Analytic Studies Using SEM and FESEM

by Josh Biggs in Tech on 29th June 2020

Scanning electron microscopy (SEM) is often used when you need to perform an analytic study or failure analysis for an object or product. SEM allows for high-resolution magnification of surfaces and provides a depth of field that is over one hundred times that of comparable light microscopy. When combined with energy dispersive x-ray spectrometer (EDS) readings, it’s possible to obtain both qualitative and quantitative information about the chemical composition of the object being studied.

The Field Emission Scanning Electron Microscope (FESEM) provides information similar to the SEM, but allows a much enhanced resolution and covers a broader energy spectrum. Together, these devices allow scientists and engineers to do in-depth analyses that covers broad topics ranging from consumer safety at contaminated sites to nutrition and health information about food. These tools are also of great value when studying catastrophic failure of structures that were built using concrete, steel and other materials.

Lead in the Soil Near the Golden Gate Bridge

The iconic Golden Gate Bridge linking San Francisco and Marin County was built during the 1930’s. At the time it was constructed it was painted with two lead-based paints, one a red primer and the other a top coat. Lead was later recognized as a hazard and in 1965 a project began to remove the lead paint and replace it with a zinc-based coatings.

Unfortunately, initial soil samples taken from under the bridge showed lead content that was above acceptable levels. The source of the lead could have been the original paint or it could have been caused by accumulations from leaded gasoline that was in use for many years. Scientists were called in to do a chemical analysis using SEM-EDS and were able to pinpoint minutes flecks of paint mixed in with grains of sand and quartz. The chemical profile and layers of the minute paint flecks matched samples from the bridge and it became clear that the lead in the soil originated with the Golden Gate Bridge.

Studying Probiotics on Pan Bread

Probiotics are live organisms that help with our digestive health and companies are very interested in discovering innovative ways to include probiotics in their food products. One idea being studied was to create an edible film that would act as a carrier layer for probiotics applied to the outside crust of pan bread. This study was necessary because probiotics can degrade during production processes due to mechanical, heat and other stresses.

Bu using a SEM, technicians were able to study the probiotics and the edible films and chart any degradations discovered due to changes in drying conditions or composition. The SEM study determined that variances in drying conditions did not harm the probiotics and that they were intact within the edible layer applied to the bread. It was noted that the edible film did not hurt the bread crust and that a slightly thicker film offered even better probiotic protection.

Developing Composites Based on Bamboo Fiber

Engineers were interested in studying bamboo as a natural fiber for creating composites to be used in construction. By mechanically rolling and untwining the bamboo, the fiber developers hoped to fracture the bamboo fibers so that they could be made stronger by applying a resin to them. The process of breaking down the fibers, called brooming, would allow developers to make a much stronger bamboo product.

By using an FESEM, scientists were able to examine the bamboo fibers that were rolled and untwined using a mechanical process. They observed that this process literally smashed the cellular structure of the bamboo and actually created microfractures between fibers. This allowed for the resin to be immersed into them and thus created a much stronger bond between fiber and resin.

If you need to do an in-depth study of material compositions or perform a failure analysis, then SEM and FESEM devices can provide the scientific answers you are seeking. When combined with EDS, they give valuable insights into both the material composition and elemental makeup of the materials being studied.

Categories: Tech