Surface treatment of reduced iron powder with amino trimethylene phosphonic acid and inorganic synergists for high saturation magnetization and low-loss soft magnetic composites

Abstract

With the development of electronic power equipment towards lightweight and miniaturization, higher requirements are placed on the performance of soft magnetic composites (SMCs), such as high saturation magnetization and extremely low losses. In this study, amino trimethylene phosphonic acid (ATMP), ZnCl₂, and Na₂MoO₄ were utilized to co-treat the reduced iron powder. Zinc chloride and sodium molybdate significantly improved the film-forming ability of ATMP., resulting in the formation of a coating on the reduced iron powder surface. The treated powder, compared to untreated iron powder, exhibited significantly increased resistivity and effectively reduced losses. The results suggested that the magnetic molybdate inside the coating inhibited the reduction of saturation magnetization. In addition, the impact of treatment duration on the microstructure and electromagnetic properties of the SMCs was also investigated. The results demonstrated that the iron powder treated for 60 min formed the most uniform and dense coating, resulting in an optimal loss reduction of 262.5 mW/g (50 mT, 100 kHz), which is a 75.9 % decrease compared to the untreated sample, with a saturation magnetization of 210.23 emu/g. This study offers a feasible green and economical approach for the industrial production of SMCs.