TY  - JOUR
A1  - Flores Suárez, Rosaura
A1  - Mellinger, Axel
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Gerhard, Reimund
A1  - Singh, Rajeev
T1  - Thermal-pulse tomography of polarization distributions in a cylindrical geometry
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - Fast, three-dimensional polarization mapping in piezoelectric sensor cables was performed by means of the novel thermal-pulse tomography (TPT) technique with a lateral resolution of 200 mum. The active piezoelectric cable material (a copolymer of polyvinylidene fluoride with trifluoroethylene) was electrically poled with a point-to-cable corona discharge. A focused laser was employed to heat the opaque outer electrode, and the short-circuit current generated by the thermal pulse was used to obtain 3D polarization maps via the scale transformation method. The article describes the TPT technique as a fast non-destructive option for studying cylindrical geometries.
Y1  - 2006
U6  - https://doi.org/10.1109/TDEI.2006.258210
SN  - 1070-9878
VL  - 13
IS  - 5
SP  - 1030
EP  - 1035
PB  - IEEE
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Mellinger, Axel
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Mallepally, Rajendar Reddy
A1  - Gerhard, Reimund
T1  - Thermal and temporal stability of ferroelectret films made from cellular polypropylene/air composites
N2  - Ferroelectrets are thin films of polymer foams, exhibiting piezoelectric properties after electrical charging. Ferroelectret foams usually consist of a cellular polymer structure filled with air. Polymer-air composites are elastically soft due to their high air content as well as due to the size and shape of the polymer walls. Their elastically soft composite structure is one essential key for the working principle of ferroelectrets, besides the permanent trapping of electric charges inside the polymer voids. The elastic properties allow large deformations of the electrically charged voids. However, the composite structure can also possibly limit the stability and consequently the range of applications because of, e. g., penetration of gas and liquids accompanied by discharge phenomena or because of a mechanical pre-load which may be required during the application. Here, we discuss various stability aspects related to the piezoelectric properties of polypropylene ferroelectrets. Near and below room temperature, the piezoelectric effect and the stability of the trapped charges are practically independent from humidity during long-time storage in a humid atmosphere or water, or from operating conditions, such as continuous mechanical excitation. Thermal treatment of cellular polypropylene above -10 degrees C leads to a softening of the voided structure which is apparent from the decreasing values of the elastic modulus. This decrease results in an increase of the piezoelectric activity. Heating above 60 degrees C, however, leads to a decrease in piezoelectricity
Y1  - 2006
ER  - 
TY  - JOUR
A1  - Mellinger, Axel
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Mallepally, Rajendar Reddy
A1  - Gerhard, Reimund
T1  - Thermal and temporal stability of ferroelectret films made from cellular polypropylene/air composites
Y1  - 2006
ER  - 
TY  - JOUR
A1  - Mellinger, Axel
A1  - Flores Suárez, Rosaura
A1  - Singh, Rajeev
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Lang, Sidney B.
A1  - Gerhard, Reimund
T1  - High-resolution space-charge and polarization tomography with thermal pulses
N2  - Die Arbeit wurde am 13.03.2006 mit dem "BEST PAPER AWARD" des deutschen IEEE Instrumentation and Measurement (I&M) Chapter ausgezeichnet.
Y1  - 2006
SN  - 3-8007-2939-3
ER  -