Study On MOCVD Process Of Preparing Anti-oxidation Ir Coatings

In this thesis,Ir coatings deposited on the C_f/SiC composites and Mo by MOCVD process were investigated to enhance their oxidation resistance.The process,components,structure and properties of Ir coatings were studied.The C_f/SiC composites were tested in the simulated process of MOCVD,there is not apparent effect on its mechanical property,It can be treated by the process of MOCVD in the presence of O₂.The deposition experiment of Cu(acac)₂ on SiC ceramic plate to obtain an expected process -ing parameters indicates the cold-wall MOCVD reactor designed are also applicable for non-metal materials.The sublimed experiment of Cu(acac)₂ indicates that its sublimed speed rate is constant in the stationary temperature environment,sublimed speed rate can be controlled by altering speed of movement.The sublimed speed rate can be indicated by the variation of the system pressure.It is found that the growth rate increase as the rising of the substrate temperature during the preparation of Ir coatings.In the presence of O₂,the temperature of deposition can reduce dramatically and the yield can increase notably,but Ir coatings deposited using a high O₂ partial pressure exhibit a low purity.The particles of Ir coatings easily reunited as the rising of the concentration.The mean growth rate have a close relationship with the temperature of deposition and the concentration of reactant,the more concentration is,the bigger the speed will be.The net yield of Ir deposited on annular speciman is about 30%,and its gross yield is about 70%;the experiment of depositing on Mo substrate shows that the yield will be increased as temperature grows,but the binding strength will go down.The analysis of component indicates that the purity of the surface of Ir coating is lower than the purity of the inside by energy spectrometer,and carbon and oxygen are contained in the film. The purity of film can be promoted by H₂ in high temperature.The deposition effectiveness can be measured by its airtightness,Ir coatings can enhance airtightness of C_f/SiC composites effectively.The ablation of oxyacetylene flame shows that Ir coatings play an important role in oxidation resistance,especially after the process of H₂.