Ceramic kitchen knives

Some of the ceramic knife companies put a chunk of metal in the handle for detection purposes. Karl

you mean Beryllium?

I think he means Beryllium Oxide. ...lew...

On Tue, 18 Nov 2008 23:00:23 -0500, the infamous "Ed Huntress" scrawled the following:

And Cubic Zirconia is the trade name of one manmade diamond.

Yeah, for kicks. I have a Latin book you might enjoy hearing about. _How to Insult, Abuse, and Insinuate in Classical Latin_. ;)

-- Latin: It's not just for geniuses any more.

On Wed, 19 Nov 2008 00:04:47 -0500, the infamous "Ed Huntress" scrawled the following:

Right, and now black. The black ceramic knives are sinister looking. Very cool. ;)

-- Latin: It's not just for geniuses any more.

Uh, not that I know of. It's the name of an *artificial* diamond. It isn't diamond, manmade or otherwise. It isn't even carbon.

My son probably would enjoy that.

-- Ed Huntress

Are you sure they're zirconia? Black is usually aluminum oxide. In high-performance engineering applications, black may be silicon nitride.

I'll bet they're aluminum oxide (alumina).

-- Ed Huntress

my aluminium oxide blasting medium is brown. my silicon carbide blasting medium is black.

does al2o3 come in black too, and is it harder than brown al2o3?

Nope, It is Zirconium Carbide. They press the blades from Zirconium Oxide powder, Then they fire them at 14-1500 degrees for a few hours. These blades will be white at this time,if you wanted a white ceramic this is what you would get. If you wanted a black blade they run it through a second process called hot isostatic pressing. During this process the zirconium oxide changes to zirconium carbide, and you now have a black blade. The trade off it that the black blades are a bit stronger than the white ones BUT they don't hold an edge as long.

It comes in black, but I don't know if it's harder. IIRC it's tougher. There also is white AlOx, and pink.

The black, if my vague and fleabitten memory still works, contains small amounts of some ferrous compound.

-- Ed Huntress

Wow, HIPping is pretty fancy for a knife blade. That used to be reserved for things like jet turbine blades.

Where does the carbon come from to react with the zirconium oxide?

-- Ed Huntress

On Wed, 19 Nov 2008 15:41:32 -0500 in rec.crafts.metalworking, "Ed Huntress" wrote,

"Artificial" is pretty much just another word for "man-made". I would call it imitation diamond or diamond substitute.

I think thats called "paste" in the jewlery business. :-) ...lew...

Or Saphire in the crystal form. Al O 2 3 ...lew...

Man-made diamond, like GE's crystalline diamond used for diamond compact tools, and the vapor-deposited synthetic diamond used for coating tools, is real diamond. Chemically, it's indistinguishable from natural diamond. It's carbon, and it's just as hard as natural diamond.

Cubic zirconia and other artificial diamonds are not diamonds at all. They're completely different compounds, and they're somewhat softer than diamond. Zirconia, for example, is zirconium dioxide.

Now that man-made, or synthetic diamonds are so common, it's good to distinguish them from the artificial stones that only *look* like diamonds. The synthetics, again, are real diamonds. They can even make some gem-quality synthetic diamonds today.

-- Ed Huntress

Yup, BeO. Harmless unless you grind it up and breath it in.

But then drill rod is harmless unless you do something like sharpen it to a point and plunge it into your eye.

Best regards, Spehro Pefhany

Here's an interesting article about synthetic vapor-deposition diamonds:

They are producing gem quality up to 34 carat! With an improved process that will allow much larger "... to kilocarat diamonds of high optical quality". De Beers must be having nightmares!

Astonishingly: " ...600 tonnes of synthetic diamonds are produced each year for industrial use alone ..."

Bob

I think so. This sounds more like the beryllium ceramic used for hybrid integrated circuits at one time.

Enjoy, DoN.

YES, yes, yes, that's what I was thinking! I knew I must have been off-base on that.

Thanks for the correction!

Jon