We mentioned a recent paper that examined silicon/carbon fibers
for use in batteries. Shown above is a TEM image from the paper.
From it you can tell the fibers are essentially hollow carbon
fibers with a layer of silicon around the outside edge.
Transmission electron microscopes (TEMs) work by shooting a beam
of electrons through a sample. The sample has to be quite thin
to let the electrons through, but since these fibers are around
100 nm thick that is fine. The important thing is that the image
is made with electrons. This is different than the sort of
images you’re used to, such as those made with cameras, regular
microscopes, or even your eyes: all of those images are made by
light. Electrons have a smaller wavelength than light, and so
electron microscopes work at extremely high resolution: in some
cases you can make out individual atoms with them. Why would
anyone care about silicon-coated nano-fibers? Because lithium
ions can be stored inside silicon, and that makes these fibers
well-suited to storin