부산대학교 도서관

Advances in nanofabrication technology allow gold-filled carbon nanotubes (CNTs) to be used as pin-tip injectors for additive nanomanufacturing; however, the refilling of CNT cartridges is still a technical challenge. An isolated CNT bridged and biased between two electrodes can be filled with metals owing to mass transport caused by electromigration forces. However, severe Joule heat-induced damage of the host CNT makes it difficult to refill CNT cartridges using this method. Another approach for Joule heat-assisted filling of CNTs is shifting the point of the highest temperature from the CNT cartridge to the supportive CNT. We have previously demonstrated the controlled growth of gold nanowires in CNTs by thermomigration and coalescence of metal nanoparticles. It is important to understand the origin of nanocapillary forces in CNTs to optimize the refilling process of CNT cartridges. In this study, we focus on the experimental conditions when coalescence of gold nanoparticles becomes the cause of gold loading in CNTs. We analyzed the process of coalescence by in situ transmission electron microscopy. For gold nanoparticles, in the absence of a strong thermal gradient, coalescence is the main factor responsible for elongation of the encapsulated nanowire. Large nanoparticles always absorb smaller nanoparticles, which leads to elongation of the encapsulated nanowire. In the case of platinum nanoparticles, the strong interaction between platinum and carbon layers does not allow the process of coalescence to be the main mechanism; therefore, thermomigration is the origin of the nanocapillary forces. The results reveal a metal-dependent mechanism of CNT loading.