Nickel Oxide (NiO) is an important transition metal oxide with cubic lattice structure. Among the magnetic nanoparticles, fabrication of nickel nanoparticles is often more difficult than that of the other particles. This is because they are easily oxidized. To achieve pure nickel nanocrystals, numerous methods have been conducted in organic environments in order to prevent formation of hydroxide or oxidation. In the present work, we report the synthesis of NiO nanoparticles. Magnetic properties of NiO nanoparticles with different sizes and at different temperatures are compared. The phase structures, particle sizes and magnetic properties of NiO nanoparticles have been characterized by X-ray diffraction, TEM images and Vibrating Sample Magnetometer (VSM). We collected the experimental data reported in the literature, for the same conditions, and after fitting, extrapolating and doing some calculations. The magnetization for smaller nanoparticles is bigger for the samples we consider here. This difference could be explained by the difference of surface volume ratio of nanoparticle which shows the contribution of the paramagnetic surface is more important with respect to the anti-ferromagnetism of the core for smaller particles. Also the nanoparticle at lower temperatures shows bigger magnetization.
As we know there is a fairly big difference between the physical properties of the bulk and nanoparticles, and also among nanoparticle themselves, for the same matter [
Magnetic nanoparticles are widely used in conductive colors [
Nickel is one of the transitional metals that has a magnetic property in relation with its bulk state and thus has interesting applications and properties such as hydrogen storage and catalytic properties. Using various methods such as electrochemical reduction [
Among the magnetic nanoparticles, fabrication of nickel nanoparticles is often more difficult than that of the other particles. This is because they are easily oxidized. To achieve pure nickel nanocrystals, numerous methods have been conducted in organic environments in order to prevent formation of hydroxide or oxidation. Zhang et al. have prepared Ni nanocrystals with a diameter of 20 - 60 nm through degradation of nickel acetyl acetonate in oleyl amine [
Among the majority of advanced technologies for fabrication of nickel nanoparticles and nickel oxide, the thermal degradation is a new method for synthesis of mono-disperse and stable nanoparticles. In comparison with conventional methods, it is far quicker, cleaner, and more environmentally friendly, and through the thermal reduction process it should be optimized for fabrication of nickel nanoparticles with different sizes and shapes, since the shape and size for particles influence its application and properties.
In this method, metal nanoparticles and the metal oxide have been prepared through thermal degradation of the metal-surfactant complex in a hot surfactant solution. This method is schematically shown in
We produced NiO nanoparticles with particle diameters 25 - 100 nm. We observed a phase transition at 38 and a coercively as high as 700 Oe at 10 K, although the bulk is anti-ferromagnetism.
Lopez and co-workers [
The XRD pattern of nickel nanoparticles in
Nickel oxide nanoparticles were formed following the exposure of nickel nanoparticles to air after around 55 h. The XRD pattern of these particles is in the form of
The images of Transmission Electron Microscopy (TEM) are shown in
The magnetic properties of nickel nanoparticles are depicted in
In
These differences could be explained by the difference surface volume ratio of nanoparticles which means the contribution of the paramagnetic or the effect of spines on the surface (it means: the spins increase as the particle size decreases) is more important with respect to the anti-ferromagnetism of the core for smaller particles.
In
Fardin Taghizadeh, (2016) The Study of Structural and Magnetic Properties of NiO Nanoparticles. Optics and Photonics Journal,06,164-169. doi: 10.4236/opj.2016.68B027