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12AX7
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Noooo!
Look at it this way: clean 'er off with some acid (or sandpaper, or...), recoat and you'll have more surface area! 
Tim
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Rosco Bodine
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Gone too soon , we shall miss Gerty ......
The flower of youth is fleeting , it lasts but a moment .
She looks so ....unspeakably horribly ravaged 
You can almost hear her crying out in final despair
"goodbye cruel world"
RIP Gerty , a musical tribute and farewell
http://youtube.com/watch?v=oiFTXckh0zU&feature=related
| Quote: | Originally posted by Xenoid
Long live Hubert... 
I am sorry to report that the brave little anode Gertrude (known affectionatly as "Gerty" to some of you) died this afternoon local time.
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From the looks of her , expiration came as a merciful end .
| Quote: |
During her short lifetime of approximately 146 Amp hours, in the often harsh environments of assorted perchlorate cells, Gerty is estimated to have
converted about 280g of NaClO3 to 322g of NaClO4.
Gerty died from the hideous effects of slow passivation followed by massive overvoltage application.
Please do not let this happen to your anodes!
Gerty died alone, while I was having a pleasant hike in the mountains. I had inadvertantly left the voltage limiting set to maximum (~ 30 volts) on my
lab power supply while running in constant current mode (1 amp). I am not sure what the exact "breakdown" voltage for the passivated layer is, but it
obviously less than 30 volts...  |
Evidence shows clearly that this was no accident but murder most foul . The usual suspects are believed to have been responsible . She was
overpowered and forcibly
oxygenated again and again and again , until she was dead . The body was mutilated and crows are yet observed
picking pieces of her rotting remains from the trees . It is all so .....ghastly 
| Quote: |
I now have a 300 ml perchlorate cell "chocka-block" full of steaming, white, TiO2 gloop!
Moral, never apply more than about 10 volts across a Ti anode in a perchlorate cell!
I have more "bad news" but I am too distraught to report it at the present time... 
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You mean it gets worse ??? Brace yourself and tell us ,
screw your courage to the sticking place ,
and let us hear it ....the rest of the story
[Edited on 30-12-2007 by Rosco Bodine]
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Xenoid
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@ 12AX7
Hmmm.. I think she's past the "cleaning up with sandpaper" stage. One thing I was thinking about though, is that if this process was carried out in a
"more controlled" manner it might be possible to produce a high surface area that bonds well to any interface layers. Actually, I don't think sanding
produces all that great a surface, it's more like lots of smooth grooves.
If the Ti was corroded using say 10 mA, or 100 mA, who knows, at the breakdown voltage, it might produce a superb bonding surface akin to
sandblasting, but better. This could be further enhanced with HCl etching. One problem, is that the high voltage breakdown starts at defects and
pinholes, and might not produce an even surface. A low current over a longer time might solve this though.
@ Rosco
Don't fret Rosco, my "bad news" has nothing to do with coating Ti anodes. It concerns "Big Bertha", my 10 litre, 12 gouging rod chlorate cell. It
relates to the application of 25 amps through SS junctions in the presence of saline solution, chlorine and air. I can't believe I cocked this up
twice in about a week... 
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12AX7
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Hmm, check out electropolishing titanium -- if it exists. I get a nasty feeling the bath would require fluoride, though. Well, that's still not too
bad, under electrolysis, the bath could be pH-neutral for the most part. The anode might give off some HF fumes though.
Tim
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man_from_mystery_babylon
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Yes titanium can be electropolished. There is even a company that claims to be using a "saline" solution to do it.
I emailed them with some questions about their process, but of course they never responded.
As I understand it, you need a rather high current density to electropolish...as below some threshold point, you only etch.
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chloric1
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@Xenoid-You said Gerty got ate up by a condition of overvoltage because you did not set your limit to a lower level. I know the voltage increased
slighty with your first cobalt anode, but I am not sure at what rate Gerty increased in voltage. If you could ballpark some relative graph or
something to see if this manganese thing is indeed a step forward. Also, figuring total hours of use between the two. I believe that you stated your
initial cobalt anode was useless for perchlorate. Once more data is produced the more it will have to be consolidated and organized.
@Rosco-A tad melodramitic dont ya think?!
I did enjoy the video you linked to it went well with my toast and coffee this morning.
[Edited on 12/30/2007 by chloric1]
Fellow molecular manipulator
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Xenoid
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| Quote: | Originally posted by chloric1
@Xenoid-You said Gerty got ate up by a condition of overvoltage because you did not set your limit to a lower level. I know the voltage increased
slighty with your first cobalt anode, but I am not sure at what rate Gerty increased in voltage. If you could ballpark some relative graph or
something to see if this manganese thing is indeed a step forward. Also, figuring total hours of use between the two. I believe that you stated your
initial cobalt anode was useless for perchlorate. Once more data is produced the more it will have to be consolidated and organized.
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Well, part of the problem was I messed around with solutions and current settings for the first 76 hours. I would say that based on 1 amp at
50mA/cm^2 she started the run at 3.7 volts which rose to 4.0 volts at the end of the 76 hours.
I then put her in a new cell where she lasted for about 70 hours, she started at 4.0 volts and after 50 hours was at 4.8 volts, on the morning of her
demise the voltage had risen to 5.5 volts. I should have shut her down then, and she would have lived to make perchlorate another day, but the black
coat still looked intact and "I just wanted to see what would happen". Now I know...
The beta-MnO2 coat was definitely a step forward as far as perchlorate goes. The 12 coat Co3O4 anode only ran for about 25 hours, under similar
conditions.
The straight 4 coat Co3O4 was good in a chlorate cell, I think it was 13 days, I haven't tried beta-MnO2 in chlorate yet!
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Rosco Bodine
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The interface works and the outside reaction layer works .
But both are porous . An intermediate layer is needed .
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chloric1
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@Xenoid-Ok that gives me some idea how you are operating. I have been stalling for a few reasons getting started. I got half of my nitrate
solutions made up already but I ordered some 1L beakers so I could do the boiling oxalic acid etch. I always liked oxalic acid and I am not real
excited about hot concentrated HCl. But then yesterday I reread some of your post in cobalt earlier on. You used a beaker of water to heat the test
tube of HCl. This is what I will do until my beakers arrive. My first anode will be tested in a brine to make chlorate because I need to see and
show how it compares to your cobalt spinel alone. Manganese coatings and perchlorates a little later.
@Rosco- Yes I know. Don't know if it is necessary for a seal for making only chlorate but it is definately true for perchlorate. My answer,when I
got the time and if I find my 5 year old stannous choride, is to dissolve stannous chloride in conc. HCl,oxidize with H2O2,and then add ammonia to
precipitate stannic oxide and remove pesky chlorides, then redissolve in nitric acid at specific gravity 1.2. Then I will either add cobalt nitrate
or nickel nitrate. Probably 10% concentration of the secondary components seems adequate.
Chlorides, I feel, might even be atogonistic agents for titanium passivation and should be avoided. These ions have a nasty reputation in
electroplating as well as metal finishing. Ever heard of "bronze disease" ? Find a bronze statue close to the coast and you will see.
[Edited on 12/31/2007 by chloric1]
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Rosco Bodine
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| Quote: | Originally posted by chloric1
@Rosco- Yes I know. Don't know if it is necessary for a seal for making only chlorate but it is definately true for perchlorate.
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It serves a larger purpose than just a seal to have an
intermediate layer of SnO2 . That larger purpose is something which I don't think has been discussed in any of these threads before , but it is
important . There is a logical
strategy where plural coatings are laminated on a substrate
which should attempt to have a sequence of coatings that
ideally obey an *ascending* oxygen overvoltage value from
the outermost layer inwards towards the substrate . The
outermost coating is optimized for catalytic activity for the
desired product , but will probably not be optimized physically
and likely will be porous . Desirably the next layer which resides beneath that porous outer coating will have a slightly
higher oxygen overvoltage so that oxygen is preferentially
evolved from the outer coating , rather than being encouraged to spread laterally *between the layers* at those places where the bottom of a pore in
the outer layer
contacts the intermediate layer . A pressure gradient is
created by the oxygen overvoltages . By having the underlayment layer have the *higher* oxygen overpotential ,
it creates a *physical* effect for oxygen evolution that is
a parallel similar to how a body of water seeks its own level
rather than trying to flow uphill . The equilibrium favors that
oxygen will evolve preferentially at its path of least resistance , on the outside layer material exposed to the electrolyte .....rather than trying
to migrate between the layers and delaminate the outer coating . You see the nascent reaction products are going to actively seek the
easiest path for their "birth" , and the easiest path for
evolution of those electrolytic products must be kept located
preferably with the outermost "working coating" .
Oxygen overvoltage is sort of an indicator because it is
pretty much a concensus that it is oxygen permeation , diffusion of oxygen downwards through the coatings and reaching the substrate which ultimately
passivates the anode . And by having the layers create an effect that presents an unfavorable gradient for that diffusion , the substrate is more
protected . The idea is that oxygen should have to "flow uphill" to reach the substrate . When voltage
is applied to the anode and current flows , the goal is that the energy be dissipated on the outer surface preferentially
as much as possible , rather than following a path of less resistance presented by an interface at underlying layers .
| Quote: |
My answer,when I got the time and if I find my 5 year old stannous choride, is to dissolve stannous chloride in conc. HCl,oxidize with H2O2,and then
add ammonia to precipitate stannic oxide and remove pesky chlorides, then redissolve in nitric acid at specific gravity 1.2. Then I will either add
cobalt nitrate or nickel nitrate. Probably 10% concentration of the secondary components seems adequate. |
The best initial sealing layer over the cobalt spinel could very well be an oxidative soak deposition of SnO2 precipitated from dilute SnCl2 + NaNO3 ,
then baked . This would involve
no complicated preparations .
The use of Sn nitrates certainly intrigues me because they are mentioned as useful precursors in several patents , but
no details given ....almost as if this could be something of a "secret hidden in plain sight" if you follow what I mean .
| Quote: |
Chlorides, I feel, might even be atogonistic agents for titanium passivation and should be avoided. These ions have a nasty reputation in
electroplating as well as metal finishing. Ever heard of "bronze disease" ? Find a bronze statue close to the coast and you will see.
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Yeah , I have had some reservation about the "chlorides fluxing scenario" with regards to the DTO on Ti scheme ,
but not because of any prejudice against chlorides themselves since they are useful intermediates . My
reservations concerning chlorides involves the way they are described being used , which I know is oversimplification in describing a "reagent
preparation" where the reagent itself is more than its ingredient list , but rather a reaction product which changes minute by minute . These
mixtures are unstable and react to form sols , alkoxides , and complex mixtures for which there are alternatives . There are several ways of doing
the same thing , with variants that are more appropriate depending on compatability with other coatings , dopants , and the temperatures which will be
used .
I am still looking at these SnO2 based coating references ,
trying to find anything useful . Went through a search hits list of several hundred abstracts yesterday and found five more articles , a couple of
them especially interesting ,
requested in the references needed thread .
One of those articles abstract describes what evidently may be a variant on the soak deposition method , where a
simple solution of SnCl4 at a specific concentration and pH ,
is deliberately made unstable via hydrolysis and gradually
"slimes" a coating of SnO2 onto an immersed substrate ,
which is no slime at all of course , but a tough and adherent
coating , which may be baked to further vitrify .
Also of interest are other articles which involve nanocrystallites of SnO2 formed *in solution* where
dopants are included at the molecular level *before any baking* , as these materials may be used as thickeners
in mixture with other precursors for baked coatings .
It is very interesting to have a colloid , whose particles
are not amorphous at all , but rather are crystals a few nanometers in dimension . Like having a bag of tiny conductive jewels so small they suspend
in water without sinking .
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tentacles
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Rosco: Re: "uphill substrates" - That would track along with something I'd read (somewhere) about PbO2 plating in industry - that PbO2 plating was
typically conducted at 70C. I've read (somewhere else, probably) that plating PbO2 at higher temperatures will lower it's oxygen overpotential.
Obviously this would make it easier to find intermediates with a higher overpotential, or perhaps cause the intermediates to last much longer with a
greater difference.
[Edited on 1-1-2008 by tentacles]
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Xenoid
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@ tentacles
See the list of anode compositions posted by R.P.Wang on page 8 of this thread!
http://www.sciencemadness.org/talk/viewthread.php?tid=9572&a...
Ti / SnO2 + Sb / alpha-PbO2 / beta-PbO2 is claimed to be "reliable".
[Edited on 1-1-2008 by Xenoid]
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Rosco Bodine
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There is probably an inherent benefit from the differing
oxygen overvoltage effect derived automatically when
alternating layers of different materials are used in sequence , for *two* paired layer cycles like A-B/A-B as a configuration , because even if you
don't know which
of the materials A or B has the higher oxygen overvoltage ,
the barrier will still exist for that labrynth if B turns out to be the layer with the higher O2 overvoltage . It would
result in shedding of the outer layer B , but then the
correct ordering would be encountered and further erosion
would then be opposed .
So using different layers in alternating fashion makes good sense as a strategy , even if there is not good specific information about the differences
between the O2 overvoltage for the different layer materials being used ....
but only if at least four layers are used to hedge the bet
for that unknown . In scientific terminology , that is known as covering ones ass
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Xenoid
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Hubert's Fate
The fate of Hubert has been decided! He is to spend his life in the confines of a KClO3 cell. Why POTASSIUM chlorate,
I hear you say. Well, a number of reasons;
1) I have never run a KClO3 cell, not much point with only graphite and gouging rods for anodes. I am approaching this with an air of optimism though
and expecting this cell will run perfectly "clean".
2) I wanted to try and make some totally Na free KClO3.
3) I already have two NaClO3 cells running.
4) Experience with "Gertrude" and earlier anodes, suggests a chlorate rather than a perchlorate cell is a safer place for an anode of Hubert's
composition.
I put together a more or less practical cell specifically to accommodate Hubert (see attached image). It has a capacity of 800 mls and an annular SS
cathode and was cobbled together from bits of previous cells. The internal connections for the SS cathode are covered in glue lined heatshrink and the
SS screw electrical connection is coated in hot glue. Hopefully this will prevent headspace corrosion of the cathode which has been causing me a few
problems lately.
The cell has been running for about 28 hours now at 2 amps and 3.6 volts (55 mA/cm^2). So far there is absolutely no black specks of MnO2 floating
around, this has plagued earlier MnO2 anodes. The cell actually looks like a large jar of pink champagne. But it's not a tipple I would like to try.
More like a cocktail from hell. I was surprised to see small, flakey crystals of KClO3 settling on the bottom only 12 hours after starting. I thought
it would take longer, but I suppose KClO3 is near insoluble in near saturated KCl solution. Looking good now, but what it will be like in a couple of
weeks time is anybody's guess!
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jpsmith123
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This wire had a layer of Co cathodically electrodeposited onto it from Co acetate & vinegar solution. It seemed to form a relatively thick, even,
highly adherent layer.
After that it was heated in a gas flame for about 5 minutes, during which time the color changed from grey to blue/black.
Unlike the previous anodically deposited films, this coating cannot be rubbed off, smudged, etc.
Hopefully I'll get to try it in NaCl solution later today.
[Edited on by jpsmith123]
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Rosco Bodine
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@jpsmith123
In dann2's ATO thread I posted a patent US4584084
http://www.sciencemadness.org/talk/viewthread.php?action=att...
which described something like the Beer patent compositions where TiO2 was used as a component of the intermediate layer , but derived from a Ti salt
precursor
which was decomposed on baking , in mixture with the
other solid solution and dopant materials . It was significant information not only in relation to the Beer
patents similar but different use of Ti oxides as a part of the intermediate layer , but also because layers even using that TiO2 as part of a
tertiary composition with
Fe and Sn oxides , had performance several times better
than ATO intermediate layers .
I expected you to be jumping on that disclosure , since it
aligns with the Beer patents use of TiO2 as a "toughener"
component for the intermediate layer , and IIRC a couple of the Shamrock patents had similarly reported a toughened intermediate layer using a TiO2
component .
IIRC these baked intermediate layers actually even increase the longevity of Pt plated Ti anodes above what
is gotten from direct plating of Pt onto Ti , especially for thinner platings .
I don't know if the same thing will hold true for your
Co plating then oxidized to the oxide , but it might .
Or it may be that a TiO2 tertiary interface composition might similarly result from a baking and diffusion , perhaps
if you overcoat or undercoat the Co metal with an SnO2
precursor . It's going to require more heat for such a scheme than the cobalt spinel derived from nitrate .
The Fe doped SnO2 - TiO2 mixture is a very interesting
intermediate layer anyway especially if it does prove
more durable than the usual ATO .
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Xenoid
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Update on Hubert
Hubert has been running in the 800 ml KClO3 cell for 3 days now.
The solution is a pale pink from MnO4- but has not increased in colour from beyond the first 12 hours. I think an equilibrium has been achieved with
the MnO2 on the anode. This may be some sort of "common ion effect" as mentioned by Rosco. The colour looks worse than what it is, due to the strong
colouration ability of MnO4-, and is really a miniscule amout that can be cleared away with a few drops of H2O2.
Other than the pink colouration, the solution is crystal clear (literally). I have dropped in a magnetic stirrer bar to improve the efficiency and
this brought about a "snow storm" of 5mm of KClO3 overnight. There is now about 10 mm of crystal "snow" accumulated on the bottom, and it's really
blowing a blizzard in there.
I'm very pleased with Huberts performance "so far".
In the background of the attached image you can see my chlorinator anode cell, note the disgusting colour. This is mainly caused by corrosion of the
cathode in the "headspace" area. Some of the black "dusty" material appears to be coming off the MMO anodes.... gulp! The "theoretical" runtime
finished a few days ago, but I'm going to let it go a few more days!
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dann2
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Hello,
The 'Alembic' anode way way back used the same system and he has stated that many hundreds of hours were obtained from the anode without any visable
signs of wear.
The anode is a bit of bother to make though. Did I mention it's of holy grail status??
Finally got around to titrating the product from a Perchlorate cell which had the DTO anode running in it. 5 coat anode.
This cell had been run for much much more than the run time of the cell (going from Chlorate to Perchlorate).
The cell product contains 79% Chlorate.
You also get ignition when the product is mixed with sugar and a drop of Sulphuric applied.
DTO is a hopeless anode for Perchlorate making. It lasts quite a long time though, approx 450 hours as far as I can remember.
The pink Chlorate cell is a VERY confusing sight. I could make some politically incorrect jokes........... but I won't.
Keep it up.
Dann2
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Xenoid
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Hubert and Purple Haze
"Hubert" and "Purple Haze" seem to be getting on very well together. This cell has now been running for over 6 days with absolutely no change in the
electrical parameters, still 2.0 amps at 3.5 volts. I switched it off this morning and when the bubbles cleared Hubert's shiny blackness could be
readily observed. The cell is still crystal clear, other than the pink tint. The KClO3 crystals are now twice as deep as in the image shown
previously, and there are clusters of crystals adhering to the outside of the annular cathode. The KClO3 is now interfering with the stirrer bar and
the electrolyte circulation. I guess I should "harvest" the KClO3 and top up the cell with saturated KCl and just keep it running.
@ dann2 - Yes I thought of all those jokes as well....
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chloric1
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Its just a one eyed, one horned flyin purple chlorate maker...
I am happy for you and for Hubert. In this gray and endless winter it is nice to see the colors of spring! I guess this anode is going to have a life of several hundred ours.
It appears that 50 to 60mA/cm2 is ideal for this kind of anode.
[Edited on 1/7/2008 by chloric1]
Fellow molecular manipulator
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Xenoid
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| Quote: | Originally posted by chloric1
It appears that 50 to 60mA/cm2 is ideal for this kind of anode.
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Well, I don't really know! I just used a current density that wasn't too extreme. It's a useful, practical density, and higher than what I use for
gouging rods. The coating may work just as well at 100 mA/cm^2 or may blow to bits. It's something that needs more testing, but is not all that
important at the moment!
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Rosco Bodine
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@Xenoid
You mentioned earlier about the heat gun being pressed
to produce hot enough temperatures inside the tube
you are using as an oven . Is that a solid tube you are using and what diameter ? Are you using any sort of insulation wrapping around the tube ?
The heat gun tube oven is something I have been
giving some thought . I am considering using some
perforated stainless tubing and then wrapping it with
insulation , perhaps the 2 inch wide woven fiberglass
ribbon that is sold as exhaust header wrap for keeping
engine compartments cooler . I am thinking that the
heat loss from the tube itself would be greatly reduced
by using such a scheme , which should raise the temperature capability .
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Xenoid
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| Quote: | Originally posted by Rosco Bodine
Is that a solid tube you are using and what diameter ? Are you using any sort of insulation wrapping around the tube ?
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It's just a piece of scrap Al tube (~50 mm dia. 2mm wall) I happened to have lying around that fitted fairly tightly on the end of the gun. I have now
wrapped a strip of thin tinplate around the end of the heat gun so it fits really tightly, it was a bit wobbly before. I don't think insulation is
required, I'd say 98% of the heat loss was as hot air out the top! I'm using solid Ti rods, they absorb a lot of heat, and for the first couple of
mins. the "heat setting" knob needs to be higher to reach, say 380 oC, then I can "back it off" a bit for the rest of the time.
My heat gun has 4 inlet slots, I taped over the two smaller ones. When I checked the temp. on max setting it rose steadily and would have exceeded 400
0C. So I am running it at about 80 - 90 % setting for the pyrolysis.
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Rosco Bodine
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It would have to be losing a whole lot of heat off the tube . I bet if you wrapped the tube with some foil backed fiberglass pipe wrap , the temp
inside the tube
would jump up 200C from where it is .
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chloric1
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Might sound sloppy but I have 1/4" diameter rods(6.35mm) and I am going to heat with the airgun and mount the rod with a clamp on a ringstand so I can
hold horizontal. I use a heat gun every day at work so I am used to waving it and distributing the heat. I won a thermocouple on ebay for my digital
multimeter but it will not be here for some time. Will have to watch the process to see what going on. When my thermocouple probe gets here, I may
use a vycor tube and just support the titanium with one hole stoppers.
[Edited on 1/7/2008 by chloric1]
Fellow molecular manipulator
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