Permeability Model Building And Preparation Of Ordered Structures Soft Magnetic Composite Materials

In the field of electromagnetic shielding, magnetic shielding for low frequency (<100kHz) is one of the key and difficult points. Theoretical calculation found that the shielding effectiveness is determined by the permeability of the materials with the same size. Because the effective permeability theory of the magnetic composite is imperfect at present, the main work of this paper is to build a model what is predictable the effective permeability of the composite, which is filled by particles in the various array. This model will use to guide the work of preparation of magnetic composites. This paper is divided into the following three parts:1、Building a model for spherical particles in the composite material with different array based on the magnetic dipole. Determining the magnetization of the particles with averaging the additional magnetic field, then calculate the effective permeability of the composite. This model can be used to calculate the effective permeability of the spherical particles with different array. Comparing with the experimental data and other models prove the accuracy of the current model.2、With the introduction of the demagnetization factor, the model is obtained which can calculate the effective permeability of the flake in the composite material with different array. Flake is approximately ellipsoidal in this model which using the average area instead of the homogenization means of spherical particles for the large error. This model can be used to predict the effective permeability of flake particles with different array and orientation. Through the calculation of the model, the effective permeability of the composite can be greatly improved when flake particles from random into orientation.3、Using magnetic field orientation increase the permeability according to the model prediction. It also can further validate the model. After using magnetic field to deal with the composite filled flake carbonyl iron powder, it found that doubling the permeability compared with untreated. The model can accurately predict the effective permeability of the composite treated magnetic field.and it is confirmed that the model can be used to guide the preparation of magnetic composite materials.Characteristics of the paper is mainly reflected in the following two aspects:1、The current effective permeability model can only calculate the specific arrangement of filler particles, our model to calculate the effective permeability of the filler particles with different arrangement and orientation, and complete consideration of the interaction between the filler particles, so that to improve the accuracy of the model.2、Improving the effective permeability of composite material has obstacles with the guidance of the current model. According to the results of our model, using magnetic fields to improve the effective permeability of the composite. If the permeability constant, the particle volume fraction will be reduced to half. So the weight of material can be significantly reduced. This paper has important theoretical and practical significance on the study of composite.