Ask A Scientist© Chemistry Archive

name        Eric S.
status      student
age         20s

Question -  I was looking for information in your general science
archives about the hardness of borazon and I came across this:


name       Lance
status     other
Question - Can a substance be harder than diamond?
------------------------------------------------
Yes. There is a substance known as borazon, which is a compound of
alternating boron and nitrogen atoms arranged in the same manner as the
carbon atoms of diamond, that is actually harder then diamond.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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Hello,
Diamond is the hardest KNOWN substance. Unless a material scientist
corrects me otherwise, I would say that it may become possible in time
to make harder materials.

One point to keep in mind is that material properties such as "hardness"
are also dependent on other factors such as temperature. I do not know,
for example, if diamond is still the hardest known substance, say, at
low temperatures. At high temperatures diamond turns into graphite and
thus you do not have diamond anymore. At those temperatures, there are
many other materials, principally ceramics and metals that would be
harder than graphite.

AK
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Which answer is correct? Are there certain temperatures and pressures at
which borazon exceeds the hardness of diamond. I am not concerned with
comparing the diamond a

The information I am able to find indicates that cubic boron nitride,
produced by GE under the name "Borazon"
(http://www.geplastics.com/superabrasives/product/cbn/index.html), is
"almost" as hard as diamond. I did not find any numerical hardness rating.

You will find as you go through the AAS archives that there are many
conflicting answers. Scientists are not omniscient, and they do not always
agree.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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