Science Advances

Supplementary Materials

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  • fig. S1. XRD of compressed GCs recovered after compressing raw GC at pressures of 10 to 25 GPa and temperatures of 600° to 1200°C.
  • fig. S2. SAED patterns of compressed GCs measured at different length scales.
  • fig. S3. Local order in compressed GC.
  • fig. S4. The sp3 component of compressed GCs measured at ambient condition.
  • fig. S5. The sp3 component of compressed GC and microstructure of raw GC.
  • fig. S6. UV Raman spectroscopy of compressed GCs.
  • fig. S7. The loading/unloading-displacement curves of compressed GCs in comparison with raw GC, Cu, and MgO.
  • fig. S8. The loading/unloading-displacement curves, indentation hardness, and elastic recovery of compressed GCs synthesized at moderate pressures and temperatures.
  • fig. S9. The loading/unloading-displacement curves, hardness, Young’s modulus, and indentation elastic recovery of compressed GC at varied loading, holding, and unloading times.
  • fig. S10. Indentation morphology after unloading three-sided pyramidal Berkovich diamond indenter, showing significant elastic recovery.
  • fig. S11. Optical images of the indentations on diamond and Com.GC-2 after unloading a four-sided pyramidal diamond indenter.
  • fig. S12. Mohs hardness of compressed GC (Com.GC-3) characterized with qualitative scratch tests.
  • fig. S13. Axial compressive stress-strain relations established in a simple DAC.
  • fig. S14. Compressive strength tests for standard materials including type I and II GCs in a simple DAC.
  • fig. S15. Comparison of thermal stability of compressed GC (Com.GC-3) with raw GC at air and inert argon (Ar) or nitrogen (N2) conditions, respectively.

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