Direct synthesis of submicron FeNi particles via spray pyrolysis using various reduction agents

Abstract

Preparing spherical and submicron FeNi particles in a simple, rapid, and harmless process is highly desirable for various applications yet severely challenging. Herein, we successfully synthesized the FeNi particles from their metal salts in a relatively low reduction atmosphere using three types of reduction agent, i.e., ethanol, ethylene glycol, and formic acid, via spray pyrolysis. The reduction agents were tested over a concentration range of 0–30 vol%. The type and concentration of reduction agents show a crucial role in the formation of FeNi particles. At higher concentrations (25 vol%), ethanol and ethylene glycol produced smooth and spherical FeNi particles of submicron size, 284 ± 1.6 and 399 ± 1.5 nm respectively, whereas formic acid produced particles with an irregular and Janus shape comprising FeNi and FeO, with a size of 396 ± 1.5 nm. A plausible metal salt reduction mechanism was proposed for the different reduction agents. The reduction agent type not only influences the reduction degree but also particle morphology during synthesis. This finding opens new opportunities to adjust the FeNi particles with respect to varied purposes by manipulating reduction agents.