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Wire Yttria coating electrophoresis

Posted: Mon Jun 12, 2017 1:38 pm
by Jeroen Vriesman
Hi all,

Some preliminary experiments with yttria coating on tungsten:

The result on the picture uses:
a) an yttria colloid (10nm particles, water + acetic acid)
b) a graphite anode (so we don't get any metallic contamination in the colloid, just Kolbe electrolysis)
c) a 2% duty cycle -150V, 5A electrophoresis signal for about 300 seconds

We didn't do any sintering yet, but the layer doesn't fall off easily, so that's good, we will do some sintering en emission tests soon.

We do see one problem, the yttria layer is not smooth, this is because of the H2 bubbles forming during the process.

So, next we will try introducing more movement en vibration during the process, we tried with a pager motor, but that wasn't enough.

Question 1:
Does anyone here know a surfactant which would loosen the H2 bubbles from the cathode?

Question 2:
We are using tungsten now, but would anyone here know a good source of iridium or rhenium wire/ribbon?

Re: Wire Yttria coating electrophoresis

Posted: Mon Jun 12, 2017 3:30 pm
by Dennis P Brown
Could you try a slight vacuum to enlarge the bubbles so that more buoyant force results?

Re: Wire Yttria coating electrophoresis

Posted: Mon Jun 12, 2017 5:15 pm
by Roberto Ferrari
Hi Jeroen

For wires check http://www.sisweb.com/

What about depositing a Y carbonate, decomposing it later under vacuum, as the classical procedure for coating oxide cathodes?

Regards

Roberto

Re: Wire Yttria coating electrophoresis

Posted: Mon Jun 12, 2017 9:20 pm
by Jerry Biehler
Oh, I would be interested in knowing how you did the yttrium coating. My RGA uses yttria coated filaments and they are incredibly expensive.

Re: Wire Yttria coating electrophoresis

Posted: Tue Jun 13, 2017 9:07 am
by Jeroen Vriesman
Dennis: I think vacuum would just make more bubbles.

Roberto: thanks, I did know sisweb is selling it, but they don't have any prices on their site, bit afraid of the "request pricing", but I will ask them.

Jerry: the basic procedure is in this post, we don have more for now. But as soon as we have "proven endurance and emission" I will post a more detailed version.
Attached is a picture of our setup. (very simple, mosfet switch, 150V, grafite anode).
We used this water based colloid: http://www.nyacol.com/products/yttrium/

Re: Wire Yttria coating electrophoresis

Posted: Tue Jun 13, 2017 3:03 pm
by Roberto Ferrari
Jeroen
SIS domestic prices are approx 100 dollars for 10 feet W/Re (0.0132").
But international requests may be charged double than the domestic price.

Re: Wire Yttria coating electrophoresis

Posted: Fri Jun 16, 2017 11:16 am
by Jeroen Vriesman
Roberto, W/Re is indeed not that expensive usually.

But (as far as I understand), I would need pure rhenium wire.
The "enemy" is the tungsten-water cycle. Does tungsten-rhenium also suffer from this problem?

This shows teh emission of yttria coated pure rhenium:
http://www.sisweb.com/referenc/applnote/app-92.htm

Re: Wire Yttria coating electrophoresis

Posted: Fri Jun 16, 2017 12:54 pm
by Roberto Ferrari
Jeroen

This paper states that rhenium resists well the water cycle.

Gordon B. Gaines,
Chester T. Sims,
and Robert I. Jaffee

The Behavior of Rhenium in Electron Tube Environments

J. Electrochem. Soc. 1959 106(10): 881-885.

Even tungsten COATED with rhenium.

Re: Wire Yttria coating electrophoresis

Posted: Sat Jun 17, 2017 4:37 pm
by Jeroen Vriesman
Roberto,

thank you, that was exactly what I was looking for, I was thinking about electroplating tungsten with rhenium. Just don't know how yet...

Re: Wire Yttria coating electrophoresis

Posted: Sat Jun 17, 2017 5:47 pm
by Roberto Ferrari
Jeroen

Think this will help you:

Electrodeposition of rhenium on tungsten hot plate used in Q plasma source
P. J. Paris
Citation: Review of Scientific Instruments 60, 2802 (1989); doi: 10.1063/1.1140664