This study investigated the degradation characteristics and biodegradability of phenol, refractory organic matters, by injecting MgO and CaO-known to be catalyst materials for the ozonation process-into a Dielectric Barrier Discharge (DBD) plasma. MgO and CaO were injected at 0, 0.5, 1.0, and 2 g/L, and the pH was not adjusted separately to examine the optimal injection amounts of MgO and CaO. When MgO and CaO were injected, the phenol decomposition rate was increased, and the reaction time was found to decrease by 2.1 to 2.6 times. In addition, during CaO injection, intermediate products combined with Ca2+ to cause precipitation, which increased the COD (chemical oxygen demand) removal rate by approximately 2.4 times. The biodegradability of plasma treated water increased with increase in the phenol decomposition rate and increased as the amount of the generated intermediate products increased. The biodegradability was the highest in the plasma reaction with MgO injection as compared to when the DBD plasma pH was adjusted. Thus, it was found that a DBD plasma can degrade non-biodegradable phenols and increase biodegradability.

본 연구는 저온살균(60oC, 5-20분)과 대기압플라즈마(5- 20분)를 병용한 고춧가루 중의 E. coli 저감화 및 시너지 효과를 조사하였다. 저온살균 단일처리시 대장균의 불활 성화는 최대 2 log10 CFU/g(=99% 감소) 이상 나타내었으며, 대기압플라즈마 5, 10, 15, 및 20분간 단일처리 하였을 때 각각 0.4, 0.8, 0.9 및 1.4 log10 CFU/g 감소되었다. 저온 살균 및 대기압플라즈마 단독 처리만으로는 만족할 만한 미생물 저감화효과를 얻을 수 없었기에 저온살균 처리 후, 대기압플라즈마를 병용처리 하여 대장균의 불활성화는 1- 6 log10 CFU/g 이상 감소되었다. 그러나, 저온살균과 대기 압플라즈마 병용처리에 따른 관능적 품질 (색, 이취, 맛, 조 직감 및 전체적인 기호도)에 대한 유의적인 차이는 관찰 되지 않았다(P>0.05). 따라서 고춧가루의 미생물학적 안전성 확보를 위해 저온살균과 대기압플라즈마 단독처리보다 이 둘의 병용처리가 E. coli의 확실한 저감화 효과를 유도 하고 식품 고유의 품질특성을 유지하는데 효과적이었음을 본 연구를 통해 확인되었다.

Recently, the amount of heat generated in devices has been increasing due to the miniaturization and high performance of electronic devices. Cu-graphite composites are emerging as a heat sink material, but its capability is limited due to the weak interface bonding between the two materials. To overcome these problems, Cu nanoparticles were deposited on a graphite flake surface by electroless plating to increase the interfacial bonds between Cu and graphite, and then composite materials were consolidated by spark plasma sintering. The Cu content was varied from 20 wt.% to 60 wt.% to investigate the effect of the graphite fraction and microstructure on thermal conductivity of the Cu-graphite composites. The highest thermal conductivity of 692 W m−1K−1 was achieved for the composite with 40 wt.% Cu. The measured coefficients of thermal expansion of the composites ranged from 5.36 × 10−6 to 3.06 × 10−6 K−1. We anticipate that the Cu-graphite composites have remarkable potential for heat dissipation applications in energy storage and electronics owing to their high thermal conductivity and low thermal expansion coefficient.

본 연구는 수산양식분야에서 용수를 살균하기 위해 제품화되어 있는 UV 및 플라즈마 장치를 100 ℓ 수조에 적용하고 처리수를 1 ℓ씩 채수, 농축하여 시료 내 세균 수의 변화를 확인하여 두 가지 처리 방식에 따른 효과를 비교하였다. 각 장치를 6시간 동안 작동시키면서 일반 해 수 내 세균을 MA, TCBS, SS 배지에 배양하여 세균 수 변화를 확인하였고, 살균처리된 해수 내 Edwardsiella piscicida를 인위 접종한 후 처리수 내 E. piscicida 세균 수 변화를 확인한 결과 UV 장치와 플라즈마 장치 간의 세균 저감 효율은 99.5~99.9% 수준으로 거의 유사한 수준으로 확 인되었다. 2가지 장치를 적용하여 100 ℓ의 수량을 동일한 시간 동안 처리하였을 때, 플라즈마 방식의 경우 UV 장치와 비교하여 더 짧은 시간 안에 세균을 사멸하는 것으로 나타났다. 하지 만 본 연구에서는 단기적(6시간)으로만 세균 수 변화를 확인한 것으로, 사료찌꺼기, 배설물, 연 안 오염 등에 따라 수질의 변동이 크고 biofilm과 유기물이 많이 존재하는 실제 양식환경을 고려할 때, 탁도와 유기물의 존재에 따라 한계가 있는 UV 처리 방식보다는 지속적이고 일정 한 효과를 유지할 수 있는 플라즈마 처리 방식이 보다 효율적일 것으로 사료된다.

Molybdenum is a low-resistivity transition metal that can be applied to silicon devices using Si-metal electrode structures and thin film solar cell electrodes. We investigate the deposition of metal Mo thin film by plasma-enhanced atomic layer deposition (PE-ALD). Mo(CO)6 and H2 plasma are used as precursor. H2 plasma is induced between ALD cycles for reduction of Mo(CO)6 and Mo film is deposited on Si substrate at 300℃. Through variation of PE-ALD conditions such as precursor pulse time, plasma pulse time and plasma power, we find that these conditions result in low resistivity. The resistivity is affected by Mo pulse time. We can find the reason through analyzing XPS data according to Mo pulse time. The thickness uniformity is affected by plasma power. The lowest resistivity is 176 μΩ·cm at Mo(CO)6 pulse time 3s. The thickness uniformity of metal Mo thin film deposited by PE-ALD shows a value of less than 3% below the plasma power of 200 W.

Oxide coatings are formed on die-cast AZ91D Mg alloy through an environmentally friendly plasma electrolytic oxidation(PEO) process using an electrolytic solution of NaAlO2, KOH, and KF. The effects of PEO condition with different duty cycles (10 %, 20 %, and 40 %) and frequencies(500 Hz, 1,000 Hz, and 2,000 Hz) on the crystal phase, composition, microstructure, and micro-hardness properties of the oxide coatings are investigated. The oxide coatings on die-cast AZ91D Mg alloy mainly consist of MgO and MgAl2O4 phases. The proportion of each crystalline phase depends on various electrical parameters, such as duty cycle and frequency. The surfaces of oxide coatings exhibit as craters of pancake-shaped oxide melting and solidification particles. The pore size and surface roughness of the oxide coating increase considerably with increase in the number of duty cycles, while the densification and thickness of oxide coatings increase progressively. Differences in the growth mechanism may be attributed to differences in oxide growth during PEO treatment that occur because the applied operating voltage is insufficient to reach breakdown voltage at higher frequencies. PEO treatment also results in the oxide coating having strong adhesion properties on the Mg alloy. The micro-hardness at the cross-section of oxide coatings is much higher not only compared to that on the surface but also compared to that of the conventional anodizing oxide coatings. The oxide coatings are found to improve the micro-hardness with the increase in the number of duty cycles, which suggests that various electrical parameters, such as duty cycle and frequency, are among the key factors controlling the structural and physical properties of the oxide coating.

In the present work, spheroidization of angular vanadium powders using a radio frequency (RF) thermal plasma process is investigated. Initially, angular vanadium powders are spheroidized successfully at an average particle size of 100 μm using the RF-plasma process. It is difficult to avoid oxide layer formation on the surface of vanadium powder during the RF-plasma process. Titanium/vanadium/stainless steel functionally graded materials are manufactured with vanadium as the interlayer. Vanadium intermediate layers are deposited using both angular and spheroidized vanadium powders. Then, 17-4PH stainless steel is successfully deposited on the vanadium interlayer made from the angular powder. However, on the surface of the vanadium interlayer made from the spheroidized powder, delamination of 17-4PH occurs during deposition. The main cause of this phenomenon is presumed to be the high thickness of the vanadium interlayer and the relatively high level of surface oxidation of the interlayer.

This objective of this study was to investigate the degradation characteristics of phenol, a refractory substance, by using a submerged dielectric barrier discharge (DBD) plasma reactor. To indirectly determine the concentration of active species produced in the DBD plasma, the dissolved ozone was measured. To investigate the phenol degradation characteristics, the phenol and chemical oxygen demand (COD) concentrations were evaluated based on pH and the discharge power. The dissolved ozone was measured based on the air flow rate and power discharged. The highest dissolved ozone concentration was recorded when the injected air flow rate was 5 L/min. At a discharge power of 40W as compared to 70W, the dissolved ozone was approximately 2.7 – 6.5 times higher. In regards to phenol degradation, the final degradation rate was highest at about 74.06%, when the initial pH was 10. At a discharged power of 40W, the rate of phenol decomposition was observed to be approximately 1.25 times higher compared to when the discharged power was 70W. It was established that the phenol degradation reaction was a primary reaction, and when the discharge power was 40W as opposed to 70W, the reaction rate constant(k) was approximately 1.72 times higher.

This study was carried out to investigate the effect of chlorine water and plasma gas treatment on the quality and microbial control of Latuca indica L. baby Leaf during storage. Latuca indica L. baby leaves were harvested from a plant height of 10cm. They were sterilized with 100μL·L-1 chlorine water and plasma-gas (1, 3, and 6hours), and packaged with 1,300cc·m-2·day-1·atm-1 films and then stored at 8±1?and RH 85±5% for 25days. During storage, the fresh weight loss of all treatments were less than 1.0%, and the carbon dioxide and oxygen concentrations in packages were 6-8% and 16-17%, respectively for all treatments in the final storage day. The concentration of ethylene in the packages fluctuated between 1-3μL·L-1 during the storage and the highest concentration of ethylene was observed at 6 hours plasma treatment in the final storage day. The off-odor of all treatments were almost odorless, the treatments of chlorine water and 1 hour plasma maintained the marketable visual quality until the end of storage. Chlorophyll content and Hue angle value measured at the final storage day were similar to those measured before storage in chlorine water and 1 hour of plasma treatments. E. coli was not detected immediately after sterilization in all sterilization treatments. After 6 hours of plasma treatment, the total bacteria fungus counts were lower than the domestic microbial standard for agricultural product in all sterilization treatments. The total aerobic counts in the end storage day increased compared to before storage, whereas E. coli was not detected in all sterilization treatments. The sterilization effect against bacteria and fungi was the best in chlorine water treatment. Plasma treatment showed sterilization effects, but within a prolonged period of time. In addition, the sterilization effect decreased gradually. These results suggest that chlorine water and plasma treatment were effective in maintaining Latuca indica L. baby Leaf commerciality and controlling microorganisms during postharvest storage.

The objective of this study was to investigate the quality properties of sausages added with the atmospheric pressure plasma treated extract of Perilla frutescens Britton var. acuta Kudo (red perilla). The lyophilized powder of red perilla extract treated by atmospheric-pressure plasma contained 7.5 g kg-1 nitrite. Sausage samples were manufactured with the addition of sodium nitrite (Control), celery powder (Celery), or plasma-treated extract of red perilla (PTP) to obtain nitrite concentration of 70 mg kg-1. The residual nitrite content was the lowest in PTP during storage for 21 days at 4℃ (p<0.05). The total aerobic bacteria counts were higher in PTP than in Control and Celery during storage at 4℃ (p<0.05). Malondialdehyde content of sausages was significantly lower in PTP than in Control and Celery during storage (p<0.05). PTP showed the lowest L* value and the highest b* value among the tested sausage samples during storage (p<0.05). PTP received the low scores in all the sensory properties of sausages because of its inherent color and flavor. The results suggested that the plasma-treated extract of red perilla was an unsuitable natural nitrite source for cured meat products because of its adverse effect on sensory quality. However, natural nitrite source with increased nitrite content can be produced by the treatment of the natural plant extract with atmosphericpressure plasma.

In this work, a PAM(Plasma Assisted Machining) technology was applied to milling of high manganese steel, a typical hard-to-machine materials. For this purpose, a transferred type of arc plasma torch was coupled with a 3-axis milling machine, then, used to heat and soften the surface of a high manganese steel plate in front of a 16 mm end mill with 2 blades and hard coatings. From the test results, it was concluded that the cutting load can be significantly reduced down to 57 % by plasma heating with the power level of 3.9 kW, ensuring the improvement of tool life and surface roughness in milling of high manganese work pieces.

바이오존의 대기압 플라즈마를 사용한 쥐치포(Stephanolepis cirrhifer) 중 미생물안전관리 대상인 B. cereus F4810/72 와 S. aureus ATCC 6538의 저감화 정도 및 품질 특성을 관찰하였다. 대기중의 공기를 활용하여 플라즈마 발생을 유도하여 0 분, 1 분, 3 분, 5 분, 10 분 및 20 분 처리하였다. 이후 대상 미생물의 살균력 평가를 위해 표준평판 법을 사용하여 로그 감소값을 계산하고 Color difference meter를 사용하여 Hunter “L”(명도), ”a”(적색도) 및 “b”(황색도)의 차이를 분석했다. 대기압 플라즈마 3분 처리만으로도 이 두 세균을 1 로그 감소(=90% 감소) 시킬 수 있음이 확인되었다. 아울러 최대 20 분 처리시 쥐치포의 명도, 적색도 및 황색도의 차이는 관찰되지 않았다. 그러나, 본 연구에 사용된 대기압 플라즈마의 기타 수산 건어포와 일반 식품에 대한 산업적 적용을 위해서는 추가적인 목적 미생물의 살균력 연구와 각 품질의 특성을 고려한 품질평가 및 관능평가 등의 추가적인 연구의 확대가 필요하다고 사료된다.

Effects of a commercial scale intervention system combining ultraviolet (UV)-C and plasma treatments on the microbial decontamination of black pepper powder were investigated. The process parameters include treatment time, time for plasma accumulation before treatment, and water activity of black pepper powder. A significant reduction in the number of indigenous aerobic mesophilic bacteria in black pepper powder was observed after treatments lasted for ≥ 20 min (p<0.05) and the reduction was differed by powder manufacturer. The microbial reduction rates obtained by individual UV-C treatment, individual plasma treatment, and UV-C/plasma-combined treatment were 0.2, 0.5, and 1.0 log CFU/g, respectively, suggesting that the efficacy of the microbial inactivation was enhanced by treatment combination. Nonetheless, neither plasma accumulation time nor powder water activity affected the microbial inactivation efficacy of the combined treatment. The UV-C/plasma-combined treatment, however, decreased lightness of black pepper powder, and the decrease generally increased as operation time increased. The plasma accumulation time of 20 min resulted in significant reduction in both lightness and brown color. The results indicate that the commercial-scale intervention system combining treatments of UV-C and plasma has the potential to be applied in the food industry for decontaminating black pepper powder.