Real-time Observation of Microstructural Dynamic Process in Colloidal Solution under Dilatant Phenomena

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K13890
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13040:Biophysics, chemical physics and soft matter physics-related
• Research Institution: University of Tsukuba
• Principal Investigator: Akada Keishi 筑波大学, 数理物質系, 助教 (50815892)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: レオロジー / 非ニュートン流体 / 小角散乱 / コロイド

Outline of Final Research Achievements

The phenomenon in which viscosity increases with shear stress is called shear thickening (dilatancy), and it is desired to elucidate the mechanism to control its properties. In this study, simultaneous measurements of viscosity and small-angle/ultra-small angle X-ray scattering (Rheo-SAXS/USAXS) were performed to elucidate the shear-thickening process through real-time structural observation. The obtained results show that with increasing viscosity, elliptical silica flocs are formed and aligned in the flow direction. Furthermore, we developed a fast Rheo-SAXS/USAXS with msec time resolution and clarified the transient phenomena that cause shear thinning. A self-made shear cell with piezoelectric operation has also been developed, which enables simultaneous shear measurement for small sample volumes of micro-L.

Free Research Field

レオロジー

Academic Significance and Societal Importance of the Research Achievements

せん断応力を印加すると粘度が増大する特性はシアシックニング(shear thickening)と呼ばれ、インクノズルの詰まりや電極スラリーの塗布ムラの原因になる一方、衝撃を加えると硬化する特徴を活かした衝撃吸収材等への応用が見込まれる。申請者はレオメーターとX線透過溶液セルを使い、溶液粘度と小角X線散乱/極小角X線散乱の同時測定(rheo-SAXS/USAXS)による現象発生の過渡状態を調べることで，シアシックニング現象発生時の粒子の挙動を明らかにした。得られた知見は衝撃応答する粒子のダイナミクスを明らかにし，シアシックニング現象の制御に繋がる。