15 research outputs found
Electrical, Thermal and Optical Diagnostics of an Atmospheric Plasma Jet System
Plasma diagnostics of atmospheric plasmas is a key tool in helping to understand processing performance issues. This paper presents an electrical, optical and thermographic imaging study of the PlasmaStream atmospheric plasma jet system. The system was found to exhibit three operating modes; one constricted/localized plasma and two extended volume plasmas. At low power and helium flows the plasma is localized at the electrodes and has the electrical properties of a corona/filamentary discharge with electrical chaotic temporal structure. With increasing discharge power and helium flow the plasma expands into the volume of the tube, becoming regular and homogeneous in appearance. Emission spectra show evidence of atomic oxygen, nitric oxide and the hydroxyl radical production. Plasma activated gas temperature deduced from the rotational temperature of nitrogen molecules was found to be of order of 400 K: whereas thermographic imaging of the quartz tube yielded surface temperatures between 319 and 347 K.<br/
Destruction of chemical warfare surrogates using a portable atmospheric pressure plasma jet
Today’s reality is connected with mitigation of threats from the new chemical and biological warfare agents. A novel investigation of cold plasmas in contact with liquids presented in this paper demonstrated that the chemically reactive environment produced by atmospheric pressure plasma jet (APPJ) is potentially capable of rapid destruction of chemical warfare agents in a broad spectrum. The decontamination of three different chemical warfare agent surrogates dissolved in liquid is investigated by using an easily transportable APPJ. The jet is powered by a kHz signal source connected to a low-voltage DC source and with He as working gas. The detailed investigation of electrical properties is performed for various plasmas at different distances from the sample. The measurements of plasma properties in situ are supported by the optical spectrometry measurements, whereas the high performance liquid chromatography measurements before and after the treatment of aqueous solutions of Malathion, Fenitrothion and Dimethyl Methylphosphonate. These solutions are used to evaluate destruction and its efficiency for specific neural agent simulants. The particular removal rates are found to be from 56% up to 96% during 10 min treatment. The data obtained provide basis to evaluate APPJ’s efficiency at different operating conditions. The presented results are promising and could be improved with different operating conditions and optimization of the decontamination process
Influence of gas type on the thermal efficiency of microwave plasmas for the sintering of metal powders
Microwave plasmas have enormous potential as a rapid and energy efficient sintering
technology. This paper evaluates the influence of both plasma atmosphere and metal
powder type on the sintering temperatures achieved and the properties of the sintered
powder metal compacts. The sintering is carried out using a 2.45 GHz microwave-plasma
process called rapid discharge sintering (RDS). The sintering of three types of metal
powder are evaluated in this study: nickel (Ni), copper (Cu) and 316L stainless steel (SS).
An in-depth study of the effects of the plasma processing parameters on the sintered
powder compacts are investigated. These parameters are correlated with the mechanical
performance of the sintered compacts to help understand the effect of the plasma heating
process. The substrate materials are sintered in four different gas discharges, namely
hydrogen, nitrogen oxygen and argon. Thermocouple, pyrometer and emission
spectroscopy measurements were taken to determine the substrate and the discharge
temperatures. The morphology and structure were examined using scanning electron
microscopy and x-ray diffraction. The density and hardness of the sintered compacts were
correlated with the plasma processing conditions. As expected higher densities were
obtained with powders with lower sintering temperatures i.e. nickel and copper when
compared with stainless steel. Under the power input and pressure conditions used the
highest substrate temperature attained was 1100
∘
C for Cu powder sintered in a nitrogen
atmosphere. In contrast under the same processing conditions but in an argon plasma, the
temperature achieved with SS was only 500
∘
C. The effect of the plasma gas type on the
sintered powder compact chemistry was also monitored, both hydrogen and nitrogen
yielded a reducing effect for the metal in contrast with the oxidising effect observed in an
oxygen plasma.Science Foundation IrelandAuthor has checked copyrightAD 22/01/201