Diagnosis Of The Plasma Jet And The Preparation Of Powder Silica At Atmosphere Pressure

Atmospheric-pressure non-thermal plasma jets?APNP-Js? are widely used in bio-application, surface modification, surface decontamination, and deposition due to its rich chemical active particles, low gas temperature and flexible operating process et al.. In order to have better control on the application of the laboratory as well as industrial plasma,it is necessary to understand the plasma jet properties. In addition, the preparation of silica by using plasma chemical vapor method at atmospheric pressure are widely concerned because of its advantages — large, complex and sealed vacuum reaction equipment are not necessary. In this paper, we make research primarily on the diagnosis of the plasma jet and the preparation of silica through chemical vapor method.In dielectric barrier helium plasma jet, we use a dielectric probe to measure the electron density and electron density as a function of the applied voltage along the jet axis outside the dielectric layer. The results show that the electron density is about 10¹¹ cm^-3, and it increase with the applied voltage.On the other hand, in dual assisted grounded electrode dielectric barrier discharge, we measure the jet electron density, plasma bullet velocity and ion-neutral particles collision frequency in glow discharge and filamentary discharge mode respectively. Under the glow discharge mode, the estimated electron density is on the order of 10¹¹cm^-3. Ion-neutral particles collision frequency in the radial direction is about 10⁷ Hz. In the axial direction, the result turns to be about 10¹⁰ Hz. However, the ion-neutral particles collision frequency in the radial direction is about 10⁸ Hz while under the filamentary discharge mode. In this process, additional diagnostic equipment are not required because the current waveforms are from the three ground rings. With this information, the plasma jet properties are obtained, which is veryconvenient.On the preliminary study of the preparation of silica?SiO₂? through chemical vapor method, some off-white powders were prepared with radio-frequency capacitive coupling discharge by using the hexamethyldisiloxane?HMDSO? as the preparation sources. The X-ray diffraction?XRD? result showed that the main composition of the powder is the amorphous SiO₂. Furthermore, on the preparation of SiO₂ with dielectric barrier discharge, we roughly measure the particle size distribution of the SiO₂ with the nano particle analyzer?Nanotral Wave?. The results are about a few micron, and the particle size increase when the concentration of the particles increase.