Perovskite-type barium strontium titanate （BST） thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol...Perovskite-type barium strontium titanate （BST） thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction （XRD） revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature. Transmission electron microscope （TEM） images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 ℃ down to 5 nm at 800 ℃. Field emission scanning electron microscope （FE-SEM） analysis and atomic force microscope （AFM） images revealed that BST thin films had mesoporous and nanocrystafiine structure with average grain size of 3Onm at 600 ℃. Based on Brunauer-Emmett-Teller （BET） analysis, the synthesized BST showed mesoporous structure containing nnres with needle, and nlate shanes and BET surface area in the range of 49-32 m^2/g at 500-800℃展开更多
TiO2 nanorods have been successfully grown into a track-etched polycarbonate （PC） membrane by a particulate sol-electrophoretic deposition from an aqueous medium. The prepared sols had a narrow particle size distrib...TiO2 nanorods have been successfully grown into a track-etched polycarbonate （PC） membrane by a particulate sol-electrophoretic deposition from an aqueous medium. The prepared sols had a narrow particle size distribution around 17 nm and excellent stability against aging, with zeta potentials in the range of 47-50 mV at pH 2. It was found that TiO2 nanorods were grown from dilute aqueous sol with a low, 0.1-M concentration. Fourier transform infrared spectroscopy （FT-IR） analysis confirmed that a full conversion of titanium isopropoxide was obtained by hydrolysis, resulting in the formation of TiO2 particles. X-ray diffraction （XRD） results revealed that TiO2 nanorods dried at 100℃ were a mixture of anatase and brookite phases, whereas they were a mixture of anatase and futile structures at 500℃. Moreover, the rutile content of the TiO2 nanorods was higher than that of TiO2 powders. Transmission electron microscope （TEM） images confirmed that TiO2 nanorods had a smooth morphology and longi- tudinal uniformity in diameter. Field emission scanning electron microscope （FE-SEM） images showed that TiO2 nanorods grown by sol-electrophoresis from the dilute aqueous sol had a dense structure with a uniform diameter of 200 rim, containing small particles with an average size of 15 nm. Simultaneous differential thermal （SDT） analysis verified that individual TiO2 nanorods, grown into a PC template, were obtained after annealing at 500℃. Based on kinetic studies, it was found that uniform TiO2 nanorods with high-quality morphology were obtained under optimum conditions at an applied potential of 0.3 V/cm and a deposition time of 60 min.展开更多
文摘Perovskite-type barium strontium titanate （BST） thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction （XRD） revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature. Transmission electron microscope （TEM） images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 ℃ down to 5 nm at 800 ℃. Field emission scanning electron microscope （FE-SEM） analysis and atomic force microscope （AFM） images revealed that BST thin films had mesoporous and nanocrystafiine structure with average grain size of 3Onm at 600 ℃. Based on Brunauer-Emmett-Teller （BET） analysis, the synthesized BST showed mesoporous structure containing nnres with needle, and nlate shanes and BET surface area in the range of 49-32 m^2/g at 500-800℃
文摘TiO2 nanorods have been successfully grown into a track-etched polycarbonate （PC） membrane by a particulate sol-electrophoretic deposition from an aqueous medium. The prepared sols had a narrow particle size distribution around 17 nm and excellent stability against aging, with zeta potentials in the range of 47-50 mV at pH 2. It was found that TiO2 nanorods were grown from dilute aqueous sol with a low, 0.1-M concentration. Fourier transform infrared spectroscopy （FT-IR） analysis confirmed that a full conversion of titanium isopropoxide was obtained by hydrolysis, resulting in the formation of TiO2 particles. X-ray diffraction （XRD） results revealed that TiO2 nanorods dried at 100℃ were a mixture of anatase and brookite phases, whereas they were a mixture of anatase and futile structures at 500℃. Moreover, the rutile content of the TiO2 nanorods was higher than that of TiO2 powders. Transmission electron microscope （TEM） images confirmed that TiO2 nanorods had a smooth morphology and longi- tudinal uniformity in diameter. Field emission scanning electron microscope （FE-SEM） images showed that TiO2 nanorods grown by sol-electrophoresis from the dilute aqueous sol had a dense structure with a uniform diameter of 200 rim, containing small particles with an average size of 15 nm. Simultaneous differential thermal （SDT） analysis verified that individual TiO2 nanorods, grown into a PC template, were obtained after annealing at 500℃. Based on kinetic studies, it was found that uniform TiO2 nanorods with high-quality morphology were obtained under optimum conditions at an applied potential of 0.3 V/cm and a deposition time of 60 min.
