• Title/Summary/Keyword: Nano grain size

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Effect of nano-Nb2O5 on the microstructure and mechanical properties of AZ31 alloy matrix nanocomposites

  • Huang, Song-Jeng;Kannaiyan, Sathiyalingam;Subramani, Murugan
    • Advances in nano research
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    • v.13 no.4
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    • pp.407-416
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    • 2022
  • In this study, the gravitating mechanical stir casting method was used to fabricating the Nb2O5/AZ31 magnesium matrix nanocomposites. Niobium pentoxide (Nb2O5) used as reinforcement with two different weight percentages (3 wt % and 6 wt %). The influence of Nb2O5 on microstructure and mechanical properties has been investigated. The microstructure analysis showed that the composites are mainly composed of the primary α-magnesium phase and phase β-Mg17Al12 secondary phase. The secondary phase was dispersed evenly along the grain boundary of the Mg phase. The Nb2O5/AZ31 nanocomposites revealed that the grain size and its lamellar shape (β-Mg17Al12) were gradually refined. Different strengthening mechanisms were assessed in terms of their contributions. Results showed that composite material properties of hardness, yield strength, and fracture study were directly related to Nb2O5 as a reinforcement. The maximum values of the mechanical properties were achieved with the addition of 3 wt% Nb2O5 on the AZ31 alloy.

Exchange Coupling in Massively Produced Nd2Fe14B+Fe3B Nanocomposite Powders

  • Yang, Choong Jin;Park, Eon Byung;Han, Jong Soo;Kim, Eung Chan
    • Journal of Magnetics
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    • v.9 no.2
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    • pp.27-33
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    • 2004
  • Magnetic properties of $Nd_4Fe_{77.5}B_{18.5}$ compound in term of exchange coupling between $Nd_2Fe_{14}B$ and $Fe_3B$ magnetic nano crystals in melt spun powders were characterized by varying the quenching speed in mass production line. The exchange coupled phenomenon was characterized as functions of nano crystal size and volume fraction of each magnetic phase which was possible by employing Henkel plot (${\delta}M$) and refined Mossbauer spectroscopy. The optimized magnetic properties obtained from the present volume production line were: $B_r= 11.73 kG,{_i}H_c/ = 3.082 kOe$, and $(BH)_{max} = 12.28 MGOe.$ The volume fraction of each magnetic phase for those conditions giving the grain size of 10 nm were ${\alpha}-Fe; 4.2%, Fe_3B; 60.1 %$, and $Nd_2Fe_{14}B; 35.7%$. The superior magnetic properties in the $Nd_2Fe_{14}Fe_3B$ based nanocomposites were confirmed to be dependant on the volume fraction of $Fe_3B$.

Fabrication of $Al_2O_3$/SiC Hybrid-Composite ($Al_2O_3$/SiC Hybrid-Composite의 제조)

  • Lee, Su-Yeong;Im, Gyeong-Ho;Jeon, Byeong-Se
    • 연구논문집
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    • s.26
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    • pp.103-112
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    • 1996
  • $Al_2O_3/SiC$ Hybrid-Composite has been fabricated by conventional powder process. The addition of $\alpha-Al_2O_3$ as seed particles in the transformation of $\gamma-Al_2O_3 to $\alpha-Al_2O_3$ provided a homogeneity of the microstructure, resulting in increase of mechanical properties. The grain growth of $Al_2O_3$ are significantly surpressed by the addition of nano-sized. SiC particles, increasing in fracture strength. The addition of SiC plates to $Al_2O_3$ nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC plates with nitrides such as BN and /SiC$Si_3N_4$ enhanced fracture toughness much more than uncoated SiC plates by inducing crack deflection.

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Synthesis and Characterization of Middle Infrared Transmission ZnS Ceramics by Heat Treatment Time (열처리 시간에 따른 중적외선 투과 ZnS 세라믹의 합성과 특성)

  • Kwon, Tae-Hyeong;Yeo, Seo-Yeong;Park, Chang-Sun;Kim, Chang-Il;Hong, Youn-Woo;Paik, Jong-Hoo
    • Journal of Sensor Science and Technology
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    • v.26 no.5
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    • pp.360-365
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    • 2017
  • In this study, a heat treatment process was applied to ZnS nano-powder to improve the optical properties of ZnS ceramic, and the characteristics of heat treatment time were studied. The ZnS nano-powders were synthesized by hydrothermal synthesis. The heat treatment was carried out at $550^{\circ}C$ for 0.5, 1, 2, and 4 hours in a vacuum atmosphere ($10^{-2}torr$). X-ray diffraction and scanning electron microscope analyzes confirmed the change of crystal phase and grain size to confirm the structural change with heat treatment time. The heat treated ZnS nano-powder was sintered by hot pressing, and the change of optical properties of the ZnS ceramic was analyzed by infrared spectroscopy.

Pentacene Thin Film Transistors with Various Polymer Gate Insulators

  • Kim, Jae-Kyoung;Kim, Jung-Min;Yoon, Tae-Sik;Lee, Hyun-Ho;Jeon, D.;Kim, Yong-Sang
    • Journal of Electrical Engineering and Technology
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    • v.4 no.1
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    • pp.118-122
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    • 2009
  • Organic thin film transistors with a pentacene active layer and various polymer gate insulators were fabricated and their performances were investigated. Characteristics of pentacene thin film transistors on different polymer substrates were investigated using an atomic force microscope (AFM) and x-ray diffraction (XRD). The pentacene thin films were deposited by thermal evaporation on the gate insulators of various polymers. Hexamethyldisilazane (HMDS), polyvinyl acetate (PVA) and polymethyl methacrylate (PMMA) were fabricated as the gate insulator where a pentacene layer was deposited at 40, 55, 70, 85, 100 oC. Pentacene thin films on PMMA showed the largest grain size and least trap concentration. In addition, pentacene TFTs of top-contact geometry are compared with PMMA and $SiO_2$ as gate insulators, respectively. We also fabricated pentacene TFT with Poly (3, 4-ethylenedioxythiophene)-Polysturene Sulfonate (PEDOT:PSS) electrode by inkjet printing method. The physical and electrical characteristics of each gate insulator were tested and analyzed by AFM and I-V measurement. It was found that the performance of TFT was mainly determined by morphology of pentacene rather than the physical or chemical structure of the polymer gate insulator

Composition Dependence on Structural and Optical Properties of MgxZn1-xO Thin Films Prepared by Sol-Gel Method

  • Kim, Min-Su;Noh, Keun-Tae;Yim, Kwang-Gug;Kim, So-A-Ram;Nam, Gi-Woong;Lee, Dong-Yul;Kim, Jin-Soo;Kim, Jong-Su;Leem, Jae-Young
    • Bulletin of the Korean Chemical Society
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    • v.32 no.9
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    • pp.3453-3458
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    • 2011
  • The $Mg_xZn_{1-x}O$ thin films with the various content ratio ranging from 0 to 0.4 were prepared by sol-gel spincoating method. To investigate the effects of content ratio on the structural and optical properties of the $Mg_xZn_{1-x}O$ thin films, scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out. With increase in the content ratio, the grain size of the $Mg_xZn_{1-x}O$ thin films was increased, however, at the content ratio above 0.2, MgO particles with cubic structure were formed on the surface of the $Mg_xZn_{1-x}O$ thin films, indicating that the Mg content exceeded its solubility limit in the thin films. The residual stress of the $Mg_xZn_{1-x}O$ thin films is increased with increase in the Mg mole fraction. In the PL investigations, the bandgap and the activation energy of the $Mg_xZn_{1-x}O$ thin films was increased with the Mg mole fraction.

A Feasibility Study of Nano-grained ZnO Piezoelectric Thin Film Fabrication

  • Zhang, Ruirui;Lee, Eun-Ju;Yoon, Gi-Wan
    • Journal of information and communication convergence engineering
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    • v.7 no.4
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    • pp.530-534
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    • 2009
  • C-axis-oriented ZnO thin films were successfully deposited on p-Si (100) in an RF magnetron sputtering system. Deposition conditions such as deposition power, working pressure, and oxygen gas ratio $O_2/(O_2+Ar)$ were varied. Crystalline structures of the deposited ZnO films were investigated by a scanning electron microscope (SEM) technique. Results show that the deposition parameters can have a strong impact on the preferred orientations and grain sizes of the deposited ZnO films.

Mitigation Methods of Sn Whisker Growth on Pure Sn Plating (순 Sn 도금에서의 Sn 휘스커 성장제어 기술)

  • Kim, Keun-Soo
    • Journal of Welding and Joining
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    • v.31 no.3
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    • pp.17-21
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    • 2013
  • Sn whiskers are one of the serious causes of the failure of electronics. Sn whiskers grow spontaneously from Sn-based, lead-free finished surfaces, even at room temperature. A primary factor of these Sn whiskers growth is compressive stress, which enhances the diffusion of Sn or other elements. The sources of compressive stress are the growth of non-uniform large intermetallic compounds along the interface between the Sn grain boundary and Cu substrate. Recent studies revealed the methods for reducing Sn whisker growth. This paper gives an overview about recent researches for mitigation methods of Sn whisker growth during nearly room temperature storage.

Effects of the Electroplating Duration on the Mechanical Property of the Ni-Co-SiC Composite Coatings

  • Kim, Sung-Min;Lee, Hong-Kee
    • Journal of the Korean institute of surface engineering
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    • v.43 no.6
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    • pp.255-259
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    • 2010
  • In this work, Ni-Co composites incorporated with nano-sized SiC particles in the range of 45-55 nm are prepared by electroplating. The effects of plating duration on the chemical composition, surface morphology, crystalline structures and hardness have been studied. The maximum hardness of Ni-Co-SiC composite coating is approximately 633 Hv at plating duration of 1 h. The hardness is gradually decreased with increasing plating duration, which can be attributed to the growth of crystalline size and the agglomerates of SiC nano-particles. It is therefore explained that the grain refinement of Ni-Co matrix and stable dispersion of SiC particles play an important role for strengthening, which indicate Hall-Petch relation and Orowan model were dominant for hardening of Ni-Co-SiC composite coatings.

A Study on Deformation Behavior of the Grain-Size Controlled Rheology Material by Using Nanoindenter and AFM (나노인덴터와 원자력간 현미경을 이용한 결정립 제어 레오로지 소재의 변형거동에 관한 연구)

  • 윤성원;김정원;강충길
    • Transactions of Materials Processing
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    • v.13 no.4
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    • pp.374-381
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    • 2004
  • In this study, the deformation behavior of semi-solid Al-Si alloy was investigated by nanoindenter as a part of the research on the surface crack behavior in thixoformed automobile component. The microstructure of semi-solid Al-Si alloy consists of primary and eutectic regions. In eutectic regions the crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. Nano-deformation characteristics in the eutectic and primary phase of semi-solid aluminium alloy were investigated through the nano-indentation experiments and the AFM observation. In addition, mechanical properties of each region were investigated and compared with each other.