Preparation Of Melamine-based Carbon Foam And Its Electromagnetic Shielding Properties

With the rapid development of science and technology,the popularization of electronic equipment has brought serious electromagnetic interference and pollution.It not only affects the stability of electronic equipment,but also long-term radiation can cause grave harm to the human body.Applying certain electromagnetic shielding to corresponding electronic equipment is an effective solution to the above problems.In recent years,due to the continuous development of wearable devices,soft and thin electromagnetic shielding materials have received widespread attention.Therefore,this paper studies the electromagnetic shielding effectiveness of melamine-based carbon foam and its composite foam,and analyzes its electromagnetic mechanism.In this paper,melamine sponge is used as the raw material,and the composite carbon foam is prepared through the carbonization process,in-situ growth of CNTs,and impregnation and loading of nano-Fe₃O₄.The effects of the carbonization temperature and the loading of the two on the cell morphology,conductivity and electromagnetic shielding effectiveness of the carbon foam were studied respectively.The specific research content and results are as following:（1）The influence of carbonization temperature on the pore structure of carbon foam was studied,and the influence mechanism of pore structure on the electromagnetic shielding performance was analyzed.The study found that with the increase of the carbonization temperature,the shrinkage rate,cell density,and order of carbon crystallites（graphitization）of the melamine-based carbon foam gradually increases.The combined effect of the above factors lead to the electrical conductivity of the carbon foam.Efficiency and electromagnetic shielding performance are improved.When the carbonization temperature is 900℃,the maximum cell density of the carbon foam is 3.29×10¹³cell/cm³,the electromagnetic shielding performance can reach 16.1d B,and the absolute shielding efficiency（SSE_T）reaches 4780.28d B·cm²/g.At this time,the foam The absorption loss accounts for 87%of the total loss.After 50compression cycles,the retention rate of electromagnetic shielding performance reached 86.2%.Based on the experimental results,it is believed that the melamine-based carbon foam is a soft and thin shielding matrix with good compression cycle performance and high absorption loss.（2）The influence of CNTs loading on the electromagnetic shielding performance of melamine-based carbon foam was investigated.The results show that the loading of CNTs effectively improves the conductivity of carbon foam,and plays a leading role in improving the electromagnetic shielding performance of the material.When the load of CNTs is 3.2mg/cm³,the conductivity and electromagnetic shielding performance of carbon foam reach the maximum values of 82.92S/m and 35.2d B,respectively.The absorption loss accounts for 87.7%of the total loss,and the SSE_Treaches the highest value of 8935.51d B·cm²/g.After 50 compression cycles,the shielding performance retention rate is 70.5%.However,when the loading of CNTs exceeds 3.2mg/cm³,CNTs agglomerate inside the composite carbon foam,and the structure of the carbon foam is seriously damaged at this time,and the shielding effect is greatly reduced.The main reason for the above results is that proper CNTs loading helps to form a good conductive network.（3）The effect of loading nano-Fe₃O₄ on the performance of composite carbon foam was studied.The results show that the loading of nano-Fe₃O₄ improves the magnetic loss performance of carbon foam,which is intuitively manifested as a substantial increase in electromagnetic shielding performance.When the nano-Fe₃O₄loading is 17.1mg/cm³,the electromagnetic shielding performance of the material reaches the highest value of 49.4d B,and the absorption loss accounts for 89.3%of the total loss.The retention rate of electromagnetic shielding performance after 50compression cycles was 62.2%.But this time,the SSE_T of the carbon foam is reduced to 5318.34d B·cm²/g,so compared with nano-Fe₃O₄,loading CNTs is more conducive to the preparation of light and thin high-performance flexible electromagnetic shielding materials.