• Title, Summary, Keyword: microstructure

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Microstructure and Electrical Resistivity of Ink-Jet Printed Nanoparticle Silver Films under Isothermal Annealing (잉크젯 프린팅된 은(Ag) 박막의 등온 열처리에 따른 미세조직과 전기 비저항 특성 평가)

  • Choi, Soo-Hong;Jung, Jung-Kyu;Kim, In-Young;Jung, Hyun-Chul;Joung, Jae-Woo;Joo, Young-Chang
    • Korean Journal of Materials Research
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    • v.17 no.9
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    • pp.453-457
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    • 2007
  • Interest in use of ink-jet printing for pattern-on-demand fabrication of metal interconnects without complicated and wasteful etching process has been on rapid increase. However, ink-jet printing is a wet process and needs an additional thermal treatment such as an annealing process. Since a metal ink is a suspension containing metal nanoparticles and organic capping molecules to prevent aggregation of them, the microstructure of an ink-jet printed metal interconnect 'as dried' can be characterized as a stack of loosely packed nanoparticles. Therefore, during being treated thermally, an inkjet-printed interconnect is likely to evolve a characteristic microstructure, different from that of the conventionally vacuum-deposited metal films. Microstructure characteristics can significantly affect the corresponding electrical and mechanical properties. The characteristics of change in microstructure and electrical resistivity of inkjet-printed silver (Ag) films when annealed isothermally at a temperature between 170 and $240^{\circ}C$ were analyzed. The change in electrical resistivity was described using the first-order exponential decay kinetics. The corresponding activation energy of 0.44 eV was explained in terms of a thermally-activated mechanism, i.e., migration of point defects such as vacancy-oxygen pairs, rather than microstructure evolution such as grain growth or change in porosity.

Microstructure Generation and Linearly Elastic Characteristic Analysis of Hierarchical Models for Dual-Phase Composite Materials (이종 입자복합재의 미세구조 생성과 계층적 모델의 선형 탄성적 응답특성 해석)

  • Cho, Jin-Rae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.3
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    • pp.133-140
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    • 2018
  • This paper is concerned with the 2-D micostructure generation for $Ni-A{\ell}_2O_3$ dual-phase composite materials and the numerical analysis of mechanical characteristic of hierarchical models of microstructure which are defined in terms of the scale of microstructure. The microstructures of dual-phase composite materials were generated by applying the mathematical RMDF(random morphology description functions) technique to a 2-D RVE of composite materials. And, the hierarchical models of microstructure were defined by the number of Gaussian points. Meanwhile, the volume fractions of metal and ceramic particles were set by adjusting the level of RMD functions. The microstructures which were generated by RMDF technique are definitely random even though the total number of Gaussian points is the same. The randomly generated microstructures were applied to a 2-D beam model, and the variation of normal and shear stresses to the scale of microstructure was numerically investigated. In addition, through the crack analyses, the influence of RMDF randomness and Gauss point number on the crack-tip stress is investigated.

Rolling of AZ31 Alloy and Microstructure of Rolled Plates (압연조건에 따른 AZ31 마그네슘합금판재의 변형거동 및 미세조직 변화)

  • Ha, T.K.;Jeong, H.T.;Sung, H.J.;Park, W.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.63-66
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    • 2006
  • The effect of warm rolling under various conditions on the microstructure and mechanical property was investigated using an AZ31 Mg alloy sheet. Several processing parameters such as initial thickness, thickness reduction by a single pass rolling, rolling temperature, roll speed, and roll temperature were varied to elicit an optimum condition for the warm rolling process of AZ31 Mg alloy. Microstructure and mechanical properties were measured for specimens subjected to rolling experiments of various conditions. Warm rolling of 30% thickness reduction per pass was possible without any side-crack at temperatures as low as $200^{\circ}C$ under the roll speed of 30 m/min. The initial microstructure before rolling was the mixed one consisting of partially recrystallized and cast structures. Grain refinement was found to occur actively during the warm rolling, producing a very fine grain size of 7 mm after 50% reduction in single pass rolling at $200^{\circ}C$. Yield strength of 204MPa, tensile strength of 330MPa and uniform elongation of 32% have been obtained in warm rolled sheets.

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Process Design and Microstructure Evaluation During Hot Forging of Superalloy Turbine Disk (초내열합금 터빈 디스크의 열간 단조 공정에 대한 공정 설계 및 미세조직 평가)

  • Cha, D.J.;Kim, D.K.;Kim, Y.D.;Bae, W.B.;Cho, J.R.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.190-194
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    • 2007
  • The forging process design and microstructure evolution for gas turbine disk of a Waspaloy is investigated in this study. Parameters related to deformation are die and preform geometry, and forging temperature of die and workpiece. Die and preform design are considered to reduce the forging load, and to avoid the forging defects. Blocker and finisher dies for multistage forging are designed and the initial billet geometry is determined. The control of hot forging parameters such as strain, strain rate and temperature also is important because the microstructure change in hot working affects the mechanical properties. The dynamic recrystallization evolution has been studied in the temperature range 900-$1200^{\circ}C$ and strain rate range 0.01-1.0s-1 using hot compression tests. Modeling equations are required represent the flow curve, recrystallized grain size, recrystallized volume fraction by various tests. In this study, we used to thermo-viscoplastic finite element modeling equation of DEFORM-2D to predict the microstructure change evolution during thermo-mechanical processing. The microstructure is updated during the entire thermal and deformation processes in forging.

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Microstructure and Properties of $Cr_{2}O_{3}$additive ternary PZT Ceramics ($Cr_{2}O_{3}$이 첨가된 PNN-PZT 압전세라믹스에서의 미세구조 및 특성)

  • 박정호;김철수;김성곤;이상렬
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.972-975
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    • 2001
  • The effect of Cr$_2$O$_3$(0 to 0.5 wt%) doping on the microstructure and electrical properties of ternary Pb(Zr,Ti)O$_3$-Pb(Ni,Nb)O$_3$piezoelectric ceramic has been investigated. Abnormal grain growth (grain size 3.3 to 11.2 $\mu$m) and densification are found. Minor additives of $\leq$0.1 wt% improve the mechanical coupling factor, but with more additives of $\geq$0.2 wt% electrical properties deteriorate. Thus, these phenomna can be ascribed mainly to anomalous developed microstructure. The large grains were composed of a core region that is free of Cr and a surrounding shell region rich in Cr. The interfaces between the core and the shell were composed of misfit dislocations. The mechanical properties of the specimens were strongly influenced by this microstructural change. The microstrutural and compositonal evolution of the specimens containing different amounts of Cr$_2$O$_3$were monitored. Electrical properties were measured and related to the variations in the microstructure.

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Fabrication of Multi-stepped Three Dimensional Silicon Microstructure for INS Grade Servo Accelerometer (관성 항법 장치급 서보 가속도계용 다단차 3차원 실리콘 미세 구조물 제작)

  • Yee, Young-Joo;Lee, Sang-Hoon;Chun, Kuk-Jin;Kim, Yong-Kwon;Cho, Dong-Il
    • Proceedings of the KIEE Conference
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    • pp.425-427
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    • 1996
  • New fabrication technique was developed to make three dimensional silicon microstructure with five fold vertical steps through entire wafer thickness. Each step is pre-defined on multiply stacked thermal oxide and silicon nitride (O/N) layers by photolithographies. Multi-stepped silicon microstructure is formed by anisotropic etch in aqueous KOH solution with the patterned nitride film as masking layer. Fabricated microstructure consists of four $16{\mu}m$ thick flexural spring beams, $290{\mu}m$ thick proof mass, mesas for overrange stop with $10{\mu}m$ height from the surface of the proof mass, and the other mesas and V grooves used for assembling this structure to the packaging frame of pendulous servo accelerometer. Using the numerical finite element method (FEM) simulator: ABAQUS, mechanical characteristics of the fabricated microstructure by the developed technique was compared with those of the same structure processed by one step silicon bulk etch followed by oxidation and patterning the etched region.

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Microstructure Characterization of the Solders Deposited by Thermal Evaporation for Flip Chip Bonding (진공 증발법에 의해 제조된 플립 칩 본딩용 솔더의 미세 구조분석)

  • 이충식;김영호;권오경;한학수;주관종;김동구
    • Journal of the Korean institute of surface engineering
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    • v.28 no.2
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    • pp.67-76
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    • 1995
  • The microstructure of 95wt.%Pb/5wt.%Sn and 63wt.%Sn/37wt.%Pb solders for flip chip bonding process has been characterized. Solders were deposited by thermal evaporation and reflowed in the conventional furnace or by rapid thermal annealing(RTA) process. As-deposited films show columnar structure. The microstructure of furnace cooled 63Sn/37Pb solder shows typical lamellar form, but that of RTA treated solder has the structure showing an uniform dispersion of Pb-rich phase in Sn matrix. The grain size of 95Pb/5Sn solder reflowed in the furnace is about $5\mu\textrm{m}$, but the grain size of RTA treated solder is too small to be observed. The microstructure in 63Sn/37Pb solder bump shows the segregation of Pb phase in the Sn rich matrix regardless of reflowing method. The 63Sn/37Pb solder bump formed by RTA process shows more uniform microstructure. These result are related to the heat dissipation in the solder bump.

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The Changes of Microstructure, Morphology, and Mechanical Properties of Solvent Treated PET POY (Partially Oriented Yarn) (폴리에스테르 부분배향사의 용매처리에 따른 내부구조 및 인장성질의 변화)

  • Shin, Hae Won;Ryu, Hyo Seon
    • Journal of the Korean Society of Clothing and Textiles
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    • v.17 no.1
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    • pp.63-75
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    • 1993
  • Partially oriented polyester yarn (PET POY) was treated in the unrestrained state using various solvents at different temperatures. Interactions between PET POY & solvents were estimated by the changes of microstructure, morphology and mechanical properties. The correlation between the changes of microstructure & morphology and the changes of mechanical properties was also studied. TCE, Dioxane, O-DCB, DMF, and BA were found to be active solvents, while Iso-AA and water were found to be weak solvents. PET POY was affected mainly by the solvents when treated with active solvents and affected mainly by heat when treated with weak solvents. Changes by the solvent treatment in microstructure and morphology were : an increase in crystallinity, a change in birefringence, a shrinkage in length, and a change in DSC curve. As for the changes in mechanical properties, findings in the PET POY when treated with solvents were : a decrease in stress-at-break, a change in yield stress, an increase in strain-at-break & yield strain, and a decrease in initial modulus. Changes in microstructure and morphology directly affected the mechanical properties.

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Microstructure Evolution of Superalloy Nimonic 80A (초내열합금 Nimonic 80A의 미세조직 변화에 관한 연구)

  • Jeong H. S.;Cho J. R.;Park H. C.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.174-177
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    • 2004
  • The nickel-based alloy Nimonic 80A possesses strength, and corrosion, creep and oxidation resistance at high temperature. These products are used for aerospace, marine engineering and power generation, etc. The control of forging parameters such as strain, strain rate, temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. It is necessary to understand the microstructure variation evolution. The microstructure change evolution occurs by recovery, recrystallization and grain growth phenomena. The dynamic recrystallization evolution has been studied in the temperature range $950-1250^{\circ}C$ and strain rate range $0.05-5s^{-1}$ using hot compression tests. The metadynamic recrystallization and grain growth evolution has been studied in the temperature range $950-1250^{\circ}C$ and strain rate range 0.05, $5s^{-1}$, holding time range 5, 10, 100, 600 sec using hot compression tests. Modeling equations are developed to represent the flow curve, recrystallized grain size, recrystallized fraction and grain growth phenomena by various tests. Parameters of modeling equation are expressed as a function of the Zener-Hollomon parameter. The modeling equation for grain growth is expressed as a function of initial grain size and holding time.

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