• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.716-721
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• 2009

The major drive for the application of low-temperature plasma treatment in nitrocarburizing of austenitic stainless steels lies in improved surface hardness without degraded corrosion resistance. The low-temperature plasma nitrocarburizing was performed in a gas mixture of $N_{2}$, $H_{2}$, and carbon-containing gas such as $CH_{4}$ at $450^{\circ}C$. The influence of the processing time (5~30 h) and $N_{2}$ gas composition (15~35%) on the surface properties of the nitrocarburized layer was investigated. The resultant nitrocarburized layer was a dual-layer structure, which was comprised of a N-enriched layer (${\gamma}_N$) with a high nitrogen content on top of a C-enriched layer (${\gamma}_C$) with a high carbon content, leading to a significant increase in surface hardness. The surface hardness reached up to about $1050HV_{0.01}$, which is about 4 times higher than that of the untreated sample ($250HV_{0.01}$). The thickness of the hardened layer increased with increasing treatment time and $N_{2}$ gas level in the atmosphere and reached up to about $25{\mu}m$. In addition, the corrosion resistance of the treated samples without containing $Cr_{2}N$ precipitates was enhanced than that of the untreated samples due to a high concentration of N on the surface. However, longer treatment time (25% $N_{2}$, 30 h) and higher $N_{2}$ gas composition (35% $N_{2}$, 20 h) resulted in the formation of $Cr_{2}N$ precipitates in the N-enriched layer, which caused the degradation of corrosion resistance.

• Journal of Food Hygiene and Safety
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• v.32 no.1
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• pp.64-69
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• 2017

This study was conducted to investigate the effect of cold plasma combined with UV-C irradiation against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes on lettuce. E. coli O157:H7, S. Typhimurium, and L. monocytogenes, corresponding to approximately 5.82, 5.09, 5.65 log CFU/g, were inoculated on lettuce, respectively. Then, the lettuce was treated with cold plasma, UV-C and combination (cold plasma + UV-C), respectively. The treated lettuce was stored for 9 days at $4^{\circ}C$ for microbiological analysis and sensory evaluation. Cold plasma reduced the populations of E. coli O157:H7, S. Typhimurium, and L. monocytogenes by 0.26, 0.65, and 0.93 log CFU/g, respectively. Each microorganism were reduced by 0.87, 0.88, and 1.14 log CFU/g after UV-C treatment. And, the combined treatment that was treated by cold plasma after UV-C treatment reduced the populations of inoculated microorganisms by 1.44, 2.70, 1.62 log CFU/g, respectively. The all treatment significantly (p < 0.05) reduced the populations of all inoculated bacteria compared to untreated lettuce. UV-C combined with cold plasma was the most effective for reducing the pathogenic bacteria on lettuce, by showing log-reductions of ${\geq}2.0\;log\;CFU/g$. All treatment was not significantly different until 6 day storage compared to control group in terms of appearance, texture and overall acceptability. Therefore, the combined treatment will be an effective intervention method to control the bacteria on lettuce.

• Journal of Surface Science and Engineering
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• v.37 no.5
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• pp.243-248
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• 2004

A palladium-nikel(Pd-Ni) alloy composite membrane has been fabricated on microporous nickel support formed with nickel powder. Plasma surface treatment process is introduced as pre-treatment process instead of HCI activation. Pd coating layer was prepared by dc magnetron sputtering deposition after $H_2$ plasma surface treatment. Palladium-nickel alloy composite layer had a fairly uniform and dense surface morphology. The membrane was characterized by permeation experiments with hydrogen and nitrogen gases at temperature of 773 K and pressure of 2.2psi. The hydrogen permeance was 6 ml/minㆍ$\textrm{cm}^2$ㆍatm and the selectivity was 120 for hydrogen/nitrogen($H_2$/$N_2$) mixing gases at 773 K.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.8
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• pp.1069-1085
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• 2011

In large-type goats that were fed on dry forage twice daily, dry forage intake was markedly suppressed after 40 min of feeding had elapsed. The objective of this study was to clarify whether or not increases in plasma osmolality and subsequent thirst sensations produced by dry forage feeding suppress dry forage intake. Eight large-type male esophageal- and ruminal-fistulated goats (crossbred Japanese Saanen/Nubian, aged 3 to 6 years, weighing $72.3{\pm}2.74$ kg) were used in two experiments conducted under sham feeding conditions. The animals were fed ad libitum a diet of roughly crushed alfalfa hay cubes for 2 h from 10:00 to 12:00 h during two experiments. Water was withheld during feeding in both experiments but was available for a period of 30 min after completion of the 2 h feeding period. In experiment 1, an intraruminal infusion of artificial parotid saliva (RIAPS) in the control replenished saliva lost via the esophageal fistula and an intraruminal infusion of hypertonic solution (RIHS) in the treatment was carried out in order to reproduce the effects of changing salt content due to feed entering the rumen. In experiment 2, the RIHS control was conducted in the same manner as the RIHS treatment of experiment 1. The treatment group consisted of RIHS-with an intravenous infusion of artificial mixed saliva (VIAMS) treatment that was carried out for 3 h to prevent increases in plasma osmolality during feeding. The results of the RIHS treatment in experiment 1 showed that ruminal fluid osmolality increased and then an increase in plasma osmolality was observed. This resulted in the production of thirst sensations and the reduction of cumulative dry forage intake to 43.3% (p<0.05) of the RIAPS control. The results of the RIHS-VIAMS treatment in experiment 2 indicated that ruminal fluid osmolality was the same as the RIHS control but plasma osmolality significantly decreased, and thirst level was markedly reduced. This caused a significant increase of 31.4% (p<0.05) in cumulative dry forage intake in the RIHS-VIAMS treatment compared to the RIHS control. These results indicate that increases in ruminal fluid osmolality during dry forage feeding indirectly suppresses dry forage intake by causing an increase in plasma osmolality and subsequently inducing thirst sensations. The results of the present study suggest that marked decreases in dry forage intake after 40 min of feeding are caused by increases in plasma osmolality and subsequent thirst sensations produced by dry forage feeding.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.1
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• pp.3-9
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• 2011

Plasma nitriding of stainless steels has been investigated over a range of temperature from 400 to $500^{\circ}C$ and time from 10 to 20 hours. Characterization of systematic materials was carried out in terms of mechanical properties and corrosion behaviors. The results showed that plasma nitriding conducted at low temperatures not only increased the surface hardness, but also improved the corrosion resistance of STS 316L, STS409L, and STS 420J2. It was found that plasma-nitriding treatment at $500^{\circ}C$ resulted in increasing the corrosion performance of STS 409L and STS 420J2, while STS 316L was observed with server and massive damage on surface due to the formation of CrN.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.164-165
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• 2007

The effect of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotubes (CNTs) has been systematically investigated. The plasma treatment resulted in the removal of the amorphous carbon particles. As the plasma treatment time was longer, the CNT diameter was reduced, regardless of gas types. Especially, for the sample treated in hydrogen plasma, the catalyst metal on the tip of CNTs was eliminated.

• Membrane and Water Treatment
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• v.4 no.2
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• pp.109-126
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• 2013

Surface modification by low-pressure ammonia ($NH_3$) plasma on commercial thin-film composite (TFC) membranes was investigated in this study. Surface hydrophilicity, total surface free energy, ion exchange capacity (IEC) and zeta (${\zeta}$)-potentials were determined for the TFC membranes. Qualitative and quantitative analyses of the membrane surface chemistry were conducted by attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy. Results showed that the $NH_3$ plasma treatment increased the surface hydrophilicity, in particular at a plasma treatment time longer than 5 min at 50 W of plasma power. Total surface free energy was influenced by the basic polar components introduced by the $NH_3$ plasma, and isoelectric point (IEP) was shifted to higher pH region after the modification. A ten (10) min $NH_3$ plasma treatment at 90 W was found to be adequate for the TFC membrane modification, resulting in a membrane with better characteristics than the TFC membranes without the modification for water treatment. The thin-film chemistry (i.e., fully-aromatic and semi-aromatic nature in the interfacial polymerization) influenced the initial stage of plasma modification.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.275-280
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• 2010

The influence of $O_2$-plasma treatment on $H_2$ post-treated BZO (ZnO:B) thin film using MOCVD (Metal-Organic Chemical Vapor Deposition) are investigated. An $O_2$-plasma treatment of the $H_2$ post-treated BZO thin films resulted in XRD peak of (100), (101) and (110). Also, electrical properties resulted in an increase in sheet resistance and work function. The weighted optical transmittance and haze at 300~1,100 nm of BZO thin films with $O_2$-plasma treatment on the $H_2$ post-treatment show approximately 86% and 15%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.632-635
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• 2001

Microcrystalline Si films have been deposited by using five W-wire filaments of 0.5 mm diameter for hot-wire chemical vapor deposition (HWCVD). We compared the HWCVD grown films with the film exposed to transformer couple plasma system for the modification of seed layer. W-wire filament temperature was maintained below 1600$^{\circ}C$ to avoid metal contamination by thermal evaporation at the filament. Deposition conditions were varied with H$_2$dilution ratio, with and without plasma treatment. From the Raman spectra analysis, we observed that the film crystallization was strongly influenced by the H$_2$dilution ratio and weakly depended on the distance between the wire and a substrate. We were able to achieve the crystalline volume fraction of about 70% with an SiH$_4$/H$_2$ratio of 1.3%, a wire temperature of 1514$^{\circ}C$, a substrate separation distance of 4cm, and a chamber pressure of 38 mTorr. We investigated the influence of ${\mu}$c-Si film properties by using a plasma treatment. This article also deals with the influence of the H$_2$dilution ratio in crystallization modification.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.121-121
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• 2011

Graphene formed by chemical vapor deposition was exposed to the various plasmas of Ar, O2, N2, and H2 to examine its effects on the bonding properties of graphene to metal. Upon the Ar plasma exposure of patterned graphene, the subsequently deposited metal electrodes remained intact, enabling successful fabrication of field effect transistor (FET) arrays. The effects of enhancing adhesion between graphene and metals were more evident from O2 plasmas than Ar, N2, and H2 plasmas, suggesting that chemical reaction of O radicals induces hydrophilic property of graphene more effectively than chemical reaction of H and N radicals and physical bombardment of Ar ions. From the electrical measurements (drain current vs. gate voltage) of field effect transistors before and after Ar plasma exposure, it was confirmed that the plasma treatment is very effective in controlling bonding properties of graphene to metals accurately without requiring buffer layers.