Papers by Keyword: Plasma Jet

Abstract: Various methods of gas-vortex stabilization in plasma torches for metal cutting are investigated. The influence of an angle of plasma-forming gas injection into the nozzle on kinematic characteristics of the plasma jet is shown. The increase in the radial component of the velocity at the output from the swirler makes it possible to increase the uniformity of velocity distribution and the kinetic properties of jet in the zone of influence on the cut metal. For the cutting of the thin sheet metals, it is advisable to use the technology of "narrow-jet plasma".

Abstract: Diamond crystals are successfully synthesized by irradiating DC arc plasma jet to the substrate set in a methanol solution. It is the important procedure to preheat the substrate by inert Ar plasma jet before introducing the methanol solution gas to the plasma jet gun. The effects of two experimental conditions, the incident power and the substrates, are investigated. In the case of the Si substrate, cubic crystalline diamond grains of same size are synthesized at the plasma power of 470W. High speed hetero epitaxy is expected by using this method. In the case of the tungsten carbide substrate, diamond crystals and carbon nanotubes are simultaneously synthesized at the plasma power of 260W. The catalytic effect of Co binder in the substrate may cause the chemical reaction of the nanotube synthesis.

Abstract: The analysis of several constructive solutions for metal cutting in plasmatrons is done. On the basis of the presented solutions, new plasmatrons for precision metals cutting are elaborated. This plasmatrons work using narrow jet plasma technologies and two air-gas paths. Principles, methods and complexities in design of this technology are presented. Also, several results of investigation of cutting quality and acoustic safety of new plasmatrons are presented. New metal cutting technology does not have similar solutions at the Russian market and has great advantages in comparison with traditional domestic and similar foreign plasmatrons.

Abstract: One way to increase the durability of the machine is active surface coatings using new technological processes such as thermal spray coatings, especially the plasma jet. Was made by coating nickel plating process of the plasma jet knife blade for removal of a group from the grower. In order to emphasize increasing the reliability of these knives by coating with nickel, they were mounted on a cultivator with a lot of knives witness, uncovered, and have been used extensively. Data on wear two groups of knives, coated with nickel and witness uncovered were recorded by photometric methods were processed and plotted statisitic. There was a significant decrease of 66.79% in average wear on the knife blades coated with nickel compared to the control, uncoated.

Abstract: Two kinds of multiple-pulse were reported on atmospheric plasma jet (APPJ) of dielectric barrier discharge (DBD) configurations in this study. Meanwhile, the investigation on electrical characteristics of APPJ in helium and helium/air was carried out with the aim of shedding light on the electrode parameters for dissipated power and jet length. The typical bacteria, E. coil, were employed to study the effect by the two APPJ devices (PJ-1 and PJ-2). For PJ-1, multiple-pulse appears in both sides of every half-cycle, but only in the positive half-cycle for PJ-2. A wider power electrode of PJ-1 and further distance from the nozzle to grounding electrode of PJ-2, whether in ambient helium or helium/air, are all conducive to improvement of dissipated power. With the increase of gas flow rate, the jet length will become longer at laminar flow mode, then get shorter, and a permanent to the end. Generally, the introduction of air leads a better sterilization effect, especially for PJ-1. Keywords: Atmospheric Pressure, multiple-pulse, Electrode parameters, dissipated power, jet length, plasma jet. PACS: 52.80.-s, 52.77.-j

Abstract: To study the friction and wear properties of S136/WC-Co friction pair, friction and wear tests in air jet, nitrogen jet and nitrogen cold plasma jet atmospheres are carried out. The morphology and composition of friction surface are analyzed by camera, scanning electron microscope and energy-dispersive X-ray spectroscope. The wear behaviors and mechanism of anti-wear of the three jets to S136 are also discussed. The experiment results prove that the reactive species in the nitrogen plasma jet contribute to the generation of oxidation film on the friction surface quickly to reduce the wear of S136/WC-Co friction pair in real-time.

Abstract: High speed Schlieren imaging, pressure tapping points and optical emission spectroscopy for temperature and heat flux data are essential measurement techniques for analysis of bow shock dispersion, aerodynamic performance or heat transfer of spacecraft in atmospheric re-entry. However, design and manufacturing of a high voltage pulsed-plasma jet for testing in a supersonic counterflow deserves careful examination. High voltage electrification combined with high temperature sparking between electrodes possesses several design difficulties and manufacturing challenges which need to be addressed that form the basis of the design principals and manufacturing methodology of an Apollo capsule pulsed-plasma jet for successful testing and experimentation of the model.

Abstract: Polyimide (PI) has good mechanical properties, heat resistance and low temperature performance, and thus shares a wide range of applications. Atmospheric pressure plasma jet was designed for polyimide films surface modification in this paper. The impacts of exposure time and gas ratio on the film surface morphology and property were studied. Scanning Electron Microscope (SEM) results prove that the treated film surface becomes rough and the contact angle decreases rapidly with exposing to plasma. The contact angle did not decrease anymore after extending plasma exposing time to 20 seconds Moreover the intensity of C=O absorption band increases as shown in the Fourier transform infrared spectroscopy (FTIR).

Abstract: Argon plasma jet in a single-electrode configuration was generated at low temperature and atmospheric pressure by 50 kHz radiofrequency power supply. Optical Emission Spectroscopy (OES) was used to investigate the local emissivity of argon plasma in the range between 200 and 1,100 nm. The spatial distribution of reactive species was measured at different distances of the plasma expansion from the nozzle exit such as 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 cm. These measurements were obtained to analyze the plasma parameters such as electron temperature and electron density. The effect of distances of the plasma expansion from the nozzle exit on the plasma parameters was studied. The main intensive argon lines were found in the region between 690 and 970 nm. The electron temperature was found in the range of 0.5-1.1 eV. The electron density was found in the range of 4.0x10¹²-1.2x10¹³ cm^-3. The plasma parameters strongly depended on the distances of the plasma expansion from the nozzle exit.

Abstract: Experimental system of CCD real-time acquisition is developed according to high temperature property of plasma jet. Mathematical model of gray image and jet temperature distribution is established and basic principles of the CCD collection is analyzed. It realizes acquisition by a common image acquisition card in LabVIEW environment and real-time display of jet. Jet is collected on the computer image processing by using IMAQ Vision, and it intuitive analyzes the shape and temperature distribution according to pseudo-color image processing results of the jet temperature field. Experimental results deepen understanding of the complex nature of plasma jet, which have a guiding significance on the plasma technology in materials processing application.