Developments in Ceramic Materials Research

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232 R. Ramesh, H. Kara, Ron Stevens and C. R. Bowen Piezoelectric charge coefficients, permittivity and impedance data are collected using the method described in Section.2.1. The measured piezoelectric and dielectric properties of the dense PZT ceramic and piezocomposites are given in Table 2. This table shows that the reduction in d31 is significantly greater than that for d33. Consequently, gH and figure of merit (dH.gH) are improved for the piezocomposites compared with dense PZT. However, the dielectric constant and hence, the capacitance of the piezocomposites is much lower than that of the dense piezoceramic material. Table 2. Properties of dense piezoceramic, 22% PZT-Air composite and 11% PZT- Polymer composite. The parameters d33, d31, , device capacitance and receiving sensitivity have been measured and the parameters dH, gH are dH.gH are calculated Material d 33 pCN -1 d 31 pCN -1 T ε 33 x10 -9 Fm -1 ε dH pCN -1 T 33 g H x10 -3 VmN -1 d H.g H x10 -15 Pa -1 MdB re. 1VμPa -1 Device Cap.pF PZT-5H 513 220 25.3 72.8 2.87 209 -205 5050 22% PZT-Air 210 29 2.8 152 54.2 8238 -198 800 11% PZT- Polymer 35.7 7 0.67 21.7 28.3 614 -215 210 5.1.2. Hydrophone Assemby The porous piezocomposites show a low permittivity, which results in a low measured device capacitance values compared to the dense PZT hydrophone (Table 2). Since the capacitance of the cable used (RS Products) is 42 pF m -1 and a 1.5m cable used for each hydrophone, the capacitance of the devices is increased in order to reduce the cable loading effect which can lead to a decrease in the hydrophone sensitivity. To achieve this, two discs of piezocomposite are attached back-to-back using an electrically parallel connection. The configuration is shown in Figure 14. The pieces are attached to a 0.15 mm thick copper plate electrode with conductive epoxy (RS Products, UK, Product 186-3616) in opposite poling directions. The remaining two faces are then attached with copper electrodes and soldered to a cable. The middle electrode is used as the positive lead and the two outer electrodes are connected to the cable shield. Finally, the whole assembly is molded in 1mm thick polyurethane for water isolation (Figure 14). The dense PZT ceramic hydrophone is also assembled in the same way with the same thickness for a direct comparison. In order to ensure the structural integrity of the device assembly, an impedance spectrum is measured, in air, at every stage of the construction using Solartron Impedance Analyser (Model 1260, USA). The impedance spectra so recorded do not show any spurious peaks, indicating proper structural integrity of the hydrophones. For any underwater application, hydrophones are normally used in the form of an array. Hydrophone arrays covering large surface area are desirable for certain applications because, it enhances the signal-to-noise ratio of the receiver system. Further, acoustic imaging systems require arrays of hydrophones to collect information arriving from different angles with respect to the position of the array itself. Characteristics of hydrophone arrays are found to be
Progress in Porous Piezoceramics 233 deviate from that of the single-element hydrophone. Therefore, it is important to evaluate the arrays in order to assess their underwater performance. Figure 14. (a) Schematic design and (b) assembled piezocomposite hydrophones. Figure 15a shows the photograph of a 3x3 hydrophone array assembled using square pieces of porous piezoceramics and Figure 14b shows the array after encapsulation.
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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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The Use of Ceramic Pots in Old Wors
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3.2. Wall-in Positions The Use of C
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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
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Page 268 and 269: 254 Li Chen Figure 8(a). I-V curve
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correlation function, 156 corrosion
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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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