2023-04-27 アルゴンヌ国立研究所(ANL)
Chemical engineers at the U. of I. have developed a new metric for understanding how soft materials yield to stress – an advancement that will help solve various materials engineering challenges, such as how to formulate better 3D printing inks. Image courtesy Oak Ridge National Laboratory
◆研究チームは、流れに依存する材料の性質に関する構造-性質関係を研究する高度な顕微鏡技術である「X線光子相関分光法(XPCS)」を使用し、マクロな観察と微視的レベルでの出来事を直接結び付けることに成功した。
◆この研究成果は、3Dプリントインク、柔軟な電子機器やセンサーの製造、バイオメディカルインプラントの正確な印刷、山崩れや雪崩のコントロール、食品加工品や個人用品のテクスチャーの改善など、さまざまな材料工学上の課題に進展をもたらす可能性があるという。
＜関連情報＞
X線光子相関分光法(XPCS)による濃縮コロイド系の降伏遷移の解明 Investigation of the yielding transition in concentrated colloidal systems via rheo-XPCS
Gavin J. Donley,Suresh Narayanan,Matthew A. Wade,Jun Dong Park,Robert L. Leheny ,James L. Harden and Simon A. Roger
Proceedings of the National Academy of Sciences Published:April 24, 2023
DOI:https://doi.org/10.1073/pnas.2215517120
Significance
The flow and deformation behavior of colloidal glasses are important to a wide range of potential applications, but direct connections between the macroscopic flow/deformation and microscopic structure or dynamics have been difficult to come by. In this work, we utilize simultaneous stress-controlled rheology and x-ray scattering to bridge this gap. By probing the onset of yielding in a colloidal glass, we determine that the transition from recoverable to unrecoverable deformation is strongly linked to the loss of structural memory and the acceleration of the nanoscale fluctuations of the glass.
Abstract
We probe the microstructural yielding dynamics of a concentrated colloidal system by performing creep/recovery tests with simultaneous collection of coherent scattering data via X-ray Photon Correlation Spectroscopy (XPCS). This combination of rheology and scattering allows for time-resolved observations of the microstructural dynamics as yielding occurs, which can be linked back to the applied rheological deformation to form structure–property relations. Under sufficiently small applied creep stresses, examination of the correlation in the flow direction reveals that the scattering response recorrelates with its predeformed state, indicating nearly complete microstructural recovery, and the dynamics of the system under these conditions slows considerably. Conversely, larger creep stresses increase the speed of the dynamics under both applied creep and recovery. The data show a strong connection between the microstructural dynamics and the acquisition of unrecoverable strain. By comparing this relationship to that predicted from homogeneous, affine shearing, we find that the yielding transition in concentrated colloidal systems is highly heterogeneous on the microstructural level.
