Electric field-assisted levitation-jet aerosol synthesis of Ni/NiO nanoparticles

Abstract

Ni/NiO powdered nanoparticles with average sizes 10-30 nm were prepared by a levitation-jet method involving the condensation of Ni metal vapour in a mixture of helium with various amounts of air or oxygen. The process was undertaken with the application of a DC electric field up to 6.5 kV cm À1 . The particles were characterized by X-Ray diffraction, transmission electron microscopy, BET adsorption and vibrating sample magnetometry. It was found that the intensity of the applied electric field and partial oxygen pressure correlated with the main structural and magnetic parameters of the nanoparticles, such as average particle size, residual ratio of nickel, coercivity and maximum magnetisation. The specific surface area of the particles correlated with the magnitude of the external electric field. Room-temperature hysteresis loops of weakly oxidized nanoparticles show ferromagnetic-like behaviour, whereas the strongly oxidized ones exhibit a low-field ferromagnetic feature superimposed to a paramagnetic signal, regardless of the particle size. Magnetic measurements allowed for the estimation of the residual metal Ni content in the powdered nanoparticles, which can be as low as 0.04 at.% depending on oxygen partial pressure and external electric field strength.

Strain Recovery and Defect Characterization in Mg‐Implanted Homoepitaxial GaN on High‐Quality GaN Substrates

“…Apart from that, the high‐resolution TEM image in Figure also showed some Moiré fringes. They are formed by the superposition of two lattice planes that are similar in d‐spacings but slightly misoriented . In this sample, the fringes could be generated by other extended defects, such as dislocations, causing local distortions in the lattice.…”

Structural, optical, XPS and magnetic properties of Zn particles capped by ZnO nanoparticles

“…1c), the synthesis process takes place under essential oxidizer content in the net gas flow (Table 1). That time-limited the condensation zone [38,41] and in result Zn and ZnO as it may see in the fig. 1c probably form the separate nanoparticles, with the latter became a tetrapod-shaped [49] and the abovementioned Zn/ZnO capped morphology be non-obvious.…”

57Fe Mössbauer study of NiFe2O4 nanoparticles produced by the levitation-jet aerosol technique

“…The studied aerosol-generated NiFe2O4 NPs were synthesized by using a one-stage dry levitation-jet process in presence of an applied DC electric field, which was described in detail elsewhere [12][13][14]. In this technique a piece of metallic nickel wire (1 g) was wound around an iron wire in a volume ratio of Ni:Fe = 1:2 and suspended in a quartz tube with an inner diameter of 14 mm.…”

“…During the synthesis process, an electric field was applied to the condensation/cooling zone near the levitating droplet as well as in a transverse direction to the gas flow by means of two thin tungsten rods, anchored outside the quartz tube, which generated a DC electric field between 0 and 210 kV/m. Such geometry allows the electric field to act over a cooling zone and provides crystallization of metal vapor into nanoparticles [12].…”