Supercritical CO2 does not help visualize ionizing radiation

I tried to build a cloud chamber with supercritical CO2, thinking that ionizing radiation (alpha particles) would cause localized condensation of the CO2 at the point where the fluid is coming out of the supercritical state. It didn't work, unfortunately. I tested this idea with the americium-241 source from a smoke detector. I will continue experimenting with CO2 ionization chambers, and it might be possible to visualize the particles with superheated liquid CO2.

A helpful commenter pointed out that alpha particles will not travel very far in a fluid as dense as liquid CO2, so I will try again with a beta emitter.

Supercritical drying chamber for aerogel production

I built a pressure chamber from 2" pipe fittings and 1/8" brass valves to contain supercritical CO2 for drying applications. One project is to try aerogel production which generally requires that solvent be removed via supercritical drying. Normal evaporation would deform the aerogel structure as the surface tension of the solvent pulls the gel's structure tighter together and makes it dense. Since supercritical fluids have gaseous properties, they can diffuse out through the gel without affecting the structure the way that a liquid would.

Liquid lens video

Repost for new video on liquid lenses:



This is a project that I built a few years ago when I learned about liquid lenses. They are quite useful for optical paths with small diameters.

http://www.supertex.com/pdf/datasheets/HV892.pdf

http://varioptic.com/en/products.html

http://benkrasnow.blogspot.com/2009/07/experimenting-with-liquid-lens.html

Microstepping a stepper motor with the SLA7062

Stepper motors can be made to rotate more smoothly by providing simulated sine waves. The SLA7062 chip uses internal PWM to provide sinusoidal current waveforms to unipolar stepper motors. I have this working fairly well, but the PWM frequency is acoustically apparent and annoying.

How to TIG weld aluminum beverage cans together

I show how to weld aluminum cans together with a cheap import TIG welder. I am not a professional welder, so some of my advice may be unconventional or even wrong, but these methods work well for me. With a 3/32" electrode and large gas lens, I don't have to change the torch setup for nearly any kind of common welding. Let me know if you have any questions or would like me to make more welding videos.

Some things that I have learned:

Don't use pure tungsten electrodes. The new rare-earth blends work very well on nearly all metals.

Sharpen the electrode to a very fine point for low-current welding, and sharpen it like a pencil for higher (eg over 100A) welding.

Keep the electrode balance control electrode negative ("weld") and only shift toward electrode positive ("clean") when absolutely necessary.

The welder's pulse feature turned out to be not as useful as I originally thought. It just seems to complicate things. It's definitely possible to make great welds without it.

Use fat electrodes. Some people claim that using an electrode that is "too large" for the weld current will cause the arc to wander. Nope. Just grind it to a sharp point. Thin electrodes 1/16" and .040" overheat much too easily, and provide no apparent benefit. .040" electrodes are very frustrating.

Use thin filler rod. It's much easier to feed thin rod quickly than feed fat rod slowly. As I mentioned in the video, it's easier to sneak a thin filler rod into the puddle while keeping the torch close to the surface.