Effect of element infiltration on radial composition/structure and magnetic/electrical properties of Fe-B amorphous powders prepared by spark erosion

Abstract

Before confirming spark erosion as an effective technique for producing Fe-based amorphous powders, it is crucial to thoroughly investigate their magnetic/electrical properties and the impact of different elements infiltration on composition, microstructure, and performances. Limited research has been conducted on the magnetic and electrical properties of spark-eroded Fe-based amorphous powders, and there is a dearth of studies on the influence of different elements' infiltration. In this work, a series of binary Fe83B17 amorphous powders were synthesized using water (as a source of O), ethanol (as a source of C and O), and silicone oil (as a source of O, Si, and C). The elements O, C, and Si exhibit different concentration distributions along the radial direction in the synthesized powders. The depth of O infiltration varies between 10 to 35nm, C from 190 to 280nm, and Si barely diffuses inward. For powders prepared in water (WF), the formation of nanoclusters throughout the particle leads to an improved saturation magnetization. Besides, the infiltrated mass ratio of O is merely 1.38wt.% and is predominantly concentrated in the surface of WF powder, resulting in a significant increase in resistivity. The resistivity of WF powder is approximately four orders of magnitude higher compared to powders prepared in ethanol (EF) and silicone oil (SF). Nanoclusters are also observed in EF and SF powders, where the significant infiltration of non-magnetic C leading to a reduction in the saturation magnetization of both EF and SF powders. Inside EF powder, a remarkable peak of C content appears at ~30nm away from the powder surface in the radial direction, accompanied by an increase in structural order. This suggests a synchronous relationship between the variations of structural order in the radial direction and the concentration of the infiltration element. These findings demonstrate the practical feasibility of tuning composition and microstructure via dielectrics to develop high-performance Fe-based amorphous powders.