The present work addresses the synthesis and characterization of crystalline cobalt nanoparticles produced through a modified polyol-process conducive to the controlled formation of magnetic soft-Co structures with potential for applications in biomedicine. XRD characterization evidenced the influence of oleate and acetate species on the formation and crystal growth-inhibition of crystalline fcc-Co with controlled average crystallite sizes in the 8–10nm range. Magnetic measurements confirmed the strong influence of synthesis conditions on crystal structure and hence, on magnetic properties. As-synthesized nanoparticles exhibited coercivity values below 100 Oe and magnetization as high as 155 emu/g at room temperature. These values agreed with the soft magnetic nature of the fcc-Co phase.

Applications of elemental cobalt are consequence of its phase-dependent magnetic properties; the anisotropic high-coercivity hcp-Co phase is preferred for permanent magnet applications, while the more symmetric low coercivity fcc- and pseudocubic ε-Co can be used in soft magnetic applications involving power electronics and magnetic write heads. The present work addresses the synthesis and characterization of nanocrystalline cobalt particles produced through a modified polyol-based approach conducive to the formation of fcc-, hcp-, or ε-Co phases. Metastable ε-Co and hcp-Co were exclusively formed in the presence of trimethylene glycol. In turn, fcc-Co or mixture of fcc/hcp-Co phases were produced in tetraethylene glycol. The average crystallite size in all cases ranged between 10 and 13 nm. Magnetic measurements confirmed the strong influence of synthesis conditions on crystal structure and hence on magnetic properties of nanocrystalline cobalt. The coercivity of the products varied from 338 to 550 Oe depending on the presence of the different cobalt structures.

Articles you may be interested inFacile synthesis of single-phase spherical α″-Fe16N2/Al2O3 core-shell nanoparticles via a gas-phase method

No abstract

Nanofluids, consisting of nanometric particles suspended in a base fluid, have become a new alternative for improving heat management technology. Silver, which is known to exhibit pretty high electrical and thermal conductivity among metals, has been selected for this research. At present, we are focused on the study of the size- and shape-controlled synthesis conditions of silver nanocrystals in polyol media. Control of crystal size and shape at the nanoscale were achieved by suitable selection of the synthesis conditions and the presence of habit-controlling agents like chloride ions. Silver nanostructures (faceted crystals, wires, rods) were remarkable monodisperse in size and their dimension could be controlled in the 30-50nm range (particles) and 24-127nm in thickness for rods or wires.