• Title, Summary, Keyword: Sintering

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Application of rate-controlled sintering into the study of sintering behavior of boron carbide (탄화붕소 소결 거동 연구를 위한 율속제어소결의 적용)

  • Lee, Hyukjae
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.25 no.1
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    • pp.6-12
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    • 2015
  • Under rate-controlled sintering, furnace power is controlled to maintain a specific specimen contraction rate. This thermal processing method guarantees continuous process with a minimum thermal energy applied over time and makes it possible to control the density of the sintered body precisely. In this study, the rate-controlled sintering is applied to the sintering of $B_4C$ in order to investigate how rate-controlled sintering variables can affect the sintering behavior and/or grain growth behavior of $B_4C$ and how the results can be interpreted using sintering theories to draw an optimal sintering condition of the rate-controlled sintering. Further, the applicability of the rate-controlled sintering into the study for sintering of unknown materials is also considered.

Pressureless Sintering and Spark-Plasma Sintering of Fe-TiC Composite Powders (Fe-TiC 복합재료 분말의 상압소결과 방전플라즈마소결)

  • Lee, B.H.;Bae, S.W.;Bae, S.W.;Khoa, H.X.;Kim, Ji Soon
    • Journal of Korean Powder Metallurgy Institute
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    • v.22 no.4
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    • pp.283-288
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    • 2015
  • Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at $1300^{\circ}C$ for 3h. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.

Low-Temperature Sintering and Microwave Dielectric Properties of $(ZnMg)TiO_3$ System ($(ZHMg)TiO_3$계 세라믹스의 저온소결과 마이크로파 유전특성)

  • Sim, Woo-Sung;Bang, Jae-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.321-324
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    • 2003
  • The effects of various sintering additives such as $Bi_2O_3+V_2O_5$, $BiVO_4$, $B_2O_3$, and $CuO+V_2O_5$ on the low-temperature sintering and microwave dielectric properties of $(ZnMg)TiO_3$ system were studied. Sintering was enhanced by the sintering additives and highly dense samples were obtained for $(Zn_{0.8}Mg_{0.2})TiO_3$ at the sintering temperature of $910^{\circ}C$. $(Zn_{0.8}Mg_{0.2})TiO_3$ with 6.19 mol.%$B_2O_3$ was found to show the best sintering and microwave dielectric properties.

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A study on Sintering Characteristics of Commercial 7xxx Series Al Alloy Powders (상용 7xxx Series Al 합금계 혼합분말의 소결 특성)

  • ;;;Panyu
    • Journal of Korean Powder Metallurgy Institute
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    • v.11 no.1
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    • pp.69-73
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    • 2004
  • The sintering characteristics of commercial 7xxx series Al-Zn-Mg-Cu alloy have been investigated. Sintering system of this blended elemental powder has aspects of both transient and supersolidus liquid phase sintering. Transient liquids occur when the constitution point during sintering lies in a solid phase region but where the sintering temperature is greater than either the melting point of one of the constituent or a eutectic temperature. Supersolidus liquid phase sintering occurs when a preblended powder is heated to a temperature between the solidus and liquids. However, these reaction were restrained their inter diffusion due to the appearance of the oxide film. Thus, 7xxx series Al alloy is extremely sensitive to process variables, including particle size, holding time and sintering temperature. Therefore, above phenomenons were observed formation and behaviour of the liquid by using SEM and DSC.

Comparison of fracture strength and color of zirconia copings according to multi-layer zirconia blocks and sintering method (다층 지르코니아 블록 종류와 소결방법에 따른 지르코니아 코핑의 파절강도와 색조 비교)

  • Kang, Jae-Min;Kim, Won-Young;Chung, In-Sung
    • The Journal of Korean Academy of Dental Technology
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    • v.41 no.3
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    • pp.195-201
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    • 2019
  • Purpose: This study was investigated the effect of multilayer zirconia block type and sintering method on fracture strength, micro structure and color of zirconia copings. Methods: Three kinds of multi-layered zirconia blocks were used to identify the effects of the kinds of multi-layered zirconia blocks and sintering methods on fracture strength and color reproducibility of zirconia copings. 60 Zirconia copings were fabricated and fracture strength, micro structure and color reproducibility were compared and evaluated. Results: In all the blocks, the CS group, which refers to the general sintering method had higher fracture strength of zirconia copings than the MS group that refers to the microwave sintering method(MCS/MMS; 2,107.5N/1,930.4N, DCS/DMS; 917.0N/879.1N, UCS/UMS; 2,256.9/2,050.7N). In relation to CIE $L^*$, $a^*$, $b^*$ values of zirconia copings depending on the kinds of multi-layered zirconia blocks and sintering methods, the MS group using the microwave sintering method had lower brightness and chroma than the CS group using the general sintering method. Conclusion: In all the blocks, the CS group(general sintering) had higher fracture strength of zirconia copings than the MS group(microwave sintering). In relation to CIE $L^*$, $a^*$, $b^*$ values of zirconia copings depending on the kinds of multilayered zirconia blocks and sintering methods, the MS group using the microwave sintering method had lower brightness and chroma than the CS group using the general sintering method.

Sintering of Fe-30 wt% TiC Composite Powders Fabricated from (Fe, TiH2, C) Powder Mixture ((Fe, TiH2, C) 혼합 분말로부터 제조된 Fe-30 wt% TiC 복합재료 분말의 소결)

  • Lee, Byunghoon;Kim, Ji Soon
    • Journal of Korean Powder Metallurgy Institute
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    • v.22 no.5
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    • pp.356-361
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    • 2015
  • Fe-30 wt% TiC composite powders are fabricated by in situ reaction synthesis after planetary ball milling of (Fe, $TiH_2$, Carbon) powder mixture. Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-30 wt% TiC composite powder compacts. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C/min$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts are not densified even after sintering at $1300^{\circ}C$ for 3 h, which shows a relative denstiy of 66.9%. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly full densification of 99.6% relative density under the sintering pressure of 50 MPa.

Densification of Cu-50%Cr Powder Compacts and Properties of the Sintered Compacts (Cu-50%Cr 분말성형체의 치밀화 및 소결체 물성)

  • 김미진;정재필;도정만;박종구;홍경태
    • Journal of Korean Powder Metallurgy Institute
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    • v.7 no.4
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    • pp.218-227
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    • 2000
  • It is well known that the Cu-Cr alloys are very difficult to be made by conventional sintering methods. This difficulty originates both from limited solubility of Cr in the Cu matrix and from limited sintering temperature due to high vapor pressures of Cr and Cu components at the high temperature. Densification of Cu-50%Cr Powder compacts by conventional Powder metallurgy Process has been studied. Three kinds of sintering methods were tested in order to obtain high-density sintered compacts. Completely densified Cu-Cr compacts could be obtained neither by solid state sintering method nor by liquid phase sintering method. Both low degree of shrinkage and evolution of large pores in the Cu matrix during the solid state sintering are attributed to the anchoring effect of large Cr particles, which inhibits homogeneous densification of Cu matrix and induces pore generation in the Cu matrix. In addition, the effect of undiffusible gas coming from the reduction of Cu-oxide and Cr-oxide was observed during liquid phase sintering. A two-step sintering method, solid state sintering followed by liquid phase sintering, was proved to have beneficial effect on the fabrication of high-dendsity Cu-Cr sintered compacts. The sintered compacts have properties similar to those of commercial products.

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Microstructures and Mechanical Properties of $TiC-Ni_3Al$ Cermet ($TiC-Ni_3Al$ Cermet의 미세조직과 기계적성질)

  • 손호민;이완재
    • Journal of Korean Powder Metallurgy Institute
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    • v.5 no.4
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    • pp.286-292
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    • 1998
  • Ni$_3$Al intermetallic compound has been tested as a binder phase, in order to improve the oxidation resistance and the mechanical properties of TiC-Ni cermet at a high temperature. The wettability of $Ni_3Al$ on TiC and the optimum sintering condition were investigated in TiC-(30, 40) vol% $Ni_3Al$ cermets with the sintering temperature (1380~$1430^{\circ}C$) and time (30~99 min). The results are summarized as follows: 1) Ni$_3$Al showed good wettability on TiC above 1400$^{\circ}C$ ; 2) The shrinkages of the specimens increased with the sintering temperature, the sintering time and the binder content, whereas the relative densities were decreased; 3) Any other phase did not appeared in the microstructures of all sintered cermets. The grain sizes of TiC became larger as the sintering temperature and the sintering time as well as the binder content increased; 4) The hardness of the cermets decreased with increase in the sintering temperature and the sintering time as well as the binder content; 5) The transverse-rupture strength of the cermets increased with the sintering temperature and the sintering time, whereas it decreased with the binder content.

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Effect of MgO Addition Affecting in Zirconia-Frit Composites' Sintering and Properties of Matter (Zirconia-Frit composites의 소결 및 물성에 미치는 MgO 첨가의 효과)

  • Kwon, Eun-Ja;Lee, Gyu-Sun
    • The Journal of Korean Academy of Dental Technology
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    • v.32 no.1
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    • pp.9-16
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    • 2010
  • This study sought to apply different MgO additions to Zirconia (20wt % Frit) and thereby determine its mechanical properties depending upon variation of temperature, as a part of elementary study. First, in terms of sintering density depending on sintering conditions, it was found that sintering density increased as temperature varied from $1100^{\circ}C$ to $1300^{\circ}C$. As the addition of MgO increased, it was found that sintering density tended to decrease at each temperature. For the maximum sintering density obtained from pellet, it was found that 3wt% MgO addition specimens sintered at $1300^{\circ}C$ had its maximum sintering density as high as 97.39%. This study measured mechanical properties of these specimens, and it was found that their bending strength tended to decrease as the content of MgO addition increased. And it was found that their bending strength reached up to 162 MPa when 3wt% MgO was added to them for sintering process at $1300^{\circ}\Delta C$. It was also found that those specimens had Vickers microhardness up to 4.6 GPa when 5wt% MgO was added to them for sintering process at $1300^{\circ}C$.

On the Properties and Synthesis of Nanostructured W-Cu alloys by Mechanical Alloying(II) Sintering Behavior of MA NS W-Cu Composite Powders (기계적 합금화 방법으로 제조된 nanostructured W-Cu 합금의 제조 및 물성 연구(II) -MA NS W-Cu 복합분말의 소결거동-)

  • 김진천
    • Journal of Korean Powder Metallurgy Institute
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    • v.5 no.2
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    • pp.89-97
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    • 1998
  • Sintering behavior of nanostructured(NS) W-Cu powders prepared by mechanical alloying (MA) was investigated as a function of sintering temperature. MA NS W-2owt%Cu and W-3owt%Cu composite powders with the crystal size of 20-30 nm were annealed at 90$0^{\circ}C$, and thermal characteristics of those powders were investigated by DSC. Sintering behavior of MA NS W-Cu composite powders was investigated during the solid-state sintering and the Cu-liquid phase sintering. The new nanosintering phenonenon of MA W-Cu powders at solid-state sintering temperature was suggested to explain the W-grain growth in the inside of MA powders. The sintering densification of MA NS W-Cu powders was enhanced at Cu melting temperature by arrangement of MA powders, i.e., the first rearrangement of MA powders was occurred, and then the rearrangement of W-grains in the sintered parts was also took place during liquid-phase sintering, i.e., the second rearrangement was happened. Due to the double rearrangement process of MA NS W-Cu powders, the high sintered density with more than 96%o was obtained and the fine and high homogeneous state of W and Cu phases was achieved by sintering at 1200 $^{\circ}C$.

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