Not logged in [Login - Register]
 Sciencemadness Discussion Board » Special topics » Technochemistry » Forget everything else, diamond is the answer! Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Detritus   » Test Forum

Pages:  1    3  4
Author: Subject: Forget everything else, diamond is the answer!
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

Forget everything else, diamond is the answer!

According to the attached review paper, doped diamond electrodes may replace MMO, platinum and PbO2.

The paper doesn't explicitly mention suitability for perchlorate production, but it's clearly implied I would say.

Also, U.S. patent app. #20070170070 claims the use of a doped diamond coated anode to make perchloric acid.

Being that graphite can apparently be used as a substrate for diamond deposition, and being that "diamond-like" films can be electrolytically deposited from methanol...this gets me thinking...I wonder if trimethyl borate could be added to the methanol to dope the product with boron?

Attachment: Doped Diamond Electrodes.pdf (804kB)

Xenoid
International Hazard

Posts: 774
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline

Mood: Comfortably Numb

Hmmm..... Now all we have to do is erect aerials on our roofs, and wait for a thunderstorm....

May be we should all try Bob's method after all ....

http://members.tm.net/lapointe/Allotropes.html

[Edited on 13-12-2007 by Xenoid]
JohnWW
International Hazard

Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline

Mood: No Mood

The only problem is that diamond is a very good insulator, in fact one of the best. "Doping" it with small amounts of N or B, incorporated into artificial diamonds, which is a very expensive thing to do, has been done to make semiconductors (n and p type respectively), which operate at voltages about 5 times that for Si or Ge based semiconductors, although because of their cost they are still largely experimental.
I am a fish
undersea enforcer

Posts: 600
Registered: 16-1-2003
Location: Bath, United Kingdom
Member Is Offline

Mood: Ichthyoidal

Actually, not doping synthetic diamond with nitrogen is the difficult bit. Diamonds produced by Gemesis are yellow in colour due to nitrogen impurities. Avoiding this contamination is a major technical challenge.

1f /0u (4|\\| |234d 7|-|15, /0u |234||/ |\\|33d 70 937 0u7 /\\/\\0|23.
12AX7
Post Harlot

Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline

Mood: informative

Odd, I heard that they produce N-doped diamonds because they are more expensive.

Edit: The wiki article implies that a vacuum chamber may be all that is needed. Exclude N2, maybe introduce BH3, etc. as desired. (For that matter, B dissolves in Fe. Even easier.)

Tim

[Edited on 12-14-2007 by 12AX7]

Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
I am a fish
undersea enforcer

Posts: 600
Registered: 16-1-2003
Location: Bath, United Kingdom
Member Is Offline

Mood: Ichthyoidal

The impure nitrogen-doped diamonds sell for more, because that is how the gem market is stacked, with coloured gems attracting higher prices. However, technically speaking, the nitrogen doping is a flaw in the process.

1f /0u (4|\\| |234d 7|-|15, /0u |234||/ |\\|33d 70 937 0u7 /\\/\\0|23.
dann2
International Hazard

Posts: 1523
Registered: 31-1-2007
Member Is Offline

Mood: No Mood

Hello,

I am no diamond expert but I will come in with my 2c's worth. (pun intended).
I think the N doped one sell for more if they are naturally occuring only. If made in the lab (N doped or otherwise) they sell for less.
Lab make diamonds can be told apart from naturally occuring ones by a lab test. Don't think you can tell them apart (the good one's anyways) from visual inspection.

One last gem of info:
Diamond has one of the highest thermal conductivity off all substances. It conducts heat by some weird and wonderful 'lattice vibrations'.

Dann2
Xenoid
International Hazard

Posts: 774
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline

Mood: Comfortably Numb

Synthetic diamonds made by the latest techniques are readily distinguished from natural stones by optical microscopic examination, they are FLAWLESS. Natural stones have all sorts of lattice defects and occluded minerals.

I am still waiting for the diamond coated frying pans, which were touted about, several years ago...
12AX7
Post Harlot

Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline

Mood: informative

It also has an anomalous heat capacity, something Einstein and Debye theorized on early in the 20th century. The best explanation is a lattice of relatively stiff oscillators, linked to each other such that one can analyze the exchange of energy as wave particles -- phonons -- bouncing around inside, having energies from about zero up to a cutoff, such that the wavelength of these oscillations must be less than the corresponding distance between atoms.

Diamond is composed of a rather stiff lattice; as a result, these oscillators have steep energy levels and don't store much energy (as heat) at low temperatures. As a result, diamond has significantly less heat capacity than most other materials at room temperature.

Statistical mechanics is interesting, if mathematically intensive. I now know the formulas and derivations explaining this, though it's certainly above and beyond the topic of this thread (and probably of even less interest to most here!).

Tim

Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
chloric1
International Hazard

Posts: 1039
Registered: 8-10-2003
Location: closer to the anode
Member Is Offline

Mood: Strongly alkaline

We only need a plasma at 2200 to 2800. Comeon it is not that hard to do in the garage.

Seriousy though, microwave energy was mentioned and someone that reads here who has telecommunication expertice might be able to make a microwave gun that can be tuned to energize some organic vapors. Microwaves are definately able to heat certain things up to insane temperatures in a hurry.

Silicon as a substrate? Wow! That's just crazy cool! Of coarse not practical for large electrodes but it would nice for a pocket model. I would like to known in my neighborhood as"The guy who makes doped diamond silicon substrate anodes" I wonder how well they could sell on ebay.

In the theater of life its nice to know where the exit doors are located.
Twospoons
International Hazard

Posts: 976
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline

Mood: Full of B12 - YIPPEE!

Of the diamond CVD papers I've seen, the most common (and accessible for us) method is simply a hot tungsten filament in a low pressure atmosphere of H2, CH4, CO2. Even the pressure requirements are not difficult ( 1or 2 torr IIRC). Typical substrates were tungsten sheet rubbed with diamond dust (for nucleation). Deposition rates are slow - μm per hour - so it would likely take a week or two to build a working coat.

Helicopter: "helico" -> spiral, "pter" -> with wings
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

I've seen a patent claiming that you can use water/alcohol vapor instead of H2 & CH4.

But anyone with a high voltage DC power supply can try the electrolysis of methanol as per the attached paper.

Attachment: Electrolysis of Methanol.pdf (132kB)

Nixie
National Hazard

Posts: 490
Registered: 12-12-2006
Member Is Offline

Mood: ?

 Quote: Originally posted by jpsmith123 I've seen a patent claiming that you can use water/alcohol vapor instead of H2 & CH4. But anyone with a high voltage DC power supply can try the electrolysis of methanol as per the attached paper.

I wonder if there's any benefit to going for a higher voltage (I can do about 150 kV at the suggested 20 mA current density), at least in terms of being able to deposit a thicker film. The only thing I'm missing to try that experiment is the HF for cleaning the substrate (and I have no clue how to obtain any). And how would one go about doping such a film?

[Edit:] By the way, I'm still waiting for you to answer my message from a long time ago :|

[Edited on 17-12-2007 by Nixie]

\"Good is a product of the ethical and spiritual artistry of individuals; it cannot be mass-produced.\" --Aldous Huxley
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

I'd bet that you could use a graphite substrate with the surface prepared by anodic etching in NaOH, Na2CO3, Na3PO4, etc. Maybe electrocleaned and hydrided titanium would work, too.

IMO, one interesting experimental aspect would be to see if the coatings could be made conductive by adding small amounts of, say, methyl borate or some other boron containing compound to the methanol.

(BTW sorry about the lapse. I was forced to move a few times, unexpectedly, and I had little or no internet access and no access to my files, etc., for a few months. Are you still involveed with that project?)
Nixie
National Hazard

Posts: 490
Registered: 12-12-2006
Member Is Offline

Mood: ?

I am; not in a hurry as work is busy at the moment, but I hope to get back to it early '08. It'd help if I knew what else I'd need to purchase so I watch out on eBay and surplus places.

\"Good is a product of the ethical and spiritual artistry of individuals; it cannot be mass-produced.\" --Aldous Huxley
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

I'm still thinking about this, especially since none of other efforts have yet produced a reliable perchlorate anode.

Ok here's the idea:

It seems that many places are selling diamond powder on line...I've seen it for a few dollars per gram. I would guess that at least some of these powders are "contaminated" with something else e.g. nitrogen, and are therefore conductive.

In several of his patents Beer talks about "rolling" the noble metal oxide into the titanium, or electrophoretic deposition, or just painting on an oxide slurry, followed by baking at high temperature.

According to several patents, titanium hydride can be used to create a bond to diamond; just mix the hydride with diamond and heat to decompose the hydride (preferably in an inert or a reducing atmosphere).

So why not take a piece of Ti, hydride it, coat it with diamond powder, and bake to create the bond?

[Edited on by jpsmith123]
-jeffB
Hazard to Others

Posts: 185
Registered: 6-12-2007
Member Is Offline

Mood: No Mood

If electrolyzing methanol at kilovolts is annoying, what about DMSO at 150V?

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=n...
-jeffB
Hazard to Others

Posts: 185
Registered: 6-12-2007
Member Is Offline

Mood: No Mood

 Quote: Originally posted by Xenoid I am still waiting for the diamond coated frying pans, which were touted about, several years ago...

I got to try one of these out some years ago -- a friend of mine ran a materials lab, and one of their collaborators was looking at starting up a company to make them. It was disappointing. It was a lot stickier than Teflon, or even well-seasoned cast-iron, and it certainly appeared to be scratched by stainless-steel utensils, although I suppose I may just have been leaving stainless-steel streaks on it. There is something cool, though, about the idea of serving breakfast out of a diamond skillet...
microcosmicus
National Hazard

Posts: 287
Registered: 31-12-2007
Member Is Offline

Mood: spin up

Assuming you have some sort of furnace which can achieve the required
temperature in an atmosphere which doesn't burn your diamonds, this
sounds like something interesting to try. This is the sort of procedure used
to make diamond files. At any rate, it would be interesting to be able to do
this at home --- I would certainly be curious to know how your attempts turn
out since high temperature stuff interests me.

As for use as an anode, an obvious point is that the substrate holding the
diamond is metal (titanium in this case) and therefore also conducts so,
if your purpose were to create an anode in which the conducting surface
were purely diamond, this would not do. Rather, you would have a mixed
titainium-diamond electrode. Looking at one of my diamond files, I see that
something like half the surface area is metal substrate, To have only the
diamond be in contact with the electrolyte, you would somehow have to
cover the titanium which holds the diamond grains in place with an insulator.
Maybe this could be done by some process like painting the electrode with
an insulator, then rubbing out the high spots so the diamonds show through
or maybe you could cover the Ti with a non-conductive oxide layer by anodizing it.

[Edited on 8-1-2008 by microcosmicus]
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

@-jeffB: Thanks for the reference. I've posted a request for the full paper.

@microcosmicus: Theoretically it's ok to have titanium exposed to the electrolyte, as it forms a self-protecting oxide layer. (That's why titanium and the other so-called "valve" metals are preferred as substrate materials).
microcosmicus
National Hazard

Posts: 287
Registered: 31-12-2007
Member Is Offline

Mood: spin up

@jpsmith123
In that case, what about stainless steel --- an oxide coating is what
makes it stainless, after all. Or is titanium oxide more resistant to
the stuff found in chlorate cells than chromium oxide? Diamond in a
SS substrate is quite easy to find in the form of diamond files, laps,
knife sharpeners, etc.

Duh -- using the stuff as an anode would automatically anodize it,
wouldn't it

[Edited on 8-1-2008 by microcosmicus]
12AX7
Post Harlot

Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline

Mood: informative

I'm learning every day, more and more, just how fucking resilient TiO2 is. Even to fluorides. . .

Stainless does not compare, period.

Tim

Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

Here's another interesting paper.

This paper describes some diamond coated anodes. Note the current densities they tested them at.

"However until now, diamond has not been introduced in electrochemical applications because of the limited availability of diamond for large-area electrodes. In the last years large-area chemical vapour deposition (CVD) of polycrystalline diamond films has been developed, yielding deposition areas of up to 0.3 m2 on metallic and ceramic substrates. These boron doped conductive diamond electrodes are semiconductor electrodes with a
microcrystalline structure and comparatively rough surfaces. Diamond-coated electrodes are chemically, mechanically and thermally very resistant (4) and show no significant corrosion even under high electrochemical load (5, 6). Galvanostatic investigations show no detectable changes of the electrodes for example after several hours in a solution of NaF in concentrated nitric acid at 50 °C (6) or in sulphuric acid (7). Over several weeks at 2 to 10 A cm-2 and thousands of Ah cm-2 the electrochemical activity of these diamond electrodes remains also constant in contrast to other conventional carbon electrodes (8)."

Attachment: Paper.pdf (2MB)

Nixie
National Hazard

Posts: 490
Registered: 12-12-2006
Member Is Offline

Mood: ?

What is the maximum temperature diamond can withstand in air for a prolonged period of time? I platinum-plated my tunsten plasma electrodes, but I'm wondering if diamond would last longer or allow a higher temperature.

[Edited on 8-1-2008 by Nixie]

\"Good is a product of the ethical and spiritual artistry of individuals; it cannot be mass-produced.\" --Aldous Huxley
jpsmith123
International Hazard

Posts: 757
Registered: 24-6-2005
Member Is Offline

Mood: No Mood

IIRC it starts to oxidize around 700 C or something like that, so you're probably better off with platinum.

What'd you do, electroplate the platinum onto the electrodes?
Pages:  1    3  4

 Sciencemadness Discussion Board » Special topics » Technochemistry » Forget everything else, diamond is the answer! Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Detritus   » Test Forum