Fine crystal structure transition of cobalt nanoparticles formed in a microfluidic reactor

The X-ray diffractions of cobalt nanoparticles synthesized by a microfluidic reactor process at low temperature suggest glasslike phases with only one broad peak. An X-ray absorption fine-structure (XAFS) technique is used to investigate fine crystal phase transition or changes in atomic arrangement and interatom spacing, during the Co nanoparticle formation by the microfluidic reactor process. The results indicate that the dynamic energy and retention time in microfluidic channels, and Ostwald ripening and quenching processes will affect the atom arrangement and the interatom spacing significantly. The hierarchies of surface energies for the main cut planes in different Co crystal structures can be used to elaborate these effects very well. The atom rearrangement and the interatom spacing shift during the nanoparticle formation are very important in the control of the nanoparticle properties via microfluidic processes, particularly for those sensitive to their fine crystal structures, such as magnetic and optical properties.