Study On The Preparation And Performance Of Carbon-based Composite Materials For Electromagnetic Shielding

To promote the research and application level of bamboo charcoal continually,this research is based on the application needs of bamboo charcoal in the field of electromagnetic shielding.The research uses recarbonization of bamboo charcoal(BC)and High-density polyethylene(HDPE)as main raw materials,with the technique of the mechanical blending and melt extrusion,in order to achieve the continuous preparation of BC/HDPE composites in electromagnetic shielding.The research on the effects of bamboo charcoal content and carbonization temperature influence of the mechanical properties,melting crystallization properties,electrical conductivity,electromagnetic shielding properties and microstructure of composite materials,the reveal of the inner relationship between the content of bamboo charcoal,carbonization temperature,microstructure,and electromagnetic shielding performance,and the classification of the electromagnetic shielding mechanism of bamboo charcoal-based composites,all provide a theoretical basis for breaking the bottleneck of the electromagnetic shielding application of bamboo charcoal.Finally,by applying the preparation technology of BC/HDPE composite material to biomass gasification carbon,and by comparing the performance of bamboo charcoal,gasification charcoal,and wood charcoal based composite materials,the research provides theoretical and technical references for the application of biomass carbon based composites in the field of interior decoration and electromagnetic shielding.The main research results are as follows:(1)Secondary carbonization is a simple and efficient technology to improve the conductivity of carbon.As the recarbonization temperature increases,the specific surface area of bamboo charcoal first increases and then decreases within the range of700?-1500?.The C element content increases from 82.45%to 96.87%,the fixed carbon content increases from 81.22%to 96.3%,and the calorific value from 31.385 MJ/kg to34.904 MJ/kg,the conductivity increases from 10^-8 S/cm to 92.94 S/cm;the recarbonization reduces the polarity of bamboo charcoal and forms many macroporous structures on the fiber cap and cell wall.After the recarbonization,the bamboo charcoal form curved graphite edges,and the degree of graphitization gradually increases with the increase of temperature.The 002 peak of BC1500 is 0.334 nm,which is close to the graphite stripe spacing of 0.34 nm.The recarbonization significantly enhances the conductivity of bamboo charcoal,which is the result of increased carbon content,further shrinkage of cell walls and fiber caps,and formation of curved graphite edges.(2)The carbonization temperature of bamboo charcoal and the content of bamboo charcoal filler have a significant effect on the properties of composite materials.With the increase in the proportion of bamboo charcoal filler,the flexural strength of the composite material continues to increase.The flexural strength of the bamboo charcoal treated at1100?reaches the maximum value of 51.76 MPa when the content is 70%,and the maximum flexural modulus reaches 4.15 GPa when the content is 60%.After the bamboo charcoal is treated by the secondary carbonization at 700?1500?,the bamboo charcoal treated at 700?have the best composite material mechanical properties.The addition of bamboo charcoal changes the melting temperature,cold crystallization temperature,storage modulus and loss modulus of the composite material.On the one hand,it enhances the stiffness of the composite material,and on the other hand,it also strengthens the heat resistance of the composite material.The electromagnetic shielding efficiency of the composite material reaches 27.56 d B after carbonization at 1100?,while the electromagnetic shielding efficiency of the composite material reaches 35.69 d B after carbonization at 1500?,which can shield 99.99%electromagnetic waves.(3)The changes in volatile matter,fixed carbon,ash,carbon element and electrical conductivity of gasified carbon after secondary carbonization at 1100?are consistent with the trend of bamboo charcoal after secondary carbonization,but the high ash content of gasified carbon leads to lower electrical conductivity than that of bamboo charcoal.The interface co MPatibility between biochar and high-density polyethylene is very good.It is evenly dispersed in the matrix and enhances the rigidity of the composite material.The bending strengths of the five carbon-based composite materials such as GC,GC1100,BC,BC1100,and WC are respectively It is 39.38 MPa,43.98 MPa,43.2 MPa,42.46 MPa,45.61 MPa,and the reinforcing effect of charcoal on carbon-based composites is the most significant.After the secondary carbonization of gasified carbon,the conductivity of the carbon matrix composite prepared is 2.03 S/m,and the shielding efficiency of the 3mm thickness composite material reaches 18.35 d B,which is expected to be applied in civil electromagnetic shielding materials after the thickness is increased.