Effects of Nd concentration on structural and magnetic properties of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

Zinc ferrite nanomaterials have been received significant attention in recent years on account of their potential applications in the fields of electronics, optoelectronics and magnetics. To enhance the magnetic properties of zinc ferrites, Nd-doped zinc ferrites (ZnFe_2?xNd_xO₄, x?=?0, 0.01, 0.02, 0.03) nanoparticles (NPs) have been prepared by the sol–gel method. The effects of Nd doping concentration on the structural and magnetic properties of zinc ferrites were studied. The results of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy indicated that the Nd ions were incorporated into the crystal lattice of ZnFe₂O₄ and substituted for the Fe³⁺ sites. Unlike pure zinc ferrites with paramagnetism, Nd doped ZnFe₂O₄ NPs were superparamagnetic at room temperature. Vibrating sample magnetometry results showed, with the increase of Nd content, the saturation magnetization of Nd doped ZnFe₂O₄ NPs increased.     

A new strategy for the preparation of porous zinc ferrite nanorods with subsequently light-driven photocatalytic activity

Porous zinc ferrite (ZnFe₂O₄) nanorods have been synthesized by the thermal decomposition of ZnFe₂(C₂O₄)₃ nanorods precursor, which was prepared by template-, surfactant-free solvothermal method. The morphology and structure of the obtained ZnFe₂(C₂O₄)₃ nanorods precursor and porous ZnFe₂O₄ nanorods were characterized by X-ray powder diffraction, transmission electron microscopy, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results indicated that the as-synthesized ZnFe₂O₄ retained the precursor morphology of 1D nanorods with diameters of 100–200 nm and lengths of several micrometers and plenty of nanoparticles were interconnected to each other to form porous nanorods. The as-prepared ZnFe₂O₄ nanorods as a kind of subsequently light-driven photocatalyst exhibited good photocatalytic decomposition activity for methylene blue (MB).     

Physicochemical properties of fine-particle ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> prepared by spray pyrolysis of nitrate solutions

Fine zinc ferrite (ZnFe₂O₄) powders uniform in morphology have been prepared by spray pyrolysis of nitrate solutions. Examination by scanning electron microscopy showed that the powders consisted of micron- and submicron-sized polycrystalline spherical particles. The ZnFe₂O₄ sample prepared by pyrolysis at 1000°C had paramagnetic properties. Its crystal structure was refined by the Rietveld method and was shown to be a partially inverse spinel with a degree of inversion near 15%. According to nitrogen adsorption measurements, the specific surface of the powders was 5.2 m²/g. The electrical conductance of a film produced from fine-particle zinc ferrite was found to be very sensitive to the hydrogen sulfide concentration in air.     

Facile synthesis and characterization of ZnFe2O4/α-Fe2O3 composite hollow nanospheres

ZnFe₂O₄/α-Fe₂O₃ composite hollow nanospheres were successfully fabricated via a facile one-pot solvothermal method, utilizing polyethylene glycol as soft template. X-ray diffraction and scanning electron microscopy analysis revealed that the prepared nanospheres with cubic spinel and rhombohedra composite structure had a uniform diameter of about 370 nm, and the hollow structure could be further confirmed by transmission electron microscopy. Energy dispersive X-ray, X-ray photoelectron spectroscopy and Fourier transform infrared techniques were also applied to characterize the elemental composition and chemical bonds in the hollow nanospheres. The ZnFe₂O₄/α-Fe₂O₃ composite hollow nanospheres show attractive light absorption property for potential applications in electronics, optics, and catalysis.     

Facile synthesis and characterization of TiO<Subscript>2</Subscript>–graphene–ZnFe<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Tb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4</Subscript> ternary nano-hybrids

Rare earth ion (Tb³⁺)-doped zinc ferrite (ZnFe₂O₄) nanoparticles grown on reduced graphene oxide (RGO) prepared through sol–gel method have been reported. During the sol–gel process, graphene oxide was reduced to RGO, and, subsequently, anatase TiO₂ and cubic spinel ZnFe_2?x Tb _x O₄ were grown in situ on the surfaces of the RGO nano-sheets. The structure, surface morphology and chemical composition of ternary nano-composites were studied using scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, photoluminescence spectra and vibrating sample magnetometer (VSM). XRD results showed that the produced TiO₂ was composed of anatase and some rutile phases and ZnFe₂O₄ with a cubic spinel structure. The particle sizes of ZnFe₂O₄ and TiO₂ nanoparticles were in the ranges of ~65–80 and ~17–20 nm, respectively. The saturation magnetization (M _S) determined from VSM was found to linearly increase with Tb³⁺ concentration.     

Magnetic Properties of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles Synthesized by Starch-Assisted Sol–Gel Auto-combustion Method

In this paper, ZnFe₂O₄ spinel ferrite nanoparticles with different grain sizes at different annealing temperatures have been synthesized using the starch-assisted sol–gel auto-combustion method. The synthesized nanoparticles were characterized by conventional powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and vibrating sample magnetometer. The X-ray diffraction (XRD) patterns demonstrated that the ZnFe₂O₄ nanoparticles consist of single-phase spinel structure with crystallite sizes 4.81, 8.72, 12.06, 29.32, and 72.60 nm annealed at 400, 600, 800, 1000, and 1200 °C, respectively. Field emission scanning electron microscopy reveals that particles are of spherical morphology at lower annealing temperature and hexagonal-like morphology at higher temperature. An infrared spectroscopy study shows the presence of two principal absorption bands in the frequency range around 525 cm^?1 (ν ₁) and around 350 cm^?1 (ν ₂), which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Raman spectroscopy study also indicated the change in octahedral and tetrahedral site-related Raman modes in zinc ferrite nanoparticles with change of particle size. The nanocrystalline ZnFe₂O₄ samples (4.81, 8.72, 12.06, 29.32 nm) show ferrimagnetic behavior, and bulk sample (72.60 nm) shows paramagnetic behavior. This change in magnetic behavior is due to change of cation distribution in ZnFe₂O₄ nanoparticles with decrease of particle size.     

One-step hydrothermal synthesis of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nano-octahedrons as a high capacity anode material for Li-ion batteries

Binary transition metal oxides are considered as promising anode materials for lithium-ion batteries (LIB), because they can effectively overcome the drawbacks of simple oxides. Here, a one-step hydrothermal method is described for the synthesis of regular ZnFe₂O₄ octahedrons about 200 nm in size at a low temperature without further annealing being required. The ZnFe₂O₄ octahedrons were characterized by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical performance of the ZnFe₂O₄ octahedrons was examined in terms of cyclic voltammetry and discharge/charge profiles. The ZnFe₂O₄ octahedrons exhibit a high capacity of 910 mA·h/g at 60 mA/g between 0.01 and 3.0 V after 80 cycles. They also deliver a reversible specific capacity of 730 mA·h/g even after 300 cycles at 1000 mA/g, a much better performance than those in previous reports. A set of reactions involved in the discharge/charge processes are proposed on the basis of ex situ high-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of the electrode materials. The insights obtained will be of benefit in the design of future anode materials for lithium ion batteries.      

Structural,morphological and magnetic properties of hydrothermally synthesized ZnFe2O4 nanoparticles

Zinc ferrite (ZnFe₂O₄) nanoparticles were synthesized by a surfactant assisted hydrothermal method using different concentrations of ethylamine (EA) namely, 2, 4, 6, 8 and 10 ml. The powder X-ray diffraction measurements revealed that the amount of EA plays an important role in the formation of single phase ZnFe₂O₄ nanoparticles. The amount of 2 and 4 ml of EA yielded mixed phases of α-Fe₂O₃ and ZnFe₂O₄ whereas 6 ml of EA produced well crystalline and single phase ZnFe₂O₄ with regular spinel structures. Field emission scanning electron microscopy images revealed that ZnFe₂O₄ possess spherical shape, irrespective of the concentrations of EA. Magnetic characterizations revealed that the synthesized samples with EA concentrations 6, 8, 10 ml were superparamagnetic in nature at room temperature.     

Fabrication and application of MFe2O4 (M = Zn,Cu) nanoparticles as anodes for Li ion batteries

In this work, MFe₂O₄ (M?=?Zn, Cu) nanoparticles were successfully prepared by a hydrothermal method. The structure, morphology, microstructure, specific surface area and electrochemical properties of the resultant particles were characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physical adsorption, charge–discharge test and cyclic voltammetry (CV) method, respectively. The resulting ZnFe₂O₄ and CuFe₂O₄ products were sphere-like and cubic-shaped particles and their average size was about 30–40?nm and 60–70?nm, respectively. The initial discharge capacities of ZnFe₂O₄ and CuFe₂O₄ electrodes reached 1287.5?mAh?g^?1 and 1412.3?mAh?g^?1, respectively, at a current density of 0.2?mA?cm^?2 in a potential range of 0.0–3.0?V. This indicated that Cu is a better counter ion than Zn. The resulting MFe₂O₄ nanoparticles are expected to be a promising candidate of anode materials for Li ion batteries. The reaction mechanism of MFe₂O₄ nanoparticles in Li ion batteries was also discussed based on the CV of Li/MFe₂O₄ cell.     

Nanostructured ZnFe2O4 thick film as room temperature liquefied petroleum gas sensor

In the present work, thick film of nanostructured zinc ferrite was prepared by screen printing method and its liquefied petroleum gas (LPG) sensing properties were investigated. The structural and surface morphological characterisations of the sample were analysed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The minimum crystallite size of ZnFe₂O₄ calculated from Scherrer's formula is found to be 4 nm. SEM images exhibit the porous nature of the sensing material with a number of active sites. Optical characterisation of the film was carried out by ultraviolet–visible spectrophotometer. The estimated value of band gap of the film was found 1.91 eV. The LPG sensing properties of the zinc ferrite film were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the film were measured with the exposure of LPG as a function of time. The maximum values of sensitivity and percentage sensor response were found 16 and 1785, respectively, for 5 vol.% of LPG. These experimental results show that nanostructured zinc ferrite is a promising material for LPG sensor.     

Green and low temperature synthesis of nanocrystalline transition metal ferrites by simple wet chemistry routes

Crystalline and nanostructured cobalt （CoFe2O4）, nickel （NiFe2O4）, zinc （ZnFe2O4） and manganese （MnFe2O4） spinel ferrites are synthesized with high yields, crystallinity and purity through an easy, quick, reproducible and low-temperature hydrothermal assisted route starting from an aqueous suspension of copredpitated metal oxalates. The use of water as a reaction medium is a further advantage of the chosen protocol. Additionally, the zinc spinel is also prepared through an alternative route combining copredpitation of oxalates from an aqueous solution with thermal decomposition under reflux conditions. The nanocrystalline powders are obtained as a pure crystalline phase already at the extremely low tem- perature of 75 ℃ and no further thermal treatment is needed. The structure and microstructure of the prepared materials is investigated by means of X-ray powder diffraction （XRPD）, while X-ray photoelectron spectroscopy （XPS） and inductively coupled plasma-atomic emission spectroscopy （ICP-AES） analyses are used to gain information about the surface and bulk composition of the samples, respectively, confirming the expected stoichiometry. To investigate the effect of the synthesis protocol on the morphology of the obtained ferrites, transmission electron microscopy （TEM） observations are performed on selected samples. The magnetic properties of the cobalt and manganese spinels are also investigated using a superconducting quantum device magnetometer （SQUID） revealing hard and soft ferrimagnetic behavior, respectively.     

Molecular design of nanometric zinc borate-containing polyimide as a route to flame retardant materials

Zinc borate (Zn₂B₆O₁₁·3H₂O) nanoparticles were successfully prepared by using an emulsion liquid membrane (W/O/W emulsion) to control the size of particles with Na₂B₄O₇·10H₂O, boric acid and ZnSO₄·7H₂O as raw materials. All materials were dispersed with the polyimide (PI) precursor, poly (amic acid). Using a combination of dissolving the poly (amic acid) and mixing fatty acid surfactant-coated zinc borate nanoparticles; we have demonstrated the formation of nanocomposites with uniform nanoparticles dispersion. We report the first deposition of nanocomposite polyimides from solution using spin-coating. The microstructures and morphology of the as-obtained samples were studied by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA).     

Role of particle size in visible light photocatalysis of Congo Red using TiO<Subscript>2</Subscript>·[ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript>]<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanocomposites

TiO₂·[ZnFe₂O₄] _x (x = 0·0-0·5) nanocomposites (NCs) with an average particle size of 72·4 nm were synthesized by the method of co-precipitation/hydrolysis (CPH). For the comparison of particle-size dependent effects, a set of polycrystalline samples with similar compositions was also prepared by solid state reaction (SSR) route. Average particle size for SSR prepared samples was about 3·0 μm. All the samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer, Raman spectroscopy and Fourier transform infra-red (FTIR) spectroscopy. Their visible light photocatalytic activity was tested for the degradation of Congo Red dye. Maximum photodegradation was observed for the NC with x = 0·1 synthesized by CPH (particle size, 71 nm). Similar composition prepared by SSR method (particle size, 6·19 μm) showed lower photoactivity in comparison even with that observed for pure TiO₂ (particle size, 4·03 μm). It was, therefore, concluded that enhanced photodegradation is directly related to the reduced particle size of the composites, which implies that photosensitization is the process primarily involved. Although, doping of TiO₂ with ZnFe₂O₄ does extend the cut-off wavelength towards visible parts of the spectrum, its contribution in the enhancement is not as significant as that due to the photosensitization.     

Structural,Magnetic, Optical,and Catalytic Properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles by the Sol-Gel Method

This article was aimed to extend a simple procedure for the preparation by a sol-gel method by using iron nitrate and polar solvent (e.g., water) as the starting materials from the viewpoint that they are of low cost. A study of the effect of chelating agents such as citric acid weight ratio on the structure of Fe₃O₄ was reported. The synthesized product was characterized by powder X-ray diffraction (XRD), high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) studies, and vibrating sample magnetometer (VSM). Magnetic analysis revealed that the Fe₃O₄ nanoparticles had a ferromagnetic behavior at room temperature with a saturation magnetization of 20.83 emu/g. Furthermore, Fe₃O₄ nanoparticles prepared by the sol-gel method using citric acid were tested for the catalytic activity towards the oxidation of benzyl alcohol.     

Preparation of carbon nanotube-neodymium oxide composite and research on its catalytic performance

Carbon Nanotube-Neodymium Oxide (CNT-Nd₂O₃) composite was prepared by using acid treated carbon nanotubes (CNTs) and neodymium nitrate in the presence of sodium dodecyl sulfate and ammonia liquid. Techniques of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and differential thermal analysis (DTA) are used to characterize the morphology, structure, composition and catalytic property of the CNT-Nd₂O₃ composite. The experimental results show that the Nd₂O₃ nanoparticles, which have an average diameter of about 30-40 nm, are loaded on the surface of carbon nanotube. Compared with pure Nd₂O₃ nanorods, the CNT-Nd₂O₃ composite can catalyze the thermal decomposition of ammonium perchlorate more effectively. The sampling methods of the experimental samples made a difference on the catalytic experiment results, and the best catalytic result was obtained when de-ionized water served as the solvent of ammonium perchlorate.     

Preparation of continuous alumina gel fibres by aqueous sol–gel process

Continuous alumina gel fibres were prepared by sol–gel method. The spinning sol was prepared by mixing aluminum nitrate, lactic acid and polyvinylpyrrolidone with a mass ratio of 10:3:1· 5. Thermogravimetry–differential scanning calorimetry (TG–DSC), Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibres. The Al₂O₃ fibres with a uniform diameter can be obtained by sintering gel fibres at 1200 °C.     

Au/Fe3O4磁性纳米粒子的合成及表征

报道了一种合成具有巯基官能团修饰的Au/Fe_3O_4磁性纳米粒子的新方法。采用共沉淀法制备Fe_3O_4磁性纳米颗粒,并在此基础上用聚(烯丙胺)溶液还原HAuCl4,制得Au/Fe_3O_4磁性核壳纳米颗粒,再用3-巯基-1-丙磺酸钠修饰Au/Fe_3O_4磁性纳米粒子,最后得到具有巯基官能团稳定的Au/Fe_3O_4磁性纳米粒子。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)、X射线光电子能谱(XPS)、振动样品磁强计(VSM)分别对产物的微观结构及磁性特征进行表征。     

Chemical, physical, structural and morphological characterization of the electric arc furnace dust

Electric arc furnace dust (EAFD) is a hazardous industrial waste generated in the collection of particulate material during steelmaking process via electric arc furnace. Important elements to the industry such as, Fe and Zn are the main ones in EAFD. Due to their presence, it becomes very important to know how these elements are combined before studying new technologies for its processing. The aim of this work was to carry out a chemical, physical, structural and morphological characterization of the EAFD. The investigation was carried out by using granulometry analysis, chemical analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy via SEM (EDS), X-ray mapping analysis via SEM, X-ray diffraction (XRD) and Mössbauer spectroscopy. By XRD the following phases were detected: ZnFe₂O₄, Fe₃O₄, MgFe₂O₄, FeCr₂O ₄, Ca_0.15Fe_2.85O₄, MgO, Mn₃O₄, SiO₂ and ZnO. On the other hand, the phases detected by Mössbauer spectroscopy were: ZnFe₂O₄, Fe₃O₄, Ca_0.15Fe_2.85O₄ and FeCr₂O₄. Magnesium ferrite (MgFe₂O₄), observed in the XRD pattern as overlapped peaks, was not identified in the Mössbauer spectroscopy analysis.     

Self-assembly of monodisperse SiO2-zinc borate core-shell nanospheres for lubrication

Spherical SiO₂ particles have been successfully coated with zinc borate layers through a self-assembly process. The resulted SiO₂-Zn₅B₄O₁₁ core-shell nanospheres were characterized by X-ray diffraction (XRD), infrared spectra (IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The obtained SiO₂-Zn₅B₄O₁₁ core-shell nanospheres have perfect spherical shape with narrow size distribution (average diameters 50 nm), i.e., the cores with mean diameters of 40 nm and the shells with an average thickness of 5 nm, monodisperse and smooth surface. Moreover, the friction coefficient of the base oil was decreased by the addition of SiO₂-Zn₅B₄O₁₁ core-shell nanospheres.     

Photophysical properties of Eu3+ and Tb3+-doped ZnAl2O4 phosphors obtained by combustion reaction

Europium- and terbium-doped zinc aluminate oxide nanocrystals with a spinel structure were successfully prepared by a combustion method, using urea as fuel. The samples thus obtained were characterized by X-ray diffraction, scanning electron microscopy and luminescence spectroscopy. X-ray diffraction results confirmed the formation of ZnAl₂O₄ spinel phase and a minor amount of ZnO. Our SEM results revealed agglomerates in the shape of irregular plates composed of nanoparticles with dispersed points of second phase in the surface. Powders containing Eu³⁺ and Tb³⁺ ions displayed red and green photoluminescence, respectively.