• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.36-40
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• 2018

In this study, the electromechanical properties in Sn-Cu double layer stabilized GdBCO coated conductor (CC) tapes with and without external lamination under uniaxial tension were examined at 77 K and self-field. Their irreversible stress and strain limits were determined using a loading-unloading scheme based on different critical current ($I_c$) recovery criteria. The repeated tests were performed and statistical estimation was done to check the reproducibility depending on the criterion adopted in evaluating the electromechanical properties. From the results, it showed that the Sn-Cu double-layer stabilized CC tapes have the higher irreversible stress limit, but lower irreversible strain limit as compared to brass laminated ones. Through the repeated tests, it can be found that a small scattering of irreversible limits existed in both CC tape samples. Finally, similar strain sensitivity of $I_c$ in both CC tapes was obtained.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 추계학술발표회 초록집
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• pp.69-69
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• 2001

We report a study of the nitriding of the martensitic grade of stainless steel AKSK 420 in a low-pressure rl discharge using pure nitrogen. Much studied samples of the austenitic grade AISI 304 were treated at the same time to provide a comparison. With a treatment time of 4.0 h at $400^{\circ}C$, the nitrogen-rich layer on MSK 420 is 20pm thick and has a hardness about 4.3 times higher than that of the untreated material. The layer thickness is much greater than that obtained on AISI 304 under identical treatment conditions, reflecting the different Cr content of the two alloys. The alloy AlISI 420 is more susceptible than AISI 304 to the formation of CrN and ferrite, and this has a deleterious effect on the hardnes, gain. Below the temperature at which CrN forms, the treated layer retains its martensitic structure, but with a larger lattice parameter than the bulk, a phase that we term expanded martensite, by analogy with the situation with austenitic stainless steel. The fact that the treated layer retains a martensitic structure is interesting in view of previous evidence that nitrogen is an austenite stabilizer.

• Journal of Electrochemical Science and Technology
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• 제14권3호
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• pp.231-242
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• 2023

Li₂O-based cathodes utilizing oxide-peroxide conversion are innovative next-generation cathodes that have the potential to surpass the capacity of current commercial cathodes. However, these cathodes are exposed to severe cathode-electrolyte side reactions owing to the formation of highly reactive superoxides (O^x-, 1 ≤ x < 2) from O^2- ions in the Li₂O structure during charging. Succinonitrile (SN) has been used as a stabilizer at the cathode/electrolyte interface to mitigate cathode-electrolyte side reactions. SN forms a protective layer through decomposition during cycling, potentially reducing unwanted side reactions at the interface. In this study, a composite of Li₂O and Ni-embedded reduced graphene oxide (LNGO) was used as the Li₂O-based cathode. The addition of SN effectively thinned the interfacial layer formed during cycling. The presence of a N-derived layer resulting from the decomposition of SN was observed after cycling, potentially suppressing the formation of undesirable reaction products and the growth of the interfacial layer. The cell with the SN additive exhibited an enhanced electrochemical performance, including increased usable capacity and improved cyclic performance. The results confirm that incorporating the SN additive effectively stabilizes the cathode-electrolyte interface in Li₂O-based cathodes.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.50-53
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• 2023

In this study, the photolithography process was chosen to reduce the aspect ratio of the cross-section of a high-temperature superconducting (HTS) tape by dividing the superconducting layer of the tape. Reducing the aspect ratio decreases the magnetization losses in the second-generation HTS tapes generated by AC magnetic fields. The HTS tape used in the experiment has a thin silver (Ag) layer of about 2 ㎛ on top of the REBCO superconducting layer and no additional stabilizer layer. A dry film resist (DFR) was laminated on top of the HTS tape by a lamination method for the segmentation. Exposure to a 395 nm UV lamp on a patterned mask cures the DFR. Dipping with a 1% Na₂CO₃ solution was followed to develop the uncured film side and to obtain the required pattern. The silver and superconducting layers of the REBCO films were cleaned with an acid solution after the etching. Finally, the segmented HTS tape was completed by stripping the DFR film with acetone.

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.40-45
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• 2022

The electrical/thermal stabilities and magnetic field controllability of a no-insulation (NI) high-temperature superconducting magnet are characterized by contact resistance between turn-to-turn layers, and the contact resistance characteristics are determined by properties of conductor surface and winding tension. In order to accurately predict the electromagnetic characteristics of the NI coil in a design stage, it is necessary to control the contact resistance characteristics within the design target parameters. In this paper, the contact resistance and critical current characteristics of a rare-earth barium copper oxide (REBCO) conductor were measured to analyze the effects of surface treatment conditions (roughness and oxidation level) of the copper stabilizer layer in REBCO conductor. The test samples with different surface roughness and oxidation levels were fabricated and conductor surface analysis was performed using scanning electron microscope, alpha step surface profiler and energy dispersive X-ray spectroscopy. Moreover, the contact resistance and critical current characteristics of the samples were measured using the four-terminal method in a liquid nitrogen impregnated cooling environment. Compared with as-received REBCO conductor sample, the contact resistance values of the REBCO conductors, which were post-treated by the scratch and oxidation of the surface of the copper stabilizer layer, tended to increase, and the critical current values were decreased under certain roughness and oxidation conditions.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.263-270
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• 1999

In country, for 2002 World-cup the peak is to construct soccer playground. the stabilizing method by additives is mainly applied of permanent improvement for bearing capacity of structure foundation and for strength, durability and transformation of road pavement layer except for construction machine's trafficability and bearing capacity. This study is on soft ground improvement of $\bigcirc$$\bigcirc$ world-cup stadium field. construction field constitutes of very various layers and after construction the lawn grass should be planted on the surface of the earth and in addition, chemical effects should be limited from improved ground layer. Mixing soft clay in field with three domestic representative additives, it evaluated the unconfined compression strength. In the results, after curing during 28 days the objective strength has been obtained on about 5% combination ratio.

• 한국도로학회논문집
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• 제10권3호
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• pp.57-68
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• 2008

하부구조 안정처리 기법은 도로포장의 공용성을 증대시킬 뿐만 아니라 상부 포장층의 두께 절감할 수 있는 효과가 있다. 하부구조의 지반재료에 적절한 종류의 안정제를 배합함으로써 새로운 형태의 공학적인 지반재료를 구성하여 구조적 및 경제적으로 효과적인 층 구조를 형성하게 할 수 있다. 기존에는 안정처리기법을 경험에 근거하여 적용하여 왔으며 또한 설계시 본 기법을 적용할 수 있는 기준이 정립되어 있지 않다. 본 논문의 목적은 도로하부 지반재료에 적용을 위한 안정처리제의 역학적 특성을 평가하여 최적의 함량을 결정하고자 한다. 국내 포장하부구조의 대부분을 차지하고 있는 조립질 지반을 선정하여 안정제 혼합시 강도 및 변형특성을 일축압축실험과 반복재하식 회복변형계수 실내실험을 통하여 각각 알아보았다. 일축압축 실험결과, 안정제를 사용한 안정처리방법의 효과가 입도조정 안정처리 기법에 비하여 약 10배 이상의 일축압축강도가 증가 하는 것으로 나타났다. 또한 안정처리시 회복변형계수는 원시료와 비교하여 약 $6{\times}10$배 이상 증가하며, 체적응력과 축차응력 그리고 안정제의 함량이 커질수록 증가하는 경향을 나타내었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.243.1-243.1
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• 2011

We demonstrate a facile and robust layer-by-layer (LbL) assembly method for the fabrication of nonvolatile resistive switching memory (NRSM) devices based on superparamagnetic nanocomposite multilayers, which allows the highly enhanced magnetic and resistive switching memory properties as well as the dense and homogeneous adsorption of nanoparticles, via nucleophilic substitution reaction (NSR) in nonpolar solvent. Superparamagnetic iron oxide nanoparticles (MP) of about size 12 nm (or 7 nm) synthesized with oleic acid (OA) in nonpolar solvent could be converted into 2-bromo-2-methylpropionic acid (BMPA)-stabilized iron oxide nanoparticles (BMPA-MP) by stabilizer exchange without change of solvent polarity. In addition, bromo groups of BMPA-MP could be connected with highly branched amine groups of poly (amidoamine) dendrimer (PAMA) in ethanol by NSR of between bromo and amine groups. Based on these results, nanocomposite multilayers using LbL assembly could be fabricated in nonpolar solvent by NSR of between BMPA-MP and PAMA without any additional phase transfer of MP for conventional LbL assembly. These resulting superparamagnetic multilayers displayed highly improved magnetic and resistive switching memory properties in comparison with those of multilayers based on water-dispersible MP. Furthermore, NRSM devices, which were fabricated by LbL assembly method under atmospheric conditions, exhibited the outstanding performances such as long-term stability, fast switching speed and high ON/OFF ratio comparable to that of conventional inorganic NRSM devices produced by vacuum deposition.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.365-366
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• 2009

This study researched into the manufacture of current-limit module of using YBCO coated conductor. Regarding over-current of exceeding the critical current, the quench characteristics were researched according to the stabilizing layer through tendency in resistance, which is generated in conductor, by applying over-current to YBCO coated conductors, which have stabilizing layer. YBCO coated conductors, which were used in experiment, include one kind such as the conductor, which used stainless as the stabilizing layer. The critical current is 70 A. And, the critical temperature is with 90 K. First of all, the quench generation was researched under over-current of exceeding the critical current by using this YBCO coated conductors. The tendency of a rise in the detected voltage according to the applied current was measured. And, the tendency of a rise in resistance through voltage-current curve was measured. As a result, the point of time in thermal quench of conductor, which has stainless as the stabilizing layer, could be confirmed to be fast.

• 한국지반환경공학회 논문집
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• 제7권5호
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• pp.21-29
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• 2006

경량성토공법은 성토체 자중을 감소시켜 지반의 침하를 감소시키는 공법으로 작업의 편리성 등의 이유로 적용사례가 증가하고 있다. 이와 관련하여 스티로폼은 연약지반상에 경량성토재로서 활용할 수 있는 것으로 알려져 있다. 경량성토재로서 스티로폼의 사용은 응력증가를 최소화 할 수 있으며, 안정재 사용을 통하여 지지력 증대와 침하감소효과를 얻을 수 있다. 이에 본 연구에서는 연약점성토층 상부에 경량성토재를 포설하고 모형 지지력 실험과 유한요소해석을 실시하였으며, 그 결과를 바탕으로 경량성토재로서의 지지력 특성을 평가하였다. 실험결과 일반적인 성토재 보다 폐스티로폼을 이용한 성토재가 더욱 우수한 특성을 발휘하는 것으로 나타났다.