Observation of ultrasound velocity gradient in fullerene ceramics by acoustic microscopy

A scanning acoustic microscope is used to study the distribution of elastic properties in small samples (O 3 x 2 mm3) of new hard phases of C60. The specimens under investigation were synthesized from pure C60 powder under pressure P = 8 GPa in the temperature range 500-1650 K. The time-of-flight mode was used for bulk sound wave velocity determination in a direction parallel to the cylinder's axis. Longitudinal sound wave velocities greater than 10,000 m/s were found for all specimens treated at temperatures higher than 1000 K. Using the B-scan mode allowed us to observe the velocity gradient in the sample's periphery. The heterogeneous internal structure of the specimen is visualized in the images formed in C- and B-scan modes.