The effects of Na＋, concentrations on the crystal Mg2＋, A13＋ and Fe3＋ ion morphology of calcium sulfate hemihydrate whiskers formed via a hydrothermal method have been studied. In the presence of A13＋ concentrati...The effects of Na＋, concentrations on the crystal Mg2＋, A13＋ and Fe3＋ ion morphology of calcium sulfate hemihydrate whiskers formed via a hydrothermal method have been studied. In the presence of A13＋ concentrations higher than 1x10-3 mol/L the whiskers were significantly shorter and thicker and the presence of Mg2＋ and Fe3＋ resulted in shorter whiskers. The presence of Nan did not affect the morphology of the whiskers. Through elemental analysis, it was determined that Mg2＋ and A13＋ were selectively adsorbed on the surfaces of the crystals, whereas Fe3＋ underwent a hydrolysis reaction to form a brown precipitate which decreased the ion concentration in the solution. These results indicate that in raw materials used for the industrial preparation of calcium sulfate whiskers, AI3＋ and Fe3＋ should be removed and the Mg2＋ concentration should be less than 8 x 10-3 mol/L in order to obtain pure whiskers with high aspect ratios.展开更多
LiCoPO4 micron-rods with an average diameter of about 500 nm and length of about 5 μm were synthesized by dispersant-aided hydrothermal method. Poly(n-vinylpyrrolidone) (PVP) was used as dispersant in the hydrotherma...LiCoPO4 micron-rods with an average diameter of about 500 nm and length of about 5 μm were synthesized by dispersant-aided hydrothermal method. Poly(n-vinylpyrrolidone) (PVP) was used as dispersant in the hydrothermal method. The starting solution and the concentration of dispersant have significant influences on the morphology of LiCoPO4,and the electrochemical performance is improved via controlling the particle size and morphology by the hydrothermal method. The cell using smaller particle LiCoPO4 as cat...展开更多
pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti（SO4）2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano- sized TiO2 ...pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti（SO4）2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano- sized TiO2 powder with various morphologies and sizes was synthesized. Changes in morphology, size and phase type with pH values of samples were characterized by X-ray diffraction （XRD） and transmission electron micro- scopy （TEM） measurements. Results show that under the present preparation conditions, TiO2 powder is an anatase phase with pH value less than 11, but is more likely to be a brookite phase with pH value more than 11. With the increase in pH value from 1 to 11 in hydrothermal envi- ronment, nano-sized anatase TiO2 gradually grows up in all directions. {001 }, { 101 } and { 100} groups of crystal plane are the exposed crystal planes of nano-sized anatase TiO2 for the （004）, （101） and （200） facets found in high-reso- lution TEM image. The photocatalytic performance of nano-sized TiO2 with different morphologies was com- pared by measuring their photocatalytic degradation rates for methylene blue under ultraviolet light. Results show that anatase TiO2 prepared under the alkalescenthydrothermal environment （pH = 9, 11） has a better pho- tocatalytic degrading performance. Different sizes and phases of nanoscaled TiO2 powders with different photo- catalytic performances can be prepared by the control of pH value of hydrothermal solutions.展开更多
文摘The effects of Na＋, concentrations on the crystal Mg2＋, A13＋ and Fe3＋ ion morphology of calcium sulfate hemihydrate whiskers formed via a hydrothermal method have been studied. In the presence of A13＋ concentrations higher than 1x10-3 mol/L the whiskers were significantly shorter and thicker and the presence of Mg2＋ and Fe3＋ resulted in shorter whiskers. The presence of Nan did not affect the morphology of the whiskers. Through elemental analysis, it was determined that Mg2＋ and A13＋ were selectively adsorbed on the surfaces of the crystals, whereas Fe3＋ underwent a hydrolysis reaction to form a brown precipitate which decreased the ion concentration in the solution. These results indicate that in raw materials used for the industrial preparation of calcium sulfate whiskers, AI3＋ and Fe3＋ should be removed and the Mg2＋ concentration should be less than 8 x 10-3 mol/L in order to obtain pure whiskers with high aspect ratios.
文摘LiCoPO4 micron-rods with an average diameter of about 500 nm and length of about 5 μm were synthesized by dispersant-aided hydrothermal method. Poly(n-vinylpyrrolidone) (PVP) was used as dispersant in the hydrothermal method. The starting solution and the concentration of dispersant have significant influences on the morphology of LiCoPO4,and the electrochemical performance is improved via controlling the particle size and morphology by the hydrothermal method. The cell using smaller particle LiCoPO4 as cat...
基金financially supported by the National Natural Science Foundation of China (Nos.51302322 and 21373273)the Open-End Fund for the Valuable and Precision Instruments of Central South University (No.CSUZC201613)+1 种基金the Open Foundation of Guangdong Provincial Key Laboratory for Technology and Application of Metal Toughening,Guangdong Institute of Materials and Processing (No.GKL201605)the Education Reform Project of Central South University (No.2016jy03)
文摘pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti（SO4）2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano- sized TiO2 powder with various morphologies and sizes was synthesized. Changes in morphology, size and phase type with pH values of samples were characterized by X-ray diffraction （XRD） and transmission electron micro- scopy （TEM） measurements. Results show that under the present preparation conditions, TiO2 powder is an anatase phase with pH value less than 11, but is more likely to be a brookite phase with pH value more than 11. With the increase in pH value from 1 to 11 in hydrothermal envi- ronment, nano-sized anatase TiO2 gradually grows up in all directions. {001 }, { 101 } and { 100} groups of crystal plane are the exposed crystal planes of nano-sized anatase TiO2 for the （004）, （101） and （200） facets found in high-reso- lution TEM image. The photocatalytic performance of nano-sized TiO2 with different morphologies was com- pared by measuring their photocatalytic degradation rates for methylene blue under ultraviolet light. Results show that anatase TiO2 prepared under the alkalescenthydrothermal environment （pH = 9, 11） has a better pho- tocatalytic degrading performance. Different sizes and phases of nanoscaled TiO2 powders with different photo- catalytic performances can be prepared by the control of pH value of hydrothermal solutions.
