Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 3700 O'Hara Street, Pittsburgh, Pennsylvania 15261, United States.
Department of Mechanical Engineering, University of California-Merced, 5200 North Lake Road, Merced, California 95343, United States.
Nano Lett. 2022 Jul 27;22(14):5954-5960. doi: 10.1021/acs.nanolett.2c02016. Epub 2022 Jul 6.
The adhesion between nanoscale components has been shown to increase with applied load, contradicting well-established mechanics models. Here, we use transmission electron microscopy and atomistic simulations to reveal the underlying mechanism for this increase as a change in the mode of separation. Analyzing 135 nanoscale adhesion tests on technologically relevant materials of anatase TiO, silicon, and diamond, we demonstrate a transition from fracture-controlled to strength-controlled separation. When fracture models are incorrectly applied, they yield a 7-fold increase in work of adhesion; however, we show that the work of adhesion is unchanged with loading. Instead, the nanoscale adhesion is governed by the product of adhesive strength and contact area; the pressure dependence of adhesion arises because contact area increases with applied load. By revealing the mechanism of separation for loaded nanoscale contacts, these findings provide guidance for tailoring adhesion in applications from nanoprobe-based manufacturing to nanoparticle catalysts.
纳米级组件之间的粘附力已被证明随所施加的负载而增加，这与成熟的力学模型相矛盾。在这里，我们使用透射电子显微镜和原子模拟来揭示这种增加的潜在机制，即分离模式的改变。通过分析对锐钛矿 TiO2、硅和金刚石等技术相关材料的 135 个纳米级粘附测试，我们证明了从断裂控制到强度控制分离的转变。当错误地应用断裂模型时，它们会导致粘附功增加 7 倍；然而，我们表明，粘附功随载荷不变。相反，纳米级粘附受粘附强度和接触面积的乘积控制；粘附的压力依赖性是因为接触面积随施加的负载而增加。通过揭示加载纳米级接触分离的机制，这些发现为从基于纳米探针的制造到纳米颗粒催化剂的应用中调整粘附力提供了指导。
