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Author: Subject: DIY microwave reactor with integrated stirrer
tantric2.718
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[*] posted on 4-6-2017 at 14:40
DIY microwave reactor with integrated stirrer


NOTE TO MODS: i've been away for a while and i accidentally put this in the wrong sub forum, should be in apparatus acquisition.

first, this has nothing to do with plasma or nitric acid. i just need a microwave with a hole in the top for the condenser.

can i use the pre-existing turner mechanism as a magnetic stirrer? it's inset into the bottom of the chamber. i can get a new glass plate that covers it but doesn't connect then glue teflon covered stirbars to the arms of the turner. it would be slow, but it would be good enough.it would likely work better if i could get a bunch of stirballs instead of bars.

okay, tell me why this is impossible or tell me how to speed up the turner.

thanks.

Banksy-Anarchist-and-Mother.jpg - 38kB

[Edited on 4-6-2017 by tantric2.718]
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Chemetix
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[*] posted on 4-6-2017 at 15:10


The turning mechanism is driven by a motor that is set to around 8RPM. The only way to speed it up is replace it with something that fits.

I'm uneasy about trying to put holes in the cavity. Wouldn't that just shoot microwave radiation straight up the condenser? Even of you put reflector mesh in the condenser bore, the glass of the condenser would be wider than the spacing in the reflector mesh and would also leak radiation.
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[*] posted on 4-6-2017 at 15:35


People have put holes in the top of microwave ovens before. It would be worth checking for radiation leaks if you intend to do this. Microwaves are not to be trifled with.

I would imagine that you could come up with a shielding solution that fits your geometry. It might mean putting some metal mesh in the mouth of your condenser or creating a curved metal adapter leading from reaction vessel inside to glassware outside.

If you asked, Chemetix could probably make you a glass adapter with embedded mesh that you could use for microwave work. Or maybe you could get away with silvering a glass straight adapter and plugging it with a mesh to halt straight-through radiation.
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Twospoons
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[*] posted on 4-6-2017 at 15:46


Usual technique is to put a microwave absorber at the top of the opening - graphite block, ferrite block, hell even a container of water would work.
The other way to do it is make the opening into a proper waveguide, with the length adjusted so that the microwaves are reflected back from the open end. How good is your microwave transmission line theory?




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tantric2.718
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[*] posted on 4-6-2017 at 19:13


commercial microwaves use a wavelength of 12cm. so long as the hole is less than that in diameter, there will be no leakage. originally i was thinking of some kind of teflon gasket on the condenser, but now...science! it works, bitches.

[Edited on 5-6-2017 by tantric2.718]
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[*] posted on 5-6-2017 at 13:34


Actually no - a 1/4 wave hole will act as an antenna. Rule of thumb for shielding is no slots or holes bigger than 1/20 of the wavelength you are trying to suppress. (I'm an electronic engineer by profession)



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tantric2.718
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[*] posted on 1-7-2017 at 10:33


i could be totally wrong about all of this...

the radiation from a microwave isn't ionizing/beta.


Quote:

Microwave radiation can heat body tissue the same way it heats food. Exposure to high levels of microwaves can cause a painful burn. Two areas of the body, the eyes and the testes, are particularly vulnerable to RF heating because there is relatively little blood flow in them to carry away excess heat. Additionally, the lens of the eye is particularly sensitive to intense heat, and exposure to high levels of microwaves can cause cataracts. But these types of injuries – burns and cataracts – can only be caused by exposure to large amounts of microwave radiation.



so honestly, what does it matter? if the reactor is in a closet with no metal exposed and condensor threaded through a graphite block and perhaps a microwave safe bowl hanging over it.....all microwaves at that wavelength can do is burn you.

at what rate are 12cm microwaves absorbed by air? what about just putting a water vaporizer/steam generator pointed above it?

i need this to do is run for 30 to turn apiole into isoapiole.
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[*] posted on 1-7-2017 at 15:30


Quote: Originally posted by tantric2.718  

at what rate are 12cm microwaves absorbed by air?


They're not. Apart from the usual inverse square law (power density is inversely proportional to the square of the distance to the source) microwaves travel quite happily through air for long distances.
Your wifi wouldn't work very well otherwise.

I guess what we're all trying to say is make sure you reduce the risk as much as possible. Take all precautions - don't get hurt.




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[*] posted on 1-7-2017 at 23:29


I have a little experience with microwaves,
. a hole the size of a condenser certainly would leak microwaves
. a hole about 1/4 wavelength long (e.g. copper tube) should reflect most of the microwaves back into the cavity.

Also, I would want a Claisen adapter or similar in the hole to allow temperature measurement.




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[*] posted on 2-9-2017 at 19:36


You could test for the presents of microwaves leaking from the hole you drill with water or metal power.
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