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Cloner
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[*] posted on 13-5-2005 at 06:04
flame temperatures


I want to make conducting glass slides (layer of tin oxide) and require a temperature of about 600 degrees C.

Now I wonder if a normal bunsen burner is capable of producing such a temperature in the bluest part. I can melt soft glass for pulling capillaries in that flame. Microscope slides are another type of glass, they at least dont seem to soften in that flame.
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neutrino
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[*] posted on 13-5-2005 at 12:47


Easily. You probably just have to hold the slide in the flame a little longer. I suspect that it's made of soda-lime glass, which is very easy to soften.
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[*] posted on 13-5-2005 at 13:55


Bunsen burners running on propane achieve 1300-1500K. Using methane 1800K is possible.



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Esplosivo
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[*] posted on 13-5-2005 at 21:05


Since this thread regards flame temperatures does anyone have any idea of what temperature can be reached by a flame of a kitchen burner running on propane? I intend to use one for pyrolysis of acetone and need to have an idea of the temperatures the flame can reach. Thanks for the help.



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12AX7
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[*] posted on 13-5-2005 at 22:10


Well, propane in general can reach 3500°F+, there's at least one person who made a furnace capable of melting steels, not that I'd want to pay his fuel bill. A cold, uninsulated flame like that might reach orange heat. Well, there's an easy way to test - put something in the flame and see what it gets up to! Mind that thin objects more accurately reveal the actual flame temperature, but are unrealistic at best when it comes to heating anything of substance.

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neutrino
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[*] posted on 14-5-2005 at 04:23


Propane torches get very hot; I can soften capillary tubing made of something like vycor (mp = 1600*C) in the flame. Remember, though, that this is extremely thin tubing and you'll never get anything big to this temperature.
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Cloner
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[*] posted on 24-5-2005 at 06:12


well, as it turns out getting 600 out of the flame is no problem at all; the knowing of the temperature is another matter. Anyway, it worked somewhat in that oxide did form but in horribly varying thicknesses as the color tells.
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[*] posted on 24-5-2005 at 08:37


Quote:
Originally posted by Cloner
well, as it turns out getting 600 out of the flame is no problem at all; the knowing of the temperature is another matter.


I've run up against that question as well-- it's a tough one. See http://www.crscientific.com/newsletter-10.html

I'm even leaning more toward the "practical" temperature of a propane torch as being around 900-1000 C, not even 1200.
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Cloner
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[*] posted on 31-5-2005 at 01:10


I think the best way would be to use a ceramic tile (the ones for streeting seem right to me). Heating this would ideally happen in an oven though. But one could put scraps of lead and aluminum on the tile to betray the melting point. Such tiles would offer gradual cooling as well, which seems to be necessary for thicker glass.
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Lambda
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[*] posted on 6-6-2005 at 11:32
Evenly distributed tin oxide layer.


Quote:
Originally posted by Cloner
I want to make conducting glass slides (layer of tin oxide) and require a temperature of about 600 degrees C.

Seeing that you want to use tin oxide as your conductor, maybe this procedure can prove to be a way arround, however more cumbersome:

1) By dipping your pretreated glassware in a Thollens solution, your will be able to make it conductive by means of a silver layer (the silver mirror experiment is wel described in literature: CAUTION !!, kept solutions form highly unstable and (spontainously) explosive silver nitrides).

2a) Now your glassware has become conductive, and tin may be electroplated on it. (some electronic stores sell electroplating solutions of tin, for PCB-plating, as wel as silver and gold solutions for the same purpose).

2b) A this point, you may allso be able to dip your preheated glassware in molten tin, this may then stick (*).

3) Assuming your glassware has a layer of tin deposited on it, this layer may then be oxidized by means of nitric acid to tin oxide.

You will get a beautifully even tin oxide layer. However, if your intention is to get a tin silicate fusion product with glass, on which tin oxide lays, then it must be heated in the oxidizing zone of the flame.

(*) By pretreating your glassware with a hydrogen fluoride or ammonium biflouride solution, you will get better adheasion of the silver layer (sandblasting may allso be done instead).
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[Edited on 7-6-2005 by Lambda]
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Cloner
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[*] posted on 8-6-2005 at 09:32


Thanks for the procedure. I have a few questions though.

First of all, making a silver mirror and plating tin on it gives the glass a pretty thick silver coating that comes before the tin. Oxidizing all of it to oxides would thus deliver silver oxide and tin oxide in top of it. Is all that still transparent?

Will molten tin stick to glass or roll off in droplets? I fear the latter, so I assume you mean to dip tin plated slides in molten tin. Why this step if you can just plate further?

You mention getting beautifully even tin oxide layers by nitric acid oxidation of a 'tin mirror' on glass. Have you produced such layers and if yes, how translucent were these?

Thanks in advance.
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neutrino
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[*] posted on 8-6-2005 at 12:58


Oxidizing silver would not be easy, as the oxide is very unstable.

Tin wouldn’t stick to the glass. Most plate glass is made by letting molten glass solidify on a molten tin bath, then separating the two afterward. If this can be done so easily and economically, the two must not stick well.
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Cloner
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[*] posted on 9-6-2005 at 01:06


well, silver oxide comes out if you put silver nitrate in high PH. It is probably unstable in light.
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Lambda
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[*] posted on 9-6-2005 at 10:47
Tinplating glass on wich a uM-layer of Silver sits !!!


What I wrote is, tinplating glass that has been pretreated with a silver layer. This silver mirror layer is in the uM-range of thickness.

Tin sticks to this !!!.

Pretreating the naked glass is to get better adhesion of the silver layer (not the tin layer).

I did not write about "sticking tin to glass".
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12AX7
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[*] posted on 9-6-2005 at 16:18


Quote:
Originally posted by Lambda
Tin sticks to this !!!.


Hmm, ya know what, tin dissolves about 2% Ag at ordinary molten temperatures. I bet it'll just bead up and roll off, unless the adhesive force remains.

Indium is an expensive possibility, FWIW. Ga and alloys (so I'm assuming In as well) wet glass.

Tim
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Lambda
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[*] posted on 9-6-2005 at 18:03


Quote:
Originally posted by Lambda
2a) Now your glassware has become conductive, and tin may be electroplated on it. (some electronic stores sell electroplating solutions of tin, for PCB-plating, as wel as silver and gold solutions for the same purpose).

A quick dip may resolve the "roll-off" problem:
Quote:
Originally posted by Lambda
2b) A this point, you may allso be able to dip your preheated glassware in molten tin, this may then stick.

The reason that tin and silver adhere so well, is because of the dissolving properties of these two metals on the boarder line

Evaporating tin fumes on this silver layer will most probably solve the solubillity/roll-off problem, but is this practical ?.

Scraping off the protective layer of a rhodium-plated mirror, galvanising or dipping it in molten tin, may be a more practical obtainable objective for Cloner. However, I don't think this will easily be made translucent anymore.
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Originally posted by 12AX7
Indium is an expensive possibility, FWIW. Ga and alloys (so I'm assuming In as well) wet glass.

Using Indium or galium alloys for the primary coating layer may be a rather expensive and thus unpractical path for Cloner to wander.

With unlimited resorces, it's often not very difficult to obtain ones objectives, but unpractical propositions to the chemist wich may have only limited recorces are completely worthless !
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[*] posted on 9-6-2005 at 20:03


Quote:
Originally posted by Lambda
Evaporating tin fumes on this silver layer will most probably solve the solubillity/roll-off problem, but is this practical ?.


Hmm, since tin boils at 4000°F, electroplating would be a good idea. :) If you plate a layer about equal thickness to the silver, heat probably won't damage it, since it's past at least the low-melting point mixture. (The interfacial layer will still melt (solidus) at 494K, but the entire layer won't fully melt (liquidus) until 830K or so.)

Tim
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