Developments in Ceramic Materials Research

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234 R. Ramesh, H. Kara, Ron Stevens and C. R. Bowen a b Figure 15. Porous piezoceramic hydrophone array (a) before and (b) after encapsulation. 5.2. Evaluation of Hydrophones The assembled piezocomposite hydrophones are tested in a 1.5 x 1.5 x 2.8 m 3 water tank in the frequency range 20-100 kHz. The experimental setup is shown in Figure 16. Figure 16. Schematic view of the tank used for acoustic measurements.
Progress in Porous Piezoceramics 235 A custom made parametric array is used as the acoustic source. The hydrophone sensitivities are measured by comparing the hydrophone outputs with those of a calibrated Brüel and Kjær 8103 hydrophone (B and K 8103, Denmark). The outputs of the hydrophones are amplified by 60 dB with a Brookdeal 9452 precision a.c. amplifier and displayed on a Lecroy 9304C digital oscilloscope remotely controlled by a computer for data acquisition. The input impedance of the pre-amplifier is very high (~5 GΩ), so that it does not affect the voltage developed by the standard hydrophone. Further, the same amplifier is used for the piezocomposite and standard hydrophones, so that the common errors are cancelled out when we take the frequency response, which is a ratio of two outputs. The hydrophone is evaluated in a far-field condition. For each acquisition, the waveforms are averaged over 100 sweeps and uniformly sampled over 1000 points. The angular response of the hydrophones is measured by mounting the hydrophones on a rotating table that is remotely controlled by the computer. Figure 17 shows the results of acoustic measurements of the dense PZT hydrophone, the piezocomposite hydrophones (11%PZT-polymer and 22%PZT-air) and the BandK 8103 hydrophone in the form of time-domain signals. The dense PZT and piezocomposite hydrophones have significantly different responses to the acoustic pulse. The dense PZT hydrophone showed a ‘ringing’ behaviour with a long tail (Figure 17a) and is not useful for high-resolution applications, whereas the piezocomposite hydrophones, as well as the BandK hydrophone produced short clean output pulses (Figure 17b) characteristic of a broadband transducer. The voltage output from 22% PZT-air composite is higher, while at the same time, retaining a relatively clean short pulse. The high output from the piezocomposite hydrophones for a given acoustic input signal is also reflected on the measured sensitivity graph, shown in Figure 18, which illustrates that radial resonances are suppressed in the composites when compared with the sharp resonance peak obtained for dense PZT. Suppression of the radial resonances gives a flatter response to the hydrophone. Figure 17. (Continued).
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DEVELOPMENTS IN CERAMIC MATERIALS R
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Copyright © 2007 by Nova Science P
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PREFACE Ceramics are refractory, in
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Preface ix crystals is discussed. A
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Preface xi spectra and the directio
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2 Leslie G. Cecil comprehensive dat
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4 Leslie G. Cecil Ringle et al. (19
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6 Leslie G. Cecil The main architec
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8 Leslie G. Cecil can study “the
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10 Leslie G. Cecil Middleton et al.
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12 Leslie G. Cecil The laser ablate
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14 Leslie G. Cecil There are two ge
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16 Leslie G. Cecil distinct recipes
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18 Leslie G. Cecil second group (Fi
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20 Leslie G. Cecil The Vitzil-Orang
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22 Leslie G. Cecil Table 3. Mahalan
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24 Leslie G. Cecil Ixlú and Ch’i
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26 Leslie G. Cecil structures (D. R
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28 Leslie G. Cecil paste and Macanc
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30 Leslie G. Cecil Bieber, A. M. Jr
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32 Leslie G. Cecil Kepecs, S. M., a
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34 Leslie G. Cecil Schele, L., Grub
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36 Z. C. Li, Z. J. Pei and C. Tread
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54 T. T. Basiev, V. A. Demidenko, K
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62 I, % 100 80 60 40 20 0 T. T. Bas
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68 Fluorescence, a.u. 1 T. T. Basie
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70 Fluorescence, a.u. 1 0.1 0.01 0.
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78 k, cm -1 20 18 16 14 12 10 8 6 4
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82 Photon counts 300 250 200 150 10
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84 Fluorescence, a.u. I transfer ,
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86 ln(I transfer (t)) -4.2 -4.4 -4.
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88 Fluorescence, a.u. I transfer ,
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In: Developments in Ceramic Materia
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Synthesis, Spectroscopic and Magnet
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a c Synthesis, Spectroscopic and Ma
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Transmission Transmission Transmiss
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Sm (J/Kmol) Sm (J/Kmol) 15 10 5 Syn
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Intensity (a.u.) Intensity (a.u.) 8
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IACC ( τ ) = t2 ∫ The Use of Cer
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where σ res is the scattering cros
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D50 0.8 0.7 0.6 0.5 0.4 0.3 The Use
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Definition (D50) 1 0.95 0.9 0.85 0.
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Modeling of Thermal Transport in Ce
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Page 256 and 257: 242 Development of Display Technolo
Page 258 and 259: 244 Li Chen technology moved to the
Page 260 and 261: 246 Li Chen The continuing evolutio
Page 262 and 263: 248 Li Chen the back contact cathod
Page 264 and 265: 250 Li Chen Figure 3. Vertical side
Page 266 and 267: 252 Li Chen Figure 6. Molybdenum mi
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group membership, 13, 20, 21, 22, 2
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microstructure(s), x, xi, 73, 74, 2
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efraction index, 61 refractive inde
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time, vii, ix, 1, 3, 7, 8, 11, 26,
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Developments in Ceramic Materials Research

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