Composition and Morphology Investigation of NiCoB Nanoparticles, as-Prepared and Coated by SiO2

Abstract

Abstract. NiCoB nanoparticles, as-prepared and coated by SiO 2 , were synthesized by chemical reduction of metallic salts. The as-prepared samples were additionally annealed at 650 for 1 hour in argon atmosphere. All samples (the as-prepared and annealed ones) were investigated by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). According to FE-SEM observations each of the investigated samples was composed of nearly spherical nanoparticles with average dimension smaller than 30 nm. Also, tendency of formation of irregular agglomerates was present in both cases of the as-prepared and annealed investigated samples. XRD measurements of as-prepared samples revealed fully amorphous structure. In case of annealed samples, crystallization of different phases was confirmed (as a consequence of heat treatment at 650 C). The existence of these phases was also observed from FE-SEM micrographs as different morphologies present in the samples.(doi: 10.5562/cca2234)

Microstructural Features of Magnetic NiCoB Nanoparticles Addition to MgB2 Precursor Powders

“…[14] It should be mentioned that the amounts of ethanol solutions of metallic salts Ni(NO3)2 and CoCl2, along with the one of water solution of reducing agent KBH4, were adjusted to yield the nominal composition NiCoB nanoparticles (NP). Then the mixture of (1 -x)Mg : xNP : 2B with x = 0.01 was prepared, which corresponds to 2.67 w. % of NiCoB nanoparticles.…”

“…This could explain somewhat larger sizes in case of CoNi agglomerates from literature, [28] Table 4. Also, the measured mean size of bigger spherical agglomerates from Figure 3 (c), corresponds to the one observed for smooth spherical agglomerates in annealed sample with NiCoB nanoparticles from our previous work 14 , Table 4, which were mostly composed of Co and Ni. These agglomerates were also formed as a consequence of annealing at 650 C, but their quantity was too small to be identified with certainty as CoNi agglomerates by XRD.…”

“…Very small amount of detected Cl ((E(Kα1)) = 2,622 keV) is explained as a remnant from synthesis of NiCoB particles (due to the CoCl2 metallic salt used in the preparation procedure). [14] Quantitative EDS analysis of the region shown in Figure 7 (b) indicates the presence of MgB2 and MgO, along with some amount of unreacted Mg. Small amount of detected Co and Ni, with molar Co:Ni ratio close to 1 : 1, indicates the presence of CoNi, as well. This is in very good agreement with earlier XRD observations ( Figure 1; Table 1).…”

“…[13] In this work we used nickel-cobalt-boron (NiCoB) nanoparticles which were earlier synthesized by chemical reduction of metallic salts (the details on the synthesis route can be found in previous work). [14] NiCoB particles were nearly spherical with the amorphous structure [14] and magnetic properties favorable for achieving magnetic flux pinning in MgB2: they have single domain magnetic structure with blocking temperature below room temperature (i.e. they are superparamagnetic at room temperature, which is preferable to avoid agglomeration of particles during mixing of Mg, B and NiCoB powders), considerable saturation magnetization and low coercive field at low temperatures.…”

“…This is explained with some amount of oxygen pollution present in the media of inert gas. [27] Water used in preparation procedure of asprepared sample with NiCoB nanoparticles [14] could also act as a source of oxygen, due to incompletely removing from starting solutions through the argon bubbling. On the basis of previous result published by some of the authors from this work (M. M and Ž. S., Ref.…”