Chapter 1: The Quest for Hardness

You might think diamonds hold the title for the hardest natural substance, but there are actually six materials that surpass them in toughness.

Carbon is a remarkable element, unique in its chemical and physical characteristics. With just six protons, it is the lightest abundant element capable of forming a variety of complex bonds. All known life forms are based on carbon, thanks to its ability to bond with up to four other atoms simultaneously. The diverse geometries of these bonds allow carbon to self-assemble into a robust crystal lattice under specific high-pressure conditions. When conditions are optimal, carbon can crystallize into a solid structure known as a diamond.

While diamonds are renowned for their hardness, they are not the only strong material on Earth. In fact, there are six substances that exceed their hardness. The Darwin's bark spider produces the largest orb-type web of any spider species, and its silk is the strongest among all spider silks. A single strand can measure up to 82 feet, and if one were to circle the globe, it would weigh only about a pound (CARLES LALUEZA-FOX et al. 2010).

Honorable mentions include three terrestrial materials that, while not quite as hard as diamonds, possess impressive strength in various ways. With advancements in nanotechnology and a deeper understanding of modern materials at the nanoscale, we now appreciate that hardness is just one metric in evaluating materials.

Spider silk, particularly from Darwin's bark spider, is famous for its toughness, boasting a higher strength-to-weight ratio than conventional materials like aluminum or steel. Remarkably, this silk is ten times stronger than Kevlar. A pound of this silk could yield a strand long enough to encircle the Earth. Silicon carbide, often found as fragments of the mineral moissanite, is nearly as hard as diamonds.

Chapter 2: The Science of Strength

Silicon carbide is chemically composed of silicon and carbon, both of which share a family in the periodic table. Since its mass production began in 1893, silicon carbide has been synthesized and utilized for its hardness in various applications, including car brakes, bulletproof vests, and military armor. Additionally, it has valuable semiconductor properties for electronics.

Innovative ordered pillar arrays, enhanced with silica nanospheres, have been developed for advanced porous media applications, allowing scientists to separate materials efficiently. These hollow nanospheres, created at the Department of Energy's Sandia National Laboratories, self-assemble into stiff structures, only slightly less hard than diamonds.

Self-assembly is a powerful natural process, yet biological materials generally lack the strength of synthetic ones. These self-assembling nanoparticles could lead to advanced materials for better water purification, efficient solar cells, and next-generation electronics. A dream application for these materials could be custom, printable body armor tailored to the user.

Although diamonds are often marketed as the hardest material, they do have limits in temperature and pressure, just like any other substance. Six materials have been identified that can surpass diamonds in hardness or strength.

Chapter 3: The Elite Six

Diamonds rank high for scratch resistance, making them the toughest known material in that regard. However, six materials exceed diamonds in hardness. Boron nitride, like carbon, can form various configurations, including the remarkably strong wurtzite structure, which is 18% harder than diamonds.

5.) Wurtzite Boron Nitride

Instead of carbon, boron nitride (BN) can create a crystal structure with different properties. Its rare wurtzite form, found in volcanic eruptions, has demonstrated hardness exceeding that of diamonds through simulations.

4.) Lonsdaleite

When a carbon-rich meteor strikes Earth, the graphite within it can transform into lonsdaleite under immense pressure, achieving hardness levels 58% greater than diamonds. However, most lonsdaleite samples contain impurities that reduce their hardness.

3.) Dyneema

Shifting to synthetic materials, Dyneema is a thermoplastic polyethylene polymer with an exceptionally high molecular weight, making it the strongest fiber known to humanity. It boasts the highest impact strength among thermoplastics and can even stop bullets.

2.) Palladium Microalloy Glass

This newly developed microalloy glass combines five elements, allowing it to deform without shattering, exhibiting unmatched strength and toughness against steel and other materials.

1.) Buckypaper

Buckypaper, made from carbon nanotubes, is incredibly strong and light, potentially reaching up to 500 times the strength of steel. Its unique properties make it suitable for a variety of applications, from military to biological fields.

The journey to create stronger, more resilient materials continues, and as we delve into the nanotechnology era, the significance of these advanced materials grows. Living in a time when diamonds are no longer the hardest materials available is a testament to human ingenuity and scientific progress. The future holds exciting possibilities as we explore the applications of these innovative materials.