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Electrodeposition of diamonds

 

Q. Dear Sir,

I am teacher in a private training school. Very recently one of my student has put a question which gave me many nights of thinking. But I was unable to get the real answer to that.

The question is, "How to deposit diamond on metal like stainless steel or aluminium or any other metal". It will be highly informative if somebody provides the answer in a very simple manner and the procedure to be followed.

Regards,

Prasanna Kumar.G.V
Tutor - Bangalore, Karnataka, India

A. Hi, Prasanna. The basic principle is you set up a slurry of tiny diamond particles in a nickel plating bath or electroless nickel plating bath and the diamonds are occluded (encapsulated) as the nickel deposit is laid down. At one time General Electric offered industrial diamonds that were pre-plated with electroless nickel to facilitate the process. Whether this product line is still available from General Electric, I don't know; and whether it actually helps for the diamonds to be pre-plated, I don't know either. But if you can reach someone in this area of General Electric perhaps they can help you. Nano-size diamonds now are available from Russia, which improves the economy I understand.

There are dozens of important and broad patents in this technology, so one approach might be to go to someone who licenses their patented processes.

Good luck, and regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Prasanna, if I recall correctly, carbon is found in three distinct forms: graphitic, diamond and fullerene. Diamond has a peculiar carbon atom crystal structure which has been nearly impossible to synthesize. Using extremely high pressures and temperatures, scientists at MIT and in Russia have synthesized it to tiny crystals and nearly pure form. So, at this point, no one has figured out how to plate pure diamonds. Having said that, there are processes that have been commercialized for coating diamond-like-carbon (DLC) structures, either hydrogenated (i.e., with a hydrogen atom attached) or intrinsic (i.e., with only carbon atoms). These coatings are typically deposited by vaporizing carbon or decomposing carbon compounds in vacuum under active plasma. Sometimes RF or microwave electromagnetic fields are used to enhance the process. If you are looking for literature, look for DLCs. I do not know if this is a simple enough answer.

Mandar Sunthankar
- Fort Collins, Colorado

A. Diamond can be deposited in a number of ways. These include physical vapor deposition, chemical vapor deposition, and at least one later technique. Numerous articles have been written on the subject, in journals such as Vacuum, Advanced Coatings and Surface Technology, Thin Films, and the Journal of Vacuum Science. For details of the deposition processes, I suggest you look at the journal articles.

Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover
San Diego, California

A. Diamond is just one form of carbon; as stated above there are other forms, namely graphite and fullerene. The important thing about diamond is its structure, it is sp3 carbon, whilst graphite is sp2. Due to this atomic geometry, diamond forms a 3 dimensional structure whilst graphite forms a two dimensional plate-like structure. This is why graphite is such a good dry lubricant; the planes slide over each other. Diamond, on the other hand, is rubbish as a lubricant. I cannot discuss fullerene because I do not know that much about it and there is bound to be better people out there than me!

Diamond is a very good electrical insulator, whilst graphite is a reasonably good conductor. Consequently you cannot electrodeposit diamond straight onto a surface. However, you can co-deposit it by making a fine suspension of diamond "powder". One sneaky way I was told about is to make a suspension of diamond in a metal plating solution and horizontally rotate the workpiece at the bottom of a container and deposit or electrodeposit a metal onto it. Some metals can be deposited without electricity ("Electroless"). The real trick to it is to make the density of the plating solution similar to the microdensity of the diamond particles. This can be achieved by mixing the diamonds with a suitable surfactant. The rotating workpiece acts both as the cathode and a means of stirring. Let good old gravity drop the diamond particles onto the workpiece. Obviously this will not work in space unless you have got synthetic gravity! If the rate of agitation is just right, the rate of diamond deposition can be easily controlled. This technique is used with nickel (both electrolytic and electroless).

Another way of coating things in diamond is to use vacuum techniques. When carbon is "plasmaised" it forms both sp2 and sp3 carbon. The two types can be separated by a strong magnetic field and the workpiece located in the area where the sp3 carbon appears. This separation method is not absolutely perfect and that is why you get DLC or "diamond like carbon". The better the separation, obviously the better the diamond like coating. Fullerene can be made by using an electric arc system, but I don't know much about that.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

A. Electro plating of diamond to stainless substrate can be achieved by first using a nickel strike on the stainless. The stainless can be diamond plated by placing the part in diamond powder held in porous ceramic, this submerged in the plating bath. Plating chemistry is pumped through the diamond and stone around the product parts under current.

Robert Sachs
- Morrisburg, Ontario

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A. Dear Prasanna,

It is possible to deposit diamond thin films on a suitable substrate by a process called chemical vapour deposition. There are several techniques even in chemical vapour deposition (CVD) for e.g. Microwave CVD, Hot filament CVD etc.Each of the techniques differing only in the method by which the hydrogen plasma or atoms produced.The Technique is actually simple. A carbon feed gas generally methane dilute by hydrogen to approx. 1-2 mol %. is passed into the chamber. On entering the chamber it passes through a hot filament or Microwaves which essentially dissociates the hydrogen. and the hydrogen atoms abstracts the hydrogen from the methane forming the methyl radical.The substrate is placed 1 cm below the hot filament with the temperature of 2000 degrees C. The substrate is maintained at ~ 800 degrees. the metyl radical adds to the substrates and the film growth takes place. The choice of the substrate is very important. There are several factors to be taken care of unit cell parameters of the substrates must be similar to that of the diamond, the substrate must have low solubility for carbon, low diffusion for carbon.

About the question you asked, whether it is possible to coat diamond on stainless steel: yes , it is possible. However stainless steel has a large percentage of iron. and carbon diffuses considerably into iron and over that it also catalyses the formation of more graphitic carbon. This can be overcome by coating steel with chromium nitride. this is reported in the most recent issue of the journal diamond and related materials.

The method described above looks very simple but it is very difficult job. good understanding of the low vacuum techniques, mechanical drawing to sketch the setup to obtain is absolutely essential. these are just few of the things that is necessary.

Sreejith. K , BARC
- MUMBAI

On a solid surface it is possible to deposit diamond, is more valid diamond-like, film by a chemical method (CVD) at the expense of chemical hyperthermal reactions. Other path to the deposition diamond-like of a film by a method vacuum arc. The graphite is sputtered in a vacuum arc and the ions of Carbon with high energy are condensed on a surface, deriving diamond-like a film. The third path, this deposition of a diamond powder by a method sintering (hyperthermal pressing), galvanic method on the basis of a nickel or gas-therm by a method. Last methodologies will be used for manufacturing of a diamond tool.

Dr.Boris A.Eizner
- Israel
2006