With the rapid development of modern electronic industry, humanity has entered the era of electronic information, more and more electronic and electrical equipment has entered every corner of society, but these electronic and electrical equipment will generate certain electromagnetic waves during operation, not only It will produce certain electromagnetic interference on the surrounding electrical and electronic equipment, and it will also cause certain electromagnetic radiation harm to the human body. In order to effectively suppress electromagnetic interference and electromagnetic radiation harm, the research of electromagnetic shielding materials is particularly important. Zheng Wenge, a researcher in Polymer Division of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, has been working on the development of high-efficiency electromagnetic shielding materials, and has made a series of advances in the preparation and performance research of graphene-based electromagnetic shielding materials in the earlier period (ACS Applied Materials & Interfaces, 2011, 3, 918; ACS Applied Materials & Interfaces, 2013, 5, 2677; ACS Applied Materials & Interfaces, 2013, 5, 11383; Advanced Functional Materials, 2014, 24, 4542; RSC Advances, 2015, 5, 24342; Carbon, 2016, 100, 375; Carbon, 2016, 102, 154; ACS Applied Materials & Interfaces, 2016, 8, 8050). Recently, the team made new progress in the structural design and performance study of graphene-based electromagnetic shielding materials. (1) The researchers designed a high-strength flexible polymer/graphene composite film with a sandwich structure and explored the influence of zig-zag folded structures on the electromagnetic shielding of the film (see Figure 1). The high-strength flexible polymer/graphene composite film is prepared by using an ordinary non-woven fabric as a reinforcing interlayer and a polymer/graphene composite as a conductive coating. Electromagnetic shielding test results show that the zigzag folding of the film sample can enhance its electromagnetic shielding performance (especially for films with higher electrical conductivity), wherein the smaller sawtooth angle and the longer sawtooth side length make the zigzag fold pair The enhancement of the electromagnetic shielding of the thin film is more obvious, which is mainly because the smaller sawtooth angle and the longer sawtooth side length can enable a larger area of ​​material to participate in the electromagnetic shielding, and at the same time enhance the multiple reflection attenuation of the electromagnetic wave by the sawtooth. At the same time, the electromagnetic shielding performance of the thin film can be effectively controlled by simply stretching or compressing the sawtooth structure. The relevant results were published in the international journal Carbon, 2017, 113, 55 and applied for Chinese invention patent 201610850306.5. (2) The researchers explored the effects of multilayer composite structures (gradient structures + hollow sandwich structures) on the electromagnetic shielding properties of polymer/graphene composites. Firstly, composite materials with different gradient structures can be prepared by free superposition and combination of different graphene polymer/graphene composite foams. The results show that: 1 The gradient structure has little effect on the electromagnetic shielding performance of composite materials, but it can The wave impedance between the composite material and the air is greatly enhanced, which in turn enhances the electromagnetic wave absorption performance; 2 The structural design with the strongest wave-absorbing performance has the abc structure (as shown in Fig. 2) and the structural design with the strongest electromagnetic wave reflection. It is a cba structure. In addition, sandwiching a wave-transparent material between two polymer/graphene composite foams can provide a composite material with a hollow sandwich structure. The results show that: 1 The hollow sandwich structure can greatly improve the shielding performance of the composite material, but the main reason is that It enhances the reflection of electromagnetic waves by the material. The increase in the shielding effectiveness of the sandwich structure on the composite material is related to the thickness of the intermediate transmission layer. When the thickness is 1/4 wavelength in the corresponding frequency band, the increase is greatest. This research has great reference value for designing polymer-based electromagnetic shielding materials with high shielding and absorbing properties. The relevant results were published in the International Journal of Composites Science and Technology, 2017, DOI: 10.1016/j.compscitech.2016.12.002, And apply for Chinese invention patents 201610919451.4 and 201610919480.0. The above work was supported by the National Natural Science Foundation of China (51603218, 51473181, 51573202), the Natural Science Foundation of Ningbo (2016A610269) and the China Postdoctoral Science Foundation (2015M570531). Thread Rolling Die,Thread Rolling Die Head,Die Thread Rolling,Cylindrical Thread Rolling Dies Chongqing Henghui Precision Mold Co., Ltd , https://www.citool.com
Ningbo Materials has made progress in structural design of electromagnetic shielding materials