For many years diamond has been considered the hardest material. Then it gave the first place to man-made nanomaterials that proved to be somewhat harder than the diamond. Recently researchers discovered a natural substance that is 58 percent tougher than diamond.
Together with his team Zicheng Pan at Shanghai Jiao Tong University analyzed two substances and noticed that the structure of wurtzite boron nitride is similar to that of diamond, but is composed of different atoms, while the mineral lonsdaleite, is composed of carbon atoms.
It is worth mentioning that diamond is made up of carbon atoms as well, but mineral lonsdaleite's atoms are arranged in a different shape.
Scientists simulated how the two substances withstand stress. They found that wurtzide boron nitride was able to withstand 18% more stress than diamond, while lonsdaleite 58% more. In case the same results will be registered with physical experiments, the two materials will prove to be much harder than any other substance.
The two substances are very rare in nature: lonsdaleite sometimes appears when meteorites containing graphite reach Earth and wurtzite boron nitride appears as a result of volcanic eruptions that generate extremely high temperatures and pressures, reports New Scientist.
If the physical experiments will show that wurtzite boron nitride is indeed harder than diamond it may replace the diamond, being more stable in oxygen at higher temperatures.
The features of the substance would allow placing the wurtzite boron nitride on the tips of cutting and drilling devices that operate at high temperatures. Besides wurtzite boron nitride could be used in making corrosion resistant films that are mounted on the surface of a space vehicle.
source:
http://www.infoniac.com/science/substance-harder-than-diamond.html
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