Carbon fibers（CFs） were coated with a nickel-phosphorus（Ni-P） film using an electroless plating process. The morphology, elemental composition and phases in the coating layer of the CFs were investigated by scanni...Carbon fibers（CFs） were coated with a nickel-phosphorus（Ni-P） film using an electroless plating process. The morphology, elemental composition and phases in the coating layer of the CFs were investigated by scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS） and X-ray diffraction（XRD）, respectively. Wet paper-making method was used to prepare nickle coated carbon fiber paper（NCFP）. Vacuum assisted infusion molding process（VAIMP） was employed to manufacture the NCFP reinforced epoxy composites, and carbon fiber paper（CFP） reinforced epoxy composites were also produced as a comparison. Electromagnetic interference（EMI） shielding properties of the composites were measured in the 3.22-4.9 GHz frequency range using waveguide method. Both NCFP and CFP reinforced epoxy composites of 0.5 mm thickness exhibited high EMI shielding effectiveness（SE） at 8wt% fiber content, 35 d B and 30 d B, respectively, and reflection was the dominant shielding mechanism.展开更多
The origin of the shallow decay segment in γ-ray bursts' (GRB) early light curves remains a mystery, especially those cases with a long-lived plateau followed by an abrupt falloff. In this paper, we propose to un...The origin of the shallow decay segment in γ-ray bursts' (GRB) early light curves remains a mystery, especially those cases with a long-lived plateau followed by an abrupt falloff. In this paper, we propose to understand the origins of the long-lived plateau by considering the solidification of newborn quark stars with latent heat released as energy injection to the GRB afterglow, and we suggest that an abrupt falloff would naturally appear after the plateau due to the energy injection cutoff. We estimated the total latent heat released during the phase transition of quark stars from liquid to solid states to be on the order of ～ 1051 ergs, which is comparable to the emission energy in the shallow decay segment. We also estimated the time scale of radiating the latent heat through thermal photon emission, and found that the time scale agrees with the observations. Based on our estimation, we analyzed the process of energy injection to GRB afterglow. We will show that the steady latent heat of quark star phase transition will continuously inject into the GRB afterglow in a form similar to that of a Poynting-flux-dominated outflow and naturally produce the shallow decay phase and the abrupt falloff after the plateau. We conclude that the latent heat of quark star phase transition is an important contribution to the shallow decay radiation in some GRB afterglows, and explains the long-lived plateau followed by an abrupt falloff, if pulsar-like stars are really (solid) quark stars.展开更多
基金Funded by the National Natural Science Foundation of China(No.51373129)
文摘Carbon fibers（CFs） were coated with a nickel-phosphorus（Ni-P） film using an electroless plating process. The morphology, elemental composition and phases in the coating layer of the CFs were investigated by scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS） and X-ray diffraction（XRD）, respectively. Wet paper-making method was used to prepare nickle coated carbon fiber paper（NCFP）. Vacuum assisted infusion molding process（VAIMP） was employed to manufacture the NCFP reinforced epoxy composites, and carbon fiber paper（CFP） reinforced epoxy composites were also produced as a comparison. Electromagnetic interference（EMI） shielding properties of the composites were measured in the 3.22-4.9 GHz frequency range using waveguide method. Both NCFP and CFP reinforced epoxy composites of 0.5 mm thickness exhibited high EMI shielding effectiveness（SE） at 8wt% fiber content, 35 d B and 30 d B, respectively, and reflection was the dominant shielding mechanism.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10973002, 10973003 and 10935001)the National Basic Research Program of China (Grant Nos. 2009CB24901, 2009CB824800)the John Templeton Foundation and the National Fund for Fostering Talents of Basic Science (Grant No. J0630311)
文摘The origin of the shallow decay segment in γ-ray bursts' (GRB) early light curves remains a mystery, especially those cases with a long-lived plateau followed by an abrupt falloff. In this paper, we propose to understand the origins of the long-lived plateau by considering the solidification of newborn quark stars with latent heat released as energy injection to the GRB afterglow, and we suggest that an abrupt falloff would naturally appear after the plateau due to the energy injection cutoff. We estimated the total latent heat released during the phase transition of quark stars from liquid to solid states to be on the order of ～ 1051 ergs, which is comparable to the emission energy in the shallow decay segment. We also estimated the time scale of radiating the latent heat through thermal photon emission, and found that the time scale agrees with the observations. Based on our estimation, we analyzed the process of energy injection to GRB afterglow. We will show that the steady latent heat of quark star phase transition will continuously inject into the GRB afterglow in a form similar to that of a Poynting-flux-dominated outflow and naturally produce the shallow decay phase and the abrupt falloff after the plateau. We conclude that the latent heat of quark star phase transition is an important contribution to the shallow decay radiation in some GRB afterglows, and explains the long-lived plateau followed by an abrupt falloff, if pulsar-like stars are really (solid) quark stars.
