Abstract
Laser-assisted Chemical Vapor Deposition (LCVD) utilizes a focused laser beam to induce a chemical vapor deposition process upon a substrate material. By moving either the substrate or the focal plane of the laser beam LCVD may be used to produce three dimensional structures having characteristic lengths on the order of μm. The physical phenomena associated with LCVD also occur on length scales of μm. For this reason, with the exception of the observation of bulk properties, detailed experimental observations of the fluid flow and heat transfer phenomena associated with the LCVD process do not exist. The LCVD process is characterized by the inter-relating fluid flow, chemical reaction and mass and heat transfer phenomena. In addition, the characteristics of the laser and the deposited material morphology influence the overall process.
The current research effort has developed a mathematical model and employed a numerical technique to characterize the three-dimensional natural convection induced by an incident laser beam around a fiber. This effort has not accounted for the effects of the chemical reactions associated with the LCVD process. The laser irradiance characteristics and the absorption by the fiber material have been incorporated into the energy equation. The velocity and temperature profiles in the boundary layer demonstrate the existence of a small area in which large temperature gradients and a chemical reaction occur. This effort has laid the foundation for an investigation of the one-dimensional diffusion controlled chemical vapor deposition process model. Additionally, it will facilitate the modeling of the three-dimensional homogeneous and heterogeneous reactions in the buoyancy driven flow produced in LCVD fiber formation.
