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Room temperature nanojoining is an important phenomenon that has to be understood well for use in different applications, for example, for assembly of nanoscale building blocks into nanoscale and microscale structures and devices. However, the mechanism for nanoparticle joining at room temperature is not well established. In this research, we employed molecular dynamics simulation to explain how and why silver nanodisks are joined/assembled but with their original shape unchanged. To support our theoretical observations, we compared our simulation results to SEM and HRTEM observations of joined silver nanodisks. It was found that joining at a wide temperature range (1–500 K) can be done through short movement and rearrangement of surface atoms and subsequent elastic or plastic deformation of the particles, resulting in perfect crystal alignment at the joint interface. Our simulation shows the crystal defects such as dislocations due to initial lattice mismatch of the crystals can be sintered out to yield a perfect crystalline structure at the interface between joined particles, which is supported by the experimental observations.

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The utilization of high-aspect-ratio silver nanobelts (NBs) is reported with the typical silver micro flakes to develop advanced electrical conductive adhesive (ECA) composite materials. Ag NBs (10-40 nm thick, 100-400 nm wide and 1-10 mm long) were synthesized by chemical reduction of silver nitride. The incorporation of a small amount of the Ag NBs (NBs to flakes weight-ratio K ¼ 0.03) into a conventional ECA with 60 wt% Ag micro flakes results in an electrical conductivity enhancement by 1300%. It is also found that adding a 2 wt% (K ¼ 0.03) of the NBs into a conventional ECA with 80 wt% Ag flakes reduced the bulk resistivity to 3 Â 10 À5 V Á cm for the hybrid ECAs, which is comparable to that of a typical eutectic solder, showing great potential as an alternative electrical interconnect materials.

Thermal instability of metallic nanoparticles is typically attributed to chemical attack by contaminants. However, thermodynamic stability is independent of other affecting parameters. The importance of this will be clarified when the structural change toward a more stable thermodynamic condition may be followed by a chemical reaction with the surroundings, which may cause a wrong diagnosis. In this research, molecular dynamics simulations and experimental observations were performed to investigate the effect of crystallography and surface texture on stability at high temperature using two closely related model nanoparticles: silver nanobelts and pentagonal nanowires. Previously, the instability of silver nanowires was associated with sulfidation of the wire at high temperature. However, we found that the silver nanowires are inherently unstable at high temperature, degrading due to the high-energy nature of the nanowire's predominately (100) crystallographic surface and pentagonal geometry. In contrast, the silver nanobelts resist thermal degradation up to 500 °C because of their predominately low-energy (111) crystallographic surfaces. In this case study, we successfully demonstrate that inherent thermodynamic stability driven by morphology is significant in metallic nanoparticles, and should be investigated when selecting a nanoparticle for high temperature applications. Moreover, we identify a new one-dimensional nanoparticle, the silver nanobelt, with inherent high-temperature stability.

On the measurement of relative powder-bed compaction density in powder-bed additive manufacturing processes. Jmade (2018),