• 제목/요약/키워드: $Al_2O_3$ nanocomposites

검색결과 63건 처리시간 0.033초

Preparation of Al@Fe2O3 Core-Shell Composites Using Amphiphilic Graft Copolymer Template

  • Patel, Rajkumar;Kim, Sang Jin;Kim, Jin Kyu;Park, Jung Su;Kim, Jong Hak
    • Korean Chemical Engineering Research
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    • 제52권2호
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    • pp.209-213
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    • 2014
  • A graft copolymer of poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) was synthesized via atom transfer radical polymerization (ATRP) and used as a structure-directing agent to prepare $Al@Fe_2O_3$ core-shell nanocomposites through a sol-gel process. The amphiphilic property of PVC-g-POEM allows for good dispersion of Al particles and leads to specific interaction with iron ethoxide, a precursor of $Fe_2O_3$. Secondary bonding interaction in the sol-gel composites was characterized by Fourier transform-infrared (FT-IR) spectroscopy. The well-organized morphology of $Al@Fe_2O_3$ core-shell nanocomposites was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were used to analyze the elemental composition and crystallization structure of the composites.

Structure and Properties for 28 GHz Microwave Sintered PZT Nanocomposites

  • Tajima, Ken-ichi;Hwang, Hae-Jin;Sando, Mutsuo;Niihara, Koichi
    • The Korean Journal of Ceramics
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    • 제4권4호
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    • pp.352-355
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    • 1998
  • Dense $ Pb(Zr, Ti)O_3(PZT)/Al_2O_3$ nanocomposites were prepared by the 28 GHz microwave heating method and conventional electric furnace sintering. Electrical and mechanical properties of the composites were investigated. The fracture strength of the PZT composites with 0.1vol% $Al_2O_3$ was significantly improved in both sintering methods. Smaller grain size and effective reinforcement of the PZT matrix by the second phase were considered to be responsible for the excellent fracture strength. Planar electromechanical coupling factor Kp of the composites sintered by 28GHz microwave heating was higher than that of the materical prepared by the conventional route. It seemed that the control of the reaction between PZT and $Al_2O_3$ by the microwave rapid sintering resulted in the high piezoelectric properties.

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소결분위기 변환온도가 Al2O3/Cu 나노복합재료의 미세조직과 파괴강도에 미치는 영향 (Effect of Sintering Atmosphere Changing Temperature on Microstructure and Mechanical Property of Al2O3/Cu Nanocomposites)

  • 오승탁;윤세중
    • 한국분말재료학회지
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    • 제11권5호
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    • pp.421-426
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    • 2004
  • The microstructure and mechanical property of hot-pressed $Al_2O_3/Cu$ composites with a different temperature for atmosphere changing from H$_{2}$ to Ar have been studied. When atmosphere-changed from H$_{2}$ to Ar gas at 145$0^{\circ}C$, the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when atmosphere-changed at low temperature of 110$0^{\circ}C$ the composite showed more homogeneous microstructure, higher fracture strength and smaller deviation in strength. Based on the thermodynamic consideration and microstructural analysis, it was interpreted that the Cu wetting behavior relating to the formation of CuAlO$_{2}$ is probably responsible for strong dependence of microstructure on atmosphere changing temperature. The reason for a strong sensitivity of fracture strength and especially of its deviation to atmosphere changing temperature was explained by the microstructural inhomogeneity and by the role of CuAlO$_{2}$ phase on the interfacial bonding strength.

열화학적 방법에 의한 전극용 나노 Cu/Al2O3 복합분말 합성 (Synthesis of Cu/Al2O3 Nanostructured Composite Powders for Electrode Application by Thermochemical Process)

  • 이동원;배정현;김병기
    • 한국분말재료학회지
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    • 제10권5호
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    • pp.337-343
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    • 2003
  • Nanostructured Cu-$Al_2O_3$ composite powders were synthesized by thermochemical process. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from water-soluble copper and aluminum nitrates, 2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nano-structured CuO + $Al_2O_3$, and 3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the gamma-$Al_2O_3$, and different alumina formation behaviors appeared with various heat treating temperatures. The mean particle size of the final Cu/$Al_2O_3$ composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/$Al_2O_3$ composite by the conventional internal oxidation process.

PECS에 의해 제조된 $Al_2O_3$/5vol.%Cu 나노복합재료의 파괴인성 (Fracture Toughness of $Al_2O_3$/5vol.%Cu Nanocomposites Fabricated by PECS)

  • 민경호;홍대희;김대건;김영도;문인형
    • 한국분말재료학회지
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    • 제7권3호
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    • pp.149-153
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    • 2000
  • In this study, the fabrication of $Al_2O_3$/5vol.%Cu nanocomposite and its mechanical property were discussed. The nanocomposite powders were produced by high energy ball milling of $Al_2O_3$ and Cu elemental powders. The ball-milled powders were sintered with Pulse Electric Current Sintering (PECS) facility. The relative densities of specimens sintered at $1200^{\circ}C$ and $1250^{\circ}C$ after soaking process at $900^{\circ}C$ were 96% and over 97%, respectively. The sintered microstructures were composed of $Al_2O_3$ matrix and the nano-sized Cu particles distributed on grain boundaries of $Al_2O_3$ matrix. The nanocomposite exhibited the enhanced fracture toughness compared with general monolithic $Al_2O_3$. The toughness increase was explained by the crack deflection and bridging by dispersed Cu particles.

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Multifunctionality in Ceramic/Metal Nanocomposites

  • Sekino, Tohru;Kondo, Hiroki;Niihara, Koichi
    • 한국분말재료학회지
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    • 제8권3호
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    • pp.186-191
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    • 2001
  • Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.

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Effects of nanomaterials on hydration reaction, microstructure and mechanical characteristics of cementitious nanocomposites: A review

  • Kim, Gwang Mok
    • 도시과학
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    • 제9권1호
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    • pp.7-16
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    • 2020
  • Application of nanomaterials to cementitious composites has been attempted with the rapid development of nanotechnology since the 1990s. Various nanomaterials such as carbon nanotube, graphene, nano-SiO2, nano-TiO2, nano-Al2O3, nano-Clay, and nano-Magnetite have been applied to cementitious composites to improve the mechanical properties and the durability, and to impart a variety of functionality. In-depth information on the effect of nanomaterials on the hydration reaction, the microstructure, and the mechanical properties of cementitious nanocomposites is provided in the present study. Specifically, this paper mostly deals with the previous studies on the heat evolution characteristics of cementitious nanomaterials at an early age of curing, and the pore and the compressive strength characteristics of cementitious nanocomposites. Furthermore, the effect of nanomaterials on the cementitious nanocomposites was systematically discussed with the reviews.