flying fish Posted October 22, 2008 Posted October 22, 2008 Thanks! That's kind of what I suspected...the quantity is too low to be much concern. Of course at 1340 C, who knows how quickly it will oxidize (maybe with a "poof") and shooting all the gasses into the operator's face (ok probably not, but I do want to be on the side of caution). And while we are on the topic, does anyone know of a "slippery", refractory material that doesn't oxidize? It seems to be a tough thing to come by. I'm almost wondering what if I sent the graphite off to have to unused, exposed portions coated with SiC. But after all that effort, I might as well just try to find an H2 or vacuum furnace. Yes, I am trying to get APC forum member to do my job for me .
Richtee Posted October 22, 2008 Posted October 22, 2008 Yes, I am trying to get APC forum member to do my job for me . I'm sure yer getting better grades than I ever did, kid ;{)
asilentbob Posted October 22, 2008 Posted October 22, 2008 I have probably spent 5 hours every week on IRC for the past 2 years or so... Not counting when I'm away from the computer and just leaving it on and running... Sure it works, but IMO 30min of Skype is far superior to 30min of IRC. If you have a reducing atmosphere oxidation should be negligible. Right?
Swede Posted October 24, 2008 Posted October 24, 2008 Glass work for the laboratory... While not specifically pyro related, quite a few guys here are into amateur chemistry. I had a need today to cut and shape some old pipettes, and this site has some cool info for the beginner. Enjoy! http://www.ecu.edu/glassblowing/gb.htm
flying fish Posted October 26, 2008 Posted October 26, 2008 If you have a reducing atmosphere oxidation should be negligible. Right? I was just thinking about this again. How would you create a reducing atmosphere (or at least a poor-oxygen environment) without needing to buy a specialized furnace? Could I stick a crucible full of lampblack (or maybe activated carbon) in there to eat up all the oxygen before it can reach my graphite substrate?!?! Or is there a way for me to pump N2 into the chamber...Or just put the whole furnace into a big box (say, our fume hood with the exhaust closed off) and then pump nitrogen directly into that box. The first idea would obviously be the easiest....though I'm not sure if it would work.
oskarchem Posted October 26, 2008 Posted October 26, 2008 You could just burn something inside the furnace, for the combustion to eat up all the oxygen.
flying fish Posted October 26, 2008 Posted October 26, 2008 Yeah, that's where I was going with the lampblack/carbon idea. It has to be something that will last for an hour at 1340 C...but it has to use up enough oxygen to slow the oxidation of the graphite substantially.
mormanman Posted October 27, 2008 Posted October 27, 2008 I thought I would share this with you guys. I found an excellent source of 4" mortars FOR FREE. Guess where? None other than home depot. You know the carpet roles, well they have cardboard tubes inside and guess what they do when they're done with the tubes? They throw them away so they're "mailing tubes" for me. Great find I think.
asilentbob Posted October 27, 2008 Posted October 27, 2008 If its an electric furnace... it would get complicated... If its gas burning... you just shift the fuel/air ratio a bit by adjusting the burner so that the combustion of the gas is less than optimum. Its like adjusting the flame on a bunsen burner so less air gets mixed in with the gas. You might make a bit of soot/lampblack and carbon monoxide... but if its vented away from others it shouldn't really be a problem.
Swede Posted October 27, 2008 Posted October 27, 2008 FF, I've used stainless steel foil for years to protect items in an electric furnace; before that, I used borosillicate glass powder like "Keep-Bryte." But the foil is good stuff, IF you can encase whatever your item is inside of it. It is wrapped and the foil rolled and crimped a bit, forming an enclosure that while not totally leakproof, will do a good job protecting the item. It is also possible to displace most of the air (before sealing) with Nitrogen or Argon. A piece of brown paper inside will consume the O2 that remains or enters. SS foil is best for small objects or containers, but I'll bet it would be possible to seal all sorts of objects.
Bonny Posted October 27, 2008 Posted October 27, 2008 FF, I've used stainless steel foil for years to protect items in an electric furnace; before that, I used borosillicate glass powder like "Keep-Bryte." But the foil is good stuff, IF you can encase whatever your item is inside of it. It is wrapped and the foil rolled and crimped a bit, forming an enclosure that while not totally leakproof, will do a good job protecting the item. It is also possible to displace most of the air (before sealing) with Nitrogen or Argon. A piece of brown paper inside will consume the O2 that remains or enters. SS foil is best for small objects or containers, but I'll bet it would be possible to seal all sorts of objects. I think they did something similar to harden or anneal steels etc...at the machine shop I worked at years ago. The material and some paper was put in a bag (SS I guess) and then the bag was put into the electric oven.
tentacles Posted October 27, 2008 Posted October 27, 2008 Good call, Swede, you can buy this kind of foil at machine suppliers like Enco, McMaster, etc. It's not cheap but it could be reusable if you're careful. There's some good to 1800F and another to 2100F, about $43-48 for a 10"x12' roll.
flying fish Posted October 27, 2008 Posted October 27, 2008 Thanks again for the advice guys. Of course, our operating temperature is going to be 2444F (1340C) for one hour...at which we've seen some pretty nasty things done to stainless steel (I'll see if I can get a picture of it!). But the foil might be worth a try. It will probably burn up, but perhaps protect the graphite for a little while. Heck, I wouldn't even mind if I can't reuse the graphite after one use. Graphite for one run costs a few bucks, and the chips are sold for several $hundred a piece. As long as the graphite substrate stays flat enough to allow to good (thermocompressive) bonding of our microfluidic chips. Pumping N2 in before closing the door sounds like a good idea, but the furnace is not hermetically sealed...at least I don't think it is. I will double check on that. Things just keep getting crazier and crazier at work. I was pulled from my original project to work on this thermocompressive bonding project, and then I was pulled from the thermocompressive bonding thing to try and locate a supplier for another exotic substance that probably doesn't exist.
Swede Posted October 28, 2008 Posted October 28, 2008 Wow, I might have missed it, but I didn't realize the temp was that high. The SS might hang on for a few minutes, but I wouldn't count on it for much. How about an Argon trickle? Create an injection tube from inconel or similar metal (maybe Ti will work), and affix it so it can inject into the furnace. Purge the furnace before heating with a high flow, then taper the flow as the furnace heats. Above 1,000 degrees or so, take the flow down to a very low state, too low to cool the furnace (maybe 1/2 PSI???) but high enough to provide just a bit of positive pressure inside. Most electric furnaces go to only 2,200 F or so, so I'm guessing yours is fairly specialized, expensive, and well made. What is the chamber made of? Mine is a ceramic fiber refractory (not firebrick) and there is a spring-loaded flange on the door that actually does seal pretty well. Any furnace that goes that high better be very well sealed, or the heat might leak and fry the cabinet or electronics. I'm guessing some atmosphere controlled furnaces use a similar overpressure system, as it would be much simpler than actually trying to seal it, and keep it sealed, throughout the cycle. Furnaces need to be able to vent slightly anyhow, so as to expel hot gasses. Interesting conundrum.
flying fish Posted October 28, 2008 Posted October 28, 2008 Darn - I forgot to find out whether the furnace is actually sealed or not. I believe the furnace lining is a refractory fiber board, probably alumina. It's a lab furnace with an 8"x8"x8" chamber, and goes up to 1700C.
Swede Posted October 29, 2008 Posted October 29, 2008 1700C/3,000F is an insanely high temperature for an electric furnace that uses resistance coils. I didn't think there was a resistance element that could create such temps. What brand of furnace is it? Wow, I learned something new today. They DO make high temp electric box furnaces that can do 1,800 degrees C.http://www.sentrotech.com 1900C MoSi2 Heating Element Very interesting. When you open the door to one of those at 3,000 F, the IR radiation must be insane.
flying fish Posted October 29, 2008 Posted October 29, 2008 It is one of the 1700 series Lab furnaces from CM furnace. http://www.cmfurnaces.com/Lab.cfm And yeah, from what I've read heating elements for High Temp furnaces are generally molybdenum disilicide (sounds exotic! I don't even know how to pronounce it.). Our old furnace had SiC heating elements, but it only went to 1000C.
asilentbob Posted October 31, 2008 Posted October 31, 2008 I'd say just try it once without modifications to see if your going to even need to modify it. Ya know, don't fix it if it isn't broken. On a side note, its halloween and I have nothing to do :/. Working on mounting the bucket of my star roller to the shaft... Shouldn't have any problem, but with my luck probably will be off center or something... Going to be a while... Waiting for some wood glue to dry between two layers of C-clamped wood disks. Should probably get some breakfast too huh?
Bonny Posted October 31, 2008 Posted October 31, 2008 Working on mounting the bucket of my star roller to the shaft... Shouldn't have any problem, but with my luck probably will be off center or something... Going to be a while... Waiting for some wood glue to dry between two layers of C-clamped wood disks. If it's a bit off centre it might actually help, by providing some "bumping action" so stars don't stick together.
asilentbob Posted October 31, 2008 Posted October 31, 2008 True, but I could always add a rib or 2 inside the bucket to achieve the same effect. On a side note this desk rolly chair just broke randomly... Need to weld it back together or something...
mike_au Posted November 3, 2008 Posted November 3, 2008 Finished my new mill yesterday. It's a little bit too fast (~100rpm, I was aiming for ~90) and a little louder than I had hoped, but it's a definite improvement over my old one.
The-T Posted November 3, 2008 Posted November 3, 2008 Nice looking mill there. I like the design, it looks neat and simple.
qwezxc12 Posted November 3, 2008 Posted November 3, 2008 Finished my new mill yesterday. It's a little bit too fast (~100rpm, I was aiming for ~90) and a little louder than I had hoped, but it's a definite improvement over my old one. Looks nice. Wondering, though... Looks like clear poly tubing over threaded rod for shafts...Will the poly tubing provide enough grip?Any particular reason to have two drive shafts, rather than one and a idler?
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