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標題: The study on Nano-magnetic Composite Material and Its Microwave Absorption
作者: 蔡仲濠
Hao, Tsai Chung
關鍵字: Nano cobalt particle;奈米鈷粒子;Magnetic dispersion solution;Nano-magnetic composite material;Complex permeability;Microwave absorption;磁性分散液;奈米磁性複合材料;複數導磁係數;微波吸收
出版社: 化學工程學系
Nano-technology has been regarded as one of the important science and technology in this century. It's application includes photo-electric, material science, mechanics, and biotechnology. Recently, it is found that nano-magnetic composite material can produce the ferromagnetic resonance effect due to absorbing microwave in the wide frequency.
This investigation aims to use the oleic acid (9wt%) and nano-cobalt particles (30wt%) for fabricating nano-magnetic dispersion in heptane solution, and dry it to become composite powders and blend with epoxy resin for nano-magnetic composite material. Additionally, the free space reflection method is utilized to measure microwave absorption of nano-magnetic composite material with the incidence source of 3.5GHz to 17.5GHz microwave in the different thickness. As shown in the result from TGA test, the cobalt particle can be protected with the oleic acid from oxidation. In addition, in the range of 4GHz to 10GHz, the permeability absolute value of nano magnetic composite materials is -0.03 and less than -0.83 of sneok's limit for attenuate rate. It is worth mentioned that the refection loss of microwave is over 20dB ranging from 4 to 9GHz and reach 73dB at 4.4GHz in matching thickness 4.5mm of magnetic composite material with 46.2wt.% nano-cobalt particles.
In summary, the microwave absorber of nano-magnetic composites materials with low cobalt content has been successfully manufactured to reduce matching thickness and develop semiconductor microwave filter component, antenna materials, and radar absorber in the wide range of frequency in this study.

奈米科技已被認為本世紀最重要的產業之一,其涵蓋領域包括了光電、材料、機械、生物科技等,應用範圍相當廣泛。近年來,已有研究者發現奈米磁性複合材料(Nano-magnetic composite)具有寬頻段的微波吸特性,故本研究擬利用9wt%油酸及平均粒徑25nm的30wt%奈米級鈷粒子,以球磨分散製成奈米磁性分散液,並將其乾燥形成複合粉體,再與環氧樹脂掺合後,製作出奈米磁性複合材料,且在不同的厚度下,以自由空間反射法量測其微波吸收特性。結果顯示,在油酸吸附層的保護作用下,磁性複合材料中的奈米級鈷粒子具有良好的分散性及穩定性,並且由TGA測試得知,油酸吸附層具有保護鈷粒子避免其氧化的功能。此外,所製備的奈米磁性複合材料,於4GHz至10GHz的頻率範圍,其複數導磁性數的實部變化率最大僅有-0.085,遠低於氧化鐵的sneok極限值[24] -0.83,且由模擬計算結果得知,46.2wt%奈米鈷粒子含量的磁性複合材料可於4.5mm的最佳化厚度下及4GHz至9GHz的頻率範圍達到20dB的微波吸收率,其中在4.4GHz處可達72dB,因此,本研究所製備奈米磁性複合材料,已具有寬頻段微波吸收,低固含量及厚度薄的特性,可應用於半導體寬頻濾波元件、微波天線材料、雷達波吸收材料等開發。
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