Simulation Of Argon And Ammonia Mixture Discharges

Ar/NH3admixture plasma discharge has an extremely important role in portable hydrogen generating device, environment protection, silicon nitride thin film deposition, magnetic fluid preparation and nanotube modification and so on. Although there were the partial experimental results and theoretical calculation results on Ar/NH3admixture plasma discharge, complex components and the densities significantly changed with time, and the complex equipments have been to measure the spatial and temporal parameters. The direct experimental diagnosis on the atmospheric pressure plasma discharge is still limited at present. The fluid model of the Ar/NH3admixture plasma discharges has been developed to solve the continuity equations for electron, ions and radials and the electron energy conservation equation and Poisson’s equation at the different discharge mechanism. The plasma parameters how to influence on the spatial distribution of the main radicals and ions of ammonia are studied by simulation.The research contents of the thesis are summarized as follows:In chapter one, the applications and the research progress of theory and experiment on argon and ammonia admixture discharge are described, and the significance and the main content of the research are introduced.In chapter two, the one-demonsional fluid model is adopted to simulate Ar/NH3admixture direct current discharge in planar electrode at atmospheric pressure. The ammonia concentration and the pressure how to effect on the particle density in the discharge mode are discussed. It found that the main ions are Ar2+and Ar+, the Ar2+density is about one order higher than the Ar+density.The density of NH2increases with pressure increased which is more obvious than that of NH. The proportion of NH4+density to that of ammonia ions becomes larger, while the NH2-density has an opposite trend when the ammonia concentration and pressure increased. And the density of NH+is significantly lower than that of the other positive ammonia ions. The results of two-dimensional fluid model are compared with those of one-dimensional fluid model.In chapter three, the one-demonsional fluid model is used to calculate an atmospheric pressure Ar/NH3admixture dielectric barrier discharge between the coaxial electrodes. The spatial distribution of the ammonia radials and the impact of ammonia concentration on the particle density, gas temperature and electron temperature are discussed respectively. It found that in the discharge mode the H2density is more than that of H. NH4+becomes the most important ammonia ion. The Ar2+ion density is higher than that of Ar+ion as ammonia concentration is low.Along with ammonia concentration increased, a large number of NH, H2and NH2are generated by the ammonia decomposition, and then Ar2+is consumed by reaction with them, it makes the Ar+ion density is higher than that of Ar2+ion. Along with ammonia concentration increased, gas temperature slightly increased, while electron temperature is slightly lower.In chapter four, the two-dimensional axisymmetric fluid model is used to simulate Ar/NH3admixture microwave electron cyclotron resonance discharge at low pressure. The impact of pressure and microwave power on the particle density is discussed. It found that the density of electron and the ammonium ions increased with the microwave power increased, while the uniformity of the spatial distribution is decreased. The NH3+density sequentially higher than that of the NH2+, NH4+and NH+ions at low pressure.In chapter five, the two-dimensional hybrid model is adopted to investigate ammonia concertion how to influence on the Ar/NH3admixture discharge in the magnetized direct current planar device at low pressure.lt found that the Ar+density is signficantly higher than the Ar2+density at5mTorr, and the most ammonia ion is NH3+, sequentially followed by NH2+, NH4+and NH+. The main charged particles density is lower, and the spatial distribution is slightly uniform, and the electron temperature is slightly increase as the volume ratio of argon and ammonia is1:1.