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Scientists Develop Outstanding “Glass” as Hard as Diamonds

"Glass" as Hard as Diamonds

Scientists Develop Outstanding “Glass” as Hard as Diamonds

Researchers conducted experiments on carbon-based materials and were able to develop an outstanding “glass” with peculiar features and various potential applications, as stated in the Independent online newspaper and corroborated by National Science Review, where the original research paper can be fully accessed.

We found this subject so interesting that we decided to share it with you.

This article contains the following topics:

  1. INTRO
    • Structural characterisation
    • Mechanical properties
    • Optical properties
    • Comparison of various types of AM carbon materials or “Glass”-state materials


Exploring new forms of carbon has always been a matter of interest amongst scientists. In 2021, researchers conducted experiments with amorphous carbon materials (AM-I, AM-II and AM-III) and presented their findings.

The results of comprehensive mechanical tests performed in the synthesised amorphous carbon material named AM-III, prove that this is the hardest and strongest AM material know to this day – it can almost reach diamond crystal’s strength.
AM-III demonstrates outstanding mechanical and electronic properties, ultrahigh strength and wear resistance. A material with these characteristics, can be potentially used in photovoltaic applications, like solar cells or other technological applications, due to its properties.

This research is a demonstration of a “systematic study of the behaviour of C60 fullerene at the previously unexplored pressure of 25 GPa and different temperatures”.

The materials named AM-I, AM-II and AM-III were synthesised and characterised by the following techniques:

  • X-Ray diffraction (XRD)
  • Raman spectroscopy
  • High-Resolution Transmission Electron Microscopy (HRTEM)
  • Electron Energy Loss Spectroscopy (EELS)

As said in the original paper:

article quote
Quoted from the original research article.

Once the AM-III was the most interesting of the three AM materials, we’re going to focus on this one on the next sections of this article.


Structural characterisation

After the treatment of C60 at 25 GPa and an increase in temperature (from 1000°C to 1200°C) the material changes colour from opaque black to transparent yellow, as we can see in the image bellow (picture C):

Picture 1 AM III Article
Figure 1. XRD patterns and Raman spectra of synthetic carbon materials collected at ambient condition. (A) XRD patterns indicating phase transition path along C60→3D-C60→AM carbon→Diamond. AM-I, AM-II and AM-III have one main diffraction peak at structure factor (q) of ∼3.0 A–1 as well as another weak peak around 5.3 A–1, which are clearly different from previously discovered low-density AM carbon materials from compressing C60 at relatively low pressures of 6.5–13 GPa [17]. (B) Peak fitting of the XRD patterns of the AM carbon materials and a-D from compressing GC [12]. The magenta, green, orange and light-blue peaks are at q = ∼2.0 Å–1, ∼2.4 Å–1, ∼3.0 Å–1 and ∼5.3 Å–1, respectively. The peak at q = ∼2.0 Å–1 in a-D [12], AM-I, AM-II and the AM carbon recovered from compressing C60 at 25 GPa and 800°C, originates from the interlayer diffraction signal of residual graphite-like nanoclusters in the structure. This peak disappears in AM-III, demonstrating the formation of a completely different short-range ordered structure. (C) UV Raman spectra of AM-I, AM-II, AM-III, AM + Diamond composite and diamond. The insets are the optical photographs of recovered samples, displaying that AM-III is yellow-transparent and distinct from the black AM-I and AM-II.

Image Source: NSR

Mechanical properties

  • AM-III has the highest hardness of all known AM materials;
  • The hardness can rival that of diamond;
  • Measurements demonstrate that the AM-III is comparable in strength to diamond and superior to the other known high-strength materials;
  • A set of experimental and theoretical results demonstrate that ultrahigh hardness and strength comparable to crystalline diamond can be achieved.

Optical properties

Quoting the original piece:

“In view of the yellow-transparent nature of AM-III, its visible light absorption spectrum was measured in transmission utilising a diamond anvil cell (DAC).”

These AM carbon materials are a class of semiconductors with bandgaps less than diamond and close to the AM silicon films, often used in many ways in the technological industry.

Picture 2 AM III Article
Figure 2. Optical properties and bandgaps of AM carbon materials. (A) PL spectra measured at ambient condition. The AM-I spectrum is excited by 633 nm laser, the AM-II and AM-III spectra are excited by 532 nm laser. The bandgaps of AM carbon materials estimated from PL spectra are between 1.5 and 2.2 eV, illustrating their semiconducting nature. (B) Absorption spectrum of AM-III. The absorption edge of AM-III is at ∼570 nm, corresponding to an optical bandgap value of 2.15 eV. The inset shows an optical microscope view of a piece of transparent AM-III placed inside the hole of a gasket that is mounted inside the diamond-anvil cell (DAC).

Image Source: NSR

Comparison of various types of AM carbon materials or “Glass”-state materials

When testing crystalline materials, using one technique alone (XDR, for example) is enough to analyse its structure, whereas AM carbon materials need complimentary characterisation for a clearer identification of the different states of disordered matter.

A unique combination of semiconductive and superior mechanical properties – hardness and strength at the level of natural/synthetic diamond – is provided by a distinct short-range order, microstructure and composition.


For this experiment were performed several tests:

  • Sample synthesis;
  • X-ray diffraction and Raman spectroscopy;
  • HRTEM and EELS measurements;
  • Hardness and elastic modulus measurement;
  • Compressive strength test;
  • Optical absorption;
  • Thermal stability measurement.

For more information on these methods, make sure to read the original research article.


In conclusion, AM carbon materials — AM-III in particular — show outstanding results concerning mechanical properties, hardness and strength.

So far, we know that these materials are ultra-hard, ultra-strong, semiconducting and with various purposes, like photovoltaic or technological applications. Still, it cares for further theoretical and experimental investigation to better understand its composition and other potential applications.

If you find this article interesting, make sure to leave a comment with your thoughts and we’ll reply ASAP. In the meanwhile, you can read other articles from our blog.

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Andreia Antunes

Andreia is our Marketing Specialist at ISSCloud and writes about Internet Marketing, Search Engine Optimisation (SEO/SEM) and Social Media Marketing (SMM).

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