Defect Evolution And Mechanical Properties Of 4H-SiC Irradiated By Multi Gradient High Energy Ions

With the proposal of the carbon peaking and carbon neutrality goals,nuclear energy,as a clean energy,plays an increasingly important role in the sustainable development of energy.However,the performance degradation of nuclear materials in reactors has always been the main bottleneck hindering the development of advanced nuclear energy.Silicon carbide is considered to be one of the good candidate materials for advanced nuclear energy because of its excellent characteristics such as high melting point,high thermal conductivity,high corrosion resistance and small neutron reaction cross section.During the service period,silicon carbide components have been in the environment of high temperature,high corrosion and high irradiation for a long time,resulting in swelling,hardening and creep.Therefore,the research on the defect evolution and mechanical properties of silicon carbide under high temperature irradiation can promote its application in the field of nuclear energy.In this paper,the radiation damage law of 4H-SiC was studied by multi gradient high energy Ne ion irradiation.The main content is to use Raman spectroscopy,infrared spectroscopy,nanoindentation and other characterization methods to analyze the defect evolution and hardness changes of 4H-SiC under high temperature irradiation.The conclusions are as follows:The relative Raman intensity decreased exponentially with the increase of dose,and gradually tended to the saturation value of 0.15.At the maximum dose of 8.05 dpa,there was no amorphous phenomenon,and the characteristic peak of E₁（TO）disappeared.Irradiation damage causes lattice distortion and chemical rearrangement of atoms,resulting in disordered Si-C bond and homonuclear Si-Sibond after irradiation.At the annealing temperature T<650℃,the defect evolution is mainly the compound of simple defects left by high temperature injection;At 650℃<T<850℃,defects gather and dislocation grow.Because defects are not fully compounded in limited annealing time,the annealing characteristics of the previous stage continue;At850℃<T<1000℃,Ne ions are captured by vacancy clusters and further evolve into extended defect clusters,hindering the recovery of defects.After irradiation,the total disorder degree of the sample increases with the increase of dose.The expansion of defect clusters in the low dose range is the main factor causing disorder,and the disorder in the high dose range is caused by the direct collision between atoms and the expansion of defect clusters.Annealing treatment reduces the irradiation damage,and the total disorder decreases with the increase of annealing temperature.Through the infrared spectrum analysis of the cross-section samples,it is found that the transmittance in the transverse optical phonon（TO）and longitudinal optical phonon（LO）regions decreases significantly after ion irradiation.The longitudinal optical phonon(==1)absorption peak was observed at 838 cm^-1,and the absorption peak showed red shift or blue shift at different doses.When the dose at 1.35 dpa and 4 dpa,the hardness of silicon carbide increases due to the dominant effect of defect hardening;At 5.25 dpa,the effect of chemical bond fracture on the hardness is greater,so the hardness decreases.When the irradiation dose reaches 8.05 dpa,the hardness is slightly higher than the unirradiated region.At this time,the chemical bond fracture and defect hardening reach a balance.