• Title/Summary/Keyword: SI7

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Study on Grain Refinement of Al-7Si Based Alloys with TiC (Al-7Si 합급의 결정립 미세화에 미치는 TiC 첨가의 영향)

  • Han, Yun-Sung;Choi, Chang-Ock
    • Journal of Korea Foundry Society
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    • v.23 no.2
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    • pp.63-68
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    • 2003
  • Al-Ti-C grain refiner form a relatively new alternative to the existing class of Al-Ti-B type grain refiners for achieving fine equiaxed structures in aluminum alloys during casting and solidification. The present study was carried out to investigate the influence of Al-Ti-C master alloys on the grain structure of Al-7Si alloys. The present study also investigates the relationship between grain refining efficiency and concentrations of Fe and Si in hypo-eutectic Al-Si alloys using Al-3Ti-0.13C master alloys. It is found that several parameters affect significantly the grain refining performance in silumin alloys. The present study reports the influence of various parameters such as alloy content, master alloy addition level, melt holding time and superheat on the grain refining efficiency in Al-7Si alloys.

A study on the squeeze casting of Al-7.0Si-0.4Mg alloy for fuel system parts

  • Kim Soon-Ho;Kim Seong-Soo
    • International Journal of Precision Engineering and Manufacturing
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    • v.6 no.3
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    • pp.56-59
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    • 2005
  • Aluminum alloy casting is gaining increased acceptance in automotive and electronic industries and especially, squeeze casting is the most efficient method of mass manufacturing of such parts. In this study, the microstructures and mechanical properties of Al-7.0Si-0.4Mg(AC4C) alloy fabricated by squeeze casting process for development of fuel system parts (fuel rail) are investigated. The microstructure of squeeze cast specimen was composed of eutectic structure aluminum solid solution and $Mg_2Si$ precipitates. The tensile strength of as-solid solution treatment Al-7.0Si-0.4Mg alloy was 298.5MPa. It was found that Al-7.0Si-0.4Mg alloy had good corrosion resistance in electrochemical polarization test.

Epitaxial Growth of Ge on Si(100) and Si(111) Surfaces (Si(100)와 Si(111) 표면의 Ge 에피 성장 연구)

  • Khang, Yun-Ho;Kuk, Young
    • Journal of the Korean Vacuum Society
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    • v.2 no.2
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    • pp.161-165
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    • 1993
  • The geometrical and electronic structure of epitaxially grown Ge on Si(100) and Si(111) surfaces has been studied by scanning tunneling microscopy. Since Ge atoms could be distinguished from Si atoms by scanning tunneling spectroscopy and voltage dependent STM images, the growth mode of the added layer could be studied. On the (100) surface with a (2${\times}$1) reconstruction, Ge overlayer grow preferentially on the B type step edges at 720K. On the (111) surface, Ge overlayer also grow on the step edges with (7${\times}$7) and (5${\times}$5) structure depending on their coverage and annealing temperature.

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A Study on The Optimal Design of SiC Ceramic Heater (SiC계 세라믹 발열체의 최적 설계에 관한 연구)

  • Cho, Hyun-Seob
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.7
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    • pp.1631-1634
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    • 2009
  • Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites. Temperature rising time of sheath heater is 1.1 times faster than SiC ceramic heater. Heating insulation of SiC ceramic heater is 2.7 times larger than sheath heater. If SiC ceramic heater is one body type of a product application, contact resistance will decrease. I think that temperature initial rising time is faster than now. The more SiC ceramic heater is used for a long time, the more economic benefit is larger in the view point of heat insulation.

Grain Orientation and Electrical Properties of $Sr_2Nb_2O_7$ Ceramics and Thin Films (다결정 및 박막형 $Sr_2Nb_2O_7$의 입자배향과 전기적특성)

  • 손창헌;전상재;남효덕;이희영
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.4
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    • pp.274-280
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    • 1998
  • Polycrystalline $Sr_2Nb_2O_7$ ceramics with very high Curie temperature were sintered using the powder derived by the chemical coprecipitation method (CCP). The phase evolution and grain-orientation of sintered samples were examined by XRD, while sintering behavior, dielectric properties and polarization were studied by SEM and ferroelectric tester. Extremely high degree of grain-orientation was observed along the (0k0) direction, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal. Thin film fabrication of $Sr_2Nb_2O_7$ in the pyroniobate family was also attempted on $SiO_2$/Si(100), Pt/$SiO_2$/Si(100), Pt/Ti/$SiO_2$/Si(100) and Pt/$ZrO_2/SiO_2/Si_2(100)$ substrates, using metalorganic decomposition (MOD) process. Neodecanoate precursor solution was prepared by mixing strontium neodecanoate with niobium neodecanoate synthesized from niobium ethoxide. It was found that $Sr_2Nb_2O_7$ single phase appeared in XRD patterns the samples annealed above $950^{\circ}C$. The effect of substrate type on film microstructure and dielectric properties was observed.

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Co-deposition of Si Particles During Electrodeposition of Fe in Sulfate Solution (황산철 도금액 중 Si 입자의 공석 특성)

  • Moon Sung-Mo;Lee Sang-Yeal;Lee Kyu-Hwan;Chang Do-Yon
    • Journal of the Korean institute of surface engineering
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    • v.37 no.6
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    • pp.319-325
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    • 2004
  • Fe thin films containing Si particles were prepared on metallic substrates by electrodeposition method in sulfate solutions and the content of codeposited Si particles in the films was investigated as a function of applied current density, the content of Si particels in the solution, solution pH, solution temperature and concentration of $FeSO_4$$7H_2$O in the solution. The amount of Si codeposited in the film was not dependent on the applied current density, solution pH and solution temperature, while it was dependent on the content of Si particles in the solution and the concentration of $FeSO_4$$7H_2$O in the solution. The amount of Si codeposited in the film increased with increasing content of Si particles in the solution but reached a maximum value of about 6 wt% when the content of Si particles in the solution exceeds 100 g/l. On the other hand, the content of Si codeposited in the film increased up to about 17 wt% with decreasing concentration of $FeSO_4$$7H_2$O in the solution. These results would be applied to the fabrication of very thin Fe-6.5 wt% Si sheets for electrical applications.

IR Study on the Adsorption of Carbon Monoxide on Silica Supported Ruthenium-Nickel Alloy (실리카 지지 루테늄-니켈 합금에 있어서 일산화탄소의 흡착에 관한 IR 연구)

  • Park, Sang-Youn;Yoon, Dong-Wook
    • Applied Chemistry for Engineering
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    • v.17 no.4
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    • pp.349-356
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    • 2006
  • We have investigated adsorption and desorption properties of CO adsorption on silica supported Ru/Ni alloys at various Ru/Ni mole content ratio as well as CO partial pressures using Fourier transform infrared spectrometer (FT-IR). For Ru-$SiO_{2}$ sample, four bands were observed at $2080.0cm^{-1}$, $2021.0{\sim}2030.7cm^{-1}$, $1778.9{\sim}1799.3cm^{-1}$, $1623.8cm^{-1}$ on adsorption and three bands were observed at $2138.7cm^{-1}$, $2069.3cm^{-1}$, $1988.3{\sim}2030.7cm^{-1}$ on vacumn desorption. For Ni-$SiO_{2}$ sample, four bands were observed at $2057.7cm^{-1}$, $2019.1{\sim}2040.3cm^{-1}$, $1862.9{\sim}1868.7cm^{-1}$, $1625.7cm^{-1}$ on adsorption and two bands were observed at $2009.5{\sim}2040.3cm^{-1}$, $1828.4{\sim}1868.7cm^{-1}$ on vacumn desorption. These absorption bands correspond with those of the previous reports approximately. For Ru/Ni(9/1, 8/2, 7/3, 6/4, 5/5; mole content ratio)-$SiO_{2}$ samples, three bands were observed at $2001.8{\sim}2057.7cm^{-1}$, $1812.8{\sim}1926.5cm^{-1}$, $1623.8{\sim}1625.7cm^{-1}$ on adsorption and three bands were observed at $2140.6cm^{-1}$, $2073.1cm^{-1}$, $1969.0{\sim}2057.7cm^{-1}$ on vacumn desorption. The spectrum pattern observed for Ru/Ni-$SiO_{2}$ sample at 9/1 Ru/Ni mole content ratio on CO adsorption and on vacumn desorption is almost like the spectrum pattern observed for Ru-$SiO_{2}$ sample. But the spectrum patterns observed for Ru/Ni-$SiO_{2}$ samples under 8/2 Ru/Ni mole content ratio on CO adsorption and vacumn desorption are almost like the pattern observed for $Ni-SiO_{2}$ sample. It may be suggested surfaces of alloy clusters on the Ru/Ni-$SiO_{2}$ samples contain more Ni components than the mole content ratio of the sample considering the above phenomena. With Ru/Ni-$SiO_{2}$ samples the absorption band shifts may be ascribed to variations of surface concentration, strain variation due to atomic size difference, variation of bonding energy and electronic densities, and changes of surface geometries according to surface concentration variation. Studies for CO adsorption on Ru/Ni alloy cluster surface by LEED and Auger spectroscopy, interation between Ru/Ni alloy cluster and $SiO_{2}$, and MO calculation for the system would be needed to look into the phenomena.

Effects of Mn, Cr, and Sr Additions on the Microstructure and Tensile Properties of Al-7Si-0.4Mg-1Fe Casting Alloy (Al-7Si-0.4Mg-1Fe 주조합금의 미세조직과 인장성질에 미치는 Mn, Cr 및 Sr 첨가의 영향)

  • Kim, Jeong-Min;Park, Joon-Sik;Kim, Ha-Young;Cho, Jae-Ik;Jung, Chang-Yeol
    • Journal of Korea Foundry Society
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    • v.29 no.1
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    • pp.27-32
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    • 2009
  • The microstructure of Al-7Si-0.4Mg-1Fe alloy mainly consists of aluminum dendrites, Al-Si eutectics, and $Al_5FeSi$ needles. When Mn was added to the alloy, the substantial amount of $Al_5FeSi$ phase was changed into Al(Mn,Fe)Si, however the needle-like morphology was almost unchanged. Combined additions of Cr or Sr with Mn to the base alloy resulted in rod-like Al(Mn, Fe,Si)Si phase. The tensile properties of as-cast alloys were enhanced by the Mn addition, especially when it was added with Sr. The tensile properties after T6 heat treatment was a little improved with 0.7%Mn addition, but Cr or Sr additions with Mn didn't show any positive effect on the properties of heat-treated alloys.

The study of In/Si(111) surface by variation of RHEED spot intensity (RHEED회절점의 강도변화에 따른 In/Si(111)에 대한 연구)

  • 곽호원;이의완;박동수;이운환
    • Journal of the Korean Vacuum Society
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    • v.6 no.2
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    • pp.172-176
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    • 1997
  • The change of surface structures for the deposition of indium on clean Si(111) surface is investigated as a function of substrate temperature and surface coverage by RHEED. We find that at substrate temperature of $400^{\circ}C$, $\sqrt{3}\times\sqrt{3},\sqrt{31}\times\sqrt{31},4\times 1$ structures are formed at indium coverages of 0.2, 0.3 and 0.5 ML, respectively. We also find that for the substrate temperature of $300^{\circ}C$, 4$\times$1 structure starts to be forme by 0.2 ML of indium, and the mixed structure of 4$\times$1 and $\sqrt{3}\times\sqrt{3}$is observed for more than 1.0 ML. On the other hand, if the indium is deposited on the Si(111)-$\sqrt{3}\times\sqrt{3}$ structure at room temperature, $2\times2\; and\;\sqrt{7}\times\sqrt{3}$ structures are found to form at 0.2 and 0.4 ML, respectovely. From the desorption process, the desorption energy of indium in Si $\sqrt{7}\times\sqrt{3}$ structure is observed to be 2.84 eV.

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Effect of Solution Treatment Conditions on the Microstructure and Hardness Changes of Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu Alloys (Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu 합금의 미세조직 및 경도 변화에 미치는 용체화 처리 조건의 영향)

  • Sung-Bean Chung;Min-Su Kim;Dae-Up Kim;Sung-Kil Hong
    • Journal of Korea Foundry Society
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    • v.42 no.6
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    • pp.337-346
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    • 2022
  • In order to optimize the solution treatment conditions of Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu alloys, a series of heat treatment experiments were conducted under various solution treatment times up to 7 hours at 545℃, followed by a microstructural analysis using optical microscopy, FE-SEM, and Brinell hardness measurements. Rapid coarsening of eutectic Si particles was observed in the alloys during the first 3 hours of solution treatment but the size of those Si particles did not change at longer solution treatment conditions. Meanwhile, the degree of spheroidisation of eutectic Si particles increased until the solution treatment time was increased up to 7 hours. Q-Al5Cu2Mg8Si6 andθ-Al2Cu were observed in as-cast Cu-containing Al alloys but the intermetallic compounds were dissolved completely after 3 hours of solution treatment at 545℃. Depending on the initial Mg composition of the Al alloys, π-Al8FeMg3Si either disappeared in the alloy with 0.3wt% of Mg content after 5 hours of solution treatment or remained in the alloy with 0.5wt% of Mg content after 7 hours of solution treatment time. Mg and Cu content in the primary-α phase of the Al alloys increased until the solution treatment time reached 5 hours, which was in accordance with the dissolution behavior of Mg or Cu-containing intermetallic compounds with respect to the solution treatment time. From the results of microstructural changes in the Al-7Si-Mg-Cu alloys during solution treatment, it was concluded that at least 5 hours of solution treatment at 545℃ is required to maximize the age hardening effect of the present Al alloys. The same optimal solution treatment conditions could also be derived from Brinell hardness values of the present Al-7Si-Mg-Cu alloys measured at different solution treatment conditions.