| The research of electromagnetic shielding material has important significance with the complicating electromagnetic environment.In this paper,we study on the electromagnetic wave reflection and absorption double-effect wood composites,obtained a kind of new electromagnetic shielding materials which has absorbed and reflected double shielding effection.We prepared Fe/wood composites and Fe&Fe3O4/wood composites materials by in situ chemical synthesis process and mechanical mixing respectively.We characterize the structure and magnetic properties by X-ray diffractometer,Scanning electron microscope,Fourier infrared spectrometer and Magnetic measurement,discussing the effects of different condition on the structure and magnetic properties.And we measure the Fe/wood composites and Fe&Fe3O4/wood composites useing a vector network analyzer.Magnetic parameters and the wave absorption properties of the composite material are analyzed by MATLAB.Research shows:（1）Fe/wood composites prepared by in-situ chemical synthesis at room temperature have a certain degree of oxidation,and with the increasing of the composites ratio,the oxidation becomes more severe.The Fe particles are uniform in size,connecting with each other,and covering on the surface of wood like net-work.There is a strong physical and chemical effects between the Fe and wood.The prepared Fe/wood composites have lower saturation magnetization and remnant magnetization,and higher coercivity.With the increasing of reduced Fe ratio,both the real and imagine parts of the dielectric constant of the material are improved.The absorption loss of material is mainly based on the dielectric loss.（2）The size and distribution of particles are generally uniform,and there is a strong physical and chemical interaction between the functional particles and wood for all of composites prepared by three methods.（3）Fe&Fe3O4/wood composites prepared by in-situ chemical synthesis method have lower saturation magnetization value and greater coercivity;Increasing the ratio of Fe/wood or Fe3O4/wood improves the saturation magnetization and remnant magnetization in the process of mechanical blending Fe/wood and Fe3O4/wood,But the increasing of Fe/wood blend ratio will increase the coercivity and decrease the sample’s super-paramagnetic;compared with the other two preparation method,the mechanical blend nano-Fe powder and Fe3O4/wood preparation method has the highest saturation magnetization(maximum 134.92 emu?g-1)and the lowest remnant magnetization in the three processes(<5 emu?g-1)and coercivity（<20 Oe）.this method can not only increase the saturation magnetization of the materials,but also keep the low remnant magnetization and low coercivity of Fe3O4 particles,making it to be a better preparation method for superparamagnetic wood composites.（4）Comparing Fe&Fe3O4/wood composites obtained by three preparation processes,the composites prepared by mechanical blending nano-Fe powders and Fe3O4/wood have better microwave absorption property.The composites obtained by the three methods show similar microwave absorption value within tested frequency range,indicating that the prepared materials are composite materials with a wide microwave absorption frequency. |
