Aluminum electrophorescence display attmepts, using 6061-T6 in saturated borax solution with a half wave rectified 'signal' putting the aluminum/stainless diode in reverse bias.
There are apparently two different modes of this Al diode in reverse bias, the
first (in this case) is the glowing phase which works up to about 370 volts,
then some kind of breakdown discharge starts all over the aluminum surface, its
a percussive random bright pinpoints affair with blue/violet sparkles
gradually turning to "sodium orange" over time. Note that the brightness of
smaller plates of possibly different Al alloys glow much better than the 6061
shown here. This percussive sparkly phase uses a lot of current (200ma)
whereas the glowing bit uses more like 10ma.
The leakage current in reverse conduction with at 50ohm load (lightbulb) is only 2ma at 186vpeaks.
Putting AC through the diode, causes the aluminum to electrolyze, and the
coating to 'improve' the reverse breakdown voltage went up to about 380volts
before the sparklies started after doing this.
I'm noticing here that the alloys of Aluminum that block most of the
current in the reverse direction do not work well as displays and those that
work well as displays are a little leakier, no idea why yet. (I mean no idea
why some aluminum alloys work better than others, I understand energy for the
electrophoresis has to come from somewhere...)
2024 Al with 2-6% copper glows brightly 6061 hardly at all.
a 8 oz mason jar with 36 in^2 Al (2" pipe 2.75" high) makes a really good diode.
To drop the no load power consumption of these diodes 3 sugar packets in one 8oz
diode will cut the no-load power (with 100vdc out) from 18 watts to 1-2 watts (some of this power was
because the aluminum plates are so big.) In addition at full power the efficiency
goes from somewhere around 34% to 44%
304 stainless rusts too quickly
24 tsp Baking Soda/gal. seems about right.
Ti cathode seems to limit the current way too much and prevents proper diode operation?
Al-Ti doesn't work well Ta-Ti doesn't work well.
Al-Stainless seems to work the best.
Al-Pb rusts red too quickly.
Best ratio of Al-SS diode dc out vs ac in is at 85vac in. 1.33* vout, up to 100vac in (slightly worse?)
The effects of heating, I fully expect this to follow the laws of
thermodynamics just haven't crunched these crude numbers yet.
In sparkly mode, this uses too much current to be a useful display, but
its the only one photographable by me.