Chemical Vapor Deposition Modeling for High Temperature Materials
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CHEMICAL VAPOR DEPOSITION MODELING FOR HIGH TEMPERATURE MATERIALS
SULEYNAZ A. GOKOGLU NASA Lewis Research Center, Cleveland, OH 44135
ABSTRACT The formalism for the accurate modeling of chemical vapor deposition (CVD) processes has matured based on the well established principles of transport phenomena and chemical kinetics in The utility and limitations of the gas phase and on surfaces. such models are discussed in practical applications for high temAttention is drawn to the comperature structural materials. Traditional plexities and uncertainties in chemical kinetics. approaches based on only equilibrium thermochemistry and/or transport phenomena are defended as useful tools, within their The role of modeling is validity, for engineering purposes. discussed within the context of establishing the link between CVD It process parameters and material microstructures/ properties. is argued that CVD modeling is an essential part of designing CVD equipment and controlling/optimizing CVD processes for the production and/or coating of high performance structural materials. INTROJUCTION Among the available methods for fabricating materials from the gas phase, chemical vapor deposition (CVD) provides many diverse opportunities for commercial application because it is Indeed, its more economical to develop and easier to scale up. versatility allows CVD to be routinely employed in various areas However, as the interest of materials science and technology. and demand in more sophisticated advanced materials grows to meet today's more stringent performance requirements, it is becoming clearer that the CVD technique should be better exploited. Structural materials have not generally received the same degree of attention in terms of the precision of the CVD process during their fabrication as the electronic and optical materials. However, this is no longer the case. A sufficient understanding of the interactive physicochemical phenomena involved in CVD is required to efficiently Therefore, produce novel materials with superior properties. modeling of such complex systems is now recognized to be an essential and integral part of CVD research. The controlled implementation of the CVD process is an interdiciplinary effort involving many different fields of A comprehensive analysis should science and engineering. naturally include gas phase and surface chemical reaction kinetics, heat and multicomponent mass transport, fluid physics, The simultaneous description of the and thermodynamics (1]. coupled phenomena in multidimensions with multireaction schemes obviously requires highly efficient computational software and The analysis should be fully supported by the hardware [2]. measurement, testing and characterization techniques that are Mat. Res. Soc. Symp. Proc. Vol. 250. 01992 Materials Research Society
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available to specialists in heat transfer, fluids, chemistry and materials science. The modeling of the interactions of such multiparameter systems is indeed a challenge. One has only the directly controllable parameters of
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