Poling conditions

Moreover, a large scatter of the piezoelectric constant among samples of different poling conditions, such as is indicated in Table 3, seems to suggest that the piezoelectricity of polarized PVDF does not have a single origin. Further work is required to settle this problem. 

The nonlinear optical susceptibility can be calculated by assuming a one-dimensional molecule and a non-interacting molecular ensemble at the poling conditions, and is given by... 

Tabie 6. Poling conditions and EO coeiiicients of various organic-inorganic hybrid films... 

Excellent stability and solvent resistance 150°C 1 hr Poling condition 140°C... 

Pyro- and Piezoelectric Properties The electric field application on a ferroelectric nanoceramic/polymer composite creates a macroscopic polarization in the sample, responsible for the piezo- and pyroelectricity of the composite. It is possible to induce ferroelectric behavior in an inert matrix [Huang et al., 2004] or to improve the piezo-and pyroelectricity of polymers. Lam and Chan [2005] studied the influence of lead magnesium niobate-lead titanate (PMN-PT) particles on the ferroelectric properties of a PVDF-TrFE matrix. The piezoelectric and pyroelectric coefficients were measured in the electrical field direction. The Curie point of PVDF-TrFE and PMN-PT is around 105 and 120°C, respectively. Different polarization procedures are possible. As the signs of piezoelectric coefficients of ceramic and copolymer are opposite, the poling conditions modify the piezoelectric properties of the sample. In all cases, the increase in the longitudinal piezoelectric strain coefficient, 33, with ceramic phase poled) at < / = 0.4, the piezoelectric coefficient increases up to 15 pC/N. The decrease in da for parallel polarization is due primarily to the increase in piezoelectric activity of the ceramic phase with the volume fraction of PMN-PT. The maximum piezoelectric coefficient was obtained for antiparallel polarization, and at < / = 0.4 of PMN-PT, it reached 30pC/N. 

C. The oriented films were finally annealed at 120 C for 0.5 hr. In order to control the degree of molecular orientation, the uniaxially drawn samples were annealed to shrink at 160 C. Aluminum electrodes for electric measurements were evaporated onto both film surfaces. The poling condition used for this experiment was 25 MV/m at 120°C for 2hrs. 

Wood pole condition has traditionally been assessed by the sound of an impact on the pole or from the condition of a cored sample of the wood. Recent developments include nondestructive test procedures that offer more refined assessment of wood pole conditions. A device based on the measurement of the passage of ultrasound through the wood was developed [9]. The condition of the pole can be assessed, provided there is an adequate database to calibrate the signal delay time against the measured strength of the particular wood species. The device can only indicate the condition at and above the ground line. 

E J. Sbuford, A. F. Wil. J. J. Rkca, anid G. E Thomas. Characterization and piezoelectric activity of stretched and poled poly(vtnytidene fluorideX 7>tt I effect of draw ratio and poling conditions. Polymer Eng. Sci 16 2S (1976X... 

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