TY - JOUR A1 - Bovtun, V. A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Beck, Uwe A1 - Erhard, Anton A1 - Yakymenko, Y. T1 - Air-coupled ultrasonic transducers based on cellular polypropylene ferroelectret films N2 - Analysis of the dielectric and electromechanical properties of the cellular polypropylene ferroelectret films (EMFIT) evidences their high potential for the application in the air-coupled ultrasonic transducers. Simple prototype transducers, based on the EMFIT films, were developed and their high sensitivity was proved in the air-coupled ultrasonic experiment. Amplitude and delay time scanned images of the polyethylene step wedge with holes, obtained in both pulse-echo and transmission modes, demonstrate that non-contact ultrasonic imaging with EMFIT transducers is possible. KW - Air-coupled ultrasonics KW - Non-contact transducers KW - Ferroelectrets KW - Electromechanical properties PY - 2007 SN - 0015-0193 SN - 1563-5112 VL - 353 IS - 1 SP - 186 EP - 192 PB - Taylor & Francis CY - New York, NY AN - OPUS4-14977 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bovtun, Viktor Petrovic A1 - Döring, Joachim A1 - Bartusch, Jürgen A1 - Beck, Uwe A1 - Erhard, Anton A1 - Yakymenko, Y. T1 - Ferroelectret non-contact ultrasonic transducers N2 - Dielectric and electromechanical properties of the cellular polypropylene ferroelectret films (EMFIT), combining strong piezoelectric response with a low density and softness, evidence their high potential for the air-coupled ultrasonic applications. The disadvantage of the low coupling factor is compensated by the extremely low acoustic impedance, which provides excellent matching to air and promises efficient sound transmission through the air–transducer interface. The influence of the electrodes on the electromechanical properties was investigated. Electron beam evaporation technology was adapted to the EMFIT films, and films with both-sided Au and Al electrodes were prepared without reducing or suppressing of the electromechanical properties. Finally, prototype transducers based on the EMFIT films were developed. In spite of the simple construction and absence of matching layers, high sensitivity of the EMFIT transducers was proved in the air-coupled ultrasonic experiment. Amplitude and delay time scanned images of the polyethylene step wedge with holes, obtained in both pulse-echo and transmission modes, demonstrate that non-contact ultrasonic imaging and testing with EMFIT transducers is possible. KW - Piezoelectric film KW - Air borne transducer KW - Non-destructive testing PY - 2007 SN - 0947-8396 VL - 88 IS - 4 SP - 737 EP - 743 PB - Springer CY - Berlin AN - OPUS4-15074 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -