TY  - JOUR
A1  - Wegener, Michael
A1  - Bauer, Siegfried
A1  - Gerhard, Reimund
T1  - Apparent dielectric hysteresis without significant dipolar movement?
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Qiu, Xunlin
A1  - Mellinger, Axel
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Gerhard, Reimund
T1  - Barrier discharges in cellular polypropylene ferroelectrets : how do they influence the electromechanical properties?
Y1  - 2007
ER  - 
TY  - JOUR
A1  - Bergweiler, Steffen
A1  - Bergner, André
A1  - Görne, Thomas
A1  - Wegener, Michael
A1  - Gerhard, Reimund
T1  - Breathing modes and sound radiation of metallic organ pipes
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Wegener, Michael
A1  - Gerhard, Reimund
A1  - Wirges, Werner
A1  - Bergner, André
A1  - Bergweiler, Steffen
T1  - Breathing modes of organ-pipe bodies : experimental detection with ring-shaped piezoelectric-polymer sensors
Y1  - 2003
ER  - 
TY  - JOUR
A1  - Fang, Peng
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Gerhard, Reimund
A1  - Zirkel, Larissa
T1  - Cellular polyethylene-naphthalate ferroelectrets : foaming in supercritical carbon dioxide, structural and electrical preparation, and resulting piezoelectricity
N2  - Polymer foams with electrically charged cellular voids, the so-called ferroelectrets, are soft piezoelectric transducer materials. Several polymers such as polyethylene terephthalate or cyclo-olefin copolymers are under investigation with respect to their suitability as ferroelectrets. Here, the authors report an additional ferroelectret polymer, cellular polyethylene-naphthalate (PEN), which was prepared from commercial uniform polymer films by means of foaming in supercritical carbon dioxide, inflation, biaxial stretching, electrical charging, and metallization. Piezoelectric d(33) coefficients of up to 140 pC/N demonstrate the suitability of such cellular PEN films for transducer applications. Their piezoelectricity is partially stable at elevated temperatures as high as 100 degrees C.
Y1  - 2007
UR  - http://apl.aip.org/
U6  - https://doi.org/10.1063/1.2738365
SN  - 0003-6951
ER  - 
TY  - JOUR
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Richter, Kristin
A1  - Künstler, Wolfgang
A1  - Gerhard, Reimund
T1  - Charge stability and piezoelectric properties of porous fluoro-polymer space-charge electrets in layer systems
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Wegener, Michael
A1  - Wirges, Werner
A1  - Paajanen, Mika
A1  - Gerhard, Reimund
T1  - Charging behaviour and thermal stability of porous and non-porous polytetrafluoroethylene (PTFE) electrets
Y1  - 2007
SN  - 978-1-4244-1482-6
ER  - 
TY  - JOUR
A1  - Paajanen, Mika
A1  - Wegener, Michael
A1  - Gerhard, Reimund
T1  - Charging of cellular space-charge electret films in various gas atmospheres
Y1  - 2001
SN  - 0-7803-7053-8
ER  - 
TY  - JOUR
A1  - Montanari, Gian Carlo
A1  - Fabiani, Davide
A1  - Ciani, Franco
A1  - Motori, Antonio
A1  - Paajanen, Mika
A1  - Gerhard, Reimund
A1  - Wegener, Michael
T1  - Charging properties and time-temperature stability of innovative polymeric cellular ferroelectrets
N2  - After appropriate mechanical and electrical treatments, some cellular polymers become able to retain space charge for a long time, i.e. they acquire electret behavior. The electrical treatment consists of charging under high levels of DC electric field. The mechanical treatment, based on the application of stretching forces to cellular polymer slabs that were before expanded under pressurized gas, affects the cavity size and shape, and therefore also the effectiveness of the charging process itself. An investigation of charging mechanisms, as well as of mechanical treatment, is therefore fundamental for optimizing the ferro- and piezo-electret properties. The aim of this paper is to discuss the effect of the physical dimension of the cavities on the charging behavior of cellular ferroelectrets and to focus on the time-temperature stability for two families of polymeric cellular ferroelectrets based on polypropylene (PP) and on a cyclo-olefin copolymer (COC). Emphasis will be given to the stretching process and in particular to the expansion rate applied during the manufacturing process (which affects the radial dimension and the height of the cavities, respectively). Space-charge and partial-discharge measurements as a function of time and temperature are the main tools to infer the influence of the cavity size on charging and stability characteristics.
Y1  - 2007
UR  - http://ieeexplore.ieee.org/servlet/opac?punumber=94
U6  - https://doi.org/10.1109/TDEI.2007.302892
SN  - 1070-9878
ER  - 
TY  - JOUR
A1  - Elling, B.
A1  - Pinnow, M.
A1  - Danz, Rudi
A1  - Wegener, Michael
A1  - Wirges, werner
A1  - Gerhard, Reimund
T1  - Coating of porous polytetrafluoroethylene films with other polymers for electret applications
Y1  - 2001
SN  - 0-7803-7053-8
ER  -