• Title, Summary, Keyword: SiC

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Effect of Si Addition on Resistivity of Porous SiC-Si Composite for Heating Element Application (다공성 SiC-Si 복합체의 전기비저항에 미치는 Si 첨가량의 영향)

  • Jun, Shinhee;Lee, Wonjoo;Kong, Young-Min
    • Korean Journal of Materials Research
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    • v.25 no.5
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    • pp.258-263
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    • 2015
  • To fabricate porous SiC-Si composites for heating element applications, both SiC powders and Si powders were mixed and sintered together. The properties of the sintered SiC-Si body were investigated as a function of SiC particle size and/or Si particle contents from 10 wt% to 40 wt%, respectively. Porous SiC-Si composites were fabricated by Si bonded reaction at a sintering temperature of $1650^{\circ}C$ for 80 min. The microstructure and phase analysis of SiC-Si composites that depend on Si particle contents were characterized using scanning electron microscope and X-ray diffraction. The electrical resistivity of SiC-Si composites was also evaluated using a 4-point probe resistivity method. The electrical resistivity of the sintered SiC-Si body sharply decreased as the amount of Si addition increased. We found that the electrical resistivity of porous SiC-Si composites is closely related to the amount of Si added and at least 20 wt% Si are needed in order to apply the SiCSi composites to the heating element.

6H-SiC epitaxial growth and crystal structure analysis (6H-SiC 에피층 성장과 결정구조 해석)

  • Kook-Sang Park;Ky-Am Lee
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.2
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    • pp.197-206
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    • 1997
  • A SiC epilayer on the 6H-SiC crystal substrate was grown by chemical vapor deposition (CVD). The crystal structure of the SiC epilayer was investigated by using the X-ray diffraction patterns and the Roman scattering spectroscopy. The SiC epilayer on the 6H-SiC substrate was grown to be homoepilayer by CVD. In order to distinguish a certain SiC polytype mixed in the SiC crystal grown by the modified Lely method, we have calculated the X-ray diffraction intensities and Brags angles of the typical SiC crystal powders. By comparing the measured X-ray diffraction pattern with the calculated ones, it was identified that the SiC crystal grown by the modified Lely method was the 6H-SiC crystal mixed some 15R-SiC.

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Study on Improvement of Mechanical Property, Oxidation and Erosion Resistance of SiC Matrix Ceramic Composites Reinforced by Hybrid Fabric Composed of SiC and Carbon Fiber (탄화규소섬유와 탄소섬유 하이브리드 직물을 강화재로 한 SiC 매트릭스 세라믹복합재의 기계적물성, 산화 및 삭마 저항성 개선 연구)

  • Yoon, Byungil;Kim, Myeongju;Kim, Jaesung;Kwon, Hyangjoo;Youn, Sungtae;Kim, Jungil
    • Composites Research
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    • v.32 no.3
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    • pp.148-157
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    • 2019
  • In this study, $C_f/SiC$, $SiC_f/SiC$ and $C_f-SiC_f/SiC$ ceramic composites reinforcing carbon fiber, SiC fiber and hybrid fiber were fabricated by hybrid TGCVI and PIP process. After the thermal shock cycle, 3-point bending and Oxy-Acetylene torch test, their mechanical behavior, oxidation and erosion resistance were evaluated. The $C_f/SiC$ composite showed a decrease in mechanical property along with increasing temperature, a pseudo-ductile fracture mode and a large quantity of erosion. The $SiC_f/SiC$ composite exhibited stronger mechanical property and lower erosion rate compared to the $C_f/SiC$, but brittle fracture mode. On the other hand, hybrid type of $C_f-SiC_f/SiC$ composite gave the best mechanical property, more ductile failure mode than the $SiC_f/SiC$, and lower erosion rate than the $C_f/SiC$. During the Oxy-Acetylene torch test, the $SiO_2$ formed by reaction of the SiC matrix with oxygen prevented further oxidation or erosion of the fibers for $C_f-SiC_f/SiC$ and $SiC_f/SiC$ composites particularly. In conclusion, if a hybrid composite with low porosity is prepared, this material is expected to have high applicability as a high temperature thermo-structural composite under high temperature oxidation atmosphere by improving low mechanical property due to the oxidation of $C_f/SiC$ and brittle fracture mode of $SiC_f/SiC$ composite.

$\beta$-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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High Temeprature Strength Property of Continuous SiC Fiber Reinforced SiC Matrix Composites (SiC 장섬유 강화 SiC 기지 복합재료의 고온강도 특성)

  • Shin, Yun-Seok;Lee, Sang-Pil;Lee, Jin-Kyung;Lee, Joon-Hyun
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.102-105
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    • 2005
  • The mechanical properties of $SiC_f/SiC$ composites reinforced with continuous SiC fiber have been investigated in conjunction with the detailed analysis of their microstructures. Especially, the effect of test temperature on the characterization of $SiC_f/SiC$ composites was examined. In this composite system, a braiding Hi-Nicalon SiC fibric was selected as a reinforcement. $SiC_f/SiC$ composites have been fabricated by the reaction sintering process, using the complex matrix slurry with a constant composition ratio of SiC and C particles. The characterization of $RS-SiC_f/SiC$ composites was investigated by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the high temperature applicability of $RS-SiC_f/SiC$ composites was discussed.

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Fabrication of $Al_2O_3/SiC$ Composite Through Oxidation of SiC (SiC의 산화에 의한 $Al_2O_3/SiC$ 복합체의 제조)

  • 김경환;이홍림;이형민;홍기곤
    • Journal of the Korean Ceramic Society
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    • v.34 no.5
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    • pp.535-543
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    • 1997
  • The surface of SiC particles were partially oxidized to produce SiO2 layers on the SiC particles to prepare Al2O3/SiC composite by formation of mullite bonds between the grains of Al2O3 and SiC during sintering at 1$600^{\circ}C$. This process is considered to enable the sintering of Al2O3/SiC composite at lower temperature and also to relieve the stress, produced by thermal expansion mismatch between Al2O3 and SiC. In fact, Al2O3/SiC composite prepared by oxidation of SiC was observed to be more effectively sintered and densified at lower temperature. Maximum density, flexural strength and microhardness were obtained with 5.65 vol% of mullite content in Al2O3/SiC composite.

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Influence of Solidification Condition on the Segregation of SiC Particles in the Al-Si/$SiC_p$ Composites (Al-Si/$SiC_p$ 복합재료에서 SiC의 편석에 미치는 응고 조건의 영향)

  • Kim, Jong-Chan;Kwon, Hyuk-Moo
    • Journal of Korea Foundry Society
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    • v.17 no.2
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    • pp.180-187
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    • 1997
  • The influence of solidification condition on the segregation of SiC particles in the $Al-xSi/6wt%SiC_p$(x: 6, 10, 14, 18${\cdot}$wt%) composites was investigated in the study. The results are as follows: 1) During the counter-gravity unidirectional solidification of $Al-Si/SiC_p$ composites melt, most of the SiC particles are pushed to the top of the casting. 2) The SiC particles pushing in the $Al-Si/SiC_p$ composite melts are not observed, when the interface velocity of melts increases more than 1.41 ${\mu}m/sec$. 3) The SiC particles are entrapped in the interdendrite regions, when the sizes of SiC particles in the $Al-Si/SiC_p$ composites are large than ${\varphi}22{\mu}m$.

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Preparation of Si-SiC Composites by Si-Infiltration (Si 침윤에 의한 Si-SiC 복합체 제조)

  • 김인술;장주민;오기동;박홍채
    • Journal of the Korean Ceramic Society
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    • v.29 no.9
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    • pp.750-756
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    • 1992
  • Reaction bonded si-SiC composites were prepared by silicon infiltration technique at temperature of 1$600^{\circ}C$ for 30 minutes in vaccum atmosphere. The microstructure and mechanical properties of Si-SiC composites were investigated and characterized. UF-15 and SE-10 as SiC powders, phenolic resin and carbon black as carbon source, and metallic silicon powder as molten Si source were used as starting materials. New SiC crystallines nucleatd and grown by reaction of Si and C were detected by TEM and SEM-EDS. The bonding between new and original SiC was found to be strong. But the wetting of SiC by unreacted metallic Si and the rapid grain growth of new SiC decreased density and fracture toughness. Fracture toughness and modulus of rupture of Si-SiC composite were about 3.2 MPa.m1/2 and 480 MPa, respectively.

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Mechanical and Electrical Properties of Si-SiC Fabricated Using SiC-C Composite Powders Synthesized by Sol-gel Process (Sol-gel 법으로 합성된 SiC-C 복합분말을 사용하여 제조된 Si-SiC의 기계적 특성 및 전기저항 특성)

  • Youn, Sung Il;Cho, Gyung Sun;Youm, Mi Rae;Lim, Dae Soon;Park, Sang Whan
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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    • pp.459-465
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    • 2014
  • In this study, Si-SiC composites were fabricated using a Si melt infiltration method using ${\beta}$-SiC/C composite powders synthesized by the carbothermal reduction of $SiO_2-C$ precursors made from a TEOS and a phenol resin. The purity of the synthesized SiC-C composite powders was higher than 99.9993 wt% and the average particle size varied from 4 to $6{\mu}m$ with increasing carbon contents of the $SiO_2-C$ precursors. It was found that the Si-SiC composites fabricated in this study consist of ${\beta}$-SiC and residual Si, without any trace of ${\alpha}$-SiC. The 3-point bending strengths of the fabricated Si-SiC composites were measured and found to be higher than 550 MPa, although the density of the fabricated Si-SiC composite was less than $2.9g/cm^3$. The bending strengths and the densities of the fabricated Si-SiC composites were found to decrease with increasing C/Si mole ratios in the SiC-C composite powders. The specific resistivities of the Si-SiC composites fabricated using the SiC-C composite powders were less than $0.018{\Omega}cm$. With increasing C content in the SiC-C composite powders used for the fabrication of Si-SiC composites, the specific resistivity of the Si-SiC composites was found to slightly increase from 0.0157 to $0.018{\Omega}cm$.

The Frequency Characteristics of Elastic Wave by Crack Propagation of SiC/SiC Composites

  • Kim, J.W.;Nam, K.W.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.110-114
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    • 2012
  • We studied on the nondestructive evaluation of the elastic wave signal of SiC ceramics and SiC/SiC composite ceramics under monotonic tensile loading. The elastic wave signal of cross and unidirectional SiC/SiC composite ceramics were obtained by pencil lead method and bending test. It was applied for the time-frequency method which used by the discrete wavelet analysis algorithm. The time-frequency analysis provides time variation of each frequency component involved in a waveform, which makes it possible to evaluate the contribution of SiC fiber frequency. The results were compared with the characteristic of frequency group from SiC slurry and fiber. Based on the results, if it is possible to shift up and design as a higher frequency group, we will can make the superior material better than those of exiting SiC/SiC composites.

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