Submicron particles of Co, Ni and Co-Ni alloys

Abstract

Magnetic sub-micron sized particles (with diameters in the range 100-600 nm) of Co, Ni and Co-Ni alloys, protected with polyvinylpyrrolidone have been prepared in gram quantities using the polyol process. Experiments carried out with different metal precursors and starting compositions have yielded reliable routes to produce particles of the desired diameters in the 100-600 nm range. The particles were characterized with X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis and magnetic measurements. The particles are found to be stable under ambient conditions indefinitely. The coercivity values of the Co and Ni particles are ~ 50% higher compared to the corresponding bulk values. The alloy particles follow a trend similar to the bulk alloys.

Synthesis of nanocrystalline Co–Ni alloys by precursor approach and studies on their magnetic properties

“…The saturation magnetization of the Co-Ni nanoalloys falls in between that of pure bulk nickel and cobalt which are 54.4 emu/g [55] and 162 emu/g [56], respectively. The saturation magnetizations of Co-Ni alloys are known to vary with the concentration of cobalt, in Co-Ni alloy particles [30]. The M s values of the alloys in the present study are higher than that of pure nanocrystalline nickel.…”

“…Co-Ni particles useful for microwave applications with sub-micron size range have been synthesized by the polyol process by Viau et al [29]. PVP protected Co-Ni alloy nanoparticles have been prepared by the polyol process by Saravanan et al [30]. Freshly prepared cobalt (II) and nickel (II) hydroxides have been subjected to reduction in ethylene glycol to obtain Co-Ni powder by Bianco et al [7].…”

Nickel nanoparticles embedded in carbon foam for improving electromagnetic shielding effectiveness

“…The Ni nanoparticles were synthesized by the process reported literature (Saravanan et al 2001). The 1 g of nickel chloride hexahydrate (NiCl 2 Á6H 2 O) was dissolved in 100-ml ethylene glycol.…”

Novel Nanotrees of Crystalline Nickel formed via Electrolytic Approach

“…However, the M S value for the sample with PVP is less than that for without PVP due to the existant of non-magnetic PVP in the sample. It also can be found that the H C and M r values for these two sample are much higher than those for bulk nickel materials (100 Oe, 2.7 emu/g), which also can be attributed to their unique preferred orientation structures [22] and the reduced size as well as presence of hierarchical structures [7]. The less M S for these two samples compared with that for bulk nickel materials (55 emu/g) is mainly due to the spin disorder on the surface and surface oxidation [2].…”