Thermal expansion of Cu/carbon nanotube composite wires and the effect of Cu-spatial distribution

Abstract We report for the first time the coefficient of thermal expansion (CTE) of Cu/carbon nanotube (Cu/CNT) macroscopic wire composites and its strong dependence on CNT-Cu mixing. Homogeneous composite wires with 40 vol% nanotubes uniformly mixed in continuous Cu matrix showed CTE ∼4.42 × 10−6  °C-1 (∼26% Cu-CTE and similar to Si-CTE). The value matches with Turner’s model predictions implying that when nanotube-Cu shared contact is high, both low thermal expansion and high bulk modulus of CNTs contribute to offsetting Cu thermal expansion. In contrast, absence of or non-uniform CNT-Cu mixing i.e., reduced shared interface led to higher wire-composite CTEs (∼53−92% Cu-CTE) even with higher CNT vol%.