I Bought a Kg of ZnS:Ag from China

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Michael Driscoll
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I Bought a Kg of ZnS:Ag from China

Post by Michael Driscoll »

I bought what I think is P4(?) from Amy, a nice lady in China. It took months and a payment to a third party at a NYC bank account with no hope of getting my money back if I got screwed, and lots of skepticism from my wife.

All the cool guys in my life have trusted me in some manner and I always made it a point to do the right thing when I gave my word in a deal. I can't even remember getting the wrong end of the stick and I'm 70 yo, that's how rare it has been. Since I am a happy and trusting guy by nature, I almost always just believe what people say contrary to my wife's opinion of other people's promises. For example, back in '92 when I was a machine gun dealer, I ordered a MG from a famous guy in Indiana over the phone. Three weeks later it had been xferred and showed up on my doorstep with an invoice inside the cardboard box! I sent him a check the next day. UPS would often leave signature-required items without signing as we live in the country. IMO, he was a cool dude...

So, after about two months and a confiscation by Chinese authorities of the first shipment (and a reshipment only the second time to a company name in addition to my name), I received a kilo of white powder in two semi-sealed thin plastic bags labeled "Resin." I emailed Amy and she said it was labeled the way it would most likely get through and she assured me that it was genuine.

I think it's ZnS:Ag but don't know how to tell for sure.

Can any of you guys tell me what to check to test if it's the right stuff?

I paid about $0.70 per gram by the time it was all done including fees. The wifely scorn and disbelief made it cost about $25.00 a gram... (It really wasn't that bad but she is still not a believer)

Will it glow under beta or alpha? Will it light up from a Am241 smoke detector dot? It glows brilliantly under UV. I think it glows blue but can't remember right now as I got it in mid-January and have been very busy with other interests. I tried some stuck to Scotch Magic Transparent tape and it didn't glow to my eyes which seem to need a lot of light now that I'm old.

So, if it's real then I would probably want to sell some like Richard H. did with his P4 years ago when he was in a similar situation. I don't know how to do it though, as I am real good at buying but rarely sell anything. I am not trying to make money just recoup some of the 950 grams too much that I bought!

I am thinking $1.00 per gram plus postage shipped in a plastic baggie in a padded envelope. I am not good at this.

I would appreciate any advice I can get from you guys.

I should put it in the For Sale forum when I finally do it, right?

Thanks,
Mike Driscoll
Leesburg, Va
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Richard Hull
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Re: I Bought a Kg of ZnS:Ag from China

Post by Richard Hull »

Mike, Back in the 90's I purchased 500 grams of P4 from Bicron direct at 50 cents per gram. Top grade stuff, too.the simplest way to test is to put a bit of the powder spread out real thin on a piece of paper and hang a Am241 source about 1cm from the surface. Do this in total darkness spending at least 15-20 minutes dark eye adapting and you will see a white glow get more and more intense as your eyes adapt.

Obviously electron beams in vacuums will make the stuff glow brilliantly. (white)

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: I Bought a Kg of ZnS:Ag from China

Post by Dennis P Brown »

For someone not at all familiar with P4 (or ZnS:Ag) could one give a few details. I certainly know of the bulk material - ZnS and both its infrared uses and that it has phosphorescence properties with x-rays and electrons. But not really anything when doped with silver. Wiki does mention that Ag doping creates a blue light under x-ray or electrons. But is it useful for other applications for a fusor or is that basically it?
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Richard Hull
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Re: I Bought a Kg of ZnS:Ag from China

Post by Richard Hull »

Mostly used for radiation detection purposes and 100% of old B&W TV screens. (my first source in highschool daze was to smash an old dead B&W TV CRT and scrap the face of the phosphor.

Alpha detection using a PMT face coated with a thin layer of P4 fast phosphor is the key component in a "wipe test" instrument using a 2" diameter pan drawer to detect radon daughter deposits on benches in labs.

I attach an image of my alpha counter by eberline using the above method. The chromed tray must be kept immaculate as alphas from daughters are everywhere in real life. A good clean count drawer closed is 1-2 CPM. Take a 2" paper disk wet with distilled water and take a single 1 meter long wipe on a lab bench and you will get over 1000cpm! Such are the daughters in air. when we used old CRT's, I would wipe one that had been on all day and would get 6,000 cpm on the eberline. After a couple of wipes and careful tray cleaning I would get a no source count of 30 cpm. clean again with alcohol and distilled water and it would be 10 cpm. clean a third time and maybe 8 cpm. At this point you just need to let the tiny amount of daughters decay over a month. Put a 10uCi red hot disk of Cs137 that measured 90,000 cpm on a GM pancake in the tray and you get maybe 3cpm....
Alpha only, remember

Richard Hull
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Great find on e-bay, but had to  up $550
Great find on e-bay, but had to up $550
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Richard Hester
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Re: I Bought a Kg of ZnS:Ag from China

Post by Richard Hester »

Eljen also sells ZnS Ag phosphor. I plan to enquire...
Rex Allers
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Re: I Bought a Kg of ZnS:Ag from China

Post by Rex Allers »

For some ZnS (Ag) general info. I'm attaching a data sheet with an overview.

Forum specific, it has been used layered between plastic attached to a PMT to make fast neutron detectors.
Attaching, also, specs for one commercial version.

And last here is a link (still working tonight) to an amateur assembled version by Doug Coulter (RIP).
http://www.coultersmithing.com/forums/v ... f=11&t=502
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Alex Aitken
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Re: I Bought a Kg of ZnS:Ag from China

Post by Alex Aitken »

If it glows blue under UV and has a very fast decay then what you have is probably right. A small amount of long persistence phosphorescence might also be normal, can anyone comment?

Be aware the green phosphor, I forget if it's Cu or Mn, it might even be a rare earth, is much more visible to the human eye, so it's brighter for a given activity of alpha, and you can see individual flashes with a lens. Blue is harder for the eye to see, and also to focus on, but much better for bi-alkali photomultipliers.

I bought an alpha screen from ebay a few months ago and I can't remember if it's blue or green but I only got a very general faint glow from a 1uCi alpha source even when very close. I had better results from pigment from glow in the dark paint 10+ years ago, which I poured as a powder and then pressed flat. That may help your test if you also have a weak source.
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Richard Hull
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Re: I Bought a Kg of ZnS:Ag from China

Post by Richard Hull »

The Cu activator is the classic green. Easy to see but has a longish flash that is not great for fast count PMT work. Mn and Eu are also activators for ZnS.

The ZnS:Cu is a light green powder that was used in all radium clock and watch dials. Both the senior Becquerel and his son were renown chemists specializing in phosphor chemistry. The son was the one who discovered radioactivity. Alas, he did not follow up on it, turning further work over to the Curries. They were quickly joined by English and German chemists in the late 1890s and early 1900s.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Richard Hester
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Re: I Bought a Kg of ZnS:Ag from China

Post by Richard Hester »

Just as I side note, I made a rough scintillation screen out of a mix of vac-seal dusted with ZnS:Ag phosphor. I stared at it for ages with dark-adapted eyes and an alpha source and never saw anything. Just on a whim, I flashed the screen with a blue LED source I had on hand (one of those little pocket "squeeze" LED lights), and voila! It lit up like a little pocket universe when hit by an alpha source - fascinating...
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