Aqueous Co-precipitation Method Research Articles

Controlled Synthesis, Characterization and Magnetic Properties of Magnetite (Fe<sub>3</sub>O<sub>4</sub>) Nanoparticles without Surfactant under N<sub>2</sub> Gas at Room Temperature

In this study, magnetite (Fe3O4) nanoparticles were synthesized at room temperature using FeCl3.6H2O (1.28 M), FeCl2.4H2O (0.64 M) and HCl (0.4 M) for preparing a solution as the iron source and NaOH (0.9-1.5 M) for to prepare a solution as the alkali source by the aqueous phase co-precipitation method under vigorous mechanical stirring (450 and 750 rpm) together with N2 gas flowing through the reaction medium during synthesis operation in closed system. The powder samples were characterized by the commonly used techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and BET analyses. SEM was used to observe the morphology and agglomeration state of the powder. Size and morphology of the precipitated crystallites were examined with TEM. The prevalence of functional groups in the synthesized powders was ascertained by FTIR spectroscopy. The pure magnetite and other phases according to processing parameters were observed by XRD analysis. The magnetic properties of magnetite (Fe3O4) nanoparticles were examined using VSM. Finally, the specific surface area of nanoparticles was measured by BET technique. The results indicate that smaller particles can be synthesized by increasing stirring rate and decreasing the NaOH concentration, which in this case corresponded to 35 nm using 0.9 M NaOH at 750 rpm. The VSM analysis showed a saturation magnetization range of (82-96 emu/g) and coercivity of (83-119 Oe) for particles between (35-96 nm) respectively. Also, the highest specific surface area of 40 m2/g was obtained at 0.9 M NaOH at 750 rpm and the smallest value of 15 m2/g at 1.5 M of NaOH at 450 rpm using BET analysis.

Structure, morphology and magnetic properties ofMg(x) Zn(1 − x)Fe2O4 ferrites prepared by polyol and aqueous co-precipitation methods: a low-toxicity alternative toNi(x)Zn(1 − x)Fe2O4 ferrites

The synthesis and properties ofMg(x)Zn(1 − x)Fe2O4 spinel ferrites as a low-toxicity alternative to the technologically significantNi(x)Zn(1 − x)Fe2O4 ferrites are reported. Ferrite nanoparticles have been formed through boththe polyol and aqueous co-precipitation methods that can be readilyadapted to industrial scale synthesis to satisfy the demand of a variety ofcommercial applications. The structure, morphology and magnetic properties ofMg(x)Zn(1 − x)Fe2O4 were studied as a function of composition and particle size. Scanning electron microscopy images showparticles synthesised by the aqueous co-precipitation method possess a broad size distribution (i.e. ∼ 80–120 nm) with an average diameter of the order of100 nm ± 20 nm and could be produced in high process yields of up to 25 g l − 1. In contrast, particles synthesised by the polyol-based co-precipitationmethod possess a narrower size distribution with an average diameter in the30 nm ± 5 nm range but are limited to smaller yields of ∼ 6 g l − 1. Furthermore, the polyol synthesis method was shown to control average particle size byvarying the length of the glycol surfactant chain. Particles prepared by both methods arecompared with respect to their phase purity, crystal structure, morphology, magneticproperties and microwave properties.

Numeric Simulations of a Novel Wideband Electromagnetic Band Gap Metamaterial Utilizing Oriented Cobalt-Substituted Z-Type Barium Hexaferrites

The material parameters of an electromagnetic bandgap (EBG) metamaterial consisting of metallic Sievenpiper structures prepared upon a Co2Z hexaferrite substrate having μr = 12 to 14 and er = 10 to 12 are reported. A bandwidth of 50%-75% of L-band was realized in simulation. The synthesis of the Co2Z hexaferrite material with optimized properties was achieved via a modified aqueous coprecipitation method with yields of up to 25 g/L. Magnetically oriented Co2Z substrates were demonstrated to exhibit a zero-field ferromagnetic resonance frequency of ~1.1 GHz that enabled device application from ultrahigh frequency (UHF) through L-band frequencies. EBG metamaterials designed and simulated on an oriented Co2Z hexaferrite substrate were compared to standard dielectric EBG designs. Results indicate that standard dielectric EBG designs, which operate over a 50% bandwidth and profile height of ~λo/10, are replaceable with an equivalent bandwidth Co2Z EBG metamaterial designed to a height of ~λo/95. The applications of the proposed metamaterial toward ultralow profile antenna designs at UHF through L-band are discussed.

A Facile Route to Prepare Tetragonal BaTiO3 Nanoparticle Through Composition Control

In the present work, tetragonal BaTiO3 particles down to 20 nm have been synthesized by low temperature aqueous co-precipitation method through composition control. Field emission scanning electron microscopy (FE-SEM) images indicated that the precipitates contained fine (about 20–30 nm) faceted particles. The Raman spectra revealed that tetragonal phase appeared with the increase in Ba/Ti ratio in the precursor solution. The appearance of tetragonal phase in BaTiO3 nanoparticle was related with the lattice defect revealed by lattice parameter and lattice strain calculated by XRD results. The lattice defect can be modified through composition control.

Preparation and Characterization of Pure‐Phase Co2Y Ferrite Powders via a Scalable Aqueous Coprecipitation Method

Aqueous chemical coprecipitation methods have been developed to produce large quantities, 12 g per batch, of pure‐phase Ba2Co2Fe12O22 Y‐type hexaferrite powders. X‐ray diffraction studies showed that sintering temperatures as low as 900°C were sufficient to produce a single‐phase Y‐type hexaferrite material. The method has also been shown to lend itself to efficient scale up, leading to large batch production. The growth of particles as a function of time and temperature in a single‐step sintering process, as opposed to multiple annealing and sintering processes required in conventional ceramic processing, was explored. Size and shape of particles have been characterized by scanning electron microscopy, while the magnetic properties were studied by vibrating sample magnetometry. Measured structural and magnetic properties are closely matched with those of bulk ceramic materials, indicating that the proposed approach may serve as a large‐scale, cost‐effective substitute to conventional ceramic processing of hexagonal ferrite materials.

Synthesis of cobalt-doped cadmium sulphide nanocrystals and their optical and magnetic properties

Cobalt-doped cadmium sulphide (CdS) nanocrystals (NCs) were synthesized with three different cobalt concentrations by aqueous chemical coprecipitation method. Dopant incorporation was recognised using X-ray diffraction (XRD) analysis with a shift in the diffraction peaks and compression in the lattice. The size and crystallinity of the cobalt-doped CdS NCs were studied by high resolution transmission electron microscopy (HRTEM). The blue shift in the spectra and the band gap value of Co-doped CdS NCs was estimated using reflectance UV spectrophotometer. Variation in the luminescence properties was studied by fluorescence spectroscopy. The change in the optical properties supports the Co incorporation in the CdS NCs. The BET measurement revealed that the powders had a relatively high specific surface area of 131.30, 106.93 and 102.04 m2/g for 2, 4 and 6% Co:CdS, respectively. Room temperature magnetisation was studied using vibrating sample magnetometer for both 4 and 6% cobalt-doped CdS NCs, which revealed a weak ferromagnetic signal and strong ferromagnetic hysteresis respectively.

Morphology controllable synthesis of Ba(Ti0˙9Zr0˙1)O3 nanoparticles by low temperature aqueous coprecipitation method

Single phase Ba(Ti0˙9Zr0˙1)O3 nanoparticles have been synthesised by a low temperature aqueous coprecipitation method without any dispersant or further thermal treatment. Ba(Ti0˙9Zr0˙1)O3 nanoparticles with different particle sizes and morphology were synthesised at 65 or 85°C under ambient condition. Based on XRD patterns and field emission scanning electron microscopy images, the particle sizes decrease with the increase in the solution concentration. In addition, the morphology of the particles changes from coral-like to sphere-like with the increase of the solution concentration under constant stirring, and the critical concentration decreases with the increase in temperature, but the particles remain sphere-like when there is no mechanical agitation. The morphology transition behaviour can be understood by the different nucleation modes in the presence or absence of mechanical agitation, which was verified by the high resolution TEM images.

Characterization of Inhibitor Release from Zn-Al-[V10O28]6−Hydrotalcite Pigments and Corrosion Protection from Hydrotalcite-Pigmented Epoxy Coatings

Abstract A Zn-Al-[V10O28]6− hydrotalcite ion exchange compound was synthesized as a corrosion inhibiting pigment additive for protective organic coatings. A simple aqueous coprecipitation method wa...

Synthesis and characterization of Ba(TI1-xZRx)O₃ nanopowders by an aqueous coprecipitation method

Synthesis and characterization of Ba(TI1-xZRx)O₃ nanopowders by an aqueous coprecipitation method

Effect of surface states of layered double hydroxides on conductive and transport properties of nanocomposite polymer electrolytes

All solid-state poly(ethylene oxide) (PEO) nanocomposite electrolytes were made containing nanoscale fillers of layered double hydroxides (LDHs). Two kinds of LDHs with different surface states were prepared by aqueous co-precipitation method. The LDHs were added into PEO matrix to study the structures, conductivities and ionic transport properties of nanocomposite electrolytes. The structures of LDHs were characterized by infrared spectra, thermogravimetric analysis and wide-angle X-ray diffraction. With enhanced compatibility of LDH sheets by oligo(ethylene oxide) surface modification, the PEO/OMLDH nanocomposite electrolyte exhibits an amorphous morphology and an enhancement of conductivity by three orders of magnitude as compared to pure PEO electrolyte. The lithium ion transference number T Li + of PEO/LDH nanocomposite electrolyte measured with a value of 0.42 is two times higher than the one of pure PEO electrolyte, which can be attributed to the Lewis acid–base interaction between surface states of metal hydroxides and counter anions of lithium salts.

Synthesis and Magnetic Properties of Fe3O4 Nanoparticles

Magnetic Fe3O4 nanoparticles with size below 10 nm have been prepared by the aqueous phase coprecipitation method. The Fe3O4 nanoparticles show typical superparamagnetism. Comparison is made between the dispersed sample and the powder sample, and the results are discussed.

Size-dependent magnetic properties of MnFe2O4 fine particles synthesized by coprecipitation.

Manganese ferrite, ${\mathrm{MnFe}}_{2}$${\mathrm{O}}_{4}$, fine particles in the size range 5--15 nm have been prepared by an aqueous phase coprecipitation method. The freshly prepared particles are in a metastable state with regard to the cation distribution between the A and B sites of the spinel lattice. Thermomagnetic, differential scanning calorimetry and M\ossbauer spectroscopy show that heat treatment under inert gas to 670 K irreversibly changes the cation distribution to a stable state. Heat treatment of freshly prepared samples in air to 470 K both changes the cation site distribution somewhat and, most importantly, oxidizes the ${\mathrm{Mn}}^{2+}$ to ${\mathrm{Mn}}^{3+}$. The Curie temperature is modified in association with these changes. With this knowledge, we create a series of samples with various sizes but the same microstructure. We find the following. (1) The Curie temperature decreases relative to the bulk as size decreases. The decrease is consistent with finite size scaling. (2) The fit of the spontaneous magnetization to the Bloch ${\mathit{T}}^{3/2}$ law yields a Bloch constant larger than the bulk increasing with decreasing size in proportion to the specific surface area of the particles. We find a better fit is obtained if the exponent of the temperature is increased to be in the range 1.6 to 1.8. (3) The saturation magnetization decreases with decreasing size also in proportion to the specific surface area of the particles. \textcopyright{} 1996 The American Physical Society.