Transport Processes in Chemical Vapor Deposition of Functionally Graded Materials: Fundamental Understanding through Combined Experiments and High-Fidelity Mathematical Modeling

本研究的目的是通过实验和计算相结合的方法，对功能梯度化学气相沉积(CVD)过程中的物理和化学输运过程有一个基本的了解。功能梯度材料(FGM)可以被定义为材料的组成从一个极端到另一个极端逐渐变化的材料。功能梯度材料可以成功地用于连接两种互不相连的材料，如金属和陶瓷，或在衬底上提供涂层，从而提供逐渐变化的热膨胀系数。CVD包括在加热到可以发生化学反应的温度的衬底上逐渐沉积一种材料，从而形成一层薄薄的沉积层。一个典型的CVD过程涉及到流量、温度、物质浓度和反应器几何形状之间的复杂相互作用。准确地了解各种流动变量之间的相互作用对于获得最佳的操作参数及其变化方式是非常重要的。实验中解决的基本问题是载气输送的化学物质的瞬时平面分布以及衬底表面附近的温度。计算研究的目标将是建立一个关于梯度沉积过程中发生的瞬变流动、传热和化学反应的数学模型。

The objective of this research is to gain a fundamental understanding of the physical and chemical transport processes in the chemical vapor deposition (CVD) of functionally graded methods, through a combined experimental and computational investigation. A functionally graded material (FGM) may be defined as one in which the composition of the material varies gradually from one extreme to another. Functionally graded materials can successfully be used to join two disjoint materials such as metals and ceramics, or provide coatings on substrates in such a way as to provide a gradual variation of the thermal expansion coefficient. CVD involves the gradual deposition of a material on a substrate heated to a temperature where chemical reactions can take place, thus forming a thin layer of deposit. A typical CVD process involves complex interactions between flow, temperature, species concentrations, and reactor geometry. Understanding the precise interactions between the various flow variables is very essential to obtaining the optimum set of operating parameters, and their manner of variation.The fundamental issues addressed in the experiments will be the transient planar distributions of the chemical species transported by the carrier gas, and of temperature near the surface of the substrate. The objective of the computational study will be to develop a mathematical model of the transient flow, heat transfer and chemical reactions that occur during the graded deposition process.