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  - Flores Suárez, Rosaura
A1  - Ganesan, Lakshmi Meena
A1  - Wirges, Werner
A1  - Gerhard, Reimund
A1  - Mellinger, Axel
T1  - Imaging liquid crystals dispersed in a ferroelectric polymer matrix by means of thermal-pulse tomography
N2  - A new arrangement of the optical elements in a Thermal-Pulse-Tomography (TPT) setup allows to scan micrometer structures in composite and heterogeneous samples such as polymer-dispersed liquid crystals (PDLCs). The non-destructive TPT technique allows the determination of three-dimensional profiles of polarization and space charge in dielectrics. The samples under study were 12 mu m thick films of a copolymer of vinylidene fluoride with trifluoroethylene P(VDF- TrFE) (65/35) with embedded liquid-crystal droplets. The poling process was performed in direct contact well above the coercive field of the copolymer. The 3D map obtained from scanning with a 10 mu m wide spot shows elliptically shaped areas with liquid-crystal droplets. Considering the droplets as oblate spheroids, their major axis lies in the x-y plane, while their minor axis in the z direction measures 0.5 mu m or more. This result is in good agreement with scanning electron micrographs. It is believed that the major axis is overestimated due to imaging of liquid-crystal clusters.
Y1  - 2010
UR  - http://ieeexplore.ieee.org/servlet/opac?punumber=94
U6  - https://doi.org/10.1109/TDEI.2010.5539683
SN  - 1070-9878
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  - 
TY  - JOUR
A1  - Pham, Cong Duc
A1  - Petre, Anca
A1  - Berquez, Laurent
A1  - Flores Suárez, Rosaura
A1  - Mellinger, Axel
A1  - Wirges, Werner
A1  - Gerhard, Reimund
T1  - 3D high-resolution mapping of polarization profiles in thin poly(vinylidenefluoride-trifluoroethylene) (PVDF- TrFE) films using two thermal techniques
N2  - In this paper, two non-destructive thermal methods are used in order to determine, with a high degree of accuracy, three-dimensional polarization distributions in thin films (12 mu m) of poly(vinylidenefluoride- trifluoroethylene) (PVDF-TrFE). The techniques are the frequency-domain Focused Laser Intensity Modulation Method (FLIMM) and time-domain Thermal-Pulse Tomography (TPT). Samples were first metalized with grid-shaped electrode and poled. 3D polarization mapping yielded profiles which reproduce the electrode-grid shape. The polarization is not uniform across the sample thickness. Significant polarization values are found only at depths beyond 0.5 mu m from the sample surface. Both methods provide similar results, TPT method being faster, whereas the FLIMM technique has a better lateral resolution.
Y1  - 2009
UR  - http://ieeexplore.ieee.org/servlet/opac?punumber=94
U6  - https://doi.org/10.1109/TDEI.2009.5128505
SN  - 1070-9878
ER  -