• 한국재료학회지
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• 제15권3호
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• pp.155-160
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• 2005

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which results in a chemically aggressive environment that is very corrosive fir typical structural materials. So, it is essential to choose the optimum material f3r the process equipment handling molten salt. In this study, the corrosion behavior of Al-Y coated Haynes 263 in a molten salt of $LiCl-Li_2O$ under oxidation atmosphere was investigated at $650^{\circ}C$ for $72\~168$ hours. The corrosion rate of Al-Y coated Haynes 263 was low while that of bare Haynes 263 was high in a molten salt of $LiCl-Li_2O$. Al-Y coated Haynes 263 improved the corrosion resistance better than bare Haynes 263 alloy. An Al oxide layer acts as a protective film which Prohibits Penetration of oxygen. Corrosion Products were formed $Li(Ni,Co)O_2$ and $LiTiO_2$ on bare Haynes 263, but $LiAlO_2,\;Li_5Fe_5O_8\;and\;LiTiO_2$ on Al-Y coated Haynes 263.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.179-179
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• 2008

$BaTiO_3$를 기본조성으로 하는 PTC 써미스터는 Curie 온도이상에서 저항이 급격히 상승하는 산화물 반도체 세라믹이다. 이러한 성질을 이용하여 degaussing 소자, 정온 발열체, 온도센서, 전류 제한소자 등 상업적으로 여러 분야에서 연구되고 있다. 또한 원가절감 등을 위하여 Ni 내부전극을 사용하여 환원 분위기에서 소결하는 칩 타입에 대한 연구가 진행되고 있다. 본 연구에서는 Sm 함량(0.1at%~1.0at%)을 달리한 $BaTiO_3$(Si, Mn, Ca) 계를 선택하여 3%$H_2/N_2$ 분위기에서 1200~$1260^{\circ}C$, 2h 소결한 후 공기 중에서 재산화 처리하고 재산화 시간에 따른 PTC 특성 변화에 대하여 고찰하였다. 재산화 온도와 시간은 각각 $800^{\circ}C$와 0.5h~10h으로 하였다. Sm 함량을 달리하여 환원 분위기에서 소결한 시편의 미세구조와 PTC 특성과의 상관관계를 관찰한 결과, 소결온도가 낮을수록 PTC 특성은 좋아졌으며, 상온 비저항은 Sm 함량이 높아질수록 낮아졌다. 또한 Sm 함량이 높아질수록 jumping ratio$(R_{max}/R_{25^{\circ}C})$는 낮아졌다. 재산화 시간에 따른 PTC 특성은 다소 떨어졌지만 소결온도에 따라 달리 나타났다. Jumping ratio$(R_{max}/R_{25^{\circ}C})$는 Sm을 0.7 at% 첨가한 계에서 재산화를 1시간 처리한 시편에서 가장 우수하였다.

• 한국표면공학회지
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• 제32권2호
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• pp.144-156
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• 1999

Thermal Barrier Coating with Functional Gradient Materials (FGM-TBC) can play an important role to protect the parts from harmful environments in high temperatures such as oxidation, corrosion, and wear and to improve the efficiency of aircraft engine by lowering the surface temperature on turbine blade. FGM-TBC can increase the life spans of product and improve the operating properties. Therfore, in this study the evaluations of mechanical and thermal properties of FGM-TBC such as fatigue, oxidation and wear-resistance at high temperatures have been conducted. The samples of both the TBC with 2, 3, 5 layers (YSZ/NiCrAlY) to be produced by Air Plasma Spray method (APS) and the bulk TBC with 6 layers to be produced by Plasma Assisted Sintering method (PAS) were used. Furthermore, residual stress, bond strength, and thermal conductivity were evaluated. The average thickness of the APS was 500$\mu\textrm{m}$ to 600$\mu\textrm{m}$ and the average thickness of the PAS was 3mm. The hardness number of the top layer of APS was 750 Hv to 810Hv and that of PAS was 950 Hv to 1440Hv. The $ZrO_2$ coating layer of APS was composed of tetragonal structure after spraying as the result of XRD analysis. As shown in the results of the high temperature wear test, the 3 layer coating of APS had the best wear resistance at $800^{\circ}C$ and the 5 layer coating of APS had the best wear resistance at $600^{\circ}C$. But, these coatings had the tendency of the low-temperature softening at $300^{\circ}C$. The main mechanism of wear was the adhesive wear and the friction coefficient of coatings was increased as increasing the test temperatures. A s results of thermal conductivity test, the ${\Delta}T$ of the APS coating was increased as number of layer and the range of thermal conductivity of the PAS was $800^{\circ}C$ to $1000^{\circ}C$.

• 대한안전경영과학회지
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• 제9권6호
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• pp.197-204
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• 2007

Ceramic pigments were developed by using 4 kinds of Brass scraps. Each Brass scraps were mixed with same weight-ratio of Husk ash, and fine-ground by Rotate ring mill(RRG-120, Armstech industrial. co. Ltd, Korea) after firing at $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. As a result, analysis of particle size of synthetic pigments by particle size analyser, they are $3{\mu}m$ as average. The resulting pigments were characterized by using XRD, FT-IR, SEM Structure of the crystals are Zn2SiO4,, and ZnO, Cu2O, CuO, and cristobalite are existed and particles' shape are plate or needle. As a result of analysis of chemical composition by XRF, synthetic pigments have high SiO2 and CuO content and have SnO2, ZnO and NiO, too. 1wt%, 3wt% and 5wt% pigments were added in each lime glaze, lime-barium glaze and lime-magnesia glaze, and fired at oxidation and reducing atmosphere to figure hue in glazes out. As a result of analysis of color, chroma and brightness by UV, colors of glazes fired at oxidation atmosphere turned into green from sky blue, and colors of glazes fired at reducing atmosphere turned into pink and red.

• 자원환경지질
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• 제8권4호
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• pp.175-182
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• 1975

본 연구는 양양(襄陽) 철광산(鐵鑛山) 의 철(鐵)을 부존(賦存)하고 있는 각섬석질암(角閃石質岩)의 성인(成因) 규명을 목적으로, 습식(濕式) 및 방출분광분석적(方出分光分析的) 방법을 통하여 얻은 18개의 주성분(主成分) 및 희유성분(稀有成分)의 data를 각종 Niggli 도표에 적용시키고 variaticn trend를 검토한 결과이다. 지금까지의 각 대륙(大陸)에 분포하는 각섬석질암(角閃石質岩)의 화학적(化學的)인 연구결과로는 거의 모든 각섬석질암이 변성퇴적암류(變成堆積岩類)의 형태로 산출될지라도 화성기원(火成起源)으로 밝혀져 왔으나 양양(襄陽) 철광산(鐵鑛山)의 함철(含鐵) 각섬석질암(角閃石質岩)은 준일각섬석질암(準一角閃石質岩), 특히 pelite-carbonate mixture의 특성(特性)을 뚜렷하게 보여준다. 즉 Niggli 값을 사용한 각 도면에서 본 연구의 대상이 된 시료들은 분산(分散)된 분포(分布) 및 퇴적(堆積)영역, 특히 pelite-carbonate mixture의 trend를 잘 따르고, Cr, Co 및 Ni의 함량이 매우 낮으며 Cr/mg, Co/mg 도포에서퇴적기원(堆積起源)의 특정인 negative trend를 뚜렷하게 나타낸다. 한편 높은 oxidation ratio의 값(>30)은 상기(上記) 결과를 더욱 뒷바침해준다. 이러한 모든 현상은 경기변성대(京畿變成帶)에서 퇴적기원(堆積起源)으로 판명된 준일각섬석질암(準一角閃石質岩)(소칠섭(蘇七燮), 1974) 이 갖는 특성과 유사하다.

• 대한화학회지
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• 제44권4호
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• pp.322-327
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• 2000

산성 $K_2Cr_2O_7$ 용액 자체의 흡광도를 측정하는 기존의 분석법과는 달리 산성 $K_2Cr_2O_7$ 용액 속에 존재하는 $HCrO_4^-$ 이온과 과산화수소($H_2O_2$)의 산화-원반응의생성물인 진한 푸른색의 $CrO(O_2)_2$의 흡광도를 측정하는 분석법에 흐름주입분석기법을 접목한 새로운 흡구분광분석법을 개발하였다. 새로운 흡수분광분석법은 넓은 분석농도범위($2.0 {\times}10^{-6}$M~$8.0 {\times}10^{-3}$M)에 걸쳐 Beer의 법칙을 정확히 따르는 $K_2Cr_2O_7$용액의 검정선의 작성이 가능하였다. 새로운 흡수분광분석법은 기존의 흡수분광법에 비해 약 2.2배 가량 더 높은 감도을 보이며, Cu를 제외한 V, Co, Ni,Fe, 그리고 Mn가 같은 물질들에 의한 간섭현상도 거의 무시할 수 있다는 장점을 가진다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.100-105
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• 2003

25Cr-20Ni series strainless steel have an excellent high temperature strength, high oxidation and high corrosion resistance. However, further improvement can be creep strength by work hardening prior creep. In the present study, the effect of prestraining at room temperature on the creep behavior of a Class M(STS310S) and a Class A(STS310J1TB) alloy containing precipitates have been examined. Prestraining was carried out at room temperature and range of prestrain was $0.5{\sim}2.5$ % at STS310J1TB and $2.0{\sim}7.0$ % at STS310S. Creep behavior and creep rate of pre-strained specimens were compared with that of virgin specimens. Room temperature prestraining produced the creep life that is longer than that of a virgin specimen both for STS310J1TB and STS310S when creep test carried out at the temperature lower than recrystallization temperature. The reason for this improvement of creep life was ascribable to the interaction between dislocations and precipitates in addition to the dislocation-dislocation interaction in STS310J1TB and the dislocation-dislocation interaction in STS310S. The beneficial effect of prestraining in STS310J1TB was larger than that of STS310S.

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.416-423
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• 2019

A novel non-enzymatic oxalic acid (OA) sensor based on the platinum/carbon black-nickel-reduced graphene oxide (Pt/CBNi-rGO) nanocomposite is reported. The nanocomposites were prepared by the ethylene glycol reduction method. Their morphology and chemical composition were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results clearly demonstrated the formation of the Pt/CB-Ni-rGO nanocomposite. The electrocatalytic activity of the Pt/CB-Ni-rGO electrode was investigated by cyclic voltammetry. It was determined that the appropriate amount of Pt enhanced the catalytic activity of Pt for oxalic acid electro-oxidation. Moreover, the modified electrode was determined to be highly selective for oxalic acid without interference from compounds commonly found in urine including uric acid and ascorbic acid. The chronoamperometric signal gave a wide linearity range of 20 μM-60 mM and the detection limit (3σ) was found to be 2.35 μM. The proposed method showed high selectivity, stability, and good reproducibility and could be used with micro-volumes of sample for the detection of oxalic acid. Finally, the oxalic acid content in artificial and control urine samples were successfully determined by our proposed electrode.

• 한국자기학회지
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• 제10권3호
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• pp.118-122
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• 2000

절연층으로 $Al_2$ $O_3$를 사용한 스핀의존성 터널링 접합에서 절연층의 두께가 자기저항특성에 미치는 효과에 대해 조사하였다. 스핀 의존성 터널링 접합은 3-gun 스퍼터링 시스템에서 4$^{\circ}$tilt-cut (111)Si 기판 위에 증착하였다. 절연층으로 사용된 $Al_2$ $O_3$는 Al을 1~3 nm로 증착한 후에 대기중에서 자연산화시켜 얻었고, 상부와 하부 강자성체 전극은 NiFe와 Co를 사용하였다. 자기저항비는 절연층의 두께가 2 nm인 터널링 접합에서 약 14 %로 최대값을 보였고 접합에 걸리는 터널링 전압이 증가함에 따라 최대 자기저항비는 급격히 감소하는 경향을 보였다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3695-3702
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• 2013

A nickel(II) complex $[Ni(H_2biim)_2(H_2O)_2](ClO_4)_2{\cdot}H_2O$ (1) of biimidazole ligand has been synthesized and characterized (Where $H_2biim$ = 2,2'-biimidazole). The single crystal X-ray diffraction of the complex shows a dimeric structure with six coordinated psudo-octahedral geometry. The cyclic voltammograms of complex exhibited one quasireversible reduction wave ($E_{pc}=-0.61V$) and an irreversible oxidation wave ($E_{pa}=1.28V$) in DMF solution. The interaction of the complex with Calf-Thymus DNA (CT-DNA) has been investigated by absorption and fluorescence spectroscopy. The complex is an avid DNA binder with a binding constant value of $1.03{\times}10^5M^{-1}$. The results suggest that the nickel(II) complex bind to CT-DNA via intercalative mode and can quench the fluorescence intensity of EB bind to CT-DNA with $K_{app}$ value of $3.2{\times}10^5M^{-1}$. The complex also shown efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of hydrogen peroxide as oxidizing agent. The DNA cleavage by complex in presence of quenchers; viz. DMSO, KI, $NaN_3$ and EDTA reveals that hydroxyl radical or singlet oxygen mechanism is involved. The complex showed invitro antimicrobial activity against four bacteria and two fungi. The antimicrobial activity was nearer to that of standard drugs and greater than that of the free ligand.