Carbon is one of the most fascinating elements due to its structurally diverse allotropic forms stemming from its bonding varieties (sp, sp2, and sp3). Exploring new forms of carbon has always been the eternal theme of scientific research. Herein, we report the amorphous (AM) carbon materials with high fraction of sp3 bonding recovered from compression of fullerene C60 under high pressure and high temperature previously unexplored. Analysis of photoluminescence and absorption spectra demonstrates that they are semiconducting with a bandgap range of 1.5–2.2 eV, comparable to that of widely used amorphous silicon. Comprehensive mechanical tests demonstrate that the synthesized AM-III carbon is the hardest and strongest amorphous material known so far, which can scratch diamond crystal and approach its strength. The produced AM carbon materials combine outstanding mechanical and electronic properties, and may potentially be used in photovoltaic applications that require ultrahigh strength and wear resistance.
Articles you may be interested inIn situ structure characterization of Pb(Yb1/2Nb1/2)O3-PbTiO3 crystals under high pressure-temperature Appl.Structure and properties of superelastic hard carbon phase created in fullerene-metal composites by high temperature-high pressure treatment
Treatment of a fullerene soot extract and metal (Co) powder mixture under pressure of 5 and 8 GPa at 1000 °C leads to the transformation of fullerites into superelastic hard phase (SHP) and to simultaneous sintering of the powder mixture to nonporous composite material reinforced by the SHP particles. The structure of the SHP particles reveals a topological relation to the initial fullerite crystal morphology. Upon indentation, the SHP particles demonstrate an elastic recovery of up to 96%. The universal microhardness of the SHP particles HU = 26 GPa, and their microhardness HV = 35 GPa. A high ratio between the microhardness and elastic modulus (HV/E = 0.19-0.21) of the SHP particles makes them perspective candidates for design of materials with superior wear resistance and tribological properties.
Instrumented indentation methods have been used to study the effect of the loading rate and holding time at different maximum loads on the indentation characteristics of superelastic hard carbon particles reinforcing metal matrix composite materials. The properties of the carbon particles prepared in fullerite-metal powder mixtures by high-pressure synthesis substantially differ as a function of synthesis parameters (P, T) and the initial fullerite characteristics (C60 in crystalline or amorphous state). The indentation creep C
IT decreases with increasing F
max (500-2000 mN) and increases with holding time (60-600 s). The harder carbon particles formed from amorphous fullerite are characterized by higher indentation creep CIT and deeper penetration at constant load. Such creep behavior correlates with different elastic recovery characteristics of the particles upon indentation.
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