Effective Nonlinear Responses To External AC And DC Electric Field In A Kind Of Graded Coated Composites

Composite dielectric material is a key research subject in modern physics.Through the combination of a variety of forms and technology for several components of materials with different properties,a new kind of material,i.e.composite dielectric material,is formed.The advantages are that these composites can not only keep the properties of each component material,but also add new physical features and functions which the individual component material do not have,so we can design the desired products according to the practical application by changing its shape,size,component ratio and so on.Some composite dielectric material,which physical properties have continuous variation in space,are called gradient composite material,and this kind of material can be found everywhere in nature.In this thesis,the effective responses of nonlinear composites,where the spherical and cylindrical coated inclusions are randomly embedded in a host medium respectively,are studied under the action of an external AC and DC electric field E_app=E₀?1+sin?t? by using a perturbation method.Its main contents are as follows:In the first chapter,a brief summary for the research background,progress of the effective dielectric responses of the nonlinear composites and the research work in this thesis are given.In the second chapter,under the action of an external AC and DC electric field E_app=E₀?1+sin?t?,the problems of the effective response of weakly nonlinear composites with cylindrical coated particle inclusions randomly embedded in a host medium are discussed with the use of the perturbation method,and the local potential distributions of composites are derived separately in the inclusion core particle,coated shell layer material and host regions.All the effective nonlinear responses of the nonlinear cylindrical coated composites and their relationships are obtained in a dilute limit.In the third chapter,under the action of an external AC and DC electric field E_app=E₀?1+sin?t?,the problems of the effective response of weakly nonlinear composites with spherical coated particle inclusions randomly embedded in a host medium are discussed with the use of the perturbation method,and the local potential distributions of composites are derived separately in the inclusion core particle,coated shell layer material and host regions.All the effective nonlinear responses of the nonlinear spherical coated composites and their relationships are calculated in a dilute limit.In the fourth chapter,the results of this thesis are summarized and discussed,and the outlook for further work is pointed out.