Charged Particle Induced Damage In PEEK And PI And Radiation Shielding Enhanced By B₄C

There are different types of charged particles in the space environment,which will produce different kinds of radiation damage effects on materials and devices,leading to failures and even accidents of spacecraft on orbit.The development of lightweight and efficient radiation protection materials is an effective way to improve the external protection of spacecraft.Polyetheretherketone（PEEK）and polyimide（PI）have excellent comprehensive properties such as mechanics,heat and electricity,which are expected to become the matrix for the development of new polymer-based composite radiation protection materials.Research on charged particle radiation effects and mechanisms in depth.and B₄C as the reinforcing component prepared B₄C/PEEK and B₄C/PI polymer matrix composite materials.The development of lightweight and efficient extrinsic radiation protection technology has important scientific value and practical engineering significance.The PEEK and PI matrix materials irradiated by different energy electrons,protons and heavy ions,small-angle X-ray scattering（SAXS）,grazing incidence technique（GISAXS）and broadband dielectric spectrometer and other microstructure and performance analysis methods were used to study the radiation effects and mechanisms of the matrix materials in-depth.The microstructure evolution of PEEK before and after electron irradiation during tensile deformation was analyzed by using the SAXS technique in real time.The GISAXS technique was used to study the damage effects of the proton irradiated PEEK crystal.The dielectric constant change rule of PI materials before and after irradiation was analyzed by the broadband dielectric spectrometer test.B₄C/PEEK and B₄C/PI two composite materials were prepared successfully,the radiation protection effects of electrons,protons,neutrons and gamma rays were tested and analyzed.The research results show that after 120keV electron irradiation,the tensile strength and elongation at break of PEEK materials are reduced to a certain extent.The long period of the crystal inside the PEEK material is 15.95nm,and the long period of the crystal increases with the increase of the tensile strain,and the long period of the crystal about 82nm appear in the later stage of the tensile deformation.Low-energy electrons promote the rotation and cracking of the crystal platelets.120keV electron irradiation reduced the surface roughness of the PEEK sample,the melting temperature and crystallization temperature moved to low temperature,the crystallinity decreased,and the C=O content decreased.However,the results of infrared spectroscopy analysis showed that no new chemical groups were formed.Under the condition of 170keV proton irradiation,the obvious change of the surface crystal structure of PEEK is due to the transformation of part of the crystal region from the crystalline state to the amorphous state,showing the degeneration effect of the crystal region.Carbonized"black spots"appeared on the surface of the PEEK after 25MeV oxygen ion irradiation,while silicon particles formed on the surface after 25MeV silicon ion irradiation.After being irradiated with oxygen and silicon ions,the content of free radicals increased significantly.PEEK is irradiated with oxygen ions,and secondary crystallization peaks are generated in the cooling crystallization peak,but there is no secondary crystallization peak of PEEK irradiated by silicon ion irradiation.After the heavy ion irradiation,no new chemical groups were formed in the PEEK material,but the content of C=O groups decreased and the content of C-O groups increased,indicating that ion irradiation caused chemical bonds in PEEK samples to break.The PI material irradiated with 1MeV electrons,3MeV protons,10MeV protons,and 25MeV carbon ions can be produced a lot of free radicals,and the free radicals have an annealing effect.After 25MeV carbon ions irradiation,the content of free radicals produced by the PI material present an order of magnitude increase compared to that of the pristine material.The irradiated PI material does not produce new chemical groups,but the chemical bonds are broken,the contents of polar groups（C-N bonds and C=O bonds）reduced,and the content of non-polar groups（C-C bonds）increased.The yield strength and elongation at break of PI materials are slightly reduced after being irradiated.The dielectric constant of PI material decreases after irradiation,moreover,it decreases with the increase of irradiation fluence and test frequency.The dielectric loss does not change significantly in the low frequency range,but after 10⁴ Hz,the dielectric loss increases sharply with frequency increase.The electrical insulation of PI material is slightly reduced after irradiation.The above conclusions indicate that PEEK and PI are degraded to a certain degree mainly due to ionizing radiation damage after being irradiated by charged particles.Analog design of composites used by Geant 4,the B₄C enhanced component was added to the PEEK and PI matrix to prepare B₄C/PEEK and B₄C/PI composite materials with different B₄C content by compression molding method and in-situ synthesis method,respectively.The B₄C components are tightly combined with the matrix,and the distribution is uniform without agglomeration.After preparation,the number of free radicals in the two composite materials increased significantly.When the B₄C components were added,the position of the free radical peak shifted to the left and broadened.The crystallinity of B₄C/PEEK decreases with the increase of B₄C contents.The flexural strength of B₄C/PEEK increases with the addition amounts of B₄C components,while the elongation at break decreases.After adding the B₄C components,the thermal stability and dielectric constant of the two composites increase.The electronic and proton protection performance simulation of B₄C/PEEK composite material is consistent with the test results.It has good proton radiation protection ability,and the--more B₄C adding amounts the better the radiation protection performance.With the increase of B₄C addition amounts,the electron,neutron and gamma radiation protection performance of the B₄C/PEEK and B₄C/PI composites is enhanced.When the B₄C addition amounts is 30 wt%,the gamma radiation protection performance of the B₄C/PEEK composite material is roughly equivalent to that of metal aluminum.