该文聚焦电磁屏蔽材料和纳米材料的热点研究方向，设计了泡沫炭材料与银纳米颗粒(Ag NPs)复合材料的制备及电磁屏蔽性能分析综合实验。该实验通过直接炭化三聚氰胺泡沫及水热还原原位生长法制备了 Ag NPs/泡沫炭复合材料。通过测量 Ag NPs/泡沫炭复合材料的电磁屏蔽参数，优化了电磁屏蔽效能。实验通过材料合成、物性表征、理论参数测试、性能应用等四个环节，拓宽了学生的知识面，锻炼了他们的实践动手能力和分析解决实际问题的能力。
Comprehensive experiment design for the synthesis of carbon foam-based electromagnetic shielding composites
[Objective]With the full arrival of the electronic information age,diverse electronic devices such as digital cameras,laptops,and wearable gadgets have been extensively used in previous decades.These electronic devices have brought immense convenience to people's daily lives,but they trigger serious electromagnetic interference and radiation pollution,which is detrimental to the regular operation of devices and equipment as well as people's health.As an efficient way to overcome electromagnetic interference challenges,electromagnetic shielding materials can weaken the energy of electromagnetic waves due to the impedance mismatch between them.Therefore,in previous years,electromagnetic shielding materials have elicited substantial interest.In this paper,inspired by the emerging topic of electromagnetic shielding materials and nanomaterials,a thorough experiment is developed to create carbon foam and silver nanoparticle(Ag NPs)composite materials and examine their electromagnetic shielding characteristics.[Methods]In the experiment,melamine foam is directly pyrolyzed and carbonized at 1 000℃using the direct carbonization technique.The acquired carbon foam possesses a typical 3D reticular open cell structure,demonstrating satisfactory stability,complete and uniform cell structure,smooth ligament,and large internal loadable space.Moreover,using PVP and silver nitrate as the starting materials,spherical Ag NPs with uniform morphology and 100-nanometer diameter are synthesized simply and swiftly using hydrothermal reduction.In the last step,Ag NPs/carbon foam composites are successfully created by the hydrothermal reduction of Ag NPs onto carbon foam.The microstructure and morphology of the obtained Ag NPs/carbon foam composites are comprehensively characterized by XRD and SEM.Results clearly show that the obtained composites possess a stable structure,and the Ag NPs demonstrate a uniform distribution on the skeleton of the carbon foam matrix.The EDS mapping also confirms the uniform distribution of silver and carbon elements.With the addition of Ag NPs,the carrier concentration of carbon foam increases,and the conductivity of carbon foam can be enhanced.To prove this point,the electromagnetic shielding performance of the pristine carbon foam and Ag NPs/carbon foam composites are determined and reviewed.[Results]Results reveal that the electromagnetic shielding effectiveness of Ag NPs/carbon foam composite increases from 18 dB(pristine carbon foam)to 21 dB.The improvement of the electromagnetic shielding effectiveness of the Ag NPs/carbon foam composite is based on the increased conductivity of the material.Thus,the reflection loss is enhanced,and many heterogeneous interfaces between Ag NPs and foam carbon are produced,leading to dielectric polarization and enhanced dielectric loss and absorption.To examine the shielding mechanism of the obtained Ag NPs/carbon foam composites further,the skin depth,attenuation constant,and complex permittivity are also determined and reviewed.[Conclusions]In summary,through 4D design processes engaging material synthesis,physical characterization,theoretical parameter testing,and performance application,the experiment expands the student's knowledge,exercises the student's practical skills and analytical ability to solve practical problems,and advances the development of innovative,applied talents.
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