Influence of heat treatment on the microwave absorption properties of Flaky Carbonyl Iron Powder

Abstract High-energy ball milling is a very common method to produce materials with high magnetic permeability due to its ability to produce flaky shape particles on the nano-scale. It is an efficient technique to improve microwave absorbing properties. Therefore, this study aims to achieve an ideal microstructure and improve microwave absorption properties of flake carbonyl iron powder fabricated by high-energy ball milling. The influence of pre-heating at different times/temperatures on magnetic absorbing properties is also investigated. Further, the relationship between heat treatment temperature, permeability is analyzed. Microstructural analyses reveal that the phase of the material does not change with the change of pre-heating temperature. However, the material made by ball-milling has a finer grain size and a higher flattening ratio. The results show that the length to diameter ratio of the flake material can be increased by pre-heating, and thus improve the magnetic permeability and absorbing performance of the material. The optimal parameters of pre-heating are obtained at the temperature and time of 200 °C and 2 h, respectively, wherein the real part of the permeability reaches up to 3.20 at 2 GHz, the imaginary part reaches 1.61 at 6.2 GHz.