Nano-tribology at atom-flat surfaces

为了理解原子水平上的摩擦，摩擦系数在纳米尺度和毫米尺度上测量，使用定义良好的原子平面晶体面。分别在碱卤化物表面和方解石表面研究了摩擦的各向异性和不对称性。为了从不可切割的晶面中制备原子平面，尝试了各种溶液处理方法。NaC1(110),(111),（113）和（120）表面局部原子平坦。方解石晶面中，（0001）和{01-16}晶面在溶液处理下表现出稳定化的迹象。在NaC1（110）表面，摩擦力的微观测量清楚地检测到预期的摩擦各向异性。在极性NaC1（111）表面也未检测到各向异性。纳米尺度上的摩擦各向异性可以直观地解释。对相对湿度的依赖性也进行了研究。在碱卤化物表面的摩擦测量……另一方面，更多毫米尺度的ace给出了难以简单解释的结果。在方解石（10-14）表面进行了毫米尺度的摩擦测量，显示出纳米尺度上明显的摩擦不对称性。在更大的尺度上，可以清楚地检测到不同扫描方向的不对称性。然而，与纳米尺度相比，得到了相反的结果。通过施加更大的正常载荷，在表面进行磨损轨迹分析。用扫描电子显微镜和原子力显微镜观察轨迹，发现在（0001）和{10-14)表面有滑移作用。毫米尺度的摩擦不对称性和各向异性可以通过这些滑动表面的存在更容易理解。在这个尺度下，与纳米尺度相比，应力被施加在更大的区域上。在纳米尺度上用来解释不对称的化学键质量-弹簧系统模型在毫米尺度上是不适用的。研究了自润滑材料候选材料类玻璃碳（GLC）的摩擦性能。在2000摄氏度或以上的热处理引起表面石墨化，足以作为一种实用材料。通过在更高的温度下处理，GLC在表层磨损后保持了实际的摩擦范围。研究了添加纳米碳纤维的呋喃树脂衍生塑料的表面结构和摩擦性能。通过用刀片铺开树脂，纤维平铺在层流样品中，尽管方向是随机的。在样品上测量的摩擦各向异性可以用基体聚合物沿扩散方向的取向来解释。摩擦系数随纤维含量的增加先增大后减小，在2000℃热处理后表面最平整。纤维结构在2800摄氏度时消失。少

In order to understand friction in the atomic level, frictional coefficients were measured both in nano-scale and in millimeters-Ale using well-defined and atom-flat crystal faces. Frictional anisotropy and asymmetry were studied using alkali halide surfaces, and calcite surfaces, respectively. To prepare atom-flat surfaces out of uncleavable crystal faces, various solution treatments were tried. NaC1(110), (111), (113) and (120) faces became locally atom-flat. Among calcite crystal faces, (0001) and {01-16} faces showed signs of stabilization by solution treatments. Atomic models were given for the stabilization of the crystal facesAt NaC1(110) surface, expected frictional anisotropy was clearly detected in frictional force microscopic measurements. Anisotropy was not detected at polar NaC1(111) surface also as was expected. Frictional anisotropy in nano-scale can be intuitively interpreted. Dependence upon relative humidity was also studied.Friction measurements at alkali halide surf … More aces in millimeter-scale, on the other hand, gave results defying simple interpretation. Friction measurements in millimeter-scale were also performed at calcite (10-14) surface which showed clear frictional asymmetry in nano-scale. Asymmetry depending upon scan directions was clearly detected in the larger scale. However, opposite results were obtained compared to in nano-scale. Wear track analyses were performed at the surface by applying much heavier normal load. Observation of the tracks with scanning electron microscopy and atomic force microscopy revealed slip actions at (0001) and {10-14) surfaces. Frictional asymmetry and anisotropy in millimeter-scales can more easily be understood by the presence of these slip surfaces. In this scale, stresses are applied on much larger areas compared to in nano-scale. The model of chemical bonds as mass-spring systems used in explaining asymmetry in nano-scale is not applicable in millimeter-scale.Frictional properties of glass-like-carbon(GLC), a candidate for self-lubricating material, were also studied. Heat treatments at or above 2000 deg. Celsius caused surface graphitization sufficient as a practical material. By treating at even higher temperature, GLC kept the practical range of friction after wearing off of the top layers.Surface structures and frictional properties were studied with furan-resin-derived plastic added with carbon nano-fibers. By spreading the resin using a blade, the fibers lied flat in laminar samples, although in random orientations. Frictional anisotropy measured at the sample was explained by the orientation of the matrix polymer along the spreading direction. The friction coefficient first increased, then, decreased with increasing the fiber content, Heat treatment at 2000 deg. Celsium gave the flattest surface. Fiber structures were lost at 2800 deg. Celsius. Less