• Title/Summary/Keyword: Liquid-phase-sintering

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Sintering and the Electrical Properties of Co-doped $ZnO-Bi_2O_3-Sb_2O_3$ Varistor System (Co를 첨가한 $ZnO-Bi_2O_3-Sb_2O_3$ 바리스터의 소결 및 전기적 특성)

  • 김철홍;김진호
    • Journal of the Korean Ceramic Society
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    • v.37 no.2
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    • pp.186-193
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    • 2000

  • Effects of 1.0 mol% CoO addition on sintering and the electrical properties of ZnO-Bi2O3-Sb2O3(ZBS) varistor system with 3.0 mol% co-addition of Sb2O3 and Bi2O3 at various Sb/Bi ratio (0.5, 1.0, and 2.0) were investigated. Cobalt had little influence on the liquid-phase formation and the pyrochlore decomposition temepratures of ZBS, while densification was mainly dependent on Sb/Bi ratio: when Sb/Bi=0.5, excess Bi2O3 irrelevant to the formation of pyrochore(Zn2Sb3Bi3O14) forms eutectic liquid at ~75$0^{\circ}C$ which promotes densification and grain growth; with Sb/Bi=2.0, the second phase Zn7Sb2O12 formed by excess Sb2O3 irrelevant to the formation of the pyrochlore retards densification up to ~100$0^{\circ}C$. These phases caused the coarsening and uneven distribution of the second phase particles on the grain boundaries of ZnO above the pyrochlore decomposition temperature(~105$0^{\circ}C$), which led to broad size dist-ribution of ZnO; the specimen with Sb/Bi=1.0 showed homogeneous microstructure compared with the others, which enabled improved varistor characteristics. Doping of Co increased the nonlinearity and the potential barrier height of ZBS, which is thought to stem from improved sintering behavior such as homogenized microstructure due to size reduction and even distribution of the second phase and suppressed volatility of Bi2O3, as well as the improvement in the potential barrier structure via increased donor and interface electron trap densities.

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The Effect of Sintering Parameters on the Densification Behavior of PM High Speed Steel (분말 고속도공구강의 소결 조건에 따른 치밀화 거동연구)

  • 김용진
    • Journal of Powder Materials
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    • v.1 no.2
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    • pp.190-197
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    • 1994

  • The densification behavior during a sintering of M2 and T15 grade high speed steel powder compacts was reported. Sintered densities over 98% theoretical were achieved by a liquid phase sintering in vacuum for both grades. The optimum sintering temperature range where full densification could be achieved without excessive carbide coarsening and incipient melting was much narrower in M2 than in T15 grade. The sintering response was mainly affected by the type of carbides present. The primary carbides in M2 were identified as $M_6C$ type whereas those in T15 were MC type which provides wider sintering range. The addition of elemental carbon up to 0.3% lowered the optimum sintering temperature for both grades, but had little effect on expanding the sintering range and sintered structure.

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Behaviors of Grain Growth in Carbide Added TiC Matrix Cermets (탄화물첨가 TiC기지 서멧의 입성장 거동)

  • Shin, Soon-GI;Lee, Jun-Hee;Lee, Hwa-Sang
    • Korean Journal of Materials Research
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    • v.12 no.10
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    • pp.825-830
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    • 2002

  • The growth rate of solid grains in TiC-XC-2vol% and TiC-XC-30vo1% Ni cermets, where X=Zr, W or Mo, was fitted to an equation of the form $d^3$-$do^3$=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with addition of $Mo_2$C or WC and increased with addition of ZrC. The contiguity ratio was greater in the alloys with smaller growth rate constant and decreased with increasing Ni content in the $TiC-Mo_2$C-Ni cermet. The grain growth mechanism could be explained by the effect of contiguous grain boundaries in restricting the overall grain growth.

  • https://doi.org/10.3740/MRSK.2002.12.10.825 인용 PDF KSCI

Study of TiCN Aditions to an 2xxx Series Aluminium Alloy

  • Ruiz-Navas, E.M.;Delgado, Tienda M.L.;Benito, Gonzalez S.;Gordo, E.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1037-1038
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    • 2006

  • The increasing demand of PM parts for automobile and aerospace applications has caused a strong development of the aluminium based metal matrix composites (MMCs).Aluminium alloys are one of most widely used materials as matrix in MMCs, both in research and development as well as in industrial applications. In the present work, the influence of the ceramic reinforcement addition to a 2xxx series aluminium alloy is studied. Several percentages of TiCN have been added to the Al-Cu alloy using PM techniques, in order to analyze its influence on the liquid phase sintering process and on the final properties of the material.

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