Spheroidization of Nickel Powder and Coating with Carbon Layer through Laser Heating

Abstract

We developed a simple and efficient process, laser heating of nickel powder in ethanol, to produce carbon-encapsulated nickel microspheres. Long-pulse-width laser heated nickel powder suspended in pure ethanol into liquid droplets. In turn, the latter droplets became sphere-like, pyrolyzed surrounding ethanol and dissolved the produced carbon atoms. Because of their lower solubility in solid nickel, excess carbon atoms were then expelled from the metal core after solidification, thus forming graphite-like shells on the laser-modified Ni spheres. Hence, after pyrolysis the transformation of carbon was found to follow the dissolution-precipitation mechanism. The produced carbon-encapsulated nickel microspheres exhibited higher oxidation resistance compared with the initial nickel powder, while keeping their magnetic properties essentially unchanged.

Laser Synthesis of Iridium Nanospheres for Overall Water Splitting

“…Nd:YAG laser (Dawa-350, Beamtech, Beijing, China) was operated at wavelength 1064 nm, pulse width 7 ns, single-pulse energy 250 mJ, and frequency 15 Hz. More details about this preparation approach can be found elsewhere [30,31,32,33,34,35]. More specifically, an Ir plate (30 mm × 30 mm × 3mm, 99.99%) was first polished by sandpaper to remove the surface oxide layer, followed by rinsing with deionized water.…”

“…Herein, we employed a physical method, pulsed laser ablation in liquid (PLAL) [30,31,32,33,34,35,36,37,38,39,40,41,42] to produce Ir nanospheres (Ir NSs) enriched with surface atomic steps. This method is known as an efficient approach for preparation of various metallic nanoparticles [30,31,40,41,42], including those for electrocatalysis [40,41,42].…”