There are two ways to improve the Different Size Graphite Electrode resistance of carbon / carbon: adding antioxidants to reduce the oxidation rate or blocking oxygen on the surface coating of the parts. At present, the only structural materials that can work normally at a high temperature of 1600 ° C to 2000 ° C are carbon / carbon composite materials, which have the following advantages when used in the hot end parts of aeroengines: (1) It can still maintain strength without reducing above 1600 ° C; )
Reduce the weight of the engine and increase the thrust-to-weight ratio; (3) Reduce additional cooling, increase the operating temperature and improve the thermal efficiency of the engine. Once the cross section of the fiber is exposed, the fiber is rapidly ablated from the core and silicon carbide is left Surface shell. The high-temperature anti-oxidation coating is the main research content of carbon / carbon composite anti-oxidation, and the current anti-oxidation research is also focused on this aspect. SiC or Si3N4 anti-oxidation coating system can only be used under the temperature below 1700 ℃,
carbon / carbon anti-oxidation coating above 1700 ℃, must choose new materials or open up new ways, such as the use of iridium, platinum group Alloys and their compounds. Because carbon atoms have a strong affinity for each other, the carbon / carbon composite material has good stability at low or high temperatures. In addition to thermosetting resins, some thermoplastic resins can also be used as precursors for matrix carbon, such as polyetheretherketone (PEEK), polyetherimide (PEI), etc. Li Hejun. (2) Light specific gravity (less than 2. CVI process flow The prefabricated reinforcement is placed in a special CVI furnace, heated to the required temperature, and the hydrocarbon gas is introduced.
However, under the action of high temperature and high pressure, the resin carbon will also exhibit stress graphitization.; there are also many oxidation barriers studied, such as SiC, Si3N4, B4C , MoSi2, and carbides or oxides of Zr, Hf, Nb, Ta, etc. Although the CVI process cycle is longer, the overall performance of the prepared carbon / carbon composite material is better than the liquid phase impregnation method, and by changing the CVI process parameters, carbon / carbon composite materials with different structures and different properties can also be obtained. In order to improve the bonding state between the components in the matrix, the co-deposition technology of the carbon matrix and the ceramic matrix can be used.