• Title/Summary/Keyword: ZrO_2$

Search Result 2,331, Processing Time 0.043 seconds

Three Dimensionally Ordered Microstructure of Polycrystalline Zirconia Ceramics with Micro-Porosity

  • Chang, Myung Chul
    • Journal of the Korean Ceramic Society
    • /
    • v.53 no.1
    • /
    • pp.50-55
    • /
    • 2016
  • In order to make a highly ordered three-dimensionally macro-porous structure of zirconia ceramics, porogen precursors PMMA beads were prepared by emulsion polymerization using acrylic monomer. The monodisperse PMMA latex beads were closely packed by centrifugation as a porogen template for the infiltration of zirconium acetate solution. The mixed compound of PMMA and zirconium acetate was dried. According to the firing schedule, dry compacts of PMMA and zirconium acetate were calcined at 475C to obtain micro-, macro-, and meso- structures of polycrystalline zirconia with monodispersed porosity. Inorganic frameworks composed of ZrO2 were formed and showed a three Dimensionally Ordered Microstructure [3DOM] of ZrO2 ceramics. The obtained ZrO2 skeleton was calcined at 710C. The 3DOM ZrO2 skeleton showed color tuning in solutions such as deionized [DI] H2O and/or methanol. The monodispersed crystalline micro-structure with micro/meso porosity was observed by FE-SEM.

Characteristic of high-K dielectric material((ZrO2)grown by MOMBE (MOMBE 로 성장시킨 고유전물질 (ZrO2)의 특성 연구)

  • 최우종;홍장혁;김두수;명재민
    • Proceedings of the Materials Research Society of Korea Conference
    • /
    • 2003.03a
    • /
    • pp.79-79
    • /
    • 2003
  • 최근 CMOS(Complementary Metal Oxide Semiconductor) 능동소자에 사용되는 MOS-FET (Metal Oxide Semiconductror Field Effect Transitror)의 전체적인 크기 감소추세에 따라 금속 전극과 반도체 사이의 절연층 두께 감소가 요구되고 있다. 현재 보편적으로 사용되고 있는 SiO2층은 두께 감소에 따른 터널링 전류의 증가로 더 이상의 두께 감소를 기대하기 어려운 상태이다. 이러한 배경에서 최근 터널링 전류를 충분히 감소시키면서 요구되는 절연특성을 얻을 수 있는 새로운 고유전 물질 (high-k dielectric material)에 대한 연구가 이루어지고 있다. 현재까지 연구되어온 고유전 물질 중, 고유전 상수, 큰 밴드갭, Si과의 열적 안정성을 갖는 물질로 ZrO2가 주목을 받고 있다. 본 연구에서는 Metal Organic Molecular Beam Epitaxy (MOMBE) 방법을 이용한 ZrO2 층의 성장조건 및 특성을 평가하고자 한다.

  • PDF

Dielectric properties with variation of doped mount ZrO2 of BSCT ceramics (ZrO2첨가량에 따른 BSCT 세라믹의 유전특성)

  • 조현무;이성갑;이영희;배선기
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2001.07a
    • /
    • pp.153-156
    • /
    • 2001
  • (Ba0.6xSr0.4Cax)TiO3 (x=0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method and their dielectric properties were investigated with variation of composition ratio, doped ZrO2 (0.5, 1.0, 1.5, 2.0, 3.0 wt%) and sintered at 1450C. The dielectric constant and loss of the x=0.10 specimen applied field were 19.86 and 0.302 % at 0 V/cm, and 25.937 and 0.339 % at 300 V/cm, respectively. Dielectric constant were increased with increased applied field and decreased with increased frequency, and dielectric loss were within 0.1% at applied 800 MHz, respectively. all specimens showed fairly good applied field. Although, dielectric constant and loss of all specimen showed to tend of nearly the same. same.

  • PDF

Preparation of 27Ni6Zr4O143M(M=Mg, Ca, Sr, or Ba)O/70 Zeolite Y Catalysts and Hydrogen-rich Gas Production by Ethanol Steam Reforming

  • Kim, Dongjin;Lee, Jun Su;Lee, Gayoung;Choi, Byung-Hyun;Ji, Mi-Jung;Park, Sun-Min;Kang, Misook
    • Bulletin of the Korean Chemical Society
    • /
    • v.34 no.7
    • /
    • pp.2073-2080
    • /
    • 2013
  • In this study the effects of adding alkaline-earth (IIA) metal oxides to NiZr-loaded Zeolite Y catalysts were investigated on hydrogen rich production by ethanol steam reforming (ESR). Four kinds of alkaline-earth metal (Mg, Ca, Sr, or Ba) oxides of 3.0% by weight were loaded between the Ni6Zr4O14 main catalytic species and the microporous Zeolite Y support. The characterizations of these catalysts were examined by XRD, TEM, H2-TPR, NH3-TPD, and XPS. Catalytic performances during ESR were found to depend on the basicity of the added alkaline-earth metal oxides and H2 production and ethanol conversion were maximized to 82% and 98% respectively in 27(Ni6Zr4O14)3MgO/70Zeolite Y catalyst at 600C. Many carbon deposits and carbon nano fibers were seen on the surface of 30Ni6Zr4O14/70Zeolite Y catalyst but lesser amounts were observed on alkaline-earth metal oxide-loaded 27(Ni6Zr4O14)3MO/70Zeolite Y catalysts in TEM photos after ESR. This study demonstrates that hydrogen yields from ESR are closely related to the acidities of catalysts and that alkaline-earth metal oxides reduce the acidities of 27(Ni6Zr4O14)3MO/70Zeolite Y catalysts and promote hydrogen evolution by preventing progression to hydrocarbons.

Fabrication and characterization of ZrxCe1-xO2 catalytic powder by a hydrothermal process (수열합성공정에 의한 ZrxCe1-xO2 촉매 분말의 제조 및 특성)

  • Choi, Yeon-Bin;Son, Jeong-hun;Sohn, Jeong Ho;Bae, Dong-Sik
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.27 no.6
    • /
    • pp.309-312
    • /
    • 2017
  • The ceria powder is excellent in oxygen storage capacity (OSC) through the oxidation and reduction reaction of Ce ions and is used as a typical material for a three-way catalyst of an automobile which purifies the exhaust gas. However, since ceria generally has poor thermal stability at high temperatures, it is doped with metal ions to improve thermal stability. Therefore, in this study, Zr ions were doped into ceria powder, and their characteristics were further improved due to the increase of specific surface area with decreasing particle size due to doping. In this study, the synthesis of zirconium doped ceria nanopowder was synthesized by hydrothermal process. In order to synthesis Zr ion doped ceria nanopowder, the precursor reaction at was 200C for 6 hours. The average particle size of synthesized Zr doped CeO2 nanopowder was below 20 nm. The specific surface area of synthesized Zr ion doped ceria nanopowder increased from 52.03m2/g to 132.27m2/g with Zr increased 30 %.

Preparation of Li2OZrO2P2O5SiO2 based Glassy Solid Electrolytes by Sol-Gel Process and Their Ionic Conduction (솔-젤법에 의한 Li2OZrO2P2O5SiO2계 유리 고체전해질의 제조와 그의 이온전도성)

  • 박강석;김기원;강은태
    • Journal of the Korean Ceramic Society
    • /
    • v.31 no.6
    • /
    • pp.660-670
    • /
    • 1994
  • Transparent, crack-free dried gel monoliths with a composition of LiZr1.5Si2P2O12.5 have been synthesized by the low temperature polymerization of the Sol-Gel technique using metal alkoxides as starting materials. After initial reaction (20~40 min), each metal alkoxide closely paralleled each other during the hydrolysis reactions. The safe drying conditions of gels with no creaks the control of the shrinkage rate. The gels converted into the glass by heat treatment at 750C. FTIR data indicated that the gels were phase separated into silicarich and phosphate-rich regions with the lithium. XRD results showed the formation of crystalline LiH2PO4. The gels dried at 150C or fired at 750C contained the residual water. The high ionic conductivity at room temperature for these gels was attributed to the motion of protons.

  • PDF

Microwave Dielectric Properties of Donor doped Zr0.8Sn0.2TiO4 Ceramics (Donor Dopant 첨가 Zr0.8Sn0.2TiO4 세라믹스의 마이크로파 유전특성)

  • 김윤호
    • Journal of the Microelectronics and Packaging Society
    • /
    • v.2 no.2
    • /
    • pp.31-40
    • /
    • 1995
  • Donor dopant로 WO3, Ta2O5 및 Nb2O5를 첨가한 Zr0.8Sn0.2TiO4 세라믹스의 유전상수 εr 품 질계수 Q 및 공진주파수의 온도계수 rf에 대하여 연구하였다. 1390C에서 32시간 소결시 donor dopant 첨가량에 따른 ZST의 유전상수는 소결밀도의 변화 거동과 잘 일치하였다. 5.5 GHz에서 측정 한 ZST의 품질계수 Q는 ~0.5 mol% WO3 Ta2O5 및 Nb2O5 첨가에 의해 6800에서 8500 정도로 증가 하였다. ZST의 τf는 0.3 mol%까지의 WO3 첨가량 증가에 따라 0 ppm/C에서 -4.6 ppm/C까지 음 의 값으로 직선적으로 감소하였으며 0.4 mol% 범위의 Ta2O5 및 Nb2O5 첨가에 의해 -7 ppm/C 까지 직선적으로 감소하였다.