NG-CT-10 and NG-CT-20 are newly developed grades of nuclear-grade graphite from China.In this study,their oxidation behaviors were experimentally investigated using thermal gravimetric analysis.Microstructural evoluti...NG-CT-10 and NG-CT-20 are newly developed grades of nuclear-grade graphite from China.In this study,their oxidation behaviors were experimentally investigated using thermal gravimetric analysis.Microstructural evolution before and after oxidation was investigated using scanning electron microscope,mercury intrusion,and Raman spectroscopy.The apparent activation energy of NG-CT-10 nuclear graphite is 161.4 kJ/mol in a reaction temperature range of 550–700℃and that of NG-CT-20 is 153.5 kJ/mol in a temperature range of 550–650℃.The activation energy in the inner diffusion control regime is approximately half that in the kinetics control regime.At high temperatures,the binder phase is preferentially oxidized over the filler particles and small pores are generated in the binder.No new large or deep pores are generated on the graphite surfaces.Oxygen can diffuse along the boundaries of filler particles and through the binder phase,but cannot diffuse into the spaces between the nanocrystallites in the filler particles.Filler particles are oxidized starting at their outer surfaces,and the sizes of nanocrystallites do not decrease following oxidation.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51576103)the National S&T Major Project(No.ZX06901)
文摘NG-CT-10 and NG-CT-20 are newly developed grades of nuclear-grade graphite from China.In this study,their oxidation behaviors were experimentally investigated using thermal gravimetric analysis.Microstructural evolution before and after oxidation was investigated using scanning electron microscope,mercury intrusion,and Raman spectroscopy.The apparent activation energy of NG-CT-10 nuclear graphite is 161.4 kJ/mol in a reaction temperature range of 550–700℃and that of NG-CT-20 is 153.5 kJ/mol in a temperature range of 550–650℃.The activation energy in the inner diffusion control regime is approximately half that in the kinetics control regime.At high temperatures,the binder phase is preferentially oxidized over the filler particles and small pores are generated in the binder.No new large or deep pores are generated on the graphite surfaces.Oxygen can diffuse along the boundaries of filler particles and through the binder phase,but cannot diffuse into the spaces between the nanocrystallites in the filler particles.Filler particles are oxidized starting at their outer surfaces,and the sizes of nanocrystallites do not decrease following oxidation.
