Papers by Keyword: Cobalt Nanoparticles

Abstract: Magnetic cobalt nanostructured was synthesized by a two-stage method. First, a solution of cobalt precursor droplets was prepared by an ultrasonic nebulizer. Second, the arc discharge method between two electrodes in an inert gas at atmospheric pressure is used to obtain the nanostructured cobalt powder. The sample obtained was characterized by X-ray diffraction (XRD). Scanning electron microscope (SEM), High Resolution Transmission Electron Microscope (HR-TEM), UV-Vis Spectrophotometry, zeta potential (ZP) and vibrating sample magnetometer (VSM). The dielectric constant, and AC conductivity of the prepared sample was determined in the frequency range of 4 Hz to 8 MHz. The investigations showed that the Co nanoparticles prepared in this way have smaller and homogeneous nanoparticles with spherical shape morphology with good stability and unique magnetic properties as compared with the bulky one. The dielectric properties analysis shows an enhancement in the dielectric constant and the AC conductivity of the Co nanoparticles.

Abstract: The article presents the influence of biopreparations containing nanoparticles of cobalt and cuprum on the physiological state of Holstein heifers in a case of adding them to the diet. We have studied parameters of the animals’ growth and development in dynamics of live weight gain, clinical and biochemical blood parameters, the leucogram and amino acid composition of the experiment animals’ blood during the experiment.

Abstract: A series of Er³⁺ doped phosphate glass embedded with CoO nanoparticles (NPs) were synthesized from high purity raw materials by melt quenching and the influence of CoO NPs on the optical absorption were investigated. The glass has been characterized by means of TEM and UV-Vis Spectroscopy. Investigation on TEM image displays the existence of NPs where its distribution is Gaussian with the average size of 5.18 nm. Five absorbtion bands of erbium were evidenced in the UV-Vis measurement. For UV-Vis absorption peaks, the optical band gap energy, E_opt has been estimated in the range of 3.22 3.89 eV, increasing with the increasing of CoO content. Meanwhile, the urbach energy is found to be in the range of 0.98 0.74 eV decreasing with the CoO content. All the results will be discussed with respect to CoO content.

Abstract: In the present study, Cobalt nanoparticles were synthesized and mixed with Sn-3.0Ag-0.5Cu solder (SAC305). The effect of 0.05 wt.%, 0.2 wt.%, 0.5 wt.% and 1.0 wt.% Co nanoparticles on the wettability, the shear strength as well as the growth of intermetallic compounds (IMCs) at composite solder/Cu interface during thermal cycling were investigated. Results show that Co nanoparticle addition can considerably improve wettability, increase the shear strength and suppress the growth of interfacial IMCs. The addition amount of Co nanoparticles have the consistent relation with the improvement extent of the wettability, shear strength and the growth rate of interfacial IMCs. Slight addition (0.05 wt.% and 0.2 wt.%) can significantly improve the properties of nanocomposite solder in all the three aspects. However, with excessive addition amount (0.5 wt.% and 1.0 wt.%) of Co nanoparticles, the improvement extent will decline. The Cross-section images of the interface of nanocomposite solder/Cu joint show that Co can form reinforcement particles in the solder and can act as the sacrificial element to substitute Cu to react with Sn. Excessive Co nanoparticles would form large amount of hard and brittle intermetallics which leads to decreasing shear strength of the composite solder.

Abstract: Metallic cobalt (Co) nanoparticles with mean diameters in the range of 50-500 nm are formed by electroless deposition at room temperature in the presence of increasing concentration of NaOH. Co deposition was investigated by in situ mixed potential measurement. Increasing concentration of NaOH shifts the mixed potential negatively, leading to faster Co deposition and smaller apparent particle diameter. The decrease in mixed potential with increasing NaOH concentration is attributed to the decrease in the activity of Co²⁺ aquo ions in equilibrium with Co (OH)₂. Consenquently, the oxidation-reduction potential of Co (II)/Co redox pair is reduced. This leads to more negative mixed potential.

Abstract: Co and Ni nanoparticles were fabricated in fused silica plates by ion implantation technique. Electron microscopy showed the nanoparticles to be of spherical shape. Magnetic circular dichroism (MCD) was investigated in the spectral range 1.2 - 4.2 eV in a field of about 3 kOe. MCD spectra are considerably different from the spectra of thin nickel and cobalt films. MCD spectra for Ni nanoparticles are associated with surface plasmon resonance.

Abstract: In this study, cobalt nanoparticles with an average size of 16 nm were synthesized using cobalt-acetate as precursor. Besides oleylamine and oleic acid, sodium oleate was selected as surfactants to control the size of particles. The obtained particles show cubic shape and uniformly disperse. The hysteresis curve of cubic nanoparticles detected by vibrating sample magnetometer (VSM) reveals that the coercive force Hc is 297.62 Oe and the saturation magnetization Ms is 56.55 emu/g.

Abstract: Metallic cobalt nanoparticles are successfully obtained by the pyrolytic decomposition of CoC₂O₄ . 2H₂O in the argon gas. The pyrolysates of CoC₂O₄ . 2H₂O were investigated by TG-DSC and SEM. The results showed that there are two stages in the process of the pyrolytic decomposition of CoC₂O₄ . 2H₂O in the argon gas. The crystal water in CoC₂O₄ . 2H₂O was lost from 150 °C to 275 °C. CoC₂O₄ was pyrolysized into metallic cobalt powder from 300 °C to 500 °C. At the same time, the pattern of pyolysate of CoC₂O₄ . 2H₂O was fined at 347.7 °C for 10 min. But, the particles of pyolysate of CoC₂O₄ . 2H₂O were sintered into cobalt blocks at 500.0 °C for 10 min. Therefore, the conditions of pyrolytic decomposition of CoC₂O₄ . 2H₂O were controlled if single cobalt powder was obtained at 500.0 °C..

Abstract: The electrodeposition of cobalt nanoparticles from mixture of 1-butyl-3- methylimidazolium chloride (BMIC) ionic liquid and urea was investigated. The results from the cyclic voltammetry (CV) show that the reduction of Co(II) to cobalt is an irreversible process and controlled by the diffusion of Co(II) on Pt working electrode. The cobalt nanoparticles prepared by direct current (DC) electrodeposition method at 70 °C were characterized by scanning electron microscope (SEM). Test results indicate that the Co nanoparticles are grain-like arrays and link together because of their magnetic property. The average length of these particles is about 100 nm.

Abstract: Agglomerated cobalt magnetic nanoparticles coated with carbon, dispersed in a paraffin matrix, were prepared and investigated by FMR (ferromagnetic resonance) at room temperature. Four samples with different C/Co content, ranging from 0.175 to 1.011, dispersed at low concentration in paraffin were investigated. Very intense and broad FMR spectra with different intensities, line widths and positions of the resonance fields were recorded for the samples. A strong dependence of the FMR signal intensity and resonance on the concentration of magnetic nanoparticles was observed. Various magnetic interactions affecting the observed FMR spectra have been analyzed. It was found that with increasing concentrations of magnetic nanoparticles the magnetic dipole interaction between the agglomerates plays a more important role.