Damage Effects And Mechanisms Of Charge Particle Irradiation On Second Surface Mirror Of Kapton/Al

According to the equivalent substitution principle for space energetically charged particles, the ground simulation tests of space irradiation for Kapton/Al second surface mirrors were conducted by using the space synthesis irradiating facility in the thesis. The monostratum and synthetic irradiation effects of protons and electrons on the optical property of Kapton/Al films were investigated carefully. The damage mechanism was studied by means of ultraviolet/visible (UV/Vis) absorption spectra, atom force microscopy, Fourier transform infrared (FTIR) of spectra, X-ray photoelectron spectroscopy and Mass spectra. On the basis of quantum chemistry theory, bond breaking models on irradiation damage were built by simulation software. Chemical reaction mechanism on proton irradiation damage was presented.Experimental results show that, under irradiation of space energetically charged particles, the degradation in reflective property of Kapton/Al mainly occurred in the visible light and near infrared light region, in which the spectral reflectance reduces with increasing fluence. Superposition effects of sigle action are higher than synthetic irradiation effects. The optical property of Kapton/Al shows synergistic effect after the synthetic irradiation. When the irradiation energy is given, the change in solar absorptance under proton irradiation with fluence conforms to linear functional relation:Δα_s=kΦ. Under electron irradiation the change in solar absorptance with fluence conforms to power functional relation:Δα_s=αΦ^β.The obvious change in ccolour appeared on the surface of samples after sole proton irradiation and synthetic irradiation. The charged and discharged lacework is obvious by the observation of SEM when electronic fluence is up to 3×10¹⁵ cm^-2. It was found by AFM that some finger-like bulges (proton irradiation and synthetic irradiation) or hummock-like bulges (electron irradiation) appeared on the surface of Kapton/Al, which results the increase of surface roughness.After irradiation of charged particals, the edge of optical absorption gradually shifts from UV to the visible region and a strong increase in absorbance in the visible region was observed with increasing fluence. The increase of the absorbance in the visible region is attributed to the formation of new chromophores and auxochromes.The red shifting of the end absorption edge is related to the gradually reducing of the optical energy gap.Due to the bond breaking of imide and ether during the irradiation, free radicals and ion fragments from ionization and excitation combined to volatilizable micromolecles that escaped from the material, which resulted in the decrease of N and O and a surplus of carbon atoms. Some new components formed such as isocyano (–N= C=O), ketimine (C=C=N–) and hydroxylamine (C–O–N). Benzene ring may be destroyed to some extent and change to carbonizing products similar to graphite structure.Acording to saturated track modle, some bands which represent typical function group were selected to analyze quantitatively. The results indicate that all function groups in Kapton participate in the degradation process with similar damage cross-section during the irradiation. The damage cross-section increased with the increase of electronic energy loss, indicating that irradiation damage strongly depends on electronic energy loss, this conclusion is coincident with TRIM calculation.The electrons with the energy of 50 keV mainly destroyed the C–N bonds in the skin of Kapton, forming N⁺ ion fragment, accompany the break of partly ether linkage. The fragments of N⁺, O⁺ and C⁺ or radicals will combine to volatilizable micromolecles that escaped from the material, which resulted in the relative increase of carbon contents in benzene ring. Under the electron irradiation of 70 keV not only the above debonding reaction will occur, but also the volume conseration of ion fragments and radicals from debonding will increase, which may increase the possibility of crosslinking between molecules and forming new structure. With the increase of irradiation energy, the trend of carbon enrichment in the surface of Kapton film will increase.On the basis of quantum chemistry theory, five kinds of bond breaking models on irradiation damage were built by simulation software. The thermodynamic calculation indicates that five kinds of possible debonding reaction mode are easy to occur. The probability of debonding is arranged descendingly: C–N (imide ring)> C–C (imide ring)> C–N (joined to the carbon atom of benzene ring) >C–O–C.