The thermally expandable microspheres（TEMs） were prepared via suspension polymerization with acrylonitrile（AN）, methyl methacrylate（MMA） and methyl acrylate（MA） as monomers and n-hexane as the blowing agent. M...The thermally expandable microspheres（TEMs） were prepared via suspension polymerization with acrylonitrile（AN）, methyl methacrylate（MMA） and methyl acrylate（MA） as monomers and n-hexane as the blowing agent. Meanwhile, a novel type of functional and conductive thermal expandable microsphere was obtained through strongly covering the surface of microsphere by conductive polymers with the mass loading of 1.5%. The optimal conditions to prepare high foaming ratio and equally distributed microcapsules were investigated with AN-MMA-MA in the proportion of 70%/20%/10%（m/m/m）, and 25 wt% of n-hexane in oil phase. The further investigation results showed that the unexpanded TEMs were about 30 μm in diameter and the maximum expansion ratio was nearly 125 times of original volume. The polypyrrole（PPy） was smoothly coated on the surface of the TEMs and the expansion property of PPy-coated TEMs was almost the same as the uncoated TEMs. Moreover, the structure and expanding performance of TEMs and PPy-coated TEMs were characterized by scanning electron microscopy（SEM）, laser particle size analyzer and dilatometer（DIL）.展开更多
An enhanced small-signal model is introduced to model the influence of the impact ionization effect on the performance of In As/Al Sb HFET, in which an optimized fitting function D（ωτi） in the form of least square...An enhanced small-signal model is introduced to model the influence of the impact ionization effect on the performance of In As/Al Sb HFET, in which an optimized fitting function D（ωτi） in the form of least square approximation is proposed in order to further enhance the accuracy in modeling the frequency dependency of the impact ionization effect.The enhanced model with D（ωτi） can accurately characterize the key S parameters of In As/Al Sb HFET in a wide frequency range with a very low error function EF. It is demonstrated that the new fitting function D（ωτi） is helpful in further improving the modeling accuracy degree.展开更多
To improve the electrochemical performances of α-MnO2 as electrode materials for supercapacitors, Sn-doped α-MnO2 in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As...To improve the electrochemical performances of α-MnO2 as electrode materials for supercapacitors, Sn-doped α-MnO2 in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As-prepared α-MnO2 presents nanorod shape and no other impurities exist. By ultraviolet-visible absorption spectroscopy, it is convinced that the band gaps of α-MnO2 decrease with increasing Sn-doping amount. Cyclic voltammetry investigation indicates that undoped and doped α-MnO2 all have regular capacitive response. As the scan rate enlarged, the profiles of curves gradually deviate from rectangle. Compared with undoped α-MnO2, doped α-MnO2 has larger specific capacitance. The specific capacitance of 3% doped α-MnO2 reaches 241.0 F/g while undoped α-MnO2 only has 173.0 F/g under 50 m A/g current density in galvanostatical charge-discharge measurement. Enhanced conductivity by Sn-doping is considered to account for doped sample＇s enhanced electrochemical specific capacitance.展开更多
Polyperfluorobutyne-2 (PPFB), a conjugated polymer, was characterized with IR, UV-VIS, fluorescence spectra etc. The electrical conductivities of the polymer doped with various dopants were investigated. The effect of...Polyperfluorobutyne-2 (PPFB), a conjugated polymer, was characterized with IR, UV-VIS, fluorescence spectra etc. The electrical conductivities of the polymer doped with various dopants were investigated. The effect of the molecular structure of PPFB on the electrical properties was discussed.展开更多
基金the National Natural ScienceFoundation of China(Nos.21206171,21376010)the Project of Natural Science Foundation of Beijing(No.2152012)+1 种基金the Young Elite Teacher Project(No.27170115004/027)the Project of 2011 Collaborative Innovation for Green Printing and Publishing Technology and the Project of Beijing Municipal Commission of Educatio (No.km201410005007)for the financial supports
文摘The thermally expandable microspheres（TEMs） were prepared via suspension polymerization with acrylonitrile（AN）, methyl methacrylate（MMA） and methyl acrylate（MA） as monomers and n-hexane as the blowing agent. Meanwhile, a novel type of functional and conductive thermal expandable microsphere was obtained through strongly covering the surface of microsphere by conductive polymers with the mass loading of 1.5%. The optimal conditions to prepare high foaming ratio and equally distributed microcapsules were investigated with AN-MMA-MA in the proportion of 70%/20%/10%（m/m/m）, and 25 wt% of n-hexane in oil phase. The further investigation results showed that the unexpanded TEMs were about 30 μm in diameter and the maximum expansion ratio was nearly 125 times of original volume. The polypyrrole（PPy） was smoothly coated on the surface of the TEMs and the expansion property of PPy-coated TEMs was almost the same as the uncoated TEMs. Moreover, the structure and expanding performance of TEMs and PPy-coated TEMs were characterized by scanning electron microscopy（SEM）, laser particle size analyzer and dilatometer（DIL）.
文摘An enhanced small-signal model is introduced to model the influence of the impact ionization effect on the performance of In As/Al Sb HFET, in which an optimized fitting function D（ωτi） in the form of least square approximation is proposed in order to further enhance the accuracy in modeling the frequency dependency of the impact ionization effect.The enhanced model with D（ωτi） can accurately characterize the key S parameters of In As/Al Sb HFET in a wide frequency range with a very low error function EF. It is demonstrated that the new fitting function D（ωτi） is helpful in further improving the modeling accuracy degree.
基金Funded by The National Natural Science Foundation of China(51402185)the Natural Science Foundation of Shanghai(13ZR1454700)
文摘To improve the electrochemical performances of α-MnO2 as electrode materials for supercapacitors, Sn-doped α-MnO2 in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As-prepared α-MnO2 presents nanorod shape and no other impurities exist. By ultraviolet-visible absorption spectroscopy, it is convinced that the band gaps of α-MnO2 decrease with increasing Sn-doping amount. Cyclic voltammetry investigation indicates that undoped and doped α-MnO2 all have regular capacitive response. As the scan rate enlarged, the profiles of curves gradually deviate from rectangle. Compared with undoped α-MnO2, doped α-MnO2 has larger specific capacitance. The specific capacitance of 3% doped α-MnO2 reaches 241.0 F/g while undoped α-MnO2 only has 173.0 F/g under 50 m A/g current density in galvanostatical charge-discharge measurement. Enhanced conductivity by Sn-doping is considered to account for doped sample＇s enhanced electrochemical specific capacitance.
基金Work supported by The National Natural Science Foundation of China.
文摘Polyperfluorobutyne-2 (PPFB), a conjugated polymer, was characterized with IR, UV-VIS, fluorescence spectra etc. The electrical conductivities of the polymer doped with various dopants were investigated. The effect of the molecular structure of PPFB on the electrical properties was discussed.
