アニール処理によるポリマー超音波振動子の性能向上に関するWu（PD）の論文が Ultrasonics に掲載されました。
J. Wu, Y. Mizuno, and K. Nakamura, “Enhancement in mechanical quality factors of poly phenylene sulfide under high-amplitude ultrasonic vibration through thermal annealing,” Ultrasonics, vol. 91, no. 1, pp. 52-61 (2019).
Our previous study shows that poly phenylene sulfide (PPS) provides relatively high mechanical quality factors (Q factors) at ultrasonic frequency compared to other commonly-used functional polymers, and has potential as the vibrating body of a functional ultrasonic transducer. Since PPS has semicrystalline frameworks, its Q factors may be enhanced through thermal annealing. Prior to examining this feasibility, we developed a method for estimating Q factors under high-amplitude longitudinal vibration. Q factor is originally defined as the ratio of the reactive energy to the dissipated energy, both of which are calculated from the vibration velocities on the outer surface of a cylindrical specimen. Using this method, we experimentally investigated how annealing temperatures and times affect Q factors of PPS. The results demonstrate that thermal annealing is an effective way to enhance Q factors of PPS at the heating temperatures of 100°C and 150°C, relatively high compared to the glass transition temperature of PPS (90°C–95°C). The Q factors at several tens of kilohertz are almost doubled after annealing owing to the enhancements in degrees of crystallinity. As the annealing time increases, the Q factors initially become higher, and gradually approach their saturated values at a sufficiently long time. Besides, annealing temperatures affect the change rates in Q factors, but have no observable effect on the saturated Q factors.