Committee Chair

Barisik, Murat

Committee Member

Sreenivas, Kidambi; Ranjan, Reetesh

Department

Dept. of Mechanical Engineering

College

College of Engineering and Computer Science

Publisher

University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)

Abstract

Chemical Vapor Infiltration (CVI) is a key method for fabricating silicon carbide (SiC) matrix composites. Gas-phase precursors flow into a porous fiber, react, and deposit to form the ceramic matrix. Deposition quality and rate are strongly influenced by surface reactions, depending on temperature, gas flow, and reactor pressure. This study applies a computational model to better understand rarefied gas behavior and surface chemistry during CVI. We use the Direct Simulation Monte Carlo method to simulate gas flow and chemical reactions around the fibers. Simulations span Knudsen numbers 0.001–20 and temperatures 1000–1600 K (near‑continuum to free‑molecular). As rarefaction increases, deposition rate decreases, yet temperature remains significant. In forced‑flow CVI, deposition becomes uneven: the fiber's inlet side grows more, the opposite side less. To improve gas‑phase chemistry accuracy, we adapt a Quantum‑Kinetic model for methyltrichlorosilane and chlorine reactions. Overall, it clarifies how rarefied gas dynamics and activation energy control CVI.

Acknowledgments

I am deeply grateful to my advisor, Dr. Barisik, for bringing this important topic to my attention. His clear vision, insightful feedback, and steady encouragement have shaped both this study and my research approach. I also thank Dr. Ranjan for his guidance and detailed suggestions throughout the development of my thesis. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC0024510 I wish to express my sincere appreciation to my sister Melisa and Nicholas their support and encouragement were invaluable throughout this work. I am also deeply thankful to all my friends, whose steady support I felt at every stage of this journey. Lastly, I am grateful to my family for their endless care, love, and encouragement. They also supported me throughout my educational life.

Degree

M. S.; A thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Master of Science.

Date

8-2025

Subject

Chemical vapor deposition; Monte Carlo method; Rarefied gas dynamics; Silicon carbide--Thermal properties; Surface chemistry--Mathematical models

Keyword

Chemical Vapor Infiltration (CVI); Direct Simulation Monte Carlo (DSMC); Rarefied Gas Dynamics; Surface Reactions; Silicon Carbide (SiC) Composites

Document Type

Masters theses

DCMI Type

Text

Extent

xi, 56 leaves

Language

English

Rights

http://rightsstatements.org/vocab/InC/1.0/

License

http://creativecommons.org/licenses/by-nc/4.0/

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