Study of the Static Effective Electromagnetic Property of Particulate Composite
Supervisor:zheng qin hong
The world is faced with serious energy crisis and environmental problems caused by traditional energy.It is of great theoretical significance and practical value to study advanced energy and magnetic energy storage which can save energy and keep sustainable use.Dielectric technology for energy storage has wide prospect in applications and broad market demand in modern energy research,and it has become one of the hot issues in many findings about technology for energy storage.The study and manufacture of composite is the core technology for dielectric energy storage.Effective electromagnetic parameters of composite are important in the analysis and design of composites.Therefore,the research of effective electromagnetic parameters of particle-filled composites is of theoretical significance for engineering applications.The main research is as follows:(1)Starting from the microstructure of composites filled with spherical particle,the electromagnetic field equations for multicomponent(multiphase)composites filled with particles under static conditions are obtained through physical modeling of particle-filled composites.The proportion of radius,spacing and volume of spherical particle is explored to make the maximum filling ratio of two-phase composites filled with spherical particle.(2)For two-phase composites filled with spherical particle,the Laplace equation is solved by using separation of variables,and the theoretical solution of the electric field strength in the two-phase composites under the electrostatic model is obtained.Based on mean field method and average energy method,the theoretical expression was made.Being compared with the experimental data of composites filled with four particles and some other theoretical formulas with higher calculation accuracy.Through such comparison,the effective dielectric constant and energy storage of the composites are explored.The findings illustrate that the calculation of the theoretical formula based on the average energy method are closer to the experimental measurements than those obtained by other theoretical formulas,and coincide with the experimental measurements to great extent,thus the validity of the model and the formula can be proved.In this way,the effective constant can be predicted and the design of composite materials can be made.In the study of energy storage materials,on the one hand,when the dielectric constant of the filling phase increases to a certain threshold,the energy storage density of the composites tends to be relatively stable,almost no longer changing with the dielectric constant of the filling phase;on the other hand,some composites with moderate effective dielectric constant have higher energy storage.(3)For(three-phase)composites filled with spherical particles,the Laplace equation is solved by using separation of variables,and the theoretical solution of electric field strength of each component in the electrostatic field model is obtained.The validity of the theoretical formula for the effective dielectric constant of Particulate-Filled(three-phase)composites filled with spherical particles obtained by the average energy method are verified through comparison with other experimental data.The size of metal nanoparticles and the effect of interface on the effective permittivity and energy storage properties of the composites are analyzed through the obtained theoretical formulas.The calculated results conincide with the experimental results.It can be used to guide the design and manufacture of composites.(4)For two-phase composite magnetic materials filled with spherical particles,the Laplace equation is solved by using the method of separation of variables,and the theoretical solution of magnetic field strength in two-phase composite materials under the condition of static magnetic model is obtained.The theoretical expressions are compared with the experimental data and some theoretical formulas with high accuracy.The correctness of the physical model and the effective permeability theory obtained by the average energy method are verified.The validity of the formulas are analyzed.The effects of the permeability and volume ratio of the filled phase particles on the effective permeability and magnetic energy storage of the composites are analyzed.The composite materials with high magnetic energy storage can not be fabricated by increasing the permeability of filled phase under certain volume ratio.Some composite materials with moderate effective permeability have higher magnetic energy storage.If the filled phase particles are superconducting particles,the magnetic energy storage of the composites is only lower than that of the matrix at the critical temperature,and the superconducting particles can not improve the magnetic energy storage of the composites.(5)For three-phase magnetic composites filled with spherical particles,the magnetic intensity in each component under static magnetic model is obtained by using separation of variables,and the theoretical expression of effective permeability is made with the help of the mean field method and the mean energy method respectively.Therefore,by using the obtained theoretical formulas,the size effects of the of nanoparticles in the filled phase,the interface relative permeability and the magnetic energy storage ability of the composites,the effect of the interface of nanoparticles on the effective permeability of the composites in extremes,and the effect of superconducting nanoparticles for the effective permeability of the composites are discussed.The influence of interfacial phase on magnetic energy storage of composites can not be neglected.The interfacial phase even plays a decisive role in improving the magnetic energy storage of composites to a certain extent.These calculation formulas and analysis have important reference values for the design,preparation and analysis of composites.