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Effect of Si on the Microstructure and Mechanical Properties of Ti-Al-Si-C-N Coatings (Si 함량에 따른 Ti-Al-Si-C-N 코팅막의 미세구조와 기계적 특성의 변화에 관한 연구)

  • Hong, Young-Su;Kwon, Se-Hun;Kim, Kwang-Ho
    • Journal of Surface Science and Engineering
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    • v.42 no.2
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    • pp.73-78
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    • 2009
  • Quinary Ti-Al-Si-C-N films were successfully synthesized on SUS 304 substrates and Si wafers by a hybrid coating system combining an arc ion plating technique and a DC reactive magnetron sputtering technique. In this work, the effect of Si content on the microstructure and mechanical properties of Ti-Al-C-N films were systematically investigated. It was revealed that the microstructure of Ti-Al-Si-C-N coatings changed from a columnar to a nano-composite by the Si addition. Due to the nanocomposite microstructure of Ti-Al-Si-C-N coatings, the microhardness of The Ti-Al-Si-C-N coatings significantly increased up to 56 GPa. In addition the average friction coefficients of Ti-Al-Si-C-N coatings were remarkably decreased with Si addition. Therefore, Ti-Al-Si-C-N coatings can be applicable as next-generation hard-coating materials due to their improved hybrid mechanical properties.

Effect of Nitrogen Gas Pressure on the Mechanical Properties of Polymer Composite Materials (고분자 복합재료의 기계적 물성에 미치는 질소기압의 영향)

  • Kim, Bu-An;Hwang, Hyun-Young;Kang, Suk-Jun;Moon, Chang-Kwon
    • Journal of Power System Engineering
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    • v.20 no.5
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    • pp.14-19
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    • 2016
  • This study is about the effect of nitrogen gas pressures during manufacturing process on the mechanical properties of composite materials. TiO2/epoxy resin nanocomposites and carbon fiber reinforced epoxy resin(CFRP) composites were fabricated under various nitrogen gas pressures. Tensile strength test, vicker's hardness test and fracture surface observation were carried out to investigate the effect of nitrogen gas pressure. As a result, the tensile strength of nanocomposite and CFRP composites showed clearly increasing tendency by a change in the nitrogen gas pressure up to 3.0 atm and then the tensile strength decreased a little. However, the vicker's hardness of TiO2/epoxy nanocomposites showed same hardness values regardless of the nitrogen gas pressures.

Synthesis and Properties of Ni-CNT Nanocomposites Using Electrical Explosion of Wire in Different Conditions

  • Maithili Biswas; Jin-Chun Kim
    • Korean Journal of Materials Research
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    • v.34 no.3
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    • pp.138-143
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    • 2024
  • Ni-CNT nanocomposites were synthesized via the electrical explosion of wire (EEW) in acetone and deionized (DI) water liquid conditions with different CNT compositions. The change in the shape and properties of the Ni-CNT nanopowders were determined based on the type of fluids and CNT compositions. In every case, the Ni nanopowder had a spherical shape and the CNT powder had a tube shape. However, the Ni-CNT nanopowders obtained in DI water exhibited irregular shapes due to the oxidation of Ni. Phase analysis also revealed the existence of nickel oxide when using DI water, as well as some unknown peaks with acetone, which may form due to the metastable phase of Ni. Magnetic properties were investigated using a Vibrating Sample Magnetometer (VSM) for all cases. Nanopowders prepared in DI water conditions had better magnetic properties than those in acetone, as evidenced by the simultaneous formation of super paramagnetic NiO peaks and ferromagnetic Ni peaks. The DI water (Ni:CNT = 1:0.3) sample revealed better magnetic results than the DI water (Ni-CNT = 1:0.5) because it had less CNT contents.

Characterization and Electrical Conductivity of Carbon-Coated Metallic (Ni, Cu, Sn) Nanocapsules

  • Wang, Dong Xing;Shah, Asif;Zhou, Lei;Zhang, Xue Feng;Liu, Chun Jing;Huang, Hao;Dong, Xing Long
    • Applied Microscopy
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    • v.45 no.4
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    • pp.236-241
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    • 2015
  • Carbon-coated Ni, Cu and Sn nanocapsules were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and a four-point probe device. All of these nanocapsules were prepared by an arc-discharge method, in which the bulk metals were evaporated under methane (CH4) atmosphere. Three pure metals (Ni, Cu, Sn) were typically diverse in formation of the carbon encapsulated nanoparticles and their different mechanisms were investigated. It was indicated that a thick carbon layers formed on the surface of Ni(C) nanocapsules, whereas a thin shell of carbon with 1~2 layers covered on Cu(C) nanocapsules, and the Sn(C) nanocapsules was, in fact, a longger multi-walled carbon nanotubes partially-filled with metal Sn. As one typical magnetic/dielectric nanocomposite particles, Ni(C) nanocapsules and its counterpart of oxide-coated Ni(O) nanocapsules were compared in the electrically conductive behaviors for further applications as the electromagnetic materials.

Thermal Stability and Properties of Cu-TiB2 Nanocomposites Prepared by Combustion Synthesis and Spark-plasma Sintering

  • Kwon, Dae-Hwan;Nguyen, Thuy Dang;Dudina, Dina;Kum, Jong-Won;Choi, Pyuck-Pa;Kim, Ji-Soon;Kwon, Young-Soon
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1203-1204
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    • 2006
  • Cu-TiB2 nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.%TiB2 powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.%TiB2 composites. TiB2 particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at 650750C were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to 950C for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu-TiB2 composite showed good thermal stability at eleveated temperature.

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Surface-modified Nanoparticle Additives for Wear Resistant Water-based Coatings for Galvanized Steel Plates

  • Becker-Willinger, Carsten;Heppe, Gisela;Opsoelder, Michael;Veith, H.C. Michael;Cho, Jae-Dong;Lee, Jae-Ryung
    • Corrosion Science and Technology
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    • v.9 no.4
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    • pp.147-152
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    • 2010
  • Conventional paints for conversion coating applications in steel production derived mainly from water-based polymer dispersions containing several additives actually show good general performance, but suffer from poor scratch and abrasion resistance during use. The reason for this is because the relatively soft organic binder matrix dominates the mechanical surface properties. In order to maintain the high quality and decorative function of coated steel sheets, the mechanical performance of the surface needs to be improved significantly. In fact the wear resistance should be enhanced without affecting the optical appearance of the coatings by using appropriate nanoparticulate additives. In this direction, nanocomposite coating compositions (Nanomer(R)) have been derived from water-based polymer dispersions with an increasing amount of surface-modified nanoparticles in aqueous dispersion in order to monitor the effect of degree of filling with rigid nanoparticles. The surface of nanoparticles has been modified for optimum compatibility with the polymer matrix in order to achieve homogeneous nanoparticle dispersion over the matrix. This approach has been extended in such a way that a more expanded hybrid network has been condensed on the nanoparticle surface by a hydrolytic condensation reaction in addition to the quasi-monolayer type small molecular surface modification. It was expected that this additional modification will lead to more intensive cross-linking in coating systems resulting in further improved scratch-resistance compared to simple addition of nanoparticles with quasi-monolayer surface modification. The resulting compositions have been coated on zinc-galvanized steel and cured. The wear resistance and the corrosion protection of the modified coating systems have been tested in dependence on the compositional change, the type of surface modification as well as the mixing conditions with different shear forces. It has been found out that for loading levels up to 50 wt.-% nanoparticles, the mechanical wear resistance remains almost unaffected compared to the unmodified resin. In addition, the corrosion resistance remained unaffected even after 180 bending test showing that the flexibility of coating was not decreased by nanoparticle addition. Electron microscopy showed that the inorganic nanoparticles do not penetrate into the organic resin droplets during the mixing process but rather formed agglomerates outside the polymer droplet phase resulting in quite moderate cross linking while curing, because of viscosity. The proposed mechanisms of composite formation and cross linking could explain the poor effect regarding improvement of mechanical wear resistance and help to set up new synthesis strategies for improved nanocomposite morphologies, which should provide increased wear resistance.

Preparation of Three-Dimensional Graphene/Metal Oxide Nanocomposites for Application of Supercapacitors (슈퍼커패시터 응용을 위한 3차원 그래핀/금속 산화물 나노복합체 제조)

  • Kim, Jung Won;Choi, Bong Gill
    • Applied Chemistry for Engineering
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    • v.26 no.5
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    • pp.521-525
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    • 2015
  • Graphene-based electrode materials have been widely explored for supercapacitor applications due to their unique two-dimensional structure and properties. In particular, Three-dimensional (3D) graphene materials are of great importance for preparing electrode materials because they can provide large surface area, efficient and rapid electron and ion transfer, and mechanical stability. Recently, a number of 3D hybrid architecture of graphene/metal oxides have been developed to increase simultaneously energy and power densities of supercapacitors. This review presents the recent progress of 3D nanocomposites based on graphene and metal oxides. Preparation methods and structures of these 3D nanocomposites and their great potential in supercapacitor applications have been summarized.

Relation between Resistance and Capacitance in Atomically Dispersed Pt-SiO2 Thin Films for Multilevel Resistance Switching Memory (Pt 나노입자가 분산된 SiO2 박막의 저항-정전용량 관계)

  • Choi, Byung Joon
    • Korean Journal of Materials Research
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    • v.25 no.9
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    • pp.429-434
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    • 2015
  • Resistance switching memory cells were fabricated using atomically dispersed Pt-SiO2 thin film prepared via RF co-sputtering. The memory cell can switch between a low-resistance-state and a high-resistance-state reversibly and reproducibly through applying alternate voltage polarities. Percolated conducting paths are the origin of the low-resistance-state, while trapping electrons in the negative U-center in the Pt-SiO2 interface cause the high-resistance-state. Intermediate resistance-states are obtained through controlling the compliance current, which can be applied to multi-level operation for high memory density. It is found that the resistance value is related to the capacitance of the memory cell: a 265-fold increase in resistance induces a 2.68-fold increase in capacitance. The exponential growth model of the conducting paths can explain the quantitative relationship of resistance-capacitance. The model states that the conducting path generated in the early stage requires a larger area than that generated in the last stage, which results in a larger decrease in the capacitance.

Electrical Conductivity Behavior of 6FDA-based Fluorinated Polyimide/PMMA-g-MWCNT Nanocomposite Film (6FDA를 포함한 불소계 폴리이미드와 PMMA가 그래프트된 카본나노튜브 나노복합필름의 전기 전도성 연구)

  • Yun, Sung-Jin;Im, Hyun-Gu;Kim, Joo-Heon
    • Polymer(Korea)
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    • v.34 no.2
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    • pp.97-103
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    • 2010
  • PMMA was grafted on MWCNT surface in order to prepare conducting film composed of 6FDAbased polyimide/MWCNT. The electrical conductivity of 6FDA-based polyimide/PMMA-g-MWCNT was investigated as a function of PMMA-g-MWCNT content. Dispersion of MWCNT in 6FDA-based polyimide composite film was better than the pristine MWCNT due to the interaction force between PMMA and 6FDA-based polyimide. Electrical conductivity was interpreted by percolation threshold theory. As a result, 6FDA-6FpDA/PMMA-g-MWCNT which have high critical exponents and low critical concentration showed better dispersion than polyimide composite material that contains DABA(diamino benzoic acid).

Effect of Sintering Temperature on Microstructure and Mechanical Properties of Cu Particles Dispersed Al2O3 Nanocomposites (Cu 입자분산 Al2O3 나노복합재료의 미세조직과 기계적 특성에 미치는 소결온도의 영향)

  • Jeong, Young-Keun;Oh, Sung-Tag;Choa, Yong-Ho
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.366-370
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    • 2006
  • The microstructure and mechanical properties of hot-pressed Al2O3/Cu composites with a different sintering temperature have been studied. The size of matrix grain and Cu dispersion in composites increased with increase in sintering temperature. Fracture toughness of the composite sintered at high temperature exhibited an enhanced value. The toughness increase was explained by the thermal residual stress, crack bridging and crack branching by the formation of microcrack. The nanocomposite, hot-pressed at 1450C, showed the maximum fracture strength of 707 MPa. The strengthening was mainly attributed to the refinement of matrix grains and the increased toughness.