The thermodynamic characterization as well as the rheological characterization of the A201 alloy were conducted.Thermodynamic simulations (CALPHAD method) and calorimetric experiments were performed to determine the s...The thermodynamic characterization as well as the rheological characterization of the A201 alloy were conducted.Thermodynamic simulations (CALPHAD method) and calorimetric experiments were performed to determine the solidus and liquidus temperatures, the melting range and the sensitivity of the solid fraction at the thixoforming temperatures.The rheology of aluminium alloy A201 was examined using a high temperature Searle rheometer.The flow behaviour was analyzed with concentric cylinders of graphite to avoid chemical interactions with the liquid or semi-solid aluminium.The rotational body was grooved to prevent a phenomenon called wall slippage.Continuous cooling experiment was used to observe the shear rate effects on the flow behaviour.It can be seen that the viscosity level decreases at higher shear rates.Shear rate jump experiment was carried out to evaluate the steady state flow curve within the analyzed shear rate range from 60 s-1 to 260 s-1.It is found that the power law indexes are-1.35 and-1.49 for 35% and 45% solid fraction, respectively.Finally, some mechanical property data of as-cast and as-thixoformed A201 alloy are included indicating the potential for high strength applications.展开更多
A scorpion-shaped di-NBD(4-substituted-7-nitrobenzoxadiazole) derivative of cholesterol(Chol-2NBD) was designed and synthesized. The gelation behaviors of the compound in a series of single and mixed liquids were test...A scorpion-shaped di-NBD(4-substituted-7-nitrobenzoxadiazole) derivative of cholesterol(Chol-2NBD) was designed and synthesized. The gelation behaviors of the compound in a series of single and mixed liquids were tested. It was shown that the compound is an effective gelator for mixture liquids of THF and benzene at room temperature. Furthermore, FT-IR and temperature-/concentration-dependent 1H NMR spectroscopy studies revealed that hydrogen bonding and π-π stacking among the molecules of Chol-2NBD are two main driving forces for the physical gelation of the mixture liquids. Interestingly, as observed in the gelation test and confirmed by rheological studies, the Chol-2NBD-THF/benzene gel systems, at least the one with 2:8 of the volume ratio of THF to benzene, are mechanically stable, but very sensitive to the stimulus of shear stress, which means that the gel changes into a liquid upon shaking. More interestingly, the liquid returns to gel instantly once the shear stress is removed. This phase transition process could be repeated for many times at room temperature. In addition, primary tests demonstrated that the fluorescence emission of Chol-2NBD is significantly quenched by the presence of water, ammonia water, or ammonia gas, but the emission recovers after evaporation of them. Further detailed investigation is under progress.展开更多
For the materials that simultaneously exhibit piezoelectric and semiconductor properties,such as wurtzite Zn O,Ga N and In N,as well as two-dimensional single Mo S2,piezoelectric charges induced by externally applied ...For the materials that simultaneously exhibit piezoelectric and semiconductor properties,such as wurtzite Zn O,Ga N and In N,as well as two-dimensional single Mo S2,piezoelectric charges induced by externally applied strain can tune/control carrier transport at a metal-semiconductor contact or semiconductor junction,which is named piezotronic effect.Metal-semiconductor-metal piezotronic transistors are key piezotronic nanodevices for electromechanical applications,and they are typical nonlinear elements.In this paper,a simplified current-voltage analysis solution of piezotronic transistors is developed,which can be used for circuit design and simulation.Furthermore,the typical nonlinear circuit:Chua's circuit based on piezotronic transistors is simulated.We find that the output signal of the piezotronic transistor circuit can be switched and changed asymmetrically by externally applied strain.This study provides insight into the nonlinear properties of the piezotronic transistor,as well as guidance for piezotronic transistor nonlinear circuit application.展开更多
基金the "Ministerio de Ciencia e Innovación" and to the "Fondos FEDER",project "Integrauto" PSE-370000-2008-03the Basque Government,project "ETORTEK, Manufacturing 0.0 II",for their financial support
文摘The thermodynamic characterization as well as the rheological characterization of the A201 alloy were conducted.Thermodynamic simulations (CALPHAD method) and calorimetric experiments were performed to determine the solidus and liquidus temperatures, the melting range and the sensitivity of the solid fraction at the thixoforming temperatures.The rheology of aluminium alloy A201 was examined using a high temperature Searle rheometer.The flow behaviour was analyzed with concentric cylinders of graphite to avoid chemical interactions with the liquid or semi-solid aluminium.The rotational body was grooved to prevent a phenomenon called wall slippage.Continuous cooling experiment was used to observe the shear rate effects on the flow behaviour.It can be seen that the viscosity level decreases at higher shear rates.Shear rate jump experiment was carried out to evaluate the steady state flow curve within the analyzed shear rate range from 60 s-1 to 260 s-1.It is found that the power law indexes are-1.35 and-1.49 for 35% and 45% solid fraction, respectively.Finally, some mechanical property data of as-cast and as-thixoformed A201 alloy are included indicating the potential for high strength applications.
基金supported by the National Natural Science Foundation of China(91027017 and 21273141)the Ministry of Education of China for its"Program for Changjiang Scholars and Innovative Research Team in University"of China(IRT1070)
文摘A scorpion-shaped di-NBD(4-substituted-7-nitrobenzoxadiazole) derivative of cholesterol(Chol-2NBD) was designed and synthesized. The gelation behaviors of the compound in a series of single and mixed liquids were tested. It was shown that the compound is an effective gelator for mixture liquids of THF and benzene at room temperature. Furthermore, FT-IR and temperature-/concentration-dependent 1H NMR spectroscopy studies revealed that hydrogen bonding and π-π stacking among the molecules of Chol-2NBD are two main driving forces for the physical gelation of the mixture liquids. Interestingly, as observed in the gelation test and confirmed by rheological studies, the Chol-2NBD-THF/benzene gel systems, at least the one with 2:8 of the volume ratio of THF to benzene, are mechanically stable, but very sensitive to the stimulus of shear stress, which means that the gel changes into a liquid upon shaking. More interestingly, the liquid returns to gel instantly once the shear stress is removed. This phase transition process could be repeated for many times at room temperature. In addition, primary tests demonstrated that the fluorescence emission of Chol-2NBD is significantly quenched by the presence of water, ammonia water, or ammonia gas, but the emission recovers after evaporation of them. Further detailed investigation is under progress.
基金supported by the Natural Science Foundation of Gansu Province,China(Grant No.145RJZA226)Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2013-35)Beijing Municipal Commission of Science and Technology(Grant Nos.Z131100006013005 and Z131100006013004)
文摘For the materials that simultaneously exhibit piezoelectric and semiconductor properties,such as wurtzite Zn O,Ga N and In N,as well as two-dimensional single Mo S2,piezoelectric charges induced by externally applied strain can tune/control carrier transport at a metal-semiconductor contact or semiconductor junction,which is named piezotronic effect.Metal-semiconductor-metal piezotronic transistors are key piezotronic nanodevices for electromechanical applications,and they are typical nonlinear elements.In this paper,a simplified current-voltage analysis solution of piezotronic transistors is developed,which can be used for circuit design and simulation.Furthermore,the typical nonlinear circuit:Chua's circuit based on piezotronic transistors is simulated.We find that the output signal of the piezotronic transistor circuit can be switched and changed asymmetrically by externally applied strain.This study provides insight into the nonlinear properties of the piezotronic transistor,as well as guidance for piezotronic transistor nonlinear circuit application.
