Study On The Performance And Technology Of CVDRe

In this dissertation, the preparation of Re coatings by CVD was investigated. The process, structure and the components were studied. The system of CVD was designed, assembled and debugged. Substrate was heated in a cold-wall CVD reactor in order to heat it more centrally. The conclusion of debug indicate the system can meets the requirement of CVD no matter in stability or tightness.Through calculation of △G, △H and K_P of the reaction in the procedure of CVD, the feasible technological parameter of CVD was gain. The technological procedure of CVD of Re coating was studied, it is found that the deposition rate increased with the rise of the temperature of the substrate. The relationship between the deposition rate and the substrate temperature accorded with Arrhenius form. Through the analyse of the relation between the flow rate of chlorine and the deposition rate, it is found that the deposition rate reduced with the rise of flow rate of chlorine. Finally the feasible technological parameters are concluded that the temperature is 1400 -1500K, the temperature of chloridate is 900 K -1000K and the flow rate of chlorine is 50-70 ml/min.The crystal phase of the coating was analysed by XRD. It is found the coating is pure Re crystal. Through the analys of the relation between the technological parameter and pattern of the coatings, it is found lower deposition temperature is favorable for small size crystal, the great flow rate of chlorine is favorable for gain of more smooth surface, and higher temperature of chloridate is beneficial for dendritic crystal.The hardness and elastic modulus of CVDRe were determed by micron/nanoindentation and microhardness instrument. It was found that the microhardness of CVDRe is low, and microhard-ness and elastic modulus have an inverse ration with the size of crystal of CVDRe. At the same time the value of microhardness and elastic modulus of CVDRe both have a large-distribution. Re coating was deposited both in graphite and C_f/SiC also. The analysis of the interface of Re-graphite and Re- C_f/SiC showed that CVDRe bond well with graphite and C_f/SiC.Oxidation behavior of CVDRe in air and at 400-700℃ was studied, it is found that the Oxidation will not occur when the temperature below 400℃, the oxidation rate is low and the loss of wight by oxidation have a linear ration with oxidative time when the temperature is 500℃. When the temperature is 600℃, the Oxidation behavior of CVDRe follow the law of Wagner.