Defect Engineering in Lead Zirconate Titanate Ferroelectric Ceramic for Enhanced Electromechanical Transducer Efficiency
Defect Engineering in Lead Zirconate Titanate Ferroelectric Ceramic for Enhanced Electromechanical Transducer Efficiency
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用于增强机电换能器效率的锆钛酸铅铁电陶瓷的缺陷工程
DOI：
10.1002/adfm.202005012
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发表时间：
2020-10-01
影响因子：
19
通讯作者：
Wang, Ke
中科院分区：
文献类型：
--
作者：
Li, Zhao;Thong, Hao-Cheng;Wang, Ke
喷油器内的流动和空化现象对燃油雾化过程起着重要作用，尤其是在喷油末期，会引起高温气体的吸入，从而导致孔内结焦。由于喷油器内的油囊被一个厚的钢壁所包围，整个喷油过程发生在几微秒内，因此揭示喷油器内的流动和空化形态是非常困难的。为此，通过优化样品-探测器距离和图像处理方法，发展了同步辐射X射线相位衬度成像技术，增强了图像强度和对比度，实现了瞬态空化形貌的可视化。对三种不同喷射压力下的流动和空化形态进行了记录和比较。结果表明，喷嘴囊内空化气泡和气体摄入过程清晰可见，揭示了囊内两阶段的流动动力学过程。在第一阶段，由于压力突然下降，针尖表面周围的囊内出现空化气泡;在第二阶段，由于囊内真空度增加，环境气体通过孔口被吸入，导致空化气泡迅速破裂。然后，在喷射结束时，被吸入的气体取代了空化气泡，占据了囊的大部分空间。锆钛酸铅（PZT）基压电陶瓷是各种机电应用的重要功能材料，包括传感器、致动器和换能器。高的压电系数和机械品质因数是谐振压电应用的必要条件。然而，由于这些性能往往成反比，同时很难实现高性能，因此，广泛的应用受到了很大的限制。在本研究中，通过创新的缺陷工程，其中包括缺陷偶极子，畴壁密度和晶界之间的多尺度协调，在PZT基陶瓷中实现了非常平衡的性能。这些材料上级许多最先进的商业同行，可以满足先进机电应用的高端要求，如能量收集，结构健康监测，机器人传感器和致动器。
The flow and cavitation phenomena inside the nozzle sac play an important role in the fuel atomization process, especially at the end of the injection, which may cause high-temperature gas ingestion consequently leading to coke formation inside the orifice. It is of great difficulty to reveal the flow and cavitation morphology inside fuel nozzles during the fuel injection process since the nozzle sac is enclosed by a thick steel wall and the whole process takes place in a few microseconds. Therefore, a dedicated synchrotron radiation X-ray phase contrast imaging technology was developed by optimizing sample-to-detector distances and image processing methods, and the image intensity and contrast were enhanced to visualize the transient cavitation morphology. The flow and cavitation morphology at three different injection pressures were recorded and compared. The results show that the cavitation bubbles and gas ingestion process inside the nozzle sac can be clearly observed revealing a two-stage flow dynamics process occurring inside the sac. At the first stage, the cavitation bubbles appear in the sac around the needle tip surface due to the sudden pressure decrease; at the second stage, the ambient gas was ingested through the orifice due to the increase of the vacuum degree in the sac, leading to a rapid burst of the cavitation bubbles. The ingested gas replacing the cavitation bubbles then occupies the most space of the sac at the end of the injection.Lead zirconate titanate (PZT)-based piezoelectric ceramics are important functional materials for various electromechanical applications, including sensors, actuators, and transducers. High piezoelectric coefficient and mechanical quality factor are essential for the resonant piezoelectric application. However, since these properties are often inversely proportional, simultaneously high performances are hard to achieve, consequently, a wide range of applications are strongly restricted. In the present study, exceptionally well-balanced performances are achieved in PZT-based ceramics via innovative defect engineering, which involves multi-scale coordination among defect dipole, domain-wall density, and grain boundary. These materials are superior to many state-of-the-art commercial counterparts, which can potentially satisfy high-end requirements for advanced electromechanical applications, such as energy harvesting, structural health monitoring, robotic sensors, and actuator.