We report low- and high-temperature Raman spectroscopy of pressure-induced amorphous boron carbide (a- B4 C). Coarsening of carbon clusters in a- B4 C was characterized during heating, whereas unusual temperature coefficients of a- B4 C Raman peak shifts were observed during cooling. These results experimentally evidence that the amorphization of B4 C is associated with the destruction of the C-B-C chains and a- B4 C is composed of s p2 carbon aromatic rings and boron clusters. This disordered structure with relatively weak carbon s p2 bonds is believed to be responsible for the loss of B4 C shear strength at high pressures.
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