The Preparation And Properties Of FeCo Nanoparticles And Their Composites

With the widespread use of electromagnetic waves in the gigahertz range,metallic magnetic materials have attracted wide attention due to their higher complex permittivity.Iron-cobalt?FeCo? alloy as an excellent soft magnetic material which has high saturation magnetization,low magnetostriction,small magnetic coercive force and high Curie temperature,is applied in many fields such as aerospace,absorbing materials and others.In this paper,three FeCo particles with different iron-cobalt contents(Fe_0.7Co_0.3,Fe_0.5Co_0.5 and Fe_0.3Co_0.7)were synthesized by liquid-phase reduction method through changing the amount of raw materials added.Then we prepared a series of PANI@FeCo with different proportions by polyaniline?PANI?in-situ polymerization and compared their microwave absorption properties with PANI@FeNi.To further study of their properties,composites using epoxy as matrix and FeCo nanoparticles and PANI@FeCo as fillers were prepared.The main work is summarized as follows:Three FeCo particles with different iron-cobalt contents were prepared by liquid-phase reduction method through changing the amount of raw materials added and the surface element ratios were characterized by XPS.TEM was utilized to characterize the morphology of the FeCo particles and XRD was utilized to characterize the crystal structure of the FeCo particles.The size of the FeCo nanoplates is about 100-200nm and the thickness is about 25nm.The FeCo presents cubic crystal and we find there is no oxide in FeCo37.The results of VSM analysis shows that the coercive force of FeCo73 is 549.68370e,the saturation magnetization is 17.771emu/g;the coercive force of FeCo55 is 124.611Oe,the saturation magnetization is 140.442emu/g;the coercive force of FeCo37 is 124.707Oe,the saturation magnetization is 180.198emu/g.A series of PANI@FeCo absorbing materials were prepared by PANI in-situ polymerization.The PANI@FeCo ratios were 90%,70%,50%,and 30%,respectively.PANI tends to form an interwoven network structure in the composite material,and the sheet structure of FeCo is distributed on the surface of PANI.Through XRD test,we discover a successful combination of polyaniline and FeCo nanoparticles,and polyaniline exhibits semi-crystalline properties.The PANI@FeCo were mixed with paraffin in a ratio of 2:3,and the wave absorption performance was tested.It is found that the overall wave absorption performance of the PANI@FeCo series are not good,and among the three series,the PANI@FeCo37 performs better.When PANI@FeCo37=90%,the lowest reflection loss is-13dB,and the absorption bandwidth less than-10dB is 2GHz.And then we compared PANI@FeCo with PANI@FeNi.It is found that the dielectric losses of PANI@FeCo series are lower than that of PANI@FeNi,making the microwave absorbing properties is worse than PANI@FeNi.Composites using epoxy as matrix and FeCo nanoparticles and PANI@FeCo as fillers were prepared.SEM images showed the section morphology of the FeCo/Epoxy.LCR,tension test and TG were used to characterize the dielectric properties,mechanical properties and thermal properties of the composites.We find that the add of FeCo reduces the dielectric constant of epoxy while the add of PANI@FeCo improves the dielectric constant of epoxy;both the add of FeCo and PANI@FeCo toughen the epoxy resin;and the add of FeCo nanoplates and PANI@FeCo has no significant effect on thermal properties.