• Title/Summary/Keyword: Dominant Properties

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Effects of Solution Treatment Temperatures on Microstructure and Mechanical Properties of TIG-MIG Hybrid Arc Additive Manufactured 5356 Aluminum Alloy

  • Zuo, Wei;Ma, Le;Lu, Yu;Li, Shu-yong;Ji, Zhiqiang;Ding, Min
    • Metals and materials international
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    • v.24 no.6
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    • pp.1346-1358
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    • 2018
  • A novel additive manufacturing method with TIG-MIG hybrid heat source was applied for fabricating 5356 aluminum alloy component. In this paper the microstructure evolution, mechanical properties and fracture morphologies of both as-deposited and heat-treated component were investigated, and how these were affected by different heat-treated temperature. The as-deposited microstructure showed dominant equiaxed grains with second phase, and the size of them is coarse in the bottom region, medium in the middle region and fine in the top region owing to different thermal cycling conditions. Compared with as-deposited microstructure, the size of grain becomes large and second phases gradually dissolve in the matrix as heat-treated temperature increase. Different microstructures determine the mechanical properties of component. Results show that average ultimate tensile strength enhances from 226 to 270 MPa and average microhardness increases from 64.2 to 75.3 HV0.1 but ductility decreases from 33 to 6.5% with heat-treated temperature increasing. For all components, the tensile properties are almost the same in the vertical direction (Z) and horizontal direction (Y) due to equiaxed grains, which exhibits isotropy, and the mechanisms of these are analyzed in detailed. In general, the results demonstrate that hybrid arc heat source has the potential to fabricate aluminum alloy component.

Comparison of physicochemical properties of several tomato varieties (토마토 품종에 따른 과실의 이화학적 특성의 비교)

  • Park, Sang-Wook
    • Applied Biological Chemistry
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    • v.36 no.2
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    • pp.115-120
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    • 1993
  • For the elucidation of some information on processing properties of tomato, physicochemical characteristics of fruits were analysed for two group of cultivation pattern, non-proped cultivation (5 varieties) and groped cultivation (4 varieties). Weight, length, width, thickness and specific gravity were greater in the groped cultivation group than in the non-groped. Among the groped varieties, Master 2 showed the greatest values and 76Mo11-3-1-2-2 the smallest. Among the non-groped, weight, length, width and specific gravity were greatest in Jinhong and thickness was greatest in Good Hope and smallest in $79078{\times}ARC$. Hardness showed significant difference only among the non-groped resulting in the lowest value in $79078{\times}ARC$. Fruit sphericity was greater in the non-groped among which Good Hope was the greatest. In fruit color the non-groped showed greater trend in dominant wavelength, especially in Good Hope. No significant difference between group was found in lightness and % chroma. Sugar content showed higher trend in the non-groped and highest in Master 2. Acidity was significantly higher in the non-groped and highest in Good Hope. There was no difference in pH. Vitamin C was difference between group but higher trend in $79078{\times}ARC$. Viscosity was no difference between group but higher trend in $79078{\times}CL1561F6$ of the non-groped and 76Mo11-3-1-2-2-of the groped.

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Exchange Decoupling Of $Fe_3$Fe_3B+Nd_2Fe_{14}B Spring Magnet Powder Compact (Fe_3B+Nd_2Fe_{14}B Spring magnet분말 압분체의 Exchange Decoupling)

  • 한종수;양충진;박언병
    • Journal of the Korean Magnetics Society
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    • v.11 no.5
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    • pp.232-238
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    • 2001
  • Experimentally it is well known that the magnetic properties significantly deteriorate when nanocomposite bonded magnet are made from nanocomposite ribbon. A decrease in maximum energy product of F $e_3$B+N $d_2$F $e_{14}$B nanocomposite from 14 MGOe in nanocomposite ribbon to 6.5 MGOe in powder compact was fecund to be general. Thus, the present study is focused on finding out the root of exchange decoupling of N $d_4$F $e_{73.5}$ $Co_3$H $f_{0.5}$G $a_{0.5}$ $B_{18.5}$ nanocomposite powder compacts. The exchange decoupling behavior of the powder compact of F $e_3$B+N $d_2$F $e_{14}$B composition was studied by measuring DC demagnetization and isothermal remanent demagnetization curves, which are essential for plotting produced $\delta$M curve. From the $\delta$M plot the deterioration in the magnetic properties resulted from the fact that the magnetostatic interaction became dominant rather thanthe exchange interaction in powder compact. It is concluded that the demagnetization behavior governed by the dominant magnetostatic interaction reduced the remanence magnetization, which caused the reduction of maximum energy Product of the powder compact. We also found that the elimination of residual stress which is unavoidably accumulated during grinding process enhanced the magnetic properties considerably.bly.bly.

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The Moisture Absorption Properties of Liquid Type Epoxy Molding Compound for Chip Scale Package According to the Change of Fillers (충전재 변화에 따른 Chip Scale Package(CSP)용 액상 에폭시 수지 성형물 (Epoxy Molding Compound)의 흡습특성)

  • Kim, Whan-Gun
    • Journal of the Korean Chemical Society
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    • v.54 no.5
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    • pp.594-602
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    • 2010
  • Since the requirement of the high density integration and thin package technique of semiconductor have been increasing, the main package type of semiconductor will be a chip scale package (CSP). The changes of diffusion coefficient and moisture content ratio of epoxy resin systems according to the change of liquid type epoxy resin and fillers for CSP applications were investigated. The epoxy resins used in this study are RE-304S, RE310S, and HP-4032D, and Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The micro-sized and nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these epoxy molding compound (EMC) according to the change of filler size. The temperature of glass transition (Tg) of these EMC was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these EMC according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these EMC were calculated in terms of modified Crank equation based on Ficks' law. An increase of diffusion coefficient and maximum moisture absorption ratio with Tg in these systems without filler can be observed, which are attributed to the increase of free volume with Tg. In the EMC with filler, the changes of Tg and maximum moisture absorption ratio with the filler content can be hardly observed, however, the diffusion coefficients of these systems with filler content show the outstanding changes according to the filler size. The diffusion via free volume is dominant in the EMC with micro-sized filler; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the EMC with nano-sized filler.

Structural, Electrical and Magnetic Properties of Wide Bandgap Diluted Magnetic Semiconductor CuAl1-xMnxO2 Ceramics (널은 띠간격 묽은 자성반도체 CuAl1-xMnxO2 세라믹스의 구조 및 전자기 특성)

  • Ji Sung Hwa;Kim Hyojin
    • Korean Journal of Materials Research
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    • v.14 no.8
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    • pp.595-599
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    • 2004
  • We investigated the structural, electrical and magnetic properties of Mn-doped $CuAlO_2$ delafossite ceramics ($CuAl_{1-x}Mn_{x}O_2,\;0\le\;x\;\le0.05$), synthesized by solid-state reaction method in an air atmosphere at a sintering temperature of $1150^{\circ}C$. The solubility limit of Mn ions in delafossite $CuAlO_2$ was found to be as low as about 3 $mol\%$. Positive Hall coefficient and the temperature dependence of conductivity established that non-doped $CuAlO_2$ ceramic is a variable-range hopping p-type semiconductor. It was found that the Mn-doping in $CuAlO_2$ rapidly reduced the hole concentration and conductivity, indicating compensation of free holes. The analysis of the magnetization data provided an evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Mn ions in $CuAl_{1-x}Mn_{x}O$ alloy, leading to an almost paramagnetic behavior in this alloy.

On Flexibility in Architecture Focused on the Contradiction in Designing Flexible Space and Its Design Proposition

  • Kim, Young-Ju
    • Architectural research
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    • v.15 no.4
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    • pp.191-200
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    • 2013
  • Since Modern Movement flexibility has been one of the most attractive words in architecture. However, "overprovision first, division later" has been the most prevailing design method for spatial flexibility, and many of buildings designed for flexible use are practically quite inflexible due to insufficient building systems or/and irresponsible planning. There have been two dominant strategies to achieve architectural flexibility: multi-functionality and polyvalence. These two approaches, which point contradictory directions, actually reflect the difficulty in providing a proper form of architectural flexibility. Multi-functionality can afford changeable environments with satisfying spatial conditions; however it lacks tolerance to accommodate other uses but intended functions by architects. Meanwhile, flexibility by a polyvalent form relies on the vague anticipation of user's various interpretations. In this study by looking up these two different standpoints and historical precedents flexibility in architecture is carefully scrutinized focused on the contradiction, and as an alternative for architectural flexibility contextual relations is proposed. Unlike both multi-functionality and polyvalence, which produce flexibility by changing its own properties, manipulating contextual relations infuses flexibility into space by changing the properties of a building, not of its individual room. By using this contextual relations method, a community-centered school in Manhattan, NY, which was in danger of being closed because of its academic failure, is represented as a flexible space.

COMPARISON OF PHYSICAL PROPERTIES AND EVOLUTION OF AKARI AND SPITZER 24 ㎛-DETECTED GALAXIES AT z = 0.4 - 2

  • Fujishiro, Naofumi;Hanami, Hitoshi;Ishigaki, Tsuyoshi
    • Publications of The Korean Astronomical Society
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    • v.32 no.1
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    • pp.313-315
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    • 2017
  • We present physical properties of $24{\mu}m$ galaxies detected by AKARI and Spitzer and their evolution between redshifts 0.4 < z < 2. Using multi-wavelength data from X-ray to radio observations in NEP Deep Field (for AKARI) and Subaru/XMM-Newton Deep Field (for Spitzer), we derive photometric redshift, stellar mass, star-formation rate (SFR), dust extinction magnitude and rest-frame luminosities/colors of the $24{\mu}m$ galaxies from photometric SED fitting. We infer the SFRs from rest-frame ultraviolet luminosity and total infrared luminosity calibrated against Herschel photometric data. For both survey fields, we obtain complete samples with stellar mass of > $10^{10}M_{\odot}$ and SFR of > $30M_{\odot}/yr$ up to z = 2. We find that specific SFRs evolves with redshift at all stellar masses in NON-power-law galaxies (non-PLGs) as star-formation dominant luminous infrared galaxies (LIRGs). The correlations between specific SFR and stellar mass in the Spitzer and AKARI galaxy samples are well consistent with trends of the main sequence galaxies. We also discuss nature of PLGs and their evolution.

TiO2@carbon Core-Shell Nanostructure Electrodes for Improved Electrochemical Properties in Alkaline Solution

  • Kim, Do-Young;Lee, Young-Woo;Han, Sang-Beom;Ko, A-Ra;Kim, Hyun-Su;Kim, Si-Jin;Oh, Sang-Eun;Park, Kyung-Won
    • Journal of the Korean Electrochemical Society
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    • v.15 no.2
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    • pp.90-94
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    • 2012
  • We report nanostructure electrodes with $TiO_2$ as a core and carbon as a shell ($TiO_2$@C) for oxygen reduction in alkaline solution. The structure of core-shell electrodes is characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction method, and X-ray photoelectron microscopy. The electrochemical properties of the $TiO_2$@C electrodes are characterized using a potentiostat and compared with those of carbon supported Pt catalyst. In particular, the core-shell electrode with dominant pyridinic-N component exhibits an imporved electrocatalytic activity for oxygen reduction reaction in alkaline solution.

Effect of Aging Treatment on the Microstructure and Mechanical Properties of Mg-6Al-xZn (x : 1.5, 2.5) Alloys Fabricated by Squeeze Casting (용탕단조된 Mg-6Al-xZn (x=1.5, 2.5) 합금(合金)의 미세조직 및 기계적 성질에 미치는 시효의 영향)

  • Kim, Soon Ho
    • Journal of the Korean Society for Heat Treatment
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    • v.12 no.1
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    • pp.1-8
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    • 1999
  • This study has investigated the effect of aging treatment on the microstructure and mechanical properties of Mg-6Al-xZn(x = 1.5, 2.5) alloys fabricated by the squeeze casting process. The microstructures of as-squeeze cast were composed of pro-eutectic ${\alpha}$, super saturated ${\alpha}$ and ${\beta}(Mg_{17}Al_{12})$ compound. Aged at both $200^{\circ}C$ and $240^{\circ}C$, Mg-6Al-xZn alloys showed the peak hardness due to the formation of ${\beta}(Mg_{17}Al_{12})$ precipitates. The discontinuous precipitates of the lamella type are predominant at $200^{\circ}C$ aging treatment, while the finely dispersed continuous precipitates were dominant at $240^{\circ}C$ aging treatment. Mg-6Al-xZn alloys fabricated by the squeeze casting process had the better combination of tensile strength and elongation compared to the conventionally cast alloys. As zinc contents increased, the tensile strength was increased by the solid solution strengthening effect of zinc.

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Facile Synthesis of SrWO4:Eu3+ Phosphors

  • Bharat, L. Krishna;Yu, Jae Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.643-643
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    • 2013
  • Recently, synthesis of low-dimensional nanostructures is gaining more importance due to their structural properties and growing potential applications. On the other hand, luminescent materials doped with rare earth ions have drawn immense attention. The commercial phosphors are based on many host materials. Among them, tungstates are being currently investigated by many research groups owing to a wide range of applications. Tungstates are formed by different metal cations (e.g., SrWO4, Na2WO4, NiWO4, Cr2WO6, and ZrW2O8) and their structure depends on the size of the metal cation. Tungstates with large bivalent cations (${\gg}0.1\;nm$) have the scheelite structure and the wolframite structure with smaller ions (<0.1 nm). Strontium tungstate has the scheelite structure which is tetragonal with space group I41/a. The luminescent properties of the tungstate have been extensively explored in application fields such as sensors, detectors, lasers, photoluminiscent devices, photo catalysts, etc. In this work, we synthesized SrWO4 phosphors with different Eu3+ concentrations by using a facile route. The morphology was analyzed by using a field-emission scanning electron microscope, which exhibits the spherical shape. Transmission electron microscope image revealed the spheres composed of nanoparticles. X-ray diffraction patterns confirmed their tetragonal shape. The photoluminescence excitation and emission spectra were analyzed by varying the Eu3+ concentration, which shows a dominant red emission.

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