Plasma Chemistry and Plasma Processing

Electrical and plasma properties of a U-shaped internal inductively coupled plasma (ICP) source with/without a Ni-Zn ferrite module installed above the ICP antenna were investigated. By installing the ferrite module on the antenna, the increase of plasma density and the decrease of plasma potential could be observed. The increase of plasma density was related to the efficient inductive coupling to the plasma by concentrating the induced magnetic field between the antenna and the substrate. At 800 W of ICP power and 20mTorr Ar, a high density plasma on the order of 4.5′1011/cm3 could be obtained.

A plasma-assisted synthesis of TiO2/SnO2 nanocomposite is described. In this approach, a precursor containing a mixture of [TiCl3 and SnCl2] exposed to electric discharge was oxidized by plasma-generated reactive species (HO·/H2O = 2.85 eV/SHE). SnO2 microstructures with a diameter of 10–40 µm were coated by thin layers TiO2 nanorods with mean diameter of 6–8 nm. The obtained TiO2/SnO2 nanocomposite was characterized by transmission and scanning electron microscopy, X-ray diffraction and Fourier transform infrared. TiO2/SnO2 nanocomposite was found to be a promising new material for the photocatalytic discoloration of aqueous Remazol Brilliant Blue-R dye under daylight and UVA light sources, due to the combined effects of large specific surface area and heterojunction which efficiently separates the electron–hole pairs delaying the charge recombination. The leaching test indicated that the nanocomposite is stable easily reusable.

This paper reports the study of the Kr–Cl2 plasma chemistry in terms of the homogenous model of a dielectric barrier discharge and for two kinds of the applied voltage excitation shape. The effect of Cl2 concentration in the gas mixture, as well as gas pressure and power frequency on the discharge efficiency and the 222 nm photon generation, under typical experimental operating conditions, have been investigated and discussed. Calculations suggest that the overall conversion efficiency from electrical energy to ultraviolet emission in the lamp is in the range of 4.4–12 %, and it will be very affected at high chlorine percentage (>1 %) and high gas pressure (>200 Torr). A comparison between the sinusoidal and the burst excitation waveforms reveals that the burst excitation method provides an enhanced light source performance compared to the sinusoidal wave.

The super-hydrophobic nano-films were synthesized by atmospheric pressure plasma jet using hexamethyldisilazane. In this paper, the atmospheric pressure plasma jet reacting with air was used to determine the formation of plasma polymerized nano-film. The atmospheric pressure plasma polymerized nano-film surface properties were determined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic forced microscopy. Specifically, it has been observed that atmospheric pressure plasma polymerization with the appropriate monomer gas flow rate cause the formation of the super-hydrophobic film. The surface properties of atmospheric pressure plasma polymerized nano-films were determined as the Cassie–Baxter state. It was examined that super-hydrophobic nano-film surface exhibits the organosilicon sphere stacking structure. Such sphere stacking structure does not only cause the hydrophobicity, it also stabilizes the Cassie regime, and thus favors the water repellency.

In this work, starch has been used to enhance the oxygenate formation directly from methane and carbon dioxide using dielectric-barrier discharges (DBDs). The use of starch inhibits the formation of liquid hydrocarbons and significantly increases the selectivity of oxygenates. Oxygenates produced include primarily formaldehyde, methanol, ethanol, formic acid, and acetic acid. The total selectivity is about 10–40% with conversion of methane and carbon dioxide of about 20%. Lower methane feed concentration favors the production of oxygenates, and higher feed flow rate leads to higher selectivity of oxygenates in the presence of starch.