聚苯胺／銀奈米複合材料之介電性質分析

Dielectric Properties of Polyaniline／Silver Nanocomposites

張家豪(Chia-Hao Chang)

指導教授 ： 許經夌

中原大學/理學院/物理研究所/碩士(2011年)

https://doi.org/10.6840/CYCU.2011.00101

摘要

摘要
本實驗使用未經質子酸摻雜之聚苯胺粉末(100nm~200nm)與不同比例之(重量百分比)奈米銀粒子(~150nm)均勻混合後壓製成圓錠並分析其電性變化。實驗中我們發現當銀粒子的體積百分比達6%時就已發生展透效應而遠小於古典理論的展透閥值16%，而其主要原因為銀粒子的聚集所造成，此時電導率為1.94×10-2S/cm。而未混入銀粒子之聚苯胺的電導率為2.63×10-8 S/cm。而在介電性質的分析方面，我們發現當展透效應發生時其相對介電常數為負值，因此我們引用了電子氣體模型來解釋其介電行為。而在交流電導率的量測方面我們引用了Power law理論，在三維空間中臨界指數約為0.7，而我們的估算值大約是0.43，這也可以說明此實驗的展透閥值與古典不符的原因。
而對於不同壓錠壓力的複合材料其直流電導率會隨壓力的增加而變大，經過熱處理後發現壓力較小的樣品其電導率有下降的趨勢，而交流電導率也有類似的行為，而相對介電常數會隨著壓錠壓力的增加而上升，隨頻率的增加而下降。
最後，在本實驗中我們將聚苯胺／銀奈米複合材料做變溫並量測其電性，並觀察其在低溫底下之I-V曲線之變化。

關鍵字

聚苯胺 ； 銀複合材料

並列摘要

Abstract
In this study, we mixed dedoped polyaniline powder (average diameter of 150 nm) with silver nanoparticles (~ 150nm) in various ratios uniformly. These nanocomposite mixtures were compressed into pellets and their electrical properties were analyzed. We found that when the volume-volume percentage (v/v%) of silver particles was over 6%, percolation effect occurred, and the percolation threshold was much less than that (~16v/v%) of the classical percolation theory. This phenomenon might be due to the aggregation of silver particles in the mixing process. The conductivity of the percolated nanocomposite sample was 1.94×10-2 S/cm, which was much higher than that of pure polyaniline (2.63×10-8 S/cm). In the analysis of the dielectrical properties of the samples, the relative dielectric constant was found to be negative when the percolation effect occurred. It could be explained by referring the electron gas model. The results of our AC conductivity measurements also showed that the percolation threshold of our experiment is different from that of the classical theory.
The pressure of the sample compress process also affected the DC conductivity of the nanocomposites. The conductivity increased with increasing pressure. After annealing treatment, we found that the DC conductivity of the sample compressed by lower pressure decreased obviously, and the AC conductivity had a similar behavior. The relative dielectric constant increased with increasing pressure, and decreased with increasing frequency.
Finally, the polyaniline/Ag nanocomposites were investigated through variable temperature electrical measurements, and the I-V curves of the nanocomposites were analyzed at low temperature.

並列關鍵字

polyaniline ； ag composites

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