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Please use this identifier to cite or link to this item: http://hdl.handle.net/10087/6247

Title: Characterization, comparison and application of two types of atmospheric pressure cold Ar plasma jets
Other Titles: 2種類の大気圧低温アルゴンプラズマジェットの特性、比較および応用に関する研究
Authors: 費, 小猛
Fei, Xiaomeng
ヒ, ショウモウ
Keywords: 大気圧低温アルゴンプラズマジェット
Atomospheric pressure cold Ar plasma jets
Issue Date: 23-Mar-2011
Publisher: 群馬大学工学部
Abstract: By DBDs or RF discharges, a variety of atmospheric pressure cold plasma jets have been developed. A RF capacitive atmospheric pressure cold plasma device was developed by Cresur Corporation of Japan. This plasma device has been commercialized under the name of “APC”. Using APC, a cold Ar plasma jet is able to be generated at atmospheric pressure. On the other hand, we have successfully developed a device that is able to generate a non-equilibrium atmospheric pressure Ar plasma jet of low temperature (22 to 35°C) using surface discharge fed by a high-voltage pulsed power source. This device has been commercialized under the name of “CAPPLAT” by Cresur Corporation of Japan. Though a variety of applications are being implemented, the electrical and the optical properties of these two atmospheric pressure cold Ar plasma jets have never been studied systematically. In chapter 2, electrical properties of APC Ar plasma jet were characterized using a high-voltage probe and a current probe. According to the observed waveforms of discharge voltage and RF current, the discharge behavior was confirmed. In particular, the effects of additive gas (N2 or O2) on the electrical properties of APC Ar plasma jet were investigated in detail. It was found that APC Ar plasma jet is a stable abnormal glow discharge (the RF α-mode discharge), and this discharge behavior scarcely changed with the addition of additive gas (N2 or O2). Further, optical emission spectrometry (OES) was employed to identify the active species in APC Ar plasma jet. OES revealed that Ar active species belonging to the excited Ar atoms (4p-4s transition) are predominant in this plasma jet (in the wavelength range of 690–950 nm). Peaks belonging to the N2 second positive system (N2 (C3∏u — B3∏g)) were also observed. However, peaks belonging to the N2 first negative system ((N2+ (B2Σ+u — X2Σ+g)) (E ≈ 18.7 eV) were not detected. Additionally, an O atom peak was detected at 777 nm. Both the nitrogen and oxygen active species were detected in the pure Ar discharge because the impurities (N2 and O2) from the atmosphere were entrained into the plasma. Based on the electrical and optical characterizations, the chemical reactions of active species in APC Ar plasma jet were proposed. In particular, we investigated the effect of additive gas (N2 or O2) on the OES of APC Ar plasma jet. It was shown that the emission intensity of O atoms increased significantly when trace of O2 gas was added. However, the emission intensities of N2 (C3∏u — B3∏g) increased only slightly when the same amount of N2 gas was added. We assumed that the generated N2 (C3∏u) quickly transformed to N2+ (B2Σ+u) through the successive collisions with energetic electrons, and then the newly created N2+ (B2Σ+u) was trapped in the discharge region by a high frequency polarity change. In chapter 3, electrical properties of CAPPLAT Ar plasma jet were characterized using a high-voltage probe and a current probe. Further, optical emission spectrometry (OES) was employed to identify the active species in CAPPLAT Ar plasma jet. In particular, the effects of additive gas (N2 or O2) on the electrical and optical characteristics of CAPPLAT Ar plasma jet were investigated in detail. According to the electrical characterization, it was found that CAPPLAT Ar plasma jet was a glow-like (diffuse barrier mode) discharge; and this discharge behavior scarcely changed with the injection of the additive gas either directly into the Ar stream or into the plasma afterglow zone through a glass capillary. On the basis of this observation, a simple discharge mechanism was proposed. According to this mechanism, in the first step, Ar molecules are excited and ionized through collisions with energetic electrons. In this step, energy is transferred to the Ar particles, and Ar metastable atoms are generated. In the second step, Ar metastable atoms, the main energy carrier, are used to generate N2 (C3∏u) and O atoms through collisions with N2 or O2 molecules. On the other hand, OES characterization revealed that Ar active species belonging to the excited Ar atoms (4p-4s transition) are predominant in CAPPLAT Ar plasma jet (in the wavelength range of 690–950 nm). Peaks belonging to the N2 second positive system (N2 (C3∏u — B3∏g)) were also observed. N2 (C3∏u — B3∏g) (E ≈ 11.1 eV) were generated through a resonant reaction between Ar metastables (E ≈ 11.5 eV) and ground-state molecular N2. Additionally, an O atom peak was detected at 777 nm, with rather weak emission intensity. A small quantity of O atoms was generated through collisions between the excited Ar atoms and molecular O2. CAPPLAT plasma jet was strongly modified when N2 gas was injected directly into the Ar stream. In this case, Ar metastables were highly quenched; and N2 (C3∏u) became the main energy carrier. This resulted in a marked decrease in the emission intensities of excited Ar atoms and excited O atoms. When O2 gas was added to the plasma afterglow zone through a glass capillary, no significant quenching effect was observed, since electrons and ions are not present in the afterglow zone. In this case, the emission intensities of excited Ar atoms decreased only slightly. Interestingly, the emission intensity of excited O atoms decreased with the increasing concentration of added O2. We presumed that the newly generated O atoms were quickly transformed to O3 through combination with the added O2 molecules. In chapter 4, both the physical and the chemical characteristics of APC Ar plasma jet and CAPPLAT Ar plasma jet were compared. The electrical characteristics showed that the discharges of APC plasma jet and CAPPLAT plasma jet are glow (glow-like) discharges, which is very meaningful for the application of homogenous plasma treatment with lower costs since the complicated vacuum system and expensive He gas are unnecessary. Additionally, it was shown that jet temperatures of these two Ar plasma jets are relatively low, which is very attractive for the treatment of thermal sensitive materials. OES characterization revealed that categories of the active species in APC plasma jet and CAPPLAT plasma jet are identical but the emission intensities of active species are quite different from each other. It was because the reaction mechanisms of active species in the two Ar plasma jets are different from each other. In CAPPLAT plasma jet, firstly energy is transferred to the Ar particles through collisions with energetic electrons; and then Ar metastables are generated. Second, Ar metastables, the main energy carrier, are used to generate nitrogen and oxygen active species through collisions with N2 or O2 molecules. However, in APC plasma jet, the direct collisions between N2 or O2 molecules with energetic electrons play an important role in the generation of nitrogen and oxygen active species. To demonstrate an application of these two Ar plasma jets, high-density polyethylene (HDPE) surface treatment was performed using CAPPLAT Ar plasma jet and APC Ar plasma jet. In particular, the effects of additive gas (N2 or O2) on the HDPE surface treatment were investigated and compared in detail. It was concluded that the effective total emission intensity and the treatment temperature are two very important factors for HDPE surface treatment. Stronger effective total emission intensity suggests more effective energetic active species in the plasma, which results in the generation of more polar functional groups on HDPE surface. On the other hand, the molecular motion on polymer surface is not negligible when the treatment temperature is relatively high. Especially, when the treatment temperature is close to the melt point of the polymer, a lot of generated functional groups diffuse into the bulk of the polymer during the plasma treatment.
Description: 学位記番号:工博甲411
URI: http://hdl.handle.net/10087/6247
Academic Degrees and number: 12301甲第411号
Degree-granting date: 2011-03-23
Degree name: 博士(工学)
Degree-granting institutions: 群馬大学
Appears in Collections:学位論文

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