A nitrogen microplasma jet operated at atmospheric pressure was developed for treating thermally sensitive materials. For example, the plasma sources in treatment of vulnerable biological materials must operate near the room temperature at the atmospheric pressure, without any risk of arcing or electrical shock. The microplasma jet device operated by an electrical power less than 10 W exhibited a long plasma jet of about 6.5 cm with temperature near 300 K, not causing any harm to human skin. Optical emission measured at the wide range of 280-800 nm indicated various reactive species produced by the plasma jet.
A portable microwave plasma torch at atmospheric pressure by making use of magnetrons operated at 2.45 GHz and used in a home microwave oven has been developed. This electrodeless torch can be used in various areas including commercial, environmental and military applications. For example, perfluorocompounds (PFCs), which have long lifetimes and serious global warming implications, are widely used during plasma etching and plasma-assisted chamber cleaning processes in chemical vapour deposition systems. The microwave torch effectively eliminates PFCs. Efficient decomposition of toluene gas indicates the effectiveness of volatile organic compound eliminations from industrial emission and the elimination of airborne chemical and biological warfare agents. The microwave torch has been used to synthesize carbon nanotubes in an on-line system, thereby providing the opportunity of mass production of the nanotubes. There are other applications of the microwave plasma torch.
We propose a plasma-jet device with a micrometer-sized nozzle array for use in a cancer therapy. Also, we show the biological effects of atmospheric-pressure plasma on living cells. Nitrogen-plasma activated a surrogate DNA damage signal transduction pathway, called the ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 pathway, suggesting that the nitrogen-plasma generates DNA double-strand breaks. Phosphorylation of H2AX and p53 was detected in the plasma-treated cells, leading to apoptotic cell death. Thus, an effect for the nitrogen plasma in the control of apoptotic cell death provides insight into the how biological effects of the nitrogen-plasma can be applied to the control of cell survival, a finding with potential therapeutic implications.
Superhydrophobic carbon nanotubes (CNTs) were prepared by low-pressure CF4 glow plasma to provide roughness and fluorination in CNTs. The water droplet falling freely on the superhydrophobic CNT powders bounced dynamically. The superhydrophobicity resulted from the combined effects of the chemical modification and surface roughness. Using the contact angles obtained from the capillary rise method based on the Washburn equation, the total surface free energy of CNT powder treated by CF4 plasma for 20min was calculated to be drastically decreased from 27.04to4.06×10−7mJ∕m2.
Pyrite (FeS2) decomposition in He, N2, CO2‐CO‐SO2, O2‐CO2 and H2S‐H2 gas mixtures was studied from 400–590°C using optical microscopy, X‐ray diffraction, electron microprobe analyses, and gas chromatography. The rate constants were determined from the weight loss and the thickness change of pyrite in reacted samples. The temperature dependent composition of the product, pyrrhotite (Fe1‐xS), was measured by electron microprobe analysis and X‐ray diffraction. Pyrite decomposition to pyrrhotite and sulfur vapor (dominantly S2) was observed in all gases and follows linear kinetics. The apparent activation energy of pyrite thermal decomposition is 297 + 34 kJ mol−1 in inert gases (e.g. He, N2), and 275 + 20 kJ mol−1 in purified CO2 and in low concentration CO‐SO2 gas mixtures with CO2. The rate constants are the same regardless of gas composition at a given temperature. In oxidizing (O2‐CO2) or reducing (H2S‐H2) gas mixtures, the rate constants are larger than that in inert gases because additional reactions between pyrite and oxidizing/reducing gases accelerate the overall process while reducing the apparent activation energies. A mechanism of pyrite decomposition, which explains our experimental results, as well as the discordant activation energy data in the literature, is proposed.
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