Microstructure, grain and nanowire growth during selective laser melting of Ag-Cu/diamond composites

Selective laser melting (SLM) technique is a viable alternative to fabricating metal matrix composites (MMCs) with controllable structures; however, its implementation remains challenging because of the unpredicted defects arising from the reinforcement. This study primarily examined the microstructural evolution and grain growth in the Ag-Cu/diamond composites at the molten pool scale during the SLM process via a thermodynamic analysis. The feasibility of manufacturing Ag-Cu/diamond composites was verified using several processing parameters. Moreover, the influence of energy density on the microstructures and grain growth was also demonstrated theoretically and experimentally. The formation of different kinds of grain morphologies in the molten pool was ascribed to the temperature gradient and cooling rate, corresponding to the direction and size of grain growth. The generation of Ag-Cu nanowires at the grain boundaries was firstly found in the SLM technique, which was related to the pressure stress generated by the high cooling rate of SLM. This work hopefully opens new paths for the applications of high-performance Ag-Cu/diamond MMCs in various application fields. It also provides new possibilities for the controllable manufacturing of Ag nanowires during SLM.

Synthesis of flexible Co nanowires from bulk precursors

This work reports a method of producing flexible cobalt nanowires (NWs) directly from the chemical conversion of bulk precursors at room temperature. Chemical reduction of Li₆CoCl₈ produces a nanocomposite of Co and LiCl, of which the salt is subsequently removed. The dilute concentration of Co in the precursor combined with the anisotropic crystal structure of the hcp phase leads to 1D growth in the absence of any templates or additives. The Co NWs are shown to have high saturation magnetization (130.6 emu g⁻¹). Our understanding of the NW formation mechanism points to new directions of scalable nanostructure generation.

This work reports a method of producing flexible cobalt nanowires (NWs) directly from the chemical conversion of bulk precursors at room temperature.

Energy Dissipation and Asymmetric Excitation in Hybrid Waveguides for Routing and Coloring

The delivery of optical signals from an external light source to a nanoscale waveguide is highly important for the development of nanophotonic circuits. However, the efficient coupling of external light energy into nanophotonic components is difficult and still remains a challenge. Herein, we use an external silica nanofiber to light up an organic-inorganic hybrid nanowaveguide, namely, a system composed of a polymer filament doped with MoS₂ quantum dots. Nanofiber-excited nanowaveguides in a crossed geometry are found to asymmetrically couple excitation signals along two opposite directions, with different energy dissipation resulting in different colors of the light emitted by MoS₂ quantum dots and collected from the waveguide terminals. Interestingly, rainbow-like light in the hybrid waveguide is achieved by three-in-one mixing of red, green, and blue components. This heterodimensional system of dots in waveguide represents a significant advance toward all-optical routing and full-color display in integrated nanophotonic devices.