Analysis of interface evolution and pattern formation during CVD

Thiart, Jacob J.; Hlaváček, Vladimír

doi:10.1002/aic.690410810

Cited by 10 publications

(4 citation statements)

References 29 publications

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“…This causes the peaks to grow faster than the valleys and a needlelike formation results. This phenomenon, known as self-shadowing, has also been considered by 19 through the inclusion of relevant view factors for the impinging concentration flux over the surface, and by [20][21][22] for coating onto flat surfaces.…”

Section: Numerical Simulation Resultsmentioning

confidence: 99%

Modeling and simulation of coating growth on nanofibers

Wilder

Clemons

Kreider

et al. 2009

Journal of Applied Physics

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This work presents modeling and simulation results of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort that motivates the modeling, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor, nanofiber, and atomic levels to form a comprehensive model. Numerical simulations that link the concentration field with the evolution of the coating free surface predict that as the Damköhler number is increased the coating morphology changes from a wavy to a nodular to a dendritic needle-type form as observed experimentally.

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Section: Numerical Simulation Resultsmentioning

confidence: 99%

Modeling and simulation of coating growth on nanofibers

Wilder

Clemons

Kreider

et al. 2009

Journal of Applied Physics

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“…Especially at a high reaction rate, pore closure can occur even when no closure is expected, because of two-dimensional diffusion effects. 19 At a corner or on a convex surface of the pore wall, it is likely that deposits grow without conformal coverage and choke the pore. This manner of infiltration accelerates pore closure, and the closure time is earlier than that expected by the model calculation.…”

Section: Discussionmentioning

confidence: 99%

Modeling of Chemical Vapor Infiltration Rate Considering a Pore Size Distribution

Yoshikawa¹

2002

Journal of the American Ceramic Society

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To analyze chemical vapor infiltration (CVI) rates, a simulation model (PC model) was proposed, which is capable of considering difficulties of densification in the internal regions of porous bodies and the pore closure phenomena. In the model, a fictitious tapered pore is constructed based on the pore size distribution of the preform body, and variation of the pore shape during the process is calculated. For simulation study, fictitious tapered pores were constructed using different pore size distribution functions of Gaussian, ␦-function, and flat distribution, and their shapes and characteristics were compared. In the case of the Gaussian flat distribution (large dispersion), the fraction of fine pores was large and these pores became closed near their mouths. Reconversion of temporal fictitious pore shape into the pore distribution function was attempted and the PC model was successfully applied to monitor variations in the pore size distributions during the CVI process.

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“…This type of approximation has been used for deposition onto planar surfaces. 12 This assumption is valid for all D k F for small coating thickness, and is always relevant for small D k F due to the nearly constant value of the coating profile in such highly diffusive systems. We use this approximation to simplify the numerical simulations in Sec.…”

Section: B Solutionsmentioning

confidence: 99%

“…Note that k F and C * are calculated by the model, ␤ is the molar volume for aluminum, and D , ⌫ , and s D s are estimated from the literature. 12 Concentration at the front. The concentration at the front is approximated by ͑17͒ evaluated at r = F. Figure 12 shows how this concentration depends on the radius of the coating ͑recall that r = 1 is half the distance between fibers͒.…”

Section: Level Set Simulations Of the Coating Surfacementioning

confidence: 99%

Multiscale modeling, simulations, and experiments of coating growth on nanofibers. Part II. Deposition

Buldum

Clemons

Dill

et al. 2005

Journal of Applied Physics

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This work is Part II of an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin-film materials using plasma-enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with aluminum materials under different operating conditions to observe changes in the coating morphology. This procedure begins with the sputtering of the coating material from a target. Part I ͓J. Appl. Phys. 98, 044303 ͑2005͔͒ focused on the sputtering aspect and transport of the sputtered material through the reactor. That reactor level model determines the concentration field of the coating material. This field serves as input into the present species transport and deposition model for the region surrounding an individual nanofiber. The interrelationships among processing factors for the transport and deposition are investigated here from a detailed modeling approach that includes the salient physical and chemical phenomena. Solution strategies that couple continuum and atomistic models are used. At the continuum scale, transport dynamics near the nanofiber are described. At the atomic level, molecular dynamics ͑MD͒ simulations are used to study the deposition and sputtering mechanisms at the coating surface. Ion kinetic energies and fluxes are passed from the continuum sheath model to the MD simulations. These simulations calculate sputtering and sticking probabilities that in turn are used to calculate parameters for the continuum transport model. The continuum transport model leads to the definition of an evolution equation for the coating-free surface. This equation is solved using boundary perturbation and level set methods to determine the coating morphology as a function of operating conditions.

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Analysis of interface evolution and pattern formation during CVD

Abstract: Morphological aspects of the evolution of a gas

Cited by 10 publications

References 29 publications

Modeling and simulation of coating growth on nanofibers

Modeling and simulation of coating growth on nanofibers

Modeling of Chemical Vapor Infiltration Rate Considering a Pore Size Distribution

Multiscale modeling, simulations, and experiments of coating growth on nanofibers. Part II. Deposition

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