• 제목/요약/키워드: Amorphous Structure

검색결과 977건 처리시간 0.027초

Amorphous Vanadium Titanates as a Negative Electrode for Lithium-ion Batteries

  • Lee, Jeong Beom;Chae, Oh. B.;Chae, Seulki;Ryu, Ji Heon;Oh, Seung M.
    • Journal of Electrochemical Science and Technology
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    • 제7권4호
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    • pp.306-315
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    • 2016

  • Amorphous vanadium titanates (aVTOs) are examined for use as a negative electrode in lithium-ion batteries. These amorphous mixed oxides are synthesized in nanosized particles (<100 nm) and flocculated to form secondary particles. The $V^{5+}$ ions in aVTO are found to occupy tetrahedral sites, whereas the $Ti^{4+}$ ions show fivefold coordination. Both are uniformly dispersed at the atomic scale in the amorphous oxide matrix, which has abundant structural defects. The first reversible capacity of an aVTO electrode ($295mAhg^{-1}$) is larger than that observed for a physically mixed electrode (1:2 $aV_2O_5$ | $aTiO_2$, $245mAhg^{-1}$). The discrepancy seems to be due to the unique four-coordinated $V^{5+}$ ions in aVTO, which either are more electron-accepting or generate more structural defects that serve as $Li^+$ storage sites. Coin-type Li/aVTO cells show a large irreversible capacity in the first cycle. When they are prepared under nitrogen (aVTO-N), the population of surface hydroxyl groups is greatly reduced. These groups irreversibly produce highly resistive inorganic compounds (LiOH and $Li_2O$), leading to increased irreversible capacity and electrode resistance. As a result, the material prepared under nitrogen shows higher Coulombic efficiency and rate capability.

  • https://doi.org/10.5229/JECST.2016.7.4.306 인용 PDF KSCI

Ni/Si 기판을 사용하여 성장시킨 비결정질 $SiO_x$ 나노 와이어의 성장 메커니즘 (Direct synthesis mechanism of amorphous $SiO_x$ nanowires from Ni/Si substrate)

  • 송원영;신동익;이호준;김형섭;김상우;윤대호
    • 한국결정성장학회지
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    • 제16권6호
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    • pp.256-259
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    • 2006

  • Vapor phase epitaxy(VPE)법을 사용하여 amorphous $SiO_x$. nanowires를 성장시켰다. Ni thin film을 촉매로 사용하여 Si 기판위에 $800{\sim}1100^{\circ}C$ 범위의 온도에서 성장시켰으며, $SiO_x$ nanowires의 성장 메커니즘은 Vapor-liquid-solid(VLS)으로 확인되었다. $SiO_x$ nanowires의 shape와 morphology는 scanning electron microscope(SEM)으로 분석하였으며, cotton-like형태이고 길이는 $10{\mu}m$정도였다. 그리고 구조적 특징은 transmission electron microscope(TEM)으로 관찰하였고, $SiO_x$ nanowires의 성분 분석은 energy dispersed X-ray spectroscopy(EDS)로 하였다. EDX spectrum으로 nanowires가 Si와 O로 구성되어졌음을 확인하였다.

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열분해 온도와 성형압력의 영향에 따른 비정질 탄화규소 블록의 치밀화 (Effect of pyrolysis temperature and pressing load on the densification of amorphous silicon carbide block)

  • 주영준;주상현;조광연
    • 한국결정성장학회지
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    • 제30권6호
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    • pp.271-276
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    • 2020

  • 본 연구에서는 유기 규소 폴리머(organosilicon polymer)인 폴리카보실란(polycarbosilane, PCS)을 사용하여 비정질 탄화규소 블록을 제조를 진행하였다. 다양한 형상의 치밀한 탄화규소 블록은 큐어링된 PCS 미세분말을 일축가압성형기를 통해 2~8 ton 하중을 가한 후 1100℃, 1200℃, 1300℃, 1400℃의 열처리 과정을 거쳐 제조되었으며, 물리적 화학적 특성 분석을 위해 열중량분석기(TGA), 주사전자현미경(SEM), 에너지분광분석법(EDS), 만능시험기(UTM)을 이용하였다, 제조된 탄화규소 성형체는 열분해 온도가 증가함에 따라 SiO와 CO 가스로의 분해가 발생하였고, 비정질의 구조에서 β-SiC 결정입자가 성장함을 보였다. 또한, 밀도와 굴곡강도는 1100℃의 열분해 온도에서 제조된 탄화규소 성형체가 1.9038 g/㎤과 6.189 MPa으로 가장 높았다. 제조된 비정질 탄화규소 블록은 이전에 보고된 마이크로파 도움 발열체와 같이 다른 분야에 적용 가능할 것으로 기대된다.

  • https://doi.org/10.6111/JKCGCT.2020.30.6.271 인용 PDF KSCI HTML

철계 비정질 분말을 활용한 초고속 용사 코팅층 개발 (Development of Amorphous Iron Based Coating Layer using High-velocity Oxygen Fuel (HVOF) Spraying)

  • 김정준;김송이;이종재;이석재;임현규;이민하;김휘준;최현주
    • 한국분말재료학회지
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    • 제28권6호
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    • pp.483-490
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    • 2021

  • A new Fe-Cr-Mo-B-C amorphous alloy is designed, which offers high mechanical strength, corrosion resistance as well as high glass-forming ability and its gas-atomized amorphous powder is deposited on an ASTM A213-T91 steel substrate using the high-velocity oxygen fuel (HVOF) process. The hybrid coating layer, consisting of nanocrystalline and amorphous phases, exhibits strong bonding features with the substrate, without revealing significant pore formation. By the coating process, it is possible to obtain a dense structure in which pores are hardly observed not only inside the coating layer but also at the interface between the coating layer and the substrate. The coating layer exhibits good adhesive strength as well as good wear resistance, making it suitable for coating layers for biomass applications.

  • https://doi.org/10.4150/KPMI.2021.28.6.483 인용 PDF KSCI

금속박막의 물리적 성질(I)(증착속도에 따르는 구조변화) (-Physical Properties of Metal Thin Film-(Changes of Structure with Evaporation Rates))

  • 백수현;조현춘
    • 대한전자공학회논문지
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    • 제24권6호
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    • pp.980-985
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    • 1987

  • The thin metal films of Cr, Al, Mn and were made in various evaporation rates with 100\ulcornerthickness under 2x10**-9 bar vacuum level. We analized and discussed the relationships between changes of structure, morphology and sheet resistance, light transmittance for the corresponding evaporation rates. As the evaporation rates were decreased at higher rates, grain sizes of all film were decreased, however both of the sheet resistance and light transmittance were increased. At lower evaporation rate, films of Cr and Cu porduced non-stoi-chiometric oxides but Al an Mn showed up amorphous structures.

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