• Title/Summary/Keyword: Pressure Sintering Method

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Effects of the Whisker Orientation and Sintering Temperature on Mechanical Properties of the Si$_3$N$_4$ based Composites (Si$_3$N$_4$ Whisker의 배열방향과 소결온도가 Si$_3$N$_4$ 복합체의 기계적 성질에 미치는 영향)

  • 김창원;박동수
    • Journal of the Korean Ceramic Society
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    • v.36 no.5
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    • pp.483-489
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    • 1999
  • Gas pressure sintered silicon nitride based composites with 3 wt% $\beta$-Si3N4 whiskers were prepared and change of properties according to the whisker orientation and sintering temperature was studied. The tapes with whiskers were fabricated by two different method ; conventional tape casting and a modified tape casting by using guide pins,. Orientations of the whiskers were controlled by different stacking sequences of the sheets cut from the tape. Samples were fully densified by gas pressure sintering at 2148-2273K. As the sintering temperature increased size of the large elongated grains increased. In case of unidirectional samples sintering shrinkage normal to the whisker alignment direction was larger than that of parallel to the direction and the shrinkage anisotropy increased slightly as sintering temperature increased. As sintering temperature increased the crack length parallel to whisker alignment direction became shorter but that normal to the direction did not depend on sintering temperature. In case of cross-plied samples the anisotropy of mechanical properties disappeared.

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Computer aided simulation of spark plasma sintering process (Part 1 : formulation) (스파크 플라즈마 소결공정의 전산모사(1부 : 수식화))

  • Keum Y.T.;Jean J.H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.1
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    • pp.38-42
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    • 2006
  • Spark plasma sintering processes have been rapidly introduced recently to improve the quality and productivity of ceramic products and to solve the problem of environmental pollutions. Sintering temperatures and pressing pressures in the spark plasma sintering process are known to be the important factors highly affecting the quality of the ceramics. In this research, in order to see the effects of sintering temperatures and pressing pressures on the grain growth during the spark plasma sintering process of $Al_2O_3$ the grain growth processes associated with sintering temperatures and pressing pressures are simulated by the Monte Carlo method (MCM) and the finite element method (FEM). In this Part 1, the formulations for the simulation, which is the theoretical background of Part 2, are introduced.

Optical properties of ZnS ceramics by hot press stack sintering process (고온 가압 적층 소결에 의한 황화아연 세라믹스의 광학성 특성)

  • Park, Buem-Keun;Paik, Jong-Hoo
    • Journal of Sensor Science and Technology
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    • v.30 no.3
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    • pp.148-153
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    • 2021
  • During the manufacture of a ZnS lens with excellent transmittance in the mid-infrared region (3-5 ㎛) by the hot-press process, a single-layer sintering method is used in which one lens is manufactured in one process. Additional research is required to improve this single-layer sintering method because of its low manufacturing efficiency. To solve this problem, the variation in optical properties of ZnS lenses with change in sintering temperature was investigated by introducing a Stack sintering method that can sinter multiple lenses simultaneously. A carbon paper was placed between the molded lenses and sintered into five layers. The average permeability of 67% at medium infrared wavelengths of 3-5 ㎛ was excellent under the following sintering conditions: pressure of 50 MPa and temperature of 850℃. This value is 1% less than the average permeability in the case of single-layer sintering of the ZnS lens. It was confirmed that the stack sintering method developed in this study can be used to manufacture a large number of lenses with excellent characteristics in a single process.

A study on porous metal mold using organic binder (유기바인더를 이용한 통기성 금형제작에 관한 연구)

  • 김경래;정성일;임용관;정해도;이석우;최헌종
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.1026-1029
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    • 2002
  • Outlet of gas has been a big problem in deforming rubber or plastic in pressing mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a produce. In this study, the sintering method is used for making porous metal mold. Porous metal mold has many open pores, which are very small. When Porous metal mold is used for pressing mold, all process would be made short, produce cost would be down, and it would not leave vent marks on the surface of a produce. Porosity varies from sintering and pressing conditions, which are the pressure of compacting powder, the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering temperature condition for the Porous metal mold.

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Effects of Sintering Temperature on Fabrication Properties of LPS-SiC Ceramics (LPS-SiC 세라믹스 제조특성에 미치는 소결온도의 영향)

  • Park, Yi-Hyun;Jung, Hun-Chae;Kim, Dong-Hyun;Yoon, Han-Ki;Kohyam, Akira
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.204-209
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    • 2004
  • SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, $SiC_f/SiC$ composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of $SiC_f/SiC$ composites by hot pressing method. In the present work, Monolithic LPS-SiC was fabricated by hot pressing method in Ar atmosphere at 1760 $^{\circ}C$, 1780 $^{\circ}C$, 1800 $^{\circ}C$ and 1820 $^{\circ}C$ under 20 MPa using $Al_2O_3-Y_2O_3$ system as sintering additives in order to low sintering temperature. The starting powder was high purity ${\beta}-SiC$ nano-powder with an average particle size of 30 nm. Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the sintering temperature. In the micro-structure of this specimen, it was found that grain of sintered body was grown from 30 nm to 200 nm.

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Evaluation of Mechanical Properties and Microstructural Behavior of Sintered WC-7.5wt%Co and WC-12wt%Co Cemented Carbides

  • Raihanuzzaman, Rumman Md.;Song, Jun-U;Tak, Byeong-Jin;Hong, Hyeon-Seon;Hong, Sun-Jik
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.58.1-58.1
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    • 2011
  • WC-Co and other similar cemented carbides have been widely used as hard materials in industrial cutting tools and as mould metals; and a number of techniques have been applied to improve its microstructural characteristics, hardness and ear resistance. Cobalt is used primarily to facilitate liquid phase sintering and acts as a matrix, i.e. a cementing phase between WC grains. A uniform distribution of metal phase in a ceramic is beneficial for improved mechanical properties of the composite. WC-Co, starting from initial powders, is vastly used for a variety of machining, cutting, drilling, and other applications because of its unique combination of high strength, high hardness, high toughness, and moderate modulus of elasticity, especially with fine grained WC and finely distributed cobalt. In this study, that started with two different compositions of initial powders, WC-7.5wt%Co and WC-12wt%Co with initial powder size being 1~3 ${\mu}m$, magnetic pulsed compaction followed by subsequent vacuum sintering were carried out to produce consolidated preforms. Magnetic Pulsed Compaction (MPC), a very short duration (~600 ${\mu}s$), high pressure (~4 Gpa), high-density preform molding method was used with varied pressure between 0.5 and 3.0 Gpa, in order to reach an initial high density that would help improve the sintering behavior. For both compositions and varied MPC pressure, before and after sintering, changes in microstructural behavior and mechanical properties were analyzed. With proper combination of MPC pressure and sintering, samples were obtained with better mechanical properties, densification and microstructural behavior, and considerably improved than other conventional processes.

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Effect of Packing Characteristics on the sintering Propertiesof Pyrophyllite (랍석분쇄물의 충전성이 그 소결성에 미치는 영향)

  • 지응업;최상욱;류태원
    • Journal of the Korean Ceramic Society
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    • v.14 no.4
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    • pp.236-241
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    • 1977
  • Three kinds of specimen, consisting of the graded pyrophyllite particles alone, a substituent of 8 percent fire clay for the finer portion ($F_2$) of it, and 0.8 percent inorganic binder-added composite were prepared under the following conditions respectively; moisture content=4.5~5.0%, forming pressure=250kg/$\textrm{cm}^2$ and sintering temperature=1, 000~1, 30$0^{\circ}C$. The various properties such as modulus of rupture, apparent porosity, bulk specific gravity, pore size and pore distributiion were measured in order to collaborate with sintering phenomena. The results obtained are as follows: (1) Apparent porosity isgradually decreased with rising the sintering temperature to 1, 25$0^{\circ}C$. (2) The binder-added specimen showed the lowest value in porosity. (3) The optimum sintering temperature of specimens was considered to be 1, 25$0^{\circ}C$. (4) The wider differences between pore volumes of specimens could be obtained by method of mercurypenetration porosimeter than by the conventional method for porosity.

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Materials Characterization and the Microstructure of Pure Cu and Cu-3vol%CNT Composite Fabricated From Optimization of SPS Processing Variables (SPS 공정 변수의 최적화에 의한 Pure Cu와 Cu-3vol%CNT composite의 미세구조와 소재특성)

  • Lee, Hee Chang;Kim, Hye Sung
    • Journal of the Korean Society for Heat Treatment
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    • v.33 no.4
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    • pp.185-192
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    • 2020
  • In this study, materials characterization of pure copper and copper based carbon nano-tube composite prepared by powder metallurgy method were investigated. Prior to evaluate materials characterization, spark plasma sintering processing variables such as sintering temperature, pressure, thickness and diameter of compacts was optimized to ensure the microstructure and materials property of pure Cu and Cu-CNT composite. In addition, corrosion behavior of Cu-based CNT composite produced by powder sintering method was investigated. It was confirmed from this study that the corroded surfaces of the composite shows less dissolution compared with pure copper in 3.5 wt% NaCl solution. The measured corrosion current density (Icorr) indicates improved corrosion property of Cu based composite containing small additions of CNTs in chloride containing media. Micro-galvanic activity between Cu and CNT was not observed in given sintering condition.

Fabrication and Mechanical Properties of WC-Mo2C-Co Hard Materials by the Pulsed Current Activated Sintering Method (펄스 전류 활성 소결법을 이용한 WC-Mo2C-Co 소결체 제조 및 기계적 특성 평가)

  • Youn, Hee-Jun;Bang, Han-Sur;Bang, Hee-Seon;Oh, Ik-Hyun;Park, Hyun-Kuk
    • Korean Journal of Metals and Materials
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    • v.50 no.12
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    • pp.921-929
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    • 2012
  • The pulsed current activated sintering method (PCAS) is a new rapid sintering method that was developed recently for fabricating ceramics and composites. This method combines a high temperature for a short time with pressure application. In this work, PCAS was used to fabricate $WC-5wt%Mo_2C-5wt%$ Co hard material using WC, $Mo_2C$, and Co. The $WC-Mo_2C-Co$ was almost completely dense with a relative density of up to 100% after the simultaneous application of a pressure of 60 MPa and electric current for 11 min without grain growth. The average grain size of WC that was produced through PCAS was about $0.5-0.6{\mu}m$. The vickers hardness and fracture toughness of the $WC-5wt%Mo_2C-5wt%$Co hard materials were about $2453.5kg/mm^2$ and $7.9MPa{\cdot}m^{1/2}$, respectively, for 60 MPa at $11200^{\circ}C$.

Evaluation on Mechanical Properties of Tungsten by Sintering Additive Content (소결첨가재에 의한 텅스텐의 기계적 특성평가)

  • Lee, Sang-Pill;Lee, Jin-Kyung
    • Journal of the Korean Society of Industry Convergence
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    • v.25 no.4_2
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    • pp.621-626
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    • 2022
  • Tungsten is a high melting point metal unlike other steel materials, and it is difficult to manufacture because of its high melting temperature. In this study, pressure sintering process method was applied to manufacture the tungsten materials at low temperature. Therefore, it is necessary to densify the sintered material by using a sintering additive. Studies have been conducted on how the amount of titanium for sintering tungsten affects the mechanical properties of tungsten in this study. In order to secure the densification mechanism of tungsten powder during the sintering process, the characteristics of the sintered tungsten material according to the change of titanium content were evaluated. It was investigated the relationship between sintering parameters and mechanical properties for densification of microstructures. The sintered tungsten materials according to sintering additive content showed high sintered density (about 16.31g/cm3) and flexural strength (about 584 MPa) when the content of sintering additive was 3 wt%. However, as the content of the sintering additive increases, mechanical property of flexural strength is decreased, and the porosity is increased due to the heterogeneous sintering around titanium.