Sulfur-Mediated Synthesis of Spherical Nickel Nanoparticles in a Chemical Vapor Reactor.

In this study, we investigated the effect of the sulfur content in the NiCl2 precursor on the shape of nickel nanoparticles (Ni-NPs) prepared by chemical vapor synthesis. We obtained spherical Ni-NPs when using anhydrous NiCl2 mixed with NiSO4 or Na2SO4 with a molar ratio of 0.002 as precursors without changing any other process parameters whereas faceted Ni-NPs when using only anhydrous NiCl2 as a precursor. First-principles calculations supported experimental results, which showed that NiSO4-mixed NiCl2 and Na2SO4-mixed NiCl2 precursors favored the growth of spherical NPs.

Pure copper nanoparticles prepared by coating-assisted vapor phase synthesis without agglomeration.

Modern electronic devices, such as smartphones and electric vehicles, require multilayer ceramic capacitors (MLCCs), which comprise highly pure Cu terminations and Ni electrodes. Vapor-phase synthesis (VPS) is a promising method for synthesizing nanoparticles (NPs) with high purity and crystallinity. However, the agglomeration of the NPs occurs during their synthesis, which degrades the performance of the MLCC electrodes owing to several factors, including electrical shorts and low packing density. This paper proposes a coating-assisted VPS to inhibit agglomeration using potassium chloride (KCl) as the coating agent. The agglomeration ratio of the Cu NPs synthesized by in-flight coating with KCl at 950 °C significantly decreased from 48.20% to 3.80%, compared to without KCl coating. Furthermore, X-ray fluorescence and X-ray diffraction analyses confirmed that the KCl coating agent and residual copper chloride were removed by washing with ammonium hydroxide.