Articles you may be interested inStudy on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nanopatterned composite electrode

The pyroelectric properties of [111]-oriented Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 (PMN-0.29PT) crystals have been investigated both as a function of frequency and temperature. At room temperature, [111]-oriented crystals have a high pyroelectric coefficient of 12.8×10−4C∕m2K and a low thermal diffusivity of ∼3.7×10−7m2∕s. The calculated voltage responsivity and detectivity figures of merit Fv and Fd exceed 0.11m2∕C and 9.8×10−5Pa−1∕2, respectively, over a wide range of frequency from 50 to 20000 kHz. The crystals are inert in practical application environment and can be easily processed as well. Such investigation reveals that superior pyroelectric performance makes PMN-0.29PT crystals a promising candidate for uncooled infrared detectors and imagers.

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Data on the variability of pH levels in cement-based materials is essential for a better understanding of the early aging of materials and the long-term performance of concrete structures. Current approaches for measuring pH levels in concrete are inadequate with respect to radiometric range and resolution and spatial granularity. We report on a methodology for mapping pH levels in concrete utilizing a halochromic porphyrin sensor molecule that allows a simple measurement of surface values of pH level using a commercial digital camera setup. As proof of concept, cement paste, mortar, and concrete samples were subject to accelerated carbonation and then evaluated for pH profiles at different ages of degradation. Comparative tests on the same specimens were also conducted using phenolphthalein as the pH indicator. Spatial distribution of pH level from pH 11.0 to 13.5 were mapped at various levels of carbonation.