The influence of thermomechanical aging on microstructure and mechanical properties of 2519A aluminum alloy was investigated by means of microhardness test,tensile test,optical microscopy (OM) and transmission electro...The influence of thermomechanical aging on microstructure and mechanical properties of 2519A aluminum alloy was investigated by means of microhardness test,tensile test,optical microscopy (OM) and transmission electron microscopy (TEM).The results show that 50% cold rolling deformation prior to aging is beneficial since it promotes a more homogeneous distribution of the precipitation phase and reduces the number of precipitation phase on the grain boundaries,and thus shrinks the total volume of precipitation-free zones at grain and sub-grain boundaries.As a result,the tensile properties of 2519A aluminum alloy have been significantly improved.展开更多
Three-dimensional （3D） hierarchical Pt-Cu tetragonal, highly branched, and dendritic superstructures have been synthesized by a facile template-free hydrothermal approach, showing growth patterns along （111, 110）,...Three-dimensional （3D） hierarchical Pt-Cu tetragonal, highly branched, and dendritic superstructures have been synthesized by a facile template-free hydrothermal approach, showing growth patterns along （111, 110）, （111）, and （100） planes, respectively. These structures have been characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy （EDX）, inductively coupled plasma optical emission spectrometry （ICP-OES） and a detailed formation mechanism has been developed, which shows that the in situ formed 12 and the galvanic replacement reaction between Cu and Pt4, may guide the formation of these superstructures. The comparative electrocatalytic properties have been investigated for methanol and ethanol oxidation. Due to their interconnected arms, sufficient absorption sites, and exposed surfaces, these superstructures exhibit enhanced electrocatalytic performance for electro-oxidation of methanol and ethanol when compared with commercial Pt/C and Pt black.展开更多
Water-soluble gelatin-PbS bionanocomposites （BNCs） were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy （TEM）, X-ray diffrac...Water-soluble gelatin-PbS bionanocomposites （BNCs） were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, UV-vis absorption spectra （UV-vis）, Fourier transform infrared spectra （FT-IR） and circular dichroism （CD）. FT-IR data were used to envis- age the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2＋ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less c^-helix content and more open structures （[3-sheet, r-turn, or expanded）. A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K （298/303/308 K： 3.11/2.00/1.60 × 10^6 tool/L） at three different temperatures were calculated based on this formula. Thermodynamic parameters such as AG^θ, △Hθ and △S^θ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous （AG^θ 〈 0）, and enthalpy-driven （△H^8 〈 0）.展开更多
基金Project(2005CB623706) supported by the National Basic Research Program of China
文摘The influence of thermomechanical aging on microstructure and mechanical properties of 2519A aluminum alloy was investigated by means of microhardness test,tensile test,optical microscopy (OM) and transmission electron microscopy (TEM).The results show that 50% cold rolling deformation prior to aging is beneficial since it promotes a more homogeneous distribution of the precipitation phase and reduces the number of precipitation phase on the grain boundaries,and thus shrinks the total volume of precipitation-free zones at grain and sub-grain boundaries.As a result,the tensile properties of 2519A aluminum alloy have been significantly improved.
基金This work was supported by the National Natural Science Foundation of China （Nos. 91127040 and 21221062）, and the State Key Project of Fundamental Research for Nanoscience and Nanotechnology （No. 2011CB932402）.
文摘Three-dimensional （3D） hierarchical Pt-Cu tetragonal, highly branched, and dendritic superstructures have been synthesized by a facile template-free hydrothermal approach, showing growth patterns along （111, 110）, （111）, and （100） planes, respectively. These structures have been characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy （EDX）, inductively coupled plasma optical emission spectrometry （ICP-OES） and a detailed formation mechanism has been developed, which shows that the in situ formed 12 and the galvanic replacement reaction between Cu and Pt4, may guide the formation of these superstructures. The comparative electrocatalytic properties have been investigated for methanol and ethanol oxidation. Due to their interconnected arms, sufficient absorption sites, and exposed surfaces, these superstructures exhibit enhanced electrocatalytic performance for electro-oxidation of methanol and ethanol when compared with commercial Pt/C and Pt black.
基金supported by the National Natural Science Foundation of China(21067001)Natural Science Foundation of Guangxi Province(0991083)Innovation Project of Guangxi University for Nationalities(gxun-chx2012091)
文摘Water-soluble gelatin-PbS bionanocomposites （BNCs） were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, UV-vis absorption spectra （UV-vis）, Fourier transform infrared spectra （FT-IR） and circular dichroism （CD）. FT-IR data were used to envis- age the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2＋ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less c^-helix content and more open structures （[3-sheet, r-turn, or expanded）. A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K （298/303/308 K： 3.11/2.00/1.60 × 10^6 tool/L） at three different temperatures were calculated based on this formula. Thermodynamic parameters such as AG^θ, △Hθ and △S^θ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous （AG^θ 〈 0）, and enthalpy-driven （△H^8 〈 0）.
