Study of the Effect of Methanol Evaporation Rate on Packing of Graphite Encapsulated Nickel Nanoparticles
Date Issued
2010
Date
2010
Author(s)
Hsiao, Yuan-Lung
Abstract
Graphite Encapsulated Metal (GEM) nanoparticles is a spherical composite material with a core(metal)/shell(carbon) structure and its diameter is in a range of 5 to 100 nm. Because the outer shell protects the inner metal nanoparticles, the materials remain stable in strong acid as well as at high temperature in an oxygen-free environment. It is widely used in environmental implement, scientific research, biomedical applications, and military. GEM can be packed to form high density bulk by the magnet force and the problem of aggregation can be solved in our previous lab studies. This study not only utilizes other forces or set up several parameters to form high density bulk, but also investigates the mechanism of forming high density bulk of GEM.
These experiments are designed as following: (1) centrifugal force, (2) gypsum casting, and (3) deposition method to form high density bulk. The results of centrifugal force show that high density, large volume bulk of GEM can be formed but the results of gypsum casting cannot. The results of deposition method obviously show that the density of GEM is increasing with increasing temperature, whether the magnet force was conducted or not. In fact, the liquid bridge force can explain the different evaporation rates will affect Ni-GEM bulk density when changing temperatures. Besides, this study also provides the theoretical calculation of the effects among Van der Waals force, the magnetic force, and the liquid bridge force. The results suggest that the liquid bridge force predominates of dense GEM bulk forming in the process. The liquid bridge force is a hundred times larger than the magnetic force and 10 thousand times larger than Van der Waals force. In summary, this study not only provides experimental results and theoretical calculations to prove that the dominated force is the liquid bridge force, but also provide another method to form the high density bulk of Ni-GEM.
Subjects
graphite encapsulated nickel nanoparticles
liquid bridge force
methanol
temperature
evaporation rate
Type
thesis
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