Developing Carbon Nanotube/Cyanate Ester Composites With High Energy Storage Density Through Building A Unique Multi-layered Structure With Mica Paper

Due to their low cost,easy processability and good plasticity,high dielectric constant polymer composites(High-k APC)show great potential in various cutting-edge fields including energy storage,electronic information and new energy,etc.With the development of electronic devices toward high functionality and miniaturization,the demand for high performance embedded capacitors has been rapidly increasing,and embedded capacitors have become an important factor in determining the development of electronic devices.High-k is the basis of high performance embedded capacitors,which also should have low dielectric loss and high energy storage density.Compared with ceramic/polymer composites,electric conductor/polymer composites obtain high dielectric constants at smaller conductor loadings,but high dielectric loss and low energy storage density are their common problems.Therefore,this thesis mainly focuses on developing High-k APC with high dielectric constant,low dielectric loss and high energy storage density,which mainly includes following two parts.Firstly,two unique kinds of tri-layered structure composites were designed and prepared.Specifically,0.6 wt% of hydroxylated multi-walled carbon nanotubes(CNTs)were added into epoxy modified cyanate ester resin(CEP)to form composite(CNT/CEP),which was used as the first and third layers of the tri-layered structure composite,respectively;the second layer is mica paper(MP)infiltrated with CNT/CEP or CEP resin.Consequently,the obtained tri-layered structure composite was coded as CNT/CEP–MPI–CNT/CEP or CNT/CEP–MPII–CNT/CEP.The influences of the thickness of MP and infiltration resin on the structure,dielectric properties and energy storage density of the tri-layered structure composites were systematically studied.Results show that dielectric properties and energy density of tri-layered composites are closely related to the infiltration of MP.Specifically,CNT/CEP–MPII–CNT/CEP composite has lower dielectric loss and larger energy storage density than CNT/CEP–MPI–CNT/CEP at the same frequency and thickness of MP.For the CNT/CEP–MPII–CNT/CEP composite of which the thickness of MP is 60 ?m,its dielectric loss is only 0.07 at 100 Hz,about 7.6×10-5 times of that of CNT/CEP;moreover,the energy storage density is 16.5 times of that of CNT/CEP.The origin behind these attractive dielectric properties and energy storage densities of the tri-layered structure composites was discussed through simulating equivalent circuits and correlating with structures.Secondly,two pieces of MPs infiltrated with CEP resin were placed on the same side,two sides or in the middle of CNT/CEP composite and three kinds of layered structure composites were prepared,and coded as 2MP-CNT/CEP,MP-CNT/CEP-MP or CNT/CEP-2MP-CNT/CEP.The effect of the spatial location of MP on dielectric properties,breakdown strength and energy storage density of CNT/CEP was studied.Results show that 2MP-CNT/CEP and MP-CNT/CEP-MP composites have lower dielectric constants than conventional single-layer CNT/CEP composite.This is due to the fact that the presence of the insulating layer MP weakens the internal polarization of the CNT/CEP composite more strongly than the interfacial polarization between MP and CNT/CEP layer.CNT/CEP-2MP-CNT/CEP composites have very low dielectric loss,while 2MP-CNT/CEP composites have high dielectric loss due to the smaller blocking effect of MP on current leakage.However,2MP-CNT/CEP composites have the highest breakdown strength because of the thicker CEP resin layer between two MP layers.When the thickness of MP is 60 ?m,the breakdown strength and energy storage density of 2MP-CNT/CEP are 7.1 and 19.5 times of that of CNT/CEP,respectively.With the same MP thickness,the energy storage density of MP-CNT/CEP-MP composite is 2.6 times of that of the CNT/CEP composite because of lower dielectric constant and breakdown strength.Above results show that the presence of MP infiltrated with CEP resin can endow CNT/CEP composite with higher energy storage density.Among them,the highest energy storage density is obtained when infiltrated MP is placed on the same side of CNT/CEP.