• Title/Summary/Keyword: Chemical Vapor Infiltration (CVI)

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Studies on the Mathematical Modelling of the Pulse-CVI for the Infiltration of Siliconcarbide from Methyltrichlorosilane (메틸삼염화규소로부터 탄화규소 침착의 Pulse-CVI에 대한 수치모사 연구)

  • Kim, In-Goo;Kim, Min-Ki;Chung, Gui-Yung
    • Composites Research
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    • v.18 no.5
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    • pp.27-33
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    • 2005
  • In this research, the mathematical modelling of the pulse-CVI (Chemical Vapor Infiltration) for the preparation of siliconcarbide/carbon composite. Each pulse consists with the gas injection time, the reaction time and the evacuation time. Effects of the reaction time and the evacuation time were studied. Additionally, the effects of the reactant concentration and the pressure were observed. The benefits of the pulse-CVI such as the uniform infiltration of siliconcarbide into the carbon preform and the short reaction time were certified.

Nicalon-Fiber-Reinfored SiC Composites Via Infiltration (Infiltration 공정으로 제조한 Nicalon 섬유강화 SiC 복합재료)

  • 김민수;김영욱;한경섭;박정현
    • Journal of the Korean Ceramic Society
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    • v.30 no.12
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    • pp.993-998
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    • 1993
  • Nicalon-fiber-reinforced SiC composites were fabricated via polymer solution infiltration/chemical vapor infiltration (PSI/CVI) and CVI. Specifically, data were taken and compared for flexural strength, fracture toughness, and processing time. The two process resulted in comparable mechanical properties, and PSI/CVI process resulted in significantly reduced infiltration time.

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Film Boiling Chemical Vapor Infiltration of C/C Composites: Influence of Mass and Thermal Transfers

  • Delhaes, P.;Trinquecoste, M.;Derre, A.;Rovillain, D.;David, P.
    • Carbon letters
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    • v.4 no.4
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    • pp.163-167
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    • 2003
  • The "Film boiling" Chemical Vapor Infiltration (CVI) process is a rapid densification one developed in particular for the elaboration of carbon/carbon composite materials. In order to optimize this new thermal gradient process, we have carried out several studies, on one hand, about the nature of the complex chemical reactions in a confined medium, and on the other hand, relative to the role of heat and mass transfers inside the preform. We show in this study that the introduction of a permeable sheath around the preform leads to hybrid liquid/gas CVI process which presents the advantages of very high densification rates associated with a moderate input energy.

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Densification of Carbon/Carbon Composites by Pulse CVI with and without Residence (펄스화학기상침트법에 의한 탄소/탄소 복합재료의 치밀화에 있어서 가스유지시간 유무의 영향)

  • 이용근;류호진;박희동
    • Journal of the Korean Ceramic Society
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    • v.33 no.8
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    • pp.935-941
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    • 1996
  • Two-dimensional carbon/carbon preforms made of PAN-based carbon yarn and phenolic resin were densified with pyrolysis of propane by pulse chemical vapor infiltration where repeated the cycle of gas introduction residence and evacuation. Maximim density increment was 14% when infiltration temperature and time were 100$0^{\circ}C$ and 21.25 hrs respectively. The distribution of deposits of pyrocarbon by this process has been occurred uniformly in the bottom middle and top of carbon/carbon composite preform Pulse CVI with residence is most effective in increasing density and shortening infiltration time among isothermal CVI and pulse CVI with and without residence.

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Mechanical Properties of Cf/SiC Composite Using a Combined Process of Chemical Vapor Infiltration and Precursor Infiltration Pyrolysis

  • Kim, Kyung-Mi;Hahn, Yoonsoo;Lee, Sung-Min;Choi, Kyoon;Lee, Jong-Heun
    • Journal of the Korean Ceramic Society
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    • v.55 no.4
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    • pp.392-399
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    • 2018
  • $C_f/SiC$ composites were prepared via a process combining chemical vapor infiltration (CVI) and precursor infiltration pyrolysis (PIP), wherein silicon carbide matrices were infiltrated into 2.5D carbon preforms. The obtained composites exhibited porosities of 20 vol % and achieved strengths of 244 MPa in air at room temperature and 423 MPa at $1300^{\circ}C$ under an Ar atmosphere. Carbon fiber pull-out was rarely observed in the fractured surfaces, although intermediate layers of pyrolytic carbon of 150 nm thickness were deposited between the fiber and matrix. Fatigue fracture was observed after 1380 cycles under 45 MPa stress at $1000^{\circ}C$. The fractured samples were analyzed by transmission electron microscopy to observe the distributed phases.

Numerical study on heat transfer and densification for SiC composites during thermal gradient chemical vapour infiltration process

  • Ramadan, Zaher;Im, Ik-Tae
    • Carbon letters
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    • v.25
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    • pp.25-32
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    • 2018
  • In this study, a thermal-gradient chemical vapor infiltration (TG-CVI) process was numerically studied in order to enhance the deposition uniformity within the preform. The computational fluid dynamics technique was used to solve the governing equations for heat transfer and gas flow during the TG-CVI process for two- and three-dimensional (2-D and 3-D) models. The temperature profiles in the 2-D and 3-D models showed good agreement with each other and with the experimental results. The densification process was investigated in a 2-D axisymmetric model. Computation results showed the distribution of the SiC deposition rate within the preform. The results also showed that using two-zone heater gave better deposition uniformity.

Fracture Behaviors of SiCf/SiC Composites Prepared by Hybrid Processes of CVI and PIP (화학침착법과 고분자함침 열분해법의 복합공정으로 제조한 SiCf/SiC 복합체의 제조 공정에 따른 파괴거동)

  • Park, Ji Yeon;Han, Jangwon;Kim, Daejong;Kim, Weon-Ju;Lee, Sea Hoon
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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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 $11.2{\sim}13.5MPa{\cdot}m^{1/2}$.

Influence of Winding Patterns and Infiltration Parameters on Chemical Vapor Infiltration Behaviors of SiCf/SiC Composites (SiCf/SiC 복합체의 화학기상침착 거동에 미치는 권선 구조와 침착 변수의 영향)

  • Kim, Daejong;Ko, Myoungjin;Lee, Hyeon-Geun;Park, Ji Yeon;Kim, Weon-Ju
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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    • pp.453-458
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    • 2014
  • SiC and its composites have been considered for use as nuclear fuel cladding materials of pressurized light water reactors. In this study, a $SiC_f$/SiC composite as a constituent layer of SiC triplex fuel cladding was fabricated using a chemical vapor infiltration (CVI) process in which tubular SiC fiber preforms were prepared using a filament winding method. To enhance the matrix density of the composite layer, winding patterns, deposition temperature, and gas input ratio were controlled. Fiber arrangement and porosity were the main parameters influencing densification behaviors. Final density of the composites decreased as the SiC fiber volume fraction increased. The CVI process was optimized to densify the tubular preforms with high fiber volume fraction at a high $H_2$/MTS ratio of 20 at $1000^{\circ}C$; in this process, surface canning of the composites was effectively retarded.

Fracture Behaviors and Mechanical Properties of SiCf/SiC Composites Prepared by the Whisker Growing Assisted CVI Process (Whisker Growing Assisted 화학침착 공정으로 제조된 SiCf/SiC 복합체의 파괴거동과 기계강도 평가)

  • Kang, Seok-Min;Kim, Weon-Ju;Yoon, Soon-Gil;Park, Ji-Yeon
    • Journal of the Korean Ceramic Society
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    • v.46 no.5
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    • pp.484-487
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    • 2009
  • $SiC_f$/SiC composites with whiskers and pyrolytic carbon (PyC) coated whiskers in the matrix were fabricated for enhancement of the fracture behaviors by the whisker growing assisted chemical vapor infiltration (WA-CVI) process, respectively. $SiC_f$/SiC composites were also prepared by the conventional CVI process as reference material. The mechanical properties and fracture behaviors were analyzed by comparison of the two types of composites prepared by WA-CVI and conventional CVI. The densities of $SiC_f$/SiC composites were in the range of $2.6{\sim}2.65g/cm^3$. The flexural strengths of composite with whiskers and with those coated by PyC were 650 MPa and 600 MPa, respectively. The tensile strength of composites with whiskers was ${\sim}285$ MPa.

Studies on Effects of Deposition Parameters in Manufacturing of C/Sic composites by Pulse-CVI (C/SiC 복합재료 제조시 Pulse-CVI에서 증착변수의 영향 연구)

  • 김용탁;김영준;정귀영
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2001.10a
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    • pp.141-143
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    • 2001
  • Ceramic fiber-reinforced composites have good mechanical properties in hardness and durability. In this study, we studied the formation of SiC/C composites from methyltrichlorosilane and hydrogen by the Pulse-chemical vapor infiltration(PCVI) to deposit silicon carbide around the changes of the amount of deposit. SiC/C composites formed at $950^{\circ}C$, 20torr, Pulse-times (5s/60s). SEM of the cross sectional area of semple showed deposited silicon carbide around fibers.

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