• 전자공학회논문지T
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• 제36T권1호
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• pp.8-12
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• 1999

산소이온 펌핑효과를 나타내는 8% 이트리아가 함유된 ZrO\sub 2\ 이온 전도체를 기판으로 하여 그 위에 NO\sub x\가스에 대해 감지효과를 갖고 있는 것으로 알려져 있는 WO\sub 3\산화물 반도체를 사용하여 박막시편을 제작하였다. 각 소자의 NO\sub x\ 가스에 대한 전기적 특성과 열처리 온도에 따른 미세구조의 변화를 조사하였고, 특히 8YSZ 기판에 가해준 전압에 의한 NO\sub x\ 가스 감지의 증대효과를 조사하였다. 열처리 온도에 따른 WO\sub 3\ 박막표면의 SEM사진의 분석에서 열처리하지 않은 WO\sub 3\ 박막은 비결정질 상태이지만 600℃이상의 열처리 온도에서 결정화가 이루어졌고 사방경계상의 WO\sub 3\ 피크가 나타났으며 온도가 증가함에 따라 (111)면과 (001)면이 특히 많이 성장하였다. 측정온도 400℃에서 8YSZ 기판에 전압을 가하지 않았을 때보다 전압을 가하였을 경우가 더 안정되고 더 큰 응답을 보였으며, 특히 2V 일 때가 가장 높은 감도를 나타내었다. 그리고 NO\sub 2\ 가스보다 NO 가스에 대한 회복특성이 훨씬 우수했다.

• 한국세라믹학회지
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• 제47권1호
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• pp.82-85
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• 2010

Recently, thin film processes for oxides and metal deposition, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), have been widely adapted to fabricate solid oxide fuel cells (SOFCs). In this paper, we presented two research area of the use of such techniques. Gadolinium doped ceria (GDC) showed high ionic conductivity and could guarantee operation at low temperature. But the electron conductivity at low oxygen partial pressure and the weak mechanical property have been significant problems. To solve these issues, we coated GDC electrolyte with a nano scale yittria-doped stabilized zirconium (YSZ) layer via atomic layer deposition (ALD). We expected that the thin YSZ layer could have functions of electron blocking and preventing ceria from the reduction atmosphere. Yittria-doped barium zirconium (BYZ) has several orders higher proton conductivity than oxide ion conductor as YSZ and also has relatively high chemical stability. The fabrication processes of BYZ is very sophisticated, especially the synthesis of thin-film BYZ. We discussed the detailed fabrication processes of BYZ as well as the deposition of electrode. This paper discusses possible cell structure and process flow to accommodate such films.

• Journal of Electrochemical Science and Technology
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• 제8권2호
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• pp.101-106
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• 2017

$Li_2SiO_3$ was used as a coating material to improve the electrochemical performance of $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$. $Li_2SiO_3$ is not only a stable oxide but also an ionic conductor and can, therefore, facilitate the movement of lithium ions at the cathode/electrolyte interface. The surface of the $Li_2SiO_3$-coated $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ was covered with island-type $Li_2SiO_3$ particles, and the coating process did not affect the structural integrity of the $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ powder. The $Li_2SiO_3$ coating improved the discharge capacity and rate capability; moreover, the $Li_2SiO_3$-coated electrodes showed reduced impedance values. The surface of the lithium-ion battery cathode is typically attacked by the HF-containing electrolyte, which forms an undesired surface layer that hinders the movement of lithium ions and electrons. However, the $Li_2SiO_3$ coating layer can prevent the undesired side reactions between the cathode surface and the electrolyte, thus enhancing the rate capability and discharge capacity. The thermal stability of $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ was also improved by the $Li_2SiO_3$ coating.

• 공업화학
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• 제20권3호
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• pp.317-321
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• 2009

고체 산화물 전해질로 사용되고 있는 초 이온 전도체인 $K^+-{\beta}/{\beta}"-Al_2O_3$의 고온 상관계와 소결성 분석을 위하여 $K_2O-LiO_2-Al_2O_3$ 삼성분계로부터 고상반응을 통하여 순수한 $K^+-{\beta}/{\beta}"-Al_2O_3$ 분말을 합성한 후 slip casting방법과 냉간정수압성형에 의하여 tube와 disk형을 각각 제작하였다. Slip casting은 40 wt%의 고체함량을 가지는 슬러리를 사용해 알루미나 몰드에서 이루어졌고 냉간정수압성형은 20 MPa의 압력하에서 수행되었다. 성형체들은 $1600^{\circ}C$, $1700^{\circ}C$, $1750^{\circ}C$에서 각각 소결하여 성형방법에 따른 상관계와 소결밀도를 조사하였다. 냉간정수압성형에 의한 시편이 $1700^{\circ}C$까지 ${\beta}"-Al_2O_3$의 상분율이 월등히 높은 반면, 소결밀도에 있어서는 slip casting방법의 경우가 다소 높았다. 소결 시 상대밀도는 $1750^{\circ}C$에서 1 h 경과 후, 두 경우 모두 약 83%를 나타내었다. 90 min 이상 소결하였을 때는 입자의 과대성장과 기공으로 인해 오히려 밀도가 낮아졌다.

• 한국재료학회지
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• 제22권2호
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• pp.61-65
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• 2012

A $Li_2O-2SiO_2$ ($LS_2$) glass was investigated as a lithium-ion conducting oxide glass, which is applicable to a fast ionic conductor even at low temperature due to its high mechanical strength and chemical stability. The $Li_2O-2SiO_2$ glass is likely to be broken into small pieces when quenched; thus, it is difficult to fabricate a specifically sized sample. The production of properly sized glass samples is necessary for device applications. In this study, we applied spark plasma sintering (SPS) to fabricate $LS_2$ glass samples which have a particular size as well as high transparency. The sintered samples, $15mm\phi{\times}2mmT$ in size, ($LS_2$-s) were produced by SPS between $480^{\circ}C$ and $500^{\circ}C$ at 45MPa for 3~5mim, after which the thermal and dielectric properties of the $LS_2$-s samples were compared with those of quenched glass ($LS_2$-q) samples. Thermal behavior, crystalline structure, and electrical conductivity of both samples were analyzed by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and an impedance/gain-phase analyzer, respectively. The results showed that the $LS_2$-s had an amorphous structure, like the $LS_2$-q sample, and that both samples took on the lithium disilicate structure after the heat treatment at $800^{\circ}C$. We observed similar dielectric peaks in both of the samples between room temperature and $700^{\circ}C$. The DC activation energies of the $LS_2$-q and $LS_2$-s samples were $0.48{\pm}0.05eV$ and $0.66{\pm}0.04eV$, while the AC activation energies were $0.48{\pm}0.05eV$ and $0.68{\pm}0.04eV$, respectively.

• 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.

• 한국산학기술학회논문지
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• 제18권6호
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• pp.37-43
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• 2017

본 논문에서는 고출력 전자기파 (Electromagnetic pulses, EMP) 영향에 의해 발생하는 반도체 부품의 물리적 상호작용에 대한 원리와 고장 발생 메커니즘의 연구를 위해 선행된 연구 내용을 고찰하였다. 반도체 부품에서의 전자기파 전이 과정은 3층 (공기/유전체/도체) 구조로 설명할 수 있으며, 복소반사계수에 의하여 이론적으로 흡수되는 에너지를 예상할 수 있다. 반도체 부품에 전달된 과도한 고출력 전자기파로 인한 반도체 부품의 주요 고장 원인은 전자기파 커플링에 의한 부품 소재의 줄 열에너지의 발생이다. 전기장에 의한 유전가열과 자기장에 의한 맴돌이손실에 의해 반도체 칩의 P-N 접합 파괴, 회로패턴의 burn-out과 리드 프레임과 칩을 연결하는 와이어의 손상 등이 발생한다. 즉, 반도체 부품에 전달된 전자기파는 반도체 내부 물질과 상호작용을 하며, 쌍극자분극과 이온 전도도 현상이 동시에 발생하여, 칩 내부의 P-N 접합 부분에 과도한 역전압이 형성되어 P-N 접합 파괴를 유발한다. 향후 고 신뢰성을 요구하는 전기전자시스템에 대한 EMP 내성을 향상하기 위한 반도체 부품 수준의 연구가 필요하다.

• 한국세라믹학회지
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• 제44권12호
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• pp.740-746
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• 2007

The potential candidates for IT-SOFCs cathode materials, $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ (BSCF) and $La_{0.6}Ba_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LBCF) powders, were synthesized by a EDTA-citrate combined method from $Sr(NO_3)_2$, $Ba(NO_3)_2$, $La(NO_3)_3{\cdot}6H_2O$, $Co(NO_3)_2{\cdot}6H_2O$, $Fe(NO_3)_3{\cdot}9H_2O$, citric acid and $EDTA-NH_3$. The cathode performance of symmetrical electrochemical cells consisting of BSCF-GDC or LBCF-GDC composite electrodes and a GDC electrolyte was investigated using by AC impedance spectroscopy at the temperature range of 500 to $700^{\circ}C$. It was found that a single phase perovskite could be successfully synthesized when the precursor is heated at $850^{\circ}C$ for 2 h. Due to thermal expansion mismatch between BSCF and GDC, the composite cathodes with lower GDC content than 45 wt% were peeled off from the GDC electrolyte and their electrode polarization resistance was estimated to be high. The thermal expansion coefficient of BSCF-GDC composites was decreased with increasing the GDC content and the electrode peeling off did not occur in BSCF-45 and 55 wt% GDC composites. BSCF-45 wt% GDC composite electrode showed the lowest area specific resistances (ASR) of 0.15 and $0.04{\Omega}{\cdot}cm^2$ at 600 and $700^{\circ}C$, respectively. On the other hand, LBCF-GDC composite cathodes showed higher ASR than the BSCF-45 and 55 wt% GDC and their cathode performance were decreased with the GDC content.

• 전기화학회지
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• 제10권3호
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• pp.207-212
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• 2007

IT-SOFC(중저온형 고체산화물 연료전지)의 공기극으로 적합한 PSCF3737의 물질 특성을 파악하고 그 특성을 이용하여 낮은 ASR을 갖기 위한 소결 온도 및 두께 최적화에 관한 연구를 수행하였다. 분말 사이즈 및 상형성을 고려할 때 GNP 방법으로 합성된 분말의 하소 온도는 $1000^{\circ}C$가 적합함을 알 수 있었다. 산소 분압에 따른 ASR 변화 실험을 통하여 PSCF3737의 저항 성분을 전극 자체의 특성과 관련된 중간 주파수 대역(${\sim}10^2Hz$)과 산소의 확산에 영향 받는 낮은 주파수 대역(${\sim}10^{-1}Hz$) 2가지로 분류할 수 있었다. 공기극의 특성 실험을 통하여 소결 온도는 $1200^{\circ}C$가 가장 적합하며 공기극의 두께는 2번 스크린 프린팅 된 $27\;{\mu}m$가 가장 적합함을 알 수 있었다. 이를 토대로 EIS 측정을 하면 $700^{\circ}C$에서 $0.115\;{\Omega}cm^2$의 낮은 ASR값을 얻을 수 있었다.

• 대한화학회지
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• 제35권6호
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• pp.625-629
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• 1991

Lead Oxide를 2.5, 5.0, 7.5 및 10.0 mol%를 함유하는 Niobium Oxide-Lead Oxide계의 전기전도도를 2.0${\times}$$10^{-1}$${\sim}$1.0${\times}$$10^{-5}$ atm의 산소 부분압력하에서 700${\sim}$$1100^{\circ}C$의 온도에서 측정하였다. 본 계의 전기전도도는 PbO mol%가 증가함에 따라 감소하며 $10^{-5}$${\sim}$$10^{-1}$ $ohm^{-1}$ $cm^{-1}$ 범위에서 변하였다. 전기전도도의 활성화에너지는 약 1.70 eV이다. 전기전도도의 산소 부분압력 의존성은 높은 산소 부분압력에서는 이온 및 전자 전도성을 가진 혼합 전도체이고 낮은 산소 부분압력에서는 산소 부분압력의 -1/4승에 비례하는 의존성을 가진 n-type 전자 전도성을 나타내고 있다. 그 계의 결합구조와 전기전도 메카니즘을 얻어진 데이타와 관련시켜 논의하였다.