The crystallization of calcite from mixed alcohol water solvents in the presence of a double hydrophilic block copolymer poly(ethylene glycol) block poly(methacrylic acid)(PEG b PMAA) has been investigated. It was rev...The crystallization of calcite from mixed alcohol water solvents in the presence of a double hydrophilic block copolymer poly(ethylene glycol) block poly(methacrylic acid)(PEG b PMAA) has been investigated. It was revealed that with increasing the volume fractions of ethanol or isopropanol, the morphology of the CaCO 3 particles generally varies from peanuts through rods to spheres in the presence of the polymer. Specifically, uniform rounded calcite rods, which are about 2 μm in length with an aspect ratio of 2.6, were obtained in the isopropanol solution with volume fraction 50%.展开更多
Aragonite calcium carbonate whisker was prepared by thermal decomposition of Ca（HCO3）2 in aqueous solution in the presence of chloride salts. The influences of reaction temperature, time and concentrations of CaCl2,...Aragonite calcium carbonate whisker was prepared by thermal decomposition of Ca（HCO3）2 in aqueous solution in the presence of chloride salts. The influences of reaction temperature, time and concentrations of CaCl2, MgCl2 and KCl on the morphology of CaCO3 whiskers were studied. The structure characteristics of CaCO3 whiskers were analyzed by XRD and SEM. The results indicate that the optimum conditions are 80～100 ℃, 50～60 min and the suitable concentrations of Ca（HCO3）2, KCl, MgCl2, CaCl2 are 6.0 mmol/L, 14.0 mmol/L, 1.0 mmol/L, 1.5 mmol/L respectively. The purity of the whiskers is 99.53% and the average aspect ratio is 24.1.展开更多
Submicrometer-sized, spherical vaterite particles were synthesized by solid-state reaction at room temperature in the presence of poly(acrylic acid)(PAA). The obtained products were characterized by XRD, IR and SEM. I...Submicrometer-sized, spherical vaterite particles were synthesized by solid-state reaction at room temperature in the presence of poly(acrylic acid)(PAA). The obtained products were characterized by XRD, IR and SEM. It was revealed that with increasing PAA amount, the crystal polymorph of CaCO 3 particles varied gradually from pure calcite through a mixture of calcite and vaterite to pure vaterite, and the particle size decreased generally. It was proposed that in solid-state reaction, PAA induced the formation of vaterite and the phase transformation from vaterite to calcite was prevented completely due to the absence of H 2O, resulting in the formation of pure vaterite particles.展开更多
文摘The crystallization of calcite from mixed alcohol water solvents in the presence of a double hydrophilic block copolymer poly(ethylene glycol) block poly(methacrylic acid)(PEG b PMAA) has been investigated. It was revealed that with increasing the volume fractions of ethanol or isopropanol, the morphology of the CaCO 3 particles generally varies from peanuts through rods to spheres in the presence of the polymer. Specifically, uniform rounded calcite rods, which are about 2 μm in length with an aspect ratio of 2.6, were obtained in the isopropanol solution with volume fraction 50%.
文摘Aragonite calcium carbonate whisker was prepared by thermal decomposition of Ca（HCO3）2 in aqueous solution in the presence of chloride salts. The influences of reaction temperature, time and concentrations of CaCl2, MgCl2 and KCl on the morphology of CaCO3 whiskers were studied. The structure characteristics of CaCO3 whiskers were analyzed by XRD and SEM. The results indicate that the optimum conditions are 80～100 ℃, 50～60 min and the suitable concentrations of Ca（HCO3）2, KCl, MgCl2, CaCl2 are 6.0 mmol/L, 14.0 mmol/L, 1.0 mmol/L, 1.5 mmol/L respectively. The purity of the whiskers is 99.53% and the average aspect ratio is 24.1.
文摘Submicrometer-sized, spherical vaterite particles were synthesized by solid-state reaction at room temperature in the presence of poly(acrylic acid)(PAA). The obtained products were characterized by XRD, IR and SEM. It was revealed that with increasing PAA amount, the crystal polymorph of CaCO 3 particles varied gradually from pure calcite through a mixture of calcite and vaterite to pure vaterite, and the particle size decreased generally. It was proposed that in solid-state reaction, PAA induced the formation of vaterite and the phase transformation from vaterite to calcite was prevented completely due to the absence of H 2O, resulting in the formation of pure vaterite particles.
