On phenomena in ionized gases
vapour deposition in open-air system
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vapour deposition in open-air system
H. Yagi P 1* P , S. Yudate U 2 , H. Motomura P 2 P , M. Jinno P 2
P
Department of Industrial Innovation, Faculty of Collaborative Regional Innovation, Ehime University, P
Department of Electrical and Electronic Engineering, Faculty of Engineering, Ehime University, 3 Bunkyo, Matsuyama, 7908577, Japan (*)
yagi@dpc.ehime-u.ac.jp
a downstream flowing mixture of hydrogen and methane. The plasma torch having the shielding gas flow was employed to eliminate the effect from the atmospheric gas such as nitrogen and oxygen. The carbon films were deposited in the methane concentration about 10% (CH 4 /H 2 ). The films have DLC properties from the Raman spectra. The intensity ratio of bonding energy sp 2 /(sp 2 +sp
3 ) was 0.7. The films were smooth, flat and hard.
In recent days, plasma phenomena and its process under atmospheric pressure have been widely researched. The plasma process under atmospheric pressure will be high in deposition/etching rate in spite of its controllability of plasma. If the process under atmospheric pressure realizes in “the open-air”, the processing system becomes simple and the controllability of substrates such as the processing area and the handling of substrates, and also the processing rate becomes high in proportion to the pressure. But there are not enough data about the films deposited in the open-air condition. We researched about the influences of the atmospheric gas and the atmospheric pressure as the high pressure CVD process to the deposited films.
Experimental setup employed in this study is schematically shown in fig.1. Microwave power is supplied by a semiconductor generator at 2.45 GHz. The microwave is guided to the co-axial waveguide by a rectangular-to-coaxial line transition. The process gase mixed with hydrogen and methane were supplied through the gap between outer electrode and inner electrode to the end of nozzle. The plasma is torched between the end of inner electrode and the substrate caused by the high electric field between them. The shield gas of helium was supplied to separate between the plasma and the atmosphere.
Experimental conditions employed in the present study were as follows. The flow rate of CH 4 , H 2 and He were 15 sccm, 150 sccm and 165 sccm, respectively. The incident power is 50 W, and the processing time was 10 min. The silicon and stainless steel substrates were used for the deposition, and the gap between the nozzle and the substrate was 1.0 mm.
Fig.2 shows the Cls X-ray Photoelectron Spectrum
of the film deposited on the stainless steel (JIS:SUS304). The intensity ratio of bonding energy sp 2
2 +sp
3 ) is about 0.7. The profile corresponding to C=O bond is found in the figure.
14 Fig.2 The Cls XPS of the film deposited on the stainless steel.
143 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Ignition behaviour of atmospheric-pressure dielectric barrier discharges in argon with admixtures of hexamethyldisiloxane and tetramethylsilane
M. M. Becker 1 , J. Philipp 2 , A. K. Czerny 2 , C.-P. Klages 2 , and D. Loffhagen 1
1
2
The impact of small admixtures of the precursors hexamethyldisiloxane and tetramethylsilane on the ignition behaviour of dielectric barrier discharges in argon at atmospheric pressure has been analysed by means of a time-dependent, spatially one-dimensional fluid model and measurements. A drop of the ignition voltage by about 60
% is found when adding up to 200 ppm of precursor gas to argon. Very good agreement between measured data and modelling results is obtained when assuming that 30
% of the collisions between excited argon atoms and precursor gas lead to Penning ionization.
Dielectric barrier discharges (DBD) represent the main approach for plasma-enhanced chemical vapour deposition (PECVD) processes and facilitate the scale-up for industrial processing. Silicon-organic coatings can be achieved by mixing precursors like hexamethyldisiloxane (HMDSO) or tetramethyl- silane (TMS) to the carrier gas used by the DBD [1]. A detailed understanding of the impact of the precursor admixtures on the discharge properties like ignition voltage and energy consumption is highly important for DBD-based PECVD processing. Here, a fluid modelling approach is combined with measurements to analyse the impact of small admixtures of HMDSO and TMS to argon on the ignition behaviour of the DBD. The investigations were performed by means of the time-dependent, spatially one-dimensional fluid- Poisson model for argon DBD reported in [2], which was extended by an appropriate reaction kinetics for HMDSO and TMS, respectively. The numerical studies are based on the experimental conditions described in [1]. A symmetric plane-parallel electrode configuration was used with a thickness of the dielectrics of 2 mm and a gap width of 1 mm. The discharge is driven by a sinusoidal voltage supply at 86.2 kHz. The ignition voltage was determined by a stepwise increase of the applied voltage until the discharge was ignited and covered the entire electrode area of 8 cm 2 .
Results of the ignition voltage in dependence on the precursor concentration x are shown in figure 1. It has been found experimentally that the ignition voltage U i of the considered argon DBD decreases by about 60
% with the admixture of HMDSO and TMS, respectively, in the range from 0 to 200
ppm. The modelling-based analysis of the ionization budget shows that the impact of Penning ionization processes mainly causes the observed decrease of U i . Very good agreement between measurements and numerical results was obtained using rate coefficients for the collisions of precursor gas with excited argon atoms based on the works of Jauberteau et al. [3,
4] and a fraction of 30
% of these collision processes leading to Penning ionization.
Figure 1: Ignition voltage in atmospheric-pressure argon DBD with admixtures of HMDSO (a) and TMS (b). Acknowledgment The work was supported by the German Research Foundation under grants LO 623/3-1 and KL 1096/23-1 as well as in the framework of the Collaborative Research Centre Transregio 24 “Fundamentals of Complex Plasmas”. References [1] J. Philipp et al., Plasma Process. Polym. 13 (2016) 509–520. [2] M. M. Becker et al., J. Phys. D: Appl. Phys. 46 (2013) 355203. [3] J. L. Jauberteau et al., J. Phys. Chem. A 116 (2012) 8840−8850. [4] J. L. Jauberteau et al., Chem. Phys. Lett. 327 (2000) 351–358. Topic number 10 144
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal Water treatment using micro-bubble assisted three dimensionally integrated micro solution plasma Y. Ishida P ,
H. Masunaga P , T. Shirafuji P Department of Physical Electronics and Informatics, Osaka City University, Osaka, Japan We have performed water treatment for decomposing organic contaminants in water using micro- bubble assisted three-dimensionally integrated micro solution plasma (3D IMSP). The original 3D IMSP reactor without micro-bubble assistance cannot generate plasma when water to be treated has electrical conductivity of 200 μS/cm or higher. The novel micro-bubble assisted 3D IMSP reactor, on the other hand, can generate plasma in the water with electrical conductivity up to 500 μS/cm. Ignition and sustain voltages for plasma are also reduced. These results indicate that micro- bubble assistance brings about low-power consumption and extension of application area in water treatment by 3D IMSP.
Plasma in liquid has attracted much attention because of their possible applications for solving water-related environmental issues. We have previously proposed a novel three-dimensionally integrated micro solution plasma (3D IMSP) reactor, which can generate a large amount of microplasmas in a porous dielectric material filled with a gas/liquid mixed medium [1]. However, 3D IMSP is not effective for the treatment of an aqueous solution with a high electrical conductivity [2], which was one of disadvantages of 3D IMSP. In this work, we have introduced micro bubbles into the 3D IMSP reactor in order to treat water with higher electrical conductivity.
We employed micro-bubble generator (Hack UFB, FB11) as a substitute of the liquid circulation pump used in our previous 3D IMSP reactor [1]. The aqueous solutions used for this experiment had electrical conductivities of 1, 10, 100, 200, 500, and 1000 μ
with deionized water. 3. Results and discussion Figure 1 shows effects of micro-bubble assistance on the operation of 3D IMSP. We can confirm that the micro-bubble assisted 3D IMSP reactor can generate plasma in the aqueous solution with electrical conductivity up to 500 μ S/cm, while conventional 3D IMSP reactor cannot. Furthermore, micro-bubble assistance has an effect of reducing the ignition and sustain voltages of 3D IMSP as shown in Fig. 2, which means that we can suppress energy consumption for the water treatment by micro- bubble assisted 3D IMSP. Acknowledgement This work was partly supported by JSPS MEXT KAKENHI Grant Numbers 15H03585 and 15K13391. References [1] T. Shirafuji and Y. Himeno, Jpn. J. Appl. Phys. 52, 11NE03 (2013). [2] T. Shirafuji, J. Ueda, A. Nakamura, S. -P. Cho, N. Saito, and O. Takai, Jpn. J. Appl. Phys. 52, 126202 (2013). 17 Fig. 2 Effects of micro-bubble assistance on the ignition and sustain voltages of 3D IMSP. 6 5 4 3 2 Ig n it io n an d su st a in vo lt a g e s (k V ) 600 500 400 300 200 100 0 Electrical conductivity (uS/cm) without micro bubbles Ignition Sustain with micro bubbles Ignition Sustain Plasma is generated only with bubble assistance Maximum voltage of the power source Fig. 1 Effects of micro-bubble assistance on the operation of 3D IMSP.
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XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal Solution-plasma synthesis of a gold-nanoparticle-containing polymer membrane on aqueous solution Y. Nakamura 1 , S. Azuma 1 , T. Isshiki 2 , T. Shirafuji 1 1 Department of Physical Electronics and Informatics, Osaka City University, Osaka, Japan 2 Department of Electronics and Systems, Kyoto Institute of Technology, Kyoto, Japan We have generated dielectric barrier discharge (DBD) of argon gas on HAuCl 4 aqueous solution for synthesizing gold nanoparticles. If we add gelatine to HAuCl 4 aqueous solution, we obtain a wine-red coloured membrane on the aqueous solution by the DBD. The membrane has fibrous structure composed of polymerized gelatine, which has been confirmed through optical microscope observation and infrared absorption spectroscopy of the membrane. In addition, we have confirmed that dispersed gold nanoparticles are incorporated in the membrane, which has been confirmed through energy dispersive X-ray spectroscopy of the membrane and transmission electron microscope observation of the edge of the membrane. Gold nanoparticles in the membrane are dense and have fairly uniform size distribution depending on the position in the membrane.
Solution plasma can be used for various applications including nanoparticle synthesis and liquid treatment [1]. However, there are few reports on thin film formation using solution plasma [2]. In this work, we report that we can synthesize a free-standing and gold-nanoparticle-containing gelatine membrane by using dielectric barrier discharge (DBD) on aqueous solution.
The aqueous solution was HAuCl 4 (0.3 mM) aqueous solution with gelatine. Gas gap was 2 mm. Applied voltage was bipolar pulse voltage (amplitude 4 kV, frequency 40 kHz, pulse width 4 μs). Typical discharge time was 10 min. Discharge gas was argon. 3. Results and discussion A wine-red coloured membrane is formed on the surface of aqueous solution in contact with DBD as shown in Fig. 1. Infrared absorption spectra of the membrane and energy dispersive X-ray spectra have indicated that the membrane is made of polymerized gelatine and gold. Figure 2 shows a transmission electron microscope (TEM) image of the sample taken from the outer edge of the membrane, which indicates that gold nanoparticles are formed in the membrane, and that they are dense and have uniform size distribution. Such size regulation may be explained in terms of immediate capture of reduced gold near the outermost edge of the laterally growing membrane. This method may be useful for preparing size-regulated nanomaterials because the particle size may be controlled by adjusting rates of reduction and membrane growth. Acknowledgements This work was partly supported by JSPS MEXT KAKENHI Grant Numbers 15H03585 and 15K13391. References [1] T. Shirafuji, J. Ueda, A. Nakamura, S.-P. Cho, N. Saito, and O. Takai, Jpn. J. Appl. Phys. 52, 126202 (2013). [2] H. Furusho, D. Miyamoto, Y. Nagasaki, K. Kitano, and S. Hamaguchi, J. Photopolym. Sci. Technol. 20, 229 (2007). Fig. 2 A TEM image of the edge of the membrane. 100 nm 14 Fig. 1 The membrane formed on the HAuCl 4 /gelatine aqueous solution by Ar DBD exposure.
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XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal Time- and space-resolved optical emission spectroscopy on dielectric barrier discharge of helium gas in contact with water S. Kito
PP , K. Obana, U T. Shirafuji UPPP Deparment of Physical Electronics and Informatics, Osaka City University, Osaka, Japan P We have performed time- and space-resolved optical emission spectroscopy on a dielectric barrier discharge of helium gas in a system consisting of a top metal syringe on a water surface. We have observed streamer propagation from positive to negative electrodes for both polarities of applied pulse voltages. After the streamer reaches the counter electrode, the discharge area has shown glow-like structure, which is composed of a positive column, a Faraday dark, and a negative glow, for both polarities. However, the negative glow formed on the water shows weaker emission intensity than the positive column, as opposed to the fact that a negative glow should show higher emission intensity than a positive column in the case of conventional glow-discharges in contact with a solid electrode. This can be attributed to electron attachment by dense water vapor on the water surface.
Plasma in contact with liquid has attracted much attention because of its various potential applications [1]. However, characteristics of plasma in contact with liquid have not yet fully understood. Shirai and others have revealed static structure in a DC discharge on water [2]. In this paper, we report time evolution of structure in a DBD on water, which is observed by using time- and space-resolved optical emission spectroscopy (OES). 2. Experimental Setup We applied time- and space-resolved OES on a DBD of helium gas on a water surface. The top electrode was a metal syringe to feed helium gas, and the bottom electrode was a planar surface of deionized water in a glass petri dish. The gas gap between them was 3 mm. Applied voltage was bipolar pulsed voltage (amplitude 1.2 kV, frequency 10 kHz, pulse width 4 μs).
Figures 1(a) and 1(b) show the time- and space-resolved OES profiles for helium (587 nm) when positive and negative pulses are applied on the top electrode, respectively, in which a streamer propagates from the positive electrode to negative one. After the streamer reaches the counter electrode, the discharge area exhibits a glow-discharge-like structure composed of a positive column, Faraday dark, and negative glow. These are common features for both positive and negative polarity. However, the negative glow formed on the water surface shown in Fig. 1(a) has weaker emission intensity than the positive column as opposed to a conventional discharge on a metal electrode. This can be attributed to electron attachment by dense water vapor near the water surface.
This work was partly supported by JSPS MEXT KAKENHI Grant Numbers 15H03585 and 15K13391. References [1] P. Bruggeman and C. Leys, J. Phys. D 42, 053001 (2009). [2] N. Shirai, M. Nakazawa, S. Ibuka, and S. Ishii, Jpn. J. Appl. Phys. 48, 036002 (2009). 3 Fig. 1 Time- and space resolved OES profiles on a He plasma jet on water. 0 ns 20 ns 40 ns 60 ns 80 ns 100 ns 120 ns 140 ns 160 ns 180 ns (a) positive phase (b) negative phase nozzle nozzle water water 3 m m 3 m m 147
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Diagnostics on aluminium dust explosion ignited by spark discharge
M. Sankhe P 1 P , U S. Bernard UP 2 P , S. Pellerin P 1 P , P. Gillard 2 , M. Wartel P 1 P
P 1 P
d’Orléans, France P
P
Several companies are using flammable dusts in their manufacturing process and are sometimes faced with the risk of explosion that can cause tremendous catastrophe with human and material damage. Dust explosions can have many ignition sources but static electricity represents the largest cause of ignition. In this context we use spark discharge to ignite dust explosions for studying conditions and characteristics of dust explosions in order to prevent them.
The main goal of this work is to provide ignition experimental data usable for combustion modelling such as the minimum ignition energy (MIE), the burning temperature, the ignition delay, the variation of electron density and the spark temperature.
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