Fabrication and thermal conductivity of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes(CNTs) were coated by tungsten using metal organic chemical vapor deposition.Magnetic stirring was employed to disperse the W-coated CNTs(W-CNTs) in a Cu matrix,and then,the mixed powders were consolidated by spark plasma sintering.The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vol%,but high content of W-CNTs(10vol%) resulted in the presence of clusters.The W-CNT/Cu composites containing low content of W-CNTs(<5.0vol%) exhibited a higher thermal conductivity than the sintered pure Cu,while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs.The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites.The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing.When the W-CNT content was 2.5vol%,the W-CNT/Cu composite obtained the maximum value of thermal conductivity.The thermal resistance of the(W-CNT)-Cu interface was predicted in terms of Maxwell-Garnett effective medium approximation,and its calculated value was about 3.0×10-9m2·K·W-1.