Hypereutectic Al-17.5Si （wt pct） and Al-25Si （wt pct） alloys with various content of rare earth Er were prepared by conventional casting technique. The effect of Er on the microstructure and properties of the hype...Hypereutectic Al-17.5Si （wt pct） and Al-25Si （wt pct） alloys with various content of rare earth Er were prepared by conventional casting technique. The effect of Er on the microstructure and properties of the hypereutectic Al-Si alloys was investigated using optical microscopy, scanning electron microscopy as well as friction and wear tests. It was found that optimal amount of Er exists in modifying the hypereutectic Al-Si alloys. An appropriate addition of Er improved the anti-wear properties, and reduced the friction coefficient of the hypereutectic Al-Si alloys studied. The primary silicon crystals in the hypereutectic Al-Si alloys were refined with the suitable addition of Er element. The modification mechanism was also discussed in this paper.展开更多
The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The res...The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The results show that minor Er in the studied alloy exists in the form of Al 3Er,only a few of Er in α Al based solid solution .Primary Al 3Er particles formed during solidification were often found at the center of aluminum grains and acted as heterogeneous nucleus, also increased the rate of nucleation, therefore the grain are remarkably refined. Trace Er addition to high pure aluminum is able to increase the mechanical properties of high pure Al, which is caused by fine grain strengthening, substructure strengthening and precipitation strengthening. The recrystallization temperature of Er doped aluminum increases above 50 ℃, which is caused by the pinning effect of highly dispersed fine Al 3Er precipitates on dislocations and sub grain boundaries.展开更多
Poly(methyl methacrylate) (PMMA) was used to wrap alumina siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon...Poly(methyl methacrylate) (PMMA) was used to wrap alumina siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon oil. Meanwhile a series of PMMA wrapped alumina-siloxane gel doped with rare earths was obtained and its ER effect was tested, like viscosity of different rare earth ion doped samples in different powder concentrations and at different temperatures, at the same time, leak current density and dielectric constant were measured. Results show that the ER effect of this suspension is remarkable, and its stability is much better. The condition of emulsion polymerization and the mechanism of effect are discussed.展开更多
A series of samples of alumina-siloxane gel wrapped by poly (methyl methacrylate) and doped with rare earths such as lanthanum, praseodymium, yttrium, gadolinium and europium were prepared. The structure features were...A series of samples of alumina-siloxane gel wrapped by poly (methyl methacrylate) and doped with rare earths such as lanthanum, praseodymium, yttrium, gadolinium and europium were prepared. The structure features were characterized by micrograph, X-ray fluorescence spectrum, X-ray diffraction spectrum, Fourier transform infrared spectrum and differential thermal analysis. Tests indicate that rare earths modify the electrorheological effects of the stable suspensions composed of samples stirred with silicon oil.展开更多
Polyparapheneylene (PPP) was doped by CeCl 4 and FeCl 3, and then electrorheological (ER) suspensions were prepared by polymer powder with high dielectric constants and silicone oil. Under electric field, the change...Polyparapheneylene (PPP) was doped by CeCl 4 and FeCl 3, and then electrorheological (ER) suspensions were prepared by polymer powder with high dielectric constants and silicone oil. Under electric field, the change of viscosity, leakage current density and relative physical constants were measured. The relationships among electric field strength, particle concentration, viscosity and leakage current density were discussed. The speed of electrorheological response and the recovery time were studied and corresponding mechanisms were investigated.展开更多
High efficiency frequency up conversion in trivalent erbium ion doped new fluoride glass matrix (ZnF 2 AlF 3 PbF 2 LiF) was investigated. Under 950 nm laser diode excitation, the glasses gave very intense gre...High efficiency frequency up conversion in trivalent erbium ion doped new fluoride glass matrix (ZnF 2 AlF 3 PbF 2 LiF) was investigated. Under 950 nm laser diode excitation, the glasses gave very intense green, weak red and violet emissions. The up conversion mechanism is discussed. In addition, the infrared transmittance spectrum, the Raman spectrum and the lifetime of the trivalent erbium states in the samples were measured. The results illustrate the large potential of these new glasses for photonic applications.展开更多
The upconversion fluorescence of Er^3＋ ions in LiKGdF5 ： Er^3＋, Dy^3＋ single crystal was studied under 785, 514.5, and 980 nm laser excitation. With the laser excitation set at 785 nm, strong green （centered at 5...The upconversion fluorescence of Er^3＋ ions in LiKGdF5 ： Er^3＋, Dy^3＋ single crystal was studied under 785, 514.5, and 980 nm laser excitation. With the laser excitation set at 785 nm, strong green （centered at 543 nm） upconversion emissions, as well as weak red （651 nm）, violet （406 nm）, and blue （470 nm） upconversion emissions were obtained. With 514.5 nm laser excitation, violet （406 nm） and blue （470 nm） upconversion emissions were observed. Under 980 nm laser excitation, strong green （543 nm） and weak red （651） emissions were also obtained. The laser power dependence of the upconverted emissions was investigated to understand the upconversion mechanism. The excited state absorption （ESA） and the energy transfer （ET） processes were discussed as the possible mechanisms for all upconversion emissions.展开更多
基金supported by the National Key Technology R&D Program of China(No.2009BAE80B00)
文摘Hypereutectic Al-17.5Si （wt pct） and Al-25Si （wt pct） alloys with various content of rare earth Er were prepared by conventional casting technique. The effect of Er on the microstructure and properties of the hypereutectic Al-Si alloys was investigated using optical microscopy, scanning electron microscopy as well as friction and wear tests. It was found that optimal amount of Er exists in modifying the hypereutectic Al-Si alloys. An appropriate addition of Er improved the anti-wear properties, and reduced the friction coefficient of the hypereutectic Al-Si alloys studied. The primary silicon crystals in the hypereutectic Al-Si alloys were refined with the suitable addition of Er element. The modification mechanism was also discussed in this paper.
文摘The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The results show that minor Er in the studied alloy exists in the form of Al 3Er,only a few of Er in α Al based solid solution .Primary Al 3Er particles formed during solidification were often found at the center of aluminum grains and acted as heterogeneous nucleus, also increased the rate of nucleation, therefore the grain are remarkably refined. Trace Er addition to high pure aluminum is able to increase the mechanical properties of high pure Al, which is caused by fine grain strengthening, substructure strengthening and precipitation strengthening. The recrystallization temperature of Er doped aluminum increases above 50 ℃, which is caused by the pinning effect of highly dispersed fine Al 3Er precipitates on dislocations and sub grain boundaries.
文摘Poly(methyl methacrylate) (PMMA) was used to wrap alumina siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon oil. Meanwhile a series of PMMA wrapped alumina-siloxane gel doped with rare earths was obtained and its ER effect was tested, like viscosity of different rare earth ion doped samples in different powder concentrations and at different temperatures, at the same time, leak current density and dielectric constant were measured. Results show that the ER effect of this suspension is remarkable, and its stability is much better. The condition of emulsion polymerization and the mechanism of effect are discussed.
文摘A series of samples of alumina-siloxane gel wrapped by poly (methyl methacrylate) and doped with rare earths such as lanthanum, praseodymium, yttrium, gadolinium and europium were prepared. The structure features were characterized by micrograph, X-ray fluorescence spectrum, X-ray diffraction spectrum, Fourier transform infrared spectrum and differential thermal analysis. Tests indicate that rare earths modify the electrorheological effects of the stable suspensions composed of samples stirred with silicon oil.
文摘Polyparapheneylene (PPP) was doped by CeCl 4 and FeCl 3, and then electrorheological (ER) suspensions were prepared by polymer powder with high dielectric constants and silicone oil. Under electric field, the change of viscosity, leakage current density and relative physical constants were measured. The relationships among electric field strength, particle concentration, viscosity and leakage current density were discussed. The speed of electrorheological response and the recovery time were studied and corresponding mechanisms were investigated.
文摘High efficiency frequency up conversion in trivalent erbium ion doped new fluoride glass matrix (ZnF 2 AlF 3 PbF 2 LiF) was investigated. Under 950 nm laser diode excitation, the glasses gave very intense green, weak red and violet emissions. The up conversion mechanism is discussed. In addition, the infrared transmittance spectrum, the Raman spectrum and the lifetime of the trivalent erbium states in the samples were measured. The results illustrate the large potential of these new glasses for photonic applications.
基金Project supported by a grant from Department of Education of Zhejiang Province (20060496)
文摘The upconversion fluorescence of Er^3＋ ions in LiKGdF5 ： Er^3＋, Dy^3＋ single crystal was studied under 785, 514.5, and 980 nm laser excitation. With the laser excitation set at 785 nm, strong green （centered at 543 nm） upconversion emissions, as well as weak red （651 nm）, violet （406 nm）, and blue （470 nm） upconversion emissions were obtained. With 514.5 nm laser excitation, violet （406 nm） and blue （470 nm） upconversion emissions were observed. Under 980 nm laser excitation, strong green （543 nm） and weak red （651） emissions were also obtained. The laser power dependence of the upconverted emissions was investigated to understand the upconversion mechanism. The excited state absorption （ESA） and the energy transfer （ET） processes were discussed as the possible mechanisms for all upconversion emissions.
