The key parameters in the preparation process of CVD silicon carbide coating are to control and optimize various parameters that affect the quality and performance of the coating, in order to ensure that the coating has the required characteristics and properties. The following are some key parameters that affect the quality and performance of CVD silicon carbide coatings.

1. Gas composition of reactants: The quality and performance of coatings are affected by the gas composition of reactants. In the preparation process of CVD silicon carbide coatings, one or more organic silicon and carbon sources are usually used as reactants. The selection and proportion of these reactants will directly affect the characteristics of the generated silicon carbide coating. Appropriate reactant gas composition can obtain high-purity, dense, and uniform coatings.

2. reactant gas flow rate: The reactant gas flow rate is an important parameter for controlling the supply rate of reactants. Appropriate reactant gas flow rate is crucial for ensuring the uniformity and stability of the reaction. Low flow rates may result in slow reaction rates and uneven coating formation. Excessive flow may lead to unstable reaction processes.

3. Reaction temperature: The reaction temperature has a significant impact on the growth rate, grain morphology, and grain boundary structure of CVD silicon carbide coatings. Reasonable selection and control of reaction temperature can achieve the desired coating characteristics. Too low a temperature may result in a slow reaction rate, making it difficult to form a dense coating. Excessive temperature may cause structural changes in the silicon carbide coating, reducing its performance.

4. Reaction pressure: Reaction pressure is achieved by controlling the gas pressure inside the reaction chamber. Appropriate reaction pressure can effectively control the diffusion rate of reactant gases in the reaction chamber, thereby affecting the uniformity and density of the coating. Low reaction pressure may result in uneven diffusion of reactants and the formation of non-uniform coatings. Excessive reaction pressure may lead to excessive compression, physical deformation, and stress concentration.

5. Substrate surface treatment: The treatment of the substrate surface plays an important role in the adhesion and density of CVD silicon carbide coatings. Chemical methods, physical methods, or a combination thereof are usually used to clean, remove oxygen, impurities, and form active surfaces on the substrate surface for pretreatment, in order to improve coating quality. Appropriate surface treatment methods and conditions can maximize the bonding strength and adhesion between coatings and substrates.

6. Reaction time: Reaction time refers to the time the reactants stay in the reaction chamber. An appropriate reaction time can allow the reactants to fully react, reach their desired state, and form the desired coating structure. A too short reaction time may lead to incomplete reaction, resulting in uneven or low-quality coatings. Excessive reaction time may result in non ideal reaction products.

In summary, the key parameters in the preparation process of CVD silicon carbide coatings include reactant gas composition, reactant gas flow rate, reaction temperature, reaction pressure, substrate surface treatment, and reaction time. By selecting and controlling these parameters reasonably, silicon carbide coatings with high quality and required performance can be obtained.