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The new material is a boron-nitrogen nano-compound, which means it consists of only a few nanometer-scale boron nitrogen grains, rather than continuous crystals. Although scientists have reported this material before, boron-nitrogen compounds are very unstable at high temperatures, which is a major drawback in the industry.
Natalia Dubrovinskaia of Heidelberg University and Bayreuth University in Germany said: "The biggest breakthrough is that this hard material is stable at the same time, so it can be used for cutting and drilling." Dubrovinskaia was published on March 8th, "Applied Physics Letters". The first author of the article.
For many materials composed of grains, there is an optimum grain size, which is usually in the nanometer range. Along the way, Dubrovinskaia and colleagues conducted a number of experiments on a range of polycrystalline and nanocrystalline boron nitride compounds. This includes measuring the "Vickers hardness" of a sample. For very hard materials, the value is generally around several GPa, while the hardness of single crystal diamond is about 100 GPa.
The Dubrovinskaia group found that the hardest boron-nitrogen compound has a hardness of 85 GPa and a grain size of 14 nm, which remains thermally stable at 1600 K. The hardness of this material comes from two aspects: the effect of nanometer size and the composition of the two phases. Prior to this, it was known that the material having the closest hardness to diamond was cubic boron nitride, a single crystal phase having a Vickers hardness of 50 GPa. There is a 50GPa gap between it and diamond.
Dubrovinskaia said: "This gap has been filled by adjusting the size and composition of the grains. They will undoubtedly play an extremely important role in industry."
Scientists find a non-carbon material with a hardness close to that of diamond
Science and Technology Development Center of the Ministry of Education, March 30, 2007: A group of scientists discovered the first carbon-free material with a hardness close to that of diamond. This achievement has important implications for technologies and industries that rely on diamond for cutting and drilling.