• Title/Summary/Keyword: Powder forming

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A Study on the Si-SiC Composites Fabricated by Pressureless Powder Packing Forming Method (무가압 분말 충전 성형법에 의해 제조된 Si-SiC 복합체에 관한 연구)

  • 박정현;임은택;성재석;최헌진;이준석
    • Journal of the Korean Ceramic Society
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    • v.32 no.6
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    • pp.710-718
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    • 1995
  • The new forming method, Pressureless Powder Packing Forming Method was applied to the manufacturing of reaction sintered SiC. After the experiments of vibratory powder packing and binder infiltration, the abrasive SiC powder of which mean size is 45${\mu}{\textrm}{m}$ was selected to this forming method. Uniform green bodies with porosity of 45% and narrow pore size distribution could be formed by this new forming method. Also, complex or varied cross-sectional shapes could be easily manufactured through the silicone rubber mould used in this forming method. Maximum 15 wt% amorphous carbon was penetrated into green body by multi impregnation-carbonization cycles. And reaction-bonded SiC was manufactured by infiltration of SiC-carbon shaped bodies with liquid silicon.

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Preparation of Alumina Ceramics by Pressureless Powder Packing Forming Method (II) Characterization of Sintered Body Fabricated by Pressureless Powder Packing Forming Method (무가압 분말 충전 성형법을 이용한 알루미나 세라믹스의 제조 (II) 무가압 분말 충전 성형법에 의해 제조된 소결체 특성 관찰)

  • 박정형;성재석
    • Journal of the Korean Ceramic Society
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    • v.32 no.1
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    • pp.113-119
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    • 1995
  • The green body was fabricated by a new forming method, pressureless powder packaing forming method, and the characteristics of sintered specimen were investigated. It was found that alumina ceramics prepared by the present method showed porous structure with narrow pore size distribution, and in case of abrasive powder sintered body, compared with dry-pressed specimen, had the nearly same density. Especially, the specimen prepared with spray-dried granules showed the characteristic that granules were not either deformed or fractured during forming and sintering process. Therefore, it was found that this new forming method was effective method in fabrication of porous ceramics on account of easy control of porosity and pore size and its high thermal stability.

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Preparation of Alumina Ceramics by Pressureless Powder Packing Forming Method: (I) Development of Pressureless Powders Packing Forming Method and Characterization of Green Body (무가압 분말 충전 성형법을 이용한 알루미나 세라믹스의 제조: (I) 무가압 분말 충전 성형법 개발 및 성형체 특성 관찰)

  • 박정현;성재석;이상진
    • Journal of the Korean Ceramic Society
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    • v.31 no.1
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    • pp.31-38
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    • 1994
  • To overcome the demerit of conventional forming method, new forming method, pressureless powder packing forming method, was investigated. This technique is performed by powder packing followed by the infiltration of binder solution. Various alumina powders were used as starting materials and the powders showing good packing condition through powder packing experiment were chosen. The green densities prepared by this new forming method with these powders were lower than those of specimens by pressing method, but, nearly same density was obtained in case of green body prepared with the powders having high packing density. The distribution of binder in a green body was homogeneous and it was possible to a complex shape form by this forming method.

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Synthesis and Characterization of Zinc Phosphate Cement Powder and Cement-forming Liquid

  • Park, Choon-Keun
    • The Korean Journal of Ceramics
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    • v.3 no.4
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    • pp.269-273
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    • 1997
  • Chemical composition of cement powder influences the setting time and early compressive strength development. The setting time increases as the amounts of zinc oxide and magnesium oxide are increased. For one day compressive strength development, a cement powder with a composition 90% ZnO, 8% MgO and 2% silica resulted in the highest strength (greater than 1, 090 kg/$\textrm{cm}^2$). Cement-forming liquids also need to be buffered, with both aluminum and zinc ions, for a good consistency and a higher strength of the zinc phosphate cement. These liquids control the setting reactions.

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A Model on the Densification of Agglomerates of Powders (분말 응집체의 치밀화에 관한 모델)

  • 김형섭;이재성
    • Journal of Powder Materials
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    • v.11 no.4
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    • pp.301-307
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    • 2004
  • Successful implementation of the powder forming process requires a detailed understanding of several interacting phenomena. The aim is to better control the process variables and to optimize the design parameters. A number of studies were carried out using various constitutive models that take the density change during powder forming into account. Most of them were developed for powders and sintered porous metals, but few of them can describe powder agglomerates, whose behaviour is different from that of uniformly arranged powders. The modification is needed to account for the effect of agglomeration on densification behaviour. Incorporating powder agglomeration into a constitutive model is of considerable importance, as it provides a possibility of relating the powder densification response to microstructural characteristics of powder particles, especially in case of nano powders. In this paper, we proposed a new powder agglomerate model in order to describe the unique densification behaviour of nano powders. The proposed model was applied to the densification of powder agglomerates during cold isostatic pressing.

The Fabrication and Characteristics of Porous Alumina Ceramics by Pressureless Powder Packing Forming Method : I . Alumina (무가압분말충전성형법에 의한 다공성 세라믹스의 제조 및 특성 : I. 알루미나)

  • 박정현;황명익;김동희;최환욱;김용남
    • Journal of the Korean Ceramic Society
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    • v.36 no.6
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    • pp.662-670
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    • 1999
  • Porous alumina was fabricated from pressureless powder packing forming method using powders granulated by spray drying. It was investigated the pore size distribution of fabricated porous alumina. The results of microstructural observation showed that intraganular pore size and intragranular pore size. At 1700$^{\circ}C$ there were no intragranular pores but it showed homogeneous distribution of intergranular pore size. The bending strength and shrinkage increased as porosity decreased. In case of thermal shock resistance sudden decrease of bending strength to $\Delta$T was not shown because intergranular large pore prevented sudden crack propagation.

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The Fabrication and Characteristics of Porous Ceramics by Pressureless Powder Packing Forming Method ; II, Mullite & Cordierite (무가압분말 충전성형법에 의한 다공성 세라믹스의 제조 및 특성 : II. 뮬라이트 & 코디어라이트)

  • 박정현;황명익;김동희;최환욱;김용남
    • Journal of the Korean Ceramic Society
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    • v.36 no.6
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    • pp.671-678
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    • 1999
  • Porous ceramics were fabricated from pressureless powder packing forming method using mullite and cordierite powders granulate by spray drying. The bending strength and shrinkage of porous ceramics were increased and their porosity were decreased with increasing temperature. It showed homogeneous distribution of 2$\mu\textrm{m}$ intergranular pores of mullite at 1400$^{\circ}C$, 2.5$\mu\textrm{m}$ intergranular pores of cordierite at 1300$^{\circ}C$ respedtively. Above that temperature intragranular particles were sintered and sintering by intergranular necking was extremely proceeded. In the test of thermal shock resistance sudden decrease of bending strength to $\Delta$T was not shown because intergranular large pore prevented sudden crack propagation.

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A Finite Element Analysis for Near-net-shape Forming of Al6061 Powder under Warm Pressing (온간 성형 하에서 Al 합금 분말의 정밀정형에 대한 유한요소해석)

  • Kim, Ki-Tae;Yang, Hoon-Chul;Kim, Jong-Kwang
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.507-512
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    • 2003
  • A finite element analysis for near-net-shape forming of Al6061 powder was performed under warm pressing. The advantages of warm compaction by rubber isostatic pressing were discussed to obtain parts with better density distributions. To simulate densification and deformed shape of a powder compact during warm pressing, the elastoplastic constitutive equation based on yield function of Shima-Oyane was implemented into a finite element program(ABAQUS). The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze nonlinear elastic response of rubber. Finite element results were compared with experimental data for Al6061 powder compacts under warm pressing.

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Spray Forming of $Mg_2Si$ Rich Aluminum Alloys

  • Ellendt, N.;Uhlenwinkel, V.;Stelling, O.;Irretier, A.;Kessler, O.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.231-232
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    • 2006
  • Aluminum Alloys with a content of 22 wt.-% $Mg_2Si$ were spray formed. This alloy features by a low density and is therefore a superior material for leightweight applications. The main problem in spray forming of this type of alloy was the occurance of high porosities. First process optimizations have been performed to decrease porosity under a certain level, so that it can be closed by an extrusion process

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