摘要
为了进一步提升泡沫铝的吸波性能,利用喷涂法在泡沫铝表面涂敷了一层吸波剂涂层,采用数码相机、扫描电镜对喷涂前后泡沫铝表面形貌及吸波涂层形貌进行了观察,利用雷达截面法测量了泡沫铝的吸波性能,研究了泡沫铝的密度、厚度以及吸波剂厚度对泡沫铝吸波性能的影响。结果显示,随着密度的降低,泡沫铝孔隙的尺寸增加,孔壁减薄。喷涂吸波剂后,泡沫铝孔隙形貌未发生显著变化,吸波剂会在孔隙底部聚集,甚至会填满孔隙。泡沫铝的密度对其吸波性能影响显著,密度小于 0.405 g·cm^(-3)的泡沫铝才具有一定的吸波性能,且随着频率的增加,吸波性能增强,密度为 0.210 g·cm^(-3)的泡沫铝在 18.00 GHz 时电磁波反射率达-3.01 dB。泡沫铝的厚度对其吸波性能影响不大。喷涂吸波剂涂层后,泡沫铝吸波性能增强,当吸波剂厚度为 1.23 mm 时,泡沫铝的电磁波反射率达到-11.12 dB。泡沫铝的吸波特性是由泡沫铝密度、表面吸波涂层、电磁波频率共同作用的结果。
Aluminum foam was a new material with large pores in aluminum alloy matrix. It had not only the mechanical properties of light weight,high specific strength and specific stiffness,but also physical properties such as shock absorption,noise reduction and electromagnetic protection,which had attracted wide attention from scholars at home and abroad. In terms of electromagnetic protection,the scholars at home and abroad had conducted in-depth research on it. Research showed that aluminum foam not only had good electromagnetic shielding performance,but also had a certain wave absorbing property. In order to further improve the absorbing properties of aluminium foam,the absorbing coating was coated on the surface of aluminium foam by the spraying method. Magnetic ferrite was selected as the absorbing agent,and the coating thickness was controlled by adjusting the spraying times. In order to enhance the bonding between aluminum foam and absorbing coating,aluminum foam was treated in the sodium hydroxide solution of 5%(volume fraction). The morphology of aluminium foam and absorbing coating were observed by digital camera and scanning electron microscope(SEM). The absorbing properties of aluminium foam were measured by radar cross section(RCS)method based on GJB 2038A-2011The effects of density and thickness of aluminum foam on the absorbing properties of aluminium foam were studied. The effects of thickness of absorbing coating on the absorbing properties of aluminium foam were investigated too. The results showed that the pore size of aluminium foam increased,and the pore wall thickness decreased with the density decreasing. When the density of aluminium foam was high,the pores of the aluminium foam were spherical or ellipsoidal. However,when the density of aluminium foam was low,the pores of aluminium foam were polygonal and irregular. After spraying the absorbing coating,the morphology of aluminium foam did not change significantly. The absorbing coating accumulated at the pore bottom of aluminium foam and even filled the pores. The density of aluminium foam had a significant effect on the absorbing properties. RCS of aluminium foam with the density of more than 0.540 g·cm^(-3)was greater than zero in the frequency range of 2~18 GHz,and there were no absorbing properties. RCS of aluminium foam with the density of less than 0.405 g·cm^(-3)was less than zero in a certain frequency range,so there were certain absorbing properties. With the frequency of radar wave increasing,the absorbing properties of aluminium foam increased. When the frequency of radar wave was18.00 GHz,RCS of aluminium foam with the density of 0.210 g·cm^(-3)was -3.01 dB. The RCS of aluminum foam with different thickness was similar,and the absorbing property of aluminium foam was enhanced with the frequency of radar wave increasing. The thickness of aluminium foam had little effect on its absorbing properties. After spraying the absorbing coating,the absorbing properties of aluminium foam were improved. With the thickness of absorbing coating increasing,the absorbing properties were enhanced. When the thickness of absorbing coating was 1.23 mm,RCS of the aluminium foam reached -11.12 dB at the frequency of 18 GHz,and RCS of the aluminium foam was increased by 6.12 dB compared with the original aluminium foam. In the frequency range of 2~18 GHz,the average RCS reached -5.24 dB. For microwave absorbing materials,most of the electromagnetic waves would be absorbed when they are incident on the surface of the material,which included absorption loss,reflection loss and multiple reflection loss. When a beam of electromagnetic wave was irradiated on the surface of the aluminium foam,it would be reflected,refracted and reflected many times Finally,it would return to the free space. With the density of aluminium foam decreasing,the plane area of the aluminium foam surface decreased,that was to say,the reflection of the electromagnetic wave on the surface of the aluminium foam decreased,but the multiple reflection of the electromagnetic wave increased,and the multiple reflection loss increases during this process,so the absorbing properties of the aluminium foam were enhanced. With the frequency of electromagnetic waves increasing,the penetration of electromagnetic waves would increase. It would pass through the pore wall of aluminium foam and form electromagnetic wave refraction Electromagnetic waves would enter the adjacent pores from the surface pores,and would have multiple reflections again. During this process,multiple reflection losses would increase,and the absorbing properties of aluminium foam would be enhanced. After spraying the absorbing coating,the absorption loss could be increased due to the dielectric loss and magnetic loss of the absorbing coating,and the absorption loss would further increase with the thickness of absorbing coating increasing,so that the absorbing properties of the aluminium foam could be improved. The absorbing property of aluminium foam was the result of the interaction of aluminium foam density,absorbing coating and electromagnetic wave frequency,during the process,absorption loss,reflection loss and multiple reflection loss all played different roles.
作者
王耀奇
刘文祎
褚楚
李红
Wang Yaoqi;Liu Wenyi;Chu Chu;Li Hong(Manufacturing Technology Institute,Aviation Industry Corporation of China,Ltd,Beijing 100024,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2022年第12期1663-1668,共6页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(50875249)资助。
关键词
泡沫铝
吸波涂层
雷达波
吸波性能
aluminium foam
absorbing coating
radar wave
absorbing properties
