In order to explore the effect mechanism of solvent on the synthesis of the metal organic framework materials, the microscopic interaction between solvent and framework and the effects of N,N-dimethyl-formamide(DMF) o...In order to explore the effect mechanism of solvent on the synthesis of the metal organic framework materials, the microscopic interaction between solvent and framework and the effects of N,N-dimethyl-formamide(DMF) or N-methyl- 2-pyrrolidone(NMP) on solvothermal synthesis of [Zn4O(BDC)3]8 were investigated through a combined DFT and experimental study. XRD and SEM showed that the absorbability of NMP in the pore of [Zn4O(BDC)3]8 was weaker than that of DMF. The thermal decomposition temperature of [Zn4O(BDC)3]8 synthesized in DMF was higher than that in NMP according to TG and FT-IR. In addition, the nitrogen sorption isotherms indicated that NMP improved gas sorption property of [Zn4O(BDC)3]8. The COSMO optimized calculations indicated that the total energy of Zn4O(BDC)3 in NMP was higher than that in DMF, and compared with non-solvent system, the charge of zinc atoms decreased and the charge value was the smallest in NMP. Furthermore, the interaction of DMF, NMP or DEF in [Zn4O(BDC)3]8 crystal model was calculated by DFT method. The results suggested that NMP should be easier to be removed from pore of materials than DMF from the point of view of energy state. It can be concluded that NMP was a favorable solvent to synthesize [Zn4O(BDC)3]8 and the microscopic mechanism was that the binding force between Zn4O(BDC)3 and NMP molecule was weaker than DMF.展开更多
The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO ...The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.展开更多
基金Project(51104185)supported by the National Natural Science Foundation of ChinaProject(2010QZZD003)supported by the Key Project of Central South University of Fundamental Research Funds for the Central Universities of China
文摘In order to explore the effect mechanism of solvent on the synthesis of the metal organic framework materials, the microscopic interaction between solvent and framework and the effects of N,N-dimethyl-formamide(DMF) or N-methyl- 2-pyrrolidone(NMP) on solvothermal synthesis of [Zn4O(BDC)3]8 were investigated through a combined DFT and experimental study. XRD and SEM showed that the absorbability of NMP in the pore of [Zn4O(BDC)3]8 was weaker than that of DMF. The thermal decomposition temperature of [Zn4O(BDC)3]8 synthesized in DMF was higher than that in NMP according to TG and FT-IR. In addition, the nitrogen sorption isotherms indicated that NMP improved gas sorption property of [Zn4O(BDC)3]8. The COSMO optimized calculations indicated that the total energy of Zn4O(BDC)3 in NMP was higher than that in DMF, and compared with non-solvent system, the charge of zinc atoms decreased and the charge value was the smallest in NMP. Furthermore, the interaction of DMF, NMP or DEF in [Zn4O(BDC)3]8 crystal model was calculated by DFT method. The results suggested that NMP should be easier to be removed from pore of materials than DMF from the point of view of energy state. It can be concluded that NMP was a favorable solvent to synthesize [Zn4O(BDC)3]8 and the microscopic mechanism was that the binding force between Zn4O(BDC)3 and NMP molecule was weaker than DMF.
基金Project (BK2010392) supported by the Natural Science Foundation of Jiangsu Province of ChinaProject (3212000502) supported by the Innovation Foundation of Southeast University,China
文摘The microstructure and mechanical properties of Mg94Zn2Y4 extruded alloy containing long-period stacking ordered structures were systematically investigated by SEM and TEM analyses. The results show that the 18R-LPSO structure and α-Mg phase are observed in cast Mg94Zn2Y4 alloy. After extrusion, the LPSO structures are delaminated and Mg-slices with width of 50-200 nm are generated. By ageing at 498 K for 36 h, the ageing peak is attained andβ′phase is precipitated. Due to this novel precipitation, the microhardness ofα-Mg matrix increases apparently from HV108.9 to HV129.7. While the microhardness for LPSO structure is stabilized at about HV145. TEM observations and SAED patterns indicate that the β′ phase has unique orientation relationships betweenα-Mg and LPSO structures, the direction in the close-packed planes ofβ′precipitates perpendicular to that ofα-Mg and LPSO structures. The ultimate tensile strength for the peak-aged alloy achieves 410.7 MPa and the significant strength originates from the coexistence ofβ′precipitates and 18R-LPSO structures.
