Research On Heterogeneous Interface Microstructure And Interface Coupling Characteristics Of Magnetic Metal@Semiconductor Composites

In this thesis,three different structures of magnetic metal@semiconductor composites,including Fe@ZnO,Fe2O3-Out-MWCNTs and Fe2O3-In-MWCNTs were prepared by arc-discharge method and chemical synthesis method.Transmission electron microscopy,X-ray diffraction,vibrating sample magnetometer,X-ray photoelectron spectroscopy and vector network analyzer were used to test the samples.The paper systematically studied the micro structure,magnetic properties and electromagnetic properties in the range of 2-18 GHz and mainly explained in detail for the magnetic properties and electromagnetic wave absorption characteristics at the nanometer scale.In this thesis,magnetic metal@semiconductor composites are mainly used as research objects.The different characteristics of electromagnetic properties are analyzed through test results.It is explained that the magnetic metal@semiconductor composite heterostructure interface microstructure has very strong interfacial coupling characteristics,and it provides a strong proof for obtain better absorbers.In this thesis,a composite material of Fe@ZnO core-shell structure was prepared by arc-discharge method.In this paper,a bulk anode material of composite material was prepared by iron ratio zinc oxide according to mass ratio of 9:1.Ar and H2 as a protective and reactive gas,the H2 is excited by the instantaneous high temperature to obtain the ionic gas and the anode material is instantaneously melted into a liquid state,and the liquid metal is taken out by the flow of the gas in the enthalpy,while passing through the inert gas.At the same time,energy is lost by collision with an inert gas or a reactive gas,forming Fe@ZnO nanoparticles in one step.The obtained nanoparticles are composed of 20-30 nm iron as a core and 2-5 nm zinc oxide as a shell.Since the electronegativity of the heterogeneous phase has a significant difference,a high interfacial coupling property is generated under the action of electromagnetic waves.A large number of dipoles are formed at the interface,and a polarized surface is formed.The matching of the core@shell structure produces interfacial polarization.The Cole-Cole diagram further proves the dielectric polarization of Fe@ZnO nanometer core@shell composites.Due to the influence of heterogeneous phase microstructure and interfacial coupling characteristics,nanometer-scale composite materials with zinc oxide as the outer shell and magnetic metal iron as the core improve the impedance matching characteristics,increase the resistivity,and increase the loss of electromagnetic waves.Eliminating the effects of eddy current losses,the main magnetic loss mechanism of Fe@ZnO nanometer core@shell composites and natural resonance.Multi-walled carbon nanotubes,heterogeneous phase doped carbon nanotubes and heterogeneous phase controllable self-assembled carbon nanotube composites have been systematically studied in this paper.In this thesis,the multi-walled carbon nanotubes were modified by different chemical processes,and the Fe2O3-Out-MWCNTs and Fe2O3-InMWCNTs were prepared by the treatment of ionic metal solution doping,oxidation and reduction.In this paper,the interfacial coupling properties of heterogeneous composites are further proved by the analysis of microstructure,magnetic properties and electromagnetic properties.In the frequency range of 2-18 GHz,the original multi-walled carbon nanotubes and the carbon nanoparticles with controlled doping of Fe2O3 have obvious natural resonance phenomena,especially the complex permeability of Fe2O3-InMWCNTs has many obvious natural resonance peaks,and the dielectric of carbon nanotubes is mainly compared with zinc oxide and manganese oxide.The material has more excellent impedance matching characteristics,and the dielectric of the carbon nanotubes is kept at a large value.Due to a large number of defects(proven by Raman spectroscopy)in the modification process of the carbon nanotubes,the resistivity is improved.Thereby,the influence of the eddy current loss is eliminated,and multiple natural resonance phenomena occur at 5-15 GHz,which proves that the magnetic loss performance with natural resonance is the main mechanism while having a very high dielectric loss.Due to the different micro structure and interfacial coupling properties of Fe2O3-Out-MWCNTs and Fe2O3-In-MWCNTs,there are multiple polarization centers and polarization surfaces,which make the two magnetic metal@semiconductor composites have intentional electromagnetic properties.