• 한국표면공학회지
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• 제42권3호
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• pp.116-121
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• 2009

The 2-step low temperature plasma processes (the combined carburizing and post-nitriding) offer the increase of both surface hardness and thickness of hardened layer and corrosion resistance than the individually processed low temperature nitriding and low temperature carburizing techniques. The 2-step low temperature plasma processes were carried out for improving both the surface hardness and corrosion resistance of AISI 316L stainless steel. The influence of gas compositions on the surface properties during nitriding step were investigated. The expanded austenite (${\gamma}_N$) was formed on all of the treated surface. The thickness of ${\gamma}_N$ and concentration of N on the surface increased with increasing both nitrogen gas and Ar gas levels in the atmosphere. The thickness of ${\gamma}_N$ increased up to about $20{\mu}m$ and the thickness of entire hardened layer was determined to be about $40{\mu}m$. The surface hardness was independent of nitrogen and Ar gas contents and reached up to about 1200 $HV_{0.1}$ which is about 5 times higher than that of untreated sample (250 $HV_{0.1}$). The corrosion resistance in 2-step low temperature plasma processed austenitic stainless steels was also much enhanced than that in the untreated austenitic stainless steels due to a high concentration of N on the surface.

• Corrosion Science and Technology
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• 제7권1호
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• pp.45-49
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• 2008

The cyclic polarisation technique was applied to determine the corrosion, primary-passivation, transpassive, and protection potential of AISI 316L stainless steels immersed in 3550-ppm NaCl solution containing sulfate in the content up to 3000 ppm. The solutions were kept constant at $27^{\circ}C$ and saturated by laboratory air. The solution pH was varied from 3 to 11. Each type of potentials was plotted in function of pH and linked as lines to determine the different zones in the constructed potential-pH diagram. The predominant regimes of the immunity, general corrosion, perfect passivation, imperfect passivation, and pitting corrosion were determined based on those lines of potentials. Comparing to the potential-pH diagram of specimens immersed in the aerated and deaerated 3550-ppm NaCl solutions, the addition of 3000-ppm $Na_2SO_4$ to these solutions increased the overall, perfect and imperfect, passivation regime by shifting the transpassive-potential line to the noble direction. However, it also widened the imperfect passivation area. The addition of $Na_2SO_4$ did not significantly affect the corrosion potential. It was found that the dissolved oxygen tends to negatively shift the transpassive-potential and protection-potential lines at all studied pH. The considerable effect of dissolved oxygen on corrosion and primary-passivation potentials could not be observed.

• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.636-641
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• 2016

Alkaline water electrolysis is commercial hydrogen production technology. It is possible to operate MW scale plant. Because It used non-precious metal for electrode. But It has relatively low current density and low efficiency. In this study, research objective is development of anode for alkaline water electrolysis with low cost, high corrosion resistance and high efficiency. Stainless steel 316L (SUS 316L) was selected for a substrate of electrode. To improve corrosion resistance of substrate, Nickel (Ni) layer was electrodeposited on SUS 316L. Ni-Fe alloy was electrodeposited on the passivated Ni layer as active catalyst for oxygen evolution reaction(OER). We optimized preparation condition of Ni-Fe alloy electrodeposition by changing current density, electrodeposition time and composition ratio of Ni-Fe electrodeposition bath. This electrodes were electrochemically evaluated by using Linear sweep voltammetry (LSV) and Cyclic voltammetry (CV). The Ni-Fe alloy (Ni : Fe = 1 : 1) showed best activity of OER. The optimized electrode decreased overpotential about 40% at $100mA/cm^2$ compared with Ni anode.

• 한국표면공학회지
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• 제52권4호
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• pp.194-202
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• 2019

A systematic investigation was made on the influence of processing parameters such as gas composition and treatment temperature on the surface characteristics of hardened layers of low temperature plasma nitrided 316L Austenitic Stainless Steel. Various nitriding processes were conducted by changing temperature ($370^{\circ}C$ to $430^{\circ}C$) and changing $N_2$ percentage (10% to 25%) for 15 hours in the glow discharge environment of a gas mixture of $N_2$ and $H_2$ in a plasma nitriding system. In this process a constant pressure of 4 Torr was maintained. Increasing nitriding temperature from $370^{\circ}C$ to $430^{\circ}C$, increases the thickness of S phase layer and the surface hardness, and also makes an improvement in corrosion resistance, irrespective of nitrogen percent. On the other hand, increasing nitrogen percent from 10% to 25% at $430^{\circ}C$ decreases corrosion resistance although it increases the surface hardness and the thickness of S phase layer. Therefore, optimized condition was selected as nitriding temperature of $430^{\circ}C$ with 10% nitrogen, as at this condition, the treated sample showed better corrosion resistance. Moreover to further increase the thickness of S phase layer and surface hardness without compromising the corrosion behavior, further research was conducted by fixing the $N_2$ content at 10% with introducing various amount of $CH_4$ content from 0% to 5% in the nitriding atmosphere. The best treatment condition was determined as 10% $N_2$ and 5% $CH_4$ content at $430^{\circ}C$, where the thickness of S phase layer of about $17{\mu}m$ and a surface hardness of $980HV_{0.1}$ were obtained (before treatment $250HV_{0.1}$ hardness). This specimen also showed much higher pitting potential, i.e. better corrosion resistance, than specimens treated at different process conditions and the untreated one.

• 한국물환경학회지
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• 제34권3호
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• pp.316-327
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• 2018

Liquid fertilizers made from livestock manure contain high concentrations of nitrogen and phosphorus and thus are used as a fertilizer. However, excessive use of liquid fertilizer causes eutrophication of agricultural land and nonpoint source pollution. In this study, as a means of lowering the nutrient concentrations, struvite ($MgNH_4PO_4{\cdot}6H_2O$) production from the liquid fertilizer was investigated. When liquid fertilizers produced in Gyeonggido were analyzed, its characteristics differed by region and season, but the phosphorus concentration was commonly lower than that of nitrogen. When $K_2HPO_4$ and $MgCl_2$ were added to the liquid fertilizers, the optimal pH for struvite formation was pH 9.5. For environmentally friendly sources of magnesium and phosphate, ferronickel slag (FNS) and sewage sludge ash (SSA) were suspended in deionized water and extracted by sulfuric acid with various mass ratios. The optimum conditions for extracting FNS and SSA were 4.0 M sulfuric acid and 0.35 mass ratio of sulfuric acid to sewage sludge ash, respectively. For forming struvite, 0.233 L of SSA leachate (SSAL) was added into 0.3 L of liquid fertilizer containing 2,586 mg/L of ammonia and 110 mg/L of phosphate, pH was then adjusted to pH 9.5 using 10 M of NaOH. Afterwards 0.333 L of FNS leachate (FNSL) was added to this mixed solution. After a reaction for 1 hr at room temperature, the remaining concentrations of magnesium, ammonium, and phosphate were less than 50 mg/L, 500 mg/L and 150 mg/L, respectively, and 30 g of precipitates were obtained, most of which were struvite.

• 생명과학회지
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• 제30권6호
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• pp.491-500
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• 2020

유산균은 장 건강, 심장질환, 우울증, 비만 등을 예방하고 치료할 수 있다고 널리 알려져 있고, 특히 한국은 다양한 발효식품에서 유산균을 섭취할 수 있다. 하지만 국내 발효식품에서 분리된 유산균에 대한 연구는 대부분 김치에 한정되어 있기 때문에 대표적인 어류 전통 발효식품인 식해류의 유산균에 대한 연구는 미비한 실정이다. 따라서 본 연구는 한국의 전통발효식품인 가자미 식해의 발효에 관여하는 유산균의 배양일에 따른 균총의 변화를 관찰하고, 가자미 식해로부터 프로바이오틱스로 이용 가치가 있는 균을 분리하기 위해 시행되었다. 포항의 가정집에서 제조된 가자미 식해에서 유산균을 제조일로부터 50일까지 5일 간격으로 분리하고 동정하였고, 동정 결과 P. pentosaceus, P. inopinatus, Lc. mesenteroides, L. brevis, L. plantarum 5개 균주가 발효에 관여함을 알 수 있었다. 발효가 진행됨에 따라 초기 발효에는 Pediococcus sp.가, 중기 이후부터는 Lactobacillus sp.가 우세하게 발효에 관여하는 것을 확인할 수 있었다. 분리한 유산균 중 우수한 프로바이오틱 활성을 가지는 균주를 알아보기 위하여 산내성, 담즙산 내성 시험을 통해 균주를 선별한 뒤 응집능, 표면 소수성, 항균 활성, 항산화 활성 등을 평가하였다. 그 결과 본 연구의 가자미 식해 분리 균주 중 최종적으로 선택된 소화액 내성이 뛰어난 L. brevis GS1022와 응집능이 뛰어난 P. inopinatus GS316은 프로바이오틱 균주로 이용할 가치가 충분하다고 사료된다.

• Nuclear Engineering and Technology
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• 제40권2호
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• pp.147-154
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• 2008

The general corrosion behavior of austenitic and ferritic steels(316L, 304, N controlled 304L, and 410) in supercritical water is investigated in this paper. After exposure to deaerated supercritical water at $480^{\circ}C$/25 MPa for up to 500 h, the four steels studied were characterized using gravimetry, scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction(XRD). The results show that the 316L steel with a higher Cr and Ni content has the best corrosion-resistance performance among the steels tested. In addition to the oxide layer mixed with $Fe_{3}O_{4}$ and $(Fe,Cr)_{3}O_{4}$ that formed on all the samples, a $Fe_{3}O_{4}$ loose outer layer was observed on the 410 steel. The corrosion mechanism of stainless steels in supercritical water is discussed based on the above results.

• 산업기술연구
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• 제21권B호
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• pp.11-20
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• 2001

This laboratory study examined the impact of free chlorine residual and pipe material on the formation of biofilm in drinking water distribution pipe surfaces. Result of heterotrophic plate counts(HPC) of the biofilm in the tap water-supplied reactor averaged $2.17{\times}10^5CFU/cm^2$ on PVC and $2.43{\times}10^5CFU/cm^2$ on STS 316, respectively. HPCs on the surface exposed to the tap water containing 0.2mg/L of free chlorinne residual averaged $4.24{\times}10^4CFU/cm^2$ on PVC and $6.54{\times}10^4CFU/cm^2$ on STS 316, respectively. Average of HPC/Total direct counts in the tap water-supplied reactor ranged from 1.08%(PVC) to 1.26%(STS 316) and from 0.38%(PVC) to 0.65%(STS 316) in the reactor supplemented with disinfectant, respectively. No correlation was observed between disinfectant addition and biofilm density. With regard to the biofilm formation, little difference existed between PVC and STS 316. Yellow and red pigmented bacteria were the dominant expressions in bulk fluid, whereas non-pigmented bacteria were found dominant in the biofilm. Pink/red pigmented bacteria were found to be facultative anaerobic, while yellow pigmented bacteria and non-pigmented bacteria were found to be obligate aerobic.

• 한국미생물·생명공학회지
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• 제23권3호
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• pp.329-336
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• 1995

For the development of new antitumor antibiotics produced by microorganisms, Streptomyces sp. YBE-316 was isolated from soil. The productivity of the antitumor antibiotic from Streptomyces sp. YBE-316 gradually increased after 60 hours, and was maximum after 100 hours after inoculation in growth medium (2.0% sucrose, 1.0% soybean meal, 0.1% K$_{2}$HPO$_{4}$, pH 7.0) at 30$\circ$C, 150 rpm, 5 NL/min by 30 l jar fermentor. This antitumor antibiotic was present only in mycelium, and stable in pH 5.0-10.0 for 20 minutes at 100$\circ$C. Antitumor and antibiotic activities were maintained at neutral pH, and heat stability was low. This antitumor antibiotic was soluble in methanol and ethanol, and insoluble in water, ethyl acetate, chloroform, and n-hexane. This antitumor antibiotic was sequentially purified by acetone extraction from mycelium, butanol extraction, and silica gel column chromatography. Antitumor activity was low against most tested cell lines, but antibiotic activity was high and low against yeasts and bacteria, respectivelv. The visualization test showed that this antitumor antibiotic had higher hydroxyl, ketone, amino, carboxyl groups, and sugar(s) in its structure. Instrumental analyses showed that this antitumor antibiotic was a pentaene in polyene class antibiotics. In pentaene class antibiotics, this was considered as an eurocidin or capacidin type antibiotics. The molecular weight of this antitumor antibiotic was higher than 683.0 daltons, and this antitumor antibiotic might be glycosylated by other sugar(s), instead of mycosamine or perosamine, an amino sugar.

• 한국어류학회지
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• 제26권3호
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• pp.194-201
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• 2014

태안 연안에서 이각망에 어획된 숭어 이석을 관찰하여 연령을 사정하고, 이석 윤문의 폭으로부터 체장을 역추정하여 성장을 추정하였다. 태안 연안 숭어는 외해에서 산란하여 유어기를 보낸 후 성어가 연안으로 들어온 것으로 보이며, 관찰한 숭어의 전장은 239~605 mm 범위였으며, 400~550 mm 크기의 개체가 주를 이루었다. 나이는 1~7세 범위였고 3~5세어가 가장 많았다. 전장(L, mm)은 이석의 장반경(R, ${\mu}m$)에 유의하게 일차 비례하였다(L=15.3+87.9 R). Frazer-Lee의 방법으로 추정한 각 연륜이 형성되었을 때의 전장은 1세어의 평균(${\pm}SD$)은 $316{\pm}40.6mm$로 초기 성장이 빨랐으며, 각 나이에서 그 범위가 넓어 개체에 따른 성장률 차이가 큰 것으로 보인다. 역추산한 전장은 Von Bertalanffy의 성장식 $L_t=542[1-{\exp}\{-0.493(t+0.769)\}]$로 유의하게 회귀되었다.