The Effect of Organic Compound Pyrolysis on Synthesizing Graphite Encapsulated Nickel Nanoparticles in an Arc-discharge System

• Main Authors: Yu-Chieh Huang, 黃郁傑
• Other Authors: Mao-Hua Teng
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/v7cmb9

碩士 === 國立臺灣大學 === 地質科學研究所 === 107 === 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.