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題名 | Fractal Dimension of Colloidal Aggregates by Rheological Measurements: A Pioneer Study=以黏彈測量求取膠體分散液凝集/凝膠化的碎化維度值 |
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作者 | 徐善慧; | 書刊名 | 界面科學會誌 |
卷期 | 21:1 1998.04[民87.04] |
頁次 | 頁11-16 |
分類號 | 496 |
關鍵詞 | 碎化維度; 滲透學說; 簇間凝集; 黏彈測量; Fractal dimension; Percolation; Cluster-cluster aggregation; Rheological measurement; |
語文 | 英文(English) |
中文摘要 | 雖然用溶膠-凝膠相轉變時的黏彈測量來取代光散射實驗,以求取凝膠的碎形維度、並月以探討凝膠化過程的方法已相當普遍,但膠體的凝集現象目前尚不能以黏彈測量法獲得,故全仰賴光散射實驗來分析凝集的碎形維度與機制。本研究首先選用一特定膠體凝集系統 (純黃豆蛋白質分散液 ),此系統凝集的產物恰好也是凝膠。經由凝膠黏彈理論推導出的碎形維度 (~1.21) 較接近膠體的簇間凝集模型 (cluster-cluster aggregation) 之預測值 (範圍 ~1.20-2.70),而與模擬凝膠的浸透學說所預測的碎形維度值 (~2.5) 相去甚遠;接著測試於另一膠體系統 (聚異丙基丙醯胺水溶液 ) 亦得到與前一系統類似之結果。 因此推測:(1) 膠體凝集所形成的凝膠較適合以膠體之凝集理論來模擬;(2) 用黏彈測量來研究膠體的碎形結構與凝集機制有其發展空間。 |
英文摘要 | Rheological measurements have been used frequently to characterize the fractal dimension of the gelation systems but not the colloidal systems. The gelation of a dispersion (soy protein isolates, SPI) were studied previously by oscillatory rheological measurements (Hsu, J. Chin. Colloid & Interface Soc. 1997, 20, 209-214) and a power law scaling of dynamic moduli versus frequency at gel point was found. The scaling exponent (n~0.13) was very different from those observed in most gelation systems near the sol-gel transition (n~0.67, which can be modeled by the percolation theory). In the current paper, a theoretical argument was presented and employed to obtain the fractal dimension d=1.21 for the SPI aggregates/gels. This low fractal dimension (in comparison to d=2.5 for percolation) was reproduced in poly (N-isopropylacrylamide), and was attributed to the aggregation process, described by the cluster-cluster aggregation mechanism. From the pioneer study, rheological measurement seems to offer an option other than light scattering for use in the fractal analysis of colloids. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。