Spherical calcium carbonate was prepared by the reaction of sodium carbonate with calcium chloride at the presence of a protein like molecule, polyvinylpyrrolidone, as the template. The products were characterized by ...Spherical calcium carbonate was prepared by the reaction of sodium carbonate with calcium chloride at the presence of a protein like molecule, polyvinylpyrrolidone, as the template. The products were characterized by elemental analyses, XRD, SEM, and TG DSC respectively. The effects of polyvinylpyrrolidone on the crystal form and morphology of the as prepared CaCO3 were investigated. It was found that the aggregative shape of the produced calcium carbonate crystalline could be well controlled by adjusting the concentration of the polyvinylpyrrolidone template. This may be of important meanings to the biomimetic synthesis of novel inorganic materials.展开更多
CaSO4 Nanorods/wires were synthesized in quaternary W/O microemulsion soluti on containing triton X-100, cyclohexane and n-pentanol. Transmission electro n microscopy (TEM) was utilized to characterize the shape and s...CaSO4 Nanorods/wires were synthesized in quaternary W/O microemulsion soluti on containing triton X-100, cyclohexane and n-pentanol. Transmission electro n microscopy (TEM) was utilized to characterize the shape and size of products a s-prepared, as well as electron diffraction (ED) pattern was obtained for desi gnated nanorods (wires). It is revealed that ù0 (molar ratio of water to surfa ctant),reactants concentration and aging time play an important role in the form ation of different morphologies and size of synthesized CaSO4 nanocrystal.展开更多
Calcium fluoride nanoparticles were synthesized by water/cetyltrimethylammonium bromide (CTAB)/2-octanol microemulsion systems. X-ray powder diffraction analysis showed that the products were a single phase. The resul...Calcium fluoride nanoparticles were synthesized by water/cetyltrimethylammonium bromide (CTAB)/2-octanol microemulsion systems. X-ray powder diffraction analysis showed that the products were a single phase. The result of scanning electron microscopy confirmed that the average sizes of the calcium fluoride particles were below 100 nm in diameter. With decreasing water content and reaction time, the particle sizes decreased.展开更多
The spherical CaCO3 composite was synthesized in the presence of the amphiphilic block copolymer, i.e. polystyrene-b-poly(acrylic acid). It was revealed by XRD analysis that the grains in the composite was calcite wit...The spherical CaCO3 composite was synthesized in the presence of the amphiphilic block copolymer, i.e. polystyrene-b-poly(acrylic acid). It was revealed by XRD analysis that the grains in the composite was calcite with great distortion. Infared and Raman analysis showed that the composite was composed of PS-b-PAA calcium salt and calcite, and the calcite was nano-scaled.展开更多
合成了表面包覆 Si O2 的超细 Ca CO3 。通过 XPS,XRD对包覆表面层结构的分析 ,证实了 Si O2 以无定形包覆于 Ca CO3 表面 ,并在其表面形成了 Si- O- Ca键。对 Si O2 包覆超细 Ca CO3 的机理分析结果可知 :Na2 Si O3 的加入量是影响包...合成了表面包覆 Si O2 的超细 Ca CO3 。通过 XPS,XRD对包覆表面层结构的分析 ,证实了 Si O2 以无定形包覆于 Ca CO3 表面 ,并在其表面形成了 Si- O- Ca键。对 Si O2 包覆超细 Ca CO3 的机理分析结果可知 :Na2 Si O3 的加入量是影响包覆效率的重要因素 ,由于硅酸易自聚 ,控制 Si O2 与 Ca CO3 的重量比约为4 %～ 5 %时为包覆的最佳点 ;Ca CO3 晶粒度大小影响分散性能 ,进而影响包覆效率 ,分散性能好的包覆效率较高。展开更多
Eu3+ activated CaWO4 was prepared by high temperature solid state reaction technique. Red afterglow was observed for in the CaWO4∶Eu after exciting with 254 nm light due to Eu3+ transition from 5D0 to 7FJ (J=0, 1, 2,...Eu3+ activated CaWO4 was prepared by high temperature solid state reaction technique. Red afterglow was observed for in the CaWO4∶Eu after exciting with 254 nm light due to Eu3+ transition from 5D0 to 7FJ (J=0, 1, 2, 3,4). By the cal culation of the thermoluminescence spectrum of CaWO4∶Eu, we conclude that there were two types of trap centers: VCa″ was formed by substitution of Ca2+ by Eu3 + and complex traps were produced because of substitution of W6+ by Eu3+.展开更多
A modified shrinking unreacted-core model,based on thermogravimetric analysis,was developed to investigate CaSO4 decomposition in oxy-fuel combustion,especially under isothermal condition which is difficult to achieve...A modified shrinking unreacted-core model,based on thermogravimetric analysis,was developed to investigate CaSO4 decomposition in oxy-fuel combustion,especially under isothermal condition which is difficult to achieve in actual experiments due to high-temperature corrosion.A method was proposed to calculate the reaction rate constant for CaSO4 decomposition.Meanwhile,the diffusion of SO2 and O2,and the sintering of CaO were fully considered during the development of model.The results indicate that the model can precisely predict the decomposition of CaSO4 under high SO2 concentration（1100×10-6）.Concentrations of SO2 and O2 on the unreacted-core surface were found to increase first and then decrease with increasing temperature,and the average specific surface area and porosity of each CaO sintering layer decreased with increasing time.The increase of SO2 and/or O2 concentration inhibited CaSO4 decomposition.Moreover,the kinetics of CaSO4 decomposition had obvious dependence on temperature and the decomposition rate can be dramatically accelerated with increasing temperature.展开更多
文摘Spherical calcium carbonate was prepared by the reaction of sodium carbonate with calcium chloride at the presence of a protein like molecule, polyvinylpyrrolidone, as the template. The products were characterized by elemental analyses, XRD, SEM, and TG DSC respectively. The effects of polyvinylpyrrolidone on the crystal form and morphology of the as prepared CaCO3 were investigated. It was found that the aggregative shape of the produced calcium carbonate crystalline could be well controlled by adjusting the concentration of the polyvinylpyrrolidone template. This may be of important meanings to the biomimetic synthesis of novel inorganic materials.
文摘CaSO4 Nanorods/wires were synthesized in quaternary W/O microemulsion soluti on containing triton X-100, cyclohexane and n-pentanol. Transmission electro n microscopy (TEM) was utilized to characterize the shape and size of products a s-prepared, as well as electron diffraction (ED) pattern was obtained for desi gnated nanorods (wires). It is revealed that ù0 (molar ratio of water to surfa ctant),reactants concentration and aging time play an important role in the form ation of different morphologies and size of synthesized CaSO4 nanocrystal.
文摘Calcium fluoride nanoparticles were synthesized by water/cetyltrimethylammonium bromide (CTAB)/2-octanol microemulsion systems. X-ray powder diffraction analysis showed that the products were a single phase. The result of scanning electron microscopy confirmed that the average sizes of the calcium fluoride particles were below 100 nm in diameter. With decreasing water content and reaction time, the particle sizes decreased.
文摘The spherical CaCO3 composite was synthesized in the presence of the amphiphilic block copolymer, i.e. polystyrene-b-poly(acrylic acid). It was revealed by XRD analysis that the grains in the composite was calcite with great distortion. Infared and Raman analysis showed that the composite was composed of PS-b-PAA calcium salt and calcite, and the calcite was nano-scaled.
文摘合成了表面包覆 Si O2 的超细 Ca CO3 。通过 XPS,XRD对包覆表面层结构的分析 ,证实了 Si O2 以无定形包覆于 Ca CO3 表面 ,并在其表面形成了 Si- O- Ca键。对 Si O2 包覆超细 Ca CO3 的机理分析结果可知 :Na2 Si O3 的加入量是影响包覆效率的重要因素 ,由于硅酸易自聚 ,控制 Si O2 与 Ca CO3 的重量比约为4 %～ 5 %时为包覆的最佳点 ;Ca CO3 晶粒度大小影响分散性能 ,进而影响包覆效率 ,分散性能好的包覆效率较高。
文摘Eu3+ activated CaWO4 was prepared by high temperature solid state reaction technique. Red afterglow was observed for in the CaWO4∶Eu after exciting with 254 nm light due to Eu3+ transition from 5D0 to 7FJ (J=0, 1, 2, 3,4). By the cal culation of the thermoluminescence spectrum of CaWO4∶Eu, we conclude that there were two types of trap centers: VCa″ was formed by substitution of Ca2+ by Eu3 + and complex traps were produced because of substitution of W6+ by Eu3+.
基金Project(51276074)supported by the National Natural Science Foundation of ChinaProject(2014NY008)supported by Innovation Research Foundation of Huazhong University of Science and Technology,China
文摘A modified shrinking unreacted-core model,based on thermogravimetric analysis,was developed to investigate CaSO4 decomposition in oxy-fuel combustion,especially under isothermal condition which is difficult to achieve in actual experiments due to high-temperature corrosion.A method was proposed to calculate the reaction rate constant for CaSO4 decomposition.Meanwhile,the diffusion of SO2 and O2,and the sintering of CaO were fully considered during the development of model.The results indicate that the model can precisely predict the decomposition of CaSO4 under high SO2 concentration（1100×10-6）.Concentrations of SO2 and O2 on the unreacted-core surface were found to increase first and then decrease with increasing temperature,and the average specific surface area and porosity of each CaO sintering layer decreased with increasing time.The increase of SO2 and/or O2 concentration inhibited CaSO4 decomposition.Moreover,the kinetics of CaSO4 decomposition had obvious dependence on temperature and the decomposition rate can be dramatically accelerated with increasing temperature.
