奈米碳管/磁性顆粒/PDMS複合材料內部結構及壓敏性質

The relation between internal structures and pressure-sensitive properties of carbon nanotube/magnetic particles/PDMS composite

周哲緯(Jhe-Wei Jhou)

指導教授 ： 江宏仁

國立臺灣大學/工學院/應用力學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100601

摘要

奈米碳管具備優異的機械及電學性質因此被廣泛地運用在複合材料中，由於奈米碳管為非對稱性材料，能控制其在複合材料中的方向及排列可使複合材料性質受到控制。目前控制奈米碳管排列的方式主要有電場及磁場的方式，電場排列的方式由於需要使用高電壓，在製作上的難度及危險性較高；磁場排列的方式則需要對奈米碳管進行預處理才可進行排列。在本研究中，利用混合磁性顆粒至多壁奈米碳管/PDMS混合物中，讓奈米碳管能在磁場下被排列。
在本研究中，混合了不同奈米碳管及四氧化三鐵比例的水溶液，測試其受磁鐵吸引的速率，觀察到奈米碳管受磁鐵吸引的速率會隨著磁性顆粒添加量增加而上升。由於前述的觀察，本研究使用添加四氧化三鐵的方式來製作壓敏材料，藉此達到控制壓敏材料中奈米碳管排列之方式。
在製作壓敏材料的過程中，施加磁場能在壓敏材料中形成長條狀結構，實驗中分析了不同多壁奈米碳管、四氧化三鐵添加比例對結構的影響，觀察到長條狀結構隨著四氧化三鐵添加量的增加，形成的速率有顯著地提升。接著，對製作完成的壓敏材料進行了各種測試，發現長條狀的結構能提高壓敏材料的導電性，並觀察到導電各向異性；材料的滲透閾值從1.3wt%多壁奈米碳管添加量降低到1.2wt%。在對感測器壓阻性質及應力應變性質的量測中，發現電阻值因奈米碳管的排列結構而降低，彈性模數則是因為孔洞結構而降低。最後，量測了四氧化三鐵的粒徑大小及奈米碳管的磁性，發現兩種材料皆為具鐵磁性的材料，四氧化三鐵的飽和磁化量比奈米碳管的飽和磁化量高出約兩個數量級。
針對實驗中所觀察到的現象，本研究解釋了多壁奈米碳管/四氧化三鐵/PDMS混合物在磁場下排列的現象，在磁場下被磁化的磁性顆粒會產生局部磁場彼此吸引聚集，並吸附於奈米碳管上殘留的磁性顆粒，因此奈米碳管的磁性提升，能隨著磁場排列成長條狀結構。

關鍵字

奈米碳管 ； 磁性顆粒 ； 壓敏感測器 ； 應變感測器 ； 複合材料

並列摘要

Carbon nanotubes are widely used in composite materials due to their excellent mechanical and electrical properties. Because carbon nanotubes are asymmetrical materials, the ability to control their direction and alignment in the composite material may control the properties of the composite material. Nowadays, methods of controlling the alignment of carbon nanotubes mainly include applying an electric field and applying a magnetic field. The method of applying the electric field requires the use of high voltage, which is difficult and dangerous to implement; Method of applying magnetic field requires the use of pretreated carbon nanotubes. In this study, the effect of adding magnetic particles in the carbon nanotube/PDMS mixture is studied.
In this study, water solutions with different ratios of carbon nanotubes and ferrosoferric oxide particles are mixed and the rate of aggregation of carbon nanotubes and ferrosoferric oxide particles by the magnet is measured. The rate of aggregation of carbon nanotubes and ferrosoferric oxide particles by the magnet increases with the increase in the number of magnetic particles added. After showing the interaction between carbon nanotubes and ferrosoferric oxide particles, adding ferrosoferric oxide particles is used to prepare pressure-sensitive material, and to control the alignment of carbon nanotubes in pressure-sensitive materials.
In the process of preparing the pressure-sensitive material, long structures form in the pressure-sensitive material due to additional ferrosoferric oxide particles. In the experiment, the influence of different multi-wall carbon nanotubes to ferrosoferric oxide particles ratios on the structures are analyzed. With the increase of ferrosoferric oxide particles addition, the rate of formation of long strip structures increases. It is found that the long strip structures can improve the conductivity of the pressure-sensitive material and conductivity anisotropy; The percolation threshold of the material is reduced from 1.3wt% multi-walled carbon nanotubes addition to 1.2wt%. In the measurement of the piezoresistive properties and stress-strain properties of the sensor, it is found that the resistance is reduced due to the alignment of carbon nanotubes, and the elastic modulus is reduced due to the hole structures. Finally, the particle size of ferrosoferric oxide particles and the magnetism of carbon nanotubes are measured, and it is found that both materials are ferromagnetic. The saturation magnetization of ferrosoferric oxide particles is higher than that of carbon nanotubes about two orders of magnitude. Finally, the possible mechanisms for the observed phenomenon are discussed. Magnetic particles magnetize under the magnetic field and generate a local magnetic field, so magnetic particles absorb the remaining magnetic particles on the carbon nanotubes.

並列關鍵字

carbon nanotube ； magnetic particle ； pressure sensor ； strain sensor ； composite

參考文獻

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