  High intensity ultrasonic irradiation (sonication) of alkane slurries of
polycrystalline \ybco leads to a significant modification of the grain
morphology and, if performed with enforced oxygen flow, results in the increase
of the superconducting transition temperature. Sonication with added Fe(CO)$_5$
produces magnetic \fe2o3 nanoparticles deposited on the surface of \ybco (YBCO)
granules. Upon sintering these nanoparticles should act as efficient pinning
centers utilizing both condensation and magnetic contributions to the free
energy. The developed method could become a major technique to produce
practically useful high-pinning nanocomposite materials based on \ybco
superconductor.
