The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized ...The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized by CLDHs to reconstruct the layered structure and aggregate around CLDHs. The immobilization amount of sulfate ions by CLDHs reaches 4.74×10^-3 mol/g, while the increasing amount indicates non-linear relation with the addition of CLDHs. The incorporation of CLDHs decreases the amount of ettringite formed to limit the expansion of cement paste, which decays the sulfate reaction to enhance the sulfate resistance of concrete.展开更多
The XRD patterns of different calcined layered double hydroxides(CLDH) and their ultraviolet absorbing and screening properties have been investigated. It has been found that a calcined layered double hydroxide(CLDH) ...The XRD patterns of different calcined layered double hydroxides(CLDH) and their ultraviolet absorbing and screening properties have been investigated. It has been found that a calcined layered double hydroxide(CLDH) containing zinc is very effective in absorbing and screening ultraviolet radiation. The crystal structure of a CLDH containing zinc is similar to that of ZnO and is not related to the crystal structure of Al 2O 3. It is not a simple combination of zinc oxide and aluminium oxide but a calcined layered double hydroxide in which part of the Zn 2+ cations is replaced by Al 3+ cations.展开更多
The adsorbing effect of calcined layered double hydroxide （CLDH） for chloride ions in simulated concrete pore （SCP） solutions was investigated with the potentiodynamic polarization method, impedance measurement, i...The adsorbing effect of calcined layered double hydroxide （CLDH） for chloride ions in simulated concrete pore （SCP） solutions was investigated with the potentiodynamic polarization method, impedance measurement, ion selective electrode analysis and XRD. CLDH could effectively adsorb Cl^- and increase pH value in SCP solutions containing NaCl. The chloride to hydroxyl ions ratio （[C1^-]/[OH^-]） of the solution greatly decreased by CLDH treatment. In CLDH treated SCP solution with CI-, the pitting potential of carbon steel notably increased, and the surface impedance was much higher, indicating strengthened passivation. The process of CLDH adsorbing chloride ions from SCP solutions was accompanied with the reconstruction of the layered structure.展开更多
The reaction of ethanol with propylene oxide over calcined layered double hydroxides(CLDH) was investigated. The results show that CLDH has a good activity and a good selectivity, but the activity and the selectivity ...The reaction of ethanol with propylene oxide over calcined layered double hydroxides(CLDH) was investigated. The results show that CLDH has a good activity and a good selectivity, but the activity and the selectivity of CLDH decrease when CLDH reforms LDH- the so called 'memory effect'. The influence of the 'memory effect' on the CLDH returning to LDH was studied by the hydration reaction. It is shown that the 'memory effect' is not complete, and the decreases of the Mg/Al molar ratio of LDH and the crystallite size due to the increase of the hydration reaction time result in the drop of the activity and the selectivity.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51508191,11502081,51502272,and 51608409)the Foundation from MWR Center for Levee Safety and Disease Prevention Research,State Key Laboratory of Silicates Materials for Architectures of Wuhan University of Technology(SYSJJ2014-3,SYSJJ2018-15)+1 种基金the Foundation from Engineering Research Center of Nano-Geomaterials of Ministry of Education,China University of Geosciences(NGM2018KF011)the Fundamental Research Funds for the Central Universities,China University of Geosciences
文摘The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized by CLDHs to reconstruct the layered structure and aggregate around CLDHs. The immobilization amount of sulfate ions by CLDHs reaches 4.74×10^-3 mol/g, while the increasing amount indicates non-linear relation with the addition of CLDHs. The incorporation of CLDHs decreases the amount of ettringite formed to limit the expansion of cement paste, which decays the sulfate reaction to enhance the sulfate resistance of concrete.
文摘The XRD patterns of different calcined layered double hydroxides(CLDH) and their ultraviolet absorbing and screening properties have been investigated. It has been found that a calcined layered double hydroxide(CLDH) containing zinc is very effective in absorbing and screening ultraviolet radiation. The crystal structure of a CLDH containing zinc is similar to that of ZnO and is not related to the crystal structure of Al 2O 3. It is not a simple combination of zinc oxide and aluminium oxide but a calcined layered double hydroxide in which part of the Zn 2+ cations is replaced by Al 3+ cations.
基金Funded by the National Natural Science Foundation of China(51171014 and 51210001)the Fundamental Research Funds for the Central Universities(No.ZZ1116)
文摘The adsorbing effect of calcined layered double hydroxide （CLDH） for chloride ions in simulated concrete pore （SCP） solutions was investigated with the potentiodynamic polarization method, impedance measurement, ion selective electrode analysis and XRD. CLDH could effectively adsorb Cl^- and increase pH value in SCP solutions containing NaCl. The chloride to hydroxyl ions ratio （[C1^-]/[OH^-]） of the solution greatly decreased by CLDH treatment. In CLDH treated SCP solution with CI-, the pitting potential of carbon steel notably increased, and the surface impedance was much higher, indicating strengthened passivation. The process of CLDH adsorbing chloride ions from SCP solutions was accompanied with the reconstruction of the layered structure.
文摘The reaction of ethanol with propylene oxide over calcined layered double hydroxides(CLDH) was investigated. The results show that CLDH has a good activity and a good selectivity, but the activity and the selectivity of CLDH decrease when CLDH reforms LDH- the so called 'memory effect'. The influence of the 'memory effect' on the CLDH returning to LDH was studied by the hydration reaction. It is shown that the 'memory effect' is not complete, and the decreases of the Mg/Al molar ratio of LDH and the crystallite size due to the increase of the hydration reaction time result in the drop of the activity and the selectivity.
