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Laser-induced pressure pulses (LIPP's) of < 500 ps duration have been used to measure the ultrasonic attenuation in fluoroethylenepropylene (FEP), polyethyleneterephthalate (PETP) and polyimide (PI) as well as the charge, polarization, and piezoelectricity profiles in the thickness direction of polyvinylidenefluoride (PVDF) and FEP electrets with a resolution of 1 to 2 μm. Measurements on PVDF,...
A new method for the determination of the secondary emission yield of dielectrics is discussed. Results are given for Teflon, Aclar, Kapton, and Mylar. Surfaces of dielectrics irradiated with electrons of energies above 2 keV become negatively charged. For lower energies the number of back-scattered primaries plus backward emitted secondaries eventually exceeds that of the incoming primaries. Then...
By dispersing a non-conjugated luminescent polymer and an electron-transporting material, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), into a hole-transporting polymer, poly(9-vinylcarbazole) (PVK), we have achieved improved efficiencies for blue light-emitting diodes (LEDs) fabricated with a copolyester (CPE) containing isolated 1,2-dinaphthylethene units. Quantum efficiencies...
The results presented in this paper reveal a number of interesting features of the poling of PVDF: Room-temperature poling yields, depending on the applied field, no polarization at all or a spatially uniform polarization. In contrast, poling at elevated temperatures yields generally a nonuniform polarization with the poled region located close to the positive electrode at low fields, but extending...
Surfaces of materials irradiated by an electron beam emit low-energy secondary electrons and backscattered primary electrons. The total emission yield. defined as the ratio of the number of emitted electrons to the number of incident electrons. increases with decreasing primary energy. At the second crossover point this ratio equals unity and with further decreasing energy the emission yield reaches...
Polymer films used in the space environment are frequently exposed to partially penetrating electrons and show therefore often long-lasting charge-trapping effects. The physical processes responsible for the charge buildup and decay can only be understood with an accurate knowledge of the spatial charge profiles within the dielectrics. While calculations of charge profiles in radiation-charged dielectrics...
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