• Title/Summary/Keyword: Extrusion-sintering Process

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Microstructure Control of HAp Based Artificial Bone Using Multi-extrusion Process

  • Jang, Dong-Woo;Lee, Byong-Taek
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.54.1-54.1
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    • 2011
  • Porous hydroxyapatite has been widely used as clinical implanted material. However, it has poor mechanical properties. To increase the strength as well as the biocompatibility of the porous HAp based artificial bone, it was fabricated by multi-extrusion process. Hydroxyapatite and graphite powders were mixed separately with ethylene vinely acetate and steric acid by shear mixing process. Hydroxyapatite composites containing porous microstructure were fabricated by arranging it in the die and subject it to extrusion process. Burn-out and sintering processes were performed to remove the binder and graphite as well as increase the density. The external and internal diameter of cylindrical hollow core were approximately 10.4 mm and 4.2 mm, respectively. The size of pore channel designed to increase bone growth (osteconduction) was around 150 ${\mu}m$ in diameter. X-ray diffraction analysis and SEM observation were performed to identity the crystal structure and the detailed microstructure, respectively.

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In-Situ Fabrication of Micro-channeled Multi Tubular Solid Oxide Fuel Cell using Multi-pass Extrusion Process (다중압출 공정을 이용한 마이크로 채널 다중 원통형 고체산화물 연료전지의 in-situ 제조)

  • Byun, Ki-Cheon;Rahman, AHM Esfakur;Kim, Jong-Hee;Lee, Byong-Taek
    • Korean Journal of Materials Research
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    • v.17 no.6
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    • pp.313-317
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    • 2007
  • In-situ micro-channeled multi tubular solid oxide fuel cell(SOFC) was fabricated using multi-pass extrusion process with out side diameter of 2.7 mm and active length of 5 mm that contained 61 individual cells. Cell materials used in this work were NiO-YSZ (50 : 50 vol.%), 8 mol% yttria-stabilized zirconia(8YSZ), $La_{0.8}Sr_{0.2}MnO_3(LSM)$ as anode, electrolyte, and cathode, respectively. The arrangement of each electrode and electrolyte layer in green bodies showed uniformity and integrity after extrusion and sintering. The XRD analysis confirmed that no reaction phases appeared and the microstructure of the electrolyte was fairly dense (relative density > 96%) after sintering.

Advancement in Powder Metallurgy of Aluminum Alloys

  • Takeda, Yoshinobu
    • Journal of Powder Materials
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    • v.5 no.4
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    • pp.340-344
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    • 1998
  • Along with the growth of conventional ferrous powder metallurgy (PM), PM of aluminum alloys has been intensively investigated in Japan. Although rapidly solidified aluminum alloy powder was first used in the USA,/sup 1)/ commercialization for consumer market was first realized in Japan./sup 2)/ In order to achieve the viable cost-performance including Near Net Shape (NNS) formability, we developed three processes, powder extrusion, powder forging and sintering. The new powder extrusion process does not use either capsulation or vacuum degassing. The new powder forging does not need lateral flow. The new sintering process does not use liquid phase. The performance achieved by the processes is outstanding mechanical or physical properties that has potential to substitute cast iron, steel, titanium Metal Matrix Composite (MMC) or Ingot Metallurgy (IM) aluminum alloys. Cooperation with customers, powder suppliers and research associations contributed to the advancement of PM aluminum alloys in Japan.

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Characterization of Artificial Aggregates Fabricated by Using Various Forming Methods (다양한 성형법으로 제조된 인공 골재의 특성)

  • Kang, Seung-Gu
    • Journal of the Korean Ceramic Society
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    • v.46 no.1
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    • pp.94-101
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    • 2009
  • The physical properties of artificial aggregates made from clay and inorganic wastes with poor plasticity depends largely on forming method. The artificial aggregates composing of coal fly ash, stone sludge and clay were fabricated using 4 different forming methods and those physical properties were comparatively analyzed. The surface of aggregates made through the extrusion forming process was dense and smooth but was rough for the aggregates obtained by crushing a tile-shaped green body. The aggregates made by pelletizing process had a weak green strength and bumpy surface. The shell generated at surface during a high temperature sintering process induced the most aggregates to be bloated due to a dense shell. But the aggregates made through pelletizing process with dense surface layer showed no significant change in bulk density with sintering temperatures. The water absorption of aggregates decreased with sintering temperature, and that of pelletized specimen was standing $1.8{\sim}2.2$ times higher than that of made by other forming methods. It is concluded that the aggregates having various properties could be fabricated from one batch by using different forming methods.

Properties $(Bi,Sb)_2(Te,Se)_3$-based Thermoelectrics Prepared by the Extrusion-Sintering Process (압출-소결법으로 제조된 $(Bi,Sb)_2(Te,Se)_3$계 열전재료의 특성)

  • Ji, Cheol-Won;Kim, Il-Ho;Lee, Dong-Hui
    • Korean Journal of Materials Research
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    • v.9 no.5
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    • pp.520-527
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    • 1999
  • As a new approache(extrusion-sintering process) to fabricate the thermoelectric materials, it has been at tempted to extrude and sinter the powders simultaneously. It was possible to produce the highly dense <$(Bi,Sb)_2(Te,Se)_3$-based thermoelectrics with sound surface appearances and microstructures by adjusting the process variables. For the p-type materials, the Seeback coefficient was increased with the amount of Te dopants, and the thermoelectric figure of merit appeared to be $2.5\times10^{-3}/K$ at room temperature when doped with 3 at % Te. The n-type specimen doped with 0.16 mol% $SbI_3$ showed the thermoelectric figure of merit of $1.8\times10^{-3}/K$. In both p-type an 우-type materials, the carrier mobility an the thermoelectric figure of merit parallel to the extrusion direction were higher than those perpendicular to it.

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Sintering of Ni-Based Amorphous Alloy Powders by Plasma Activated Sintering Process (PAS법을 이용한 Ni기 비정질 분말의 소결)

  • Koo, Ja-Min;Shin, Kee-Sam;Kim, Yoon-Bae;Bae, Jong-Soo;Hur, Sung-Kang
    • Korean Journal of Materials Research
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    • v.15 no.12
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    • pp.765-772
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    • 2005
  • PAS(Plasma Activated Sintering) process was tried to apply for the fabrication of BMG(Bulk Metallic Glasses) of $Ni_{57}Zr_{20}Ti_{18}Si_5}\;and\;Ni_{57}Zr_{20}Ti_{18}Si_3Sn_2$ from the as-atomized amorphous powder. Compressive strength for the BMG(bulk Metallic Glasses) of $Ni_{57}Zr_{20}Ti_{18}Si_5$ were lower than those of BMG rods produced by warm extrusion ,or copper mold casting method. Microstructural examination by optical microcope, SEM ana EDS showed that oxidation had occurred during PASintering. In order to prevent the powder from the oxidation during PASintering, Ni coating for $Ni_{57}Zr_{20}Ti_{18}Si_5$ amorphous powder by electroless-plating method was performed. Microstructural examination for Ni coated layers after PASintering indicated that the Ni coating had been so effective to prevent powder from oxidation during PASintering. Sintering behaviors of $Ni_{57}Zr_{20}Ti_{18}Si_3Sn_2$ represent the same as those of $Ni_{57}Zr_{20}Ti_{18}Si_5$.

Study on the Relationship between Aggregation Structure and Flow Rate Depending on Extrusion Temperature at Complex Mold of (Activated Carbon/Polymer Binder) ((활성탄/고분자바인더)복합성형체의 압출온도에 따르는 응집구조 및 유량 상관성에 관한 연구)

  • Lim, Yong Gyun;Kim, Young Jun;Park, Sang Jin;Hong, Sung-Kyu
    • Korean Chemical Engineering Research
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    • v.52 no.2
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    • pp.261-265
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    • 2014
  • As the need for miniaturization in water purification filter increases, the development of filter media for single filtration with multiple function was strongly required. In this study, the molded activated carbon composed of single unit was manufactured by extrusion-sintering process, and then the flow rate, density and porosity were investigated using the molded activated carbon manufactured at various extrusion temperature. We confirmed that it was possible to manufacture the single unit-molded activated carbon when the extrusion temperature was $140{\sim}230^{\circ}C$ more than $133^{\circ}C$ being of polymer binder melting point, and the optimal extrusion temperature for the molded activated carbon with maximum flow rate was $170^{\circ}C$ since the molded activated carbon had low density and high through porosity. Also we confirmed that the flow rate through the molded activated carbon was strongly dependent upon through pore porosity compared to total porosity for the molded activated carbon.

Multi-step Metals Additive Manufacturing Technologies

  • Oh, Ji-Won;Park, Jinsu;Choi, Hanshin
    • Journal of Powder Materials
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    • v.27 no.3
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    • pp.256-267
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    • 2020
  • Metal additive manufacturing (AM) technologies are classified into two groups according to the consolidation mechanisms and densification degrees of the as-built parts. Densified parts are obtained via a single-step process such as powder bed fusion, directed energy deposition, and sheet lamination AM technologies. Conversely, green bodies are consolidated with the aid of binder phases in multi-step processes such as binder jetting and material extrusion AM. Green-body part shapes are sustained by binder phases, which are removed for the debinding process. Chemical and/or thermal debinding processes are usually devised to enhance debinding kinetics. The pathways to final densification of the green parts are sintering and/or molten metal infiltration. With respect to innovation types, the multi-step metal AM process allows conventional powder metallurgy manufacturing to be innovated continuously. Eliminating cost/time-consuming molds, enlarged 3D design freedom, and wide material selectivity create opportunities for the industrial adoption of multi-step AM technologies. In addition, knowledge of powders and powder metallurgy fuel advances of multi-step AM technologies. In the present study, multi-step AM technologies are briefly introduced from the viewpoint of the entire manufacturing lifecycle.

Enhancing Electrical Properties of N-type Bismuth Telluride Alloys through Graphene Oxide Incorporation in Extrusion 3D Printing

  • Jinhee Bae;Seungki Jo ;Kyung Tae Kim
    • Journal of Powder Materials
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    • v.30 no.4
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    • pp.318-323
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    • 2023
  • The thermoelectric effect, which converts waste heat into electricity, holds promise as a renewable energy technology. Recently, bismuth telluride (Bi2Te3)-based alloys are being recognized as important materials for practical applications in the temperature range from room temperature to 500 K. However, conventional sintering processes impose limitations on shape-changeable and tailorable Bi2Te3 materials. To overcome these issues, three-dimensional (3D) printing (additive manufacturing) is being adopted. Although some research results have been reported, relatively few studies on 3D printed thermoelectric materials are being carried out. In this study, we utilize extrusion 3D printing to manufacture n-type Bi1.7Sb0.3Te3 (N-BST). The ink is produced without using organic binders, which could negatively influence its thermoelectric properties. Furthermore, we introduce graphene oxide (GO) at the crystal interface to enhance the electrical properties. The formed N-BST composites exhibit significantly improved electrical conductivity and a higher Seebeck coefficient as the GO content increases. Therefore, we propose that the combination of the extrusion 3D printing process (Direct Ink Writing, DIW) and the incorporation of GO into N-BST offers a convenient and effective approach for achieving higher thermoelectric efficiency.