• 한국결정성장학회지
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• 제19권5호
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• pp.228-236
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• 2009

본 연구에서는 $SF_6$ 가스 포접 하이드레이트 결정이 생성되고 성장하는 메커니즘의 특성을 기술하였다. 실험은 일정한 압력과 온도에서 2상 실험($SF_6$ 기상/수용액상)과 3상 실험($SF_6$ 기상/수용액상/$SF_6$ 액상)의 서로 다른 두 가지 상 조건에서 이루어졌다. 두 조건 모두 기체 영역과 수용액 영역 사이의 경계면에서 하이드레이트 결정의 수지상이 섬유상 형태로 상향 성장하는 거동을 보였다. 3상 실험의 경우 하이드레이트 생성이 진행됨에 따라, 반응기 내부압의 감소로$SF_6$ 액상에서 생성된 기포가 기체와 수용액 계면의 막에 도달하여 기포의 표면이 하이드레이트로 전환되었다. 본 논문에서는 결정의 핵생성과 이동, 성장, 간섭을 중심으로 $SF_6$ 가스하이드레이트 결정의 성장 특성을 기술하였다.

• 열처리공학회지
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• 제8권4호
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• pp.289-301
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• 1995

The effect of Air/$C_3H_8$ gas addition on the compound layer growth of steels nitrocarburised in $NH_3+Air+C_3H_8$ mixed gas atmospheres was investigated. It is considered that amount of residual $NH_3$ was varied according to alternation of Air/$C_3H_8$ mixing ratio and volume content. The compound layer formed from nitrocarburising was composed of ${\varepsilon}-Fe_{2-3}$(C, N) and ${\gamma}^{\prime}-Fe_4$(C, N). According as Air/$C_3H_8$ mixing ratio increased, the superficial content of ${\gamma}^{\prime}-Fe_4$(C, N) within the compound layer was increased, at the same time the growth rate of compound layer and porous layer was increased. In the case of alloy steel at the fixed gas composition, the growth rate of compound layer and porous layer was worse than carbon steel and compound layer phase composition structure primarily consisted of E phase. As the carbon content of materials was increasing in the given gas atmospheres, the growth rate of compound layer and porous layer was increased and the superficial content of ${\varepsilon}-Fe_{2-3}$(C, N) within the compound layer was increased.

• 한국재료학회지
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• 제25권10호
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• pp.543-546
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• 2015

$TiO_2$ nanowires were grown by thermal oxidation of TiO powder in an oxygen and nitrogen gas environment at $1000^{\circ}C$. The ratio of $O_2$ to $N_2$ in an ambient gas was changed to investigate the effect of the gas ratio on the growth of $TiO_2$nanowires. The oxidation process was carried out at different $O_2$/$N_2$ ratios of 0/100, 25/75, 50/50 and 100/0. No nanowires were formed at $O_2$/$N_2$ ratios of less than 25/75. When the $O_2$/$N_2$ ratio was 50/50, nanowires started to form. As the gas ratio increased to 100/0, the diameter and length of the nanowires increased. The X-ray diffraction pattern showed that the nanowires were $TiO_2$ with a rutile crystallographic structure. In the XRD pattern, no peaks from the anatase and brookite structures of $TiO_2$were observed. The diameter of the nanowires decreased along the growth direction, and no catalytic particles were detected at the tips of the nanowires which suggests that the nanowires were grown with a vapor-solid growth mechanism.

• 농업과학연구
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• 제46권1호
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• pp.1-10
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• 2019

The objective of this study was to determine the effect of multi-enzyme supplementation in a corn and soybean meal-based diet on the growth performance, apparent nutrient digestibility, blood profile, fecal microbes and noxious gas emission in growing pigs. A total of 80 crossbred [(Landrace ${\times}$ Yorkshire) ${\times}$ Duroc] growing pigs with an average body weight (BW) of $25.04{\pm}1.44kg$ were used in a 6-week experiment. The experimental treatments were as follows: CON, basal diet and; T1, basal diet + 100 mg/kg multi-enzyme. During the experiment, the pigs fed the diet with multi-enzyme supplementation had a higher gain to feed ratio (G/F) (p < 0.05) than the pigs fed the diet without multi-enzyme supplementation. On day 42, the pigs fed the diet with multi-enzyme supplementation had decreased $H_2S$ and $NH_3$ emissions (p < 0.05) than the pigs fed the diet without multi-enzyme supplementation. However, no effect was observed on nutrient digestibility, blood profiles and fecal microbes among the treatments (p > 0.05). In conclusion, it is suggested that multi-enzyme supplementation in a corn and soybean meal based diet can partly improve the growth performance and noxious gas emission of growing pigs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.210-210
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• 2000

Vertically well aligned multi-wall carbon nanotubes (CNT) were grown on nickel coated glass substrates by plasma enhanced hot filament chemical vapor deposition at low temperatures below 600$^{\circ}C$. Acetylene and ammonia gas were used as the carbon source and a catalyst. Effects of growth parameters such as pre-treatment of substrate, plasma intensity, filament current, imput gas flow rate, gas composition, substrate temperature and different substrates on the growth characteristics of CNT were systematically investigated. Figure 1 shows SEM image of CNT grown on Ni coated glass substrate. Diameter of nanotube was 30 to 100nm depending on the growth condition. The diameter of CNT decreased and density of CNT increased as NH3 etching time etching time increased. Plasma intensity was found to be the most critical parameter to determine the growth of CNT. CNT was not grown at the plasma intensity lower than 500V. Growth of CNT without filament current was observed. Raman spectroscopy showed the C-C tangential stretching mode at 1592 cm1 as well as D line at 1366 cm-1. From the microanalysis using HRTEM, nickel cap was observed on the top of the grown CNT and very thin carbon amorphous layer of 5nm was found on the nickel cap. Current-voltage characteristics using STM showed about 34nA of current at the applied voltage of 1 volt. Electron emission from the vertically well aligned CNT was obtained using phosphor anode with onset electric field of 1.5C/um.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.711-711
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• 2009

Global warming has been widely recognized as a serious problem threatening the future of human beings. It is caused by the buildup in the atmosphere of greenhouse gases, such as carbon dioxide, methane, hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6). Particularly, SF6 has extremely high global warming potential compare to those of other global warming gases. One option for mitigating this greenhouse gas is the development of an effective process for capturing and separating these gases from anthropogenic sources. In general, gas hydrates can be formed under high pressure and low temperature. However, SF6 gas is known to form hydrate under relatively milder conditions. Therefore, technological and economical effects could be expected for the separation of SF6 gas from waste gas mixtures. In this study, we carried out morphological study for the SF6 hydrate crystals to understand its formation and growth mechanisms. The observations were made in high-pressure optical cell charged with liquid water and SF6 gas at constant pressure and temperature. Initially SF6 hydrate formed at the surface between gas and liquid regions, and then subsequent dendrite crystals grew at the wall above the gas/water interface. The visual observations of crystal nucleation, migration, growth and interference were reported. The detailed growth characteristics of SF6 hydrate crystals were discussed in this study.

• 한국결정성장학회지
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• 제9권1호
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• pp.14-19
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• 1999

Hexamethyldisilane$(Si_{2}(CH_{3})_{6})$의 single precursor를 사용하여 화학기상증착법으로 $1100^{\circ}C$에서 Si 기판의에 $\beta$-SiC 막을 증착시켰다. 증착과정 중 hexamethyldisilane/$H_{2}$ gas system에 HCI gas를 도입하여 mask 재료에 의해 부분적으로 덮여져 있는 Si 기판에서 SiC 증착의 선택성을 조사하였다. Si 기판과 mask 재료에서 SiC 증착의 선택성을 증진시키기 위해 출발물질과 HCI gas의 공급 방법을 변화시켰다. 결국, HCI gas를 도입함으로서 SiC 증착의 선택성은 증진되었고 펄스 형태로의 gas 공급 방법은 선택성을 향상시키는데 효율적이었다.

• Advances in materials Research
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• 제9권2호
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• pp.155-170
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• 2020

In this paper, using the recently introduced analytical approach for the analysis of mass and heat transfer during film growth in reactors for epitaxy from the gas phase, these processes are analyzed taking into account natural convection and the possibility of changing the rate of chemical interaction between reagents. As a result of the analysis, the conditions under which the homogeneity of the grown epitaxial layers increases with a change in the values of the parameters of the growth process are formulated.

• 기술사
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• 제45권4호
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• pp.30-34
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• 2012

Shale gas is one of the resources which require lots of new technologies for commercial production and has the most reserves among unconventional gas resources for commercial production at present. Especially, the growth of shale gas industry means the significant changes of paradigm and the development of shale gas is very different from conventional gas development in terms of geology, rock mechanics, petroleum engineering, development and production engineering. In this manner, shale gas may hold the key to expanding the long-term role of gas in the global energy mix.

• 한국결정성장학회지
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• 제20권2호
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• pp.85-92
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• 2010

$SF_6$ 가스는 아크방지능력과 절연 특성이 탁월하기 때문에 단열, 세척, 차폐등과 같은 여러 공업적인 영역에서 널리 사용되고 있다. 그러나 $SF_6$의 지구온난화지수는 $CO_2$의 23,900배에 달하며 3,200년 이상 공기중에 잔존한다. 이러한 이유로 하이드레이트 형성 원리를 이용하여 복합 가스에서 $SF_6$를 분리해 내는 방법이 기술적, 경제적인 면에 영향을 끼칠 것이다. 본 연구에서 $SF_6$ 하이드레이트 결정의 형성과 성장에 대한 이해를 위하여 형태학적 분석을 수행하였다. $SF_6$ 하이드레이트 필름은 용액과 기상의 계면에서 먼저 생성되었고, 이후에 수지상 가지의 형태로 성장하는 것이 관찰 되었다. 수지상 성장 결정은 기상의 방향으로 성장하였는데 이것은 객체 분자의 농도 차이에 근거한 것으로 사료된다. 본 연구에서는 기/액 계면에서의 핵생성, 유동, 성장과 같은 $SF_6$ 하이드레이트 결정의 형태학적 특성에 대하여 기술하였다.