Study On Mechanical Properties And Microstructure Of Borosilicate Glass Before And After Irradiation

Nuclear power is a very important new energy for human society.However,the development of nuclear power has also produced a lot of radioactive waste.Radioactive waste does great harm to environment.The problem of radioactive waste treatment needs to be solved urgently.Currently,an internationally recognized method is that high-level radioactive waste（HLW）would be immobilized firstly and then be settled in a underground geologic repository while borosilicate glass is the only material that has been widely used in industry.The long-term storage of glass solidification in the deep underground requires detailed research on the properties of the glass solidification under the radiation environment.The study on the mechanical properties of borosilicate glass under irradiation is of great significance to the safe disposal of HLW.In order to study the changes of macroscopic properties and microstructure of borosilicate glass before and after irradiation,eight kinds of borosilicate glass with different components were firstly refined in this work.The hardness and modulus of samples were obtained by nano-indentation technology.The microstructure of the sample was analyzed and measured by infrared spectroscopy（FTIR）and Raman spectroscopy（Raman）.Then borosilicate glass samples were irradiated with 0.3 MeV P-ions,4 MeV Kr-ions,5 MeV Xe-ions and 8 MeV Au-ions,respectively.The modification of the samples’mechanical properties before and after radiation has been investigated with nano-indentation measurement.The grazing incident X-ray diffraction（GIXRD）was employed to analyze the phase structure.The microstructure evolutions of irradiated borosilicate glasses were characterized by Raman spectroscopy.The relationship between the microstructure and hardness of irradiated glass was analyzed and discussed in detail.The results showed that:（1）With the increase of SiO₂/B₂O₃,both the values of hardness and modulus for samples increased.The hardness and modulus of SNBS1 glass was 3.95 GPa and44.85 GPa.The SNBS8 sample’s hardness and modulus increased to 6.54 GPa and71.73 GPa,respectively.The density of glass also increased significantly.The density of SNBS1 glass was 2.16 g/cm³ and the density of SNBS8 glass increased to 2.35g/cm³.（2）The change of hardness and modulus was related to silicon and boron in glass samples.With the increase of silicon content,the network structure of Si-O-Si continuously enhanced,then the internal network structure of glass was more compact,and the hardness and modulus of samples also increased.As the content of boron decreases,the[BO₃]structure in the sample decreased and the number of[BO₄]structure increased.The network structure about boron changed from two-dimension plane structure to a three-dimensional structure,which caused the increase of sample hardness.（3）With the increase of the irradiation dose,both the values of hardness and modulus for samples irradiated with P、Kr、Xe and Au ions dropped and then saturated.The trends of hardness variations for four kinds of ions with different energies were similar,and the change of modulus also followed the same rule.The maximum variation of NBS2 samples’hardness and modulus was about 35%and 18%,respectively.（4）The decrease of network polymerization and the increase of structural disorder were suggested by Raman spectra.In addition,results from this work also suggested that the main factor for the evolutions of the hardness and modulus of the borosilicate glass under ion irradiation was the change of the deformation of glass network,which was caused by nuclear energy deposition in samples.（5）The type,energy and dose of ions used in room temperature irradiation will not affect the crystal structure of the sample.The results indicated that borosilicate glass still remained amorphous after irradiation.In this work,the mechanical properties of unirradiated glass have been studied,which is helpful to design glass solidification materials with better properties.In addition,this work found that the damage of low-energy ions and high-energy ions to the samples was roughly the same.In future,we may choose to use low-energy ions to study the irradiation effect of the samples,which can better reduce the research cost.This work also has important guiding significance for understanding the changes of mechanical properties of glass solidification during the disposal process.