TY  - JOUR
A1  - Sun, Zhuanlan
A1  - Zhang, Xiaoqing
A1  - Xia, Zhongfu
A1  - Qiu, Xunlin
A1  - Wirges, Werner
A1  - Gerhard, Reimund
A1  - Zeng, Changchun
A1  - Zhang, Chuck
A1  - Wang, Ben
T1  - Polarization and piezoelectricity in polymer films with artificial void structure
JF  - Applied physics : A, Materials science & processing
N2  - Laminated polymer-film systems with well-defined void structures were prepared from fluoroethylenepropylene (FEP) and polytetrafluoroethylene (PTFE) layers. First the PTFE films were patterned and then fusion-bonded with the FEP films. The laminates were subjected to either corona or contact charging in order to obtain the desired piezoelectricity. The build-up of the "macro-dipoles" in the laminated films was studied by recording the electric hysteresis loops. The resulting electro-mechanical properties were investigated by means of dielectric resonance spectroscopy (DRS) and direct measurements of the stress-strain relationship. Moreover, the thermal stability of the piezoelectric d (33) coefficient was investigated at elevated temperatures and via thermally stimulated discharge (TSD) current measurements in short circuit. For 150 mu m thick laminated films, consisting of one 25 mu m thick PTFE layer, two 12.5 mu m thick FEP layers, and a void of 100 mu m height, the critical voltage necessary for the build-up of the "macro-dipoles" in the inner voids was approximately 1400 V, which agrees with the value calculated from the Paschen Law. A quasi-static piezoelectric d (33) coefficient up to 300 pC/N was observed after corona charging. The mechanical properties of the film systems are highly anisotropic. At room temperature, the Young's moduli of the laminated film system are around 0.37 MPa in the thickness direction and 274 MPa in the lateral direction, respectively. Using these values, the theoretical shape anisotropy ratio of the void was calculated, which agrees well with experimental observation. Compared with films that do not exhibit structural regularity, the laminates showed improved thermal stability of the d (33) coefficients. The thermal stability of d (33) can be further improved by pre-aging. E.g., the reduction of the d (33) value in the sample pre-aged at 150A degrees C for 5 h was less than 5% after annealing for 30 h at a temperature of 90A degrees C.
Y1  - 2011
U6  - https://doi.org/10.1007/s00339-011-6481-2
SN  - 0947-8396
VL  - 105
IS  - 1
SP  - 197
EP  - 205
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Gerhard, Reimund
A1  - Xia, Zhongfu
A1  - Künstler, Wolfgang
A1  - Pucher, Andreas
T1  - Preliminary study of multi-layer space-charge electrets with piezoelectric properties from porous and non- porous Teflon films
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Xia, Zhongfu
A1  - Gerhard, Reimund
A1  - Künstler, Wolfgang
A1  - Wedel, Armin
A1  - Danz, Rudi
T1  - High surface-charge stability of porous polytetrafluoroethylene electret films at room and elvated temperatures
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Künstler, Wolfgang
A1  - Xia, Zhongfu
A1  - Weinhold, Till
A1  - Pucher, Andreas
A1  - Gerhard, Reimund
T1  - Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Gerhard, Reimund
A1  - Künstler, Wolfgang
A1  - Görne, Thomas
A1  - Pucher, Andreas
A1  - Weinhold, Till
A1  - Seiß, Martin
A1  - Xia, Zhongfu
A1  - Wedel, Armin
A1  - Danz, Rudi
T1  - Porous polytetrafluoroethylene space-charge electrets for piezoelectrical applications
Y1  - 2000
ER  - 
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  -