| Electromagnetic wave signals from electronic devices can affect people’s health and the development of high-performance electromagnetic wave absorbing materials is the key to solving such problems.Metallic materials are the most common electromagnetic absorbing materials,but their high density,large volume,perishability and narrow absorption bandwidth limit large-scale applications.Multielemental nanoparticles have superior magnetic properties,corrosion resistance and energy conversion properties,and are very promising electromagnetic absorption materials,but the poor electrical conductivity of multi-element nanoparticles limits the further improvement of their electromagnetic absorption performance.Graphene has received much attention for its light density,good electrical conductivity,high stability and large dielectric constant,and is also a promising electromagnetic absorption material,but the poor impedance matching of graphene limits further improvement of its electromagnetic absorption performance.Constructing multielemental nanoparticle/graphene composites can effectively combine the advantages of both(e.g.,the high energy conversion performance of multielemental nanoparticles and the excellent electrical conductivity of graphene),which is expected to obtain high-performance electromagnetic wave-absorbing materials.In this paper,monodisperse Ag-Co-Fe-P multielemental nanoparticles with uniform size and diameter of about 9.5 nm were controllably constructed under anhydrous and oxygen-free conditions by using the Schlenk Line.Then,the reduced graphene oxide(r GO)solution was post-injected into the reaction system at the reaction temperature,resulting in the uniform growth of Ag-Co-Fe-P multielemental nanoparticles on the surface of r GO to form monodisperse small-size Ag-Co-Fe-P/r GO composites.The composite has excellent electromagnetic absorption properties with a minimum reflection loss(R_L)value of-36 d B at a coating thickness of 1.5 mm and a frequency of 14.7 GHz and an effective absorption bandwidth of 3.2 GHz(12.8～16.0 GHz).This method can prepare small-sized nanoparticles as polarization active sites,form more interfaces with r GO which enhances interface polarization loss to improve electromagnetic absorption performance.Ni has a high Snoek limit and is more abundant than Co.The preparation of Ag-Ni-Fe-P multielemental nanoparticles has lower cost and better electromagnetic properties than Ag-Co-Fe-P multielemental nanoparticles.We used a similar technique to controllably synthesize monodisperse Ag-Ni-Fe-P multielemental nanoparticles of uniform size with a diameter of approximately 9.2 nm.Then,r GO solution was post-injected into the reaction system at reaction temperature,resulting in the uniform growth of Ag-Ni-Fe-P multielemental nanoparticles on the surface of r GO to form monodisperse small-size Ag-Ni-Fe-P/r GO composites.The Ag-Ni-Fe-P/r GO composite has an R_Lvalue of-40.03 d B at a coating thickness of 3 mm,and an effective absorption bandwidth of 3.1 GHz(12.2～15.3 GHz)when the coating thickness is 1.5 mm.Meanwhile,when the coating thickness is 2.5～4.5 mm,the composite can effectively absorb electromagnetic waves in C-band(4～8 GHz)with 99.99%absorption rate.It can be seen that the reflection loss value of the lower cost Ag-Ni-Fe-P/r GO composite is greater than that of the Ag-Co-Fe-P/r GO composite,and the electromagnetic absorption band is effectively broadened.The controlled preparation of multielemental nanoparticle/r GO composites and their electromagnetic absorption properties open up a new research path for the development of electromagnetic wave absorbing materials. |
