• Title/Summary/Keyword: compacted materials

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Compressive Behavior of 7xxx Series Al Composites Reinforced with $Al_2O_3$

  • Seo, Young-Ik;Min, Kyung-Ho;Lee, Kyu-Hwan;Kim, Young-Do
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1063-1064
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    • 2006
  • Mechanical properties of 7xxx series Al metal matrix composite (MMC) powders containing different amounts of ceramic were investigated. The ceramic contents of the starting powders were 5 wt.% or 10 wt.%. The powders were uniaxially cold compacted using a cylindrical die with a compacting pressure of 250 MPa and were sintered at $620^{\circ}C$ in a dry $N_2$ atmosphere for 60 min. For the heat treatment, sintered parts were solution treated at $475^{\circ}C$ and aged at $175^{\circ}C$. Compression tests were conducted to reveal the effect of $Al_2O_3$ particle content on the mechanical properties of the composites. Fractography was examined using a scanning electron microscope.

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Synthesization of WC/Co Composite Powders Doped V and Cr by Mechanochemical Method

  • Im, Hoo-Soon;Hur, Jah-Mahn;Lee, Wan-Jae
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.646-647
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    • 2006
  • Nano-sized WC particles in WC/Co composite powders were synthesized by mechanochemical method. The raw powders$(WO_3,\;Co_3O_4,\;VC,\;Cr_3C_2$ and graphite) were mixed by planetary milling for 30 hours. The compositions were WC-10 and -20 wt% Co added VC and $Cr_3C_2$. The direct reduction and carburization of the mixed powders were carried at $900\;^{\circ}C$ for 1 to 3 hours under flowing Ar gas. The mean size of WC particles in WC/Co composite powders was about 16 nm. The resultant powders were compacted and sintered at $1300{\sim}1360\;^{\circ}C$ for 0.5 hour. After sintering the mean size of WC particles was about 50 nm.

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Properties of compacted iron powder core coated with organic materials (코팅제 및 코팅 함량에 따른 철 분말 성형체의 특성)

  • Min, Bok-Ki;Kim, In-Sung;Kim, Jong-Ryung;Choi, Sung-Jo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.264-267
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    • 2005
  • Soft magnetic iron powders have been coated with polyester or phenol resin. And the coated powder (soft magnetic composite) have been pressed into ring type core over the pressure of 870 MPa. Green density, magnetic flux density, permeability, core loss of the samples were measured to look at the effect of the coating materials and the amount of them. Green density is increased with the amount of coating materials and shows the maximum value, 6.5 $g/cm^3$ at 5 w/o, but decreased over it. And lowest value of the core loss is showed for the 5 w/o coated samples.

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Luminescence property of Eu2+ in SiO2-Al2O3 glass phosphor

  • Chae, Ki Woong;Lee, Kyoung-Ho;Cheon, Chae Il;Cho, Nam In;Kim, Jeong Seog
    • Journal of Ceramic Processing Research
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    • v.13 no.spc2
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    • pp.189-192
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    • 2012
  • Manufacturing process for silicate glass phosphors containing Eu2+ activator and their photoluminescence property have been studied. We adopted powder sintering process instead of traditional glass melting process for making glass phosphor. At first, phosphor powders were synthesized at 1200 ℃ for 2-3 hours under a reducing atmosphere with 10% H2-90% N2 gas mixture. The reduced powders were compacted into discs and then the discs weresintered at 1400 ~ 1500 ℃ for 1 hr under a reducing atmosphere of 5H2-95% N2. The enhancement of PL intensity by Al2O3 addition, XPS binding energy shift of Si 2p and O 1s, sintering shrinkage, and crystallization were characterized.

The Study of Mechanical Properties of Degraded Compacted Graphite Iron(CGI) Under 873~1273 K (873~1273 K에서 열화된 강화흑연강의 기계적 특성 연구)

  • Nam, Ki Woo;Lee, Soo Cheol
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.2
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    • pp.173-180
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    • 2013
  • Compacted graphite iron(CGI), also known as vermicular graphite iron, is a metal which is gaining popularity in applications that require either greater strength, or lower weight than cast iron. Recently compacted graphite iron has been used for diesel engine blocks. Considering that using in exhaust manifold of the diesel engine, CGI340 was conducted the heat treatment during 1 hour to 96 hours from 873 to 1273 K. Mechanical characteristics were evaluated. The obtained results are as follows; The tensile strength of the heat treated specimens showed overall lower tensile strength than that of the base metal. Tensile strength decreases with increasing of heat treatment time, and the higher heat treatment temperature and the longer time, were more reduced. The fatigue limit by the ultrasonic fatigue test was approximately 130 MPa of base metal, 100 MPa of 1173 K (96 hrs) specimen, respectively. The hardness decreases with increasing heat treatment time, and the higher the heat treatment temperature was lowered hardness distribution. In CGI340, average hardness of nodular graphite was 120 Hv, average hardness of vermicular graphite was 114 Hv. This showed lower hardness than the base structure ferrite. The nodular graphite and vermicular graphite according to the heat treatment temperature and time didn't have a consistent change. However, the grain size of base structure grew with increasing of heat treatment time.

An Experimental Study on Determination of Dry Density of Sand Mixed with Gravels (자갈 섞인 모래의 건조밀도 계산에 관한 실험 연구)

  • Park, Sung-Sik;Choi, Sun-Gyu
    • Journal of the Korean Geotechnical Society
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    • v.29 no.7
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    • pp.37-46
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    • 2013
  • Various sizes of gravels are included in the most field soils that are utilized for civil constructions. Especially, the small amounts of gravel are often included in selected soils for backfill materials, earth dams, and subbase ground. In such cases, the small amounts of mixed gravel and its shape may influence the determination of dry density of soils, which results in an inaccurate degree of compaction for soils in the field. In this study, a dry density of sand with various gravel contents (0, 10, 17, 23, 29 and 33%) and three different sizes (2.0-2.36, 3.35-4.75, 5.6-10.0 mm) was experimentally investigated for compacted or loosely packed conditions. The loosely packed sand with gravels was simulated by pouring sand into compaction mould and its density was determined. When a 33% of gravel content was mixed with sand, its dry density increased up to 15-20% for compacted specimen and 20-23% for loosely packed specimen. When a gravel content and size were the same, a dry density of compacted specimen was $0.1-0.16g/cm^3$ higher than that of loosely packed specimen. Even though the same gravel content was used, a dry density of sand with big gravels was $0.04-0.08g/cm^3$ higher than that of sand with small gravels for compacted specimen and $0.03-0.05g/cm^3$ for loosely packed specimen.

The Frost-Susceptibility of Compacted Coal Ash with Proper Mixing Ratio of Fly Ash to Bottom Ash (비회와 저회의 적정 혼합비로 다짐한 석탄회의 동상성)

  • Chun, Byung Sik;Gang, In Sung;Koh, Yong Il
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.1
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    • pp.173-178
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    • 1993
  • The most appropriate mixing ratio of fly ash to bottom ash obtained from compaction characteristics and CBR values is varying from 5:5 to 6:4. But these mixed ashes are frost-susceptible materials according to judging by the paticle-size distribution because of a lot of silty-size paticles. In this study, the frost-susceptibility of compacted coal ash with proper mixing ratio is examined experimentally for use of subgrade materials. And, the efforts have been made to find proper cement addition in making these mixed ashes frost-insusceptible. It was revealed that these mixed ashes are frost-susceptible, and 4% of cement content is required to be made frost-insusceptable. It was found that amount of frost heave of these mixed ashes decreases with the unconfined compressive strength, and increases with log k if the permeability coefficient k is as low as the water into the freezing front of these mixed ashes is restricted.

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Spark Plasma Sintering of the Ductile Cu-Gas-atomized Ni Bulk Metallic Glass Composite Powders (연질 Cu 분말-가스분무 Ni계 벌크 비정질 복합분말의 방전플라즈마 소결에 관한 연구)

  • Kim, Jin-Chun;Kim, Yong-Jin;Kim, Byoung-Kee;Kim, Ji-Soon
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.351-359
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    • 2006
  • Ni based($Ni_{57}Zr_{20}Ti_{18}Si_2Sn_3$) bulk metallic glass(BMG) powders were produced by a gas atomization process, and ductile Cu powders were mixed using a spray drying process. The Ni-based amorphous powder and Cu mixed Ni composite powders were compacted by a spark plasma sintering (SPS) processes into cylindrical shape. The relative density varied with the used SPS mold materials such as graphite, hardened steel and WC-Co hard metal. The relative density increased from 87% to 98% when the sintering temperature increased up to $460^{\circ}C$ in the WC-Co hard metal mold.

Densification of TiO2 Nano Powder by Magnetic Pulsed Compaction (자기펄스 성형법에 의한 TiO2 나노 분말의 치밀화)

  • Kim, Hyo-Seob;Lee, Jeong-Goo;Rhee, Chang-Kyu;Koo, Jar-Myung;Hong, Soon-Jik
    • Korean Journal of Materials Research
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    • v.18 no.8
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    • pp.411-416
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    • 2008
  • In this research, fine-structure TiO2 bulks were fabricated in a combined application of magnetic pulsed compaction (MPC) and subsequent sintering and their densification behavior was investigated. The obtained density of $TiO_2$ bulk prepared via the combined processes increased as the MPC pressure increased from 0.3 to 0.7 GPa. Relatively higher density (88%) in the MPCed specimen at 0.7 GPa was attributed to the decrease of the inter-particle distance of the pre-compacted component. High pressure and rapid compaction using magnetic pulsed compaction reduced the shrinkage rate (about 10% in this case) of the sintered bulks compared to general processing (about 20%). The mixing conditions of PVA, water, and $TiO_2$ nano powder for the compaction of $TiO_2$ nano powder did not affect the density and shrinkage of the sintered bulks due to the high pressure of the MPC.

Effect of Core-Shell Structure on Compaction Behavior of Harmonic Powder (Core-shell 구조를 지니는 하모닉 분말의 성형거동 분석)

  • Joo, Soo-Hyun;Park, Hyo Wook;Kang, Soo Young;Lee, Eon Sik;Kang, Hee-Soo;Kim, Hyong Seop
    • Journal of Powder Materials
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    • v.22 no.2
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    • pp.105-110
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    • 2015
  • In this study, effect of core-shell structure on compaction behavior of harmonic powder is investigated. Harmonic powders are made by electroless plating method on Fe powders. Softer Cu shell encloses harder Fe core, and the average size of Fe core and thickness of Cu shell are $34.3{\mu}m$ and $3.2{\mu}m$, respectively. The powder compaction procedure is processed with pressure of 600 MPa in a cylindrical die. Due to the low strength of Cu shell regions, the harmonic powders show better densification behavior compared with pure Fe powders. Finite element method (FEM) is performed to understand the roll of core-shell structure. Based on stress and strain distributions of FEM results, it is concluded that the early stage of powder compaction of harmonic powders mainly occurs at the shell region. FEM results also well predict porosity of compacted materials.