[atek3]

Anyone know if there would be any advantage to laying down a few thou of monocrystalline diamond on the blade of a ceramic knife? I don't really care about edge holding ability, just the ability to be an effective fighting knife?

I'm no expert on knives, so I'm curious to hear responses.

atek3

[Jim Watson]

May thy knife chip and shatter.

[PercyShelley]

In addition to diamonds being brittle, good luck making a noncrystalline edge of any significant length. It was only in the past several years that it became possible to make artificial diamonds that were big enough and consistent enough to make decent jewelry with.

It would, however, hold an edge like none other, since it would be impossible to abrade away unless you were fighting guys covered in industrial abrasives for some reason. Seeing as long-term edge retention is the single factor you do not care about, however, I've got to say that the concept's a bust.

[hso]

Not a good idea.

Ceramic has little lateral strength and regardless of this theoretical "monocrystalline diamond" coating the substrate ceramic would break easily. You'd be standing there with a high tech broken blade.

Fighting knives don't have to hold an edge like working knives. They're used for one thing and one thing only and therefore don't have to hold an edge forever.

[telomerase]

It was only in the past several years that it became possible to make artificial diamonds that were big enough and consistent enough to make decent jewelry with.

But he's just talking about coating, and GE has been coating big oil-drilling bits with diamond since the early 1980s.

[22-rimfire]

As far as I know, drilling bits do not have microcrystaline diamonds on them. They would drill to slowly and the "dust" wear off too quickly. The diamonds vary in size depending on the nature of the anticipated material to be drilled. Even fine (small carat) diamonds are still larger than you think; probably an eight inch across on the cutting surface.

[atek3]

"monocrystalline diamond" is not a theory... Basically a single diamond is grown around the blade using chemical vapor deposition (CVD). However, the diamond is only a few thousanths thick.

atek3

[CWL]

Adding diamonds to the blade of a knife is exactly like turning your knife surface into sandpaper or a file, Not only will this hinder cutting and penetration, but it will also clog-up like sandpaper. Don't think that's what you are looking for.

Microcrystalline diamond cuts by abrading, just like the grit on sandpaper. You can buy them in various sizes in a solution that can be sprayed onto surfaces for use as a polishing/cutting compound. They are sold by the carat, just like larger diamonds.

[atek3]

arg... not microcrystalline, not "diamonds", one diamond grown around the ceramic blade. It functions just like a regular knife by applying force to very small area and exceeding the strength of the material being cut. The advantage of a diamond is that a) it has a mohs hardness of 10, so nothing would dull it, and b) with the kinks worked out of the system you could grow an edge that would have a perfect 60 degree angle and no imperfections.

atek3

[Novus Collectus]

Well then atk3, why not coat the edge of a polymer blade with monocrystaline diamond then? There would be no need to worry about the blade breaking (unless the diamond does) and it would have a super sharp edge that will never dull.

[CWL]

How would you grow a single diamond along the edge of any knife? How would it be bonded to the blade material? Except for hardness, why would a 60 degree angle be good for cutting? Not that I believe it would be possible because the inherent crystalline shape of the diamond would prevent this, but even if it were possible, do you have access to a synthetic diamond manufacturing plant -one large enough to layer diamond material onto a blade and which wouldn't destroy the ceramic under the pressures and heat necessary to create a synthetic diamond?

This sounds like videogame dreaming, not practicality.

[Novus Collectus]

How would you grow a single diamond along the edge of any knife? How would it be bonded to the blade material? Except for hardness, why would a 60 degree angle be good for cutting? Not that I believe it would be possible because the inherent crystalline shape of the diamond would prevent this, but even if it were possible, do you have access to a synthetic diamond manufacturing plant -one large enough to layer diamond material onto a blade and which wouldn't destroy the ceramic under the pressures and heat necessary to create a synthetic diamond?

This sounds like videogame dreaming, not practicality. Already used on scapels. http://www.apollodiamond.com/

Chemical vapor deposition of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been either too expensive to implement or too difficult to make economical. CVD diamond growth typically occurs under low pressure (1 to 27 kPa) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate....


...The advantages to CVD diamond growth include the ability to grow diamond over large areas, the ability to grow diamond on a substrate, and the control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce diamond, the diamonds were typically very small free standing diamonds of varying sizes. With CVD diamond growth areas of greater than fifteen centimeters (six inches) diameter have been achieved and much larger areas are likely to be successfully coated with diamond in the future ...


.... Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond’s hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substratehttp://en.wikipedia.org/wiki/Chemical_vapor_deposition_of_diamond

[CWL]

Already used on scapels

Nah, those are actual teeny-weeny diamonds, take a look at some:
http://www.diamondsurgicalproducts.com/html/kniferepairs.html

Don't know about recent low-pressure chemical vapor advancements, but that's still growing multiple crystals over a surface -like sandpaper. The technology is not there yet, to manipulate the crystal structure of diamonds to grow a single crystal along a knife edge.

[hso]

Russian method of growing diamond like coatings using methane.

Still not viable for making knives.

[PercyShelley]

I assume you specified 60 degrees so that the blade angle would coincide with the crystal grain?

Anyhow, boron nitride is just as hard as diamond in certain allotropes. Does anyone know if that can be manufactured more readily into a blade shape?

[hso]

You've got to use whiskers with boron nitride to give it any strength.

[PercyShelley]

Ceramics have such strange properties.

So it goes. No lightsabers for us.