For a long time, diamond has been the undisputed king of hardness. We’ve all heard “hard as a diamond,” and it’s true; diamond is the hardest known natural material. However, what many don’t know is that while diamonds are incredibly hard, they’re also quite brittle. One sharp blow can cause a diamond to shatter. This inherent fragility has always been a trade-off in the world of superhard crystalline materials: high hardness often means low toughness.
But, what if you could have a material that’s not only harder than diamond but also incredibly resistant to breaking? That’s exactly what a team of Chinese scientists has achieved!
Researchers led by Academician Tian Yongjun from Yanshan University have developed a revolutionary new glass material, named AM-III, that is not just the hardest but also the strongest glass ever created. Remarkably, AM-III can even scratch diamond, a feat previously considered impossible for any other glass material. But unlike diamonds, AM-III is also tough and resistant to shattering.
Academician Tian has a long history of groundbreaking work in the field of superhard materials. For instance, back in 2013, his team synthesized a nano-twinned cubic boron nitride harder than diamond, a discovery that made the pages of the prestigious journal Nature.
What sets AM-III apart is its unique amorphous, or glass-like, structure. Unlike diamond’s highly structured crystalline lattice, AM-III is more disordered. This unique arrangement gives the material a key advantage: its hardness is uniform in all directions, making it less susceptible to cracking. Diamond, on the other hand, is anisotropic, meaning it has “weak spots” due to directional differences in its structure. AM-III, being amorphous, neatly sidesteps that weakness.
Testing shows AM-III boasts a Vickers hardness of approximately 113 GPa, easily scratching the 103 GPa of single-crystal diamond. Furthermore, this remarkable glass can withstand pressures of around 70 GPa without fracturing, showcasing its unparalleled strength and hardness. Incredibly, AM-III isn’t just harder and stronger; it’s also a semiconductor. Its band gap, which is crucial for electronic applications, falls within the 1.5 to 2.2 eV range, comparable to the commonly used amorphous silicon film. This dual nature – superior mechanical properties and semiconducting capability – positions AM-III for potential breakthroughs in solar energy, specifically photovoltaic applications.
The secret to diamond’s hardness lies in its incredibly tight tetrahedral carbon structure, where all the electrons participate in covalent bonding. This lack of free electrons also explains why diamond is not conductive. AM-III, with its unique glass structure and powerful properties, is truly a game changer. It represents a monumental leap forward in materials science and has the potential to reshape numerous industries in the near future.
