• Title/Summary/Keyword: $C_f/SiC$ Composite

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Microstructure Control of Reaction-Sintered Porous Mullite (반응소결된 다공성 뮬라이트의 미세구조 제어)

  • 조범래;윤상렬;강종봉
    • Composites Research
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    • v.13 no.5
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    • pp.31-36
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    • 2000
  • The effect of several important processing variables was investigated on formation of porous mullite with acicular microstructure. Experimental results demonstrated that microstructure and porosity of porous mullite are depending on concentration of $AlF_3$, holding time at $900^{\circ}C$ and starting material. Acicular mullite was developed by increasing amount of $AlF_3$ and holding time at $900^{\circ}C$. Mullite began to be formed at $1200^{\circ}C$ and the resultant microstructure sintered at this temperature is similar to those at higher temperatures. Porosity increases with increase in amounts of $AlF_3$ and holding time at $900^{\circ}C$ . Therefore, it is found that microstructure of reaction-sintered porous mullite can be controlled by governing the amount of $AlF_3$ and holding time at $900^{\circ}C$.

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Impregnation Behavior of SiCf/SiC Composites Depending on the Polycarbosilane Precursor and Solvent (폴리카보실란의 종류와 용제에 따른 SiCf/SiC복합재의 충진 거동)

  • Kim, Sun-Han;Jung, Yang-Il;Park, Jeong-Yong;Kim, Hyun-Gil;Koo, Yang-Hyun;Hong, Sun-Ig
    • Korean Journal of Materials Research
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    • v.24 no.9
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    • pp.474-480
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    • 2014
  • Process conditions for the impregnation of polycarbosilane preceramic polymer into SiC-based composites were investigated. Two kinds of preceramic polymer (PCP) was impregnated into SiC-fiber fabrics with different solvents of n-hexane and divinylbenzene (DVB). Both microstructural observations and mechanical tests were conducted to evaluate the impregnation. The matrix phases were particulated in the case of hexane solvents. Apparent relative density of the matrix was about 78.8%. The density of matrix was increased to about 96.1-98.8% when the DVB was used; however, brittle fracture was observed during a bending test. The modulus of toughness was less than $0.74J/m^3$. The fabric impregnated with a mixed PCP-dissolved solution showed intermediate characteristics with relative high density of filling (apparent density of ~96.1%) as well as proper bending behavior. The modulus of toughness was increased to about $5.31J/m^3$. The composites developed by changing the precursor and solvent suggested the possibility of fabricating SiCf/SiC composites without a fiber to matrix interphase coating.

Fabrication and Characterization of Cf/SiC Composite with BN Interphase Coated by Wet Chemical Process (습식법으로 제조된 BN 중간층을 가진 Cf/SiC 복합재의 제조 및 물성 평가)

  • Koo, Jun-mo;Kim, Kyung Ho;Han, Yoonsoo
    • Journal of the Korean institute of surface engineering
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    • v.50 no.6
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    • pp.523-530
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    • 2017
  • In this study, we developed the h-BN interphase for ceramic matrix composites (CMCs) through a wet chemical coating method, which has excellent price competitiveness and is a simple process as a departure from the existing high cost chemical vapor deposition method. The optimum condition for nitriding an h-BN interphase using boric acid and urea as precursors were derived, and the h-BN interphase coating through a wet method on a carbon preform of 2.5 D was conducted to apply the optimum conditions to the CMCs. In order to control the coating property via the wet coating method, four parameters were investigated such as dipping time of the specimen in the precursor solution, the ratio of boric acid and urea in the precursor, the concentration of solution where the precursor was dissolved, and the cycle of dipping and dry process. The CMCs was fabricated through polymer impregnation and pyrolysis (PIP) processes and a three-point flexural strength test was conducted to verify the role of the coated h-BN interphase.

Fabrication Process and Impact Characteristic Analysis of Metal Matrix Composite for Electronic Packaging Application (전자패키징용 금속복합재료의 제조공정 해석 및 충격특성평가)

  • 정성욱;정창규;남현욱;한경섭
    • Composites Research
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    • v.15 no.1
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    • pp.32-40
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    • 2002
  • This study developed fabrication process of $SiC_p/Al$ metal matrix composites as electronic packaging materials by squeeze casting method. The $SiC_p$ preform were fabricated in newly designed preform mold using about 0.8 % of inorganic binder(SiO$_2$) and 5 vol.% of $Al_2O_3$fiber. To infiltrate the molten metal into the preform, fabrication condition such as the temperature and the pressure were selected. Applying the fabrication conditions, heat transfer analysis were preformed using finite element method and thus analyzed the temperature distribution and cooling characteristic during the squeeze casting. For the fabricated composites, impact toughness and thermal expansion coefficient were measured. The metal matrix composites developed in this study have 0.2~0.3 J impact toughness, $8~10 ppm/^{\circ}C$ thermal expansion coefficient and $2.9~3.0g/cm^3$density which is appropriate properties for electronic packaging application.

Research on residual stress in SiCf reinforced titanium matrix composites

  • Qu, Haitao;Hou, Hongliang;Zhao, Bing;Lin, Song
    • Steel and Composite Structures
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    • v.17 no.2
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    • pp.173-184
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    • 2014
  • This study aimed to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites. The analytical solution of residual stress field distribution was obtained by using coaxial cylinder model, and the numerical solution was obtained by using finite element model (FEM). Both of the above models were compared and the thermal residual stress was analyzed in the axial, hoop, radial direction. The results indicated that both the two models were feasible to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites, because the deviations between the theoretical calculation results and the test results were less than 8%. In the titanium matrix composites, along with the increment of the SiC fiber volume fraction, the longitudinal property was improved, while the equivalent residual stress was not significantly changed, keeping the intensity around 600 MPa. There was a pronounced reduction of the radial residual stress in the titanium matrix composites when there was carbon coating on the surface of the SiC fiber, because carbon coating could effectively reduce the coefficient of thermal expansion mismatch between the fiber and the titanium matrix, meanwhile, the consumption of carbon coating could protect SiC fibers effectively, so as to ensure the high-performance of the composites. The support of design and optimization of composites was provided though theoretical calculation and analysis of residual stress.

Thermal/Mechanical Properties of Hafnium Carbide Coatings on Carbon-Carbon Composites (탄소-탄소 복합재료의 하프늄 탄화물 코팅재의 열적/기계적 특성)

  • Choi, So-dam;Seo, Hyoung-IL;Lim, Byung-Joo;Sihn, Ihn Cheol;Lee, Jung Min;Park, Jong Kyoo;Lee, Kee Sung
    • Composites Research
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    • v.31 no.5
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    • pp.260-266
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    • 2018
  • This study investigates thermal and mechanical characterization of Hafnium carbide coating on the $C_f-C$ composites. The hafnium carbide coatings by vacuum plasma spray on the C/C-SiC composites are prepared to evaluate oxidation and wear resistance. We perform the thermal durability tests by thermal cycling at $1200^{\circ}C$ for 10cycles in air and investigates the weight change of each cycle. We also evaluate the wear and indentation behavior using tungsten carbide ball indenter as a mechanical evaluation. As a result, the HfC coating is beneficial to reduce of weight loss during thermal cycling test and improve the elastic property of C/C-SiC composite. Especially, the HfC coating improves the wear resistance of C/C-SiC composite.

Finite Element Analysis Through Mechanical Property Test and Elasto-plastic Modeling of 2.5D Cf/SiCm Composite Analysis (2.5D Cf/SiCm 복합재의 기계적 물성 시험과 탄소성 모델링을 통한 유한요소해석)

  • Lee, MinJung;Kim, Yeontae;Lee, YeonGwan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.9
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    • pp.663-670
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    • 2020
  • A study on mechanical property characterization and modeling technique was carried out to approximate the behaviour of structures with 2.5D C/SiC material. Several tensile tests were performed to analyze the behaviour characteristics of the 2.5D C/SiC material and elastic property was characterized by applying a mathematical homogenization and a modified rule of mixture. SiC matrix representing the elasto-plastic behavior approximates as a bilinear function. Then the equivalent yield strength and equivalent plastic stiffness were calculated by minimizing errors in experiment and approximation. RVE(Representative Volume Element)was defined from the fiber and matrix configuration of 2.5D C/SiC and a process of calculating the effective stiffness matrix by applying the modified rule of mixture to RVE was implemented in the ABAQUS User-defined subroutine. Finite element analysis was performed by applying the mechanical properties of fiber and matrix calculated based on the proposed process, and the results were in good agreement with the experimental results.

High Frequency Dielectric Properties of $CaF_2$ filled Glass-Composites ($CaF_2$가 Filler로 첨가된 유리복합체의 고주파 유전특성)

  • Kim, Sun-Young;Lee, Kyoung-Ho;Kim, Sung-Won
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05c
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    • pp.277-281
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    • 2003
  • Effects of $CaF_2$ addition as a filler on the high frequency dielectric properties and sintering of CaO-$Al_2O_3-SiO_2-B_2O_3$(CASB) and ZnO-MgO-$B_2O_3-SiO_2$(ZMBS) glass composites were investigated. The optimal glass composition in the CASB system was 33.0CaO-$17.0Al_2O_3-35.0SiO_2-15.0B_O_3$(in wt%). The corresponding dielectric properties were k=8.1 and $Q{\times}fo$=1,200GHz. The sintering temperature was $800{\mu}m$. In case of 2MBS system, 25.0ZnO-25.0MgO-20.0$B_2O_3-30.0SiO_2$(in wt%) glass showed k=6.8 and $Q{\times}fo$=5,200GHz when it was sintered at $750^{\circ}C$. The maximum amount of $CaF_2$ in the CASB and 2MBS glass system without any detrimental effect on the sintering was 25.0 v/o and 15.0 v/o, respectively. The addition of $CaF_2$ in the glass systems improved the high frequency dielectric properties. In case of CASB+$CaF_2$ composite, k was 7.1 and $Q{\times}fo$ was 2,300GHz. And in case of 2MBS+$CaF_2$ composite, k was 5.9 and $Q{\times}fo$ was 8,100GHz. $CaF_2$ addition also reduced sintering temperature. Effects of $CaF_2$ on the dielectric and sintering properties was analyzed in terms of viscosity and crystallization behavior changes due to the interaction between $CaF_2$ and the glass systems.

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The Properties on Ceramic/glass Composites of SiO2-B2O3-R(CaO, BaO, ZnO, Bi2O3 Borosilicate Glass System for Low Temperature Ceramics (저온 소결 세라믹스용 SiO2-B2O3-R(CaO, BaO, ZnO, Bi2O3 붕규산염계 세라믹/유리 복합체의 특성)

  • Kim, Kwan-Soo;Yoon, Sang-Ok;Shim, Sang-Heung;Park, Jong-Guk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.1
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    • pp.19-24
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    • 2007
  • The effects of $B_2O_3-SiO_2-R(R;CaO,\;BaO,\;ZnO,\;Bi_2O_3)$ borosilicate glass system on the sintering behavior and microwave dielectric properties of ceramic/glass composites were investigated as functions of modifier, glass addition ($30{\sim}50\;vol%$) and sintering temperature ($500{\sim}900^{\circ}C$ for 2 hrs). The addition of 50 and 45 vol% glass ensured successful sintering below $900^{\circ}C$. Sintering characteristics of the composites were well described in terms of modifier. Borosilicate glass enhanced the reaction with $Al_{2}O_{3}$ to form pores, second phases and liquid phases, which was responsible to component of modifier. Dielectric constant (${\varepsilon}_{r},\;Q{\times}f_{o}$) and temperature coefficient of resonant frequency (${\tau}_{f}$) of the composite with 50 and 45 vol% glass contents($B_{2}O_{3}:SiO_{2}:R=25:10:65$) demonstrated A-CaBS(7.8, 2,560 GHz, -81ppm/$^{\circ}C$), A-BaBs(5.8, 3.130 GHz, -64 ppm/$^{\circ}C$), A-ZnBS(5.7, 17,800 GHz, -21 ppm/$^{\circ}C$), A-BiBs(45 vol% glass in total)(8.3, 2,700 GHz, -45 ppm/$^{\circ}C$) which is applicable to substrate requiring an low dielectric properties.

Effects of Fiber Orientations and Hybrid Ratios on Lubricant Tribological Characteristics of $Al_2O_{3f}/SiC_p$ Reinforced MMCs ($Al_2O_{3f}/SiC_p$ 금속복합재료의 섬유방향과 혼합비가 윤활마모특성에 미치는 영향)

  • Wang, Yi-Qi;Song, Jung-Il
    • Composites Research
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    • v.22 no.5
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    • pp.15-23
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    • 2009
  • The lubricant tribological characteristics of $Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) fabricated by squeeze casting method was investigated using a pin-on-disk wear tester. The wear tests of the MMCs were performed according to fiber/particle hybrid ratio in the planar-random (PR) and normal (N) orientations sliding against a counter steel disk at a fixed speed and $25\;kg_f$ loading under different sliding distances and temperatures. The test results showed that the wear behavior of MMCs varied with fiber orientation and hybrid ratio. At room temperature, the lubricant wear behavior of F20P0 unhybrid PR-MMCs was superior to that of N-MMCs while the hybrid composites exhibited the reverse lubricant wear behavior. It was also revealed that the wear resistance of PR-MMCs was superior to that of the N-MMCs due to the joint action of reinforcements and lubricant film between the friction surfaces at an elevated temperature of $100^{\circ}C$ for both fiber only and hybrid cases. In case of $150^{\circ}C$, although the trend of weight loss was similar to that of others, the wear resistance of PR-MMCs was better than that of N-MMCs for hybrid MMCs.