Effect of thermal treatments on structures and mechanical properties of aerogel-spun carbon nanotube fibers

• The effects of heat treatment on aerogel-spun CNT fibers were investigated.
• Two cooling methods (in furnace or in air) were compared.
• The tensile strengths of the CNT fibers improved about 50% after 250 °C treatment.
• The fiber showed a 217% increase in its modulus after air cooling at 400 °C.
• Mechanical enhancement was due to superposition of oxidation and crystallization.

In this study, the structural changes, mechanical and electrical properties of carbon nanotube (CNT) fibers after thermal treatments in air with different cooling conditions have been investigated. The tensile strength of the CNT fibers improves about 50% after heat treatment at 250 °C, due to the increase in crystallinity and oxygen-containing groups. After the thermal treatment followed by air cooling, the CNT fiber shows a 217% increases in its tensile modulus and the tensile failure model changes from ductile behavior to brittle fracture. In addition, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and field emission scanning electron microscopy are conducted to observe the structural changes of CNT fibers before and after thermal treatments.