General Route to Nanocrystalline Oxides by Hydrodynamic Cavitation

We have developed the WPI cavitational materials process for the production of phase-pure, nanostructured materials. Hydrodynamic cavitation is generated mechanically using a high-pressure fluid system. The method begins with a precipitant stream that experiences a large pressure drop (21 000 psi ambient) across a patented geometry interaction chamber. Due to the large pressure drop, bubbles are formed and collapse, causing localized heating of the solvent. In addition, the precipitate undergoes a high degree of mechanical shear in the interaction chamber. This paper deals with the application of this novel technique to the synthesis of several nanostructured oxides. The nanophase oxides are characterized using transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Select area diffraction patterns of the dried (110 °C) oxide samples in this study show distinct rings indicating nanosized particles. This is corroborated by peak breadth measurements in the X-ray diffraction patterns of the calcined samples. A comparison is made between cavitation syntheses and classical coprecipitation.