毛细管冷凝
毛细管作用
湿度
弯月面
粘附
原子力显微镜
冷凝
单层
复合材料
材料科学
化学
硅
化学物理
纳米技术
吸附
毛细管压力
热力学
光学
多孔介质
物理化学
物理
多孔性
有机化学
入射(几何)
作者
Xudong Xiao,Linmao Qian
出处
期刊:Langmuir
[American Chemical Society]
日期:2000-09-13
卷期号:16 (21): 8153-8158
被引量:432
摘要
Due to the strong capillary condensation, the adhesion force between a Si3N4 atomic force microscope (AFM) tip and silicon oxide was observed to first increase and then decrease with an increase of humidity. In contrast, due to weak capillary condensation, the adhesion force between the AFM tip and the N-octadecyltrimethoxysilane (OTE, CH3(CH2)17Si(OCH2CH3)3) self-assembled monolayer (SAM) was found to be almost independent of humidity. It was found that the formulation commonly used for macroscopic objects fails to explain our data. Using an accurate formulation and an assumed tip shape, we can explain the observed decrease of adhesion for SiO2 at high humidity as being due to the decreased capillary pressure force when the dimension of the meniscus becomes comparable with the tip size. However, the observed late onset of adhesion of SiO2 cannot be understood within the framework of the classical continuum theory. We attribute this late onset to the properties of an ultrathin water film at molecular thickness. The new formulation predicts a vanishing water meniscus between the AFM tip and OTE over the entire humidity range and can also fully account for the humidity-independent adhesion results for OTE.
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