Influence of Warm Oxide Layer on Wettability and Contact Angle for Heat Transport Devices

Recently, high heat density has become a problem in electronic devices. Therefore, high heat-transfer efficiency is required in copper heat exchangers. Improvement of wettability is reported to improve the heat-transfer efficiency. In previous studies, copper oxide layer improves the wettability. In this study, we focus on a copper oxide layer produced under warm conditions (from 200 to 300 °C), which are suitable oxidation conditions for improving wettability. Experimental results showed that the surface of the specimens was covered by the oxidation layer and took on a black color. Furthermore, the wettability was improved by the warm copper oxide layer. While, the surface roughness was approximately constant to each warm oxidized specimen. Whereat, the warm oxide layer was observed by SEM (sanning electron microscope). The results from SEM observations showed that the warm copper oxide layer consisted of stacks and combinations of nanoscopic warm oxidation particles. Thus, the warm oxidation layer hasnanoscopic surface asperities. It is seemed that these nanoscopic asperities improved the wettability.