open access

https://doi.org/10.14943/doctoral.k16120

https://hdl.handle.net/2115/93612

液体コアを有するコア・シェルナノ粒子のダストプラズマを用いた合成プロセス の開発

英語

Core-Shell

2024-09-25

Hokkaido University

xii, 79p.

Core-shell nanoparticles synthesized by depositing solid shells around liquid cores are useful as a reusable latent heat storage material. However it is challenging to deposit the shell films around liquid cores. This work demonstrates a process flow to deposit amorphous carbon films around liquid tin nanodroplets retained in a capacitively coupled plasma (CCP). High-pressure magnetron sputtering with a tin target, which was placed at the top of a vacuum chamber was used for synthesizing tin nanoparticles. Tin nanoparticles were transported to CCP at the bottom of the chamber, and they were trapped above the sheath which was formed above the rf electrode. Tin nanoparticles were heated above the melting point by ion bombardment in CCP, then, we deposited shell film (an amorphous carbon film) using plasma-enhanced chemical vapor deposition. Core-shell nanoparticles retained in CCP were collected by applying a positive bias voltage to an electrode placed inside the rf electrode. It was observed that the electrode potential was higher than the plasma potential when a bias voltage of +70 V was applied to the electrode, which enabled the efficient transportation of nanoparticles to the electrode surface. The nanoparticles were analyzed using electron microscopy (SEM, TEM), energy dispersive spcetroscopy and electron diffraction. TEM images of core-shell nanoparticles showed completely spherical cores, indicating the deposition of amorphous carbon films around melted liquid tin nanodroplets. The melting of tin nanoparticles in CCP was confirmed by estimating their temperatures using a heat transfer theory. We observed the melting of cores, which was detected by the change in the electron diffraction pattern from polycrystalline to amorphous, at the melting point of metal tin. The electron diffraction pattern was obtained while heating core-shell nanoparticles inside TEM. We did not observe the breakdown of the shell films at the melting of the cores, suggesting that the amorphous carbon films were robust against the volume expansion of cores. In addition, the amorphous carbon films protected the core from the oxidation.

2024-09-25

甲第16120号

博士(工学)

(主査) 教授 佐々木 浩一, 教授 富岡 智, 教授 柴山 環樹

工学院（量子理工学専攻）

博士論文

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