Physical properties of carbon nanotube sheets drawn from nanotube arrays

We report mechanical, thermal, and electrical properties of novel sheet materials composed of multiwalled carbon nanotubes, drawn from a CNT array. At low loading there is some slippage of CNTs but at higher loading tensile strength sigma(0) = 7.9 MPa and Young's modulus E = 310 MPa. The room-temperature thermal conductivity of the CNT sheet was 2.5 +/- 0.5 W m(-1) K-1, giving a thermal conductivity to density ratio of kappa/rho = 65 W m(-1) K-1 g(-1) cm(3). The heat capacity shows 1D behavior for T > 40 K, and 2D or 3D behavior at lower temperatures. The room-temperature specific heat was 0.83 J g(-1) K-1. The iV curves above 10 K have Ohmic behavior while the iV curve at T = 2 K is non-Ohmic, and a model to explain both ranges is presented. Negative magnetoresistance was found, increasing in magnitude with decreasing temperature (-15% at T = 2 K and B = 9 T). The tensile strength, Young's modulus and electrical conductivity of the CNT sheet are low, in comparison with other CNT materials, likely due to defects. Thermal conductivity is dominantly phononic but interfacial resistance between MWCNTs prevents the thermal conductivity from being higher. (C) 2012 Elsevier Ltd. All rights reserved.