Study of SiC/SiO2 oxidation-resistant coatings on matrix graphite for HTR fuel element

The improvement of the oxidation resistance of fuel element matrix graphite used in high temperature gas-cooled reactor (HTR) is indispensable for the further improvement of the safety of HTR. The stability of SiC coatings and SiC/SiO2 multilayer coatings in helium with little impurities is analyzed on the basis of thermodynamic calculation and it is found that SiC/SiO2 multilayered coatings are suitable oxidation resistant materials for graphite used in HTR fuel elements because they are stable both at the normal operation conditions and accidental conditions of HTR. SiC/SiO2 multilayer coatings were synthesized on the surface of fuel element matrix graphite of HTR by combination of vapor reaction diffusion, slurry method and high temperature oxidation in air; the oxidation behavior of SiC/SiO2 coated fuel element matrix graphite of HTR in different atmosphere are investigated and it is shown that SiC/SiO2 coatings can keep their stability under different experiment conditions which graphite used in HTR may encounter and greatly improve the oxidation resistance of fuel element matrix graphite of HTR.