Boron–carbon nanocomposites fabricated at high pressures and temperatures

Interaction of amorphous boron and C$_{60}$ fullerite is analyzed at pressures of 2.0 and 7.7. GPa and temperatures of 600–1800$^{\circ}$C. Effect of pressure and temperature on the material structure is studied, temperatures for synthesis of boron carbide and diamond are found, and the sequence of transformations of the carbon component is determined. Ultrasonic method is used to measure elastic moduli of the samples, and the dependences of the moduli on the structure are analyzed. It is demonstrated that the boron–carbon nanocomposite synthesized at relatively low pressure (2.0 GPa) and temperature (about 1000$^{\circ}$C) exhibits high elastic parameters (bulk modulus, $B\approx$ 75.3–84.0 GPa; Young modulus, $E\approx$ 108–119 GPa; and shear modulus, $G\approx$ 43–47 GPa at a density of about 2.2 g/cm$^3$). The results can be used for development of novel nanocomposite materials.