Scanning Electron Microscopy

Hi Everybody,

Most of our blog posts have been about fun things to do outside of school; this post will be about one of the many exciting courses offered at New Mexico Tech. This semester I am taking Materials Engineering 483, Scanning Electron Microscopy. This course is all about teaching students the proper way to use a Scanning Electron Microscope (SEM).

SEM is a microscope that uses electrons instead of light to form an image. The microscope uses an electron gun, a device that runs current through a tungsten filament until the filament emits electrons. This beam of electrons is then sent down a column of apertures, micrometer sized openings  in a metal sheet, to narrow the beam and lenses to control the SEM DIAGRAMbeam spreading . The SEM lenses are actually electromagnets instead of shaped glass like light microscopes. The lenses create magnetic fields to focus the electrons and keep them on the right path. The electron beam then hits the sample where some really fun science happens and electrons are bounced off the sample or replace electrons in the atom and emit a characteristic X-ray. These electrons are collected by different detectors and an image is formed where intensity of the signal, the amount of electrons collected, is transformed to a black and white scale, lighter areas mean more electrons. The characteristic x-rays are used to identify individual elements within a sample.

In the SEM course students learn all about how the SEM works with the ultimate goal of the students using the microscope on a personal research project throughout the course along with completing a couple of assigned lab. The images below are from my first assigned lab, we were required to image an eggshell and a metal fracture surface. My group chose a broken support piece from a jet engine.

Jet Engine Fracture 25x

The eggshell image surprises most people when they see the structure of what we see as a smooth shell.

Eggshell 700x

My personal research project for the course is analyzing a chondrite meteorite found about 20 miles south of Socorro for a materials engineering professor that really wants to see its structure and what elements are present. Not for any of his research but because like so many of us he’s a little nerdy… okay he’s pretty nerdy and thinks its gonna be something really cool to look at on a micron scale. The SEM course is unique at NMT because it is open to anyone that has a project they need to use the SEM and the class has its own funding to allow the students free use of the microscope instead of being charged ~$100/hour like a private company would. This course is just one of the many opportunities to gain valuable researching experience with an instrument that usually costs hundreds of thousands of dollars available to NMT students.

Hopefully y’all learned a little from this, until next time,




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