Synthesis of Silicon Nanoparticles and Nanowires by a Nontransferred Arc Plasma System

Choi, Sooseok,Lee, Hyunjun,Park, Dong-Wha Hindawi Limited 2016 Journal of nanomaterials Vol.2016 No.-

<P>Silicon nanomaterials were synthesized from solid silicon powder in microsize using a nontransferred arc plasma system. Synthesized silicon nanomaterials were sphere or wire in morphology according to the input power of arc plasma, the flow rate of plasma forming gas, and the collecting position of product. The product was spherical nanoparticles at a high input power for complete evaporation, while it was nanowires at a relatively low input power. The mean diameter of synthesized silicon nanoparticles was increased from 20.52 nm to 40.01 nm by increasing the input power from 9 kW to 13 kW. On the other hand, the diameter of silicon nanowires was controllable by changing the flow rate of plasma forming gas. The mean diameter of silicon nanowires was increased from 16.69 nm to 23.03 nm by decreasing the plasma forming gas flow rate from 15 L/min to 12 L/min.</P>

Numerical analysis on a thermal plasma reactor for HFC-23 treatment

Choi, Sooseok,Cho, Kyu Young,Woo, Joo Man,Lim, Jong Choo,Lee, Joong Kee Elsevier 2011 Current Applied Physics Vol.11 No.5

<P><B>Abstract</B></P><P>It was simulated that thermal flow characteristics inside a thermal plasma reactor for an abatement ofHFC-23 (trifluoromethane, CHF<SUB>3</SUB>) which is a kind of greenhouse gas. Effects of arc current and length of reaction tubes on the decomposition process were numerically analyzed to find out a suitable plasma torch operating condition and an optimal reactor design. Numerical results were in good agreements with experimental results on measured temperature at reactor exit and a damaged appearance of the inner reaction tube after the practical decomposition process. A sufficiently large area and high temperature over 1500 K for HFC-23 decomposition was predicted in the torch operation with an arc current of 50 A. In this condition, a high decomposition rate over 99.5%was achieved in spite of a short residence time estimated around 50 ms. And it was revealed that not only the length of the inner reaction tube which is continuously contact with high heat flux from the thermal plasma jet but also the outer tube length is important for a durable operation of the reactor system.</P> <P><B>Highlights</B></P><P>► Thermal plasma reactor for HFC-23 treatment was precisely simulated. ► Two tubes are placed in the reactor to provide high temperature environment over 1500 K and to introduce waste and reactive gases, respectively. ► Melting issue arose in inner reaction tube which is directly contact with thermal plasma jet, was solved by optimizing the length of outer tube with high treatment efficiency over 99.5%.</P>

THERMAL PLASMA DECOMPOSITION OF FLUORINATED GREENHOUSE GASES

SOOSEOK CHOI,Dong Wha Park,TAKAYUKI WATANABE,박동화 한국원자력학회 2012 Nuclear Engineering and Technology Vol.44 No.1

Fluorinated compounds mainly used in the semiconductor industry are potent greenhouse gases. Recently, thermal plasma gas scrubbers have been gradually replacing conventional burn-wet type gas scrubbers which are based on the combustion of fossil fuels because high conversion efficiency and control of byproduct generation are achievable in chemically reactive high temperature thermal plasma. Chemical equilibrium composition at high temperature and numerical analysis on a complex thermal flow in the thermal plasma decomposition system are used to predict the process of thermal decomposition of fluorinated gas. In order to increase economic feasibility of the thermal plasma decomposition process, increase of thermal efficiency of the plasma torch and enhancement of gas mixing between the thermal plasma jet and waste gas are discussed. In addition,noble thermal plasma systems to be applied in the thermal plasma gas treatment are introduced in the present paper.

나노물질 합성과 폐기물 처리를 위한 열플라즈마 기술

최수석 ( Sooseok Choi ) 한국공업화학회 2022 공업화학전망 Vol.25 No.1

열플라즈마는 수천 도에서 만 도 이상에 이르는 높은 온도를 바탕으로 나노물질의 합성과 폐기물의 고도처리와 같은 분야에 이용되고 있다. 열플라즈마를 발생시키는 장치인 플라즈마 토치는 전기에너지를 이용하여 출력의 제어가 자유롭고 다양한 방전기체를 적용할 수 있기 때문에, 전통적인 방법으로는 어려운 새로운 산업공정에 적용할 수 있다. 통상 열플라즈마를 이용하여 원료물질을 완전 기화시킨 다음 응축하여 합성된 나노물질의 크기는 수 nm에서 100 nm 내외의 크기를 가지며, 냉각과정의 제어를 통해 결정성 및 크기의 제어가 가능하다. 열플라즈마를 이용한 폐기물 공정은 기본적으로 재래식 연소에 비해 높은 온도에서 이루어지므로 다이옥신과 같은 유해 물질의 제어가 가능하며, 과불화탄소와 같은 난분해성 온실기체를 높은 파괴율로 처리하기에도 유리하다. 전통적으로 열플라즈마는 용접과 절단, 세라믹 물질을 사용한 열장벽 코팅, 제철 및 제련과 같은 분야에 널리 사용되어 왔다. 최근 열플라즈마를 이용한 기능성 나노물질의 합성과 난분해성 온실기체의 분해 및 메탄변환을 통한 수소생산 등에 활용하고자 하는 연구가 주를 이루고 있다.

Numerical Simulation of Thermal Plasma Gasification Process

Trans Tech Publications 2015 Applied Mechanics and Materials Vol. No.

<P>Numerical analysis of plasma gasification process was carried out base on the combination of magnetohydrodynamics (MHD) and computational fluid dynamics (CFD). A two stage gasification system which consists of a heater and a plasma rector was used to enhance syngas production in the present work. Nitrogen thermal plasma jet generated by a low power plasma torch was analyzed by a self-developed MHD code, and complex thermal flow field in the plasma reactor was simulated with a commercial CFD code. The accuracy of numerical simulation was confirmed from the comparison between numerical results and experimentally measured data of arc voltage and reactor temperature. From the numerical analysis, a high temperature for the thermal cracking of methane was expected in the upper region of the plasma reactor.</P>

Investigation of the relationship between arc-anode attachment mode and anode temperature for nickel nanoparticle production by a DC arc discharge

Liang, Feng,Tanaka, Manabu,Choi, Sooseok,Watanabe, Takayuki Institute of Physics Publishing Ltd. 2016 Journal of Physics. D, Applied Physics Vol.49 No.12

<P>Multiple and constricted arc-anode attachment modes were observed in helium arc discharge to prepare nickel nanoparticles. The electron overheating instability resulted in the formation of multiple attachment modes. The effects of hydrogen concentration and shield gas flow rate on the characteristics of nickel nanoparticles were investigated. The evaporation rate of anode material contributed to forming different arc-anode attachments. The surface temperature of the electrode was measured during the arc discharge by two-color pyrometry combined with a high-speed camera which employs appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature behavior of the anode surface was investigated by using two synchronized high-speed cameras. The waveform of anode jet area variation with time follows that of the highest temperature variation of anode surface with time. The fluctuation of the highest anode temperature increased when the arc anode attachment changed from multiple into constricted mode. The highest temperature fluctuation and stability of the arc contributed to nanoparticle size distribution. Nickel nanoparticles with large productivity and narrow size distribution were obtained when shield gas was employed by controlling the residence time of nanoparticle growth. The formation mechanism of different arc-anode attachment modes was explained.</P>

Formation of different arc-anode attachment modes and their effect on temperature fluctuation for carbon nanomaterial production in DC arc discharge

Liang, Feng,Tanaka, Manabu,Choi, Sooseok,Watanabe, Takayuki Elsevier 2017 Carbon Vol.117 No.-

<P>Diffuse and multiple arc-anode attachment modes were observed when using DC arc discharge to prepare carbon nanomaterials. The effects of arc current and electrode gap distance on the formation of different attachment modes were investigated. The formation of different attachment modes is explained by the competition of the cathode jet and the anode jet. During the arc discharge, the surface temperature of the carbon electrode was measured by two-colour pyrometry combined with a high-speed camera employing appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature fluctuation of the electrode surface was investigated. Due to the unbalanced Lorenz force, the rotation of arc spot was severe in diffuse arc-anode attachment mode, which led to relatively large temperature fluctuations on the anode surface, resulting in low purity of synthesised multi-wall carbon nanotubes on the anode deposit. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Decomposition of Nitrogen Trifluoride Using Low Power Arc Plasma

Ko, Jee-Hun,Choi, Sooseok,Park, Hyun-Woo,Park, Dong-Wha Institute of Plasma Physics, the Chinese Academy o 2013 Plasma science & technology Vol.15 No.9

<P>The low power arc plasma is characterized by extremely high enthalpy and temperature and it is easy to generate and control, and thus thermal decomposition process based on the plasma torch is receiving a great attention for decomposing non-degradable greenhouse gases. In order to elevate the economic feasibility, the effects of input power, waste gas flow rate and additive gases on the destruction and removal efficiency (DRE) of NF<SUB>3</SUB> are examined. Specific energy density (SED) deceases as the flow rate increases, and accordingly, the DRE is reduced. The DRE is basically determined by the specific energy density. The highest DRE of NF<SUB>3</SUB> was 97% for the waste gas flow rate of 100 L/min at a low input power level of 2 kW with the help of hydrogen additional gas. The inlet and outlet concentration of NF<SUB>3</SUB> was analyzed using Fourier transform infrared spectroscopy (FT-IR) for DRE of NF<SUB>3</SUB> evaluation. As a result, large amount of NF<SUB>3</SUB> can be efficiently decomposed by low power arc plasma systems.</P>

A qualitative evaluation method for engine and its operating-envelopeusing GSP

Kyuhyung KYUNG,Yongmin JUN,Sooseok YANG,Dongwhan CHOI 한국추진공학회 2004 한국추진공학회 학술대회논문집 Vol.2004 No.5

Measurement of Electron Temperature and Number Density and Their Effects on Reactive Species Formation in a DC Underwater Capillary Discharge

Ahmed, Muhammad Waqar,Rahman, Md. Shahinur,Choi, Sooseok,Shaislamov, Ulugbek,Yang, Jong-Keun,Suresh, Rai,Lee, Heon-Ju The Korean Vacuum Society 2017 Applied Science and Convergence Technology Vol.26 No.5

The scope of this work is to determine and compare the effect of electron temperature ($T_e$) and number density ($N_e$) on the yield rate and concentration of reactive chemical species ($^{\bullet}OH$, $H_2O_2$ and $O_3$) in an argon, air and oxygen injected negative DC (0-4 kV) capillary discharge with water flow(0.1 L/min). The discharge was created between tungsten pin-to pin electrodes (${\Phi}=0.5mm$) separated by a variable distance (1-2 mm) in a quartz capillary tube (2 mm inner diameter, 4 mm outer diameter), with various gas injection rates (100-800 sccm). Optical emission spectroscopy (OES) of the hydrogen Balmer lines was carried out to investigate the line shapes and intensities as functions of the discharge parameters such as the type of gas, gas injection rate and inter electrode gap distances. The intensity ratio method was used to calculate $T_e$ and Stark broadening of Balmer ${\beta}$ lines was adopted to determine $N_e$. The effects of $T_e$ and $N_e$ on the reactive chemical species formation were evaluated and presented. The enhancement in yield rate of reactive chemical species was revealed at the higher electron temperature, higher gas injection rates, higher discharge power and larger inter-electrode gap. The discharge with oxygen injection was the most effective one for increasing the reactive chemical species concentration. The formation of reactive chemical species was shown more directly related to $T_e$ than $N_e$ in a flowing water gas injected negative DC capillary discharge.