Which is the harder substance?

Which is harder? Zircon-oxide used to make ceramic blades or diamonds? I’ve got some information that says “zircon oxide, which is harder than diamonds (so hard it registers beyond the Rockwell Scale)” But most information says that a diamond is the hardest substance known to man. Which is it?

From www.wikipedia.com -

Zircon has a hardness of (Mohs) 7.5. Diamond, of course, is 10. Diamonds are still the hardest occuring gemstone or whatever.

Zirconium Dioxide, what you are looking for, is a compound. I have no idea what its hardness is but it can not be compared to diamonds for that reason.

Or so I think, atleast.

Hopefully that is self explanatory.

Zircon oxide is short. It’s full name is Zirconium oxide (not that much longer)

I don’t think that’s true. The structure of the substance determines its hardness, not the substance’s components. Carbon has a hardness of 10 when in the form of a diamond, and 0.5 (!) as graphite.


Wear and scratching on the CZ or the diamond???

And are cubiczirconia and Zircon-oxide the same thing?

A check of several Google pages turned up the following:

Describing it as a corundum
More generally, corundums represent a family of electrofused aluminas that can be divided into three large groups :

• White corundums (“pure” alumina)
• Brown corundum (aluminas doped at 1.5% or 3% with TiO2)
• Solid solutions with corundum matrices among which zircon oxide corundums can be mentioned (25% of alumina and 42% of zircon oxide) and aluminium oxynitrides (AlON).

In Nature, corundum is the hardest mineral after diamond. Moreover, chemically inert and more or less fragile depending on its preparation, it has always been a polyvalent abrasive and remains the most commonly used today. It is also used as an aggregate in refractories for its mechanical resistance in heat, its dimensional stability, its chemical inertia and its electric resistivity.

A microceramics manufacturer

Zircon oxide ceramics is a ceramic material on the basis Z2O3 zircon oxide part-stabilized by highly pur with 3MolY2O. Characteristics: Density: 6,05 g/cm³
Hardness: 1300 HV
Pressure strength: 4000 N/mm²
Bending strength (blank): 1200 MPa

Zircon oxide ceramics is a dispersion ceramic(s) on the basis of part-stabilized zircon oxide and alumina, which leads to an increase of the firmness and/or facture toughness oppostie pure ZrO2. Characteristics: Density: 5,5 g/cm³
Hardness: 1300 HV
Bending strength (blank): 2400 MPa (1000°C: 800 MPa)

More details from this site

Aluminum Oxide, Al2O3 hardness 2100 HV
Zirconium oxide, ZrO2 -Y2O3 hardness 1300 HV
Silicon Carbide, LPSSiC hardness 2990 HV

This reference, but the site wouldn’t open up.

"Knives & Tools - compare prices, reviews and buy at NexTag - Price … Boker Infinity. Boker’s ceramic blades are constructed of zircon-oxide, which is hard as diamonds (so hard it registers beyond the Rockwell scale), resists wear …

[IRL](http://www.techshopper.com/ Knives___Tools~2701185z110z160z0zB11y8zmainz5-htm - 57k - )

So, it depends if we can take the sales statement of a knife dealer as scientifically true…
The other site lists Silicon carbide as harder yet!

I’d be pretty amazed at a zirconium oxide corundum ceramic that is harder than diamonds yet with tensile strength enough to function as a knife!

Hope someone can come up with more information.

Again, from a knife dealer…

We need “The Straight Dope!”

A rating of ceramic knives

Beyond the Rockwell scale, not the Mohs scale.
I think that’s where the confusion comes from.

I don’t think it’s harder than diamonds.

Ok, here:

“Cubic zirconia is relatively hard, at about 8.5 on Mohs scale nowhere near diamond, but much harder than most natural gems”

From: http://encyclopedia.thefreedictionary.com/Cubic%20zirconium

From the same site:

So CZ is the same as zirconium oxide, though not the same kind used in knives, but the hardness of both is 1300 HV, or 8.5 on the Mohs scale!

Wow, we did it! Thanks Zebra!

Speaking as chemist (Organic, not Inorganic however), I’m having trouble believing that anything could be harder than diamond, as it’s strength comes from the crystaline latice, which is damn near perfect in diamond. All of the carbons are sp3 hybridized and form a tetraheraonal structure. In graphite, however, the carbons are sp2 hybridized and are in sheets of hexagons, with an inherent aromaticity. The sheets are held together by nothing more than Vander Waals forces, which accounts for the softness. I don’t claim to know anything about zirconium oxide or cubic zirconium, other than it’s cheaper than diamonds and I like it better, but no one listens to me.

That sounds really dangerous…