Microfluidic Synthesis of Cobalt Nanoparticles

Abstract

Co nanoparticles with three different crystal structures were synthesized in a microfluidic reactor through manipulation of reaction times, flow rates, and quenching procedures. Cobalt nanoparticles of facecentered cubic (β) phase were obtained from a high flow rate of the reactants followed by in situ quenching of the reaction. hcp and -cobalt nanoparticles were obtained at a low flow rate of the reactants followed by in situ quenching and delayed quenching, respectively. The crystal structures were characterized using Co K-edge X-ray absorption near edge structure (XANES) spectroscopy, X-ray diffraction (XRD), and selected area electron diffraction (SAED). In situ XANES measurements on Co nanoparticles coming out of the outlet of the microfluidic reactor at different flow rates seem to indicate that the difference in flow rate influences the nucleation process in a critical way and that particle growth occurs mainly outside the reactor. The magnetic properties of the cobalt nanoparticles, measured using a SQUID magnetometer system, showed significant differences among the samples and are consistent with the three different crystal structures.

Application of alternative energy forms in catalytic reactor engineering

“…[36,48] . The 4 nm Co NPs with fcc, hcp and epsilon phases have blocking temperatures of -143 ° C, 1 ° C and 17 ° C, respectively [49] . After annealing, the coercivity of CoPt [50] , FePt [39,51] and FePd [35,50] NPs increases due to a transition from the disordered face-centered cubic (fcc) to ordered facecentered tetragonal (fct) structure.…”

Ion Beam Formation and Modification of Cobalt Nanoparticles

“…Co NPs can exist in either the hexagonal closed packed (HCP), face-centered cubic (FCC), body-centered cubic (BCC), or epsilon ϵ (similar to the β phase of Mn [13]) phases, the relative stability of which depends on the route of formation [17][18][19] host matrix [20][21][22] and thermal history [23,24]. Of these four phases, HCP has the highest coercive field [13,25] and is thus the most obvious candidate for ultrahigh-density recording applications. Co nanorods and nanowires also exhibit unique perpendicular magnetic anisotropy, coercivity, remanence, and activation volumes that are heavily dependent on the nanorod length (or equivalently, major diameter) [26].…”

Microfluidics-Nano-Integration for Synthesis and Sensing

“…Because of the anaerobic conditions, Cu nanoparticles are stable in the microfluidic environment. Another important application of microfluidic synthesis, the synthesis of nanoparticles with two or more crystalline phases, realized by Kumar et al is shown in the example below ( Figure 17) for cobalt nanoparticles [29]. Figure 17.…”