A mechanism of surface hardness enhancement for H(+) irradiated polycarbonate

H(+) irradiation increases the surface hardness of polycarbonate. Nano indentation measurement shows that the hardness increases up to 3.7 GPa at the dose of 5 × 10(16) # cm(−2) and at the irradiation energy of 150 keV. In addition, the hardness increases with the dose and the energy of H(+) irradiation. In accordance with the nano indentation measurement, the Fourier-transform infrared spectroscopy (FTIR) depends on the dose and energy of H(+) irradiation. The peak at ∼1500 cm(−1) for the aromatic ring and the peak at ∼1770 cm(−1) for the C[double bond, length as m-dash]O stretch decrease with increasing dose and energy, while the increase of the dose and energy develops a new C[double bond, length as m-dash]O stretch vibration at ∼1700 cm(−1) and forms aromatic hydrocarbons at ∼1600 cm(−1). X-ray diffraction experiments are also consistent with the nano indentation measurement and FTIR spectra. Based on the experiments, we discuss a possible mechanism of the surface hardness enhancements by ion beam irradiation.