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Nano-crystalline particles of barium ferrite have been prepared by co-precipitation route using aqueous and non-aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11. Water and a mixture of diethylene glycol and water with volume ratio of 3:2 were used as solvents in the process. Co-precipitated powders were annealed at various temperatures for 1 h. Phase composition of the samples was evaluated by XRD while their morphology was studied by TEM and SEM techniques. The XRD results showed that the single phase barium ferrite obtained at 750°C when diethylene glycol/water mixture was used as a solvent. This temperature increased to 900°C when the starting materials dissolved in water. Nano-size particles of barium ferrite with mean particle size of almost 50 and 80 nm were observed in the SEM micrographs of the samples synthesized in diethylene glycol/water solution after annealing at 750°C and 800°C for 1 h, respectively. The corresponding mean crystallite size measured by TEM for sample annealed at 800°C was 40 nm.

The ground state geometric structures of the nanoparticles or clusters CO_n(n = 1-6) were given based on the first-principles calculations. Then the magnetic properties of the clusters CO_n(n = 1-6) and (CO_n)^-2(n = 1-6) were calculated in system. Results show that their ground state structures are closely related to the numbers of O-ions. These clusters have no magnetic moments and half-metallicity if they are electroneutral. However, they have magnetic moments if they have positive or negative charges. The total magnetic moments of the clusters (CO_n)^-2(n = 1-6, but n≠3) are all 2.0000 μ_B, and all their ions have contributions to the total magnetic moments. The main reason is that the molecular orbitals with lower energy filled with paired electrons and the molecular orbitals with higher energy are occupied by two electrons in parallel.

In this paper, we examine the shape effects of different nanoparticles of an incompressible, unsteady flow of a nanofluid ${\mathrm{\text{Al}}}_2{\mathrm{\text{O}}}_3$ with water ${\mathrm{\text{H}}}_2\mathrm{\text{O}}$ as the base fluid over a rotating disk. Magnetic field results are also added. In this research, four distinct shapes of ${\mathrm{\text{Al}}}_2{\mathrm{\text{O}}}_3$ nanoparticles, i.e., sphere, blade, cylinder and brick, have been employed. Every shape is suspended at the same volume. After using the Von Karman transformation, the Navier–Stokes equation, along with the magnetic field effect and the thermal energy equation, is numerically solved by using the bvp4c MATLAB solver. The effects of various parameters on the velocity field and temperature profile are illustrated graphically. This analysis is validated by comparing it to the previously described research. Furthermore, increasing the volume fraction parameter $0\le \varphi \le 0.1\%$ causes the radial, tangential, and axial velocities near the disk for the shapes brick, cylinder, and blade to decrease and increase for the shape sphere. The fluid rotating in front of the disk rotates more slowly for small values of the unsteadiness parameter $\widehat{\alpha }$. The magnetic field M has a significant influence on the axial flow when the suction parameter values are small, but this impact is limited when the suction parameter values are large.

We report on the synthesis and characterization of silicon nanoparticles by ablating silicon wafer in an ambient atmosphere of helium at 1 Torr. The mean cluster size ranging from 1.8 nm to 4.4 nm deposited on silicon substrate at room temperature is observed to depend on the laser fluence. The size of the nanoparticles decreases with laser fluence. Photoluminescence of the deposited films using Nd:YAG laser and Ar⁺ ion laser at 355 nm and 457.9 nm respectively shows emission peaks at 1.7, 2.2, and 2.7 eV. The luminescence peak at 2.2 eV and 2.7 eV are attributed to oxygen related impurities and the peak at 1.7 eV is attributed to quantum confinement.

We present a detailed study of the ferromagnetism in nano-Ni-doped SnO₂ and ZnO. It is shown that the ferromagnetic behavior is not an intrinsic property of the systems but rather associated with the presence of nNi particles in both matrices. The ferromagnetic transition of all Ni-doped samples is at 631(2) K, the same as the T_C value for bulk Ni and nano-Ni powder. The saturation moments of the nano-Ni-doped samples scale with the Ni concentration and are much lower than that of pure Ni. This is due to the large surface area of nano-Ni particles which are partially oxidized due to nano-NiO. ¹¹⁹Sn Mössbauer spectroscopy studies on Sn_0.96Ni_0.04O₂ do not show any transferred hyperfine field on the Sn nuclei, confirming that the magnetic properties stem from a different phase.

This article has been retracted. A statement of retraction is published in Mod. Phys. Lett. B Volume 28, Issue 26 (2014) http://dx.doi.org/10.1142/S0217984914930014

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Nanosize particles of barium hexaferrite were prepared by co-precipitation route using solution of iron and barium chlorides with a Fe⁺³/Ba⁺² molar ratio of 11. Water and a mixture of water/ethanol with volume ratio of 1:3 were used as solvents. Co-precipitated powders were calcined at various temperatures. XRD results showed that single phase barium hexaferrite forms at 900°C for sample synthesized in aqueous solution and its formation is resulted from the reaction between mainly crystalline phases, while this temperature decreased to 700°C for sample synthesized in water/ethanol solution and the formation of barium hexaferrite consists of reactions between amorphous phases with crystalline phases. SEM micrographs of the calcined samples at 800°C indicated that the morphology of particles was affected by the type of solvent. Nano size particles of barium hexaferrite with mean particle size of almost 80 nm were observed in the SEM micrograph of sample synthesized in water/ethanol solution after calcination at 800°C. Barium hexaferrite crystallites with mean size of 35 nm, which was approximately consistent with size obtained from XRD line broadening technique, could be seen in TEM image of this sample after calcination at 700°C.

Magnetite nano-particles have been synthesized by reverse co-precipitation method using iron salts in alkaline medium in the presence of diethylene glycol (DEG). Effect of DEG on the nano-particle characteristics was investigated by XRD, FE-SEM, FTIR and VSM techniques. From XRD results it was concluded that in the presence of DEG the composition of magnetite did not change, however the mean crystallite size reduced from 10 to 5 nm. SEM micrograph showed that DEG decreased the size of spherical magnetite nano-particles from 50 to 20 nm. Fourier transform infrared spectra (FTIR) indicated that the DEG molecules chemisorbed on the magnetite nano-particles. Under the given experimental conditions, the rate of crystallization and growth reduced, which is probably due to the capping of DEG to the magnetite nano-particles. The agglomeration was also decreased which is attributed to the coating of magnetite nano-particles by DEG which prevents the formation of hydrogen bonding between magnetite and water molecules.