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임유봉,황두섭,이준오,이정훈,김훈희,장우석 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
We have developed a high frequency (40 MHz) plasma-enhanced chemical vapor deposition (PECVD) system for large-area and high-rate deposition of hydrogenated microcrystalline silicon (μc-Si:H). The large-area and high-rate deposition is known to be the key for mass production of silicon thin film solar cells, and the high-power operation made it possible to obtain deposition rates up to 1.8 nm/s. However, it was reported that there were several drawbacks, and temperature was typically concerned by many researchers. The temperature is one of the most important factors in μc-Si:H deposition processes using PECVD for the reason that temperature is in charge of the surface reaction and the growth kinetics. Without cooling, the temperature was observed to increase considerably during deposition of a thick intrinsic layer with thickness of 2 μm. In order to operate PECVD processes with constant temperature, it is required to design an efficient temperature control system. We have developed a cooling system which is designed for a susceptor and a showerhead. Susceptor cooling is performed in a direct cooling mode where a coolant is circulated through a tube inside a susceptor, and appropriate flow rates and temperatures of the coolant were calculated. Showerhead cooling system is designed to make use of an indirect cooling mode where there is efficient thermal radiation heat exchange between a showerhead and chamber wall. The efficiency was substantially improved by anodizing surface of a showerhead. This cooling system allows stable processes of large-area μc-Si:H deposition at high power.
이태상,최원호,임유봉 한국물리학회 2004 새물리 Vol.49 No.1
Prior to optimized Hall thruster research, a prototype Hall thruster was fabricated, and a preliminary discharge experiment was conducted to study the basic principles of the Hall thruster. Using the Poisson code, we calculated the magnetic eld and optimized it by using an electromagnet and an iron core to give a large radial component of the magnetic field, which is crucial for discharge performance. With the designed eld structure, the dimension of the discharge channel was determined. Several other important design factors such as the wall material, the vacuum system requirements, the eect of the vacuum chamber size on the electric field, etc., were discussed.One-dimensional uid modeling was performed to give insights into plasma generation and ion acceleration inside the discharge channel. The fabricated prototype Hall thruster successfully showed a discharge and jet plume. 최적화된 홀 추진기에 대한 상세한 연구에 앞서서 플라즈마의 발생 및 가속원리 등의 기본적인 물리현상의 이해를 도모하기 위하여 프로토타입 홀추진기의 설계, 제작 및 방전실험을 수행하였다. 홀추진기의 설계시 고려해야 하는 여러 가지 중요한 조건들에 대해서고찰하였고, 이와 더불어 설계 시 가장 중요한 요소인 자기장 구조를 얻기 위해 전자석코일과 주철로 된 코어를 이용하여 Poisson 전산코드 계산을 통해 홀추진기에서 요구되는 반경방향의 자기장 성분을 크게 만드는 자기장 구조를 설계하였다. 이렇게 구해진 자기장 구조 하에서 일차원 유체모델링을 통해 방전통로 내부의 플라즈마 변수들을 계산하여, 일반적인 홀추진기에서 요구되는 플라즈마 구조가 설계된추진기 내에서 형성되는 것을 확인하였다. 설계된 프로토타입 장치를 제작하여 성공적인 방전과 홀 효과에 의한 플라즈마의 분사를 관찰하였다.
Curing of meat batter by indirect treatment of atmospheric pressure cold plasma
조경,이주리,임유봉,황제준,정사무엘 충남대학교 농업과학연구소 2018 Korean Journal of Agricultural Science Vol.45 No.1
Nitrite is an essential additive for cured meat product. Plasma is ionized gas and reactive nitrogen species in plasma can be infused into meat batter and subsequently generate nitrites by reaction with water molecules after plasma treatment. However, the increase of nitrite in meat batter is limited with direct treatment of atmospheric pressure cold plasma because of the increase of meat batter temperature. Therefore, this study investigated the influence of indirect treatment of atmospheric pressure cold plasma on the physicochemical properties of meat batter. Meat batter was indirectly treated with plasma at 1.5 kW for 60 min. The pH of meat batter decreased while the temperature increased with plasma treatment time. The total aerobic bacterial count of meat batter was not affected by plasma treatment. The nitrite content of meat batter was increased to 377.68 mg/kg after 60 min of plasma treatment. The residual nitrite content of cooked meat batter also increased with plasma treatment time. The CIE a* - value of cooked meat batter increased. As plasma treatment time increased, lipid oxidation tended to increase and protein oxidation significantly increased. According to these results, the indirect treatment of atmospheric pressure cold plasma can be used as a new curing method for replacing synthetic nitrite salts.