• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1181-1186
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• 2003

Chemical Mechanical Polishing (CMP) is an essential dielectric planarization in multilayer microelectronic device fabrication. In the CMP process, it is necessary to minimize the extent of surface defect formation while maintaining good planarity and optimal material removal rates. The polishing mechanism of W-CMP process has been reported as the repeated process of passive layer formation by oxidizer and abrasion action by slurry abrasives. Thus, it is important to understand the effect of oxidizer on W passivation layer, in order to obtain higher removal rate (RR) and very low non-uniformity (NU %) during W-CMP process. In this paper, we compared the effects of oxidizer or W-CMP process with three different kind of oxidizers with 5 wt% hydrogen peroxide such as Fe(NO$_3$)$_3$, H$_2$O$_2$, and KIO$_3$. The difference in removal rate and roughness of W in stable and unstable slurries are believed to caused by modification in the mechanical behavior of Al$_2$O$_3$ particles in presence of surfactant stabilizing the slurry.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.151-151
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• 2010

In this paper, the electrically properties of nonvolatile memory (NVM) using multi-stacks gate insulators of oxide-nitride-oxynitride (ONOn) and active layer of the low temperature polycrystalline silicon (LTPS) were investigated. From hydrogenated amorphous silicon (a-Si:H), the LTPS thin films with high crystalline fraction of 96% and low surface's roughness of 1.28 nm were fabricated by the metal induced crystallization (MIC) with annealing conditions of $650^{\circ}C$ for 5 hours on glass substrates. The LTPS thin film transistor (TFT) or the NVM obtains a field effect mobility of ($\mu_{FE}$) $10\;cm^2/V{\cdot}s$, threshold voltage ($V_{TH}$) of -3.5V. The results demonstrated that the NVM has a memory window of 1.6 V with a programming and erasing (P/E) voltage of -14 V and 14 V in 1 ms. Moreover, retention properties of the memory was determined exceed 80% after 10 years. Therefore, the LTPS fabricated by the MIC became a potential material for NVM application which employed for the system integration of the panel display.

• 열처리공학회지
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• 제19권2호
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• pp.90-95
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• 2006

Nitriding or carburizing of carbon steels results in good mechanical properties such as high surface hardness and wear resistance but it has no affection on the corrosion resistance. Corrosion properties of nitriding and carburizing steels could be deteriorated. So, recently, there have been great demand for oxi-nitriding to enhance both mechanical properties and corrosion resistance. In this study, the corrosion resistance of carbon steel, S35C, and free cutting steel, SUM222, are prepared by vacuum nitriding and vacuum post-oxidation were compared with those treated by nitriding. After vacuum post-oxidation, $5{\mu}m$ oxide layer was formed on the nitride layer with $20{\sim}30{\mu}m$ depth. Potentio-dynamic polarization curve in corrosion test showed that the corrosion potential after post oxidation was increased from 200 mV to 800 mV in S35C and from 600 mV to 1200 mV in SUM222. SEM analyses showed that pores was increased and surface roughness became rougher with post oxidation. However, the formation of $Fe_3O_4$ resulted in the enhanced corrosion resistance of steels.

• Advances in nano research
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• 제8권1호
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• pp.69-82
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• 2020

In this study, the free and forced vibration analysis of micro sandwich plate with porous core layer and magneto-electric face sheets based on modified couple stress theory and first order shear deformation theory under simply supported boundary conditions is illustrated. It is noted that the core layer is composed from balsa wood and also piezo magneto-electric facesheets are made of BiTiO₃-CoFe₂O₄. Using Hamilton's principle, the equations of motion for micro sandwich plate are obtained. Also, the Navier's method for simply support boundary condition is used to solve these equations. The effects of applied voltage, magnetic field, length to width ratio, thickness of porous to micro plate thickness ratio, type of porous, coefficient of porous on the frequency ratio are investigated. The numerical results indicate that with increasing of the porous coefficient, the non-dimensional frequency increases. Also, with an increase in the electric potential, the non-dimensional frequency decreases, while and with increasing of the magnetic potential is vice versa.

• 한국자기학회지
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• 제12권3호
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• pp.103-108
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• 2002

나노옥사이드(nato-oxide layer, NOL) 층이 고정층에 첨가된 스펙큘라 스핀밸브(specular spin valve)와 NOL이 없는 기본 스핀 밸브를 UHV 스퍼터 시스템에서 FeMn 반강자성층을 사용하여 탑 및 바텀 형 스핀밸브를 제조하였으며, 제조한 시료의 열처리 온도에 따른 자기저항 특성 및 교환바이어스 특성을 비교 분석하였다. 탑 형 스핀밸브에서는 NOL이 있는 경우 25$0^{\circ}C$ 열처리에서 9.2%의 자기저항비를 얻을 수 있었으며, 바텀 형 스핀밸브에서는 25$0^{\circ}C$ 열처리에서 10.1%의 자기저항비를 얻을 수 있었다. 따라서 바텀 형 스핀밸브가 탑 형 스핀밸브보다 고정층에 첨가된 NOL의 스펙큘라 반사 효과가 높아 자기저항비가 증가함을 확인하였다. 또한 바텀 형 스핀밸브에서 25$0^{\circ}C$ 이상의 열처리시 NOL이 있는 경우가 NOL이 없는 경우보다 28 % 이상의 교환바이어스 증가를 보였다. 이와 같은 원인은 NOL이 첨가된 고정층의 자기모멘트의 감소와 X-선 회절 분석 결과로부터 NOL의 첨가에 따른 강화된 (111) FeMn집합조직 때문이라고 판단된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.230-233
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• 2008

The vanadium rich ash of petroleum coke can give a slagging problem during because of the high melting point of $V_2O_3$. For continuous removal of the slag, petroleum coke is often mixed with coal, and the viscosity of the mixed slag is an important property, determining the gasification temperature. The viscosities of the mixed slag from various mixing ratios of petroleum coke and a bituminous coal were investigated. When mixed with a crystalline coal slag, $T_{cv}$ was increased at a higher the coke content in the mixed feed. When the $V_2O_3$ concentration was greater than 4.5%, it was difficult to get accurate measurements of $T_{cv}$. The SEM/EDX analyses of the cooled slag revealed that the major crystalline phase was anorthite, and $T_{cv}$ should be related to the formation temperature of anorthite. The SEM/EDX analyses also showed that, at low concentrations of vanadium, part vanadium formed a crystalline phase with Al-Si-Ca-Fe, and the rest remained in the glassy phase, suggesting that vanadium existed as a slag component at the low viscosity region. At a high concentration, vanadium forms a phase with Ca, and the Ca-V phase was separated from the slag phase, and formed a layer above the slag. FeO in petroleum coke also played an important role determining viscosity: at high temperatures, increased FeO lowered the viscosity, but as it formed a spinel phase, the depletion of FeO in the slag resulted in a higher viscosity.

• 한국지형학회지
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• 제23권2호
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• pp.29-45
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• 2016

Chemical composition of fine sediments from Jeongdongjin area are analyzed with XRF method. The results are compared with previously reported results of sandstones of the nearest Simgok port. The weight percentage of $SiO_2$ of the samples are far lower than those of sandstones of Simgok. It is supposed to be happened by the selective elution of $SiO_2$ from the sediment layer of coastal terrace, as there's no evidence of selective input or precipitation of other elements from outside. As a result of chemical alteration or weathering of sediment at coastal terrace, weight percentage of $Al_2O_3$ and $Fe_2O_3$ of samples show far higher values than those of Simgok sandstone. In addition, the relative portion of $Al_2O_3$ and $Fe_2O_3$ are decreased to upward within outcrop of terrace sediment layers. It could be caused by the chemical weathering progress with time. However Chemical Index of alteration(CIA) of sediment samples are no larger than 90 and it could be interpreted that it would take over 100ka for total weathering of sediment in this area. Meanwhile the ratio of $SiO_2/Al2O_3$ of terrace sediment showed as 3.48~6.0 and it is far smaller than those of Simgok sandstones(23.9~49.0). The ratio of $SiO_2/Fe_2O_3$ of terrace sediment(19.19~55.85) showed similar pattern with $SiO_2/Al2O_3$ (Simgok sanstone: 119.6~601.8). The ratios have a weak trend of decreasing upwards within the outcrop, there also a huge difference in value among the samples. Chemical composition of reddish brown and gray layers which suspected as the result of psudogleization reveals that reddish brown parts have higher concentration of $Fe_2O_3$ than other parts, while there was no significant difference in concentration of $Al_2O_3$ and CaO.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 추계학술대회 논문집
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• pp.291-292
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• 2015

Duplex Stainless Steel의 Plasma Nitriding 처리 시 가스량과 처리온도가 표면 특성에 미치는 영향을 조사하였다. $N_2$함량 및 처리 온도가 각각 10%에서 25%로 $400^{\circ}C$에서 $430^{\circ}C$로 증가함에 따라서 질소가 과고용된 S-phase의 두께 및 표면 경도가 증가하였으나, 내부 식성은 $Cr_2N$ 및 $(Fe,Cr)_4N$이 석출하여 감소하였다. 질소를 10%로 고정하고 $CH_4$함량을 증가시키면 1%일 때 S-phase의 두께가 최대가 되며 그이후로 감소하였다. 처리온도 $400^{\circ}C$일 때 질소함량이 10%, $CH_4$ 함량이 5%일 경우 내식성이 모재보다 증가하였다.

• 박물관보존과학
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• 제23권
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• pp.71-90
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• 2020

전쟁기념관에서 소장하고 있는 등록문화재 제666호 F-51D 무스탕 전투기의 과학적 분석을 진행하였다. F-51D 무스탕 전투기는 1950년 6월 25일 전쟁이 발발하자, 7월 2일 우리 공군이 미국으로부터 인수해 최초로 운용한 전투기이다. 전쟁기간 동안 북한군을 상대하여 괄목할 만한 작전을 펼친 한국 공군의 주력기이다. 본 연구 대상은 6·25전쟁 당시 직접 사용된 기체로 현재까지 과학적 조사·분석이 이루어지지 않았으며 차후 해체 및 복원을 계획하고 있다. 지속적인 옥외 전시로 인해 도료층 및 캐노피가 변색되었으며 도료의 박락 및 균열 또한 확인되었다. 비파괴 과학적 분석을 통해 대형유물의 해체 및 복원의 기초 자료로 활용하고자 한다. P-XRF를 사용하여 적색, 청색, 황색, 백색, 흑색, 회색을 중심으로 안료 성분 분석을 진행하였고, 전투기에 사용된 도료의 수지 성분을 확인하기 위해 적외선 분광 분석(FT-IR-ATR)을 하였다. 몸체, 날개, 꼬리날개에 사용된 금속의 성분 분석도 함께 진행하였다. 안료 성분 분석은 적색 산화철인 벵가(Fe₂O₃), 프탈로시아닌 블루계 등의 유기안료, 황색의 황연(PbCrO₄), 백색의 티타늄화이트(TiO₂), 흑색의 철흑(Fe₃O₄), 회색의 철흑(Fe₃O₄)+티타늄화이트(TiO₂)가 확인되었다. 전투기 외부 도장에 사용된 수지는 주로 Alkyd 수지를 사용한 것으로 확인되었으며 청색의 경우 Acryl 수지를 이용하여 도장 한 것으로 추정된다. 전투기 캐노피는 투명성과 내광성이 우수한 Poly methyl methacrylate(PMMA)로 확인되었다. 전투기 몸체, 날개, 꼬리날개에서 모두 알루미늄(Al)이 주성분으로 검출되었다. 꼬리날개부 후면부의 경우 철-아연 도금(함석)이 사용된 것을 보아 과거 복원부인 것으로 판단되었다.

• 소성∙가공
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• 제20권2호
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• pp.140-145
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• 2011

The aim of the present study is to derive optimized post heat treatment temperatures to get a proper formability for Ti/STS409L/Ti clad materials. These clad materials were fabricated by cold rolling followed by a post heat treatment process for 10 minutes at temperatures ranging from $500^{\circ}C$ to $850^{\circ}C$. The microstructure of the interface was observed using a Scanning Electron Microscope(SEM) and an Energy Dispersive X-ray Analyser(EDX) in order to investigate the effects of post heat treatment on the bonding properties of the Ti/STS409L/Ti clad materials. Diffusion bonding was observed at the interfaces with a diffusion layer thickness increasing with the post heat treatment temperature. The diffusion layer was composed of a type of(${\varepsilon}+{\zeta}$) intermetallic compound containing additional elements, namely, Fe, Ti and Ni. The micro Knoop hardness of the Ti/STS409L interfaces was found to increase with heat treatment up to $800^{\circ}C$ and then decrease for temperatures rising up to $850^{\circ}C$. The tensile strength was shown to decrease for heat treatment temperature increasing to $750^{\circ}C$ and then increase rapidly for temperature rising up to $850^{\circ}C$. A post heat treatment temperature range of $700{\sim}750^{\circ}C$ was found to optimize the formability of Ti/STS409L/Ti clad materials.