- 學位論文
以電弧法合成石墨包裹鎳奈米晶粒並探討有機物熱裂解反應對產物之影響研究
The Effect of Organic Compound Pyrolysis on Synthesizing Graphite Encapsulated Nickel Nanoparticles in an Arc-discharge System
摘要
石墨包裹鎳奈米晶粒(graphite encapsulated nickel nanoparticles, Ni-GEM)是一種內核為鎳奈米金屬，外部為層狀石墨的核殼複合結構材料；因穩定的石墨殼層可以保護內部金屬，所以能夠展現被包裹金屬之多元特性與應用潛力。而Elliott等人於1997年提出的二步驟機制(two-step mechanism)是目前最能合理解釋以電弧法合成GEM晶粒的機制，並根據機制可知，於合併區內提供足量且均勻的碳蒸氣，是提升GEM晶粒之包裹良率與產率最根本的方法。 為了探討不同均勻度及形態的碳蒸氣對產物的影響，本研究選用工業中常見的膠體酚醛樹脂，在電弧區內提供初始碳源，並添加液態有機分子，如苯(benzene, C6H6)及環己烷(cyclohexane, C6H12)，透過艙內間接加熱之坩堝蒸發後，有機蒸氣會隨著熱對流，由合併區外圍向內部提供碳源。根據產物之合成效率結果，單純添加3 g之酚醛樹脂作為碳源時，可以得到29%的最佳包裹良率與20 g/h之產率；而當添加了20 ml之苯與環己烷蒸氣後，其產率可達 29 g/h，並大幅提升包裹良率達80%。根據奈米顆粒之表面形態進行分類，可以觀察到獨特的分佈現象，例如使用酚醛樹脂與額外添加環己烷之產物具有約40 nm之大粒徑與小於5 nm之薄石墨層；反之，使用苯蒸氣之產物則具有20 nm之小粒徑與5-10 nm厚的石墨殼層。 本研究依照實驗結果並搭配烴類的熱裂解反應文獻，提出新的「三步驟」合成模型來解釋產物差異。苯與環己烷在熱裂解過程中除了具有不同的起始反應溫度外，亦會發生不同程度的縮合或降解反應，進而影響產物之最終形態。 最後，為了探討運作模型之適用性，本研究也嘗試合成低熔點之Cu-GEM，並使用具有相似性質之萘蒸氣進行Ni-GEM之合成，冀希建立相關初步概念假說，以提供未來深入研究之基礎。
並列摘要
Graphite Encapsulated Nickel (Ni-GEM) nanoparticles are core-shell composite-structured materials with an inner core of nano-metal and an outer shell of graphite. The internal metal can be preserved and exhibit its characteristics because of the protection of the stable graphite shell. For example, the magnetic and microwave adsorption properties can be used in several fields, i.e., as the tracer in a structural geological survey or the surface coating of stealth aircraft in the national defense industry. According to the two-step mechanism proposed by Elliott et al. (1997), the most fundamental way to improve the encapsulation efficiency and production rate of GEM is to provide sufficient uniform carbon vapor in the coalescence area. In order to investigate the effect of using different types and uniformity of the carbon vapors on products, phenol formaldehyde resin is used as the initial carbon source; besides, benzene and cyclohexane were injected into the heated alumina crucible to form vapors, providing carbons outside-in of the coalescence area. According to the results, simply adding 3 g of phenolic resin as the carbon source can obtain the best encapsulation efficiency of 29% and production rate of 20 g/h; when 20 ml of benzene and cyclohexane vapor were added, the production rate was 29 g/h, and the encapsulation efficiency was 80% for both. Moreover, the morphologies of nanoparticles show an interesting trend, that is, the Ni-GEM particles made from phenolic resin or cyclohexane vapors result in similar particle size (40 nm) with a thinner shell (less than 5 nm). However, the use of benzene vapors results in smaller particle size (20 nm) and thicker shell (5-10 nm) than ever before. According to the pyrolysis literature on hydrocarbons, it is known that the initial reaction temperature and reaction path of cyclohexane and benzene totally differ. Thus, a new “three-step” working model, in which the nanocarbon materials formed by the organic compounds will directly affect the experimental results, was proposed using the pyrolysis reaction. Last but not least, based on the applicability of this model, we aimed to synthesize Cu-GEM by this synthesis method and Ni-GEM with naphthalene vapor. This procedure is expected to establish a preliminary concept hypothesis for related research, and provide the foundation for more in-depth materials science research in the future.
參考文獻
延伸閱讀
- 邱志成（2012）。以高合成效率的製程方法合成石墨包裹奈米鐵、鈷、鎳以及銅晶粒之初步研究〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2012.02599
- 蔡昕晟（2015）。利用石墨烯結合金屬奈米結構研究兆赫波段之表面電漿極化子共振現象〔碩士論文，國立交通大學〕。華藝線上圖書館。https://doi.org/10.6842/NCTU.2015.00585
- Hao, Y. C. (2015). PAN/氧化石墨烯奈米複合材料之熱行為與形態學研究 [master's thesis, National Tsing Hua University]. Airiti Library. https://doi.org/10.6843/NTHU.2015.00508
- 黃家慶（2022）。石墨烯奈米流體應用於電子晶片散熱之研究〔碩士論文，國立臺灣師範大學〕。華藝線上圖書館。https://doi.org/10.6345/NTNU202200838
- 李尚實（2006）。Dispersion of the Graphite Encapsulated Nickel Nanocrystals with Different Particle Sizes in the NP-9 Colloidal System〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2006.02924