[M-IS11] [EJ] 結晶成長、溶解における界面・ナノ現象

[MIS11-P02] Crystallographically Favored Attachment of Just-Nucleated MoO₃ Nanoparticles in Gas Current

*石塚 紳之介¹、木村 勇気¹、佐藤 理佳子¹、山﨑 智也¹、羽馬 哲也¹ (1.北海道大学低温科学研究所)

キーワード：均質核生成、オリエンテッドアタッチメント

Nucleation and subsequent growth processes via homogeneous nucleation in vapor are enigmatic. To investigate evolution of phases, chemical composition and shape of just-nucleated nanoparticles in cooling evaporant, we developed a noble experimental apparatus that enables in-situ spatial scan of nucleating and growing nanoparticles with transmittance FT-IR spectroscopy. Here we experimentally show direct evidence that molybdenum oxide nanoparticle, just-nucleated from evaporated vapor, grown via attachment with crystallographically favored orientation in a gas current generated by the evaporation source. Just-nucleated nanoparticles showed characteristic IR absorbance of needle shaped MoO₃ and gradually changed into that of cubic and polyhedral shaped MoO₃ in ascending gas current. Each IR feature is consistent with that obtained by ex-situ IR measurements and morphological evolutions of collected nanoparticles. All needle, cubic and polyhedral shaped nanoparticles are attributed to MoO₃ with monoclinic crystal structure. The needle shaped nanoparticles are always elongated to [100] direction. Some particles, collected at growing zone, were partially attached at perpendicular planes to (100). We consider that the needle shape is the result of anisotropic growth of just-nucleated nanoparticles in supersaturated vapor. Then, the attachment between needle shaped particles fortuitously collided with the favorable orientation resulted in formation of cubic and polyhedral shaped particles in a gas current. These findings enrich the view on the pathways in nucleation and growth in vapor and give new insights into inter-particle forces that drive oriented attachment growth.