The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrheniu...The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 k J/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.展开更多
Wollastonite glass ceramics were prepared using the reactive crystallization sintering method by mixing waste glass powders with gehlenite.The crystallization property,thermodynamics,and kinetics of the prepared wolla...Wollastonite glass ceramics were prepared using the reactive crystallization sintering method by mixing waste glass powders with gehlenite.The crystallization property,thermodynamics,and kinetics of the prepared wollastonite glass ceramics were determined by X-ray diffraction analysis,scanning electron microscopy,energy-dispersive spectroscopy,high-resolution transmission electron microscopy,and differential thermal analysis.Results showed that crystals of wollastonite and alumina could be found in the gehlenite through its reaction with silicon dioxide.The wollastonite crystals showed a lath shape with a certain length-to-diameter ratio.The crystals exhibited excellent bridging and reinforcing effects.In the crystallization process,the aluminum ions in gehlenite diffused into the glass and the silicon ions in the glass diffused into gehlenite.Consequently,the three-dimensional frame structure of gehlenite was partially damaged to form a chain-like wollastonite.The results of crystallization thermodynamics and kinetics indicated that crystallization reaction could occur spontaneously under a low temperature(1173 K),with 20 wt%gehlenite added as the reactive crystallization promoter.The crystallization activation energy was evaluated as 261.99 kJ/mol by using the Kissinger method.The compression strength of the wollastonite glass ceramic samples(7.5 cm×7.5 cm)reached 251 MPa.展开更多
Stable and monodispersed silver nanoparticles were produced through a mild,convenient,one-pot method based on the reduction of silver nitrate in the presence of poly(amic acid) (PAA) as a stabilizer.The surface plasma...Stable and monodispersed silver nanoparticles were produced through a mild,convenient,one-pot method based on the reduction of silver nitrate in the presence of poly(amic acid) (PAA) as a stabilizer.The surface plasma band transition was monitored along with time in the reaction mixture for three sets of experiments by ultraviolet-visible spectroscopy.Analysis of the data with the Avrami equation yielded n exponent with values between 0.5 and 1.5,demonstrating three-dimensional heterogeneous nucleation and diffusion-controlled growth,accompanied by soft impingement effect.XRD and TEM analyses show a softly agglomerated polycrystalline state and a nearly spherical morphology (<50 nm) of nanoparticles.The FT-IR result indicates that the PAA molecular structure could be hardly influenced by the formation of nanoparticles.展开更多
基金Projects(51171135,51371132,51471123) supported by the National Natural Science Foundation of ChinaProjects(2012K07-08,2013KJXX-61) supported by Key Science and Technology Program of Shaanxi Province,ChinaProject(2013JC14) supported by the Education Department Foundation of Shaanxi Province,China
文摘The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 k J/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.
基金Project(51308086)supported by the National Natural Science Foundation of ChinaProject(LJQ2015020)supported by the Program for Liaoning Excellent Talents in University,ChinaProject(2016RQ051)supported by the Program of Science-Technology Star for Young Scholars by the Dalian Municipality,China
文摘Wollastonite glass ceramics were prepared using the reactive crystallization sintering method by mixing waste glass powders with gehlenite.The crystallization property,thermodynamics,and kinetics of the prepared wollastonite glass ceramics were determined by X-ray diffraction analysis,scanning electron microscopy,energy-dispersive spectroscopy,high-resolution transmission electron microscopy,and differential thermal analysis.Results showed that crystals of wollastonite and alumina could be found in the gehlenite through its reaction with silicon dioxide.The wollastonite crystals showed a lath shape with a certain length-to-diameter ratio.The crystals exhibited excellent bridging and reinforcing effects.In the crystallization process,the aluminum ions in gehlenite diffused into the glass and the silicon ions in the glass diffused into gehlenite.Consequently,the three-dimensional frame structure of gehlenite was partially damaged to form a chain-like wollastonite.The results of crystallization thermodynamics and kinetics indicated that crystallization reaction could occur spontaneously under a low temperature(1173 K),with 20 wt%gehlenite added as the reactive crystallization promoter.The crystallization activation energy was evaluated as 261.99 kJ/mol by using the Kissinger method.The compression strength of the wollastonite glass ceramic samples(7.5 cm×7.5 cm)reached 251 MPa.
基金Project(10JJ5057)supported by the Hunan Provincial Natural Science Foundation of China
文摘Stable and monodispersed silver nanoparticles were produced through a mild,convenient,one-pot method based on the reduction of silver nitrate in the presence of poly(amic acid) (PAA) as a stabilizer.The surface plasma band transition was monitored along with time in the reaction mixture for three sets of experiments by ultraviolet-visible spectroscopy.Analysis of the data with the Avrami equation yielded n exponent with values between 0.5 and 1.5,demonstrating three-dimensional heterogeneous nucleation and diffusion-controlled growth,accompanied by soft impingement effect.XRD and TEM analyses show a softly agglomerated polycrystalline state and a nearly spherical morphology (<50 nm) of nanoparticles.The FT-IR result indicates that the PAA molecular structure could be hardly influenced by the formation of nanoparticles.
