核心概念
本文研究了一種由核-殼層結構的吸引粒子組成的軟玻璃體系,發現其在停止剪切流動後,由於粒子間逐漸增強的吸引力,導致其黏彈性恢復出現了延遲現象。
統計資料
該乳膠懸浮液的體積分數為 62.5%。
乳膠粒子主要呈雙分散分佈,中心粒徑分別為 1 µm 和 10 µm。
黏彈性模量在停止預剪切後約 800 秒後開始急劇增加,冪律指數約為 4.6。
所有記錄的黏彈性譜都可以通過分數 Kelvin-Voigt (FKV) 模型很好地擬合,其中 α = 0.33。
頻率尺度 ω0 隨時間增加,直到 t = tc,之後保持恆定,ω0 ≃ω∗
0 = 261 rad/s。
時間 tc 隨溫度呈 Arrhenius 關係,活化能 U ≃110 kJ/mol。
屈服應力 σy 與低變形時測得的彈性模量 G′ 呈線性比例關係。
引述
"These results depict an original scenario for the delayed recovery involving a time-dependent interaction potential in which attractive hydrophobic forces are only activated when neighboring particles deform their polymer shell and come in close contact."
"This time-connectivity superposition principle is robustly verified at four other temperatures, namely 10, 15, 20, and 30◦C."
"These results point to a microscopic scenario where the anisotropy of the contact network, frozen at flow cessation, plays a key role, and only particles in close contact form cohesive bonds, whose growing number accounts for the delayed recovery."