Extremely high-frequency piezoelectroacoustic transducer based on BN-tube/SiC-whiskers rope

Innovative idea of piezoelectric electroacoustic transducer in extremely high-frequency terahertz range on the basis of BN-tube/SiC-whiskers rope is suggested and substantiated. Unlike an acoustic spectrum of solid rectangular pins and films used so far in ultrasonic pulsers and receivers, in the acoustic spectrum of circular hollow nanotubes, the peculiar squash E2g and the subsequent Eng modes of starlike chain belonging to a gallery of whispering acoustic modes was shown by ab initio RHF/6-31G calculations to exist in the Raman spectra. Inherent important feature of these standing vibrations is their weak attenuation and high frequency, which, as depended on the nanotube diameter, fall in the range of about ∼1 GHz–1 THz. Hypersound was suggested to be excited by resonant microwaves using the piezoelectric properties of BN heteropolar nanotubes and then to transmit it into a sample by high modulus encapsulated SiC-whiskers. Such BN-tube/SiC-whiskers of 100–800 nm in diameter and with ∼20 aspect ratio were synthesized by carbothermal and CVD techniques. Cactus-like arrays of SiC nanowhiskers were synthesized by CVD technique. A sketch of the hypersound generator/detector, with the piezoelectroacoustical transducer on the basis of the BN-tube/SiC-whisker assembly serving as hypersonic antenna, was advanced.