Impact of nanoparticle magnetization on the 3D formation of dual-phase Ni/NiO nanoparticle-based nanotrusses

Abstract

Magnetic nanoparticles with average size 30 nm were utilized to build three-dimensional framework structures-nanotrusses. In dual-phase Ni/NiO nanoparticles, there is a strong correlation between the amount of magnetic Ni and the final size and shape of the nanotruss. As it decreases, the length of the individual nanowires within the trusses also decreases, caused by a higher degree of branching of the wires. The position and orientation of the non-magnetic material within the truss structure was also investigated for the different phase compositions. For lower concentrations of NiO phase, the electrically conducting Ni-wire framework is maintained through the preferential bonding between the Ni crystals. For larger concentrations of NiO phase, the Niwire framework is interrupted by the NiO. The ability to use nanoparticles that are only partly oxidized in the growth of nanotruss structures is of great importance. It opens the possibility for using not only magnetic metals such as pure Ni, Fe, and Co, but also to use dual-phase nanoparticles that can strongly increase the efficiency of e.g. catalytic electrodes and fuel cells.

Magnetically Collected Platinum/Nickel Alloy Nanoparticles as Catalysts for Hydrogen Evolution

“…The individual nanoparticles are relatively uniform with a size range of 15–25 nm and predominately spherically shaped. The only non-spherical deviation is particles featuring protruding triangular features, which have been identified in the past as NiO domains . The HRTEM images in Figure e,f show that the particles consist of a metallic core surrounded by a thin oxide shell.…”

“…The only non-spherical deviation is particles featuring protruding triangular features, which have been identified in the past as NiO domains. 35 The HRTEM images in Figure 2e,f show that the particles consist of a metallic core surrounded by a thin oxide shell. The XPS data in Figure S3a,b provides further support for this conclusion, and after fitting the Ni 2p 38 and Pt 4f peaks, 39 we find that the vast majority of the detectable Ni (97%) is oxidized, whereas 45% of Pt is oxidized.…”

“…As shown in an earlier work, the possibility to collect nanoparticles using the magnetic collection technique requires sufficient magnetic properties of the nanoparticles. 35 To determine the limit for magnetic collection of the Pt x Ni 1−x nanoparticles, XRD investigations were used. Figure 1a depicts that for magnetically collected samples (black curves), no peaks can be seen for x = 0.50.…”

“…All of these parameters are presented in the process conditions table (Supporting Information, Table S1). The substrates are placed on top of a magnet in order to collect the nanoparticles magnetically, as explained in an earlier work. − However, unlike the previous works, the magnet used here is a permanent cube magnet made from NbFeB with a 7 mm side. This makes the magnetic flux density at the center of the magnet significantly stronger compared to that in the earlier work. − This results in a more efficient collection of nanoparticles.…”

Epitaxy of oxide and nitride thin films grown by magnetron sputtering

“…The variation in stoichiometry changes the material characteristics and is useful for a wide range of applications. NiO has been studied for its magnetic [20], electronic [21], thermoelectric [16], and optical [22,23] properties as well as chemical resistance. NiO, as a p-type transparent conductor is a candidate for electrochromic devices such as inorganic smart windows [24].…”