Beryllium Oxide vs Alumina - is there a way to identify? - Page 1
Forum section: electronics / general

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2015, 05:46:26 am
content: I bought a second bag (400) of the glass vacuum feed-through insulators. See ebay 251041737116.The seller is in Estonia, and has a nice practice of putting other little gifts in the box. This time I got a scarf, 50 extra feed-throughs, and... what's described on the customs form as "sharpening stone".Only it isn't, It's a thin ceramic insulator sheet. Purple-pinkish color, and it feels very heat conductive to the fingertips.Well, that's fine. Presumably the seller has some piles of old USSR tech supplies, and he really thinks this is a sharpening stone.But I think there's a fairly high chance I'm holding a piece of the dreaded BeO. Given the color and origins.Assuming I don't abrade it, I don't mind having it. It's now in a sealed ziplock bag.Does anyone know of a way to tell the difference, with certainty? By some means that doesn't involve doing anything to it that could wear even microscopic particles off. I like being alive, even if I do have a bad flu still.For one thing, I imagine the seller has a lot of these, and if it's BeO I'd better warn him about how dangerous they are.But I don't want to freak out unnecessarily. If it's AlO then it's a nice useful high voltage thermal pad.

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2015, 06:38:07 am
content: Quote from: blueskull on October 20, 2015, 06:21:49 amYes, I know. I'll be keeping it even if it is BeO.What I'm concerned about is the seller posting them around the world as 'sharpening stones'. Because you know what that means people would do with them.

author: coppice
author_rank: Super Contributor
timestamp: October 20, 2015, 06:39:11 am
content: Quote from: blueskull on October 20, 2015, 06:21:49 amThey are still actively used in most people's kitchens, right next to the food.

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2015, 07:06:53 am
content: The seller replied to me:QuoteOK. But I still want to find a way to verify which it really is. Good to know.Incidentally Alumina does make good sharpening stones - it's what they are actually made of usually. The tops of old large ceramic IC packages (eg early pentium chips) are great for sharpening scalpels, as the grit is so fine.

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2015, 07:11:26 am
content: Quote from: coppice on October 20, 2015, 06:39:11 amIf you mean the antenna stub insulator in magnetrons (microwave ovens) then no, that is Alumina.Same for kitchen knife sharpening stones.Maybe measuring thermal conductivity, or dielectric constant, could differentiate between the materials? But quite difficult to do in practice.Quote from: blueskull on October 20, 2015, 06:42:42 amExcept these reallywerea gift. I only bought the vacuum feed-throughs. Other things were surprises.Actually, he may not know it but the most interesting extra was the few pages of an Estonian newspaper. Garfield in Estonian...Or maybe he does realize.

author: Ian.M
author_rank: Super Contributor
timestamp: October 20, 2015, 07:20:41 am
content: Dielectric constant shouldn't be too tricky. Mike the thickness then use foil plates clamped against the sample using expanded polystyrene blocks and measure the resulting parallel plate capacitor with a good cap meter. Calculate the dielectric constant from the parallel plate capacitor formula and check by repeating the measurements with a known dielectric of approximately the same thickness. Weighing it, calculating the density and comparing with published data for various electrical grade ceramics might also help narrow it down.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 20, 2015, 07:25:46 am
content: Weigh them. Alumina is 4 G/cm3 and BeO is 3 G/cm3. I do not see any other way.

author: rollatorwieltje
author_rank: Unknown
timestamp: October 20, 2015, 08:43:32 am
content: Isn't BeO white? Alumina is pink under certain conditions. Better safe than sorry, but I can't imagine that somebody would dye an insulator the same color as a less harmful substance that's used for the same purpose. Also alumina is actually used as a sharpening stone and other abrasive applications.edit: note to self; refresh page before posting

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2015, 08:47:58 am
content: Quote from: Jeroen3 on October 20, 2015, 07:25:46 amDammit. This led to discovering my little electronic balance is dead. Died the death of "left ni-cad batteries in too long". I didn't even know it contained built-in batteries. Sh*t. I hate ni-cad batteries. Whatever it is they exude (hydrogen ions?) it sure can creep a long way along wires, and diffuse right through PCBs. I don't need batteries in this. Whether the unit is repairable still to be determined.Anyway... The material is 29.95 x 47.90 x 1.98 mm = 2.840518 cm3I'll be back with the weight measured the old fashioned way - precision beam balance.Edit: OK, weight is 10.686 gSo the density is 3.7619 g/cm3Closest to Alumina, so that's probably what it is. Good.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: October 20, 2015, 11:40:13 am
content: Quote from: TerraHertz on October 20, 2015, 08:47:58 amEureka!

author: SeanB
author_rank: Super Contributor
timestamp: October 20, 2015, 06:57:23 pm
content: I have some very expensive knife sharpening stones. $500 each.Before they became sharpening stones they were Ceramus dispensers, but they unfortunately are not drop proof, even in a padded box.The outer borosilicate cylinder shatters, but the inner sintered and ground aluminia piston always emerges unscathed. Sadly I only have the cheaper ones with titanium springs in the non return valves, not the " will handle anything aside from Alien blood and probably even that for a time" versions with platinum springs.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 20, 2015, 09:49:25 pm
content: AFAIK, alumina is always (or almost always) tinted red. Which, incidentally, is done with chromia. So, actually, what you have in your hands there ispolycrystalline ruby. I hope that makes you feel special. Or something.I don't know that beryllia can be tinted in the same way, or as easily. Or as usually.Alumina certainly comes in white flavors, where it would be just as hard to tell apart. But it would be rather expensive for, say, chip resistors to be built on BeO, so, you can more or less assume such things are okay. Examples like your, I suppose, heatsinking plate / sharpening stone (which it should do a good job as, by the way), could go either way, since as mentioned, BeO has been, and still is, pretty popular for high performance applications.If you're still extraordinarily curious (i.e., this isn't just a quick identification test that anyone can do easily or cheaply), you could perhaps take it to the local university. Check their website, find the department heads, and ask some (perhaps geology or chemistry or physics) faculty if you could test a sample on their x-ray or electron beam system (if they have one). Examples: XRF (x-ray fluorescence), SEM (scanning electron microscope), neutron activation, etc. (Any general purpose chemical method, like atomic absorption, mass spectrometry, chromatography or gravimetry, requires a lengthy analysis procedure, so, not exactly a casual "hey what's this thing?" opportunity.) If they like the idea, they'll probably agree just out of mutual curiosity.Tim

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2015, 10:39:07 pm
content: So, given that it's Alumina, and about 2mm thick, these could be quite useful for high voltage power systems.Thinking the seller might have lots of them for cheap (considering he gave one away as a bonus) I checked his store.Yes, he has lots of them. But a bit pricey to buy 100, at US$145http://stores.ebay.com/KALLEB-SPECIAL-WEBSTORE?_trksid=p2047675.l2563Considering typical China-new prices:http://www.aliexpress.com/item/100pcs-lot-20x25x1mm-Alumina-ceramic-pads-thermally-conductive-insulation-sheet-high-temperature-resistant-Heat-Sink/32354843285.html96% Alumina Ceramic substrates, ceramic plate IGBT ceramic heat sink 20*25*1mmUS $39.99 / lot of 150 pieces

author: rs20
author_rank: Super Contributor
timestamp: October 20, 2015, 10:48:26 pm
content: A "simple" test for the detection of Beryllium minerals.I also note that Alumina will react with NaOH to form the soluble sodium aluminate; while it appears the Beryllia is harder to dissolve: "Berrylia dissolves in hot aqueous ammonium bifluoride (NH4HF2) or a solution of hot concentrated sulfuric acid (H2SO4) and ammonium sulfate ((NH4)2SO4)".So in short, I think a strong hot solution of caustic soda will dissolve Alumina but leave Beryllia untouched? I'm literally just reading wikipedia (and "Queensland Alumina Limited") here though, hot caustic soda sounds like something that only professionals should deal with...

author: helius
author_rank: Super Contributor
timestamp: October 20, 2015, 11:32:42 pm
content: Besides dissolving glass and skin, I don't see the problem (lol).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 21, 2015, 04:23:00 am
content: NaOH is very dangerous.It dissolves skin. After brief contact, you'll notice your fingers feel overly dry and chalky. This is because your skin (and, first of all, the oils on your skin) get etched and dissolved, turned to soap. Prolonged contact (like, waiting for CO2 in the air to do something, which is in rather low concentrations remember, despite the rising concentration these days) will destroy your epidermis.Sensitive surfaces,the eyes in particular,are extremely vulnerable. You can be blinded very quickly by the stuff.Wear goggles!Aqueous acid isn't particularly dangerous. I'm not sensitive to it, but people with sensitive or thin skin may have problems. Open skin and sensitive surfaces (most any part of the face) hurts like a mofo, so you'll wash it off before it's much danger.Concentrated sulfuric acid is completely different, because it aggressively dehydrates anything, and gets seriously hot in the process. You want to wear gloves for that.Nitric acid of most commercial concentrations (I think about 50% and up) will nitrate on contact, leaving a yellow spot (and, incidentally, hurting like a mofo also). This eventually sloughs off (I suppose the scab would be flammable... but I also suppose it would smell bad too).Heard the story from a guy who does precious metals refining, he got a drop of nitric in his eye once. Still lucky, but the Dr. said if it were NaOH, he would've surely been wearing an eyepatch instead. (Yep, he ended up with a yellow spot, that eventually sloughed off. Good as new, give or take a lot of discomfort along the way.)Tim

author: rs20
author_rank: Super Contributor
timestamp: October 21, 2015, 04:50:05 am
content: Quote from: blueskull on October 21, 2015, 04:32:55 amEh? H2SO4 gets more and more dilute as it performs its dehydration...