Preparation Of Graphene 3D Printed Composite Wire And Study On Its Absorbing Properties

Electromagnetic pollution has now become one of the public pollutions of society,which not only affects the normal operation of electronic equipment,but also threatens human biological systems.The ideal and efficient wave absorbing material should have the characteristics of strong absorption,wide absorption band,light weight and thin matching thickness.The high density and large matching thickness of existing absorbing materials limit their industrial applications.There is an urgent need to develop high-efficiency absorbing materials with light weight and thin thickness.As a new type of carbon material,graphene’s excellent properties of low density,corrosion resistance,large specific surface area,high electrical conductivity and thermal conductivity,and high mechanical strength make it a research hotspot in various fields,and is an ideal lightweight and efficient absorbing material.However,due to the large dielectric constant of graphene,its impedance matching performance is poor,in addition,there are problems that the loss mechanism is single and it is difficult to form.In order to solve the above problems,this paper adopts the following solutions: 1)Compounding graphene with high molecular polymers to reduce the conductivity of graphene and make it have better matching characteristics;2)Adding magnetic materials(nano-Fe3O4)into graphene to make up for the short board with a single graphene loss mechanism;3)Design and manufacture of absorbers with different structures to solve the problem that graphene itself is difficult to form.The main work and research results are as follows:1)The variation of the forming and conductive properties of graphene/PLA composite wires under different melt extrusion molding process parameters was studied;On this basis,further explore the effects of material formulations on the electrical and mechanical properties of graphene/PLA composite wires.The results show that the die temperature should be above 110 ℃,and the cooling water temperature around 40 ℃ can ensure the surface quality of graphene/PLA composite wire;When the spindle speed is 14 r/min and the traction speed is 10 ～ 13 r/min,the wire diameter can be guaranteed;As the die temperature and spindle speed increase,the conductivity of the wire exhibits a change pattern that rises first and then decreases.When the die temperature and spindle speed are 125 ℃ and 14 r / min,respectively,the conductivity of graphene/PLA composite wire is better.In addition,when the content of graphene increases,the conductivity of graphene/PLA composite wire tends to increase first and then decrease.Among them,when the mass fraction of graphene is 8wt%,the electrical conductivity of the obtained graphene/PLA composite wire is higher than other contents.Under the same conditions,the tensile strength of graphene/PLA composite wire increases first and then decreases.The maximum tensile strength is obtained when the mass fraction of graphene is 2wt%;The change law of elongation at break decreases with increasing graphene content.When the mass fraction of graphene is 8wt%,the mechanical properties of graphene/PLA composite wire are lower than the qualified requirements.The solution is to add ACR.When its addition amount is 0.5wt%,the tensile strength and elongation at break are 21.79 MPa and 6%.Compared with no addition,it increased by 12% and 28% respectively.2)Graphene/PLA composite samples were quickly prepared using FDM technology and the absorbing properties were improved.The electromagnetic parameters of the samples were tested by the waveguide method,the reflection loss was calculated with the help of transmission line theory,and the absorption properties of different composite samples were analyzed to reveal the absorption mechanism.The results show that the real part of the complex dielectric constant of the graphene/PLA composite sample increases with increasing graphene content.When the mass fraction of graphene is 9wt%,the real part of the complex dielectric constant is the highest.Under the same conditions,the change law of the imaginary part of the complex dielectric constant increases first and then decreases.When the graphene mass fraction is 8wt%,the complex dielectric constant of the graphene/PLA composite sample has the highest imaginary part.With the increase of electromagnetic wave frequency,the change rule of the reflection loss of the graphene/PLA composite sample is to decrease first and then increase.When the graphene content is 5 ～ 9wt%,the minimum reflection loss peaks of the graphene/PLA composite sample are-3.1d B,-5.8d B,-7.2d B,-9.6d B,-8.1d B.Since the reflection loss is higher than-10 d B,it does not meet the requirements of microwave absorption.Therefore,the magnetic medium type absorber(nano-Fe3O4)is added to the original composition.When the content of medium nano-Fe3O4 is fixed at 20wt%,the real part and imaginary part of the complex dielectric constant both increase with the increases of graphene content.The real and imaginary parts of the complex dielectric constant when the mass fraction of graphene is 5wt% are higher than the corresponding single-component graphene/PLA composite samples.It shows that the complex dielectric constant of the two-component composite sample is higher than that of the single component.Under the effect of the synergistic effect,the real and imaginary parts of the complex permeability of the graphene/nano-Fe3O4/PLA composite sample increase with the increase of the graphene content,which is higher when the graphene content is 5wt%.With the increase of graphene content,the peak reflection loss of the graphene / nano-Fe3O4 / PLA composite sample decreases.When the graphene mass fraction is 5wt%,the peak of its minimum reflection loss is-13 dB;the effective absorption bandwidth Reaching 3.6GHz(12.4 ～ 16.0GHz),the wave absorption performance is far superior to the graphene / PLA composite sample with the same graphene content.It shows that when the content of nano-Fe3O4 is certain,increasing the content of graphene helps to improve the wave absorption performance,and the wave absorption performance of the two-component composite sample is better than that of the single-component composite sample.3)Designed and manufactured absorbers with different structures and studied their absorbing performance.Studies have shown that,when the honeycomb hole structure is appropriately increased,compared with the flat-shaped structure of the absorber,the impedance matching is improved and the multiple reflection interface is added,which makes the electromagnetic wave consume more energy during the propagation process,so the absorbing performance stronger.