Spark plasma sintering of sub-micron copper reinforced with ruthenium–carbon nanotube composites for thermal management applications

• The procedure to achieved good dispersion of Ru-CNTs was developed.
• Influence of SPS parameters on Cu-CNT-Ru composites.
• The CTE of Cu-2 vol% CNT was reduced by as much as 79% at 100 °C.
• The addition of ruthenium has positive influence on the oxidation state of copper.
• Densification of samples has a significant influence in the thermal conductivity.

Submicron copper reinforced with carbon nanotubes–ruthenium composites as suitable material for thermal management applications has been fabricated by Spark plasma sintering (SPS). The slurry of CNT–Ru was uniformly dispersed into copper matrix by mechanical stirring process using ethanol as a mixing medium. The composites powders were initially annealed for 30 min at 550 °C with heating rate of 5 °C/min under argon. The annealed powders were then consolidated at sintering temperature of 600 °C and 650 °C with a constant pressure of 50 MPa and the holding time of 5 min. The relative density of 98.15% was obtained for Cu-2 vol%CNT while that of Cu-2 vol%CNT-0.5 vol%Ru was of 97.08%. The Vickers hardness values of Cu-2 vol%CNT-0.5 vol%Ru sintered at 650 °C were found to be 130.4 HV. The coefficient of thermal expansion of 2.3 × 10−6/°C was measured for copper reinforced with 2 vol% CNT sample at 100 °C. The thermal conductivity of 323 W/mK and 279 W/mK was measured at 100 °C for Cu and Cu-1CNT-0.5 vol%Ru. The X-ray photoelectron spectroscopy was performed on the samples surface in order to determine the effect of additives on the copper surface. XPS revealed that addition of Ru reduced copper oxidation at the surface.