Coalescence Of Metal Nanoparticles Research Articles

Solvent‐Driven Transformation of Microsized Metal Particles into a Nanoporous Structure and Its Application to Ultrafast‐Charging Batteries

AbstractThe coalescence of metal nanoparticles in colloidal solutions is a universal and ubiquitous phenomenon. Using this behavior, a simple yet effective route is developed that enables the spontaneous transformation of microsized metals into nanoporous structures in specific electrolyte solvents. The criteria for selecting solvents and counterpart metals suitable for generating nanoporous structures are derived based on the classical theory of acid–base reactions and quantum chemistry based on density functional theory. When employing the developed method for anodes for Na‐ion batteries, the anodes prepared using microsized Sn, Pb, Bi, and CuS particles store 592, 423, 383, and 546 mAh g−1, respectively, at 10 C with cycling lifetimes of 3000−6000 cycles. This study provides fundamental framework for selecting solvents to realize low‐cost anodes with large capacities, long cycling lifetimes, and excellent rate performances. Moreover, the findings can be extended to other functional materials that can exploit their large specific surface areas.

In Situ TEM Observation of the Atomic Transport Process during the Coalescence of Au Nanoparticles.

In practical applications, the coalescence of metal nanoparticles (NPs) is a major factor affecting their physical chemistry properties. Currently, due to a lack of understanding of the atomic-level mechanisms during the nucleation and growth stages of coalescence, the correlation between the different dynamic factors in the different stages of NP coalescence is unclear. In this study, we used advanced in situ characterization techniques to observe the formation of atomic material transport channels (Au chains) during the initiation of coalescence nucleation. We focused on the movement and migration states of Au atoms and discovered an atomic ordered arrangement growth mechanism that occurs after the completion of nucleation. Simultaneously, we used density functional theory to reveal the formation principle of Au chains. These findings improve our understanding of the atomic-scale coalescence process, which can provide a new perspective for further research on coalescence atomic dynamics.

Coalescence of Metal Nanoparticles as the Origin of Nanocapillary Forces in Carbon Nanotubes

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 l...

Tuning of electrical and structural properties of metal-polymer nanocomposite films prepared by co-evaporation technique

Nanocomposites consisting of Au and Ag nanoparticles embedded in Teflon AF 1600 (Teflon) and Nylon 6 (Nylon) matrices were prepared by a simultaneous vapor phase deposition of both the polymer and the metal. The composite films were deposited between two Au-Pd alloy electrodes prepared by sputtering onto kapton foil substrates enabling further electrical measurements. The electrical properties of the composites are strongly influenced by the metal filling factor and changes in the microstructure. At first, the dependence of the resistivity of the composites consisting of various Ag and Au nanoparticle concentrations was investigated. The resistivity is characterized by a threshold region with a critical metal filling factor. Changes in the microstructure, in particular, can occur as a result of an induced electric field in between the metal nanoparticles and a heat treatment. The I–V characteristics of Teflon AF composites for different Au concentrations were studied thoroughly. An increase in the slope of the I–V curve up to a certain voltage (breakdown voltage) was observed. This phenomenon is accompanied by the field induced tunneling of the charge carriers which enhances the conductivity. The change in conductivity was also analyzed for Nylon nanocomposites with various Au concentrations in the temperature range 20–180 °C. The observed temperature dependence is explained by activated electron tunneling between metal nanoparticles and by rearrangements in the microstructure (e.g. coalescence of metal nanoparticles).