Carbon is one of the most amazing elements in nature, with chemical and physical properties that are different from other elements. With only 6 protons in its nucleus, carbon is the lightest element capable of forming complex chemical bonds. All known life forms are based on carbon, as carbon atoms can form chemical bonds with up to four atoms at a time.
Under high pressure, carbon can also combine with other carbon atoms to form a stable lattice structure. If the conditions are right, the carbon atoms can also form an extremely strong and super-hard structure called a diamond.
Although diamond is known to be the hardest substance in the world, there are actually 6 materials that are better than diamond. Of course, diamond is still one of the hardest natural materials on Earth, but it’s hard to compare with these six.
There are three substances on Earth that are not as hard as diamond, but are still worth mentioning because they work well in many ways. With the development of nanotechnology, along with a better understanding of modern materials at the nanoscale, we now realize that there are many metrics that can be used to evaluate the properties of materials. these extreme materials.
Let’s start with biology. Although spider silk looks very fragile, it is actually a very durable material. Its strength-to-weight ratio is far superior to traditional materials such as aluminum and iron, and at the same time it is very thin and sticky. Of all the spiders in the world, the Darwin’s bark spider’s silk is the strongest, 10 times stronger than synthetic Kevlar fibers.
Another natural substance called silicon carbide (usually in the form of moissanite) is only slightly harder than diamond. Silicon carbide particles have been produced on a large scale since 1893. Silicon and carbon belong to the same element family, and it is possible to form this extremely hard material at high pressures but relatively low temperatures through a process called sintering.
These materials are not only suitable for many situations requiring high stiffness such as brake pads, clutches, body armor, tank armor, etc., but also have excellent semiconductor properties, so they also play a role important role in the production of electronic components.
About 20 years ago, scientists first developed silicon nanospheres with diameters ranging from 2 nanometers to 50 nanometers. The most amazing thing is that these nanospheres are hollow and can not only self-assemble into spheres, but also interlock. It is also one of the hardest materials known to man, only slightly less than diamond in hardness.
Self-assembly is an extremely powerful tool in nature, but compared to synthetic materials, biomaterials are weaker in this respect. These self-assembled nanoparticles could be used to create custom materials such as better-performing water filters, more efficient solar cells, faster catalysts or electronics. However, the most ideal application scenario is a suit of armor that is “tailored” to the user’s body.
The most famous high hardness material
In fact, none of these materials can match the hardness of diamond. Of all the materials found or created on Earth, diamond is the seventh hardest material. While some natural (but very rare) and synthetic materials have surpassed diamond in hardness, in the impression of many people, diamond is still the substance with the highest hardness.
However, there are six materials that beat diamond in hardness.
No. 6, Wurtzite boron nitride
In addition to carbon, many other atoms or compounds can form crystals, and boron nitride is one of them. Boron and nitrogen occupy fifth and seventh positions respectively on the periodic table, and when these two elements combine, they can form many different compounds, including amorphous solids, crystalline hexagonal (similar to graphite), cubic crystal system (similar to diamond, but slightly less strong in structure), and wurtzite.
Of these, the last form is the most extreme and the material is also extremely sturdy. This material was formed during volcanic eruptions and so far only a very small amount has been found, so it is currently impossible for scientists to test its hardness experimentally. But the latest simulations show it can form a type of structure that is 18% harder than diamond.
Number 5, Lonsdaleit
Pictured are two diamonds recovered from the Popigai crater. On the left is pure diamond, on the right is a mixture of diamonds and a small amount of Lonsdaleite. If there is any Lonsdaleite stone without impurities, its strength and hardness will be many times better than pure diamond.
Real dead diamond is a cubic crystal, while Lonsdaleite is a hexagonal crystal system, its composition is similar to diamond but can be up to 58% harder than diamond. Therefore, people also call Lonsdaleite a hexagonal diamond (an allotropic form of carbon with a hexagonal lattice). In nature, it forms when meteorites containing graphite hit the Earth. The large amount of heat and pressure of the collision converted the graphite into a diamond, but the graphite’s hexagonal lattice structure was preserved. Lonsdaleite was first identified in 1967 in the Canyon Diablo meteorite, which appears to have very small crystals associated with diamonds.
Number 4, Dyneema
Dyneema is an extremely high molecular weight thermoplastic polyethylene polymer. Most of the molecules we know have only a few thousand atomic mass units, but the molecular chain of ultrahigh-molecular-weight polyethylene is extremely long, and the weight of a single molecule can be in the tens of millions atomic mass unit.
With such a long molecular chain, the intermolecular interactions will be greatly enhanced. In fact, the material has the highest impact strength of all known thermoplastics, is considered the strongest fibrous material in the world, outperforming all fasteners and zippers in the world. market, lighter than water and bulletproof.
No. 3, palladium microscopic glass
All physical materials have two important properties: strength and toughness; Strength is the force required to deform a material and toughness is the force required to break or break a material. Most ceramic materials are very durable, but their toughness is very poor, they are easily broken if clamped too tightly or accidentally dropped. Elastic materials like rubber, on the other hand, do not break easily, but they are very deformable and have extremely low stiffness.
Most glass materials are fragile, with high strength and low toughness. Even tempered glass like Pyrex glass or Corning glass is not strong enough as a material on its own. But in 2011, researchers invented a new type of microscopic glass, which contains five elements: phosphorus, silicon, germanium, silver and palladium. Among them, palladium can form shear bands, allowing the glass to be plastically deformed when it is impacted and will not be broken directly. The material is a combination of extreme strength and toughness that easily beats any steel and glass available and is also the hardest carbon-free material in the world.
No. 2, Buckypaper
Since the late 20th century, a material called carbon nanotubes has been known to be “harder than diamond”. The substance belongs to the hexagonal crystal system, the overall structure is elliptical, and its stability is better than any known structure. If you combine a large number of carbon nanotubes into a flat surface, you get a thin “paper” called buckypaper.
In addition to buckypaper, there is an equally hard structure called a buckyball, which is made up of 60 carbon atoms bonded together. Buckyball is also a natural material that can be formed in certain cosmic environments. Although Buckyball has been applied in the nano field, it has not yet achieved quantitative output, and temporarily has not shown its “talent” on a macro scale, so it is not included in the list. this book.
By comparison, each nanotube that makes up buckypaper is only 2 to 4 nanometers in diameter, but the structure is so strong that it can be incorporated into sheets of the material with larger areas. Its weight is only 10% of steel, but it is hundreds of times stronger. In addition, this material also has fire resistance, high efficiency of thermal conductivity, outstanding electromagnetic shielding ability, has rich application prospects in materials science, electronic components, military and even. even biology.
No. 1, Graphene
Finally, let’s consider a hexagonal lattice structure composed of carbon atoms – graphene, just one atom thick. After being successfully prepared, flake graphene is expected to become the most revolutionary material of the 21st century. Graphene is indeed the most basic structural component of carbon nanotubes and has a wide range of application situations. use.
At the same thickness, graphene is the strongest material known, with unparalleled thermal and electrical conductivity, light transmission approaching 100%. The 2010 Nobel Prize in Physics was awarded to Andrei Geim and Konstantin Novoselov for their experiments on graphene. To date, graphene remains the thinnest material we know of. And it took only six years for Game and Novoselov from research to award, which is one of the fastest records in physics.