Study On Fabrication And Properties Of KNBT/Epoxy Resin 1-3 Composites

1-3 piezoelectric composites combine the high piezoelectric properties of piezoelectric ceramic and the flexibility of polymer. Thus 1-3 piezoelectric composites have more merits, such as higher piezoelectric constant, larger electro-mechanical coupling coefficient, lower mechanical quality factor and smaller acoustic impedance. They are suitable for transducers with high sensitivity, broad and narrow pulse, which have been widely used in medical ultrasonic, non-destructive testing and acoustic transducers.For the environmental harmony and applications of 1-3 piezoelectric composites to medical ultrasonic transducer. KNBT piezoelectric fibers were fabricated by viscous polymer processing (VPP) and 1-3 type piezoelectric composites were prepared by arrangement-pouring method. The interrelation of composites among arrangements and properties were studied systematically . And the effects of different composition and volume fraction of piezoelectric fibers on the composites properties were discussed. The concrete work and conclusions as follows.1,KNBT ceramic fibers were fabricated by viscous polymer processing (VPP). The affects of organic content and sintering condition on fiber structures and properties were analyzed. The results show that solid content is 83.3wt%,the green fibers with fine slasticity and strength were prepared.and the best sintering condition was done at 1100℃for 2h. To the KNBT fibers, the hygroscopic coefficient Wa, apparent porosity Pa and bulk density pv were 0.45%, 0.46% and 5.94g/cm³, respectively. The ultimate tensile strength reached 20.52 MPa.2,1-3 piezoelectric composites achieved by arranging-casting technique. With study on curing technique of epoxy resin, The optimized composition of epoxy resin was 100 vs. 85 vs. 5 vs. 0.3 (epoxy resin E-51 vs. MTHPA vs. DOP vs. DMP-30, wt%), The electric field, temperature and time during poling dramatically influenced the properties of 1-3 composites. The optimal poling condition was processed on time of 30 min, temperature of 80℃, and electric field of 3 kV.mm^-1.3,The fiber volume fractionφhad prodigious effects on properties of 1-3 composites. With increasing the ceramic volume fraction, the relative permittivity constant (?) of 1-3 composites rose linear, and remnant polarization gained prominently. The piezoelectric strain constant (?) increased with increasing of fiber volume fractions and the piezoelectric voltage constant (?) decreased.When thefiber volume fractionφreached 85%,the remnant polarization P₁ and piezoelectric strain constant (?) were 29.40μC.cm^-2 and 74pC.N^-1.4,The influences of aspect ratio t/d on properties of 1-3 composites were tremendous. As increasing t/d, the relative permittivity constant (?) and permittivity loss tanδwill reduce. At the same time, the piezoelectric strain constant (?) and piezoelectric voltage constant (?) will increase. And the values of (?) were higher than KNBT ceramic all through.