• Title/Summary/Keyword: Ceramics

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An Experimental Study on the Turning Machinability of Machinable Ceramics (Machinable Ceramics 의 가공 성능 평가를 위한 실험적 연구)

  • Gang, Jae-Hun;Lee, Jae-Gyeong
    • 한국기계연구소 소보
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    • pp.79-87
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    • 1990
  • Advanced ceramics have some excellent properties as the material for the mechanical component. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. Thus it is required also by a strong boom of demands for development of Machinable ceramics with high machinability in the most of industries. In present research, experiments are carried out to compare the machinability of sample Machinable ceramics. A $\ell$N(Aluminum Nitride) with additives of BN(Boron Nitride), yttrium. CaO are turned with cut-off tool type tungsten carbide bite using conventional turning machine.

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Grinding Characteristic of Advanced Ceramics (파인세라믹의 연삭가공특성)

  • Jung, Yoon-Gyo;Kang, Jae-Hoon
    • Journal of the Korean Society for Precision Engineering
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    • v.7 no.2
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    • pp.105-112
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    • 1990
  • Advanced ceramics have some excellent properities as the material for the mechanical component. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper, some experiments are carried out to find the basic grinding characteristic of advanced ceramics. Representative advanced ceramics, such as AL/sub 2/ O/sub 3/, ZrO/sub 2/, SiC and Si/sub 3/N/sub 4/and ground with diamond wheels. Special attention is paid to comparison between the conventional and creep feed grinding. Results obtained in this study provide some useful informations to attain the high efficiency grinding of advanced ceramics.

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A study on machining of high strength ceramics for automobile engine parts (자동차 엔진 부품용 고강도 세라믹스의 기계 가공에 관한 연구)

  • 강재훈
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.5
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    • pp.60-75
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    • 1990
  • Advanced Ceramics have some excellent prosperities as the material for the mechanical component. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this study, various machining experiments are carried out to obtain the basic knowledge of grinding High Strength Ceramics with high efficiency and precision for the purpose of application to Automobile parts. Advanced Engineering Ceramics such as Si$_{3}$N$_{4}$, SiC, ZrO$_{2}$, $Al_{2}$O$_{3}$ are ground with diamond wheels using conventional grinding machine. Results obtained in this study provide some useful informations to attain the high efficiency grinding of Advanced Ceramics.

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DC Accelerated Aging Characteristics of ZPCCL-Based Varistor Ceramics (ZPCCL계 바리스터 세라믹스의 DC 가속열화특성)

  • Kim, Hyang-Suk;Nahm, Choon-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.629-633
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    • 2002
  • The degradation behaviour of ZPCCL-based varistor ceramics composed of 97.5 mol%ZnO-0.5 mol% $Pr_6O_{11}-1.0$ mol% $Cr_2O_3-0.5$ mol% $La_2O_3$ was investigated under various DC accelerated aging streses. The varistor ceramics sintered for 1 h exhibited excellent nonlinearity, in which the nonlinear exponent is 81.6 and the leakage current is $0.2{\mu}A$. It was found that this varistor ceramics possess high stability, in which the variation rates of varistor voltage, nonlinear exponent, and leakage current are -1.14%, -3.7%, and 85.0%, respectively, against DC accelerated aging stress. On the contrary, the varistor ceramics sintered for 2 h also exhibited high nonlinearity and stability, but they were bad characteristics, compared with the varistor ceramics sintered for 1 h.

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Possible Strategies for Microstructure Control of Liquid-Phase-Sintered Silicon Carbide Ceramics

  • Chun, Yong-Seong;Kim, Young-Wook
    • Journal of the Korean Ceramic Society
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    • v.42 no.8
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    • pp.542-547
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    • 2005
  • Keys to the attainment of tailored properties in SiC ceramics are microstructure control and judicious selection of the sintering additives. In this study, three different strategies for controlling microstructure of liquid-phase-sintered SiC ceramics (LPS-SiC) have been suggested: control of the initial $\alpha-SiC$ content in the starting powder, a seeding technique, and a post-sintering heat treatment. The strategies suggested offer substantial flexibility for producing toughened SiC ceramics whereby grain size, grain size distribution, and aspect ratio can be effectively controlled. The present results suggest that the proposed strategies are suitable for the manufacture of toughened SiC ceramics with improved toughness.

Flexural Strength of Polysiloxane-Derived Strontium-Doped SiOC Ceramics

  • Eom, Jung-Hye;Kim, Young-Wook
    • Journal of the Korean Ceramic Society
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    • v.52 no.1
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    • pp.61-65
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    • 2015
  • The effect of Sr addition on the flexural strength of bulk SiOC ceramics was investigated in polymer-derived SiOC ceramics prepared by conventional hot pressing. Crack-free, dense SiOC discs with a 30 mm diameter were successfully fabricated from commercially available polysiloxane with 1 mol% strontium isopropoxide derived Sr as an additive. Agglomerates formed after the pyrolysis of polysiloxane led to the formation of domain-like structures. The flexural strength of bulk SiOC was strongly dependent on the domain size formed and Sr addition. Both the minimization of the agglomerate size in the starting powders by milling after pyrolysis and the addition of Sr, which reinforces the SiOC structure, are efficient ways to improve the flexural strength of bulk SiOC ceramics. The typical flexural strength of bulk Sr-doped SiOC ceramics fabricated from submicron-sized SiOC powders was ~209 MPa.