聚合物/陶瓷复合压电材料的增材制造与应用研究

传统的压电器件制备方法是通过减材制造制造的。该工艺不仅制造成本高，生产周期长，工艺复杂、材料利用率低，而且对几何形状复杂的压电器件主要采用划片、拉削、锯切或蚀刻等切割技术，极大地限制了操作条件。作为一种新兴的尖端制造方法，增材制造技术推动了压电器件的发展，实现了从一步成型的微型器件向大规模器件制造的迈进。它改变了器件的生产工艺，提高了器件的性能。增材制造技术应用于压电材料的制造正在成为器件制造的主流趋势。本文尝试开拓压电材料的增材制造的新工艺，希望得到低成本、高效率、可大规模制造的下一代多功能压电器件。本文主要介绍以下四个方面的工作：

工作一，通过直写式打印制备了一种有银颗粒负载0.55Pb(Ni_1/3Nb_2/3)O₃-0.135PbZrO₃-0.315PbTiO₃（PNN-PZT）陶瓷和聚二甲基硅氧烷弹性体基体制成的柔性0-3结构陶瓷-聚合物复合材料。直写打印的非立体光刻网格复合材料在掺杂陶瓷颗粒后表现出更大的柔韧性，压电电压系数g₃₃高达400×10^-3 m V N^-1，这是比PZT基陶瓷高一个数量级。这项工作表明直写式3D打印的柔性陶瓷-聚合物复合材料有潜力替代脆性压电陶瓷，用于机电能量转换和接触力传感器应用，例如软机器人，人造肌肉和生物信号识别。

工作二，创造性地将介电泳技术和增材制造技术相结合，制备了一种高性能压电聚合物复合材料。对齐的1-3结构3D打印压电复合材料相比没有经过介电泳处理的压电常数和压电电压系数都显着增加。制备得到性能最优的介电泳3D打印无铅压电复合材料的峰值输出功率密度高达242 μW cm ^-2，这比3D打印随机分散纳米颗粒复合材料高9倍。这项工作为开发用于机电设备的高性能柔性压电复合材料开辟了一条途径，可能有助于可穿戴电子设备的普及。

工作三，引入了一种简便且可扩展的方法，通过使用超材料作为模板，制备高性能无铅压电复合材料。首先通过投影微立体光刻3D打印技术打印机构建了三维连续超材料结构，然后通过溶胶-凝胶法制备了无铅压电陶瓷框架。通过合理设计的三维超材料框架制备的超材料压电结构聚合物复合材料。与无规钛酸钡-聚合物复合材料相比，超材料压电结构聚合物复合材料大大提高了机电效率和压电性能，也可作为可穿戴传感器和能量收集器。这种策略可能会为制造具有复杂形状和增强压电响应的高性能增材制造电子产品开辟有前景的途径。

工作四，提出了一种受剪纸/折纸结构启发使用直写式打印机制备压电陶瓷的方法。直写打印过程类似于剪纸过程设计拓扑结构，煅烧过程在生胚上放置耐高温的氧化铝陶瓷得到弯曲陶瓷的过程类似于折纸。烧结后的压电陶瓷极化后压电常数可达到275 pC N^-1，比同类普通片状陶瓷压电常数高45%。其弯曲结构与人体能很好地贴合，也可以检测脉搏信号。这种策略也成功地推广到弯曲多孔氧化锆陶瓷的制备上。这项工作为制备复杂形状的陶瓷提供了一种新的思路。

The piezoelectric device is fabricated by subtractive manufacturing traditionally. This process is not only high manufacturing cost, long production cycle, process complicated and low utilization rate of materials, but it also mainly employs cutting technology such as scribing, broaching, sawing, or etching for piezoelectric devices with complex geometric shapes, which greatly limits operating conditions. As an emerging cutting-edge manufacturing method, additive manufacturing technology has promoted the development of piezoelectric devices, implementing the progress from one-step micro-devices to large-scale device fabrication. It changes the processability of the device and improves the performance of the device. The production of piezoelectric materials combining with additive manufacturing technique is becoming a mainstream trend in device fabrication. This thesis focuses on expanding the development of additive manufacturing of piezoelectric devices, and wishes to obtain next-generation multifunctional piezoelectric devices with low cost, high efficiency, large-scale manufacturing and excellent performance. The thesis mainly includes the following four parts:

Part 1, we report the design of flexible ceramic-polymer composite made of polydimethylsiloxane (PDMS) elastomeric matrix doped with 0.55Pb(Ni_1/3Nb_2/3)O₃-0.135PbZrO₃-0.315PbTiO₃ ceramic heterojunction particles, and the 3D printing method for fabricating complex three-dimensional architectures. We found that the non-stereolithographic direct-write-printed grid composites exhibited greater flexibility after doped with Ag coated ceramic particles, and the piezoelectric voltage coefficient g₃₃ was as high as 400 × 10^-3 m V N^-1, which is one order of magnitude higher than that of PZT based ceramics. This work demonstrates the potential of direct-writing 3D printed flexible ceramic-polymer composites to replace brittle piezoelectric ceramics for electromechanical energy conversion and applications of sensor such as soft robotics, artificial muscles, and bio-recognition.

Part 2, we introduce a facile and scalable approach combining additive manufacturing and dielectrophoresis technology to obtain a new class of high-performance piezoelectric polymer composites. Compared to a 3D-printed composite with randomly dispersed nanoparticles, both the piezoelectric coefficient and the piezoelectric voltage coefficient of the aligned 1-3 structured 3D-printed piezoelectric composites dramatically increases. The peak output power density of the optimized dielectrophoretic 3D printed composite is as high as 242 mW cm^-2, which is 9 times higher than that of a randomly dispersed nanoparticle 3D-printed composite. We believe that this work opens an avenue for developing high-performance fexible piezoelectric composites for electromechanical devices, which could possibly contribute to the proliferation of wearable electronic devices.

Part 3, we introduce a facile and scalable approach to a high-performance lead-free piezoelectric composite by using a metamaterial as a template. We first constructed a three-dimensional continuous metamaterial structure by projection micro-stereolithography 3D printing technology printer, and then prepared a lead-free piezoelectric ceramic framework by sol-gel method. We achieved a rationally designed three-dimensional metamaterial framework for effective stress transfer in the polymer composites to greatly improve the electromechanical efficiency and piezoelectric performance compared with the random BaTiO₃-polymer composite. The as-obtained piezoelectric composite was demonstrated as wearable sensor and harvest energy harvester. We expect that this strategy may potentially open promising avenues for fabrication of high-performance additive manufactured electronics with complex shwapes and enhanced piezoelectric responses.

Part 4, we creatively propose a method to fabricate piezoelectric ceramics using a direct-write printer inspired by kirigami/origami approaches in the first time. The direct writing printing process is similar to the kirigami process to design the topology, and the calcination process places a high temperature resistant alumina ceramic on the green embryo to obtain a curved BaTiO₃ ceramic process similar to origami. The piezoelectric constant of the sintered BaTiO₃ piezoelectric ceramics after polarization can reach 275 pC N^-1, which is 45% higher than that of ordinary BaTiO₃ sheet ceramics. Its curved structure fits well with the human body and can also detect pulse signals. This work provides a new idea for the preparation of complex-shaped ceramics.

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