Nanoporous and dense ferroelectric PbTiO 3 thin films are prepared by a modified solgel process. The presence of nanoporosity, with ~ 50 nm pore size formed using a block polymer as a structure-directing agent, markedly affects the microstructure, crystallization and ferroelectric film´s properties. The crystallization of the tetragonal phase is enhanced in nanoporous films. It is suggested that the decomposition of the block-copolymer in porous films triggers the crystallization of the perovskite phase at low temperatures via the local increase of temperature. Consequently, nanoporous films with improved tetragonality exhibit enhanced piezoelectric coefficients, switchable polarization and low local coercivity. By providing a means of achieving enhanced properties, nanoporosity may have a broad impact in applications of ferroelectric thin films.Nanoporous PbTiO 3 films present enhanced tetragonality at lower temperature than respective dense films. Moreover, the porosity present in the nanoporous films allows an increase of the local piezoelectric response and a decrease of the local coercive field. As result, these nanoporous films might be used to improve switching behaviour of ferroelectric thin films
Nanopatterned porous thin films of bismuth ferrite (BiFeO3) with porosity perpendicular to the plane are prepared by an evaporation-induced self-assembly methodology using nitrate metal salts and a commercial block copolymer as a structure-directing agent.
The preparation of PDMS-TEOS-CaO hybrid materials by sol-gel techniques has been widely described in previous works. Calcium nitrate is the most common source of calcium used in these preparations. However, to remove possible toxic nitrate by-products a thermal treatment is necessary at temperatures above 500 ºC, which leads to the degradation of the polymeric components of the hybrids. Strontium has already shown some promising results in the therapeutic area, being used in cases of osteoporosis and low bone density. In this study a new potential bioactive hybrid material was prepared, by sol-gel techniques, using calcium acetate as a novel calcium source. Also, for the first time, incorporation of strontium in a PDMS-TEOS hybrid system was evaluated. Samples were characterized before and after immersion in Kokubo's Simulated Body Fluid (SBF) by SEM, EDS, ICP and FT-IR spectroscopy . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 isabelmsalvado@ua.pt
AbstractThe preparation of PDMS-TEOS-CaO hybrid materials by sol-gel techniques has been widely described in previous works. Calcium nitrate is the most common source of calcium used in these preparations. However, to remove possible toxic nitrate by-products a thermal treatment is necessary at temperatures above 500 ºC, which leads to the degradation of the polymeric components of the hybrids. Strontium has already shown some promising results in the therapeutic area, being used in cases of osteoporosis and low bone density. In this study a new potential bioactive hybrid material was prepared, by sol-gel techniques, using calcium acetate as a novel calcium source. Also, for the first time, incorporation of strontium in a PDMS-TEOS hybrid system was evaluated. Samples were characterized before and after immersion in Kokubo's Simulated Body Fluid (SBF) by SEM, EDS, ICP and FT-IR spectroscopy.
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