• Title, Summary, Keyword: Chemical vapor infiltration

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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.

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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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.

Fabrication of SiCf/SiC Composite by Chemical Vapor Infiltration (화학기상침착법에 의한 SiCf/SiC 복합체의 제조)

  • Park, Ji Yeon;Kim, Daejong;Kim, Weon-Ju
    • Composites Research
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    • v.30 no.2
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    • pp.108-115
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    • 2017
  • Among several fabrication processes of $SiC_f/SiC$ composites, the chemical vapor infiltration (CVI) process has attractive advantages in manufacturing complex net-or near-net-shape components at relatively low temperatures, easily controlling the microstructure of the matrix and obtaining the highest SiC purity level. However, it has disadvantages in that the ratio of residual pores in matrix is higher than other processes and processing time is relatively long. To reduce the residual porosity, the whisker-growing-assisted CVI process, which is composed of whisker growth and matrix filling steps has been developed. The whiskers grown before matrix filling may serve to divide the large natural pores between the fibers or bundles so that the matrix can be effectively filled into the finely divided pores. In this paper, the fundamentals of the CVI process for preparation of $SiC_f/SiC$ composites and some experimental results prepared by CVI and whisker-growing-assisted CVI processes are briefly introduced.

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.

High textured carbon from chemical vapor infiltration with ethanol precursor and its rate of pyrolytic carbon deposition

  • Choi, Si Won;Joo, Kyung Do;Chung, Gui-Yung
    • The Korean Journal of Chemical Engineering
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    • v.34 no.10
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    • pp.2764-2772
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    • 2017
  • Preparation of C/C composites with ethanol precursor was studied and the role of ethanol in obtaining high textured (HT) carbon was confirmed. HT carbon was obtained more with ethanol precursor than with propane precursor as reported by Ren et al. The pyrolytic carbon deposition rate constant from ethanol precursor, which has never been reported before in any other research, was obtained. It was confirmed that a proper mixture precursor of ethanol and propane could be used in the process of temperature gradient chemical vapor infiltration (TG-CVI) on behalf of the uniform deposition throughout the preform and the deposition with more HT carbon,. The pyrolytic carbon deposition rate constant for the CVI with propane precursor obtained in this research was 2.2-times greater than that reported by Vaidyaraman.

Numerical Simulation of Diffusion and Flow in Fabrication of Carbon/Carbon Composite Using Chemical Vapor Infiltration (다단계 화학반응과 밀도화 모델을 이용한 탄소/탄소 복합재 화학기상침투 공정의 확산 및 유동 수치해석)

  • Kim, Hye-gyu;Ji, Wooseok;Jo, Namchun;Park, Jonggyu
    • Composites Research
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    • v.32 no.1
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    • pp.56-64
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    • 2019
  • In this paper, a model is developed to simulate carbon/carbon composite fabrication using chemical vapor infiltration, considering density and porosity change in the preform and multi-step hydrocarbons reactions. The model considers the preform as a porous medium whose diffusion and flow properties changes due to the porosity. To verify the theoretical model, two numerical analyses were performed for the case that the flow inside the preform is zero and the case that the flow inside the preform is calculated by fluid mechanics. The numerical results showed good agreement with the experimental data.

Numerical Study on CVI Process for SiC-Matrix Composite Formation (SiC 복합체 제조를 위한 화학기상침착공정에 대한 수치해석 연구)

  • Bae, Sung Woo;Im, Dongwon;Im, Ik-Tae
    • Journal of the Semiconductor & Display Technology
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    • v.14 no.2
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    • pp.61-65
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    • 2015
  • SiC composite materials are usually used to very high temperature condition such as thermal protection system materials at space vehicles, combustion chambers or engine nozzles because they have high specific strength and good thermal properties at high temperature. One of the most widely used fabrication methods of SiC composites is the chemical vapor infiltration (CVI) process. During the process, chemical gases including Si are introduced into porous preform which is made by carbon fibers for infiltration. Since the processes take a very long time, it is important to reduce the process time in designing the reactors and processes. In this study, both the gas flow and heat transfer in the reactors during the processes are analyzed using a computational fluid dynamics method in order to design reactors and processes for uniform, high quality SiC composites. Effects of flow rate and heater temperature as process parameters to the infiltration process were examined.

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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Effect of Processing Parameters on the Densification of Carbon/Carbon Composite by Isothermal Low-Pressure Chemical Vapor Infiltration (등온 저압화학기상침투법에 의한 탄소/탄소 복합재료의 치밀화에 대한 제조공정변수의 영향)

  • Park, H.D.;Ahn, C.W.;Cho, K.;Yoon, B.Y.;Kim, K.S.
    • Korean Journal of Materials Research
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    • v.4 no.3
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    • pp.259-267
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    • 1994
  • The effect of processing parameters, temperature, gas concentration, gas flow rate and pressure, were studied on the densification of carbon/carbon composites using a Robust design method in isothermal low-pressure chemical vapor infiltration with a gas system of $C_3H_8-N_2$ After one time of isothermal low-pressure chemical vapor infiltrat.ion, the bulk density of carbon/carbon composites in creased up to 1-9% and apparent porosity of the composites decreased down to 20-50%. ANOVA analysis of the experiment.al data revealed that the important parameters of isothermal lowpressure chemical vapor infiltration were temperature, gas concentration and gas flnw rate. 'There was almost no ~ f f e c t on densification by pressure and interaction between each parameters. In t, he present experimental conditions, the highest bulk density was obtained at $1100^{\circ}C$ temperature, 100% $C_3H_8$, concentration, 100 SCCM flow rate and 5 torr pressure.

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