TY  - JOUR
A1  - Qiu, X. L.
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Zhang, X. Q.
A1  - Hillenbrand, J.
A1  - Xia, Zhongfu
A1  - Gerhard, Reimund
A1  - Sessler, G. M.
T1  - Penetration of sulfur hexafluoride into cellular polypropylene films and its effect on the electric charging and electromechanical response of ferroelectrets
N2  - Cellular polypropylene (PP) films were treated with sulfur hexafluoride (SF6) gas in order to study the SF6 penetration behaviour and optimize the electric charging conditions. There were differences in the penetration of SF6 for different cellular PP materials, depending on the microscopic properties, which manifest themselves in the voided structure as well as in the mechanical stiffnesses of the cellular films. The penetration of SF6 after long-term pressure treatment is confirmed in strongly inflated cellular PP films with a low mechanical stiffness of about 1 MPa. No SF6 penetration occurs for slightly inflated cellular PP films with smaller void sizes and higher mechanical stiffnesses of around 5.8 MPa. The observed thickness variations, the higher charging fields during corona charging because of SF6 penetration and the SF6 environment, as well as the resulting electromechanical properties are discussed
Y1  - 2005
SN  - 0022-3727
ER  - 
TY  - JOUR
A1  - Mellinger, Axel
A1  - Singh, Rajeev
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Gerhard, Reimund
A1  - Lang, Sidney B.
T1  - Three-dimensional mapping of polarization profiles with thermal pulses
N2  - High-resolution, large-area three-dimensional mapping of polarization profiles in electret polymers was carried out by means of a fast thermal pulse technique with a focused laser beam. A lateral resolution of 38 mu m and a near- surface depth resolution of less than 0.5 mu m was achieved. At larger depths, fast thermal diffusion in the metal electrode rather than the laser spot size becomes the limiting factor for the lateral resolution. (c) 2005 American Institute of Physics
Y1  - 2005
SN  - 0003-6951
ER  - 
TY  - JOUR
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Gerhard, Reimund
T1  - Piezoelectric polyethylene terephthalate (PETP) foams : specifically designed and prepared ferroelectret films
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Wegener, Michael
A1  - Bergweiler, Steffen
A1  - Wirges, Werner
A1  - Pucher, Andreas
A1  - Tuncer, Enis
A1  - Gerhard, Reimund
T1  - Piezoelectric two-layer stacks of cellular polypropylene ferroelectrets : transducer response at audio and ultrasound frequencies
N2  - Piezoelectric cellular polypropylene films, so-called ferroelectrets, are assembled in a stack with two active transducer layers. The stack is characterized with respect to its linear and quadratic response in a frequency range from 1 kHz to 80 kHz. A relatively smooth frequency response in the sound-pressure level is found for the individual layers as well as for both layers driven in phase. The piezoelectric response of the two-layer stack is twice the response of an individual layer over a rather broad frequency range. Furthermore, the influence of the preparation conditions on the resonance frequency and the effect of the quadratic distortion on the radiated sound are investigated both for the individual transducer films in the stack and for the stack system as a whole
Y1  - 2005
SN  - 0885-3010
ER  -