The sonochemical reaction between Zn(NO 3 ) 2 and hexamethylenetetramine (HMT) resulted in different products depending on amounts of Zn(II) cations in the aqueous solution. Crystalline phase pure ZnO nanoparticles were obtained by using 0.05 M Zn(NO 3 ) 2 -HMT. This single phase was formed by low power sonication for 20 min in an ultrasonic bath at ambient conditions and its morphology did not change for the next 60 min. Higher concentrations of precursors (0.1 and 0.5 M) led to a mixture of zinc compounds including plate-like Zn 5 (OH) 8 (NO 3 ) 2 (H 2 O). In contrast, a mixed phase ZnO/Zn 5 (OH) 6 (CO 3 ) 2 and a single phase Zn 5 (OH) 6 (CO 3 ) 2 were formed when the precursor concentrations were decreased to 0.01 and 0.005 M, respectively. The resulting infrared absorption and ultraviolet/visible emission were dependent on the phases and defects in these zinc compounds.

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Physical properties of polyurethane (PU) can be modified for desired applications by adding appropriate fillers. In this work, cobalt (Co) powder of average diameter 2 μπι was filled in PU elastomers synthesized by a reaction between polyol and diisocyanate. Variation of Co loading (0, 20,40 and 60 wt.%) modified thermal properties of PU composites in terms of the shift in a melting temperature and the increase in heat absorption. From DC hysteresis loops, PU/Co composites exhibited ferromagnetic properties with improved magnetizations by the increase in Co loading. On the other hand, the coercive field was almost unvaried. For high frequency electromagnetic behaviors, the complex electrical permittivity (ε-je") and magnetic permeability (μ'-]μ") were sensitive to the frequency from 10 MHz up to 100 MHz and reached the modest values in the regime between 100 MHz and 1 GHz. At each frequency, the real part of permeability and permittivity of PU were raised by the inclusion of Co fillers. While the thermal behaviors were explained using the interaction between Co clusters and the PU matrix, the electromagnetic properties can be understood by taking into the account of interactions between Co clusters at high loading levels.

Zinc oxide nanoparticles were synthesized using a commercial ultrasonic homogenizer in a sonochemical reaction between 0.05 M zinc nitrate and hexamethylenetetramine. The solutions in glass vessels of varying shapes i.e. cube, cylinder and sphere were sonicated with a 45 W 20 kHz ultrasonic pulse for 60 min under ambient conditions. The crystalline ZnO phase was confirmed by powder X-ray diffraction and scanning electron microscopy with average particle diameters around 70 nm from the three different vessels. These ZnO particles were smaller than those previously synthesized in ultrasonic baths and sonoreactors.