Radiation-induced mechanical property changes of CNT yarn

Stimulated by the previous findings that ion beam can induce carbon nanotube (CNT) welding, we studied the irradiation effects on CNT yarns by proton irradiation. A 2.5 MeV proton beam was transmitted through a 25 μm thick Ti window and irradiated CNT yarn in air. The yarn, of about 40 μm in diameter, was fabricated by pulling and spinning CNT bundles from a CNT aligned film. After irradiation to an ion fluence of 5 × 1012, 1 × 1013, 1 × 1014, and 1 × 1015 cm−2, Raman spectroscopy was performed to study defect behavior by comparing intensity changes to the D and G bands at 1350 cm−1 and 1560 cm−1, respectively. The analysis revealed a decreasing defect level up to 1 × 1013 cm−2, followed by an increasing defect level with increasing fluence. The mechanical properties of the yarns are characterized by using a tensile tester with a strain rate of 0.2 mm/min at room temperature. The maximum tensile strength occurred at a fluence of 1 × 1013 cm−2. With increasing proton fluencies, the fracture strain shows gradual enhancement.