To meet the need of high performance thermal management materials in the field of space application thermal interfaces made out of copper composite materials reinforced with carbon nanotube (CNT) have been prepared via powder metallurgy combined with hot extrusion. The CNT content was controlled between 3 and 25 vol.%. The distribution of CNT in the composite powder was realized with ultrasonic supported mixing. The mixed powders were consolidated with Spark Plasma Sintering (SPS) to a density above 70 %. Afterwards hot extrusion compacted the composite materials to a density close to 100 % and introduced a CNT alignment parallel to the extrusion direction. After machining and etching the CNT are standing free one the thermal interface. The performance under inert and vacuum conditions regarding the effective thermal conductivity across the interfaces was measured with flash method after machining and etching under the same contact pressure.