Poly-12-hydroxystearic acid (PHSA) is widely used as a coating on colloidal spheres to provide a "hardsphere-type" interaction. These hard spheres have been widely used in fundamental studies of nucleation, crystallization, and glass formation. Most authors escribe the interaction as "nearly" hard sphere. In this paper we directly measure this interaction, using layers of PHSA adsorbed onto mica sheets in a surfaces force apparatus. We find that the layers, in appropriate solvents, have no long-range interaction. When the solvent is decahydronaphthalene (decalin), the repulsion rises from zero to the maximum measurable over a distance range of 15-20nm. The data is converted to equivalent forces between spheres of different diameters, and modeled using a hard core potential. Using zeroth-order perturbation theory and computer simulation, we demonstrate that the equation of state does not deviate from that of a perfect hard-sphere system under any relevant experimental conditions.

For the friction measurements with AFM/FFM, usually the relative values of friction signal can be obtained. In order to compare the micro-tribological properties of different samples, mica is often used as an reference sample for friction measurement. However, due to the friction force of new cleaved mica surface is unstable, it is urged to systematically investigate the tribological properties of mica to design the experimental rules of the reference sample mica for friction measurements. Experimental results show that the friction of mica varies with the cleaving time, humidity and surface state of tip. The friction measured with different tips on mica varies in the range of

使用原子力/摩擦力显微镜在5%-9%的相对湿度范围，研究了二氧化硅和二氧化硅基体上十八烷基三甲氧基硅烷自组装膜（简称OTEsAM/siO2）表面摩擦力和粘着力随湿度的变化规律实验表明叫OTE SAM/SiO2，不仅能明显改善二氧化硅基体表面的摩擦性能，而且在200nN（接触区HPnz压力约为0.8GPa）的载荷条件下表现出良好的抗磨性能由于强的亲水性，二氧化硅表面的摩擦力随湿度的增大先逐渐增大，然后急剧减小相反，OTE SAM/SiO2由于其良好的斥水性，表面的摩擦力在高湿度条件下略有减小，它可望成为微型机械和高速磁记录系统中较为理想的边界润滑剂。

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 acroscopic 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 omparable with the tip size. However, theobserved 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.

使用原子力/摩擦力显微镜，在5%-9%相对湿度范围，研究了二氧化硅和二氧化硅基体上十八烷基三甲氧基硅烷自组装膜（简称OTEsAM/siO2）表面粘着力随湿度的变化规律。实验表明，二氧化硅表面的粘着力随湿度的增大先逐渐增大，然后急剧减小相反，叫OTE SAM/SiO2由于其良好的斥水性，表面的粘着力随湿度的增大基本不变着重从基本界面力，即表面张力、范德瓦耳斯力和基本键合力的形成与变化，分析了二氧化硅表面粘着力随湿度的增大先增后减的原因，探讨了粘着力的产生机理。