This paper presents the fabrication and a spectroscopic study of a stable radiofrequency dielectric barrier discharge (RF DBD) in Ar with a novel dielectric, anodic alumina, at atmospheric pressure. Dielectric electrodes are fabricated from commercially available low cost impure aluminum strips by a two-step anodization process in 0.3 M solution of oxalic acid. The discharge is found to be stable with excellent spatial uniformity for the RF input power range of 30∼80 W. Excitation and rotational temperatures measured in the experiment range of 1472∼3255 K and 434∼484 K, respectively, as the input power changes from 30 W to 80 W. These temperature ranges are suitable for surface modification applications.
An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the α and γ modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in γ mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.
A comparison of the visual appearance of the glow modes in radio frequency (RF) atmospheric pressure glow discharge (APGD) with bare electrodes and dielectric barrier discharge (DBD) using anodized electrodes is presented. In α mode, both RF APGD and RF DBD remain volumetric, stable, and uniform. In γ mode, the RF APGD shrinks into a constricted plasma column. On the other hand, RF DBD in γ mode is stable, horizontally uniform, and retains the same volume as that in α mode without plasma constriction.
IndexTerms-Anodic alumina, dielectric barrier discharge (DBD), glow modes, mode transition, radio frequency atmospheric pressure glow discharge (RF APGD). L ARGE area, stable, and uniform atmospheric glow discharges are required for applications in many scientific disciplines. The radio frequency atmospheric pressure glow discharge (RF APGD) is sustained either in large area and stable α mode of small current resulting into poor reactive plasma species or the constricted and unstable γ mode of large current and therefore generating higher concentration of reactive plasma species [1], [2]. In other words, plasma stability and plasma reactivity of RF APGD are often mutually exclusive of each other. This paper shows that the use of anodized electrodes in RF APGD enables large area and stable γ mode over large discharge current.The RF APGD is generated between the two parallel aluminum electrodes (4 × 5 cm 2 ) with 1.2-mm gas gap by feeding industrial grade helium at a flow rate of 2 standard liters per minute. The top electrode is connected with the RF power supply (Comdel, CX 600AS, 13.56 MHz) and the bottom electrode is grounded. The discharge current and the applied voltage are measured by a wide band current (Tektronix P6021) and voltage (Tektronix P5100) probes. The pictures of the discharge are taken by focusing a digital camera (Kodak C 913 with exposure time 2 ms) through the microscope. The RF dielectric barrier discharge (RF DBD) employed the same electrode unit apart from the two electrodes being anodized in 0.3-M oxalic acid solution Manuscript
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