[School project] Making diamond

[Angelino10]

Hey there,

First of all I want to apologize for my English, haha.

So for a project I came up with the idea of making diamond. It sounds a bit impossible, but I've found some good theories (and proven) experiments. 1 is with pure alcohol, and the other one is about making diamond with a blowtorch. I've found the last one the most interesting, mostly because it's relatively simple to do..

Okay, so here's the link of the video with the blowtorch: http://www.bbc.co.uk/news/science-environment-14505109

Some things I noticed in that documentary:
1. It's an ethyl-blowtorch (I hope that's the English way of writing it..). So probably it's only mixed with pure oxygen, to get a good mixture for the flame. But maybe it's mixed with other elements?
2. The little 'iron' plate under the flame is probably graphite or platinum, because it has to withstand huge temperatures (min. 2500 C*). I thought of graphite, because it can withstand this huge temperature + It's made out of C-atoms, so maybe that's better for making diamond?
3. There seems to be some kind of cooling-system underneath the flame and the plate. This could just be cold water?

So I've got some questions, which I can hope some of you could answer:
1. Where do you guys think the plate with the flame is made off?
2. Do the C-atoms from the plate produce the diamond or from the flame itself?
3. Could it really be an ethyl-blowtorch, or could it be something else?
4. Could someone explain the chemical reactions that are finding place in this documentary. Because I still got many question marks.
5. Is it only ethyl+oxygen or is something else blended trough the gas-mixture.

Maybe you guys know a better way to produce diamond. Feel free to let me know, because at this moment I'm a bit stuck (Reason why I'm on an American site).

Thanks a lot for helping me! I know it's a lot to ask for, so pardon me for that!

 

[mikegem]

Hey there,

First of all I want to apologize for my English, haha.

So for a project I came up with the idea of making diamond. It sounds a bit impossible, but I've found some good theories (and proven) experiments. 1 is with pure alcohol, and the other one is about making diamond with a blowtorch. I've found the last one the most interesting, mostly because it's relatively simple to do..

Okay, so here's the link of the video with the blowtorch: http://www.bbc.co.uk/news/science-environment-14505109

Some things I noticed in that documentary:
1. It's an ethyl-blowtorch (I hope that's the English way of writing it..). So probably it's only mixed with pure oxygen, to get a good mixture for the flame. But maybe it's mixed with other elements?
2. The little 'iron' plate under the flame is probably graphite or platinum, because it has to withstand huge temperatures (min. 2500 C*). I thought of graphite, because it can withstand this huge temperature + It's made out of C-atoms, so maybe that's better for making diamond?
3. There seems to be some kind of cooling-system underneath the flame and the plate. This could just be cold water?

So I've got some questions, which I can hope some of you could answer:
1. Where do you guys think the plate with the flame is made off?
2. Do the C-atoms from the plate produce the diamond or from the flame itself?
3. Could it really be an ethyl-blowtorch, or could it be something else?
4. Could someone explain the chemical reactions that are finding place in this documentary. Because I still got many question marks.
5. Is it only ethyl+oxygen or is something else blended trough the gas-mixture.

Maybe you guys know a better way to produce diamond. Feel free to let me know, because at this moment I'm a bit stuck (Reason why I'm on an American site).

Thanks a lot for helping me! I know it's a lot to ask for, so pardon me for that!

Hi -

I have over 25 years of experience in diamond synthesis by various deposition methods, including flame deposition.

This is a project that you can do. The BBC reporter is using a welding torch, fueled by oxygen and acetylene, the normal gases used for welding steel with a torch. You do not need high purity gases, the normal welding grade gases will work.

The substrate (the surface you grow the diamond on) must be cooled, and there is a cooling block in the video. Without cooling, the substrate would be destroyed, and the temperature would be too high to allow diamond to grow. You can make a cooling block out of aluminum or copper. Drill holes in it and make sure there is a continuous flow of cooling water through the block so it can keep the substrate within the temperature range that will allow diamond to grow. In general, keep the substrate between 600°C and 1000°C.

For substrate materials, I can suggest tungsten, molybdenum (metals), silicon carbide, silicon nitride (ceramics) or graphite. You could also use copper, which will allow diamond growth, but the diamond will not stick to it, so it will detach and blow away very easily. The metals and ceramics are good because you can easily clamp them to your cooling block. You will have to clamp the substrate to the cooling block because there has to be a good heat transfer path between the substrate and the cooling block, otherwise the substrate will overheat. Put the clamps outside of the flame zone, or they will be destroyed. Do not use steel or any iron-containing alloy, because iron grows graphite, not diamond.

You can also use graphite, which is cheap and easy to clamp to the cooling block, and resists thermal shock very well. If you do, you should rub a little bit of diamond dust onto the surface before deposition. Wash away the excess dust with water and let the graphite dry. Use diamond abrasive powder (1 micron or less in diameter). The residual diamond dust acts as seeds for diamond growth. You can grow diamond on unseeded graphite, but it takes many hours to get the diamond growth to begin (this is called the nucleation phase). If you have a few diamond particles on the substrate, the diamond growth starts immediately.

The gas mixture ratio is somewhat critical, but you can set it by flame appearance with experience. If you have access to mass flow controllers to regulate the gas flow, you will get more consistent results. The position of the substrate in the flame is important also. In general, you want to adjust the flame so it has a long blue inner cone, with no yellow appearance. Then you want to clamp the torch so the blue inner cone sort of splashes on the substrate surface about half-way along the blue inner cone's length.

Safety - If you have not used a gas welding torch before, get someone who has experience to teach you how. Oxygen and acetylene mixtures can detonate with enormous force, so please get experienced help to teach you how to use this equipment. When you set up the torch, set it up at an angle to the substrate so that the hot gases will exit away from the torch. Don't let the torch overheat - again, someone with welding experience can guide you.

You should use a torch tip with a single hole. There are multiple-hole torch tips (in the US, they're called 'rosebuds'), and they won't work for this. I have used a #6 tip (don't know what this would correspond to outside the US, sorry).

I'd suggest you Google "diamond deposition" and "combustion" or "flame" to find lots of literature that can help you with gas mixtures and other experimental details.

This is a totally feasible project. On my honeymoon years ago, I used a welding torch, a sheet of copper, and a bucket of water (for cooling the copper) to make a few small sparkling diamonds for my wife in the basement mechanical shop of a friend's house in Montana. It worked perfectly, and the memory still makes her smile from time to time.

Have fun, don't blow yourself up or burn your house down. Good luck!

 

[mikegem]

And I forgot to answer your specific points;

1. Oxygen and acetylene, no other gases needed. People have tried methane/oxygen, ethylene/oxygen and methylacetylene/oxygen but none of these works nearly as well as acetylene/oxygen. It's probably the very high flame temperature that results in high concentrations of reactive atomic hydrogen, which are important for diamond growth.

2. See my prior post for growth surface materials. The substrate is cooled so it doesn't get hotter than about 1000°C, usually less than that.

3. Cooling block, with heat removed by water flowing through the block.

Your questions:

1. See my prior post for growth surface (substrate) materials.

2. C-atoms are provided by the flame.

3. Acetylene works much better than any other gas I've used or seen tried by others.

4. The chemistry is complex and not completely understood. I'd suggest a Google search on "diamond deposition combustion chemistry" to find some of the literature that discusses the chemistry.

5. You can add trace gases like nitrogen or diborane to change the properties of the diamond somewhat. For example, if you add a boron source (like diborane), the diamond becomes an electrical conductor (a p-type semiconductor, to be specific).

Good luck!

 

[Angelino10]

Hey,

Thanks a lot for your quick reply! It is very useful, and I'm glad that somebody is finally saying that it IS possible. So I'll do some more research today and maybe some more questions will pop-up, but I think you explained everything quite well already.

Maybe in the actual process the next few months I'll have some questions, I'm happy that I found someone who can answer my questions.

So I guess you'll here back from me, if that's okay with you of course!

Thanks!edit: Oh and by the way. When you use a graphite plate, isn't there going to be any graphite-forming instead of diamond? Because you said if you rub a little of diamond dust on it, these will expand in growth, but graphite is also made out of C-atoms, so won't these grow too? Sorry I'm not the best in science.

 

[mikegem]

Hey,


edit: Oh and by the way. When you use a graphite plate, isn't there going to be any graphite-forming instead of diamond? Because you said if you rub a little of diamond dust on it, these will expand in growth, but graphite is also made out of C-atoms, so won't these grow too? Sorry I'm not the best in science.

That's the strange thing about diamond chemical vapor depositon processes - they make diamond even under conditions in which graphite is the more stable carbon species. What happens in general is that carbon atoms that do form graphite react with the surrounding gases and get converted back to gaseous hydrocarbons, but a few carbon atoms form diamond, which is resistant to chemical attack and so stays around to grow. Technically, this is called growing a species (diamond) in its region of thermodynamic instability by using chemical kinetics to get around the problem that the stable species (graphite) is the more likely one to form.

 

[Angelino10]

Thanks a lot I think i get it now!

 

[YummyFur]

Terrific post mikegem.

For some reason it looks like something from a Southpark episode. I can see Cartman on his deathbed saying 'rosebuds'.

 

[Angelino10]

He's trolling?

 

[YummyFur]

trolling? for what purpose. Quite the contrary, I found mikegems post fascinating and for an expert on this topic to take the time to so thoroughly answer a student was a joy to behold and most gracious too.

There are many levels that one can enjoy a thread. For you there are the facts that you wished to know for a specific purpose. As for me, I just stumbled upon it and I got drawn into the elaborate detail of mikegem's post. For me there was much satisfaction to be had by appreciating the mind of mikegem. I imagined that he would get a kick out of knowing that he's probably the only person in the world who would bother to so elaborately answer your question. I found it a very human interaction. In a way it's slightly surreal because the world has become so impersonal.

It's the little things like this that make life worth living.

You know, that 13 billion years ago there was a cloud of hydrogen atoms and somehow it condensed into a computer and you looking at the computer. For me this is a never ending source of wonder and amazement. The hydrogen atoms got rerranged into you. And now you are going to rearrange some carbon atoms into diamonds.
I forgot to mention that my favourite part of the bbc video was at the end because the person testing the crystals clearly did not believe they would be diamonds and you could see that he was really amazed.

 

[Angelino10]

You are very right, I am really really, thankful, I hope I made that clear in my replies. I really did not expect a reply which contains this amount of information.

I have to say that I read your post wrong. I saw horrific instead of terrific. Like I said before; my English isn't what it should be. I hope I didn't say something misplaced, I really am thankful.

And Yeh it truly is amazing that I'm going to make diamond. I'm really excited for a school project. That really is something, haha. I'll let you guys know how the experiment went!

 

[Angelino10]

Hey there. We're about to start the project, but we were wondering about the graphite substrate material. How thick and large does this needs to be? 10x10 cm surface and 3 cm thickness or something? I really hope you're still on this forum!
Thanks a lot.

 

[Angelino10]

In your explanation above, you said you used a welding torch in your friend's basement. Does that mean, that we don't have to use a acytelene torch?

 

[Borek]

Acetylene torch is used for welding.

 

[Angelino10]

It is indeed, yet mikegem advised me to use this gas. Other websites advise it too.

 

[Borek]

In your explanation above, you said you used a welding torch in your friend's basement. Does that mean, that we don't have to use a acytelene torch?

To be honest, I don't understand what the problem is. If welding torch uses acetylene it is the same thing - so what you wrote is basically "you said you used an acetylene torch, does that mean, that we don't have to use an acetylene torch?" Either my English fails me, or you are confusing something big.

 

[Angelino10]

Haha sorry you're totally right. I got a bit confused! I saw a welding torch as a torch with 'normal gases'. But an acytelene torch is a welding torch too of course. Excuse me for my stupidness.

 

[mikegem]

Hi - Replying to an email alert I received of your posting. I don't routinely check this board.

I would try graphite with a thickness 5mm or greater. This will do two things: first, it will provide good lateral heat transfer, which will tend to reduce the peak temperature (the "hot spot" problem), and second, it will give enough mechanical strength to resist warping due to the stress at the interface between the diamond and the graphite.

CVD diamond films (like any other CVD-made material) have high intrinsic stresses. You can see this easily when you deposit a thin diamond film on silicon, then etch the silicon away - the diamond film curls up due to intrinsic stress. It's possible to minimize this stress, but it requires precision process control (expensive). Typically, minimizing stress in diamond films is done by time-varying carbon concentration and temperature. It can also be done by doing an interrupted deposition in which you deposit for awhile, then do a transient increase in carbon concentration to produce additional nucleation sites. The stress profile tends to be reset to low values during the nucleation phase.

Will check in from time to time to see how things are going. The email post alert does reach me. Good luck!

 

[mikegem]

I can recommend a couple of papers for you. One is a 2011 review of diamond CVD technologies, including combustion synthesis. The other is a 2004 paper on increasing the surface area of combustion-deposited diamond films by scanning the flame over the substrate. They might have some details that would be of use to you. If you do not have access to these papers through your school, email me at diamonds94028*removespamblock*@yahoo.com and I'll get them to you.

A review of diamond synthesis by CVD processes, Schwander & Partes, Diamond and Related Materials, 20(2011), 1287-1301 (doi:10.1016/j.diamond.2011.08.005)

Enlargement of the diamond deposition area in combustion flame method by traversing substrate. Thin Solid Films, 457(1), 217–223, 2004. doi:10.1016/j.tsf.2003.12.042

 

[mikegem]

@YummyFur -

One of the fun events in my career as a diamond CVD critter involved getting my wife a diamond for her engagement ring. This was years ago, before I and others had shown that you can use CVD methods to make single-crystal diamonds of gem size and quality.

I was pretty sure I could make her a diamond, and given that, I was loathe to pay the going rate for a natural diamond! "Just a couple more months, and I can make you a diamond" - well, those couple of months stretched out, and I finally went to a diamond dealer in San Francisco and bought a loose diamond to be mounted in her ring. I took along a 122 ct. chunk of CVD diamond just for fun, and showed it to the diamond dealer after I'd bought my diamond. He was very polite, didn't laugh in my face, but clearly didn't believe me. I asked him to test it with his diamond tester ( a little thermal conductivity tester that gives a yes/no answer to whether it's diamond based on the thermal conductivity). He did, and it of course indicated "diamond". He turned very pale, and called his brother over to see the result. I told them I'd made the material in my lab, which set off an hour's conversation about how I did it. In the end, he gave me a 50% discount on the diamond, which paid for part of our honeymoon. Working the field of diamonds has always been interesting.

 

[Angelino10]

Hey mikegem,

Thanks a lot for your replies. It means a lot to me! English is not my native language, so some of the terms you use are not clear to us. Like what do you mean with the diamond films. Do you mean there will form a small layer of diamond on top of the graphite? Or do you use it as an example?
It would be really nice if you could explain it in "Diamond deposition for dummies" language. I really appreciate the effort you're putting into your posts! I'll read the articles this evening, maybe that will help too in understanding this difficult topic.

Thanks again!

 

[Angelino10]

Dear Mike,

I have tried to obtain those articles you mentioned, but I really can't find them. I'll contact you on that email you've mentioned in your reply. If it's too much trouble to get them then that's alright, I realize that I've been asking a lot!

Anyways. I didn't have a lot of time yet to really concentrate on this subject, but I really have to get started. I read this on wikipedia.
"Hydrogen is essential because it selectively etches off non-diamond carbon".

What do they mean with selectively etche off. Do they mean what you previously said:
"What happens in general is that carbon atoms that do form graphite react with the surrounding gases and get converted back to gaseous hydrocarbons, but a few carbon atoms form diamond, which is resistant to chemical attack and so stays around to grow".

Also why is the graphite converting back into gaseous hydrocarbons. What makes the diamond resistant to chemical attack. Is there a term around this phenomenon, so that I can search for more information about this? And why isn't the graphite plate itself converting into gaseous hydrocarbons?

Also you said: "The residual diamond dust acts as seeds for diamond growth." Does this mean that the seeds will expand in growth, because of the specific diamond structure which will be expended? So this means that there is a layer full of structures which can be expanded instead of no structure at all.

Thanks a lot! Again!
I'll be waiting patiently :)

 

[Angelino10]

Which sort of CVD are we doing actually. is it HFCVD?

Edit:
By the way, isn't it possible to use the cooling block as the substrate material. Or will it overheat?Edit:

I've read an article that says that the graphite molecules contain SP2-bonds. These bonds will be hydrogenated by the atomic hydrogen in the flame. This leads to sp3-bonds. So they're actually saying that the graphite which is formed will be 'transformed' into diamond eventually. Is this true? It's a source from the year 2000, so I don't know to what extent I can believe it.

 

[Angelino10]

How do I need to see the process from a carbon-containing radical to diamond? The carbon atoms become radicals by the heat of the flame and then they'll crash into the substrate. Does this mean that they'll simply bond with the existing diamond structure?