Process optimization and properties of magnetically hard cobalt carbide nanoparticles via modified polyol method

Abstract

Cobalt carbide magnetic nanoparticles were successfully synthesized via a modified polyol process without using a rare-earth catalyst during the synthesis process. The present results show admixtures of Co 2 C and Co 3 C phases possessing magnetization values exceeding 47 emu/g and coercivity values exceeding 2.3 kOe at room temperature. Moreover, these experiments have illuminated the important role of the reaction temperature, hydroxyl ion concentrations and the reaction duration on the crystallographic structure and magnetic properties of the nanoparticles. The crystallographic structure and particle size of the Co x C nanoparticles were characterized by Xray diffractometry and scanning electron microscopy. Vibrating sample magnetometry was used to determine magnetic properties. Scale-up of synthesis to more than 5 grams per batch was demonstrated with no significant degradation of magnetic properties.

Polyol-Made Spinel Ferrite Nanoparticles—Local Structure and Operating Conditions: NiFe2O4 as a Case Study

“…Short polyol-mediated reduction reactions inhibit complete diffusion of carbon into the metal lattice and result in metal or metal carbide core-shell structures. Reversely, long reactions favor carbide stabilization instead of metal phase (Fujieda et al, 2012;Zamanpour et al, 2015;Fujieda et al, 2016), particularly if both the metal and the intermetallic crystallize in the same space group.…”

Investigation of fabrication of Mn-Ga-Al/Fe-Co nanocomposite hard magnetic materials

“…In comparison with other rare earth-free hard magnetic materials, our Mn-Ga-Al/Fe-Co nanocomposite magnets have moderate magnetic parameters. For examples, the Co-C based hard magnetic phases (Co 2 C, Co 3 C, …) have H c of about 3 kOe [27,28], the Hf-Co based ones (HfCo 7 , Hf 2 Co 11 B, …) have H c of about 4.5 kOe [29,30]. The maximum energy product of these rare earth-free hard magnetic materials is commonly less than 5 MGOe.…”

Getting Rid of Critical Raw Materials in Hard Magnets: Is it Feasible?

“…2) Cobalt carbide: Co-C Cobalt carbides were obtained in the 1960s by decomposing an organometallic precursor. They have recently been identi-fied as potentially hard and have been the subject of studies using the polyol route [24], the problem being that the material obtained is often composed of a mixture of Co 2 C and Co 3 C, the first having a rather weak magnetization. The ratio of these two phases can be controlled [25], but it is necessary to make a compromise between the coercive field of Co 2 C (300 kA/m) and the magnetization of Co 3 C (120 Am 2 /kg).…”