Wire Yttria coating electrophoresis
-
- Posts: 276
- Joined: Mon Feb 07, 2011 4:08 pm
- Real name: Jeroen Vriesman
- Location: Netherlands
- Contact:
Wire Yttria coating electrophoresis
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?
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?
- Dennis P Brown
- Posts: 3187
- Joined: Sun May 20, 2012 10:46 am
- Real name: Dennis Brown
Re: Wire Yttria coating electrophoresis
Could you try a slight vacuum to enlarge the bubbles so that more buoyant force results?
-
- Posts: 364
- Joined: Tue Mar 02, 2004 12:21 pm
- Real name: Roberto Ferrari
- Location: Argentina
- Contact:
Re: Wire Yttria coating electrophoresis
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
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
-
- Posts: 975
- Joined: Tue Nov 24, 2009 3:08 am
- Real name:
- Location: Beaverton, OR
Re: Wire Yttria coating electrophoresis
Oh, I would be interested in knowing how you did the yttrium coating. My RGA uses yttria coated filaments and they are incredibly expensive.
-
- Posts: 276
- Joined: Mon Feb 07, 2011 4:08 pm
- Real name: Jeroen Vriesman
- Location: Netherlands
- Contact:
Re: Wire Yttria coating electrophoresis
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/
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/
-
- Posts: 364
- Joined: Tue Mar 02, 2004 12:21 pm
- Real name: Roberto Ferrari
- Location: Argentina
- Contact:
Re: Wire Yttria coating electrophoresis
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.
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.
-
- Posts: 276
- Joined: Mon Feb 07, 2011 4:08 pm
- Real name: Jeroen Vriesman
- Location: Netherlands
- Contact:
Re: Wire Yttria coating electrophoresis
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
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
-
- Posts: 364
- Joined: Tue Mar 02, 2004 12:21 pm
- Real name: Roberto Ferrari
- Location: Argentina
- Contact:
Re: Wire Yttria coating electrophoresis
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.
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.
-
- Posts: 276
- Joined: Mon Feb 07, 2011 4:08 pm
- Real name: Jeroen Vriesman
- Location: Netherlands
- Contact:
Re: Wire Yttria coating electrophoresis
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...
thank you, that was exactly what I was looking for, I was thinking about electroplating tungsten with rhenium. Just don't know how yet...
-
- Posts: 364
- Joined: Tue Mar 02, 2004 12:21 pm
- Real name: Roberto Ferrari
- Location: Argentina
- Contact:
Re: Wire Yttria coating electrophoresis
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
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
Re: Wire Yttria coating electrophoresis
How much did the Nyacol yttria colloid cost you?
-
- Posts: 147
- Joined: Wed Jun 28, 2006 7:17 pm
- Real name: Silviu Tamasdan
- Location: Connecticut
Re: Wire Yttria coating electrophoresis
I see an unanswered question in the OP that I may field.
I have used surfactants in electrolysis before, and in one case it was precisely for this reason (prevent gas bubble adhesion to avoid pitting).
It was a different application though so take this with a grain of salt.
I used Triton X-100, a nonionic surfactant, at 0.5% concentration. It gave reasonable results. The application was coating of a graphite anode with a layer of lead dioxide. The electrolysis conditions were vastly different (DC 4V, about 800mA for ~20min). The Triton degrades slowly over these conditions so its surfactant properties decrease over time but it should be good enough for runs of up to 1h. I don't know how it would fare under your conditions though.
Another method that I used to deal with bubbles in this particular system was centrifugal force. Essentially the piece to be coated is spun during electrolysis by a small electric motor. I used a 6V 20000rpm motor that I undervolted to 1.5V; this combined with the inertia of the piece+connecting shaft and the friction with the electrolyte resulted in a rotation speed of about 300rpm. That is enough to knock off bubbles as they form. Caution if you use surfactant at the same time as it can lead to a significant amount of foaming.
(edit) Here's a short video that I made during that process.
https://www.dropbox.com/s/lpuqob9fl9ruj ... t.mp4?dl=0
I have used surfactants in electrolysis before, and in one case it was precisely for this reason (prevent gas bubble adhesion to avoid pitting).
It was a different application though so take this with a grain of salt.
I used Triton X-100, a nonionic surfactant, at 0.5% concentration. It gave reasonable results. The application was coating of a graphite anode with a layer of lead dioxide. The electrolysis conditions were vastly different (DC 4V, about 800mA for ~20min). The Triton degrades slowly over these conditions so its surfactant properties decrease over time but it should be good enough for runs of up to 1h. I don't know how it would fare under your conditions though.
Another method that I used to deal with bubbles in this particular system was centrifugal force. Essentially the piece to be coated is spun during electrolysis by a small electric motor. I used a 6V 20000rpm motor that I undervolted to 1.5V; this combined with the inertia of the piece+connecting shaft and the friction with the electrolyte resulted in a rotation speed of about 300rpm. That is enough to knock off bubbles as they form. Caution if you use surfactant at the same time as it can lead to a significant amount of foaming.
(edit) Here's a short video that I made during that process.
https://www.dropbox.com/s/lpuqob9fl9ruj ... t.mp4?dl=0
There _is_ madness to my method.
-
- Posts: 276
- Joined: Mon Feb 07, 2011 4:08 pm
- Real name: Jeroen Vriesman
- Location: Netherlands
- Contact:
Re: Wire Yttria coating electrophoresis
Ian,
I ordered a sample of the yttria colloid.
It was for free.
I ordered a sample of the yttria colloid.
It was for free.