Scientists Create First Non-Carbon Material with Near-Diamond Hardness

March 28, 2007 By Laura Mgrdichian feature

Research scientists have created the first non-carbon-based material with a hardness approaching that of diamond. Their work could have a significant impact on technologies and industries that rely on diamond as a cutting and drilling tool and abrasive.

The material is a boron nitride “nanocomposite.” This means that, rather than consisting of one large continuous crystal, it is made of crystalline boron-nitride grains that are each a few to several nanometers in size. Although research groups have previously reported boron carbonitride materials, claimed to be the second and third hardest materials after diamond, the particular versions, or “phases,” of those materials were unstable at high temperatures. In industry, this is a major drawback.

“The real breakthrough would be a bulk material that is hard, tough, and thermally stable, and thus ideal for cutting and drilling. We are the first to synthesize a bulk noncarbon material that fits this description,” said Natalia Dubrovinskaia, a researcher with the University of Heidelberg and the University of Bayreuth, both in Germany, to PhysOrg.com. Dubrovinskaia is the lead author of the paper describing the new material, which appears in the March 8 edition of Applied Physics Letters.

For many materials composed of crystalline grains, also referred to as polycrystalline materials, there is a grain size for which the material's hardness is optimized. This size is often in the nanometer range.

Along this line of thought, Dubrovinskaia and her colleagues synthesized and conducted several experiments on a series of polycrystalline and nanocrystalline phases of boron nitride. This characterization included measuring the samples' “Vickers hardness,” a test that assigns a hardness value to a material based on how readily it is indented by diamond. That value can be expressed in terms of the pressure applied by the diamond – using the pressure unit “pascal” – before it makes an indentation. For very hard materials that usually means billions of pascals (gigapascals, GPa). Single-crystal diamond, the hardest type, has a hardness of about 100 GPa.

The boron nitride nanocomposite synthesized by Dubrovinskaia and her group displayed a maximum hardness of 85 GPa at a grain size of about 14 nanometers, and is thermally stable up to 1600 degrees Kelvin (about 2400 degrees Fahrenheit). The material's hardness arises from two factors: the nanoscale-grain-size effect and each grain's two-phase composition. That is, each grain has a nanoscale crystalline structure and a sub-nanoscale structure. This complex composition significantly increases the bulk material's mechanical strength.

Prior to this research, the next hardest known material after single-crystal diamond was cubic boron nitride, a single-crystal phase of the material, which has a Vickers hardness of 50 GPa. That leaves a rather large 50 GPa gap.

“This gap can be filled by boron nitride nanocomposites, particularly by tuning their grain size and the compositional structure of the grains,” says Dubrovinskaia. “These materials may come to play an important role in industry.”

Citation: Natalia Dubrovinskaia, Vladimir L. Solozhenko, Nobuyoshi Miyajima, Vladimir Dmitriev, Oleksandr O. Kurakevych, and Leonid Dubrovinsky, “Superhard nanocomposite of dense polymorphs of boron nitride: Noncarbon material has reach diamond hardness.” Appl. Phys. Lett. 90, 101912 (2007)

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Snake skin inspired surfaces smash records, providing 40 percent friction reduction

Related Stories

Modeling how thin films break up

June 19, 2015

Excess surface energy from unsatisfied bonds is a significant driver of dimensional changes in thin-film materials, whether formation of holes, contracting edges, or run-away corners. In general, this break-up of a material ...

Diamond-like coatings save fuel

June 8, 2015

Coating engine components with hard carbon reduces friction to almost zero – a development that could save billions of liters of fuel worldwide every year. Now researchers have developed a new laser method to apply the ...

Graphene and diamonds prove a slippery combination

May 25, 2015

Scientists at the U.S. Department of Energy's Argonne National Laboratory have found a way to use tiny diamonds and graphene to give friction the slip, creating a new material combination that demonstrates the rare phenomenon ...

Sapphire talk enlivens guesswork over iPhone 6

July 27, 2014

Sapphire screens for the next iPhone? Sapphire is second only to diamond in hardness scratch-proof properties, used in making LEDs, missiles sensors, and on screens for luxury-tier phones. Last year, the budget-conscious ...

Recommended for you

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

Could stronger, tougher paper replace metal?

July 24, 2015

Researchers at the University of Maryland recently discovered that paper made of cellulose fibers is tougher and stronger the smaller the fibers get. For a long time, engineers have sought a material that is both strong (resistant ...

Changing the color of light

July 23, 2015

Researchers at the University of Delaware have received a $1 million grant from the W.M. Keck Foundation to explore a new idea that could improve solar cells, medical imaging and even cancer treatments. Simply put, they want ...

Wafer-thin material heralds future of wearable technology

July 27, 2015

UOW's Institute for Superconducting and Electronic Materials (ISEM) has successfully pioneered a way to construct a flexible, foldable and lightweight energy storage device that provides the building blocks for next-generation ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.