Conductive Atomic Force Microscopy to Shed New Light on Surface Electrical Trees

Greenhouse gas emission reduction is underway worldwide to mitigate the effects of global warming. Among the new initiatives, electrification of passenger airplanes could yield enormous economic and environmental benefits although a few key technology barriers remain. One main challenge is related to the insulation system. This is because insulation systems required for electric aircraft will need to withstand higher local electric fields and higher temperatures. Unfortunately, all polymeric insulation systems are subject to an aging degradation mechanism called electrical treeing, which can lead to electrical breakdown. The defect is exacerbated in areas of local high field, making it a crucial issue to understand in aircraft insulation. While this mode of tree-aging has been studied for centuries, the mechanism has been debated in the literature. Using new characterization techniques to shed new light on parts of the electrical treeing mechanism is key to new understanding that can lead to mitigation solution. One such new characterization technique is conductive atomic force microscopy (c-AFM). By using a conductive tip on the AFM, the electrical tree can be studied with respect to the electrical conductance of the interior walls and their speculated contribution to electrical tree propagation. This work used c-AFM to study an electrical tree on the surface of an insulation material to establish a baseline procedure in using this technique to study the walls of electrical trees. It was found that the c-AFM can provide conductivity results within and around an electrical tree.