• 한국재료학회지
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• 제28권12호
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• pp.709-713
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• 2018

To improve the etch rate of $Si_3N_4$ thin film, $H_2SiF_6$ is added to increase etching rate by more than two times. $SiO_3H_2$ is gradually added to obtain a selectivity of 170: 1 at 600 ppm. Moreover, when $SiO_3H_2$ is added, the etching rate of the $SiO_2$ thin film increases in proportion to the radius of the wafer. In $Si_3N_4$ thin film, there is no difference in the etching rate according to the position. However, in the $SiO_2$ thin film, the etching rate increases in proportion to the radius. At the center of the wafer, the re-growth phenomenon is confirmed at a specific concentration or above. The difference in etch rates of $SiO_2$ thin films and the reason for regrowth at these positions are interpreted as the result of the flow rate of the chemical solution replaced with fresh solution.

• 대한금속재료학회지
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• 제50권9호
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• pp.653-657
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• 2012

In this study, a molybdenum disilicide ($MoSi_2$) coating process was investigated by hydrogen reduction and Si-pack cementation. At first, the metallic Mo coating was carried out by hydrogen reduction of $MoO_3$ powder at $750^{\circ}C$ for various holding times (1, 2, 3 h) in hydrogen atmosphere. A $4.3{\mu}m$ thick metallic molybdenum thin film was formed at 3 h. $MoSi_2$ was obtained by Si-pack cementation on molybdenum thin film through hydrogen reduction processing. It was carried out using $Si:Al_2O_3:NH_4Cl=5:92:3$ (wt%) packs at $900^{\circ}C$ for various holding times (30, 60, 90 min) in Ar atmosphere. When the holding time was 90 min, a $MoSi_2$ layer was coated successfully and a $15.4{\mu}m$ thickness was observed.

• Journal of Welding and Joining
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• 제14권6호
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• pp.93-100
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• 1996

Effect of a flux composition on weld metal toughness in submerged arc welding with 60kgf/$\textrm{mm}^2$ grade C-Mo type wires was investigated and interpreted in terms of weld metal microstructure and hardenability. Flux workability was also studied by characterizing a weld bead profile. Compared to other weld metals, .weld metal used alumina basic flux with nickel showed lowest oxygen content, highest hardenability and the most acicular ferrite. The highest impact toughness of that weld metal, however, was attributed to the tough matrix due to the nickel rather than to the larger amount of acicular ferrite. Manganese silicate flux had better workability than alumina basic flux, showing broader welding conditions resulting in a depth-to-width ratio of 0.5. The composition of oxides in the weld metal was dependent on the flux composition, showing MnO-SiO$_2$-TiO in manganese silicate flux and MnO-SiO$_2$-Al$_2$O$_3$-TiO in alumina basic flux. MnO-SiO$_2$composition in both oxides was similar to a tephroite.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.799-802
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• 2003

[ $LaNiO_3$ ](LNO) thin films were deposited on various substrates as Si and $Al_2O_3$ by sol-gel process using lanthanum nitrate and nickel acetate. The structure and orientation of the films were characterized by X-ray diffraction. The orientation factors of films on Si(100), Si(111), $SiO_2/Si(100)$ and $Al_2O_3$were 97%, 63%, 73%, and 24% respective. The conductivity was $7.6{\times}10^{-3}{\Omega}{\cdot}cm$ with 10 times coating at Si(100) substrate.

• Journal of Plant Biology
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• 제30권3호
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• pp.181-187
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• 1987

Copper inhibited PSII-mediated O2 evolution (H2OlongrightarrowDCIP, H2OlongrightarrowSiMo) but not PSImediated O2 uptake(DCIP. Asc.longrightarrowMV) in isolated Chinese cabbage chloroplasts. Copper toxicity on PSII-mediated O2 evolution was higher at alkaline condition than at acidic condition and was inhanced by light illumination after copper treatment. The increased toxicity by light illumination was not recovered by subsequent dark treatment. The inhibitory effect of copper on H2OlongrightarrowDCIP reaction was higher than that on H2OlongrightarrowSiMo reaction. This result suggests that there may be another inhibitory site of copper on PSII other than water oxidizing side of PSII.

• 전기전자학회논문지
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• 제21권3호
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• pp.252-255
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• 2017

고온자전합성과 후열처리 공정으로 $Mo_xW_{1-x}Si_2$ 발열체를 제조하였다. $Mo_xW_{1-x}Si_2$ 발열체의 신뢰성을 검증하기 위해 가속수명시험을 수행하였으며, 수명시간을 Minitab 프로그램으로 추정하였다. 또한, 가속수명시험 후의 $Mo_xW_{1-x}Si_2$ 발열체의 고장분석을 전기적과 구조적 특성으로부터 수행하였다. 그 결과, $Mo_xW_{1-x}Si_2$ 발열체의 지배적인 고장 유형은 발열체 내부의 크랙 형성과 $SiO_2$ 보호층의 박리임을 확인하였다.

• 한국해양공학회지
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• 제16권6호
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• pp.60-64
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• 2002

This paper describes the machining characteristics of the MoSi$_2$--based composites through the process of electric discharge drilling with various tubular electrodes. In addition to hardness characteristics, microstructures of Nb/MoSi$_2$laminate composites were evaluated from the variation of fabricating conditions, such as preparation temperature, applied pressure, and pressure holding time. MoSi$_2$-based composites have been developed in new materials for jet engines of supersonic-speed airplanes and gas turbines for high-temperature generators. These high performance engines may require new hard materials with high strength and high temperature-resistance. Also, with the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material. The tool electrode is almost -unloaded, because there is n direct contact between the tool electrode and the work piece. By combining a non-conducting ceramic with more conducting ceramic, it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and MoSi$_2$ powder was an excellent strategy to improve hardness characteristics of monolithic MoSi$_2$. However, interfacial reaction products, like (Nb, Mo)SiO$_2$and Nb$_2$Si$_3$formed at the interface of Nb/MoSi$_2$, and increased with fabricating temperature. MoSi$_2$composites, with which a hole drilling was not possible through the conventional machining process, enhanced the capacity of ED-drilling by adding MbSi$_2$, relative to that of SiC or ZrO$_2$reinforcements.

• 한국결정성장학회지
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• 제8권4호
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• pp.532-538
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• 1998

한국산 천연베릴을 잉요하여 온도구배융제환류법에 의해 에메랄드($3BeO{\cdot}Al_2O_3{\cdot}6SiO_2:Cr^{3+}$) 단결정이 성장되었다. 리튬-몰리브데늄-바나디움 산화물계 융제는 $(MoO_3+V_2O_5)/Li_2O$, 와 $V_2O_5-Li_2O$를 서로 다르게 용융한 2종류의 융제를 혼합하여 제조하였다. 융제의 최적 조성은 산화몰리브데늄.바나디움에 대한 산화리튬의 몰비($(MoO_3+V_2O_5)/Li_2O$)가 3몰이었고 융제첨가제는 Li2O량에 대하여 $K_2O$ 또는 $Na_2O$를 0.2mole% 이내로 치환하였다. 베릴원료의 용융 농도는 융제량에 대하여 3~10% 함량이었고, $Cr_2O_3$ 발색제는 베릴량에 대하여 1%이었다. 융액은 용융, 성장, 회수 블록으로 나뉘어진 3지대 온도구배 결정성장로에서, $1100^{\circ}C$와 $1000^{\circ}C$ 사이의 안정상태에서 연속적으로 순환되도록 하였다. 에메랄드 단결정은 성장지대에서 950~$1000^{\circ}C$ 구간에서 1일 1회 2시간동안 열진동 처리하였을 때 미소핵의 생성이 억제된 대형 단결정을 성장시킬 수 있었다. 육각주상 에메랄드 단결정의 우선성장방향은 c(0001) 바닥면이었고, m(1010) 기둥면에 수직이었다.

• 한국결정성장학회지
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• 제30권5호
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• pp.200-207
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• 2020

SHS 법으로 MoSi₂ 분말, (Mo_1/2W_1/2)Si₂ 분말 및 WSi₂ 분말을 합성하고 이 분말들을 500℃, 1,000℃, 1,200℃, 1,300℃, 1,400℃, 1,500℃ 및 1,600℃에서 열처리한 다음, 결정구조 및 열중량 변화 등을 관찰하였다. Mo-W-Si계의 silicide 분말은 500℃의 저온에서도 산화 반응이 일어나며, 저온 산화 및 분해로 생성되는 결정상은 MoO₃이었다. 1,200℃ 이상에서 열처리를 한 경우에 분해반응으로 생성된 SiO₂의 결정상은 상온에서 흔히 관찰되는 α-quartz가 아닌 α-cristobalite 상으로 생성되었다. W이 포함되면 저온과 고온에서 분해 반응이 더 많이 일어나는 것으로 나타났으며, 분말을 성형하여 소결한 시편의 경우에 MoSi₂와 (Mo_1/2W_1/2)Si₂는 저온이나 고온에서 1시간 열처리를 하더라도 저온산화에 의한 분해와 그에 따른 질량 변화 반응을 관찰하기 어려웠지만 WSi₂는 저온 산화에 의하여 소결 자체가 어려웠다.

• 한국재료학회지
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• 제5권8호
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• pp.921-928
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• 1995

MoSi$_2$heating elements were fabricated using MoSi$_2$, powder prepared by SHS. Their apparent density, electrical resistivity, bending strength and victors hardness were measured as a function of sintering temperature, time and the amount of ceramic additives. The additives were A1$_2$O$_3$, SiO$_2$and bentonite which were added as a plastisizer. The electrical resistivity of MoSi$_2$decreased with the increase in the apparent density as expected. It decreased when the additives were added and the increase was the largest for the case of SiO$_2$. The bending strength and hardness decreased when the grain size becomes larger which is opposite to the expectation from the Hall-Petch type relation. Instead, they showed inverse proportionality with the volume fraction of pores probably in an exponential manner. The strength and hardness also decreased with the additives.