Study On The Line Cold Plasma Jet

Plasma Jet as one kind of low temperature atmospheric plasma have been widen used in material fabrication and modification. The commonly used plasma jets mainly use cylindrical discharge cavity, and the aperture of the plasma jet is very small, so the plasma process efficiency is restricted. It is important to develop a large area plasma jet.In this thesis a co-axis cylindrical DBD linear plasma jet generator is developed. The linear plasma jets with 5 cm width are obtained by using N2 and Ar as working gas. The effect of gas pressure, flow mass, discharge voltage, absorption power and discharge chamber structure on the plasma jet length are investigated. It is found that the linear plasma length is lengthened and then saturated when gas pressure and flow mass is increased. The linear plasma length is enhanced when the discharge voltage is increased. The width of the open slit of the reactor has a strong influence on the plasma jet while the reactor dimension has no obvious effect.The plasma jets of nitrogen and Ar are diagnosed by using optical emission spectroscopy (OES) and the plasma component are analyzed. It is found that the main component existing in N2 plasma jet are N2 and a little of N,N_ and N2+ are not found. The intensity of OES are increased when discharge voltage and flow mass are increased. The rotational temperatures are acquired by comparing the measured and calculated spectra of the N2 second positive system ((?))380.4nm(v'=0,v"=2)line. As the gas temperature equal to the rotational temperature in the plasmas, it is obtained the gas temperatures from 290K to 350K in the plasmas. These temperatures are lower than that of damaging material surfaces, when this plasma applied to treat material surfaces.The surfaces of the PET film are modified by the linear plasma jet at atmospheric pressure. The PET film are characterized with water contact angle and X-ray photoelectron spectroscopy before and after the plasma treatment, Contact angle measurements showed that the contact angle decreased greatly, and XPS analysis showed that the oxygen functional groups such as C-O and O-C=O groups on the PET surface increased after treatment. The wettability of plasma-treated PET film is improved significantly, and the investigations shows outstanding aging property of the treated samples when put them in the ambient air for five days.