Investigation On The Dielectric And Energy Storage Properties Of Carbon Nanotubes/Polymer Composites

Carbon nanotubes(CNTs)with hollow tube reticular structure are ideal quasi-one-dimensional nano-materials.Carbon nanotubes have extremely high mechanical strength,excellent electromagnetic and thermal performance,unique semiconductor or metal characteristics,etc,making it become one of the most promising nano-materials in the 21 st century.In recent years,some carbon nanotubes/polymer composite materials with high dielectric and energy storage properties have been synthesized,showing very broad application prospects in microwave absorption and radiation protection,energy storage device,etc.In this dissertation,the dielectric and microwave absorption performance of carbon nanotubes/polymer composite is discussed systematically.And the energy storage property of carbon nanotubes/polymer composites is investigated in detail.Firstly,the advances in researches for CNTs,such as structural characteristics,physical and chemical properties,the preparation methodsof carbon nanotube/polymer composites,especially in the improvement of dispersion for carbon nanotubes in polymers,are reviewed systematically.Based on the material microstructure-properties correlation theory,and taking into full account the influence of carbon nanotubes content,the waveness of carbon nanotubes,the real and imaginary parts of the permittivities of CNTs and polymer,the electromagnetic wave frequency on carbon nanotubes/polymer composite's dielectric property.The complex permittivity of carbon nanotubes/polymer composites is deduced by applying the an equivalent resistance-capacitance(RC)network.Then a dielectric model is developed.And for carbon nanotubes/polymer composites,the formulas of dielectric spectrum,dielectric loss tangent,microwave attenuation coefficient and microwave absorption coefficient of the materials are deduced in detail.By the numerical simulation,it can be theoretically proved that the improvements of nanotube/polymer composite's dielectric property can be caused.And more strong electromagnetic wave absorption of nanotube/polymer composite is caused,with the increase of carbon nanotubes content and the decrease of carbon nanotubes waveness.In addition,a good linear relationship between microwave attenuation coefficient,microwave absorption coefficient and frequency is found.The influence of carbon nanotubes content,the waveness of carbonnanotubes and the electromagnetic wave frequency on carbon nanotubes/polymer composite's energy storage property is investigated in detail.A theory model for energy storage property of nanotubes/polymer composite is proposed.The theoretical results for energy storage property of carbon nanotube/polymer composite indicate that energy storage property of the composite increases explicitly with increasing volume fraction of carbon nanotubes in the composite.In addition,the increase of carbon nanotubes waveness and electromagnetic wave frequency can cause energy storage density decreased obviously.By adjusting the content and the waveness of carbon nanotubes,the best balance of increasing the energy storage density and controlling electric loss can be achieved.And then the carbon nanotubes/polymer energy storage materials with excellent properties can be produced.The aim of this research is to provide a certain theoretical basis for the preparation of excellent carbon nanotube/polymer composite dielectric and energy storage materials.