Progression of Alignment in Stretched CNT Sheets Determined by Wide Angle X-ray Scattering

Wide angle X-Ray scattering was used to measure the progression of alignment when stretching carbon nanotube (CNT) sheets. The nanotubes were grown by an aerogel chemical vapor deposition process and drawn onto a drum rotating at a draw rate of 15 m/min to form a sheet. Samples were cut from this sheet at 0°, 10°, 25°, 45° and 90° with respect to the drawing direction. Samples stretched along the drawing direction reached 28% elongation at failure, whereas samples stretched 90° to the drawing direction reached 44% elongation at failure. In spite of this, the 0° sample had 50% of its nanotubes aligned along the stretching axis, while the 90° sample had 40% of its nanotubes aligned within ±10° of the stretching axis. The strength and modulus of samples cut along the growth direction were 1.8× and 4.9× higher than those cut in the 90° direction, with a smooth drop in strength observed as the cutting direction increased from 0° to 90°. This work reveals the relationship between sheet scale deformation and micro scale CNT reorientation.