• 제목/요약/키워드: oxygen potential

검색결과 1,428건 처리시간 0.03초

밀폐식 Ni-Cd 전지의 충전특성에 관한 연구 (Study on the Charging Characteristics of a Sealed Type Ni-Cd Cell)

  • 박영우;김재원;전무식
    • 대한화학회지
    • /
    • 제15권6호
    • /
    • pp.347-352
    • /
    • 1971
  • The variations of the positive and negative electrode potentials, and of internal pressure were measured during the charge of the sealed type Ni-Cd cell. Both polarization characteristics of a paste type Cd-electrode as a gas diffusion electrode in 30% KOH solution and the effects of active carbon electrode as an oxygen consuming auxiliary electrode of the Ni-Cd cell on the charging characteristics of the cell were studied. Peak voltage at the end of charge of the cell is ascribed to the peak at the negative electrode potential, which is due to the concentration polarization by the lack of $Cd^{++}$ ion and oxygen concentration. And the recovery of the negative electrode potential is resulted from depolarization by the increasing diffusion limiting current density with the increasing oxygen pressure. The active carbon electrode was effective as an oxygen consuming auxiliary electrode. The internal pressure of the cell could be maintained below 200mmHg even at one hour rate charge and overcharge by the use of active carbon electrode as an auxiliary electrode.

  • PDF

산소환원반응 촉매용 질소 도핑된 탄소나노섬유의 제조 (Synthesis of Nitrogen-doped Carbon Nanofibers for Oxygen Reduction Reaction)

  • 안건형;이은환;안효진
    • 한국분말재료학회지
    • /
    • 제23권6호
    • /
    • pp.420-425
    • /
    • 2016
  • N-doped carbon nanofibers as catalysts for oxygen-reduction reactions are synthesized using electrospinning and carbonization. Their morphologies, structures, chemical bonding states, and electrochemical performance are characterized. The optimized N-doped carbon nanofibers exhibit graphitization of carbon nanofibers and an increased nitrogen doping as well as a uniform network structure. In particular, the optimized N-doped carbon nanofibers show outstanding catalytic activity for oxygen-reduction reactions, such as a half-wave potential ($E_{1/2}$) of 0.43 V, kinetic limiting current density of $6.2mAcm^{-2}$, electron reduction pathways (n = 3.1), and excellent long-term stability after 2000 cycles, resulting in a lower $E_{1/2}$ potential degradation of 13 mV. The improvement in the electrochemical performance results from the synergistic effect of the graphitization of carbon nanofibers and the increased amount of nitrogen doping.

열처리 온도에 따라서 절연체, 반도체, 전도체의 특성을 갖는 GZO 박막의 특성연구 (Study on GZO Thin Films as Insulator, Semiconductor and Conductor Depending on Annealing Temperature)

  • 오데레사
    • 한국재료학회지
    • /
    • 제26권6호
    • /
    • pp.342-346
    • /
    • 2016
  • To observe the bonding structure and electrical characteristics of a GZO oxide semiconductor, GZO was deposited on ITO glasses and annealed at various temperatures. GZO was found to change from crystal to amorphous with increasing of the annealing temperatures; GZO annealed at $200^{\circ}C$ came to have an amorphous structure that depended on the decrement of the oxygen vacancies; increase the mobility due to the induction of diffusion currents occurred because of an increment of the depletion layer. The increasing of the annealing temperature caused a reduction of the carrier concentration and an increase of the bonding energy and the depletion layer; therefore, the large potential barrier increased the diffusion current dna the Hall mobility. However, annealing temperatures over $200^{\circ}C$ promoted crystallinity by the defects without oxygen vacancies, and then degraded the depletion layer, which became an Ohmic contact without a potential barrier. So the current increased because of the absence of a potential barrier.

Electrochemistry and Leaching Kinetics of Gold-Silver Alloys in Cyanide Solutions

  • Guan, Y.Charles;Sun, Xiaowei;Han, Kenneth N.
    • 자원리싸이클링
    • /
    • 제10권1호
    • /
    • pp.42-48
    • /
    • 2001
  • The dissolution behavior of gold and silver from gold-silver alloys in aerated cyanide solutions has been investigated by an electrochemical means as well as a direct measurement of gold and silver ions reported in the bulk solution as a function of time using rotating disc electrodes. The variables studied included oxygen partial pressure, rotating speed of the disc, concentration of cyanide, temperature and composition of the allyos. The dissolution potential and the rate of dissolution were obtained in view of the anodic and cathodic current-potential relationships. The results were discussed in terms of the mixed potential theory. The results showed that the dissolution rate of gold and silver from the alloys was controlled partially by chemical reaction. but largely by transport of either oxygen or cyanide, depending on their relative concentration under the experimental conditions employed in this study.

  • PDF

Corrosion Characteristics of Amorphous Alloy Ribbon ($Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$) in Hydrochloric Acid Aqueous Solution

  • Choi, Chil-Nam;Hyo, Kyung-Yang;Yang, Myung-Sun
    • 한국환경과학회:학술대회논문집
    • /
    • 한국환경과학회 2001년도 정기총회 및 봄 학술발표회 초록집
    • /
    • pp.236-237
    • /
    • 2001
  • In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves with amorphous $Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$ alloy ribbon. The results were particularly examined to identify the influences of corrosion potential including various conditions such as hydrochloric acid, temperature, salt, pH, and oxygen. The optimum conditions were established with variations including temperature, salt, pH, oxygen, corrosion rate, and resistance of corrosion potential. The mass tranfer coefficient(${\alpha}$) value was determined with the Tafel's slope for the anodic dissolution based on the polarization effect with optimum conditions. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity($I_{r}/I_{f}$).

  • PDF

저온 플라스마 공정을 이용한 알루미늄 표면의 건식 세정에 관한 연구 (A Study on the Dry Cleaning of Aluminium Surfaces by Low Temperature Plasma Process)

  • 임경택;김경환;김경석;이휘지;송선정;손호경;조동련
    • 공업화학
    • /
    • 제19권6호
    • /
    • pp.640-644
    • /
    • 2008
  • 저온 플라스마 공정을 이용하여 알루미늄 표면에 묻은 윤활유를 세정하였다. 아르곤이 혼합된 산소 플라스마를 사용하였으며, 아르곤의 혼합비, 방전전력, negative DC potential 등의 공정변수를 변화시키면서 실험을 수행하였다. 저온 플라스마 세정 후 케이스의 표면을 FTIR과 EDX를 사용하여 분석한 결과 순수 윤활유의 경우 대부분이 20 min 안에 제거되었다. 제거효율은 저온 플라스마 공정조건에 따라 크게 달라졌으며, 산소에 아르곤이 약 30% 혼합된 기체를 사용하여 케이스에 -500 V 이상의 negative DC potential을 걸어주고 300 W로 처리할 때 가장 높은 효율을 보였다. 하지만, 무기물이 함유된 윤활유의 경우에는 어떤 조건에서도 60% 이상의 제거효율을 얻을 수 없었다.

산소중독에 대한 Glutathione과 Chlorpromazine의 보호효과에 관한 실험적 연구 (A STUDY ON POTENTIAL PROTECTIVE ACTIVITIES OF GLUTATHIONE AND CHLORPROMAZINE AGAINST OXYGEN TOXICITY)

  • 임현술;윤덕로
    • Toxicological Research
    • /
    • 제6권2호
    • /
    • pp.143-157
    • /
    • 1990
  • Effective measure to prevent oxygen toxicity is greatly required as there increase chances to be exposed to high oxygen pressure, for example, space travel, deep sea diving and hyperbaric oxygen therapy. In the present study, in an attempt to evaluate glutathione and chlorpromazine as protective agents against oxygen toxicity, effects of the agents were tested on various toxicities (death rate, convulsion rate, time to convulsion, increase in weight of lung and brain and pathological changes in the organs) observed in rats exposed to 5 Absolute Atmosphere (ATA) of 100% oxygen for 120 minute. Glutathione reduced mortality rate and convulsion rate and also markedly suppressed the increase in lung and brain weight. The pathological changes observed in these organs were ameliorated by administration of glutathione. Chlorpromazine also reduced mortality rate but its effects appeared to be limited mainly to pulmonary toxicities. Thus glutathione seems to be more effective than chlorpromazine as a protective agent. The results obtained may support that oxygen toxicity is mediated by oxygen free radicals.

  • PDF

Photophysical Efficiency Factors of Singlet Oxygen Generation from Core-modified Trithiasapphyrin Derivatives

  • Ha, Jeong-Hyon;Kim, Min-Sun;Park, Yong-Il;Ryu, Shin-Hyung;Park, Mi-Gnon;Shin, Koo;Kim, Yong-Rok
    • Bulletin of the Korean Chemical Society
    • /
    • 제23권2호
    • /
    • pp.281-285
    • /
    • 2002
  • The photophysical properties and the singlet oxygen generation efficiencies of meso-tetraphenyl-trithiasapphyrin $(S_3TPS)$ and meso-tetmkis(p-methoxy phenyl)-trithiasapphy rin ((p-MeO)-$S_3TPS$) have been investigated, utilizing steady-state and time-resolved spectroscopic methods to elucidate the possibility of their use as photosensitizers for photodynamic therapy (PDT). The observed photophysical properties were compared with those of other porphyrin-like photosensitizers in geometrical and electronic structural aspects, such as extended ${\pi}$ conjugation, structural distortion, and internal heavy atoms. The steady-state electronic absorption and fluorescence spectra were both red-shifted due to the extended ${\pi}$-conjugation. The fluorescence quantum yields were measured as very small. Even though intersystem crossing rates were expected to increase due to the increment of spin orbital coupling, the triplet quantum yields were measured as less than 0.15. Such characteristics can be ascribed to the more enhanced internal conversion rates compared with the intersystem crossing rates. Furthermore, the triplet state lifetimes were shortened to -1.0 ${\mu}s$ as expected. Therefore, the singlet oxygen quantum yields were estimated to be near zero due to the fast triplet state decay rates and the inefficient energy transfer to the oxygen molecule as well as the low triplet quantum yields. The low efficiencies of energy transfer to the oxygen molecule can be attributed to the lower oxidation potential and/or the energetically low lying triplet state. Such photophysical factors should be carefully evaluated as potential photosensitizers that have extended ${\pi}$-conjugation and heavy core atoms synthesized for red-shifted absorption and high triplet state quantum yields.

Sap Temperature Distribution of the Xylem and Leaf Water Status of Apple Trees in Relation to Soil Oxygen Diffusion Rates

  • Ro, Hee-Myong
    • Journal of Applied Biological Chemistry
    • /
    • 제43권3호
    • /
    • pp.170-175
    • /
    • 2000
  • A pot-lysimeter experiment was conducted with 3-year-old 'Tsugaru' apple (Malus domestica Borkh) trees to examine the changes in oxygen diffusion rate (ODR) with lateral flow velocity of water through soil. The influence of lateral water flow velocity on water relations and elemental content in leaf, and sap temperature distribution patterns of the xylem of trees were also determined. Trees were grown under four soil water regimes: (1) fast laterally flowing (FWT, $2.50{\times}10^{-4}cm\;s^{-1}$), (2) slow laterally flowing (SWT, $0.25{\times}10^{-4}cm\;s^{-1}$), and (3) stagnant water table (WLT) at 60-cm, and (4) drip-irrigation at -40 kPa of soil matric potential as a control. The rate of $O_2$ diffusion converged near $2{\times}10^{-3}g\;m^{-2}\;min^{-1}$ for FWT and control soils, but decreased below $1{\times}10^{-3}g\;m^{-2}\;min^{-1}$ 40 days after treatment (DAT) for WLT soils. For SWT soils, however, the ODR at 15 cm below the soil surface was similar to that of control, but at 45 cm below the soil surface, ODR was similar to that of the WLT treatment. Leaf water potential of FWT and SWT plants was similar to that of control plants, but the values for SWT plants declined by 98 DAT. Leaf water potential of WLT plants decreased from -1.86 MPa (9 DAT) to -2.41 MPa (59 DAT) and finally down to -2.70 MPa. The sap temperature measured at 1100-hr was lowest at top and highest at bottom for FWT and control plants, but this pattern of SWT and WLT plants was disturbed from 29 DAT. However, for SWT plants, such thermal disturbance of sap temperature disappeared from 63 DAT.

  • PDF

스크린 인쇄법에 의한 용존 산소센서의 제조 및 특성 (Fabrication of Dissolved Oxygen sensors by Screen Print Method and Characteristic)

  • 정경진;이성필
    • 한국전기전자재료학회:학술대회논문집
    • /
    • 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
    • /
    • pp.926-929
    • /
    • 2003
  • The dissolved oxygen sensor of thick film type was fabricated by screen print method and measured the characteristic, reference electrode used Ag/AgCl, and working electrode used Pt. The devices are continuously powered at potential of $0.7V{\sim}0.8V$ versus Ag/AgCl reference electrode and results indicated that the response characteristic of sensor was $1.002{\mu}A{\sim}19.792{\mu}A$ for thirty seconds. we can know that it is good linearity when compared with of existent dissolved oxygen meter. Therefore sensor fabricated excels sensitivity for dissolved oxygen and will be considered to be applied typically because the price is costly.

  • PDF