DocumentCode :
1303309
Title :
Ferroelectric nylon materials and their feasibility for ultrasound transducers
Author :
Brown, Lewis F. ; Mason, Joel L. ; Klinkenborg, Monte L. ; Scheinbeim, Jerry I. ; Newman, Brian A.
Author_Institution :
Dept. of Electr. Eng., South Dakota State Univ., Brookings, SD, USA
Volume :
44
Issue :
5
fYear :
1997
Firstpage :
1049
Lastpage :
1059
Abstract :
Measurements of the high frequency electrical and acoustic properties of oriented ferroelectric nylon-7 and nylon-11 are reported for the frequency range of 10 to 50 MHz and temperature range of 20 to 160/spl deg/C. The dielectric properties of nylon films were measured over a broadband frequency range including the fundamental halfwave resonance frequency for each sample, and a curve-fitting resonance technique was used to determine the properties of interest for ultrasound transducer design. Despite the high remanent polarization measured in the nylon films (1.25 mC/cm/sup 2/), the measured electromechanical coupling constant (k/sub t/=0.11), and mechanical quality factor (Q/sub m/=8) were lower than typically seen for PVDF and P(VDF-TrFE) copolymer. Poor thickness uniformity of the nylon film samples is suspected of dampening the features of the dielectric spectra near resonance, resulting in lower measured values for k/sub t/ and Q/sub m/. Comparisons of both simulated and actual measured pulse-echo performance showed the nylon materials to be competitive with PVDF for ultrasonic transducer performance. Actual pulse-echo tests with nylon-7 yielded a -6 dB fractional bandwidth of 144%. Since the ferroelectric nylons are known to be hydrophilic, tests were conducted to quantitatively determine the effects of water absorption on the ultrasonic performance of nylon-7 transducers. The results showed the water exposure slightly reduces the pulse-echo amplitude response and resonant frequency of a nylon-7 transducer. The water absorption effects were shown to be fully reversible upon drying the nylon film.
Keywords :
acoustic transducers; ferroelectric materials; polymers; ultrasonic transducers; 10 to 50 MHz; 20 to 160 C; acoustic properties; curve fitting; dielectric properties; dielectric spectrum; drying; electromechanical coupling constant; ferroelectric nylon; halfwave resonance frequency; hydrophilic material; mechanical quality factor; nylon-11; nylon-7; polarization; pulse echo; ultrasound transducer; water absorption; Acoustic measurements; Dielectric materials; Dielectric measurements; Ferroelectric materials; Frequency; Q measurement; Resonance; Ultrasonic imaging; Ultrasonic transducers; Ultrasonic variables measurement;
fLanguage :
English
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
Publisher :
ieee
ISSN :
0885-3010
Type :
jour
DOI :
10.1109/58.655630
Filename :
655630
Link To Document :
بازگشت