Scanning Electron Microscopy Techniques and Their Application to Failure Analysis of Brittle Materials

Abstract

The applicability of scanning electron microscopy (SEM) to failure analysis of glasses, glass ceramics, and polycrystalline ceramic materials is presented. The principle electron operational modes include the secondary electron mode and the backscattered electron mode, where the traditional backscattered electron image obtained from a negatively biased Everhart-Thornley detector is compared with the topographical and compositional backscattered electron images obtained from the newer solid-state backscattered electron detectors. Both the energy-dispersive and wavelength-dispersive X-ray analysis modes and their relation to failure analysis are presented. The principles of fracture mechanics are combined with the fracture surface analysis to illustrate the correlation between the fracture surface features and fracture mechanics. Examples of phase-separated glasses will show the ability to determine the propagation path with respect to the phase-separated regions. Glass ceramic fracture toughness samples will be used to illustrate the ability to observe the microstructure and fracture features independently using backscattered electron imaging techniques. Ceramic samples will be used to show the applicability of determining failure mode (transgranular versus intergranular) as well as interaction with twinning and second phases.