• Title/Summary/Keyword: pulse current sintering

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Microstructure and Sintering Behavior of ZnO Thermoelectric Materials Prepared by the Pulse-Current-Sintering Method

  • Shikatani, Noboru;Misawa, Tatsuya;Ohtsu, Yasunori;Fujita, Hiroharu;Kawakami, Yuji;Enjoji, Takashi
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.682-683
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    • 2006
  • Thermoelectric conversion efficiency of thermoelectric elements can be increased by using a structure combining n-type and p-type semiconductors. From the above point of view, attention was directed at ZnO as a candidate n-type semiconductor material and investigations were made. As the result, a dimensionless figure of merit ZT close to 0.28 (1073K) was obtained for specimens produced by the PCS (Pulse Current Sintering) method with addition of specified quantities of $TiO_2$, CoO, and $Al_2O_3$ to ZnO. It was found that the interstitial $TiO_2$ in the ZnO restrains the grain growth and CoO acts onto the bond between grains. The influence of the inclusion of $TiO_2$ and CoO onto the sintering behavior also was investigated.

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Influence of the Internal Current on the Sintering Behavior of ZnO Ceramics Sintered by PCS Method

  • Misawa, Tatsuya;Shikatani, Noboru;Kawakami, Yuji;Enjoji, Takashi;Ohtsu, Yasunori;Fujita, Hiroharu
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.538-539
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    • 2006
  • The influence of the internal current for the ZnO ceramics on the sintering behavior by pulse current sintering (PCS) method was investigated. To clear the dependence of inner current on the sintering behavior of ZnO ceramics, direct measurement of electric resistance of ZnO specimen under sintering by SPS device was carried out. It was observed that electric resistance of specimen decreases with increase in the temperature. The electric resistance begins to decrease from the low temperature of $200^{\circ}C$. The internal structure of sintered ZnO ceramics changed by the control of the internal current in the specimen using $Al_2O_3$ plate.

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Sintering Effect on Clamping Characteristics and Pulse Aging Behavior of ESD-Sensitive V2O5/Mn3O4/Nb2O5 Codoped Zinc Oxide Varistors

  • Nahm, Choon-Woo
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.6
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    • pp.308-311
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    • 2015
  • V2O5/Mn3O4/Nb2O5 codoped zinc oxide varistor ceramics were sintered at a temperature range as low as 875~950℃. The voltage clamping characteristics of V2O5/Mn3O4/Nb2O5 codoped zinc oxide varistor ceramics were investigated at a pulse current range of 1~50 A. The sintering temperature had a significant effect on clamp voltage ratio, which exhibits surge protection capabilities. The varistor ceramics sintered at 875℃ exhibited the best clamping characteristics, in which the clamp voltage ratio was 2.69 at a pulse current of 50 A. The varistor ceramics sintered at 900℃ exhibited the highest electrical stability, where = 3,824 V/cm (initial 3,909 V/cm), and E1 mA/cm2 = 27 (initial 39) after application of a pulse current of 100 A.

Fabrication and Property Evaluation of Cu-Mn Compacts for Sputtering Target Application by a Pulsed Current Activated Sintering Method (펄스전류활성소결법을 이용한 스퍼터링 타겟용 Cu-Mn 소결체 제조 및 특성평가)

  • Jang, Jun-Ho;Oh, Ik-Hyun;Lim, Jae-Won;Park, Hyun-Kuk
    • Journal of Powder Materials
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    • v.23 no.1
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    • pp.1-7
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    • 2016
  • Cu-Mn compacts are fabricated by the pulsed current activated sintering method (PCAS) for sputtering target application. For fabricating the compacts, optimized sintering conditions such as the temperature, pulse ratio, pressure, and heating rate are controlled during the sintering process. The final sintering temperature and heating rate required to fabricate the target materials having high density are $700^{\circ}C$ and $80^{\circ}C/min$, respectively. The heating directly progresses up to $700^{\circ}C$ with a 3 min holding time. The sputtering target materials having high relative density of 100% are fabricated by employing a uniaxial pressure of 60 MPa and a sintering temperature of $700^{\circ}C$ without any significant change in the grain size. Also, the shrinkage displacement of the Cu-Mn target materials considerably increases with an increase in the pressure at sintering temperatures up to $700^{\circ}C$.

Fabrication of Ultra Fine β-phase Ti-Nb-Sn-HA Composite by Pulse Current Activated Sintering

  • Woo, Kee-Do;Wang, Xiaopeng;Kang, Duck-Soo;Kim, Sang-Hyuk;Woo, Jeong-Nam;Park, Sang-Hoon;Liuc, Zhiguang
    • Journal of Powder Materials
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    • v.17 no.6
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    • pp.443-448
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    • 2010
  • The $\beta$ phase Ti-Nb-Sn-HA bio materials were successfully fabricated by high energy mechanical milling and pulse current activated sintering (PCAS). Ti-6Al-4V ELI alloy has been widely used as biomaterial. But the Al has been inducing Alzheimer disease and V is classified as toxic element. In this study, ultra fine sized Ti-Nb-Sn-HA powder was produced by high energy mechanical milling machine. The $\beta$ phase Ti-Nb-Sn-HA powders were obtained after 12hr milling from $\alpha$ phase. And ultra fine grain sized Ti-Nb-Sn-HA composites could be fabricated using PCAS without grain growth. After sintering, the microstructures and phase-transformation of Ti-Nb-Sn-HA biomaterials were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The relative density was obtained by Archimedes principle and the hardness was measured by Vickers hardness tester. The $\beta$-Ti phase was obtained after 12h milling. As result of hardness and relative density, 12h milled Ti-Nb-Sn-HA composite has the highest values.

Structure and Thermal Properties of a Ternary Al-Cr-Si Quenching Ribbon Manufactured by Single Roll Method (단일 롤 방법으로 제작한 3원계 Al-Cr-Si 급냉리본의 구조 및 열 특성)

  • Han, Chang-Suk;Kim, Ki-Woong;Kim, Woo-Suk
    • Korean Journal of Materials Research
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    • v.31 no.5
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    • pp.296-300
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    • 2021
  • Al-Cr-Si ternary quench ribbons are fabricated using a single roll method and investigated for their structural and thermal properties. In particular, the sinterability is examined by pulse current sintering to obtain the following results. The Al74Cr20Si6 composition becomes a quasicrystalline single phase; by reducing the amount of Cr, it becomes a two-phase mixed structure of Al phase and quasicrystalline phase. As a result of sintering of Al74Cr20Si6, Al77Cr13Si10 and Al90Cr6Si4 compositions, the sintering density is increased with the large amount of Al phase; the sintering density is the highest in Al90Cr6Si4 composition. In addition, as a result of investigating the effects of sintering temperature and pressurization on the sintered density of Al90Cr6Si4, a sintered compact of 99% or more at 513 K and 500 MPa is produced. In particular, since the Al-Cr-Si ternary crystal is more thermally stable than the Al-Cr binary quaternary crystal, it is possible to increase the sintering temperature by about 100 K. Therefore, using an alloy of Al90Cr6Si4 composition, a sintered compact having a sintered density of 99 % or more at 613 K and 250 MPa can be manufactured. It is possible to increase the sintering temperature by using the alloy system as a ternary system. As a result, it is possible to produce a sintered body with higher density than that possible using the binary system, and at half the pressure compared with the conventional Al-Cr binary system.

Influence of Compositions of Sintered Ti-Ni Alloys on their Thermo-mechanical Properties

  • Kyogoku, Hideki;Ikeda, Tetsuya;Komatsu, Shinichiro
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.81-82
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    • 2006
  • This paper presents the influence of the compositions of sintered Ti-Ni alloys on their thermo-mechanical properties. The Ti-Ni alloys having various compositions from 50at%Ni to 51at%Ni were sintered using elemental Ti and Ni powders by a pulse-current pressure sintering equipment. The deformation resistance in stress-strain curves increased with an increase in Ni content. In the case of Ti-50at%Ni, tensile strength and elongation were more than 500 MPa and 7%, respectively. The increase in Ni content also makes the transformation temperatures lower. The deformation resistance at a test temperature change from 293K and 353K in isothermal tensile test increased with elevating test temperature.

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