R.Y. Hong

An easy approach to encapsulating Fe3O4 nanoparticles in multiwalled carbon nanotubes

Carbon nanotubes filled with magnetic materials are very interesting as new materials for applications in biomedicine. A simple and efficient method was developed to encapsulate Fe3O4 nanoparticles in multiwalled carbon nanotubes (MWCNTs). Transmission and scanning electron microscopy, energy dispersive X-ray analysis, and X-ray powder diffraction measurements confirmed that the Fe3O4 nanoparticles are encapsulated in the MWCNTs. The magnetic properties of the MWCNTs and the Fe3O4-filled MWCNTs were measured using a vibrating sample magnetometer. Results showed that the Fe3O4-filled MWCNTs exhibited superparamagnetism at room temperature and possessed a higher saturation magnetization (Ms) (around 13.15 emu/g) than that of the unfilled ones (around 0.35 emu/g). The MWCNTs encapsulating Fe3O4 nanoparticles have potential applications in engineering and medicine.

Thermodynamic and particle-dynamic studies on synthesis of silica nanoparticles using microwave-induced plasma CVD

Abstract Recent studies on preparation of silica nanoparticles using plasma chemical vapor deposition (PCVD) are briefly reviewed. A microwave (MW) PCVD apparatus was set up to synthesize silica nanoparticles by the oxidation of silicon tetrachloride. Computations based on the minimization of Gibbs free energy were conducted to find the equilibrium compositions, the optimal reaction temperature, the suitable mole ratio of oxygen to silicon tetrachloride, and the best inlet positions of silicon tetrachloride. The mean particle diameter and specific surface area were obtained from particle dynamic simulation. Experimental investigation verified the results obtained from the thermodynamic and particle-dynamic computations, and showed that the maximum production rate of silica was more than 1 kg·h −1 with the full MW input power.

FLUIDIZATION OF FINE POWDERS IN FLUIDIZED BEDS WITH AN UPWARD OR A DOWNWARD AIR JET

The hydrodynamic behavior of fine powders in jet-fluidized beds was studied numerically and experimentally. The starting point of numerical simulation was the generalized Navier-Stokes (N-S) equations for the gas and solids phases. The κ-e turbulence model was used for high-speed gas jets in fluidized beds. Computation shows that a suitable turbulence model is necessary to obtain agreement between the simulation and literature experimental data for a high-speed gas jet. The model was applied to simulating the fluidization of fine powders in fluidized beds with an upward or a downward air jet. An empirical cohesion model was obtained by correlating the cohesive force between fine particles using a cohetester. The cohesion model was embedded into the two-fluid model to simulate the fluidization of fine powders in two-dimensional (2-D) beds. To study the fluidization behavior of fine and cohesive powders with a downward jet, experiments were performed in a 2-D bed. Agreement between the computed time-average...