High temperature electrical and thermal properties of the bulk carbon nanotube prepared by SPS

Bulk multi-walled carbon nanotube was prepared by spark plasma sintering at 1700 °C under a pressure of 50 MPa in vacuum. The density of the bulk sample reaches 72% of the theoretical density of the carbon nanotube, 2 g/cm³. The high temperature thermal conductivity and electrical conductivity of the bulk material were measured in the directions perpendicular and parallel to the pressure direction. Both the thermal conductivity and electrical conductivity show apparent anisotropy. The thermoelectric power has close values in the two different directions and takes positive values in the whole measured temperature range (360–840 K).