Nano-tribology at atom-flat surfaces

为了了解原子水平上的摩擦，使用定义良好的原子平面晶面测量了纳米级和毫米级的摩擦系数。分别用碱金属卤化物表面和方解石表面研究了摩擦各向异性和不对称性。为了从不可解理的晶面制备原子平面，人们尝试了各种溶液处理方法。NaC_1(110)、(111)、(113)和(120)晶面局部变得原子平坦。方解石晶面中，(0001)和{01-16}晶面经固溶处理后有稳定的迹象。给出了晶面稳定的原子模型。在NaCl(110)面上，摩擦力的微观测量清楚地检测到预期的摩擦各向异性。在NaCl(111)极性表面也没有检测到各向异性。可以直观地解释纳米尺度上的摩擦各向异性。对相对湿度的依赖关系也进行了研究。碱卤化物冲浪…的摩擦测量另一方面，在毫米尺度上更多的王牌给出了挑战简单解释的结果。在方解石(10-14)表面也进行了毫米尺度的摩擦测量，显示出明显的纳米尺度的摩擦不对称。根据扫描方向的不对称性在更大的尺度上被清楚地检测到。然而，与纳米尺度相比，得到了相反的结果。在施加更大的法向载荷的情况下，对表面进行了磨损轨迹分析。用扫描电子显微镜和原子力显微镜观察径迹，发现在(0001)和{10-14)表面有滑移作用。通过这些滑动面的存在，可以更容易地理解毫米尺度上的摩擦不对称和各向异性。在这个尺度上，与纳米尺度相比，压力施加在更大的区域上。用化学键作为质量-弹簧系统来解释纳米尺度的非对称性模型不适用于毫米尺度，并研究了类玻璃碳(GLC)这一候选的自润滑材料的摩擦性能。2000℃或以上的热处理。作为一种实用材料，摄氏度足以使表面石墨化。通过更高的温度处理，GLC在顶层磨损后保持了实用的摩擦范围。研究了呋喃树脂衍生塑料添加碳纳米纤维后的表面结构和摩擦性能。通过用刀片铺开树脂，纤维平铺在层状样品中，尽管是随机取向的。在样品处测量的摩擦各向异性是由基质聚合物沿扩散方向的取向解释的。随着纤维含量的增加，复合材料的摩擦系数先增大后减小，热处理温度为2000℃。铯的表面最平坦。2800℃时纤维结构消失。摄氏度。较少

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