• Title/Summary/Keyword: silicon powder

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A Poling Study on a Piezoceramic/Polymer 0-3 Composites for Hydrophone Applications (Hydrophone 응용을 위한 Piezoceramic/Polymer 0-3 Composite의 분극 개선)

  • Lee, S.H.;Cho, H.C.;SaGong, G.;Seul, S.D.;Koo, H.B.
    • Proceedings of the KIEE Conference
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    • 1989.07a
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    • pp.349-352
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    • 1989
  • Poling piezoelectric ceramic-polymer composites with 0-3connectivity is difficult because of the high dielectric constant of most of the ferroelectric filler materials, and the high resistivity of the polymer matrix. To aid in poling this type of composite, conductivity of the polymer phase can be controlled by adding small amount of a semiconductor phase such as germanium, carbon or silicon. In this study, flexible piezoelectric composites of $PbTiO_3$ powder and Eccogel polymer were developed using small amounts of a semiconducting phase. These composites were poled rapidly at low voltages, resulting in properties superior to composites prepared without a conductive phase. The effect of addition of various conductive phase with different volume percentage on the dielectric and piezoelectric properties of the composite are discussed here.

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Effect of pore size and porosity on electrical breakdown behaviors of $BaTiO_3$ ceramics ($BaTiO_3$ 세라믹의 절연파괴거동에 미치는 기공의 크기와 기공율의 영향)

  • 조경호;우동찬;남효덕;이희영
    • Electrical & Electronic Materials
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    • v.10 no.3
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    • pp.255-261
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    • 1997
  • In this study, pore-containing barium titanate ceramics were prepared with different porosities and pore sizes, in order to better understand how porosity and pore size affect electrical breakdown of barium titanate ceramics. A granulated barium titanate powder was mixed with three grades of commercial polymer microspheres up to 11wt%. The electrical breakdown test was performed at two different temperatures of 30.deg. C(below Tc) and 150.deg. C(above Tc) for samples immersed in a silicon oil bath using a 60kV de power supply. Electrical breakdown strength of pore containing barium titanate ceramics with porosity lower than 10% decreased as pore size and porosity increased. However, above the 10% porosity region, electrical breakdown strength decreased as the pore connectivity increased. From the experimental results, an optimum electrical breakdown model is proposed in an attempt to explain the effect of pores.

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Fabrication of Reaction Sintered SiC Materials by Complex Slurry with Nano Size Particles (나노입자 혼합 복합슬러리를 이용한 반응소결 SiC 재료의 제조)

  • Lee Sang-Pill
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.3 s.234
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    • pp.425-431
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    • 2005
  • The efficiency of complex slurry preparation route for developing the high performance SiC matrix of $RS-SiC_{f}/SiC$ composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of molten silicon were prepared with various C/SiC complex slurries, which associated with both the sizes of starting SiC particles and the blending conditions of starting SiC and C particles. The characterization of Rs-SiC materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the process optimization is also discussed. The flexural strength of Rs-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

Ultra Precision Polishing of Micro Die and Mold Parts using Magnetic-assisted Machining (자기연마법을 응용한 미세금형부품의 초정밀 연마)

  • 안병운;김욱배;박성준;이상조
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1832-1835
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    • 2003
  • This paper suggests the selective ultra precision polishing techniques for micro die and mold parts using magnetic-assisted machining. Fabrication of magnetic abrasive particle and their polishing performance are key technology at ultra precision polishing process of micro parts. Conventional magnetic abrasives have disadvantages. which are missing of abrasive particle and inequality between magnetic particle and abrasive particle. So, bonded magnetic abrasive particles are fabricated by several method. For example, plasma melting and direct bonding. Ferrite and carbonyl iron powder are used as magnetic particle where silicon carbide and Al$_2$O$_3$ are abrasive particle. Developed particles are analyzed using measurement device such as SEM. Possibility of magnetic abrasive and polishing performance of this magnetic abrasive particles also have been investigated. After polishing, surface roughness of workpiece is reduced from 2.927 $\mu\textrm{m}$ Rmax to 0.453 $\mu\textrm{m}$ Rmax.

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A Study on Mixing of Silicon Nitride Fine Powder and Binder System for Ceramic Injection Molding (세라믹 사출성형을 위한 질화규소 미세분말과 결합체 시스템의 혼합에 대한 연구)

  • 윤재륜
    • The Korean Journal of Rheology
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    • v.2 no.1
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    • pp.67-78
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    • 1990
  • 세라믹 분말의 사출성형성을 평가하기 위하여 다양한 혼합체 시스템에 대한 혼합도 와 유변학적 성질을 질화규소 미세분말의 부피비를 변화시키면서 조사하였다. 열가소성 결 합체 시스템은 폴리에틸린 폴리에틸렌 왁스 그리고 미소량의 첨가제를 혼합하여 사용하였 다. 혼합성능을 평가하기 위하여 비분산혼합에서는 총접촉면적비를 그리고 분산혼합에서는 총파괴표면적비를 혼합척도로서 사용하여 정성적으로 모형화하였다. 사용된 혼합기내의 유 동장을 해석하기 위하여 뉴우톤유체를 가정하여 유동해석을 수행하였다. 혼합물의 혼합도는 각각 5분 30분 동안 혼합된 시편을 주사전자현미경 사진에 의해 관찰하여 평가하였다. 또한 혼합물의 사출성형성 그리고 혼합질 점도 토우크 곡선 사이의 관계를 규명하기 위하여 전단 변형를 속도를 따른 점도를 모세관 점도계를 사용하여 측정하였으며 질화규소의 부피비가 60%일 때까지는 만족할 만한 성형성과 혼합질을 가짐을 알 수 있었다.

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Quantification Method of Macro Stickies for Recycled Pulps (재생펄프의 점착성 이물질 정량 분석 방법)

  • 윤병태;오세균
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.2
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    • pp.86-91
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    • 1999
  • A new test method has been developed for a quantitative evaluation of macro-stickies in recycled pulps. The method uses a fine slot screen to separate a sticky particles form fiber in the pulp samples. The obtained sticky particles were spread on filter paper and covered with silicon carbide powder in order to make the stickies area with sufficient contrast between stickies and background. The stickies are then counted by a scanner-based image analysis system. The validity of this evaluation method of stickies of KOCC, ONP and white ledger wastepaper recycling plants respectively. It is shown that this method can be applied for a quantitative determination of stickies content in various recycled pulp samples. With this testing method, reproducible and reliable data were obtained for the actual mill pulp samples.

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The Properties of the Metal Hydride electrodes prepared by Silicon Sealant (Si-sealant를 이용하여 제조한 금속수소화물 전극의 특성)

  • CHOI, Jeon;PARK, Choong-Nyeon
    • Journal of Hydrogen and New Energy
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    • v.4 no.2
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    • pp.23-28
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    • 1993
  • The $(LM)Ni_{4.5}Co_{0.1}Mn_{0.2}Al_{0.2}$ hydrogen storage alloy powders were conducted 25wt% electroless copper plating in an acidic bath. For the preparation of a hydride electrodes, the copper coated alloy powder was mixed with Si-sealant(organosilicon) and compacted with $6t/cm^2$ at room temperature. The electrode characteristics were examined through electrochemical measurements in a half cell. As a sealant contents increased, the initial discharge capacity of si-sealant bounded electrode was lower and the activation rate in high current density was slower. For extended cycles, however, the electrodes with the Si-sealant were superior in a high rate discharge and useful range of temperature over the sealant-free electrode. In addition, the cycle life increased with increasing the amount of Si-sealant added. It can be suggested from the results that the Si-sealant as a binder could be applied to the preparation of the metal hydride electrode.

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Rapid Tooling of Porous Ceramic Mold Using Slip Casting (슬립 캐스팅을 이용한 통기성 세라믹형의 쾌속 제작)

  • Chung, Sung-Il;Jeong, Du-Su;Im, Yong-Gwan;Jeong, Hae-Do;Cho, Kyu-Kap
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.5 s.98
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    • pp.98-103
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    • 1999
  • The application field of porous mold is more and more expended. A mixture of alumina and cast iron is used for making porous mold using slip and vacuum casting method in this study. Slip casting is a process that slurry is poured into silicon rubber mold, dried in vacuum oven, debinded and sintered in furnace, In this procedure, slurry is composed of powder, binder, dispersion agent, and water. Vacuum casting is a technique for removing air bubbles existed in the slurry under vacuum condition. Since ceramics has a tendency of over-shrinkage after sintering, cast iron is used to compensate dimensional change. The results shows that sintering temperature has a great effect on characteristics of alumina-cast iron composite sintered parts. Finally ceramic-metal composite sintered mold can be used for aluminum alloy casting of shoe mold using this process.

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Luminescence Characteristics of Red Light Emitting (YVO4:Eu Thin-Film Phosphors Deposited on Si Substrate Using Pulsed Laser Deposition

  • Kim, Dong-Kuk;Kang, Wee-Kyung
    • Bulletin of the Korean Chemical Society
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    • v.25 no.12
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    • pp.1859-1862
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    • 2004
  • Europium doped yttrium vanadate ($YVO_4$:Eu) phosphor thin films were grown using a pulsed laser deposition (PLD) technique on silicon substrate. The structural characterization carried out on a series of ($YVO_4$:Eu films at post annealing temperature in the range of 550 $^{\circ}C$-1150 $^{\circ}C$ indicating that films were preferentially (200) oriented at post annealing temperature above 950 $^{\circ}C.$ Photoluminescence of thin film increased with the increase of post annealing temperature and ambient oxygen pressure though the thin film has the powder-like surface morphology at oxygen pressure above 200 mTorr. Photoluminescence decay from $^5D_1$ level of $Eu^{3+}$ show the great concentration dependency, which can be used as a good parameter to control the composition of ($YVO_4$:Eu thin film.

Development of Ultraprecision Finishing Technique using Bonded Magnetic Abrasives (결합된 자성연마입자를 이용한 초정밀 피니싱 기술 개발)

  • 윤종학;박성준;안병운
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.5
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    • pp.59-66
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    • 2003
  • This study suggests the new ultraprecision finishing techniques for micro die and mold parts using magnetic field-assisted polishing. Conventional magnetic abrasives have several disadvantages, which are missing of abrasive particle and inequal mixture between magnetic particle and abrasive particle. Therefore, bonded magnetic abrasive particles are fabricated by several method. For example, plasma melting and direct bonding. Carbonyl iron powder is used as magnetic particle there silicon carbide and alumina are abrasive particles. Developed magnetic abrasives are analyzed using SEM. Feasibility of magnetic abrasive and polishing performance of this magnetic abrasive particles also have been investigated. After polishing, surface roughness of workpiece is reduced from 85.4 ㎚ Ra to 9 ㎚ RA.