• 한국재료학회지
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• 제7권2호
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• pp.145-151
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• 1997

AI-xSi/ySiC( x:6~18wt%, y: 3~9wt%, SiC 입자크기: $10~28{\mu}m$) 복합재료를 재용해한 후 항온 유지하고 응고 시킬때 SiC 입자가 몰드의 하부로 침강하는 현상을 계통적으로 조사하였다. AI-Si/SiC 복합재료 용탕을 항온으로 유지하면 입자가 없는 지역은 유지시간이 약 처음 30분 동안 빠르게 증가한다. SiC 입자가 크기가 클수록 SiC입자의 크기가 클수록 SiC입자의 침강속도가 빠르다. 또한 복합재료중 철가한 SiC 입자의 부피분율이 증가하면 입자의 침강속도는 감소한다.

• 감성과학
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• 제24권4호
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• pp.149-156
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• 2021

본 연구에서는 1500℃ 이상의 극한 열 환경에서 사용되는 소재인 SiC (silicon carbide) 섬유를 복합방적사로 제조한 후에 원단을 제직하고 제직된 원단의 역학적 특성을 KES-FB system으로 측정하고 측정된 역학적 특성 값으로부터 착용성능을 분석하여 방화복으로의 활용 가능성을 알아보았다. 그 결과 직물의 역학적 특성에서는 인장선형성(LT)과 인장레질리언스(RT), 전단강성(G)을 나타내는 값이 원사의 제조형태에 따라서 그 특성 값의 차이를 보였으며, 직물의 두께와 평량, 밀도 값이 전단히스테리시스(2HG)와 압축레질리언스(RC) 값에 영향을 준다는 것을 알 수 있었다. 의복착용 성능에서는 착용 시 부피감을 나타내는 두께에 대한 압축에너지의 비(WC/T) 값에서 SiC 복합방적사로 제조된 직물의 값이 가장 우수한 값을 타나내었으며, 방염성능에서는 SiC 복합방적사로 제조된 직물이 탄화길이와 잔염시간에서 KFI 성능기준을 만족하여 방화복으로서의 활용이 가능함을 확인할 수 있었다.

• 한국세라믹학회지
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• 제51권5호
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• pp.430-434
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• 2014

$SiC_f$/SiC composites were prepared using the hybrid process of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP). Before the application of PIP, partially matrix-filled preform composites with different densities were fabricated by control of chemical vapor infiltration time and temperature. The changes of the final density of the $SiC_f$/SiC composites had a tendency similar to that of preform composites partially filled by CVI. Composites with lower density after the CVI process had a larger increment of density during the PIP process. Three types of microstructures were observed on the fractured surface of the composite: 1) well pulled-out fibers and lower density, 2) slightly pulled-out fibers and higher density, and 3) only bulk SiC. The different fractions and distributions of the microstructures could have an effect on the mechanical properties of the composites. In this study, $SiC_f$/SiC composites prepared using a hybrid process of CVI and PIP had density values in the range of $1.05{\sim}1.44g/cm^3$, tensile strength values in the range of 76.4 ~ 130.7 MPa, and fracture toughness values in the range of $11.2{\sim}13.5MPa{\cdot}m^{1/2}$.

• 대한금속재료학회지
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• 제48권5호
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• pp.417-423
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• 2010

A dense nanostructured MoSi$_{2}$-SiC composite was synthesized by a pulsed current activated combustion synthesis method within 2 min of one step from mechanically activated powders of Mo$_{2}$C and Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense MoSi$_{2}$-SiC with a relative density of up to 98% was produced under simultaneous application of an 80 MPa pressure and pulsed current. The average grain size and mechanical properties of the composite were investigated.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.158-161
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• 2006

SiC materials have been extensively studied for high temperature components in advanced energy conversion system and advanced gas turbine. However, the brittle characteristics of SiC such as law fracture toughness and law strain-to fracture impose a severe limitation on the practical applications of SiC materials. SiC/SiC composites can be considered as a promising candidate in various structural materials, because of their good fracture toughness. In this composite system, the direction of SiC fiber will give an effect to the mechanical properties. It is therefore important to control a properdirection of SiC fiber for the fabrication of high performance SiC/SiC composites. In this study, unidirection and two dimension woven structures of SiC/SiC composites were prepared starting from Tyranno SA fiber. SiC matrix was obtained by nano-powder infiltration and transient eutectoid (NITE) process. Effect of microstructure and density on the sintering temperature in NITE-SiC/SiC composites are described and discussed with the fiber direction of unidirection and two dimension woven structures.

• Advances in materials Research
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• 제5권1호
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• pp.55-66
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• 2016

This paper describes a study on the effects of $Mg_2Si_{(p)}$ addition on the microstructure, porosity, and mechanical properties namely hardness and tensile properties of AA332 composite. Each composite respectively contains 5, 10, 15, and 20 wt% reinforcement particles developed by a stir-casting. The molten composite was stirred at 600 rpm and melted at $900^{\circ}C{\pm}5^{\circ}C$. The $Mg_2Si$ particles were wrapped in an aluminum foil to keep them from burning when melting. The findings revealed that the microstructure of $Mg_2Si_{(p)}/AA332$ consists of ${\alpha}$-Al, binary eutectic ($Al+Mg_2Si$), $Mg_2Si$ particles, and intermetallic compound. The intermetallic compound was identified as Fe-rich and Cu-rich, formed as polygonal or blocky, Chinese script, needle-like, and polyhendrons or "skeleton like". The porosity of $Mg_2Si_{(p)}/AA332$ composite increased from 8-10% and the density decreased from 9-12% from as-cast. Mechanical properties such as hardness increased for over 42% from as-cast and the highest UTS, elongation, and maximum Q.I were achieved in the sample of 10% $Mg_2Si$. The study concludes that combined with AA332, the amount of 10 wt% of$Mg_2Si$ is a suitable reinforcement quantity with the combination ofAA332.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.342-351
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• 2010

The SiC-$ZrB_2$ composites were fabricated by combining 30, 35, 40, 45 and 50 vol. % of zirconium diboride ($ZrB_2$) powders with silicon carbide (SiC) matrix. The SiC-$ZrB_2$ composites and the sintered compacts were produced through spark plasma sintering (SPS) under argon atmosphere, and its physical, electrical, and mechanical properties were examined. Also, the thermal image analysis of the SiC-$ZrB_2$ composites was examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via x-ray diffraction (XRD) analysis. The apparent porosity of the SiC+30vol.%$ZrB_2$, SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$, SiC+45vol.%$ZrB_2$ and SiC+50vol.%$ZrB_2$ composites were 7.2546, 0.8920, 0.6038, 1.0981, and 10.0108%, respectively. The XRD phase analysis of the sintered compacts demonstrated a high phase of SiC and $ZrB_2$. Among the $SiC+ZrB_2$ composites, the SiC+50vol.%$ZrB_2$ composite had the lowest flexural strength, 290.54MPa, the other composites had more than 980MPa flexural strength except the SiC+30vol.%$ZrB_2$ composite; the SiC+40vol.%$ZrB_2$ composite had the highest flexural strength, 1011.34MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had positive temperature coefficient resistance (PTCR). The V-I characteristics of the SiC-$ZrB_2$ composites had a linear shape in the temperature range from room to $500^{\circ}C$. The electrical resistivities of the SiC+30vol.%$ZrB_2$, SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$ SiC+45vol.%$ZrB_2$ and SiC+50vol.%$ZrB_2$ composites were $4.573\times10^{-3}$, $1.554\times10^{-3}$, $9.365\times10^{-4}$, $6.999\times10^{-4}$, and $6.069\times10^{-4}\Omega{\cdot}cm$, respectively, at room temperature, and their resistance temperature coefficients were $1.896\times10^{-3}$, $3.064\times10^{-3}$, $3.169\times10^{-3}$, $3.097\times10^{-3}$, and $3.418\times10^{-3}/^{\circ}C$ in the temperature range from room to $500^{\circ}C$, respectively. Therefore, it is considered that among the sintered compacts the SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$ and SiC+45vol.%$ZrB_2$ composites containing the most outstanding mechanical properties as well as PTCR and V-I characteristics can be used as an energy friendly ceramic heater or ohmic-contact electrode material through SPS.

• 한국표면공학회지
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• 제38권3호
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• pp.89-94
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• 2005

We investigate the reaction stability of cobalt and nickel with side-wall materials of $SiO_2\;and\;Si_3N_4$. We deposited 15nm-Co and 15nm-Ni on $SiO_2(200nm)/p-type$ Si(100) and $Si_3N_4(70 nm)/p-type$ Si(100). The samples were annealed at the temperatures of $700\~1100^{\circ}C$ for 40 seconds with a rapid thermal annealer. The sheet resistance, shape, and composition of the residual materials were investigated with a 4-points probe, a field emission scanning electron microscopy, and an AES depth profiling, respectively. Samples of annealed above $1000^{\circ}C$ showed the agglomeration of residual metals with maze shape and revealed extremely high sheet resistance. The Auger depth profiling showed that the $SiO_2$ substrates had no residual metallic scums after $H_2SO_4$ cleaning while $Si_3N_4$ substrates showed some metallic residuals. Therefore, the $SiO_2$ spacer may be appropriate than $Si_3N_4$ for newly proposed Co/Ni composite salicide process.

• 한국세라믹학회지
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• 제56권2호
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• pp.205-210
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• 2019

Bioactive glass (BG) finds limited use as a bone replacement material owing to its low mechanical properties. In order to solve this problem, the micro-sized 13-93 BG was prepared as a fabric composite with SiC microfibers, and its mechanical properties and biocompatibility were investigated in this study. The tensile strengths of BG-SiC fiber-bundle composites increased in proportion to the number of SiC fibers. In particular, even when only one SiC fiber was substituted, the tensile strength increased by 81% to 1428 MPa. In the early stage of the in-vitro test, a silica-rich layer was formed on the surface of the 13-93 BG fibers. With time, calcium phosphate grew on the silica-rich layer and the BG fibers were delaminated. On the other hand, no products were observed on the SiC fibers for 7 days, therefore, SiC fibers are expected to maintain their strength even after transplantation in the body.

• 한국세라믹학회지
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• 제50권6호
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• pp.378-383
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• 2013

Continuous fiber-reinforced ceramic matrix composites (CFCCs) have a complex distribution of porosity, consisting of interfiber micro pores and interbundle/interply macro pores. Owing to the complex geometry of the pores and fiber architecture, it is difficult to obtain representative microstructural features throughout the specimen volume with conventional, destructive ceramographic approaches. In this study, we introduce X-ray computed microtomography (X-ray ${\mu}CT$) to nondestructively analyze the microstructures of disk shaped and tubular $SiC_f$/SiC composites fabricated by the chemical vapor infiltration (CVI) method. The disk specimen made by stacking plain-woven SiC fabrics exhibited periodic, large fluctuation of porosity in the stacking direction but much less variation of porosity perpendicular to the fabric planes. The X-ray ${\mu}CT$ evaluation of the microstructure was also effectively utilized to improve the fabrication process of the triple-layered tubular SiC composite.