ANALYSIS OF TRANSPORT PHENOMENA IN THE COATING OF FIBERS BY CVD

Abstract
Inorganic coated fibers produced by chemical vapor deposition find several technological applications. In this CVD process, a fiber core is mounted in a reactor between two electrodes. Reactive gases flow over the substrate and react near or on the fiber surface to form the desired coating. Experience has shown that quality deposition can only be obtained over a small range of the governing parameters : these parameters are, however, difficult to control. In the present study, a mathematical model is developed for the reactor configuration under consideration. The different mass and energy transport mechanism are compared and their influence on the reactor performance is evaluated for horizontal reactor arrangements. Numerical results, showing sharp temperature and concentration gradient close to the fiber surface, suggest that heat and mass transfer in this region are controlled by conduction and diffusion mechanisms. In the bulk region, heat and mass transfer via the convection and conduction/diffusion mechanisms can be of equal importance. Numerical results show how bulk properties are affected by both transversal and longitudinal rolls.