ni_0.2Fe₂O₄ revels formation of solid solution with average grain size of about 30 nm. From gas sensing properties it observed that nickel doping improves the sensor response and selectivity towards ammonia gas and very low response to LPG, CO, and H₂S at 280 °C. Furthermore, incorporation of Pd improves the sensor response and stability of ammonia gas and reduced the operating temperature upto 210 °C. The sensor is a promising candidate for practical detector of ammonia.     

Low-temperature synthesis and characterization of the Mn–Zn ferrite

Nanocrystalline ferrite with the composition: Mn_0.6Zn_0.4Fe₂O₄ was synthesized by two-stage route: the precipitation of Zn, Mn and Fe hydroxides from sulphates solution and the synthesis of a precursor by the sol–gel auto-combustion method. The ferrite powder obtained from the gel by ashing was sintered under air at a temperature of 720, 1150 and 1300 °C. The composition and morphology of the as-obtained phases were examined by ICP-AES, TG/DTA, XRD, FTIR, SEM and low-temperature nitrogen adsorption (BET). It was found that the spinel phase forms after gel combustion. The nanometric ferrite powder obtained as a result of the combustion is soft-agglomerated. The zinc content in the ferrite during ashing and auto-combustion is lower by about 21 mol% than the assumed one and the final product turn out to be Mn_0.68Zn_0.32Fe₂O₄.     

Structure and Magnetic Properties of Nickel–Zinc Ferrite Nanoparticles Prepared by Glass Crystallization Method

The magnetic and microstructure properties of Fe₂O₃–0.4NiO–0.6ZnO–B₂O₃ glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni_0.4Zn_0.6-Fe₂O₄ crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and 3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer. The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with saturation magnetization ranging from 12.25 to 17.82 emu/g.     

Structure and Magnetic Properties of Nickel–Zinc Ferrite Nanoparticles Prepared by Glass Crystallization Method

Summary. The magnetic and microstructure properties of Fe₂O₃–0.4NiO–0.6ZnO–B₂O₃ glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni_0.4Zn_0.6-Fe₂O₄ crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and 3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer. The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with saturation magnetization ranging from 12.25 to 17.82 emu/g.