鎳鋅鐵氧磁體/碳纖維複合薄膜電磁波吸收行為之研究

A Study on Electromagnetic Wave Absorbing of Ni-Zn Ferrite/Carbon Fiber Composite Films

黃盈蓁(Yin-Tsen Huang)

指導教授 ： 鄭大偉 ； 李貴琪

國立臺北科技大學/工程學院/資源工程研究所/碩士(2009年)

摘要

近年來人類追求數位化與電子化的高科技生活，因此電子科技發展迅速與日常生活品質之提升，電子、電機與通訊等電子資訊產品便應運而生。人類在享受這些便利時，自身因長期暴露於電磁波之環境，使電磁波被人體所吸收之情況加劇，而可能對人體造成危害；亦會對其它電子產品造成電磁波干擾 (Electromagnetic Interference，EMI)，影響電子儀器之正常運作。現今許多電磁波屏蔽材大多以反射方式屏蔽電子、電器所發出之電磁波，而經反射後之電磁波易造成儀器間相互干擾及人體之危害，且易造成環境之二次污染。電磁波吸收體可將電磁波吸收並以熱的形式消散，可有效地減少電磁波二次危害問題。
本研究是以共沉澱法及固態合成法進行鎳鋅鐵氧磁體之合成與碳纖維作為吸收劑，水性聚氨基甲酸酯 (Waterborne Polyurethane，水性PUR) 作為基材，以高分子混摻法製成具有電磁波吸收功能之水性 PUR 複合薄膜。藉由磁性填充材之電子自旋與磁區壁移動之特性，與導電性填充材之導電網絡性質，使電磁波能量於材料內部消散。
研究結果顯示，鎳鋅鐵氧磁體之合成方式、填充量、厚度以及碳纖維之添加與否均會影響電磁波吸收效益。以固態合成法於 1300℃ 熱處理之鎳鋅鐵氧磁體，所製成之複合薄膜，填充量為 20 vol.%，厚度為 0.6 mm，於高頻之頻率 2560 MHz 時，可獲得最佳電磁波吸收效益為 – 14 dB；於低頻之頻率 30 MHz 時，電磁波吸收效益為 – 29 dB，其電磁波吸收效果於低頻最高可達 99%。固態合成法於 1300℃ 熱處理之鎳鋅鐵氧磁體，與研磨過後碳纖維平均長度為 49.4 μm，所製成之複合薄膜，填充量為 20 vol.%，厚度為 0.6 mm，於高頻之頻率 2450 MHz 時，可獲得最佳電磁波吸收效益為 – 18 dB；於低頻之頻率 30 MHz 時，電磁波吸收效益為 – 15 dB，其電磁波吸收效果於高頻最高可達 90%。

關鍵字

鎳鋅鐵氧磁體 ； 碳纖維 ； 高分子混摻法 ； 水性聚氨基甲酸酯 ； 複合材料 ； 電磁波屏蔽 ； 電磁波吸收效益

並列摘要

In recent years, with the rapid development of digitization, modern science, and technology gave rise to a lot of electronic, electrical communication products, which had improved people’s daily lives greatly. Although electronic devices benefit human life, they can radiate the unwanted electromagnetic signals, which not only may cause radiative damage to human body, but also interfere with the normal working of the electronic appliances. Nowadays, most of the shielding materials can shield electromagnetic wave with reflection, which caused second pollution of environment. To overcome the problem created by EMI, electromagnetic wave absorber with the capability of absorbing electromagnetic energy incident on the surfaces of materials and dissipated by transforming into heat. It could reduce effectively the damage of electromagnetic wave.
In the study, Ni-Zn ferrite was prepared by co-precipitation method and conventional solid-state method. Ni-Zn ferrite and carbon fiber was used as absorbent, and the waterborne polyurethane was as matrix. At the same time, polymer blending method was employed to produce electromagnetic wave absorbing composite films from the maxture of waterborne polyurethane, Ni-Zn ferrite and carbon fiber. Electromagnetic wave energy could be absorbed completely and dissipated into thermal energy in the composite films through filler of magnetic by spin rotation and domain wall motion, and used filler of electric by conductive network.
The result indicated that synthesis method of the Ni-Zn ferrite powder, the amount of fillers, and the thickness of thecomposite films may affect the effectiveness of the electromagnetic absorption. The produced composite films containing 20 vol% of 1300℃ heat treated Ni-Zn ferrites synthesis by solid state method with the thickness of 0.6 mm, the maximum electromagnetic absorbing effectiveness at 2560 MHz was -14 dB, and at frequency 30 MHz can be reached -29 dB. However, with additional carbon fibers added in this composite film, the maximum electromagnetic absorbing effectiveness at 2450 MHz could reach -18 dB and at 30 MHz was about -15 dB.

並列關鍵字

Ni-Zn ferrite ； Carbon Fiber ； Polymer Blending ； Waterborne Polyurethane ； Composite ； Electromagnetic Shielding ； Electromagnetic Absorbing Effectiveness

參考文獻

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