• Carbon letters
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• 제6권1호
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• pp.31-40
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• 2005

The carbon nanofibers (CNFs) were synthesized through the catalytic decomposition of hydrocarbons in a quartz tube reactor. The CNFs prepared from $C_3H_8$ at $550^{\circ}C$ was selected as the purification sample due to the higher content of impurity than that prepared from other conditions. In this study, we carried out the purification of CNFs by oxidation in air or carbon dioxide after acid treatment, and investigated the influence of purification parameters such as kind of acid, concentration, oxidation time, and oxidation temperature on the structure of CNFs. The metal catalysts could be easily eliminated from the prepared CNFs by liquid phase purification with various acids and it was verified by ICP analysis, in which, for example, Ni content decreased from 2.51% to 0.18% with 8% nitric acid. However, the particulate carbon and heterogeneous fibers were not removed from the prepared CNFs by thermal oxidation in air and carbon dioxide. This result can be explained by that the direction of graphene sheet in CNFs is vertical to the fiber axis and the CNFs are oxidized at about the similar rate with the impurity carbon.

• 한국산림과학회지
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• 제61권1호
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• pp.27-36
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• 1983

본(本) 연구(硏究)는 질산(窒酸)펄프화법의 기술(技術)을 확립하기 위한 기초자료(基礎資料)를 얻기 위하여 실시(實施)하였다. 값이 비싸고 목재(木材)에 침투성(浸透性)이 불량(不良)한 질산(窒酸)을 직접 적용시키지 아니하고, 알카리전처리(前處理)로 어느정도 탈리그닌이 진행된 시료(試料)를 사용, 질산(窒酸)펄프화 2단증해(段蒸解)를 행하여 전처리(前處理)가 탈리그닌 및 펄프수율(收率)에 미치는 영향(影響) 및 펄프화 과정(過程)에서의 탄수화물(炭水化物)과 리그닌의 용출(溶出)거동을 구명(究明)코저 하였다. 질산(窒酸)펄프화의 제(第) 1 단증해(段蒸解)에 있어서 증해시간(蒸解時間)이 증가함에 따라 펄프수율(收率)이 감소하였으며 질산농도(窒酸濃度) 1, 2%보다 3%가 펄프수율(收率) 및 탈리그닌에 현저히 영향(影響)하였다. 또한 알카리전처리(前處理)는 질산(窒酸)펄프의 수율(收率)에 크게 영향하였으며 79%의 전처리수율(前處理收率)로서 충분한 탈리그닌 효과(効果)를 얻을 수 있었다. 질산(窒酸)펄프화 과정에서 용출(溶出)되는 탄수화물(炭水化物)은 주로 xylose였으며, 이들의 용출(溶出)은 증해시간(蒸解時間)이 증가함에 따라 증가되었는바, 이는 탄수화물(炭水化物)에 대한 질산(窒酸)의 산화작용(酸化作用)으로 도입된 carbonyl기(基)가 탄수화물(炭水化物)의 붕괴를 초래한 결과로 생각된다.

• 한국재료학회지
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• 제17권5호
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• pp.244-249
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• 2007

The properties of anodized films on aluminum 6061 alloy in single electrolyte of sulfuric acid and mixed electrolyte of sulfuric-boric acid and sulfuric-boric-nitric acid have been studied. Polarization tests in NaC solution were used to investigate the corrosion performance. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM and EDS. The results obtained have indicated that oxide films growth have been promoted by nitric acid and anodized films in mixed electrolyte have superior corrosion resistance. In case of anodic films formed in mixed electrolyte, some grooves and numerous crazings were also observed at the surface.

• 약학회지
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• 제42권6호
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• pp.583-588
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• 1998

These experiments were investigated effects of the cell death of glycyrrhetinic acid (GA) on transplanted-L1210 cells in BALB/c mice. The GA suppressed the proliferation of L121 0 cells in vivo and in vitro system. The administration of GA induced apoptosis of transplanted-L1210 cells via the reduction of mitochondrial transmembrane potential in mice. The GA enhanced the production of nitric oxidation in peritoneal macrophages obtained from L1210 cells-transplanted mice. The apoptosis of L1210 cells were induced by co-culture of the macrophages obtained from GA administered mice and L1210 cells in vitro, and was partly inhibited by the treatment of L-NMMA. These results suggest that GA induces the cytotoxicity and the apoptosis of transplanted-L1210 cells via the production of nitric oxide in peritoneal macrophages.

• 열처리공학회지
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• 제31권1호
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• pp.6-11
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• 2018

The anodic oxidation behavior of Si-containing aluminum alloy for diecasting was investigated. Especially, the property changes during anodization both on aluminum 1050 and 9 weight percentage silicon containing aluminum (Al-9Si) alloys were analyzed by the static current test. In order to fabricate a uniform anodic oxidation film by effect of Al-Si compound, nitric acid containing hydrofluoric acid had been used as a desmutter for aluminum alloy after alkaline etching. It was found that the level of voltage of Al-9Si alloy during the static current test was almost as double as higher than aluminum 1050 through anodization. By adding hydrofluoric acid in the nitric acid electrolyte, the silicon compound on the surface was removed, and the optimum amount of added hydrofluoric acid could be derived. It was also observed that the size of silicon compound formed on the surface could be refined by heat treatment at $500^{\circ}C$ and followed water quenching.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.369-372
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• 2009

In the present study, the effect of chemical treatment on graphite nanofibers (GNFs) supports with various concentrated nitric acids was investigated for methanol oxidation. To optimize the electrocatalytic activity, PtRu catalysts were deposited on GNF supports by impregnation method. The surface and structural properties of the GNF supports were characterized by X-ray photoelectron spectroscopy (XPS), element analyzer (EA), and X-ray diffraction (XRD). The morphology of the catalysts was observed by means of transmission electron microscopy (TEM). The electrocatalytic activity of PtRu/GNF catalysts was investigated by cyclic voltammetry measurement. As a result, the oxygen functional groups were introduced on the GNF supports and were gradually increased with increasing of concentrated nitric acid, causing the smaller particle size and higher loading level. And the electrocatalytic activity of the catalysts for methanol oxidation was gradually improved. Consequently, it was found that chemical treatments could influence on surface properties of the carbon supports, resulting in enhancing the electrocatalytic activity of the catalysts for DMFCs.

• Korean Journal of Acupuncture
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• 제25권4호
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• pp.89-104
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• 2008

Objectives : This study was undertaken to determine the in vitro antioxidant activity of the extract of Chilgitang herb-acupuncture solution (CHAS). Methods : The radical scavenging capacity was tested by 2,2-diphenyl-1-picryl-hydrazyl (DPPH), hypoxanthine-xanthine oxidase system, DCFH-DA assay, nitric oxide and peroxynitrite generating system. In addition, antioxidant activity on copper and AAPH mediated human low-density lipoprotein (LDL) oxidation was measured by using TBARS assay and relative electrophoretic mobility assay. The amount of total phenolic compounds was assayed by the Folin-Ciocalteu method. Results : CHAS revealed a potent scavenging activity on DPPH radical(82%), superoxide anions(73%), hydroxyl radical(63%), nitric oxide (99%) and peroxynitrite (99%). Moreover, CHAS showed a strong inhibitory effect (59%) on $FeCl_2$-ascorbic acid induced lipid peroxidation of rat liver homogenate. CHAS also markedly inhibited copper(81%) and AAPH(56%)-mediated LDL oxidation, and effectively suppressed the electrophoretic mobility during exposure of human LDL to copper ions. CHAS (82 mg/g) contained higher concentration of total phenolic compounds than that of water extract (45 mg/g) obtained from Chilgitang. Conclusions : These results indicate that CHAS may protect against ROS- or RNS involved diseases, including cardiovascular diseases.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2034-2040
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• 2020

The gas evolution from mixtures consisting of 0.2 M solution of N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) in n-alcohol (n-decanol or n-nonanol) with Isopar-M diluent was investigated during thermal oxidation. The effect of ionizing radiation on their thermal stability has been studied. It has been determined that the volume of gaseous thermolysis products increases by 260% in the case of n-nonanol and 80% in the case of n-decanol compared to non-irradiated solutions. It has been shown that the gas evolution rate and gas volume increase when the irradiated mixture saturated with nitric acid is heated. However, there are no prerequisites for the development of autocatalytic oxidation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.248-249
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• 2014

Photocatalytic cement is receiving attention due to its high oxidation power that oxidizes nitrogen oxides (NOx), thus contributing to clean atmospheric environment. However, there has not been a thorough investigation on durability of a parent material, cementitious material, as a result of photocatalytic reactions. In this study, durability of photocatalytic cementitious materials exposed to nitrogen dioxide (NO₂) gas was examined. Titanium dioxide (TiO₂) nanoparticles containing cement paste samples were exposed to cycles of NO₂ with UV light, followed by wetting and drying to simulate environmental condition. The surface of samples was characterized mechanically, chemically, and visually during the cycling. The results indicate that the photocatalytic efficiency decreased with continued NO₂ oxidation due to calcium carbonate formation. The pits found from SEM demonstrate that chemical deterioration have occurred, such as acid attack or leaching. In conclusion, the photocatalytic reactions and its product could alter cementitious materials chemically and mechanically which could further affect long-term durability.

• 대한환경공학회지
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• 제33권10호
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• pp.774-781
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• 2011

지르코늄합금 튜브 제조공정은 튜브 산세 시 질산과 불산을 사용하고 있어 세척 시 발생되는 폐수의 주요 오염물질인 질산성질소와 불소성분을 제거하기 위한 폐수처리는, 1차 화학응집처리에 의한 불소성분 제거공정, 황산화탈질반응을 이용한 SOD (Sulfur Oxidation Denitrification)공법에 의한 독립영양탈질공정, 그리고 2차 화학응집처리공정으로 구성되어 있다. 본 연구에서는, 처리공정에서 불소의 농도가 황산화탈질공정(SOD)의 탈질반응에 미치는 영향과 황산화탈질반응을 유지하기 위한 최적 운전조건을 검토하였다. 황산화탈질 반응은 불소농도 20 ppm 이하에서 거의 영향을 주지 않았으며, NaOH로 pH를 조절하는 것보다 NaOH와 $NaHCO_3$를 혼합하여 pH와 알칼리도를 조절해주는 것이 질소제거당량을 높여주는 효과가 있는 것으로 나타났다. 또한, 황산화탈질미생물에 필요한 미량원소와 알칼리성분이 혼합된 미생물활성화제가 알칼리도를 보충해줄 뿐만 아니라 황산화탈질미생물의 성장과 증식에도 영향을 주었으며, 그 결과 무기계 산업폐수처리 시 필요한 주기적인 미생물 식종 없이 운전이 가능한 결과를 얻었다. 이상의 결과를 통해, 황산화탈질공법(SOD공법)이 산업폐수의 질산성질소제거에 매우 유용한 공법임이 확인되었으며, 미생물활성화제가 황산화탈질미생물의 활성화에 기여함이 밝혀졌다.