AFM Studies on Liquid Superlubricity between Silica Surfaces Achieved with Surfactant Micelles

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• 作者：Jinjin Li ; Chenhui Zhang ; Peng Cheng ; Xinchun Chen ; Weiqi Wang ; Jianbin Luo
• 刊名：Langmuir
• 出版年：2016
• 出版时间：June 7, 2016
• 年：2016
• 卷：32
• 期：22
• 页码：5593-5599
• 全文大小：435K
• 年卷期：0
• ISSN：1520-5827

文摘

By using atomic force microscopy (AFM), we showed that the liquid superlubricity with a superlow friction coefficient of 0.0007 can be achieved between two silica surfaces lubricated by hexadecyltrimethylammonium bromide (C₁₆TAB) solution. There exists a critical load that the lubrication state translates from superlow friction to high friction reversibly. To analyze the superlow friction mechanism and the factors influencing the critical load, we used AFM to measure the structure of adsorbed C₁₆TAB molecules and the normal force between two silica surfaces. Experimental results indicate that the C₁₆TAB molecules are firmly adsorbed on the two silica surfaces by electrostatic interaction, forming cylinder-like micelles. Meanwhile, the positively charged headgroups exposed to solution produce the hydration and double layer repulsion to bear the applied load. By controlling the concentration of C₁₆TAB solution, it is confirmed that the critical load of superlow friction is determined by the maximal normal force produced by the hydration layer. Finally, the superlow friction mechanism was proposed that the adsorbed micellar layer forms the hydration layer, making the two friction surfaces be in the repulsive region and meanwhile providing excellent fluidity without adhesion between micelles.