Analysis Of High Frequency Plasma Reactor For Preparing Nano-Particles

High frequency plasma technology is widely used in preparing nano materials, however study papers reported on HF-Plasma reactor is seldom. In this paper, accounting basic theory of chemical reaction engineering, the process of nano-powders material prepared by high frequency plasma chemical vapor deposition have been studied. According to steady state cylindrical and annular reactor generalization modeling of high frequency plasma, based on Greatz problem, two-dimension coupled mathematic models have been developed. The approximate solutions have been obtained by using Crank-Nicholson finite difference, and we have developed the general program for solving this kind of two-dimension partial differential equations. The method is used to give the numerical solution of distribution of temperature, reactant conversion and degree of supersaturation in high frequency plasma reactor. This paper. has discussed detaily influence of nondimensional numbers on temperature, reactant conversion and degree of supersaturation in high frequency plasma reactor, for example heat and mass Peclet numbers, Boltzmann number and so on. And this paper further investigated influence of plasma torch radiative transfer, axial convection and radial back mixing on temperature, reactant conversion and degree of supersaturation of conglomeration state physical parameter. Not only general theoretical frame which is used to analysis quantitativly influence of the heat and mass transfer in high frequency plasma reactor on nanophase materials nucleation and growth procedure, but also theoretical guide which is used to understand and design experiment of high frequency plasma reactor.HF-PCVD is a rapid and continuous process to prepare high-purityγ-Al₂O₃ nano powders.γ-Al₂O₃ Nano-microcrystals were prepared from aluminum chloride and oxygen with Ar torch by high frequency plasma chemical vapor deposition method (HF-Plasma CVD). The microcrystals were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the particles areγ-Al₂O₃ microcrystals in the form of sphere, and thier diameters are in the range of 20-50nm with a narrow size distribution. Theγ-Al₂O₃ particle mean diameter and diameter distribution can be controlled by changing flow rates of AlCl₃ feeding under certain operation conditions.