• 센서학회지
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• 제33권2호
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• pp.63-69
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• 2024

A novel method for measuring hydrogen concentration is introduced, along with its working principle and a novel detection algorithm. This configuration requires no additional reference compartment for potentiometric electrochemical measurements; therefore, it is the most suitable for measuring dissolved hydrogen in the liquid phase. The sensor's electromotive force saturates at a certain point, depending on the hydrogen concentration during the heating process of the sensor operation. This dynamic temperature scanning method provides higher sensitivity than the constant temperature measurement method.

• 한국진공학회지
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• 제8권4B호
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• pp.507-513
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• 1999

8mol%-yttria-stabilized zirconia(YSZ) thin films as oxygen ion conductor were deposited by rf-magnetron sputtering, and the oxygen gas sensors with the structure of $SiO_2$ substrate/Ni-NiO mixed reference layer/Pt/YSZ/Pt were fabricated and their oxygen sensing properties were investigated. The steady-state electro-motive force (EMF) values were measured as a function of oxygen partial pressure ($PO_2;form 1.013\times10^3 \textrm{Pa \;to}\; 1.013\times10^5$Pa) and operating temperature ($300^{\circ}C$ to $700^{\circ}C$). The fabricated YSZ oxygen sensor showed the best oxygen sensing properties at 50$0^{\circ}C$. However, oxygen sensing properties were very low at the temperature lower than 30$0^{\circ}C$ due to the lack of oxygen ion mobility and at the temperature higher than $700^{\circ}C$ due 새 intermixing of materials between the layers. Especially, the YSZ sensor operating at $500^{\circ}C$ and oxygen partial pressure above $1.565\times10^4$Pa showed the oxygen sensing properties close to the values predicted by ideal Nernst equation.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1465-1468
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• 2014

In this study, an intermediate temperature ionic conductor, $Ce_{0.95}Eu_{0.05}P_2O_7$, was prepared by solid state reaction. The variation of conductivities with the pressure $pH_2O$ or time were studied. The highest conductivity of $Ce_{0.95}Eu_{0.05}P_2O_7$ sample was observed in dry air atmosphere at $300^{\circ}C$ to be $1.1{\times}10^{-4}S{\cdot}cm^{-1}$ and in wet air atmosphere ($pH_2O=7.4{\times}10^3Pa$) at $100^{\circ}C$ to be $1.4{\times}10^{-3}S{\cdot}cm^{-1}$, respectively. The log ${\sigma}$ ~ log ($pO_2$) plot result indicated that $Ce_{0.95}Eu_{0.05}P_2O_7$ was almost a pure ionic conductor under high oxygen partial pressure and a mixed conductor of ion and electron under low oxygen partial pressure.

• 한국결정성장학회지
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• 제29권5호
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• pp.187-191
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• 2019

고체전지, 산화물연료전지, 센서, 산화물 분리막 등 에너지 재료로 활용이 무궁한 산소 이온 전도체 중 acceptor가 첨가된 $LaAlO_3$의 전기적 특성과 고온에서의 혼합전도체로 사용 가능성을 연구하였다. Sr과 Mg을 $LaAlO_3$에 동시에 첨가하여 만든 LSAM의 전기적 특성을 교류(a.c.)와 직류(d.c.) 방법을 이용하여 다양한 산소 분압에서 측정하였다. 교류 임피던스 방법을 이용하여 LSAM의 전체 저항에서 입자(grain) 저항과 입계(grain boundary) 저항을 분리한 결과, $550^{\circ}C$ 이하의 온도에서는 입계 저항이 지배적이나 $800^{\circ}C$ 이상의 온도에서는 입자 저항이 대부분임을 알 수 있었다. 또 산소분압에 따른 전도도 측정을 물질의 결함모델(defect model)을 이용하여 분석해 전체 전도도를 이온 전도도와 전자 전도도로 분리하였다. 그 결과, $800^{\circ}C$ 이상의 고온에서 LSAM은 낮은 산소분압($Po_2$ < $10^{-10}atm$)에서는 산소이온 전도체이고 높은 산소분압($Po_2$ > $10^{-5}atm$)에서는 혼합전도체의 거동을 보였다. 또 온도가 증가하여도 산소이온 전도가 주도적인 산소분압의 영역은 줄어들지 않았고 낮은 산소분압에서도 안정적인 전기적 특성을 보이는 등으로 보아, LSAM은 고온의 낮은 산소분압(T > $1500^{\circ}C$, $Po_2$ < $10^{-10}atm$) 조건에서 용강에서의 산소이온센서와 같은 산소이온체로의 사용 가능성이 높다.

• Korean Membrane Journal
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• 제9권1호
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• pp.34-42
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• 2007

A perovskite-type ($La_{0.6}Sr_{0.4}Ti_{0.2}Fe_{0.8}O_{3-{\delta}}$) dense ceramic membrane was prepared by polymerized complex method, using citric acid as a chelating agent and ethylene glycol as an organic stabilizer. Effect of Ti addition on lanthanum-strontium ferrite mixed conductor was investigated by evaluating the thermal expansion coefficient, the oxygen flux, the electrical conductivity, and the phase stability. The thermal expansion coefficient in air was $21.19\;{\times}\;10^{-6}/K$ at 473 to 1,223 K. At the oxygen partial pressure of 0.21 atm ($20%\;O_2$), the electrical conductivity increased with temperature and then decreased after 973 K. The decrement in electrical conductivity at high temperatures was explained by a loss of the lattice oxygen. The oxygen flux increased with temperature and was $0.17\;mL/cm^2{\cdot}min$ at 1,223 K. From the temperature-dependent oxygen flux data, the activation energy of oxygen ion conduction was calculated and was 80.5 kJ/mol at 1,073 to 1,223 K. Also, the Ti-added lanthanum-strontium ferrite mixed conductor was structurally and chemically stable after 450 hours long-term test at 1,173 K.

• 한국세라믹학회지
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• 제32권3호
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• pp.359-365
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• 1995

The grain boundary effect on the ionic conductivity was investigated using a.c. admittance analysis in (Bi2O3)0.715(CaO)0.285 oxygen-ion conducting solid electrolyte. As a separated arc representing grain boundary polarization was not observed in the admittance plane, bulk conductivity was measrued for samples with various grain sizes in the temperature range from 48$0^{\circ}C$ to 72$0^{\circ}C$ and the conductivity distribution between grain interior and grain boundary was determined by the reported analytical methods. In the above temperature range, grain boundary worked as a high conductive path instead of blocking layer and ionic conduction through grain boundary was significant. The activation energy for conduction through grain and grain boundary was 78 and 106 kJ/mol, respectively.

• 한국세라믹학회지
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• 제52권5호
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• pp.299-303
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• 2015

The electrolyte is an important component in determining the performance of Fuel Cells. Especially, investigation of the conduction properties of electrolytes plays a key role in determining the performance of the electrolyte. The electrochemical properties of Yttrium stabilized zirconia (YSZ) were measured to allow the use of this material as an electrolyte for solid oxide fuel cells (SOFC) in the temperature range of $700-1000^{\circ}C$ and in $0.21{\leq}pO_2/atm{\leq}10^{-23}$. A Hebb-Wagner polarization experimental cell was optimally manufactured; here we discuss typical problems associated with making cells. The partial conductivities due to electrons and holes for 8YSZ, which is known as a superior oxygen conductor, were obtained using I-V characteristics based on the Hebb-Wagner polarization method. Activation energies for holes and electrons are $3.99{\pm}0.17eV$ and $1.70{\pm}0.06eV$ respectively. Further, we calculated the oxygen ion conductivity with electron, hole, and total conductivity, which was obtained by DC four probe conductivity measurements. The oxygen ion conductivity was dependent on the temperature; the activation energy was $0.80{\pm}0.10eV$. The electrolyte domain was determined from the top limit, bottom limit, and boundary (p=n) of the oxygen partial pressure. As a result, the electrolyte domain was widely presented in an extensive range of oxygen partial pressures and temperatures.

• 한국철도학회논문집
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• 제4권2호
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• pp.62-70
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• 2001

Pure copper, Cu-1.1wt%Cd and ACSR(Aluminum Conductor Steel Reinforced) have been used as catenary materials of the electric railway system. Since these materials may be exposed to the corrosive environments like polluted air, acid rain and sea water, it is important to investigate the corrosion rates in various corrosive environments. The aqueous corrosion characteristics of catenary materials in aerated acid, neutral and alkali solutions were studied by using immersion corrosion tests, electrochemical measurements and analytical techniques. In order to examine corrosion characteristics according to the dissolved oxygen content, pH, chloride ion concentration ion, and the addition of Cd to Cu, a series of tests such as potentiodynamic polarization, a.c impedance spectroscopy and galvanic corrosion tests were carried out with these materials. Results showed that the addition of Cd to Cu and chloride ion in the solution have an adverse effects on the resistance to corrosion. Additionally, Galvanic currents between Al and steel wires of ACSR were confirmed by using ZRA(zero resistance ammeter) method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.535-542
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• 2000

전차선로 가선재료에는 순수구리로 이루어진 전차선, 카드뮴이 포함된 조가선, steel과 Al의 이종금속으로 이루어진 ACSR이 있고 이들 재료는 산성비와 같은 부식환경에 노출되어 있다. 따라서 다양한 부식환경에서의 이들 재료의 부식특성 및 부식속도를 규명하는 것은 매우 중요한 일이다 이에 본 실험에서는 pH, 용존산소 및 염소이온의 영향을 동전위분극시험, 선형분극시험, 교류임피던스시험 및 갈바닉시험 등의 전기화학적 분석기법을 통해 가선재료의 부식거동 및 부식속도를 조사하였다. 실험 결과 카드뮴이 함유된 재료의 부식저항성이 순수구리로 이루어진 재료에서의 부식저항성보다 낮은 것을 확인하였고, 염소이온이 내식성을 감소시킨다는 것을 관찰하였으며, 갈바닉시험 결과 산성용액에서 염소이온을 첨가하였을 경우 steel의 높은 갈바닉부식 전류밀도를 ZRA 법을 통해 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.7-7
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• 2011

Quantum beam technology has been expected to develop breakthroughs for nanotechnology during the third basic plan of science and technology (2006~2010). Recently, Green- or Life Innovations has taken over the national interests in the fourth basic science and technology plan (2011~2015). The NIMS (National Institute for Materials Science) has been conducting the corresponding mid-term research plans, as well as other national projects, such as nano-Green project (Global Research for Environment and Energy based on Nanomaterials science). In this lecture, the research trends in Japan and NIMS are firstly reviewed, and the typical achievements are highlighted over key nanotechnology fields. As one of the key nanotechnologies, the quantum beam research in NIMS focused on synchrotron radiation, neutron beams and ion/atom beams, having complementary attributes. The facilities used are SPring-8, nuclear reactor JRR-3, pulsed neutron source J-PARC and ion-laser-combined beams as well as excited atomic beams. Materials studied are typically fuel cell materials, superconducting/magnetic/multi-ferroic materials, quasicrystals, thermoelectric materials, precipitation-hardened steels, nanoparticle-dispersed materials. Here, we introduce a few topics of neutron scattering and ion beam nanofabrication. For neutron powder diffraction, the NIMS has developed multi-purpose pattern fitting software, post RIETAN2000. An ionic conductor, doped Pr2NiO4, which is a candidate for fuel-cell material, was analyzed by neutron powder diffraction with the software developed. The nuclear-density distribution derived revealed the two-dimensional network of the diffusion paths of oxygen ions at high temperatures. Using the high sensitivity of neutron beams for light elements, hydrogen states in a precipitation-strengthened steel were successfully evaluated. The small-angle neutron scattering (SANS) demonstrated the sensitive detection of hydrogen atoms trapped at the interfaces of nano-sized NbC. This result provides evidence for hydrogen embrittlement due to trapped hydrogen at precipitates. The ion beam technology can give novel functionality on a nano-scale and is targeting applications in plasmonics, ultra-fast optical communications, high-density recording and bio-patterning. The technologies developed are an ion-and-laser combined irradiation method for spatial control of nanoparticles, and a nano-masked ion irradiation method for patterning. Furthermore, we succeeded in implanting a wide-area nanopattern using nano-masks of anodic porous alumina. The patterning of ion implantation will be further applied for controlling protein adhesivity of biopolymers. It has thus been demonstrated that the quantum beam-based nanotechnology will lead the innovations both for nano-characterization and nano-fabrication.