The role of the substrate surface area/reactor volume ratio in chemistry and kinetics of chemical vapor deposition

Teubner, Max; Antes, J.; Hu, Zi Jun; Zhang, W.; Hüttinger, Klaus J.

doi:10.1051/jp4:1999810

Cited by 5 publications

(3 citation statements)

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“…However, the doubled surface area in the Felt II does not lead to a doubled bulk density than in the Felt I even during the initial stage of infiltration. Therefore, CVI is not controlled simply by the surface area, but also its [A/V] ratio, because a higher [A/V] ratio leads to a lower surface related deposition rate [15][16][17][18]13]. Bulk densities of the Felt I and II become very similar one another as the infiltration time above 90h.…”

Section: Results and Discussion 31 Densificationmentioning

confidence: 99%

Chemical Vapor Infiltration of Carbon Fiber Felts from Methane: Influence of Surface Area / Volume Ratios

Zhang¹,

Zhu

Hüttinger³

2006

Advanced Inorganic Fibrous Composites V

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Isothermal, isobaric chemical vapor infiltration of carbon fiber felts with fiber volume fractions of 7.1% and 14.2% were investigated at infiltration times from 20 to 120 hours, using a constant temperature of 1095 oC and a methane pressure of 22.5 kPa. Bulk densities and the density profiles as well as porosity at various densification stages were determined. Inside–outside densification was obtained in the most infiltrations, the gradients of densification along the infiltration depth decrease with increasing of residence time and infiltration times. Outside–inside densification occurs only in the felt with the lower fiber volume fraction at final infiltration stage and at longer residence times. Microstructure of the obtained matrix carbon was analyzed with a polarized light microscopy. Abruptly change from low/medium textured carbon to medium/high textured carbon are observed in both of the carbon fiber felts, whereas the thickness of the first lower textured layer is about 14 micros in the felt with a fiber volume fraction of 7.1%, whereas it is only 2 micros in the felt with a fiber volume fraction of 14.2%, which is caused by an increasing of initial surface area / volume ratio, [A/V], from 33 to 71 mm-1. Results are completely in agreement with the previous simulations studies on the influence of [A/V] ratios.

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Section: Results and Discussion 31 Densificationmentioning

confidence: 99%

Chemical Vapor Infiltration of Carbon Fiber Felts from Methane: Influence of Surface Area / Volume Ratios

Zhang¹,

Zhu

Hüttinger³

2006

Advanced Inorganic Fibrous Composites V

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“…Because of the significant amount of chemical reactions taking place during the deposition process, it is usually assumed to decrease the reactions number by the so-called simplified (reduced) reaction scheme. Here we use a simplified reaction scheme following the proposal of Becker and Hüttinger [44,54,55]. The proposal is based on the separation of chemical reactions in species classes established on the basis of similarities between the species.…”

Section: Chemical Reactions Schemementioning

confidence: 99%

Diffuse interface method for simulation of the chemical vapor deposition of pyrolytic carbon: Aspects of the mathematical formulation

Dimitrov

Ekhlakov

Langhoff

2008

Commun. Numer. Meth. Engng.

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SUMMARYThe present work is inspired by Anderson et al. (Phys. D Nonlinear Phenom. 2000; 135(1-2):175-194) and Noll (http://www.math.cmu.edu/wn0g/noll) and falls in the conceptual line of the Ginzburg-Landau class of first-order phase-transition models based on the concept of phase-field parameter. Trying to keep the exposition as much general as possible, we develop below a thermodynamically consistent rationalization of the physical process of (anisotropic) deposition of pyrolytic carbon from a gas phase. The derivation line we follow is well established in the field of the modern continuum physics. From the covariance of the first principle of thermodynamics, the second Newton's law and the Liouville's theorem with respect to the one-dimensional Lie groups of transformations, the balance laws for the temperature, linear momentum and density are formulated. This system of partial differential equations is comprehended further by the constitutive laws for the phase field, the stress, and the heat and entropy fluxes obtained in a form consistent with the Clausius-Duhem understanding of the second law. The result referred to as a local, strongly coupled initial boundary value problem of chemical vapor deposition (IBVP-CVD) constitutes the general mathematical description of the CVD process. The weak form of isotropic IBVP-CVD is then derived and discretized by means of the discontinuous Galerkin method. At the end of the paper, we also derive the weak formulations for the local lifting operators that provide the stabilization mechanism for the discontinuous Galerkin discretization scheme.

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“…, 6) are functions of the temperature. We define further the deposition rate constants through the gas reaction constants [39,40] …”

Section: Reaction Kineticsmentioning

confidence: 99%

Phase‐field model for deposition of pyrolytic carbon

Ekhlakov

Dimitrov

Langhoff

et al. 2008

Commun. Numer. Meth. Engng.

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SUMMARYA diffuse interface model for the determination of the evolution of the deposited substrate surface during isobaric, isothermal chemical vapour infiltration (CVI) of pyrolytic carbon is proposed. A continuous scalar phase-field parameter is introduced to label explicitly the solid and the gas phases within the system. Following the conceptual line of Ginzburg-Landau theory, we formulate the initial boundary value problem of CVI. In variance with the traditional formulations, we account for the different intensities of homogeneous and heterogeneous chemical reactions during CVI by introducing a scalar-valued intensity parameter that depends only on the phase-field. The various homogeneous and heterogeneous reaction processes during CVI are described in terms of a reduced chemical reaction scheme. Finally, we discuss the application of the developed methodology for numerical simulation of a simplified two-dimensional model problem. Using a finite element method, we obtain numerical approximations for the concentration profiles along the direction of infiltration.

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The role of the substrate surface area/reactor volume ratio in chemistry and kinetics of chemical vapor deposition

Cited by 5 publications

References 0 publications

Chemical Vapor Infiltration of Carbon Fiber Felts from Methane: Influence of Surface Area / Volume Ratios

Chemical Vapor Infiltration of Carbon Fiber Felts from Methane: Influence of Surface Area / Volume Ratios

Diffuse interface method for simulation of the chemical vapor deposition of pyrolytic carbon: Aspects of the mathematical formulation

Phase‐field model for deposition of pyrolytic carbon

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