Preparation and Reaction Process of Nd2Fe14B Magnetic PowderSynthesized by Chemical Method

Abstract:

The NdFeB magnetic powder with main phase Nd₂Fe₁₄B was successfully prepared by using the chemical method to prepare NdFeB intermediates and then through two-step reduction annealing. Phase, microstructure, phase transformation of different temperatures and magnetic properties of the samples were analyzed with XRD、TEM、DSC、VSM and so on. The formation mechanism of Nd₂Fe₁₄B phase was discussed. The results show that the nano-sized NdFeB intermediates with good dispersion, including spherical Fe₃O₄ particle and flocculent organic ligands consisting of Nd and B elements, can be synthesized by chemical method. In order to obtain NdFeB magnetic powder, the intermediate should be performed two-step reduction annealing. In the first-step reduction annealing process, NdFeB intermediates were converted into NdFeO₃, B₂O₃, Nd₂O₃ and α-Fe phases. During the second-step annealing was carried out by CaH₂, the reaction experiences following processes: firstly, B₂O₃ is reduced at 501 ℃.Then, Nd₂O₃ and NdFeO₃ are reduced into NdH₂ and α-Fe phases at 678 ℃. Finally, B、NdH₂ and α-Fe are alloying reaction to formed Nd₂Fe₁₄B magnetic powder at 895 ℃.

Key words:chemical method;ligand; reduction annealing; Nd₂Fe₁₄B; magnetic powder