• Title/Summary/Keyword: $Si_3N_4$ composites

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Effect of Cutting Tool Materials on Surface Roughness and Cutting Forces in Machining of $Al-Si_3N_4$ Composite Produced by Powder Metallurgy

  • Ozcatalbas, Yusuf;Bahceci, Ersin;Turker, Mehmet
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1052-1053
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    • 2006
  • Aluminum-based composites reinforced with various amounts of $\alpha-Si_3N_4$ were produced by powder metallurgy (P/M). The machinability properties of $MMC_s$ were determined by means of cutting forces and surface roughness. Machining tests were carried out by using PCD and K10 tools. Increasing of $Si_3N_4$ volume fraction in the matrix resulted in a decrease of the surface roughness and turning forces. PCD cutting tools showed better cutting performance than K10 tools.

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Tribological Properties of Hot Pressed SiC/$Si_3$$N_4$/SiCw Composites (가압소결 SiC/$Si_3$$N_4$/SiCw 복합체의 마찰마모특성)

  • Baik, Yong-Hyuck;Choi, Woong;Kang, Seon-Myung;Park, Yong-Kap
    • Journal of the Korean Ceramic Society
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    • v.37 no.11
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    • pp.1039-1043
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    • 2000
  • $\alpha$-Si$_3$N$_4$가 20vol% 혼합된 SiC/Si$_3$N$_4$혼합물에서 $\alpha$-SiC의 일부를 SiC whisker로 치환하여 첨가한 후 180$0^{\circ}C$, 25MPa의 압력으로 hot pressing하여 SiC/Si$_3$N$_4$/SiCw 복합체를 제조하였다. SiC whisker의 첨가 함량이 증가할수록 상대밀도, 꺽임강도, 마모 저항성은 감소되었으나, 파괴인성은 크게 향상되었다. $\alpha$-SiC의 일부를 SiC whisker로의 치환은 치밀화를 억제하였으나 파괴인성의 증가는 마모 저항성을 향상시키지 않았다.

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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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Effect of Elastic/Plastic Mismatch on the Contact Crack Initiation in Asymmetric Layered Composite (층상형 비대칭성 복합재료의 탄성/소성 불일치가 접촉 균열의 개시에 미치는 영향)

  • Kim, Sang-Kyum;Lee, Kee-Sung
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.195-198
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    • 2005
  • The role of elastic/plastic mismatch on the contact crack initiation is investigated for designing desirable surface-coated asymmetric layered composites. Various layered composites such as $Si_3N_4$ ceramics on $Si_3N_4+BN$ composite, soda-lime glass on various substrates with different elastic modulus for the analysis. Spherical indentation is conducted for producing contact cracks from the surface or interface between the coating and the substrate layer. A finite element analysis of the stress fields in the loaded layer composites enables a direct correlation between the damage patterns and the stress distributions. Implications of these conclusions concerning the design of asymmetric layered composites indicate that the elastic modulus mismatch is one of the important parameter for designing layered composite to prevent the initiation of contact cracks.

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Rapid Sintering and Synthesis of a Nanocrystalline Fe-Si3N4 Composites by High-Frequency Induction Heating (고주파유도 가열에 의한 나노구조 Fe-Si3N4 복합재료의 합성 및 급속소결)

  • Ko, In-Yong;Du, Song-Lee;Doh, Jung-Mann;Yoon, Jin-Kook;Park, Sang-Whan;Shon, In-Jin
    • Korean Journal of Metals and Materials
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    • v.49 no.9
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    • pp.715-719
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    • 2011
  • Nanopowders of $Fe_3N$ and Si were fabricated by high-energy ball milling. A dense nanostructured $12Fe-Si_3N_4$ composite was simultaneously synthesized and consolidated using a high-frequency induction-heated sintering method for 2 minutes or less from mechanically activated powders of $Fe_3N$ and Si. Highly dense $12Fe-Si_3N_4$ with a relative density of up to 99% was produced under simultaneous application of 80 MPa pressure and the induced current. The microstructure and mechanical properties of the composite were investigated.

Effect of Sintering Additives and Sintering Temperature on Mechanical Properties of the $Si_3N_4$ Composites Containing Aligned $\beta-Si_3N_4$ Whisker (배향된 $\beta-Si_3N_4$ Whisker를 함유하는 $Si_3N_4$ 복합체의 기계적 특성에 미치는 소결조제와 소결온도의 영향)

  • Kim, Chang-Won;Choi, Myoung-Jae;Park, Chan;Park, Dong-Soo
    • Journal of the Korean Ceramic Society
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    • v.37 no.1
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    • pp.21-25
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    • 2000
  • Gas pressure sintered silicon nitride based composites with 5 wt% $\beta$-Si3N4 whiskers were prepared, and the variations depending on sintering additives and sintering temperature were studied. Sintering additives were 6 wt% Y2O3-1 wt% MgO(6Y1M), 6 wt%Y2O3-1 wt% Al2O3(6Y1A), 6 wt% Y2O3-1 wt% SiO2(6Y1S), and whiskers were unidirectionally oriented by a modified tape casting technique. Samples were fully densified by gas pressure sintering at 2148 K and 2273 K. As the sintering temperature increased, the size of large elongated grains was increased. Three point flexural strength of 6Y1M and 6Y1M samples was higher than that of 6Y1S sample, and the strength decreased as the sintering temperature increased. The indentation crack length became shorter for the sample sintered at higher temperature, and the difference between the cracks length parallel to and normal to the direction of whisker alignment was decreased. In case of cracks 45$^{\circ}$off the whisker alignment direction, the crack length anisotropy disappeared.

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FABRICATION AND MATERIAL ISSUES FOR THE APPLICATION OF SiC COMPOSITES TO LWR FUEL CLADDING

  • Kim, Weon-Ju;Kim, Daejong;Park, Ji Yeon
    • Nuclear Engineering and Technology
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    • v.45 no.4
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    • pp.565-572
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    • 2013
  • The fabrication methods and requirements of the fiber, interphase, and matrix of nuclear grade $SiC_f/SiC$ composites are briefly reviewed. A CVI-processed $SiC_f/SiC$ composite with a PyC or $(PyC-SiC)_n$ interphase utilizing Hi-Nicalon Type S or Tyranno SA3 fiber is currently the best combination in terms of the irradiation performance. We also describe important material issues for the application of SiC composites to LWR fuel cladding. The kinetics of the SiC corrosion under LWR conditions needs to be clarified to confirm the possibility of a burn-up extension and the cost-benefit effect of the SiC composite cladding. In addition, the development of end-plug joining technology and fission products retention capability of the ceramic composite tube would be key challenges for the successful application of SiC composite cladding.

Materials Development in α-Sialon Ceramics

  • Mitomo Mamoru;Xie Rong-Jun;Hirosaki Naoto
    • Journal of the Korean Ceramic Society
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    • v.43 no.8 s.291
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    • pp.451-457
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    • 2006
  • The solid solutions of ${\alpha}-Si_3N_4$, i.e. ${\alpha}$-sialons, are represented by a general formula of $M_x(Si,Al)_{12}(O,N)_{16}$, in which metal ions (M) dissolve into interstitial sites to stabilize the structure. Processing methods for the fabrication of ${\alpha}/{\beta}$-sialon composites, ${\alpha}-sialon/{\beta}Si_3N_4$ composites, refractory or tough ${\alpha}$-sialon ceramics have been developed to tailor the mechanical properties. Translucent and photoluminescent properties have been investigated recently. A number of applications of ${\alpha}$-sialon ceramics as engineering and optical ceramics are also presented.

Effect of Alumina Coating on Mechanical Properties of SiC Whisker Reinforced Silicon Nitrate Ceramic Composite

  • Lee, Ki-Ju;Xu, Jing-Wen;Hwang, Woon-Suk;Cho, Won-Seung
    • Corrosion Science and Technology
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    • v.6 no.1
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    • pp.24-28
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    • 2007
  • Alumina coated SiC whiskers were prepared by homogeneous precipitation of aluminum sulfate. The Si3N4 composites reinforced with coated SiC whiskers were fabricated by hot-pressing at $1800^{\circ}C$ for 2 h under an $N_{2}$ atmosphere of 0.1 MPa to examine the effects of coated whiskers on the mechanical properties of SiC whisker reinforced $Si_{3}N_{4}$ composite. By the addition of alumina coated SiC whiskers instead of as received ones, the fracture toughness of composite was about 6.7 $MPam^{1/2}$ which was slightly lower than as received SiC whisker reinforced composite. This result seems to be caused by the fact that the crack deflection and whisker pull-out were decreased. Thus, alumina coated SiC whiskers were considered to form relatively strong interface bond with $Si_{3}N_{4}$ matrix.