ABSTRACT
Respectively using pressed method and diffuse reflectance method, the infrared absorption spectrua of sorts of kaolin in various areas were obtained. The relationship between the structure characteristics of kaolin and its absorption peaks was analyzed. The results showed that compared with pressed method, the use of diffuse reflectance Fourier transform infrared spectroscopy, combined with the K-M function, results in corrected infrared spectra with high sensitivity and is more accurate and easier to analyze. Furthermore, based on a high frequency wave of 3 700-3 600 cm(-1) sections of kaolinite-OH characteristic absorption peaks, the crystallinity of all kinds of kaolnite can be known quickly. The result is consistent with the Hinckley index surveyed by X-ray diffraction technique.
ABSTRACT
High-frequency (25 MHz) ultrasonic transducers with Na(0.5)Bi(0.5)TiO(3)-BaTiO(3) (NBT-BT) lead-free piezoelectric single crystal as the active elements are fabricated and characterized. The impedance measurement reveals that the poled [001]-oriented NBT-BT single crystal exhibits a high thickness electromechanical coefficient k(t) of 0.52 and a low clamped dielectric constant of 80. The -6-dB bandwidth of the transducer is 46.16% and the insertion loss at the center frequency is -31.89 dB. The good performance of the transducer indicates that the NBT-BT single crystal would be a promising lead-free material for ultrasonic transducer applications.
