• 한국분말재료학회지
• /
• 제16권1호
• /
• pp.43-49
• /
• 2009

Titanium carbides are widely used for cutting tools and grinding wheels, because of their superior physical properties such as high melting temperature, high hardness, high wear resistance, good thermal conductivity and excellent thermal shock resistance. The common synthesizing method for the titanium carbide powders is carbo-thermal reduction from the mixtures of titanium oxide($TiO_2$) and carbon black. The purpose of the present research is to fabricate nano TiC powders using titanium salt and titanium hydride by the mechanochemical process(MCP). The initial elements used in this experiment are liquid $TiCl_4$(99.9%), $TiH_2$(99.9%) and active carbon(<$32{\mu}m$, 99.9%). Mg powders were added to the $TiCl_4$ solution in order to induce the reaction with Cl-. The weight ratios of the carbon and Mg powders were theoretically calculated. The TiC and $MgCl_2$ powders were milled in the planetary milling jar for 10 hours. The 40 nm TiC powders were fabricated by wet milling for 4 hours from the $TiCl_4$+C+Mg solution, and 300 nm TiC particles were obtained by using titanium hydride.

• Korean Chemical Engineering Research
• /
• 제48권3호
• /
• pp.304-310
• /
• 2010

공침법을 이용하여 구조 조촉매인 $SiO_2$가 첨가된 Fe계 촉매와 $SiO_2$가 첨가되지 않은 Fe계 촉매를 제조하였고, 이러한 두 가지 촉매를 이용하여 $250^{\circ}C$의 온도 및 1.5 MPa의 압력에서 Fischer-Tropsch 합성반응을 수행하였다. $SiO_2$를 첨가한 Fe계 촉매가 $SiO_2$를 첨가하지 않은 Fe계 촉매보다 현저히 우수한 촉매활성을 나타내었고, 144시간의 반응시간동안 뛰어난 촉매안정성을 나타내었다. X-선 회절 및 $N_2$의 물리흡착을 통하여 촉매의 결정구조 및 세공구조를 분석한 결과, $SiO_2$를 첨가할 경우 Fe계 촉매의 분산도가 향상되는 것을 발견할 수 있었다. 또한 $H_2$-TPR(temperature-programmed reduction) 분석결과를 통해, $SiO_2$를 첨가할 경우 $260^{\circ}C$ 이하의 저온 영역에서 $Fe_2O_3$의 $Fe_3O_4$ 및 FeO로의 환원이 촉진되는 것을 확인하였다. 반면 $CO_2$-TPD(temperature-programmed desorption) 분석결과에 의하면, $SiO_2$를 첨가한 결과 촉매의 표면 염기도는 감소하였다. 따라서 $SiO_2$를 첨가한 촉매가 $SiO_2$를 첨가하지 않은 촉매보다 우수한 촉매성능을 나타내는 것은, $SiO_2$를 첨가함에 따라 촉매의 분산이 증진되고 환원이 촉진된 것이 주요 원인인 것으로 생각된다.

• 자원리싸이클링
• /
• 제31권1호
• /
• pp.21-28
• /
• 2022

폐리튬이온배터리를 고온에서 용융환원시키면 코발트, 니켈 및 구리 금속합금상을 얻을 수 있다. 이러한 금속합금상으로부터 금속을 분리회수하기 위한 공정을 개발하기 위해 코발트, 니켈 및 구리 금속을 혼합한 금속혼합물을 3% 과산화수소를 함유한 2 M 황산용액으로 침출하면 9.6%의 구리와 함께 코발트와 니켈이 모두 침출된다. 침출용액에서 Cyanex 301로 구리(II)가 선택적으로 추출되었으며, 30% 왕수로 구리(II)를 탈거했다. 구리가 분리된 여액에서 이온성액체인 ALi-SCN으로 Co(II)를 선택적으로 추출했으며, 15%의 암모니아용액으로 3단의 교차식 탈거를 통해 모두 탈거했다. 본 연구를 통해 코발트, 니켈 및 구리 금속혼합물의 황산침출액에서 용매추출로 세 금속을 분리할 수 있는 공정을 제안했다.

• 한국전기전자재료학회논문지
• /
• 제26권1호
• /
• pp.22-26
• /
• 2013

PTCR ceramics of $(Ba_{0.998}Sm_{0.002})TiO_3+0.001MnCO_3+xSiO_2$ (x=1, 2, 3, 4, 5, 6 mol%) were fabricated by solid state method. Disk samples of diameter 5 mm and thickness about 1mm were sintered at $1,290^{\circ}C$ for 2 h in reduced atmosphere of $5%H_2-95%N_2$ followed by re-oxidation at $600^{\circ}C$ for 30 min. in $20%O_2-80%N_2$.and their microstructures and electrical properties were investigated with SEM and Multimeter. The color of sintered samples was strongly dependent on $SiO_2$ content showing that the color of samples with $SiO_2$ of 1~2 mol% was gray but that of samples with $SiO_2$ of 4~6 mol% was changed from gray to blue, which seems to be related with the reduction of samples due to the oxygen vacancies created during the sintering in reduced atmosphere. $SiO_2$ content had a great influence on the microstructure and the electrical properties. With increasing $SiO_2$ content, the grain size of samples increased and the resistivity as well as the resistivity jump ($R_{285}/R_{min}$) decreased, which is considered to be attributed to the resistivity change at grain interior and grain boundary due to the fast mass transfer through $SiO_2$ liquide phase during the sintering. Samples with 2 mol% $SiO_2$ has the resistivity of $202{\Omega}cm$ and the resistivity jump of 3.28. It is expected that $SiO_2$ doped $BaTiO_3$ based PTC ceramics can be used for multilayered PTC thermistor due to the resistance to the sintering in reduced atmosphere.

• Journal of Dental Anesthesia and Pain Medicine
• /
• 제17권1호
• /
• pp.37-46
• /
• 2017

Background: In oxidative stress, reactive oxygen species (ROS) production contributes to cellular dysfunction and initiates the apoptotic cascade. Autophagy is considered the mechanism that decreases ROS concentration and oxidative damage. Propofol shows antioxidant properties, but the mechanisms underlying the effect of propofol preconditioning (PPC) on oxidative injury remain unclear. Therefore, we investigated whether PPC protects against cell damage from hydrogen peroxide ($H_2O_2$)-induced oxidative stress and influences cellular autophagy. Method: COS-7 cells were randomly divided into the following groups: control, cells were incubated in normoxia (5% $CO_2$, 21% $O_2$, and 74% $N_2$) for 24 h without propofol; $H_2O_2$, cells were exposed to $H_2O_2$ ($400{\mu}M$) for 2 h; $PPC+H_2O_2$, cells pretreated with propofol were exposed to $H_2O_2$; and 3-methyladenine $(3-MA)+PPC+H_2O_2$, cells pretreated with 3-MA (1 mM) for 1 h and propofol were exposed to $H_2O_2$. Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide thiazolyl blue (MTT) reduction. Apoptosis was determined using Hoechst 33342 staining and fluorescence microscopy. The relationship between PPC and autophagy was detected using western blot analysis. Results: Cell viability decreased more significantly in the $H_2O_2$ group than in the control group, but it was improved by PPC ($100{\mu}M$). Pretreatment with propofol effectively decreased $H_2O_2$-induced COS-7 cell apoptosis. However, pretreatment with 3-MA inhibited the protective effect of propofol during apoptosis. Western blot analysis showed that the level of autophagy-related proteins was higher in the $PPC+H_2O_2$ group than that in the $H_2O_2$ group. Conclusion: PPC has a protective effect on $H_2O_2$-induced COS-7 cell apoptosis, which is mediated by autophagy activation.

• Mycobiology
• /
• 제40권2호
• /
• pp.117-123
• /
• 2012

Nuruk contributes to the unique characteristics of Korean alcoholic beverages. In this study, the effects of nuruk extracts (NE) on anti-oxidant characters, melanogenesis, and anti-photoaging activity were investigated. NEs were obtained from the 70% ethanol extracts of six types of nuruk, which have been used in brewing of fermented alcohol beverages in Korea. First, various antioxidant characteristics were identified in terms of 2,2'-azino-bis(3-ethylbenzthiozoline-6-sulphonic acid) (ABTS) radical scavenging activity, superoxide dismutase (SOD) expression, and inhibition of xanthine oxidase activity. NE#4 exhibited potent ABTS radical scavenging activity ($IC_{50}$ = 19.51 ${\mu}g$/mL). Compared with NE#4, relatively lower levels of activity were observed for NE#3 and NE#6, with $IC_{50}$ values of 90.99 and 76.88 ${\mu}g$/mL, respectively. According to results of western blot analysis for determination of SOD expression in $H_2O_2$-treated HepG2 cells, NE#5 and NE#6 induced a dramatic increase in the expression ratio of SOD, compared to the group treated with $H_2O_2$ only. Activity of xanthine oxidase, which converts xanthine into uric acid, generating superoxide ions, was inhibited by NE#4 and NE#6 in a dose-dependent manner. NE#4 induced significant inhibition of mushroom tyrosinase activity. A reduction in cellular melanin contents of 80% was observed in B16F1 melanocytes treated with NE#5 and NE#6; these effects were similar to those of arbutin at 100 ${\mu}M$. In addition, gelatin zymography and reverse transcription-PCR analysis were performed for assessment of anti-photoaging activity of Nuruk. Treatment with NE#6 resulted in dramatically inhibited activities of matrix metalloproteinase (MMP)-2/-9, suppressed expression of MMP-1, and increased expression of type-1 procollagen. Results of gelatin zymography for NE#4 and NE#5 were similar, to a slightly lesser degree. These results suggest the potential of NE#4 and NE#6 as natural ingredients for use in functional foods and cosmetics.

• 한국식품영양과학회지
• /
• 제43권11호
• /
• pp.1674-1680
• /
• 2014

잡곡밥 메탄올 추출물이 가지는 산화적 스트레스 개선 효과를 확인하기 위하여 $H_2O_2$로 유도된 산화적 스트레스에 대한 LLC-PK1 세포의 보호 효과를 조사하였다. $250{\mu}M$의 $H_2O_2$에 의한 산화적 스트레스가 유발된 LLC-PK1 세포에 시료추출물을 처리한 결과, WR, TMR, GR 순으로 $H_2O_2$ 처리군에 비해 세포 생존율이 증가하였다(P<0.05). 특히 GRS와 GRK에서 정상군에 가까운 세포 생존율을 나타내어 $H_2O_2$에 의한 산화적 스트레스로 유발된 세포 손상에 대한 잡곡밥 추출물의 보호 효과를 확인할 수 있었다. 세포 내 활성산소(ROS)의 수준과 세포 내 지질과산화물질(MDA)의 생성 억제 효과 역시 WR, TMR, GR, GRK, GRS 순으로 증가하는 것을 관찰하였다. $H_2O_2$로 인하여 세포 내 항산화 효소인 SOD, CAT와 GSH-px 등의 활성이 감소된 LLC-PK1 세포에 잡곡밥 추출물을 처리했을 때 이들 효소의 활성이 증가했으며 특히 GRK, GRS군에서 현저하게 증가되었다. LLC-PK1 세포에서 $H_2O_2$에 의해 발생하는 산화적 스트레스에 대한 보호 효과를 측정한 결과 잡곡밥 추출물은 세포 손상을 억제하고 세포 내 활성산소(ROS)의 수준과 지질과산화물질(MDA)의 생성을 억제하며, 세포 내 항산화 효소의 활성을 증가시키는 효과를 가지는 것으로 보인다. 또한 항산화 효소유전자 발현에서도 위와 비슷한 효과를 나타내었다. 이상의 결과로 잡곡밥 메탄올 추출물, 특히 기능성 물질인 카레가루와 상황버섯 추출물이 첨가된 잡곡밥은 LLC-PK1 세포에 대한 보호 작용과 in vitro에서의 항산화 효과가 높은 것으로 확인되었다.

• Tuberculosis and Respiratory Diseases
• /
• 제43권6호
• /
• pp.987-996
• /
• 1996

연구배경: 기존의 양압환기법은 기관내관이나 기관절개술을 통해서만 시행되어 왔으나 최근 이러한 인공기도에 의한 기도합병증을 피하기 위한 방법으로 안연 또는 코마스크를 환자~인공환기기 사이의 매체로 이용하는 비침습적 환기법 (noninvasive positive pressure ventilation, 이하 NIV라 함)이 시도되고 있다. 이에 저자 등응 급성호흡부전 환자들에서 NIV의 적용 가능성, 치료성공율 및 치료성공과 연관된 지표를 알아보고자 본 연구를 시행하였다. 방법: 대상응 급성 환기부전 (acute vemilarory failure, 이하 VF : $PaCO_2$ > 43 mrn Hg & pH < 7.35)이나 급성 산소화호흡부전 (acure oxygenarion failure, 이하 OF : $PaO_2/FIO_2$ < 300 mrn Hg & $pH{\geq}7.35$)으로 기계호흡이 필요했던 환자 106 예 중 NIV 시도가 가능한 환자 26명이었으며, 총 VF 19예 중 11 예 (57.9%) (남 : 여 =7 : 4, $55.4{\pm}14.6$세), 총 OF 87예 중 15 예 (17.2%) (남 : 여 =12 : 3, $50.6{\pm}15.6$세)에서 NIV 시도가 가능하였다. 결과: 1. 기관내삽관 없이 NIV로 기계호흡 이탈까지 성공한 환자는 VF에서 81.8% (9/11), OF에서 40%(6/15)였다. NIV 의 합병증은 코부위 피부괴사와 가스성 위장 팽대 각 1예씩 이었다. 2. 환기부전 환자의 NIV 성공 예 에서 분당호흡 수는 기저치에 비해 NIV 시작 12시간 후(각각 $34{\pm}9$회, $26{\pm}6$회, p=0.045)에 유의한 감소를 보였다. $PaCO_2$와 pH는 모두 기저치에 비해 NIV 시작 24시간 후($PaCO_2$ 각각 $87.3{\pm}20.6$, $81.2{\pm}9.1$ mm Hg, p < 0.05, pH 각각 $7.26{\pm}0.04$, $7.32{\pm}0.02$, p < 0.05)에 유의한 호전을 보였다. 3. 산소화부전에서 NIV가 성공한 6 예와 실패한 9 예에서 $PaCO_2$는 NIV 시작전 (각각 $59.8{\pm}9.2$, $76.0{\pm}22.8$ mm Hg), NIV 시작 후 30분 (각각 $121.5{\pm}20.2$, $99.6{\pm}35.8$ mm Hg,), 6시간 (각각 $100.0{\pm}26.4$, $76.2{\pm}22.3$ mm Hg) 및 12시간 ($88.7{\pm}28.7$, $74.3{\pm}16.7$ mm Hg)에 서로 유의한 차이가 없었으나 (모두 p > 0.05), $PaO_2/FIO_2$ 비는 NIV 성공 예에서는 각각 $120.0{\pm}19.6$, $218.9{\pm}98.3$, $191.3{\pm}55.2$ 및 $232.8{\pm}17.6$ mm Hg (p=0.0211)로 상승한 반면, 실패 예에서는 $127.9{\pm}63.0$, $116.8{\pm}24.4$, $100.6{\pm}34.6$ 및 $129.8{\pm}50.3$ mm Hg (p=0.5319)로 유의한 상승이 관찰되지 않았다. 결론: 비침습적 환기법은 급성 환기부전군에서 급성 산소화부전에 비해 적용성과 성공율이 높으며, 환기부전의 NIV 성공 예에서는 분당호흡수의 감소가 선행하고 $PaO_2$와 pH의 호전이 뒤따랐고 산소화부전에서는 NIV 시작 30분 후의 $PaO_2/FIO_2$ 비가 성공적 NIV 적용 여부의 한 예측 지표가 될 수 있을 것으로 사료되었다.

• 산업기술연구
• /
• 제42권1호
• /
• pp.7-12
• /
• 2022

High nickel layered oxide cathodes are gaining increasing attention for lithium-ion batteries due to their higher energy density and lower cost compared to LiCoO₂. However, they suffer from the formation of residual lithium on the surface in the form of LiOH and Li₂CO₃ on exposure to ambient air. The residual lithium causes notorious issues, such as slurry gelation during electrode preparation and gas evolution during cell cycling. In this review, we investigate the residual lithium issues through its impact on cathode slurry instability based on deformed polyvinylidene fluoride (PVdF) as well as its formation and reduction mechanism in terms of inherently off-stoichiometric synthesis of high nickel cathodes. Additionally, new analysis method with anhydrous methanol was introduced to exclude Li⁺/H⁺ exchange effect during sample preparation with distilled water. We hope that this review would contribute to encouraging the academic efforts to consider practical aspects and mitigation in global high-energy-density lithium-ion battery manufacturers.

• 한국작물학회지
• /
• 제56권4호
• /
• pp.349-360
• /
• 2011

The objectives of present study were to characterize the peptides which were isolated from Korean fermented soybean paste, chungkukjang, and to determine their antioxidant activities. Four fractions were collected from the methanol extract of chungkukjang by using a recycling preparative HPLC. Among fractions, Fr-2 was identified to be highly potent free radical scavenging activity in the assay of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and nitroblue tetrazolium(NBT)-reduction inhibition. Base on antioxidant effects, fraction Fr-2 was employed for the refraction with a prep-column and separated into five fractions of which two fractions were identified to have higher antioxidant activity. To confirm the amino acid constituents of antioxidant fractions Fr-2-2 and Fr-2-3 were analyzed, and eight kinds of amino acids such as aspartic acid, threonine, serine, glutamic acid, glycine, lysine, histidine, and arginine were identified as the constituent amino acids. Antioxidant activities of the separated peptides were further assessed cell viability with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl terazolium bromide (MTT), and fluorescence-activated cell sorting (FACS) analysis of H4IIE cells treated with hydrogen peroxide (H2O2). Chungkukjang peptides have shown their ability to protect H4IIE rat hepatoma cells against H2O2- induced oxidative stress by concentration and time-dependent manner. Therefore, These results indicated that fermented soybean paste chungkukjang will be promoted the antioxidant and radical scavenging activities, and beneficial for health. The antioxidant peptide fractions Fr-2-2 and Fr-2-3 were denominated as P-NICS-1 and P-NICS-2, respectively. However, further studies were required to clarify their amino acid sequences and molecular properties, and physiological significances.