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Ultrahard bulk amorphous carbon from collapsed fullerene


Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties1,2. Due to its important applications in technology, amorphous carbon with sp2 or mixed sp2sp3 hybridization has been explored and prepared3,4, but synthesis of bulk amorphous carbon with sp3 concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties5. Here, we successfully synthesized millimetre-sized samples—with volumes 103–104 times as large as produced in earlier studies—of transparent, nearly pure sp3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 ± 2.3 GPa), elastic modulus (1,182 ± 40 GPa) and thermal conductivity (26.0 ± 1.3 W m−1 K−1) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids.

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Fig. 1: Optical photographs of the recovered samples from different HPHT conditions.
Fig. 2: XRD patterns, EELS, UV–visible absorption spectra and atomic configuration of samples recovered from different HPHT conditions.
Fig. 3: TEM studies of the AC-3 sample.
Fig. 4: Mechanical and thermal conductivity properties of sp3 amorphous carbon.

Data availability

The authors declare that the data supporting the findings of this study are available within the article. Source data are provided with this paper.


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We thank the help from beamline scientists at BL13HB for doing the PDF experiments, and the beamline scientists at BL02U for doing preliminary PDF scattering measurements. We thank R. Tai and W. Wen for their help about the PDF measurements. We thank M. Dove and G. Zhang for discussion on the PDF data processing. M.Y. would like to thank Y. Liu from the Chinese Academy of Sciences, Institute of Physics, M. Wen from Jilin Univervisty, S. Lan from Nanjing University of Science and Technology, L. Zhang and B. Yang from the Chinese Academy of Sciences, Institute of Metal Research, and G. Liu from the Shanghai Synchrotron Radiation Facility for their fruitful discussion on the structures and deformation mechanism of amorphous materials. We thank Y. Wang from the Electron Microscopy Center, Jilin University for help with HRTEM and EELS measurements. We also thank Z. Zhang for help with TDTR measurements and data analysis. This work was supported financially by the National Key R&D Program of China (2018YFA0305900, 2018YFA0703400 and 2017YFA0403801), the National Natural Science Foundation of China (51822204, 51320105007, 11634004, 41902034 and U1732120), the China Postdoctoral Science Foundation (2020TQ0121).

Author information




B.L. and M.Y. conceived and designed the study. Y.S., Z.L., M.Y., Z.Y., F.S., X.H., L.W. and Y.F. synthesized the materials. Y.S., Z.Y., J.D, F.S. and C.Z. performed the XRD, Raman, UV–vis absorption measurements. Y.S., J.D., W.Z. and M.Y. performed the TEM characterization and analysis. Z.L., Y.S., F.S. and N.Z. performed the nanoindentation measurements. Y.S. performed Vickers, Knoop hardness measurements and TDTR measurements. J.D., Y.S., Q.L., H.L., X.H., R.F., M.Y., J.J. and X.Z. performed the synchrotron XRD measurements and data analysis. Y.S. and C.Z. draw the pictures. Y.S., M.Y., B.L., W.W., Z.L., J.D., F.S., B.S. and Y.F. analysed the results of data. M.Y., Y.S., B.S. and B.L. wrote the manuscript. All authors discussed the results and contributed to the final manuscript.

Corresponding authors

Correspondence to Mingguang Yao or Bingbing Liu.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Alfonso San Miguel, Yogesh Vohra and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Optical image of thin slices of bulk sp3 amorphous carbon samples.

The thin slices were cut from the bulk samples recovered from different HPHT conditions. The colour difference of these samples can be observed.

Extended Data Fig. 2 PT phase diagram of C60.

Results for pressure below 20 GPa and temperature below 2,000 K are from ref. 10. Solid symbols denote different samples obtained in this study: blue hexagon, dual-coloured hexagon, red circle and dual-coloured circle represent nanocrystalline diamonds, bulk sp3 amorphous carbon containing nanocrystalline diamonds (NCD), nearly fully sp3-bonded amorphous carbon, and amorphous carbon with a small amount of sp2 carbons, respectively. Abbreviations Gra and Dia represent graphite and diamond, respectively. The ‘collapse’ line represents the fullerene will collapse at 27~28 GPa at room temperature

Source data.

Extended Data Fig. 3 EELS spectra of AC-1, AC-2, AC-3 and AC-6 samples.

The black line is EELS of standard sp2 glassy carbon, the green line is amorphous diamond obtained from ref. 12 and the yellow line is sp3-rich tetrahedral amorphous carbon (ta-C) from ref. 14. The boxes indicate the energy windows for intensity integration used in two-windows method. The lines 284 and 291 correspond to the energy channels at which the intensities, used in peak-ratio method, were taken

Source data.

Extended Data Fig. 4 Peak-ratio method used for determining the sp3 concentration of different sp3 amorphous carbon samples.

ah, The sp3 concentration of standard sp2 glassy carbon and samples AC-1, AC-2, AC-3, AC-4, AC-5 and AC-6, plus a sample recovered from 27 GPa and 700 °C, respectively

Source data.

Extended Data Fig. 5 Photoluminescence and Raman spectra of sp3 amorphous carbon.

a, Photoluminescence spectra of AC-1 and AC-3 samples at room temperature. b, Raman spectra of AC-1 and AC-3 samples excited by visible (514.5 nm) and UV (325 nm) laser. c, d, The corresponding UV Raman spectra after PL background subtraction

Source data.

Extended Data Fig. 6 TEM images of the samples recovered from 20 GPa 1,000 °C and 37 GPa 1,000 °C.

a, HRTEM image of AC-1 sample in which disordered sp2 carbon was clearly observed. b, HRTEM image of diamond nanocrystals existing in the sp3 amorphous carbon sample obtained at 37 GPa and 1,000 °C.

Extended Data Fig. 7 Nanoindentation measurements of sp3 amorphous carbon samples and single crystalline diamond.

The indentation force versus depth (Ph) curves of AC-1, AC-3 and of the (100) face of single crystal diamond during loading and unloading with the maximum loads ranging from 100 to 500 mN

Source data.

Extended Data Fig. 8 Knoop hardness measurements of sp3 amorphous carbon samples and the SEM image of the indentation in our amorphous carbon and single crystal diamond after Vickers hardness measurement.

a, HK of AC-1 and AC-3 samples as a function of applied load (F). The inserts are optical images of the indentation at a load of 4.9 N. Error bars indicate five different measurement points, standard deviations. b, c, SEM images of the indentation in our amorphous carbon and in single crystal diamond after Vickers hardness measurement. The fracture of our sp3 amorphous carbon shows irregular, tooth-like cracks/edges, while that of single crystal diamond shows a regular fracture along some crystal planes. The different fracture behaviour compared with crystalline diamond should be due to the amorphous structure of our materials, in which the fracture/crack propagation behaves different from that in anisotropic crystals, leading to the irregular fracture surface

Source data.

Extended Data Fig. 9 TDTR measurements on sp3 amorphous carbon and standard samples.

a, c, The ratio signals of in-phase and out-of-phase, −Vin/Vout (open circles) for amorphous carbon samples (a) and standard Si, Al2O3, and SiO2 (c) samples, as a function of delay time. The solid lines represent the best fit to the thermal model. b, The measured thermal conductivities of standard materials (Si, Al2O3 and SiO2) compared with literature data

Source data.

Extended Data Fig. 10 The Tauc bandgap of sp3 amorphous carbon samples determined from plots of (αhν)1/2 versus photon-energy.

af, The obtained Tauc bandgap of samples recovered from 37 GPa and 450 °C (a), 20 GPa and 1,000 °C (b), 25 GPa and 1,000 °C (c), 27 GPa and 700 °C (d), 27 GPa and 900 °C (e), and 27 GPa and 1,000 °C (f)

Source data.

Source data

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Shang, Y., Liu, Z., Dong, J. et al. Ultrahard bulk amorphous carbon from collapsed fullerene. Nature 599, 599–604 (2021).

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