Aero-Gel

[Probeman]

Zack Gainsforth posted this and I thought it worth re-posting here:

I have done quite a bit of imaging of SiO2 aerogel, (not nanocellulose) but some of our imaging approaches may work for you.

To image it in an SEM, I use low voltage, uncoated. Because of the low density of aerogel, the charge balance point is surprisingly high. Our aerogels are especially low density aerogels (about 20 mg/cm3, which for SiO2 is about 99.3% vacuum) and the charge point on most of our aerogels comes in at around 2.1 to 2.2 keV. You can get some very nice images this way. It helps to use a field emitter because of the very fine structure of the fibers, and the fact that you want to keep the current low as well as the voltage.

For sectioning aerogel, we use motorized glass needle cutting: Westphal, A. J., Snead, C., Butterworth, A. L., Graham, G. A., Bradley, J. P., Bajt, S., et al. (2004). Aerogel keystones: Extraction of complete hypervelocity impact events from aerogel collectors. Meteoritics and Planetary Science, 39(, 1375-1386.

This may be a lot of work to set up, but it works very, very well. One thing you can do is cut a 100 micron thick section, flip it on its side, and cut another section a few tens of microns thick. Then you can affix that to a substrate and image it uncoated with high voltage in an SEM. It works because the density is so low the electron beam just goes clean through. (Poor man's TEM.)

Finally, I have gotten images in a TEM, but since I'm not usually studying the aerogel itself (but rather minerals trapped in it) I've never developed a good protocol here. However, it is my experience that epoxy embedding always alters the structure of the aerogel, so you probably will be better off going with some of the other suggestions if the above doesn't work for you.

I concur with Stephan that it is possible to get a good cut with razorblades (though don't drink coffee first -- it will make your hand shake!) And Phil's approach seems sharp too.