Synthesis and characterization of ultrafine Ni–Co composite powder by freeze-drying

This research focused on the synthesis of ultrafine Ni–Co composite powder prepared using a freeze-drying technique. In the process of freeze-drying, the Ni–Co powder was prepared by freeze-drying the precursor from simple NiC2O4 and CoC2O4 powders. Thermal decomposition of the amorphous freeze-dried precursor powder produced the ultrafine Ni–Co composite powder. To assure process control and product characterization, the freeze-dried precursor and the final products were analyzed by means of XRD, SEM, TEM, and IR. The results showed that the freeze-dried powder existed in a non-hygroscopic and non-crystalline state. The final product of the experiments was a Ni–Co composite powder, which existed in the form of a single crystalline state and represented fine, homogeneous, spherical particles, reaching a size range of approximately 40–70 nm. The freeze-dried powder was composed of [Ni(NH3)6]2+ and [Co(NH3)6]3+.