• Title/Summary/Keyword: SiC particle size

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Application of Friction Stir Process to Improve Surface Reliability of Light Weight Magnesium Alloy (경량 마그네슘 합금의 표면 신뢰성 향상을 위한 마찰교반공정의 적용)

  • Gil, Ung-Chan;Kim, Jae-Yeon;Hyun, Chang-Young
    • Journal of Applied Reliability
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    • v.16 no.2
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    • pp.155-161
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    • 2016
  • Purpose: Purpose of this study is to analyze the effect of particle size as well as number of pass on surface microstructure and hardness of SiC(p)/AZ31 surface composite fabricated by friction stir process (FSP). Method: SiC(p)/AZ31 surface composite containing different size of SiC particle (i. e., $2{\mu}m$ and $8{\mu}m$) was fabricated by multi-pass FSP. Microstructure was observed by scanning electron microscope and surface hardness was determined by Vickers hardness tester. Results: For all the FSPed specimens with and without hardening particles, grain size was refined due to dynamic recrystallization behavior. Surface hardness was observed to increase with decreasing particle size in the composite layer. Increasing number of FSP pass was effective for homogeneous distribution of the hardening particles and for resulting increase in surface hardness. Conclusion: FSP was effective to modify surface microstructure for improving surface hardness of SiC/AZ31 composite.

Thermal and Mechanical Properties of ZrB2-SiC Ceramics Fabricated by Hot Pressing with Change in Ratio of Submicron to Nano Size of SiC (서브마이크론/나노 크기의 SiC 비율변화에 따른 ZrB2-SiC 세라믹스의 열적, 기계적 특성)

  • Kim, Seongwon;Chae, Jung-Min;Lee, Sung-Min;Oh, Yoon-Suk;Kim, Hyung-Tae
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.410-415
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    • 2013
  • $ZrB_2$-SiC ceramics are fabricated via hot pressing with different ratios of submicron or nano-sized SiC in a $ZrB_2$-20 vol%SiC system, in order to examine the effect of the SiC size ratio on the microstructures and physical properties, such as thermal conductivity, hardness, and flexural strength, of $ZrB_2$-SiC ceramics. Five different $ZrB_2$-SiC ceramics ($ZrB_2$-20 vol%[(1-x)SiC + xnanoSiC] where x = 0.0, 0.2, 0.5, 0.8, 1.0) are prepared in this study. The mean SiC particle sizes in the sintered bodies are highly dependent on the ratio of nano-sized SiC. The thermal conductivities of the $ZrB_2$-SiC ceramics increase with the ratio of nano-sized SiC, which is consistent with the percolation behavior. In addition, the $ZrB_2$-SiC ceramics with smaller mean SiC particle sizes exhibit enhanced mechanical properties, such as hardness and flexural strength, which can be explained using the Hall-Petch relation.

Effect of Deposition Temperature on the Property of Pyrolytic SiC Fabricated by the FBCVD Method (유동층 화학기상증착법을 이용하여 제조된 열분해 탄화규소의 특성에 미치는 증착온도의 영향)

  • Kim, Yeon-Ku;Kim, Weon-Ju;Yeo, SungHwan;Cho, Moon-Sung
    • Journal of Powder Materials
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    • v.21 no.6
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    • pp.434-440
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    • 2014
  • Silicon carbide(SiC) layer is particularly important tri-isotropic (TRISO) coating layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO coated particle. The high temperature deposition of SiC layer normally performed at $1500-1650^{\circ}C$ has a negative effect on the property of IPyC layer by increasing its anisotropy. To investigate the feasibility of lower temperature SiC deposition, the influence of deposition temperature on the property of SiC layer are examined in this study. While the SiC layer coated at $1500^{\circ}C$ obtains nearly stoichiometric composition, the composition of the SiC layer coated at $1300-1400^{\circ}C$ shows discrepancy from stoichiometric ratio(1:1). $3-7{\mu}m$ grain size of SiC layer coated at $1500^{\circ}C$ is decreased to sub-micrometer (< $1{\mu}m$) $-2{\mu}m$ grain size when coated at $1400^{\circ}C$, and further decreased to nano grain size when coated at $1300-1350^{\circ}C$. Moreover, the high density of SiC layer (${\geq}3.19g/cm^3$) which is easily obtained at $1500^{\circ}C$ coating is difficult to achieve at lower temperature owing to nano size pores. the density is remarkably decreased with decreasing SiC deposition temperature.

A Study on the Graded Ni-SiC Composite Coating by Electrodeposition (전해석출에 의한 단계적 Ni-SiC 복합코팅층 제조공정에 관한연)

  • 김선규
    • Journal of the Korean institute of surface engineering
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    • v.30 no.5
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    • pp.347-354
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    • 1997
  • Composite plating is a method of co-depositing fine particles of metallic, non-metallic compound or polymers in the plated layer to improve material properties such as were-resistance, lubrication, or corrosion resistance. Graded Ni-Sic composite coating were produced in this research. Prior to produce Graded Ni-SiC composite coatings, effects of particle size, particle content, pH of electrolyte, temperature, current density, stirring rate on the amount of SiC deposited in the Ni layer were investigated. By manipulating current density and plating time properties of these coating were evaluated by micro-indentation hardness test.

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Effect of SiC Particle Size on the Microstructure and Mechanical Properties Of Al2O3-SiC Composite (Al2O3-SiC 복합재료의 미세조직 및 기계적 물성에 미치는 SiC 원료분말의 크기 영향)

  • 채기웅
    • Journal of the Korean Ceramic Society
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    • v.41 no.2
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    • pp.125-130
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    • 2004
  • The effect of SiC particle size on the microstructures and mechanical properties of A1$_2$O$_3$-SiC composite was investigated. Two types of SiC powders having average particle sizes of 0.15 ${\mu}{\textrm}{m}$ and 3 ${\mu}{\textrm}{m}$ were used. The grain growth in the specimen containing 0.15 ${\mu}{\textrm}{m}$ SiC was effectively inhibited due to the fine SiC particles. However, after the formation of some abnormal grains, fast and exaggerated grain growth occurred which led to the microstructure of large grains with irregular shape. Fracture strength decreased due to the abnormal large grains. On the other hand, for specimen containing 3 ${\mu}{\textrm}{m}$ SiC showed normal grain growth behavior from initial sintering stage. Large SiC particles, however, effectively inhibited exaggerated grain growth after nucleation of a few abnormal grains. As a consequence, microstructure consisted of homogeneous elongated grains. In the A1$_2$O$_3$-2.5SiC(0.15 ${\mu}{\textrm}{m}$)-2.5SIC(3 ${\mu}{\textrm}{m}$) composite fabricated by mixing the two types of SiC powder, abnormal grain growth occurred. However, the good fracture strength was maintained regardless of microstructural changes in this specimen.

Manufacture of SiC matrix for PAFC (인산형 연료전지용 SiC MATRIX 제조)

  • 김영우;이주성
    • Journal of Energy Engineering
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    • v.2 no.2
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    • pp.187-193
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    • 1993
  • Porous matrices to contain and support phosphoric acid were prepared with PTFE as binder and SiC whisker or SiC powders of various particle size for phosphoric acid fuel cell(PAFC). Among the matrix characteristics the most important factors in stack performances were thought to be the bubble pressure and electrolyte wettability And then matrix was constructed to have pore size smaller than that of electrode. The bubble pressures and wettabilities of matrices manufactured with various size of SiC and different PTFE contents were investigated and related with the porosities measured by porosimeter, and then the optimum manufacturing condition of matrix for PAFC was determined.

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$\beta$-SiC Formation Mechanisms in Si Melt-C-SiC System (용융 Si-C-SiC계에서 $\beta$-SiC 생성기구)

  • 서기식;박상환;송휴섭
    • Journal of the Korean Ceramic Society
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    • v.36 no.6
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    • pp.655-661
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    • 1999
  • ${\beta}$-SiC formation mechanism in Si melt-C-SiC system with varying in size of carbon source was investigated. A continuous reaction sintering process using Si melt infiltration method was adopted to control the reaction sintering time effectively. It was found that ${\beta}$-SiC formation mechanism in Si melt-C-SiC system was directly affected by the size of carbon source. In the Si melt-C-SiC system with large carbon source ${\beta}$-SiC formation mechanism could be divided into two stages depending on the reaction sintering time: in early stage of reaction sintering carbon dissolution in Si melt and precipitation of ${\beta}$-SiC was occurred preferentially and then SIC nucleation and growth was controlled by diffusion of carbon throughy the ${\beta}$-SiC layer formed on graphite particle. Furthmore a dissolution rate of graphite particles in Si melt could be accelerated by the infiltration of Si melt through basal plane of graphite crystalline.

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Current Status of $SiC_{f}/SiC$ Composites Material in Fusion Reactor

  • Yoon, Han-Ki;Lee, Sang-Pill
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.166-171
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    • 2007
  • The characterization of monolithic SiC and SiCf/SiC composite materials fabricated by NITE and RS processes was investigated in conjunction with the detailed analysis of their microstructure and density. The NITE-SiC based materials were fabricated, using a SiC powder with average size of 30 nm. RS- SiCf/SiC composites were fabricated with a complex slurry of C and SiC powder. In the RS process, the average size of starting SiC particle and the blending ratio of C/SiC powder were $0.4\;{\mu}m$ and 0.4, respectively. The reinforcing materials for /SiC composites were BN-SiC coated Hi-Nicalon SiC fiber, unidirectional or plain woven Tyranno SA SiC fiber. The characterization of all materials was examined by the means of SEM, EDS and three point bending test. The density of NITE-SiCf/SiC composite increased with increasing the pressure holding time. RS-SiCf/SiC composites represented a great decrease of flexural strength at the temperature of $1000\;^{\circ}C.$

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A Study on the Mechanical Properties and Specific Resistivity of Reaction-Bonded Silicon Carbide According to α-SiC of Various Mixed Particle Size (반응소결 탄화규소의 다양한 α-SiC 조성에 따른 기계적 특성과 전기저항 특성에 관한 연구)

  • Kim, Young-Ju;Park, Young-Shik;Jung, Youn-Woong;Song, Jun-Baek;Park, So-Young;Im, Hang-Joon
    • Composites Research
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    • v.25 no.6
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    • pp.172-177
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    • 2012
  • For the manufacture of low resistance Si-SiC composite, the properties of reaction sintering in the green body of various mixed ${\alpha}$-SiC powder size with the various carbon contents from 0wt% to 20wt% were investigated. The samples preparation was green body by CIP method under this condition, molten silicon infiltration process was conducted to reaction bonded silicon carbide. the results of sintered density, 3-point bending strength and resistance of analysis showed that varied carbon and silicon melt reacted to convert to fine ${\beta}$-SiC particle and the structure was changed to dense material. The amount of fine ${\beta}$-SiC particle was gradually increased as carbon content increase. According to mixed composite, it's mechanical and specific resistivity properties was strongly influenced by carbon content within 10wt% more then carbon content 10wt% was strongly influenced by phase transition.