A high temperature X-ray diffraction study of the influence of MWCNTs on the thermal expansion of MWCNT/Ni composites

The inclusion of multiwall carbon nanotubes (MWCNTs) into metallic matrices is expected to improve their electrical and mechanical performance. This work analyses the lattice thermal expansion behavior of MWCNT-reinforced Ni composites in order to understand the influence of CNTs on their thermomechanical properties. The lattice thermal expansion coefficient (CTE) of the composites was estimated from X-ray diffraction measurements as a function of the temperature. The MWCNT-reinforced composites show higher lattice CTE (up to 12%) compared to pure Ni. This behavior is mainly produced by the expansion mismatch between the matrix and the reinforcements. We suggest three main mechanisms that explain the behavior of the CTE of metallic matrices in presence of MWCNT. These mechanisms correlate to the anchoring effect observed in previous macroscopic measurements of thermal expansion carried out on the same system.