We have successfully fabricated large area free standing polyvinylidene fluoride -Pb(Zr0.52Ti0.48)O3 (PVDF-PZT) ferroelectric polymer-ceramic composite (wt% 80–20, respectively) thick films with an average diameter (d) ∼0.1 meter and thickness (t) ∼50 μm. Inclusion of PZT in PVDF matrix significantly enhanced dielectric constant (from 10 to 25 at 5 kHz) and energy storage capacity (from 11 to 14 J/cm3, using polarization loops), respectively, and almost similar leakage current and mechanical strength. Microstructural analysis revealed the presence of α and β crystalline phases and homogeneous distribution of PZT crystals in PVDF matrix. It was also found that apart from the microcrystals, well defined naturally developed PZT nanocrystals were embedded in PVDF matrix. The observed energy density indicates immense potential in PVDF-PZT composites for possible applications as green energy and power density electronic elements.
Passive seismic tomography, in which the event locations and the velocity model are inferred simultaneously, is seldom used to process microseismic surveys acquired in the oil and gas industry. We discuss advantages of applying tomographic ideas to typical microseismic data recorded in a single, nearly vertical well to monitor hydraulic stimulation of a shale-gas reservoir. Microseismic events are conventionally located in the energy-industry applications using a velocity model derived from sonic logs and perforation shots. Instead of fixing the model, as is normally done, we alter it while locating the events. This added flexibility not only makes it possible to accurately predict traveltimes of the recorded P- and S-waves, but also provides a convincing evidence for anisotropy of the examined shale formation. While we find that velocity heterogeneity does not need to be introduced to explain the data acquired at each stage of hydraulic fracturing, the obtained models are suggestive of possible time-lapse changes in the anisotropy parameters that characterize the stimulated reservoir volume.
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