Thermal performance of metallic nanoparticles in air

• Size and oxidation greatly influence the specific heat of metallic nanoparticles.
• Specific heat of nanoparticles can be 1 time larger than that of bulk.
• With only size effect considered, specific heat can be increased by 1.25 times.
• Oxidation has a more important effect than size on the specific heat of nanoparticle.
• Thermal conductivity (TC) of nanoparticle tablet can be smaller than 10% of bulk TC.

In this work, the thermal performance of copper and nickel nanoparticles was studied with the application of a differential scanning calorimeter method and a hot-wire method. With the absorbed water, oxidation, and the size effect all taken into consideration, this work shows that the absorbed water can be omitted at temperatures higher than 350 K. Both the size and oxidation greatly influence the specific heat of the nanoparticles. The specific heat of 50 nm copper nanoparticles can be 1 time larger than that of bulk at temperature about 550 K. With only the size effect considered, the specific heat of 50 nm copper or nickel nanoparticles can be greater than 1.25 times that of the specific heat of the bulk. Oxidation has a more important effect than size on the specific heat of 50 nm metallic nanoparticles. The thermal conductivity of the nanoparticle tablet will be much smaller than that of the corresponding bulk material, even much smaller than 10% of the bulk thermal conductivity.