中子辐照6H-SiC热力学及辐照缺陷高温回复动力学OA

Silicon carbide(SiC)is a promising material for nuclear reactor structures due to its excellent radiation resistance and high-temperature performance.The behavior of irradiation damage and the mechanisms of high-temperature recovery in SiC directly affect its service performance and longevity in nuclear environments.This study investigated effects of neutron irradiation on properties of 6H-SiC,with a particular focus on high-temperature recovery mechanisms of irradiation-induced defects.Specifically,defect evolution and thermodynamic responses in nitrogen-doped(ND≈3.0×1019 cm-3)6H-SiC subjected to neutron irradiation at about 150℃and a fluence of 2.58×1020 n/cm2 followed by isochronal annealing were examined.Integrated techniques and first-principles calculations were employed to comprehensively analyze its structural and property evolution.The key findings were as follows.(1)Significant lattice swelling was observed during the irradiation,with a swelling rate of 0.416%along the a-axis,0.430%along the c-axis,and 1.310%in the unit cell volume,while all maintaining integrity of the single-crystalline structure.(2)A 14.7%increase in specific heat capacity was recorded,with 375.4 J/g of stored irradiation energy being released during heating from 100℃to 500℃.(3)A four-stage defect recovery kinetic model was proposed based on the recovery of lattice parameters and the evolution of Raman spectra:Stage I(room temperature(RT)-600℃),primarily dominated by close-range recombination of carbon Frenkel pairs driven by migration energy(Ea)of 0.14 eV;Stage II(600-850℃),recombination of silicon Frenkel pairs and migration of carbon interstitials(Ea=0.26 eV);Stage III(850-1200℃),lattice reconstruction(Ea=0.65 eV);Stage IV(1200-1500℃),long-range diffusion of carbon vacancies(VC)and dissociation of NCVSi complexes(Ea=1.50 eV).(4)The presence of nitrogen-stabilized NCVSi defect configurations was confirmed by a characteristic emission peak at 826 nm(634 cm-1 Raman shift)when excited with 785 nm light.This study quantitatively reveals the defect recovery pathways and migration energies in neutron-irradiated 6H-SiC,providing a critical foundation for evaluating radiation damage,predicting performance,and optimizing annealing processes in nuclear-grade SiC materials.